Human Biology Exam: MCQ Quiz!

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Human Biology Exam: MCQ Quiz! - Quiz

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Questions and Answers
  • 1. 

    One characteristic of lipids is:

    • A.

      They dissolve well in water.

    • B.

      They are usually non-polar.

    • C.

      They usually form hydrogen bonds with each other.

    • D.

      They contain only carbon and no other element.

    Correct Answer
    B. They are usually non-polar.
    Explanation
    Lipids are usually non-polar because they consist of long hydrocarbon chains, which are made up of carbon and hydrogen atoms. The absence of polar groups in lipids prevents them from forming hydrogen bonds with water molecules. Instead, lipids tend to cluster together and form non-polar environments, such as cell membranes, where they play a crucial role in providing insulation and energy storage.

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  • 2. 

    Which is the unit of life which is made up of cells of one type performing a specific function?

    • A.

      A cell

    • B.

      A tissue

    • C.

      An organ

    • D.

      An organelle

    Correct Answer
    B. A tissue
    Explanation
    A tissue is a unit of life that is made up of cells of one type performing a specific function. Tissues are groups of cells that work together to carry out a particular function in an organism. Each type of tissue has a specific role and contributes to the overall functioning of the organism. Examples of tissues include muscle tissue, nervous tissue, and epithelial tissue.

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  • 3. 

    Most of the molecules in cell membranes that form channels or pores are:

    • A.

      Phospholipids

    • B.

      Lipids

    • C.

      Proteins

    • D.

      Carbohydrates

    Correct Answer
    C. Proteins
    Explanation
    The correct answer is proteins. Proteins are the main components of cell membranes that form channels or pores. These channels and pores allow for the selective transport of molecules and ions across the membrane, regulating the movement of substances in and out of the cell. While lipids, such as phospholipids, are also important components of cell membranes, they primarily form the lipid bilayer structure of the membrane rather than the channels or pores. Carbohydrates play a role in cell recognition and signaling, but they are not the main molecules involved in forming channels or pores in cell membranes.

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  • 4. 

    Which of these organelles makes ATP?

    • A.

      Mitochondria

    • B.

      Ribosomes

    • C.

      Golgi Bodies

    • D.

      Smooth Endoplasmic Reticula

    Correct Answer
    A. Mitochondria
    Explanation
    Mitochondria is the correct answer because it is the organelle responsible for producing ATP (adenosine triphosphate), which is the main source of cellular energy. Mitochondria have their own DNA and are capable of carrying out aerobic respiration, a process that generates ATP through the breakdown of glucose and other molecules. This ATP is then used by the cell to carry out various metabolic activities and provide energy for cellular functions.

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  • 5. 

    Which of the following is a cellular structure with two membranes, the inner of which is folded?

    • A.

      Ribosomes

    • B.

      Golgi Bodies

    • C.

      Mitochondria

    • D.

      Lysosomes

    Correct Answer
    C. Mitochondria
    Explanation
    Mitochondria is the correct answer because it is a cellular structure that has two membranes, with the inner membrane being folded. The folds in the inner membrane are called cristae, and they increase the surface area available for chemical reactions involved in energy production. Mitochondria are known as the powerhouse of the cell because they generate most of the cell's energy through a process called cellular respiration.

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  • 6. 

    In which of the following is glucose split into two molecules of 3 carbons each?

    • A.

      Ribosomes

    • B.

      Glycolysis

    • C.

      Electron Transport Chain

    • D.

      Krebs Cycle

    Correct Answer
    B. Glycolysis
    Explanation
    Glycolysis is the correct answer because it is the process in which glucose is broken down into two molecules of 3 carbons each, known as pyruvate. This process occurs in the cytoplasm of cells and is the first step in cellular respiration, providing energy for the cell in the form of ATP.

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  • 7. 

    Water will move into a cell if:

    • A.

      The membrane is not too thick.

    • B.

      The cell is not too large.

    • C.

      Water is of higher concentration outside the cell.

    • D.

      Water is attached to another molecule such as a phospholipid.

    Correct Answer
    C. Water is of higher concentration outside the cell.
    Explanation
    This process occurs through osmosis, where water moves across a semi-permeable membrane from an area of higher concentration to an area of lower concentration until equilibrium is reached.

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  • 8. 

    The method of movement across a membrane of a molecule from a region of low concentration to a region of high concentration is called:

    • A.

      Passive transport

    • B.

      Osmosis

    • C.

      Facilitated diffusion

    • D.

      Active transport

    Correct Answer
    D. Active transport
    Explanation
    Active transport is the method of movement across a membrane of a molecule from a region of low concentration to a region of high concentration. This process requires the use of energy in the form of ATP to transport molecules against their concentration gradient. Unlike passive transport, active transport moves molecules against the natural flow, allowing cells to maintain specific concentrations of molecules inside and outside the cell. Osmosis is the movement of water molecules across a membrane, facilitated diffusion is the movement of molecules across a membrane with the help of transport proteins, and passive transport refers to the movement of molecules down their concentration gradient without the use of energy.

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  • 9. 

    Which is true of Active Transport?

    • A.

      Only large molecules are moved across a membrane.

    • B.

      A portion of the membrane dissolves when active transport occurs.

    • C.

      It requires a membrane lipid which forms a hole in the membrane.

    • D.

      It requires energy, usually in the form of ATP.

    Correct Answer
    D. It requires energy, usually in the form of ATP.
    Explanation
    Active transport is a process in which molecules are moved across a membrane against their concentration gradient, requiring energy. ATP (adenosine triphosphate) is a molecule that provides the necessary energy for active transport. Therefore, the statement "It requires energy, usually in the form of ATP" is correct. This energy is used to pump molecules across the membrane, allowing for the movement of substances such as ions or nutrients against their concentration gradient.

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  • 10. 

    The atomic number and the atomic weight of an element:

    • A.

      Do not count the weight of electrons.

    • B.

      Both include the weight of the electrons, but only the atomic number includes the number of neutrons.

    • C.

      Both include the weight of the protons of the element.

    • D.

      Are actually the same thing.

    Correct Answer(s)
    A. Do not count the weight of electrons.
    C. Both include the weight of the protons of the element.
    Explanation
    The atomic number of an element represents the number of protons in its nucleus, while the atomic weight includes the combined mass of both protons and neutrons. However, electrons have such a small mass compared to protons and neutrons that they are not considered when determining the atomic number or atomic weight. Therefore, the correct answer is that both the atomic number and atomic weight do not count the weight of electrons, and both include the weight of the protons of the element.

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  • 11. 

    How many molecules of Carbon dioxide (CO2) are eventually produced from one molecule of glucose?

    • A.

      0

    • B.

      2

    • C.

      4

    • D.

      6

    Correct Answer
    D. 6
    Explanation
    One molecule of glucose undergoes a process called cellular respiration, which involves several biochemical reactions. During this process, one molecule of glucose is completely broken down, resulting in the production of six molecules of carbon dioxide (CO2). Therefore, six molecules of carbon dioxide are eventually produced from one molecule of glucose.

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  • 12. 

    Magnesium has 12 protons. How many electrons are in its second shell?

    • A.

      4

    • B.

      8

    • C.

      12

    • D.

      16

    Correct Answer
    B. 8
    Explanation
    The second shell of an atom can hold a maximum of 8 electrons. Since magnesium has 12 protons, it also has 12 electrons. The first shell can hold a maximum of 2 electrons, so 2 electrons will be in the first shell, leaving 10 electrons for the second shell. Therefore, the correct answer is 8.

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  • 13. 

    A water molecule is polar due to the presence of:

    • A.

      An ionic bond.

    • B.

      Carbon attached to a hydrogen.

    • C.

      Oxygen.

    • D.

      Too many electrons in its outer shell.

    Correct Answer
    C. Oxygen.
    Explanation
    A water molecule is polar due to the presence of oxygen. Oxygen is more electronegative than hydrogen, meaning it has a stronger attraction for electrons. As a result, oxygen pulls the shared electrons in the water molecule towards itself, creating a partial negative charge. The hydrogen atoms, on the other hand, have a partial positive charge. This uneven distribution of charges gives water its polarity, making it capable of forming hydrogen bonds and exhibiting properties like high surface tension and the ability to dissolve various substances.

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  • 14. 

    Which of the following atoms has gained a single electron?

    • A.

      Na+

    • B.

      Cl-

    • C.

      An unreacted Na.

    • D.

      An atom with 10 protons in its nucleus.

    Correct Answer
    B. Cl-
    Explanation
    Chlorine (Cl-) has gained a single electron. Chlorine typically has 17 electrons, but when it gains one more electron, it becomes negatively charged (Cl-) and has a total of 18 electrons.

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  • 15. 

    The bond that forms when a Hydrogen atom attaches to an Oxygen atom is called:

    • A.

      Sharing of electrons between two hydrogen atoms.

    • B.

      A non-polar bond.

    • C.

      A polar bond.

    • D.

      A hydrogen bond

    Correct Answer
    C. A polar bond.
    Explanation
    When a hydrogen atom attaches to an oxygen atom, the electrons are not shared equally between them. The oxygen atom is more electronegative than the hydrogen atom, meaning it attracts the shared electrons more strongly. This creates a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atom, resulting in a polar bond.

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  • 16. 

    The part of a membrane which forms a middle layer of the two layers of phospholipids is:

    • A.

      Dissolved in water.

    • B.

      Made up of proteins.

    • C.

      Made of the fatty acid tails of the phospholipids.

    • D.

      Highly polar.

    Correct Answer
    C. Made of the fatty acid tails of the phospholipids.
    Explanation
    The middle layer of the two layers of phospholipids in a membrane is made up of the fatty acid tails of the phospholipids. Phospholipids have a polar head and nonpolar tails, with the heads facing outward towards the water and the tails facing inward, away from the water. This arrangement forms a lipid bilayer, with the hydrophobic tails in the middle and the hydrophilic heads on the outer surfaces. Therefore, the correct answer is that the middle layer of the membrane is made of the fatty acid tails of the phospholipids.

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  • 17. 

    In the reaction ADP + Phosphate + Energy ---> ATP, one can say that:

    • A.

      Energy is created.

    • B.

      The reaction cannot occur.

    • C.

      Energy is lost.

    • D.

      Energy is stored.

    Correct Answer
    D. Energy is stored.
    Explanation
    In the given reaction, ADP and phosphate combine to form ATP, along with the release of energy. This energy is not lost or created, but rather stored in the ATP molecule. ATP acts as a form of energy currency in cells, where it can be used to fuel various cellular processes. Therefore, the correct answer is that energy is stored.

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  • 18. 

    Which of the following is a polymer of glucose?

    • A.

      Starch

    • B.

      Glycogen

    • C.

      Cellulose

    • D.

      All of a, b and c are polymers of glucose.

    Correct Answer
    D. All of a, b and c are polymers of glucose.
    Explanation
    Starch, glycogen, and cellulose are all polymers of glucose. Starch is a polysaccharide found in plants and serves as a storage form of glucose. Glycogen is a polysaccharide found in animals and acts as a storage form of glucose in the liver and muscles. Cellulose is a polysaccharide found in the cell walls of plants and provides structural support. All three substances are composed of repeating units of glucose molecules, making them polymers of glucose.

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  • 19. 

    A peptide bond forms between ________ when forming a protein.

    • A.

      Ions

    • B.

      Water and oxygen

    • C.

      Two amino acids

    • D.

      Two glucose molecules

    Correct Answer
    C. Two amino acids
    Explanation
    A peptide bond forms between two amino acids when forming a protein. Amino acids are the building blocks of proteins, and when two amino acids come together, a peptide bond is formed. This bond is a covalent bond that links the carboxyl group of one amino acid to the amino group of another amino acid. This process, known as peptide bond formation or condensation reaction, occurs through the removal of a water molecule. The resulting chain of amino acids forms the backbone of the protein structure.

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  • 20. 

    Which of the following is produced during the formation of all polymers?

    • A.

      Water

    • B.

      Carbon dioxide

    • C.

      Oxygen

    • D.

      A 6-carbon molecule

    Correct Answer
    A. Water
    Explanation
    During the formation of polymers, water is produced as a byproduct. This process is known as dehydration synthesis or condensation reaction, where monomers join together to form a polymer by removing a water molecule. Therefore, water is a common byproduct in the formation of all polymers.

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  • 21. 

    Which of the following is evidence of quaternary protein structure?

    • A.

      Two separate peptides (=proteins) attached together.

    • B.

      A folding of a protein.

    • C.

      An unfolded protein.

    • D.

      A very long protein, unfolded.

    Correct Answer
    A. Two separate peptides (=proteins) attached together.
    Explanation
    The evidence of quaternary protein structure is the presence of two separate peptides (proteins) attached together. Quaternary structure refers to the arrangement of multiple protein subunits to form a functional protein complex. In this case, the attachment of two separate peptides indicates the formation of a larger protein structure consisting of multiple subunits. This is a characteristic feature of quaternary protein structure.

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  • 22. 

    During cellular respiration, the electrons carried by FADH2 from the Krebs cycle end up:

    • A.

      In water.

    • B.

      As part of ATP.

    • C.

      As part of ADP.

    • D.

      Being transferred to Carbon dioxide (CO2)

    Correct Answer
    A. In water.
    Explanation
    During cellular respiration, FADH2 transfers its electrons to the electron transport chain. This chain consists of protein complexes that pass the electrons along, ultimately leading to the formation of water. The electrons from FADH2 combine with oxygen and hydrogen ions to form water molecules. Therefore, the electrons carried by FADH2 end up in water.

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  • 23. 

    Which of the following organelles is actually a small, particle and not a membrane?

    • A.

      Golgi complex

    • B.

      A ribosome

    • C.

      Mitochondrion

    • D.

      Lysosome

    Correct Answer
    B. A ribosome
    Explanation
    A ribosome is a small particle that is responsible for protein synthesis within a cell. It is not surrounded by a membrane, unlike other organelles such as the Golgi complex, mitochondrion, and lysosome. The absence of a membrane allows ribosomes to be free-floating in the cytoplasm or attached to the endoplasmic reticulum. This characteristic of being a small particle without a membrane makes a ribosome distinct from the other organelles listed.

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  • 24. 

    The energy which is used by the electron transport chain to produce ATP comes from:

    • A.

      ADP formed in glycolysis.

    • B.

      ADP formed in the Krebs cycle.

    • C.

      Electrons which came from glucose breakdown.

    • D.

      CO2 (carbon dioxide)

    Correct Answer
    C. Electrons which came from glucose breakdown.
    Explanation
    The electron transport chain is a series of protein complexes in the inner mitochondrial membrane that transfer electrons from electron donors to electron acceptors. In cellular respiration, glucose is broken down in a series of reactions, producing electrons that are carried by electron carriers such as NADH and FADH2. These electron carriers donate their electrons to the electron transport chain, which uses the energy from the electron transfer to pump protons across the membrane, creating a proton gradient. This gradient is then used by ATP synthase to produce ATP. Therefore, the energy used by the electron transport chain to produce ATP comes from the electrons that came from glucose breakdown.

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  • 25. 

    Most ATP production in the mitochondrion occurs when ________ through ________.

    • A.

      H+ ions ; ATP synthase

    • B.

      Water ; water pores

    • C.

      Electrons ; ATP synthase

    • D.

      ADP ; protein complexes of the electron transport chain

    Correct Answer
    A. H+ ions ; ATP synthase
    Explanation
    ATP production in the mitochondrion occurs through the process of oxidative phosphorylation. During this process, electrons from NADH and FADH2 are passed through a series of protein complexes in the electron transport chain. As electrons move through these complexes, they create a proton gradient across the inner mitochondrial membrane. H+ ions then flow back into the mitochondrial matrix through ATP synthase, which uses the energy from this flow to generate ATP. Therefore, the correct answer is H+ ions ; ATP synthase.

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  • 26. 

    When carbon reacts, it usually:

    • A.

      Forms only polar bonds.

    • B.

      Has gained electrons from another atom.

    • C.

      Has lost electrons to another atom.

    • D.

      Shares electrons with other atoms.

    Correct Answer
    D. Shares electrons with other atoms.
    Explanation
    Carbon is an element that has four valence electrons. In order to achieve a stable electron configuration, carbon can form covalent bonds by sharing its valence electrons with other atoms. This allows carbon to complete its outer electron shell and become more stable. Therefore, the correct answer is that carbon shares electrons with other atoms.

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  • 27. 

    Three of the four answers listed below are actually members of the same tissue type. Select the exception.

    • A.

      Blood

    • B.

      Epithelium

    • C.

      Bone

    • D.

      Cartilage

    Correct Answer
    B. Epithelium
    Explanation
    Blood, bone, and cartilage are all connective tissues, whereas epithelium is a type of tissue that covers the surfaces of organs and lines body cavities. Therefore, epithelium is the exception as it does not belong to the same tissue type as the other three options.

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  • 28. 

    The correct operational sequence of the three processes listed below is:

    • A.

      Glycolysis >> Krebs cycle >> electron transport

    • B.

      Electron transport >> Krebs cycle >> glycolysis

    • C.

      Krebs cycle >> glycolysis >> electron transport

    • D.

      Glycolysis >> electron transport >> Krebs cycle

    Correct Answer
    A. Glycolysis >> Krebs cycle >> electron transport
    Explanation
    The correct operational sequence of the three processes is glycolysis, Krebs cycle, and electron transport. Glycolysis is the first step in cellular respiration where glucose is broken down into pyruvate. The pyruvate then enters the Krebs cycle, where it is further broken down and releases energy-rich molecules such as ATP and NADH. The final step is the electron transport chain, where the NADH produced in the previous steps is used to generate ATP through oxidative phosphorylation. Therefore, the correct sequence is glycolysis, Krebs cycle, and electron transport.

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  • 29. 

    During cellular respiration, electron energy is necessary to:

    • A.

      Actively transport H+ ions in order to allow ATP formation.

    • B.

      Cause dehydration reactions (= condensation reactions).

    • C.

      Move water across the electron transport chain.

    • D.

      Remove phosphate from ADP.

    Correct Answer
    A. Actively transport H+ ions in order to allow ATP formation.
    Explanation
    During cellular respiration, electron energy is necessary to actively transport H+ ions in order to allow ATP formation. This is because electron energy is used to pump H+ ions across the inner mitochondrial membrane, creating a concentration gradient. This gradient is then used by ATP synthase to produce ATP through chemiosmosis. Therefore, electron energy is crucial for the active transport of H+ ions, which ultimately leads to the formation of ATP.

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  • 30. 

    Which of the following would have already accepted 2 electrons?

    • A.

      NAD+

    • B.

      NADH

    • C.

      CO2

    • D.

      ADP

    Correct Answer
    B. NADH
    Explanation
    NADH would have already accepted 2 electrons because it is the reduced form of NAD+ (nicotinamide adenine dinucleotide). NAD+ can accept 2 electrons and a hydrogen ion (H+) to form NADH during cellular respiration. This reduction reaction is an important step in the production of ATP, the energy currency of cells.

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  • 31. 

    When one has reached the end of glycolysis, one can say that:

    • A.

      The final molecule has 5 carbons.

    • B.

      Glucose has been formed.

    • C.

      ATP has been used.

    • D.

      CO2 has been released.

    Correct Answer
    C. ATP has been used.
    Explanation
    In glycolysis, ATP is used as an energy source to convert glucose into pyruvate. This process involves the breakdown of glucose into two molecules of pyruvate, and during this process, two molecules of ATP are consumed. Therefore, when one has reached the end of glycolysis, it can be concluded that ATP has been used.

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  • 32. 

    In order to remove electrons which have completed their journey through the electron transport chain, they will be moved to:

    • A.

      FAD

    • B.

      ATP

    • C.

      Oxygen

    • D.

      NAD+

    Correct Answer
    C. Oxygen
    Explanation
    Electrons that have completed their journey through the electron transport chain are moved to oxygen. Oxygen acts as the final electron acceptor in the electron transport chain, accepting the electrons and combining with hydrogen ions to form water. This process is essential for the production of ATP, the energy currency of the cell. Oxygen's role as the final electron acceptor ensures the continuation of the electron flow and the generation of a proton gradient, which drives ATP synthesis.

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  • 33. 

    Which two particles are always equal in number in an unreacted atom?

    • A.

      Electrons and protons

    • B.

      Electrons and neutrons

    • C.

      Protons and neutrons

    • D.

      None of the above answers are correct.

    Correct Answer
    A. Electrons and protons
    Explanation
    In an unreacted atom, the number of electrons is always equal to the number of protons. This is because electrons carry a negative charge, while protons carry a positive charge. In a neutral atom, the positive charge of the protons cancels out the negative charge of the electrons, resulting in a balanced atom. Therefore, the correct answer is electrons and protons.

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  • 34. 

    Which of the following will have equal but opposite charges?

    • A.

      Protons and neutrons

    • B.

      Protons and electrons

    • C.

      Electrons and neutrons

    • D.

      Neutrons and ions

    Correct Answer
    B. Protons and electrons
    Explanation
    Protons and electrons will have equal but opposite charges. Protons have a positive charge, while electrons have a negative charge. The charges of protons and electrons are equal in magnitude but opposite in sign, resulting in an attraction between them. This attraction is what holds atoms together, as protons and electrons are found in the nucleus and electron cloud, respectively.

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  • 35. 

    In which of the following would one produce a molecule which contains only 5 carbons?

    • A.

      Glycolysis

    • B.

      ATP synthase

    • C.

      The preparatory reaction just before entering the Krebs cycle.

    • D.

      Krebs cycle

    Correct Answer
    D. Krebs cycle
    Explanation
    The Krebs cycle is the correct answer because it is the stage in cellular respiration where acetyl-CoA, a molecule with two carbons, enters the cycle and combines with oxaloacetate, a molecule with four carbons, to form citrate, a molecule with six carbons. As the cycle progresses, citrate is gradually broken down, resulting in the production of carbon dioxide and the regeneration of oxaloacetate. Therefore, the Krebs cycle ultimately produces molecules with only five carbons.

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  • 36. 

    The monomers involved in this are called simple sugars.

    • A.

      Proteins

    • B.

      Lipids

    • C.

      Polysaccharides

    • D.

      All of the above.

    Correct Answer
    C. Polysaccharides
    Explanation
    Polysaccharides are complex carbohydrates made up of multiple monosaccharide units joined together through glycosidic bonds. They are the main storage form of carbohydrates in plants and animals and serve as an energy source. Unlike simple sugars, which are monomers, polysaccharides are large molecules that can be composed of hundreds or thousands of monosaccharide units. Therefore, the statement that "The monomers involved in this are called simple sugars" is incorrect.

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  • 37. 

    Which of the following has monomers which are put together by dehydration reactions?

    • A.

      Proteins

    • B.

      Lipids

    • C.

      Polysaccharides

    • D.

      All of the above.

    Correct Answer
    D. All of the above.
    Explanation
    All of the given options, proteins, lipids, and polysaccharides, have monomers that are joined together through dehydration reactions. Dehydration reactions involve the removal of a water molecule to form a covalent bond between monomers. In proteins, amino acids are linked together through peptide bonds. In lipids, fatty acids are joined to glycerol through ester bonds. In polysaccharides, such as starch and cellulose, monosaccharides are connected through glycosidic bonds. Therefore, all of these macromolecules are formed by dehydration reactions.

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  • 38. 

    Which of the following has monomers which are put together in ribosomes?

    • A.

      Proteins

    • B.

      Lipids

    • C.

      Polysaccharides

    • D.

      All of the above.

    Correct Answer
    A. Proteins
    Explanation
    Proteins are the only option among the given choices that have monomers put together in ribosomes. Ribosomes are responsible for protein synthesis, where amino acids are joined together to form a polypeptide chain. Lipids and polysaccharides do not undergo this process and are not assembled in ribosomes.

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  • 39. 

    Which of the following form or make up all membranes?

    • A.

      Proteins

    • B.

      Lipids

    • C.

      Polysaccharides

    • D.

      All of the above.

    Correct Answer
    B. Lipids
    Explanation
    Lipids form or make up all membranes. Lipids are a type of biomolecule that includes fats, oils, and phospholipids. They have a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail, which allows them to form a bilayer structure in cell membranes. This lipid bilayer provides a barrier that separates the inside of the cell from its external environment. Proteins and polysaccharides may also be present in membranes, but lipids are the primary component responsible for their formation.

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  • 40. 

    A cell membrane is considered to be a bilayer (two-layered) because it is made up of:

    • A.

      Two layers of protein on either side of a layer of water.

    • B.

      Two layers of proteins.

    • C.

      Two layers of phospholipids.

    • D.

      Two layers of cholesterol, a lipid.

    Correct Answer
    C. Two layers of phospholipids.
    Explanation
    The cell membrane is composed of a bilayer of phospholipids. Phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. In the cell membrane, the hydrophilic heads face the watery environment both inside and outside the cell, while the hydrophobic tails face each other in the middle of the membrane. This arrangement forms a stable barrier that separates the cell from its surroundings. The presence of two layers of phospholipids gives the cell membrane its characteristic structure and allows it to regulate the passage of molecules in and out of the cell.

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  • 41. 

    The Krebs cycle starts and ends with:

    • A.

      Glucose

    • B.

      Pyruvate

    • C.

      A 4-carbon molecule

    • D.

      ATP

    Correct Answer
    C. A 4-carbon molecule
    Explanation
    The Krebs cycle starts and ends with a 4-carbon molecule. This molecule, called oxaloacetate, combines with acetyl-CoA to form citrate, which then goes through a series of reactions to produce energy-rich molecules such as ATP. At the end of the cycle, the 4-carbon molecule is regenerated to start the cycle again. Glucose and pyruvate are involved in earlier stages of cellular respiration, but they are not the molecules that start and end the Krebs cycle.

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  • 42. 

    List the biological levels in order of size and complexity:

    • A.

      Protein, organ, cell, tissue, species, population, ecosystem

    • B.

      Protein, cell, organelle, organ, organism, population, ecosystem

    • C.

      Atom, protein, tissue, organelle, species, population, ecosystem

    • D.

      Atom, molecule, cell, tissue, organ, population, ecosystem

    Correct Answer
    D. Atom, molecule, cell, tissue, organ, population, ecosystem
    Explanation
    The correct answer is "atom, molecule, cell, tissue, organ, population, ecosystem." This order starts with the smallest and simplest unit of matter, the atom, and progresses to larger and more complex structures. Molecules are formed by the combination of atoms, cells are the basic building blocks of life, tissues are groups of cells working together, organs are composed of different tissues working together, populations consist of a group of individuals of the same species, and ecosystems are made up of populations of different species interacting with each other and their environment.

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  • 43. 

    What is the ultimate source of energy for humans?

    • A.

      Plants

    • B.

      ATP

    • C.

      Sunlight

    • D.

      Protein

    Correct Answer
    C. Sunlight
    Explanation
    Sunlight is the ultimate source of energy for humans because it is captured by plants through photosynthesis. Plants convert sunlight into chemical energy in the form of glucose, which is then used by humans and other animals as a source of energy through the process of cellular respiration. ATP and protein are important for energy production and cellular functions in the human body, but they are not the ultimate source of energy.

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  • 44. 

    Which of the following determines what element an atom is?

    • A.

      Protons

    • B.

      Neutrons

    • C.

      Electrons

    • D.

      Neurons

    Correct Answer
    A. Protons
    Explanation
    Protons determine what element an atom is because they carry a positive charge and their number in the nucleus determines the atomic number of the element. Each element has a unique number of protons, which distinguishes it from other elements. Neutrons and electrons also play important roles in the atom, but they do not determine the identity of the element. Neurons, on the other hand, have no direct relevance to the determination of an atom's element.

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  • 45. 

    If you were a cholesterol molecule, with which of the following would you interact with most easily?

    • A.

      DNA

    • B.

      Glucose

    • C.

      Phospholipids

    • D.

      Amino acids

    Correct Answer
    C. Phospholipids
    Explanation
    Cholesterol is a type of lipid molecule that is primarily found in cell membranes. Phospholipids are also a type of lipid molecule that make up the majority of the cell membrane. Due to their similar chemical properties, cholesterol molecules can easily interact with phospholipids in the cell membrane. This interaction helps maintain the fluidity and stability of the cell membrane. On the other hand, DNA, glucose, and amino acids are not lipid molecules and do not have the same chemical properties as cholesterol, making it more difficult for cholesterol to interact with them.

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  • 46. 

    Which tissues can be found in the heart?

    • A.

      Cardiac muscles

    • B.

      Nervous tissues

    • C.

      Connective tissues

    • D.

      All of the above are found in the heart.

    Correct Answer
    D. All of the above are found in the heart.
    Explanation
    The heart contains cardiac muscles, which are responsible for its contraction and pumping action. It also contains nervous tissues, which help regulate the heart's activity and control its rhythm. Additionally, connective tissues are found in the heart, providing support and structure to the organ. Therefore, all of the mentioned tissues can be found in the heart.

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  • 47. 

    The type of cells shown in the illustration below are from:

    • A.

      Blood

    • B.

      Striated muscle

    • C.

      Smooth muscle

    • D.

      Nerve

    Correct Answer
    D. Nerve
    Explanation
    The cells shown in the illustration are nerve cells, also known as neurons. Neurons are specialized cells that transmit electrical signals throughout the body, allowing for communication between different parts of the nervous system. These cells have a unique structure with long projections called axons and dendrites, which help in transmitting and receiving signals. The presence of a single, elongated cell body with branching projections indicates that the cells in the illustration are nerve cells.

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  • 48. 

    In the following diagram, which numbered arrow points to the most polar region?

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    Correct Answer
    A. 1
    Explanation
    The correct answer is 1 because the arrow is pointing towards the top of the diagram, indicating the North Pole, which is the most polar region on Earth. The other arrows are pointing towards different directions, but none of them are pointing towards the polar region.

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  • 49. 

    In the diagram below, which portion would interact with water most easily?

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    Correct Answer
    A. 1
    Explanation
    Portion 1 would interact with water most easily because it is directly exposed to the water. It is the only portion that is not blocked or covered by any other part of the diagram. Therefore, water can easily come into contact with portion 1, allowing for interaction to occur.

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  • 50. 

    Which of the following diagrams would accurately depict how water molecules form hydrogen bonds with each other? [The squiggle represents a hydrogen bond].

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    Correct Answer
    D. 4

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  • Current Version
  • Mar 08, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • May 09, 2010
    Quiz Created by
    Funkytrunks22
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