Ultimate Biology Class To Study Quiz

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Questions: 106 | Attempts: 201

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Ultimate Biology Quizzes & Trivia

All my quizzes and test questions combined throughout the year for my biology class to study for my final.


Questions and Answers
  • 1. 

    If an atom has a charge of +1, which of the following must be true?

    • A.

      It has the same number of protons as electrons.

    • B.

      It has two more protons than neutrons.

    • C.

      It has one more electron than it does protons.

    • D.

      It has one more proton than it does electrons.

    Correct Answer
    D. It has one more proton than it does electrons.
    Explanation
    If an atom has a charge of +1, it means that it has lost one electron. Since electrons have a negative charge, losing one electron would result in a net positive charge for the atom. Therefore, the atom must have one more proton than it does electrons in order to have a charge of +1.

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  • 2. 

    When a complex molecule, such as a polypeptide, folds up in solution in water, regions of the moleculewith _________ bonds will be near the surface (associated with water molecules) because theseregions are ____________.

    • A.

      Non-polar / hydrophilic

    • B.

      Non-polar / hydrophobic

    • C.

      Polar / hydrophobic

    • D.

      Parched / thirsty

    • E.

      Polar / hydrophilic

    Correct Answer
    E. Polar / hydrophilic
    Explanation
    When a complex molecule, such as a polypeptide, folds up in solution in water, regions of the molecule with polar bonds will be near the surface (associated with water molecules) because these regions are hydrophilic. Polar bonds have an uneven distribution of charge, with one end being slightly positive and the other end being slightly negative. This polarity allows the polar regions of the molecule to interact with the polar water molecules, forming hydrogen bonds. Since water is a polar molecule, it is attracted to other polar molecules, making the polar regions of the molecule more likely to be near the water surface.

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  • 3. 

    Which of the following properties of water is NOT affected by the strong cohesion between H2O molecules?

    • A.

      Heat Of vaporization

    • B.

      Specfic heat

    • C.

      Surface tension

    • D.

      Ph

    • E.

      Adhesion

    Correct Answer
    D. Ph
    Explanation
    The pH of water is not affected by the strong cohesion between H2O molecules. The cohesion between water molecules is due to hydrogen bonding, which does not alter the concentration of H+ or OH- ions in the solution. The pH of a solution is determined by the concentration of these ions, and since the cohesion between water molecules does not change this concentration, the pH remains unaffected.

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  • 4. 

    Carbon has proven to be an extremely useful backbone element for complex biological molecules dueto strong electronegativity and valence number of 7, which allows carbon atoms to attract electrons fromalmost any other element.

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    The explanation for the given answer "false" is that while carbon is indeed an extremely useful backbone element for complex biological molecules, it is not due to its strong electronegativity and valence number of 7. Carbon's usefulness lies in its ability to form stable covalent bonds with other carbon atoms and a wide variety of other elements, allowing for the formation of complex and diverse organic compounds.

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  • 5. 

    A chemical reaction in which the product has more potential chemical energy than the reactants iscalled endergonic.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    An endergonic reaction is a chemical reaction where the product has more potential chemical energy than the reactants. This means that energy is absorbed or required for the reaction to occur. In an endergonic reaction, the products have higher energy levels than the reactants, indicating an increase in potential chemical energy. Therefore, the statement is true.

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  • 6. 

    One atom named Stan shares electrons with Betty. Between them they share 4 electrons. What kind ofbond do they share?

    • A.

      Single Bond

    • B.

      Valance Bond

    • C.

      Double Bond

    • D.

      Bond Of Love

    Correct Answer
    C. Double Bond
    Explanation
    Stan and Betty share 4 electrons, which indicates a strong bond between them. A double bond is formed when two atoms share four electrons, with two pairs of electrons being shared. This type of bond is commonly found between carbon atoms and is characterized by a strong attraction and a shorter bond length compared to a single bond. Therefore, the correct answer is a Double Bond.

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  • 7. 

    When Sodium loses an electron to chlorine it becomes?

    • A.

      A cation

    • B.

      As mad as @#$#@%^&

    • C.

      An Anion

    • D.

      Negatively charged

    Correct Answer
    A. A cation
    Explanation
    When sodium loses an electron to chlorine, it creates a positively charged ion called a cation. This is because sodium has one valence electron in its outermost shell, and by losing that electron, it achieves a stable electron configuration similar to that of a noble gas. The loss of an electron results in an overall positive charge on the sodium ion.

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  • 8. 

    The two most common elements in the human body by number (not by mass) are _________and_________ .

    Correct Answer
    Hydrogen
    Oxygen
    Explanation
    The two most common elements in the human body by number are hydrogen and oxygen. Hydrogen is the most abundant element in the universe and is found in large quantities in water and organic compounds. Oxygen is the second most abundant element in the human body and is essential for respiration and energy production. These two elements are crucial for the functioning of various biological processes in the human body.

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  • 9. 

    A solution contains 1 X 10-12 moles of H+ per liter. What is its pH?____________ Is the solution considered acidic or basic?_______________

    Correct Answer
    12
    Basic
    Explanation
    The pH of a solution is a measure of its acidity or basicity. pH is calculated using the formula -log[H+], where [H+] represents the concentration of hydrogen ions in moles per liter. In this case, the solution contains 1 X 10-12 moles of H+ per liter. Taking the negative logarithm of this concentration gives a pH value of 12. Since the pH is greater than 7, the solution is considered basic.

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  • 10. 

    Molecules of this type are bonded together in_______________ reactions to form a_________________.

    • A.

      Exergonic/ hydrogen bond

    • B.

      Ionic/ nucleotide

    • C.

      Hydrolysis/ prion

    • D.

      Condensation/ polypeptide

    • E.

      Aminocarboxylation / protein

    Correct Answer
    D. Condensation/ polypeptide
    Explanation
    Molecules of this type are bonded together in condensation reactions to form a polypeptide. In a condensation reaction, two molecules combine to form a larger molecule, with the elimination of a small molecule such as water. In the context of proteins, amino acids are joined together through condensation reactions to form polypeptides, which are chains of amino acids. This process is essential for protein synthesis and the formation of the primary structure of proteins.

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  • 11. 

    Amino acids with ___________ groups that contain __________ are likely to be hydrophilic.

    • A.

      Functional / hydrogen

    • B.

      R/ Oxygen

    • C.

      Hydroxyl/ oxygen

    • D.

      Phosphate/ oxygen

    • E.

      Ketone/ nitrogen

    Correct Answer
    B. R/ Oxygen
    Explanation
    Amino acids with oxygen groups that contain oxygen are likely to be hydrophilic. Oxygen groups, such as hydroxyl and carbonyl groups, are polar and can form hydrogen bonds with water molecules, making the amino acid hydrophilic.

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  • 12. 

    Which one of the following is NOT a component of each monomer used to make proteins?a carboxyl group, COOHa side chain, Ra phosphorous atom, Pan amino functional group, NH2

    • A.

      A carboxyl group, COOH

    • B.

      A side chain, R

    • C.

      A phosphorous atom, P

    • D.

      An amino functional group, NH2

    Correct Answer
    C. A phosphorous atom, P
    Explanation
    Each monomer used to make proteins consists of an amino functional group (NH2), a carboxyl group (COOH), and a side chain (R). These components are necessary for the formation of peptide bonds, which link the monomers together to form a protein chain. However, a phosphorous atom (P) is not typically found in the structure of amino acids, which are the building blocks of proteins. Therefore, a phosphorous atom is not a component of each monomer used to make proteins.

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  • 13. 

    Why are polymerization reactions endergonic?

    • A.

      They release heat. making the reatant monomers move faster

    • B.

      They reduce entropy

    • C.

      Because the condensation and hydrolysis reactions are equally spontaneous.

    • D.

      Because polymers are energetically more stable and have lower potential energy than monomers do.

    Correct Answer
    B. They reduce entropy
    Explanation
    Polymerization reactions involve the formation of larger molecules (polymers) from smaller molecules (monomers). This process leads to a decrease in the number of possible arrangements of the molecules, resulting in a reduction in entropy. Since entropy is a measure of the disorder or randomness in a system, a decrease in entropy requires an input of energy. Therefore, polymerization reactions are endergonic, meaning they require energy to proceed.

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  • 14. 

    At the pH found in cells (about 7.0), what happens to the amino group on an amino acid?

    • A.

      It is reduced, and tends to act as an electron donor in redox reactions.

    • B.

      It acts as an acid and loses a proton, giving it a negative charge.

    • C.

      It acts as a base and gains a proton, giving it a positive charge.

    • D.

      It remains neutral, like water, and does not have a charge.

    Correct Answer
    C. It acts as a base and gains a proton, giving it a positive charge.
    Explanation
    At a pH of 7.0, the amino group on an amino acid acts as a base and gains a proton, giving it a positive charge. This is because at this pH, the environment is slightly acidic, and the amino group can accept a proton (H+) to become positively charged. This positive charge allows the amino acid to participate in various chemical reactions and interactions within the cell.

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  • 15. 

    Suppose you discovered a new amino acid. Its R-group contains only hydrogen and carbon atoms.Predict the behavior of this amino acid.

    • A.

      Relative to the amino acids found in organisms, its interactions with water will be intermediate.

    • B.

      It is hydrophilic.

    • C.

      It is hydrophobic.

    • D.

      Relative to the amino acids found in organisms, its interactions with water will be very high.

    Correct Answer
    C. It is hydrophobic.
    Explanation
    The given information states that the R-group of the new amino acid contains only hydrogen and carbon atoms. Hydrophobic amino acids typically have nonpolar R-groups, such as hydrocarbon chains. Since hydrogen and carbon atoms are both nonpolar, it can be inferred that the new amino acid is hydrophobic. Hydrophobic amino acids tend to repel water and prefer to interact with nonpolar molecules or other hydrophobic regions. Therefore, the behavior of this amino acid would be consistent with being hydrophobic.

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  • 16. 

    An isomer of a particular molecule is :

    • A.

      A molecule that has the same formula, but a different structure.

    • B.

      Another copy of the same molecule.

    • C.

      A molecule that is the same except it has an additional side group.

    • D.

      A molecule that has the same structure as the target molecule, but a different formula.

    Correct Answer
    A. A molecule that has the same formula, but a different structure.
    Explanation
    An isomer of a particular molecule refers to a molecule that has the same chemical formula as the target molecule but differs in its structural arrangement. Isomers have the same number and types of atoms but are arranged differently, resulting in distinct chemical and physical properties. Therefore, the correct answer is "a molecule that has the same formula, but a different structure."

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  • 17. 

    To act as an effective coolant in a car's radiator, a substance has to be a liquid at the temperaturesfound in your car's engine and have the capacity to absorb a great deal of heat. You have a referencebook with tables listing the physical properties of many liquids. In choosing a coolant for your car,which table would you check first?

    • A.

      Heat of vaporization

    • B.

      Specific heat

    • C.

      Ph

    • D.

      Density at room temperature

    Correct Answer
    B. Specific heat
    Explanation
    To act as an effective coolant in a car's radiator, a substance needs to have a high specific heat. Specific heat refers to the amount of heat energy required to raise the temperature of a substance by a certain amount. A coolant with a high specific heat can absorb a greater amount of heat from the car's engine, helping to regulate its temperature and prevent overheating. Therefore, checking the table listing the specific heat of different liquids would be the first step in choosing a coolant for a car.

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  • 18. 

    You have isolated a previously unstudied protein, identified its complete structure in detail, anddetermined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites.One of these is large, apparently the bonding site for the large substrate; the other is small, possibly abinding site for a regulatory molecule. What do these findings tell you about the mechanism of thisprotein?

    • A.

      It is probably a structural protein found in cartilage or skeletal tissue.

    • B.

      It is probably a structural protein that is involved in cell-to-cell adhesion.

    • C.

      It is probably an enzyme that works through allosteric regulation.

    • D.

      It is probably a cell membrane transport protein–like an ion channel

    • E.

      It is probably an enzyme that works through competitive inhibition.

    Correct Answer
    C. It is probably an enzyme that works through allosteric regulation.
    Explanation
    The presence of two binding sites in the protein suggests that it is involved in some kind of regulation. The large binding site is likely for the substrate, indicating that the protein catalyzes the breakdown of a large substrate. The presence of a small binding site suggests that there is a regulatory molecule that can bind to it and modulate the activity of the protein. This is characteristic of allosteric regulation, where the binding of a regulatory molecule to a different site on the protein can either enhance or inhibit its catalytic activity. Therefore, the protein is likely an enzyme that works through allosteric regulation.

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  • 19. 

    Which of the following means of transport would most likely be used for moving a medium-sized molecule (like amonosaccharide or an amino acid) from a low concentration on the outside of a cell to a high concentration onthe inside of a cell?

    • A.

      Facilitated diffusion through a transporter protein

    • B.

      Facilitated diffusion through an ion channel protein

    • C.

      Passive transport

    • D.

      Active transport through a "pump" protein

    Correct Answer
    D. Active transport through a "pump" protein
    Explanation
    Active transport through a "pump" protein would be the most likely means of transport for moving a medium-sized molecule from a low concentration on the outside of a cell to a high concentration on the inside of a cell. This is because active transport requires the use of energy to move molecules against their concentration gradient, from an area of low concentration to an area of high concentration. "Pump" proteins are specifically designed to transport molecules against their concentration gradient, making them suitable for this task. Facilitated diffusion through a transporter protein or an ion channel protein would not be able to move molecules against their concentration gradient, and passive transport does not require energy and would not be able to move molecules from a low concentration to a high concentration.

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  • 20. 

    GLUT-1 is an example of what?

    • A.

      A recognition protein that identifies cells as belonging to the body

    • B.

      A transport protein that facilitates diffusion of a large molecule across cell membranes

    • C.

      A protein that is toxic to cells by opening channels in membranes

    • D.

      A membrane-bound pump that moves large molecules against a gradient by using ATP

    Correct Answer
    B. A transport protein that facilitates diffusion of a large molecule across cell membranes
    Explanation
    GLUT-1 is an example of a transport protein that facilitates the diffusion of a large molecule across cell membranes. This means that GLUT-1 helps to transport large molecules across the cell membrane by facilitating their diffusion.

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  • 21. 

    The small intestine is the site of digestion and absorption of nutrients. A single layer of epithelial cells lines thesmall intestine. In the duodenum (the first section of the small intestine), these epithelial cells secrete largequantities of digestive enzymes. Which of the following features would be typical of these epithelial cells?

    • A.

      They have more smooth endoplasmic reticulum than rough endoplasmic reticulum.

    • B.

      They have larger nuclei than cells that secrete large quantities of lipids

    • C.

      They contain large quantities of rough endoplasmic reticulum.

    • D.

      They contain large numbers of lysosomes.

    Correct Answer
    C. They contain large quantities of rough endoplasmic reticulum.
    Explanation
    The correct answer is that these epithelial cells contain large quantities of rough endoplasmic reticulum. This is because rough endoplasmic reticulum is responsible for the synthesis and secretion of proteins, including digestive enzymes. Since the duodenum is the site of digestion, it makes sense that the epithelial cells in this region would have a high concentration of rough endoplasmic reticulum to support the production and secretion of digestive enzymes.

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  • 22. 

    What is the site of synthesis of proteins for export (secretion from the cell)?

    • A.

      Free ribosomes

    • B.

      Ribosomes that attach to the outer mitochondrial membrane

    • C.

      Ribosomes that attach to the endoplasmic reticulum

    • D.

      Ribosomes that attach to the Golgi complex

    Correct Answer
    C. Ribosomes that attach to the endoplasmic reticulum
    Explanation
    Ribosomes that attach to the endoplasmic reticulum are responsible for synthesizing proteins that are intended for export or secretion from the cell. The endoplasmic reticulum is a network of membranes connected to the nuclear envelope, and it plays a crucial role in protein synthesis and processing. Ribosomes attached to the endoplasmic reticulum, also known as rough endoplasmic reticulum, produce proteins that are either inserted into the membrane or packaged into vesicles for transportation to other parts of the cell or outside of the cell. Therefore, these ribosomes are the site of synthesis for proteins that are meant to be secreted.

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  • 23. 

    Which of the following is not a characteristic that chloroplasts and mitochondria share?

    • A.

      They both have their own DNA.

    • B.

      They are capable of reproducing themselves.

    • C.

      They both have multiple membranes.

    • D.

      They are both part of the endomembrane system.

    Correct Answer
    D. They are both part of the endomembrane system.
    Explanation
    Chloroplasts and mitochondria both have their own DNA, they are capable of reproducing themselves, and they both have multiple membranes. However, they are not part of the endomembrane system. The endomembrane system includes organelles such as the endoplasmic reticulum, Golgi apparatus, and lysosomes, which are involved in the synthesis, modification, and transport of proteins and lipids within the cell. Chloroplasts and mitochondria are not involved in these processes, as their main functions are related to energy production (mitochondria) and photosynthesis (chloroplasts).

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  • 24. 

    How is the nuclear membrane related to the endoplasmic reticulum?

    • A.

      Ribosomes that exit the nucleus through the nuclear pore complex attach to ribosome receptor locations on the endoplasmic reticulum, thus providing a means of communication between the two structures.

    • B.

      The inner and outer bilayers of the nuclear envelope are separated by a space that is continuous with the space inside the endoplasmic reticulum, thus providing direct contact between the two structures

    • C.

      The nuclear lamina anchors the endoplasmic reticulum, providing structural support and communication through direct contact

    • D.

      The nucleolus is present in the nucleus, but communicates directly with the endoplasmic reticulum.

    Correct Answer
    B. The inner and outer bilayers of the nuclear envelope are separated by a space that is continuous with the space inside the endoplasmic reticulum, thus providing direct contact between the two structures
    Explanation
    The inner and outer bilayers of the nuclear envelope are continuous with the space inside the endoplasmic reticulum, allowing for direct contact between the two structures. This direct contact facilitates communication and exchange of materials between the nucleus and the endoplasmic reticulum.

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  • 25. 

    What is a purpose of the cell wall for both prokaryotes and plant cells?

    • A.

      To provide a means of cell-cell interaction

    • B.

      To protect the cell from the effects of a hypotonic environment

    • C.

      To regulate the passage of solutes into and out of the cell

    • D.

      To enable the cell to obtain nutrients from its environment

    Correct Answer
    B. To protect the cell from the effects of a hypotonic environment
    Explanation
    The cell wall serves as a protective barrier for both prokaryotes and plant cells, helping to shield the cell from the potentially damaging effects of a hypotonic environment. In a hypotonic environment, there is a higher concentration of solutes inside the cell compared to the surrounding environment, causing water to enter the cell and potentially leading to cell lysis or bursting. The cell wall provides structural support and prevents excessive water uptake, maintaining the cell's shape and integrity.

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  • 26. 

    What can you infer about high-molecular-weight proteins that cannot be transported into the nucleus?

    • A.

      They are defective proteins.

    • B.

      They are foreign proteins.

    • C.

      They lack nuclear localization signals (NLS).

    • D.

      They have been tagged for destruction.

    Correct Answer
    C. They lack nuclear localization signals (NLS).
    Explanation
    High-molecular-weight proteins that cannot be transported into the nucleus are inferred to lack nuclear localization signals (NLS). Nuclear localization signals are specific sequences of amino acids that act as a "zip code" for proteins, allowing them to be recognized and transported into the nucleus. Therefore, the absence of NLS in these proteins prevents their transportation into the nucleus, indicating that they lack the necessary signal for nuclear localization.

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  • 27. 

    What is the most important factor in explaining why diffusion occurs spontaneously?

    • A.

      The process is endothermic

    • B.

      It leads to an increase in entropy.

    • C.

      It leads to a decrease in entropy.

    • D.

      The process is exothermic.

    Correct Answer
    B. It leads to an increase in entropy.
    Explanation
    Diffusion is the spontaneous movement of particles from an area of high concentration to an area of low concentration. The most important factor in explaining why diffusion occurs spontaneously is that it leads to an increase in entropy. Entropy is a measure of the disorder or randomness in a system, and diffusion increases the randomness of the particle distribution. As particles move from an area of high concentration to an area of low concentration, the system becomes more disordered, which is favored by nature.

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  • 28. 

    Mitochondrial DNA codes for about 13 proteins (depending on the species of organism). These 13 proteinsaccount for a small proportion of the proteins present in mitochondria. The remaining proteins are coded for bynuclear DNA. What is the most likely explanation for how these proteins find their way to the mitochondria?

    • A.

      Signal sequences

    • B.

      MRNAs that are manufactured in the nucleus, but translated by mitochondrial ribosomes

    • C.

      Random transport vesicles

    • D.

      Attachment of ribosomes to outer mitochondrial pores and direct deposition into the inner mitochondrial compartment

    Correct Answer
    A. Signal sequences
    Explanation
    The most likely explanation for how these proteins find their way to the mitochondria is through signal sequences. Signal sequences are specific amino acid sequences that act as "tags" on proteins, guiding them to their correct cellular location. In the case of mitochondrial proteins, signal sequences target them to the mitochondria, where they are imported and incorporated into the organelle. This process ensures that the proteins are correctly delivered to the mitochondria and can perform their functions within the organelle.

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  • 29. 

    Under what circumstances does membrane transport always require energy?

    • A.

      Whenever molecules are moved that are too large to pass through the phospholipid bilayer membrane

    • B.

      Whenever a solute is charged, such as an ion, and is moved through a phospholipid bilayer membrane

    • C.

      Whenever a molecule is polar and is moved through a phospholipid bilayer membrane

    • D.

      Whenever a solute needs to be moved from low concentration to high concentration through a phospholipid bilayer membrane

    Correct Answer
    D. Whenever a solute needs to be moved from low concentration to high concentration through a phospholipid bilayer membrane
    Explanation
    Membrane transport always requires energy when a solute needs to be moved from a low concentration to a high concentration through a phospholipid bilayer membrane. This process is called active transport, and it requires the use of energy in the form of ATP to move molecules against their concentration gradient. Active transport is necessary when the concentration of a particular solute needs to be increased inside the cell, and this process cannot occur spontaneously without the input of energy.

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  • 30. 

    Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among theosteocytes. The collagen and calcium salts are ________.

    • A.

      Components of the plasma membrane of osteocytes.

    • B.

      Deposited by the circulatory system and are not associated with the osteocytes.

    • C.

      Extensions of the endoplasmic reticulum.

    • D.

      Part of the extracellular matrix

    Correct Answer
    D. Part of the extracellular matrix
    Explanation
    Collagen fibers and calcium salts are part of the extracellular matrix. The extracellular matrix is a complex network of proteins and other substances that surround cells. In the case of osteocytes, collagen fibers and calcium salts are found in abundance in the extracellular matrix surrounding the bone cells. These components provide structural support and contribute to the strength and rigidity of the bone tissue. They are not part of the plasma membrane of osteocytes, nor are they deposited by the circulatory system or extensions of the endoplasmic reticulum.

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  • 31. 

    Integrins are integral membrane proteins. They are often attached to ________.

    • A.

      Cytoskeletal proteins and molecules of the extracellular matrix.

    • B.

      Pathogens.

    • C.

      Membranes of intracellular organelles.

    • D.

      Glycogen molecules and other cellular inclusions.

    Correct Answer
    A. Cytoskeletal proteins and molecules of the extracellular matrix.
    Explanation
    Integrins are known to be attached to cytoskeletal proteins and molecules of the extracellular matrix. This attachment is important for cell adhesion, migration, and signaling. Integrins act as bridges between the intracellular cytoskeleton and the extracellular matrix, allowing cells to interact with their surrounding environment and maintain structural integrity. Integrins also play a crucial role in various cellular processes such as cell proliferation, differentiation, and tissue development.

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  • 32. 

    Put the following events in the process of signal-transduction for epinephrine action in order:1. A conformational change in the signal-receptor complex activates an enzyme.2. Protein kinases are activated.3. A signal molecule binds to a receptor.4. Target proteins are phosphorylated.5. Second messenger molecules are released.

    • A.

      3,1,2,5,4

    • B.

      3,1,5,2,4

    • C.

      1,3,4,2,5

    • D.

      1,2,3,4,5

    Correct Answer
    B. 3,1,5,2,4
    Explanation
    The process of signal-transduction for epinephrine action begins with the binding of a signal molecule to a receptor (event 3). This binding causes a conformational change in the signal-receptor complex, which in turn activates an enzyme (event 1). The activated enzyme then triggers the release of second messenger molecules (event 5). These second messengers then activate protein kinases (event 2). Finally, the protein kinases phosphorylate target proteins (event 4). Therefore, the correct order of events is 3,1,5,2,4.

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  • 33. 

    A kinase is an enzyme that ________.

    • A.

      Functions as a second messenger molecule.

    • B.

      Produces second messenger molecules.

    • C.

      Adds a phosphate group to target molecules.

    • D.

      Serves as a receptor for various signal molecules.

    Correct Answer
    C. Adds a phosphate group to target molecules.
    Explanation
    A kinase is an enzyme that adds a phosphate group to target molecules. This process, known as phosphorylation, is crucial for regulating various cellular functions. By adding a phosphate group to specific amino acids in proteins, kinases can modulate protein activity, localization, and interactions. This phosphorylation event can act as a signal to activate or deactivate proteins, allowing for precise control of cellular processes such as cell growth, metabolism, and signal transduction. Therefore, the correct answer is that a kinase adds a phosphate group to target molecules.

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  • 34. 

    G-protein receptors and tyrosine kinase receptors both initiate the signal transduction response bybinding signal molecules.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Both G-protein receptors and tyrosine kinase receptors are involved in signal transduction, which is the process by which signals from outside the cell are transmitted to the inside of the cell to initiate a response. These receptors bind to specific signal molecules, such as hormones or growth factors, and trigger a cascade of intracellular events that ultimately lead to a cellular response. Therefore, the statement that both G-protein receptors and tyrosine kinase receptors initiate the signal transduction response by binding signal molecules is true.

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  • 35. 

    Nitric oxide (NO), a substance with small molecular weight, is rapidly degraded within an organismbut can function as a hormone. How does this substance enter the cell?

    • A.

      NO is soluble in the membrane, so it can diffuse into the cell.

    • B.

      It doesn't enter the cell, but attaches to a G-protein receptor and initiates a signal transduction pathway.

    • C.

      It directly affects gene expression.

    • D.

      It attaches to a receptor on the surface. The receptor-signal complex results in a conformational change that internalizes NO.

    Correct Answer
    A. NO is soluble in the membrane, so it can diffuse into the cell.
    Explanation
    NO is a small molecule that is able to dissolve in the cell membrane, allowing it to passively diffuse into the cell. This means that it does not require any specific receptors or signal transduction pathways to enter the cell. Once inside, NO can exert its effects as a hormone.

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  • 36. 

    Spherocytosis is a defect associated with a defective cytoskeletal protein in red blood cells. What do you suspectis one consequence of defective cytoskeletal proteins in red blood cells?

    • A.

      Adhering of blood cells to blood vessel walls, causing the formation of plaque

    • B.

      Abnormal cell shape

    • C.

      A lack of cellular proteins available to transport oxygen

    • D.

      Insufficient energy supply in the cell

    Correct Answer
    B. Abnormal cell shape
    Explanation
    Defective cytoskeletal proteins in red blood cells can lead to abnormal cell shape. The cytoskeleton provides structural support and maintains the shape of cells. In the case of spherocytosis, the defective cytoskeletal protein causes the red blood cells to become spherical instead of their normal biconcave shape. This abnormal shape can affect the ability of the red blood cells to flow smoothly through blood vessels and perform their functions effectively.

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  • 37. 

    Multiple Choice Average Score 0.63 points (Extra credit)The glucocorticoid receptor is a protein that is found only in the cytoplasm until the hormone glucocorticoid entersthe cell and binds to this receptor. The receptor then translocates to the nucleus, where it regulates thetranscription of certain genes. If a specific sequence of the receptor is deleted from the protein, the receptor stillbinds glucocorticoid but does not enter the nucleus. Consider the following additional hypothetical experiment. Ifthe mutant receptor is fused with a fragment of protein that is normally found in the nucleus, the receptor entersthe nucleus regardless of whether glucocorticoid is bound. Which conclusion can be drawn from theseobservations?

    • A.

      The binding of glucocorticoid to the receptor must expose a nuclear localization signal.

    • B.

      Glucocorticoid is the nuclear localization signal for the receptor.

    • C.

      The glucocorticoid receptor does not have a nuclear localization sequence.

    • D.

      The glucocorticoid receptor enters the nucleus by a mechanism different from other proteins found in the nucleus.

    Correct Answer
    A. The binding of glucocorticoid to the receptor must expose a nuclear localization signal.
    Explanation
    The correct answer suggests that the binding of glucocorticoid to the receptor exposes a nuclear localization signal. This means that when glucocorticoid binds to the receptor, it causes a change in the receptor structure that allows it to enter the nucleus. This conclusion is supported by the observation that even when the specific sequence of the receptor is deleted, the receptor still binds glucocorticoid but does not enter the nucleus. Therefore, the binding of glucocorticoid must be responsible for exposing the nuclear localization signal and allowing the receptor to translocate to the nucleus.

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  • 38. 

    Hormones are chemical substances produced in one organ that are released into the bloodstream and affect thefunction of a target organ. For the target organ to respond to a particular hormone, it must ________.

    • A.

      Have the same genetic makeup.

    • B.

      Be from the same cell type as the organ that produced the hormone.

    • C.

      Have receptors that recognize and bind the hormone molecule.

    • D.

      Be experiencing a disruption in homeostasis.

    Correct Answer
    C. Have receptors that recognize and bind the hormone molecule.
    Explanation
    The target organ must have receptors that recognize and bind the hormone molecule in order to respond to a particular hormone. Receptors are proteins located on the surface or inside the target cells that are specific to certain hormones. When a hormone binds to its receptor, it triggers a series of biochemical reactions within the cell, leading to a specific response. Without the appropriate receptors, the target organ would not be able to recognize and respond to the hormone.

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  • 39. 

    Blood sugar is regulated by two pancreatic hormones, namely insulin and glucagon. When blood sugar rises,insulin is released; it binds to receptors and, through signal transduction, results in an increase in glucoseuptake by cells, effectively lowering blood glucose. When blood sugar decreases, glucagon is released, binds tocell receptors, and causes glucose to be released into circulation. Diabetes mellitus is a disorder that results from excessively high levels of blood glucose. Type II diabetics have normal to elevated levels of insulin. What,then, might be causing the elevated blood glucose levels?

    • A.

      Inability to regulate gene expression

    • B.

      Inadequate insulin production

    • C.

      Defective receptors

    • D.

      Defective second messenger

    Correct Answer
    C. Defective receptors
    Explanation
    The elevated blood glucose levels in Type II diabetics may be caused by defective receptors. Even though these individuals have normal to elevated levels of insulin, their receptors are not functioning properly, leading to a decreased ability of insulin to bind to the receptors and stimulate glucose uptake by cells. As a result, blood glucose levels remain high despite the presence of insulin.

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  • 40. 

    What characteristic of ATP is responsible for its high energy level compared to AMP?

    • A.

      The phosphorus atoms in the phosphate groups

    • B.

      The C—H bonds of the ribose sugar

    • C.

      The closely spaced negative charges associated with the phosphate groups

    • D.

      The nitrogen atoms in adenine

    Correct Answer
    C. The closely spaced negative charges associated with the phosphate groups
    Explanation
    The closely spaced negative charges associated with the phosphate groups are responsible for ATP's high energy level compared to AMP. These negative charges create repulsion between the phosphate groups, making the bonds between them unstable. As a result, when one of the phosphate groups is broken off, a large amount of energy is released. This energy can be used for various cellular processes, making ATP the primary energy currency of the cell.

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  • 41. 

    Following glycolysis and the Krebs cycle and before the electron transport chain and oxidative phosphorylation,the carbon skeleton of glucose has been broken down to CO2. Most of the energy from the original glucose atthat point is still in the form of ________.

    • A.

      ATP

    • B.

      NADH

    • C.

      CO2

    • D.

      H2O

    Correct Answer
    B. NADH
    Explanation
    After the processes of glycolysis and the Krebs cycle, the carbon skeleton of glucose has been broken down to CO2. However, most of the energy from the original glucose is still in the form of NADH. NADH is a high-energy molecule that carries electrons to the electron transport chain, where it is used to generate ATP through oxidative phosphorylation. Therefore, NADH is the correct answer as it represents the form in which the majority of the energy from glucose is stored at this point in the metabolic pathway.

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  • 42. 

    Why might adding inorganic phosphate to a reaction mixture where glycolysis was rapidly proceeding help sustainthe metabolic pathway?

    • A.

      It would increase the amount of glucose available for catabolism.

    • B.

      The metabolic intermediates of glycolysis are phosphorylated

    • C.

      It would increase the oxygen supply available for aerobic respiration because each phosphate group has four oxygen atoms as constituents.

    • D.

      It increases the energy level of the electrons that are transferred to the electron transport chain where ATP is produced.

    Correct Answer
    B. The metabolic intermediates of glycolysis are phosphorylated
    Explanation
    Adding inorganic phosphate to a reaction mixture where glycolysis is rapidly proceeding would help sustain the metabolic pathway because the metabolic intermediates of glycolysis are phosphorylated. Phosphorylation is an important step in glycolysis, as it helps to trap glucose within the cell and allows for further breakdown of glucose molecules. By adding inorganic phosphate, it ensures that there is a sufficient supply of phosphorylated intermediates to continue the glycolytic process and generate energy for the cell.

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  • 43. 

    A metabolic pathway, glycolysis, is active when cellular energy levels are ________; the regulatory enzyme,phosphofructokinase, is ________ by ATP.

    • A.

      High; activated

    • B.

      Low; inhibited

    • C.

      Low; activated

    • D.

      High; inhibited

    Correct Answer
    B. Low; inhibited
    Explanation
    Glycolysis is a metabolic pathway that breaks down glucose to produce energy. When cellular energy levels are low, it indicates that the cell needs more energy. In this situation, glycolysis is active to generate additional energy. Phosphofructokinase is a regulatory enzyme in glycolysis that controls the rate of the pathway. When ATP levels are high, it means that the cell already has sufficient energy, and glycolysis needs to be inhibited to prevent unnecessary energy production. Therefore, when cellular energy levels are low, phosphofructokinase is inhibited by ATP.

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  • 44. 

    Substrate-level phosphorylation occurs within a metabolic pathway where sufficient energy is released by a givenchemical reaction to drive the synthesis of ATP from ADP and phosphate. Substrate-level phosphorylation is seenin which metabolic pathway(s)?

    • A.

      Krebs Cycle

    • B.

      Both glycolysis and the Krebs cycle

    • C.

      Electron transport chain

    • D.

      All of the above pathways involve steps where substrate level phosphorylation takes place

    • E.

      Glycolysis

    Correct Answer
    B. Both glycolysis and the Krebs cycle
    Explanation
    Both glycolysis and the Krebs cycle involve steps where substrate-level phosphorylation takes place. In substrate-level phosphorylation, energy is released from a chemical reaction and used to convert ADP and phosphate into ATP. This process occurs in both glycolysis and the Krebs cycle, allowing for the production of ATP in these metabolic pathways. The electron transport chain, on the other hand, does not directly involve substrate-level phosphorylation. Therefore, the correct answer is both glycolysis and the Krebs cycle.

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  • 45. 

    Which of these statements concerning the following reaction is true?Malate + NAD+ → oxaloacetate + NADH + H+

    • A.

      Malate is more oxidized than oxaloacetate.

    • B.

      Oxaloacetate is more reduced than malate.

    • C.

      NAD+ is more reduced than NADH.

    • D.

      Malate is more reduced than oxaloacetate.

    Correct Answer
    D. Malate is more reduced than oxaloacetate.
    Explanation
    Malate is more reduced than oxaloacetate because it gains electrons and a proton (H+) to form oxaloacetate. In this reaction, malate acts as a reducing agent, donating electrons and a proton to another molecule (oxaloacetate). Oxaloacetate, on the other hand, is more oxidized because it accepts the electrons and proton from malate. Therefore, malate is more reduced compared to oxaloacetate.

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  • 46. 

    Which of the following events takes place in the electron transport chain?

    • A.

      The breakdown of an acetyl group to carbon dioxide

    • B.

      Breakdown of glucose into two pyruvate molecules

    • C.

      Substrate-level phosphorylation

    • D.

      The extraction of energy from high-energy electrons remaining from glycolysis and the Krebs cycle

    Correct Answer
    D. The extraction of energy from high-energy electrons remaining from glycolysis and the Krebs cycle
    Explanation
    The electron transport chain is the final stage of cellular respiration, where high-energy electrons from glycolysis and the Krebs cycle are transferred through a series of protein complexes. As these electrons move along the chain, their energy is gradually released and used to generate ATP, the main energy currency of the cell. Therefore, the extraction of energy from high-energy electrons remaining from glycolysis and the Krebs cycle is the event that takes place in the electron transport chain.

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  • 47. 

    Which of the following statements about the electron transport chain is true?

    • A.

      Electrons are received from NADH and FADH2.

    • B.

      Electrons are passed from donor to recipient carrier molecules in a series of oxidation-reduction reactions.

    • C.

      Usually the terminal electron acceptor is oxygen.

    • D.

      Most of the enzymes are part of the inner mitochondrial membrane

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    The given correct answer is "All of the above". This means that all of the statements mentioned in the options are true. The electron transport chain receives electrons from NADH and FADH2, and these electrons are passed from donor to recipient carrier molecules in a series of oxidation-reduction reactions. Usually, the terminal electron acceptor in the electron transport chain is oxygen. Additionally, most of the enzymes involved in this process are found in the inner mitochondrial membrane.

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  • 48. 

    Animals inhale air containing oxygen and exhale air with less oxygen and more carbon dioxide. Afterinhalation, the extra oxygen from the air will mostly be found in

    • A.

      Water

    • B.

      Organic molecules.

    • C.

      Ethanol

    • D.

      Lactate

    • E.

      The carbon dioxide that is exhaled.

    Correct Answer
    A. Water
    Explanation
    During inhalation, animals take in oxygen from the air. This oxygen is transported through the bloodstream and binds to hemoglobin in red blood cells. It is then delivered to cells throughout the body, where it is used in cellular respiration. In this process, oxygen is used to break down organic molecules, such as glucose, to produce energy. The byproducts of this process are carbon dioxide and water. Therefore, the extra oxygen from the inhaled air will mostly be found in water, as it is a product of cellular respiration.

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  • 49. 

    Fatty acids typically have an even number of carbons. They are catabolized by a process called beta-oxidation.The end-products of the metabolic pathway are acetyl groups of acetyl CoA molecules. What is the most likelyfate of the acetyl groups?

    • A.

      They directly enter the electron transport chain.

    • B.

      They are directly decarboxylated by pyruvate dehydrogenase.

    • C.

      They directly enter the energy-yielding stages of glycolysis.

    • D.

      They directly enter the Krebs cycle

    Correct Answer
    D. They directly enter the Krebs cycle
    Explanation
    Acetyl groups derived from fatty acids enter the Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid cycle. The Krebs cycle is a series of chemical reactions that occurs in the mitochondria of cells and is an essential part of cellular respiration. Acetyl CoA, which is produced during beta-oxidation of fatty acids, combines with oxaloacetate to form citrate, initiating the Krebs cycle. This cycle generates ATP, NADH, and FADH2, which are then used in the electron transport chain to produce more ATP through oxidative phosphorylation. Therefore, the most likely fate of the acetyl groups is to directly enter the Krebs cycle.

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  • 50. 

    10 Multiple Choice Average Score 0.65 pointsWhich of the following statements concerning cellular metabolism is false?

    • A.

      Glycolysis is inhibited when cellular energy levels are abundant.

    • B.

      Krebs cycle activity is dependent solely on availability of substrate; otherwise it is unregulated.

    • C.

      Reactions of the Krebs cycle take place in the mitochondrial matrix.

    • D.

      In the electron transport chain, electrons decrease in energy level as they are transferred from one electron carrier to the next.

    Correct Answer
    B. Krebs cycle activity is dependent solely on availability of substrate; otherwise it is unregulated.
    Explanation
    The statement that Krebs cycle activity is dependent solely on availability of substrate; otherwise it is unregulated is false. The Krebs cycle, also known as the citric acid cycle, is tightly regulated by various factors such as the concentration of ATP, NADH, and other intermediates. The rate of the Krebs cycle is influenced by the energy needs of the cell and the availability of substrates, but it is also regulated by feedback inhibition and allosteric regulation. Therefore, the activity of the Krebs cycle is not solely dependent on substrate availability.

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