Biology Exam 2 Pt. 2
Jennifer schwartz class at PPCC
- 1.
Which of the following functions as a recognition signal for interactions between cells?
- A.
RNA
- B.
Phospholipids
- C.
Cholesterol
- D.
Fatty acids
- E.
Glycolipids
Correct Answer
E. GlycolipidsExplanation
Glycolipids function as recognition signals for interactions between cells. These molecules are composed of a lipid portion and a carbohydrate portion. The carbohydrate portion on the cell surface acts as a marker, allowing cells to recognize and interact with each other. This recognition is crucial for various cellular processes such as cell adhesion, immune response, and development. Glycolipids play a vital role in cell communication and facilitate the recognition and binding of cells to form tissues and organs.Rate this question:
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- 2.
Which of the following represents the correct pathway for the synthesis and secretion of insulin, a protein secreted by the cells of the pancreas?
- A.
Rough ER; Golgi apparatus; vesicle; plasma membrane
- B.
Golgi Apparatus; rough ER; lysosome
- C.
Lysosome; vesicle; plasma membrane
- D.
Plasma membrane; cloated vesicle; lysosome
- E.
Rough ER; cytoplasm; plasma membrane
Correct Answer
A. Rough ER; Golgi apparatus; vesicle; plasma membraneExplanation
Insulin is a protein that is synthesized and secreted by the cells of the pancreas. The rough ER is responsible for the initial synthesis of proteins, including insulin. After synthesis, the proteins are transported to the Golgi apparatus, where they undergo further processing and packaging. From the Golgi apparatus, the insulin is packaged into vesicles, which then transport it to the plasma membrane. Finally, the insulin is secreted out of the cell through exocytosis, where it can then enter the bloodstream and regulate blood sugar levels. Therefore, the correct pathway for the synthesis and secretion of insulin is Rough ER; Golgi apparatus; vesicle; plasma membrane.Rate this question:
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- 3.
Cell growth can involve movement of membrane material from
- A.
The cell membrane to the vesicles
- B.
The Golgi apparatus to the cell membrane
- C.
The smooth ER to the rough ER
- D.
Coated pits to the inside of the cell.
- E.
The nuclear envelope directly to the cell membrane.
Correct Answer
B. The Golgi apparatus to the cell membraneExplanation
During cell growth, the Golgi apparatus plays a crucial role in the transport and modification of proteins and lipids. It receives membrane material from the endoplasmic reticulum (ER) and packages it into vesicles. These vesicles then fuse with the cell membrane, allowing the incorporation of new membrane material into the growing cell. Therefore, the movement of membrane material from the Golgi apparatus to the cell membrane is a plausible explanation for cell growth.Rate this question:
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- 4.
The difference between tight junctions, desmosomes and gap junctions is that
- A.
Desmosomes and gap junctions contain keratin, whereas tight junctions have collagen.
- B.
Gap junctions and tight junctions have specialized protein channels called connexons; desmosomes do not.
- C.
Tight juctions and desmosomes have mechanical roles, whereas gap junctions facilitate communication between cells.
- D.
Desmosomes and gap junctions are found in epithelial tissue, whereas tight junctions are found in nerve cells.
- E.
They all have different functions; however, their structure is the same.
Correct Answer
C. Tight juctions and desmosomes have mechanical roles, whereas gap junctions facilitate communication between cells.Explanation
Tight junctions and desmosomes play a mechanical role by providing strength and stability to tissues, while gap junctions facilitate communication between cells by allowing the passage of small molecules and ions. This distinction in function sets them apart from each other.Rate this question:
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- 5.
Which of the following does not affect the rate of diffusion of a substance?
- A.
Temperature of the solution
- B.
Concentration gradient
- C.
Electrical charge of the diffusing material
- D.
Presence of other substances in the solution
- E.
Molecular diameter of the diffusing material
Correct Answer
D. Presence of other substances in the solutionExplanation
The presence of other substances in the solution does not affect the rate of diffusion of a substance. Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration, and it is a passive process that occurs due to random motion of particles. The rate of diffusion is determined by factors such as temperature, concentration gradient, electrical charge, and molecular diameter. However, the presence of other substances in the solution does not directly impact the rate of diffusion.Rate this question:
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- 6.
Osmosis moves water from a region of ____ to a region of ____.
- A.
High concentration of dissolved material; low concentration of dissolved material
- B.
Low concentration of dissolved material; high concentration of dissolved material
- C.
Hypertonic solution; hypotonic solution
- D.
Negative osmotic potential; positive osmotic potential
- E.
Low concentration of water; high concentration of water
Correct Answer
B. Low concentration of dissolved material; high concentration of dissolved materialExplanation
Osmosis is the movement of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration. In this case, the correct answer is "low concentration of dissolved material; high concentration of dissolved material" because osmosis occurs in response to the concentration of dissolved solutes. Water will move from an area with a lower concentration of dissolved material (higher concentration of water) to an area with a higher concentration of dissolved material (lower concentration of water) in order to equalize the concentrations on both sides of the membrane.Rate this question:
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- 7.
Which of the following molecules is the most likely to diffuse across a cell membrane?
- A.
Glucose
- B.
Na*
- C.
A steroid
- D.
A common amino acid
- E.
Cl-
Correct Answer
C. A steroidExplanation
Steroids are lipid-soluble molecules that have a hydrophobic region, allowing them to easily cross the hydrophobic interior of the cell membrane. Unlike glucose, Na+, amino acids, and Cl-, which are hydrophilic and require specific transport mechanisms to cross the membrane, steroids can diffuse directly through the lipid bilayer. Therefore, a steroid is the most likely molecule to diffuse across a cell membrane.Rate this question:
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- 8.
When placed in a hypertonic solution, animal cells
- A.
Shrink.
- B.
Swell.
- C.
Burst.
- D.
Do not change.
- E.
Swell but not burst because of the cell wall.
Correct Answer
A. Shrink.Explanation
When placed in a hypertonic solution, animal cells will shrink. This is because a hypertonic solution has a higher concentration of solutes compared to the inside of the cell. As a result, water will move out of the cell through osmosis, causing the cell to shrink in size. The option stating that animal cells swell but not burst because of the cell wall is incorrect, as animal cells do not have a cell wall like plant cells do.Rate this question:
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- 9.
If a red blood cell is placed in an isotonic solution,
- A.
The cell will shrivel.
- B.
The cell will swell and burst.
- C.
The cell will shrivel and then return to normal.
- D.
The cell will swell and then return to normal.
- E.
Water moves into and out of the cell at an equal rate, but there is no net change.
Correct Answer
E. Water moves into and out of the cell at an equal rate, but there is no net change.Explanation
When a red blood cell is placed in an isotonic solution, it means that the concentration of solutes inside and outside the cell is the same. As a result, water moves into and out of the cell at an equal rate through the process of osmosis. This balanced movement of water prevents any net change in the size or shape of the cell, leading to no swelling, bursting, or shriveling. Therefore, the correct answer is that water moves into and out of the cell at an equal rate, but there is no net change.Rate this question:
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- 10.
The speed and direction of ions as they move into and out of the cell are determined by the
- A.
Ability of the ion to let go of its water
- B.
Concentration gradient and elec trochemical imbalances
- C.
Number of channel proteins present.
- D.
Size and charge of the ion.
- E.
Presence of specific stimuli to open gated channel proteins.
Correct Answer
B. Concentration gradient and elec trochemical imbalancesExplanation
The speed and direction of ions as they move into and out of the cell are determined by the concentration gradient and electrochemical imbalances. This means that ions will move from an area of high concentration to an area of low concentration, and the presence of electrochemical imbalances, such as differences in charge across the cell membrane, can also influence ion movement. This explanation suggests that the ability of the ion to let go of its water, the number of channel proteins present, and the size and charge of the ion are not the primary factors determining the speed and direction of ion movement.Rate this question:
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- 11.
One result of the movement of ions through ion channels is the creation of a membrane potential. The membrane potential is
- A.
A charge imbalance across the plasma membrane.
- B.
The difference in ion concentrations on either side of hte plasma membrane.
- C.
The difference in ATP concentration son either side of hte plasma membrane.
- D.
The capacity for active transport.
- E.
The ability of macromolecules to recognize and adhere to one another.
Correct Answer
A. A charge imbalance across the plasma membrane.Explanation
The movement of ions through ion channels leads to a charge imbalance across the plasma membrane. This means that there is an unequal distribution of positive and negative charges on either side of the membrane. This charge imbalance is what creates the membrane potential, which is essential for various cellular processes such as the transmission of nerve impulses and the uptake of nutrients.Rate this question:
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- 12.
In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the concentration difference of the molecule across the membrane increases becasue
- A.
Facilitated diffusion requires the use of ATP.
- B.
As the concentration difference increases, molecules interfere with one another.
- C.
The carrier proteins are saturated.
- D.
The transport protein must be of the channel type
- E.
The diffusion constant depends on the concentration difference.
Correct Answer
C. The carrier proteins are saturated.Explanation
The correct answer is that the carrier proteins are saturated. In facilitated diffusion, carrier proteins are responsible for transporting specific molecules across the membrane. However, these carrier proteins have a limited capacity or number of binding sites. Once all the binding sites are occupied by molecules, the diffusion rate cannot continue to increase even if the concentration difference across the membrane increases. This is because the carrier proteins are already saturated with molecules and cannot transport any more.Rate this question:
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- 13.
Active transport usually moves molecules
- A.
In the same direction as diffusion moves them.
- B.
In the opposite direction in which diffusion moves them.
- C.
In a direction that tends to bring about equilibrium.
- D.
Toward higher pH.
- E.
Toward higher osmotic potential.
Correct Answer
B. In the opposite direction in which diffusion moves them.Explanation
Active transport is a process that requires energy to move molecules across a cell membrane against their concentration gradient. Unlike diffusion, which moves molecules from an area of high concentration to an area of low concentration, active transport moves molecules in the opposite direction, from an area of low concentration to an area of high concentration. This allows the cell to accumulate molecules against their concentration gradient, maintaining a concentration gradient that is necessary for various cellular processes.Rate this question:
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- 14.
In the parietal cells of the stomach, the uptake of chloride ions is coupled to the transport of bicarbonate ions out of the cell. This type of transport system is called
- A.
A uniport.
- B.
A symport.
- C.
An exchange channel.
- D.
Diffusion.
- E.
An antiport.
Correct Answer
E. An antiport.Explanation
In the parietal cells of the stomach, the transport of chloride ions and bicarbonate ions occurs in opposite directions. This type of transport system, where two different ions are transported in opposite directions, is known as an antiport. It is different from a uniport, which transports only one type of molecule, and a symport, which transports two different molecules in the same direction. An exchange channel refers to a different type of transport mechanism, and diffusion is a passive process that does not involve specific transport proteins.Rate this question:
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- 15.
The only process that can bring glucose molecules into cells and does not involve the metabolic energy of ATP is
- A.
Phagocytosis.
- B.
Pinocytosis.
- C.
Active transport.
- D.
Diffusion.
- E.
Osmosis.
Correct Answer
D. Diffusion.Explanation
Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration, without the use of ATP. This movement occurs down the concentration gradient, and it does not require any metabolic energy. Phagocytosis, pinocytosis, active transport, and osmosis all involve the use of ATP or other forms of energy to transport molecules across the cell membrane. Therefore, diffusion is the only process listed that does not require ATP for the movement of glucose molecules into cells.Rate this question:
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- 16.
For each molecule of ATP consumed during active transport of swodium and potassium,
- A.
Two Na+ ions are imported and three K+ ions are exported.
- B.
Two Na+ ions are imported and one K+ ion is exported
- C.
One K+ ion is imported and three Na+ ions are exported
- D.
Two K+ ions are imported and three Na+ ions are exported
- E.
Three K+ ions are imported and two Na+ ions are exported.
Correct Answer
D. Two K+ ions are imported and three Na+ ions are exportedExplanation
During active transport of sodium and potassium, two K+ ions are imported and three Na+ ions are exported for each molecule of ATP consumed. This is because the sodium-potassium pump, which is responsible for active transport, uses ATP to pump three sodium ions out of the cell and two potassium ions into the cell. This creates an electrochemical gradient that is essential for various cellular processes, such as nerve impulse transmission and muscle contraction.Rate this question:
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- 17.
Which of the following processes does not involve the uptake of materials into the cell?
- A.
Exocytosis
- B.
P:inocytosis
- C.
Endocytosis
- D.
Receptor-mediated endocytosis
- E.
Phagocytsis
Correct Answer
A. ExocytosisExplanation
Exocytosis is the process in which materials are released from the cell. It involves the fusion of vesicles containing these materials with the cell membrane, leading to their release into the extracellular environment. In contrast, endocytosis, receptor-mediated endocytosis, pinocytosis, and phagocytosis all involve the uptake of materials into the cell. Therefore, the correct answer is Exocytosis.Rate this question:
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- 18.
Active transport differs from passive transport in that active transport
- A.
Requires energy.
- B.
Never requires direct input of ATP.
- C.
Moves molecules with a concentration gradient.
- D.
Both a and c
Correct Answer
A. Requires energy.Explanation
Active transport differs from passive transport in that it requires energy. This is because active transport moves molecules against their concentration gradient, from an area of lower concentration to an area of higher concentration. This process requires the use of energy to pump the molecules across the cell membrane. In contrast, passive transport does not require energy and moves molecules down their concentration gradient, from an area of higher concentration to an area of lower concentration. Therefore, the correct answer is that active transport requires energy.Rate this question:
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- 19.
Facilitated diffusion and active transport both
- A.
Require ATP.
- B.
Require the use of proteins as carriers
- C.
Carry solutes in only one direction
- D.
Increase without limit as the concentration gradient increases.
- E.
Depend on the solubility of the solute in lipids.
Correct Answer
B. Require the use of proteins as carriersExplanation
Facilitated diffusion and active transport both require the use of proteins as carriers. This is because both processes involve the movement of solutes across a cell membrane, which cannot occur directly due to the hydrophobic nature of the lipid bilayer. Proteins embedded in the membrane act as carriers or channels to facilitate the movement of specific solutes. In facilitated diffusion, the solutes move down their concentration gradient without the need for energy. In active transport, however, solutes are transported against their concentration gradient, requiring the input of ATP to drive the process.Rate this question:
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- 20.
The ____ of animal cells resemble the ___ of plant cells.
- A.
Tight junctions; plasma membrane
- B.
Tight junctions; plasmodesmata
- C.
Desmosomes; plasmodesmata
- D.
Gap junctions; plasma membrane
- E.
Gap junctions; plasmosdesmata
Correct Answer
E. Gap junctions; plasmosdesmata -
- 21.
Receptor-mediated endocytosis
- A.
Is non-specific.
- B.
Allows small molecules to enter cells.
- C.
Results in the formation of clathrin-coated vesicles.
- D.
Directly involves the Golgi apparatus.
- E.
Is anothher name for phagocytosis.
Correct Answer
C. Results in the formation of clathrin-coated vesicles.Explanation
Receptor-mediated endocytosis is a specific process in which specific molecules are taken up by cells. It involves the binding of ligands to specific receptors on the cell surface, which triggers the formation of clathrin-coated vesicles. These vesicles are responsible for internalizing the ligands and bringing them into the cell. This process is important for the uptake of various substances, such as hormones, growth factors, and cholesterol, and plays a crucial role in regulating cellular processes. The Golgi apparatus is not directly involved in receptor-mediated endocytosis.Rate this question:
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- 22.
The sum total of all the chemical reactions in a living structure is called its
- A.
Energetics
- B.
Activity.
- C.
Digestive power.
- D.
Entropy
- E.
Metabolism
Correct Answer
E. MetabolismExplanation
Metabolism refers to the sum total of all the chemical reactions that occur within a living structure. It includes processes such as breaking down food to obtain energy, synthesizing molecules for growth and repair, and eliminating waste products. Energetics refers to the study of energy and its transformations, but it does not encompass the entire range of chemical reactions in a living structure. Activity and digestive power are not comprehensive terms to describe all chemical reactions, while entropy refers to the measure of disorder in a system and is not specific to living structures.Rate this question:
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- 23.
Anabolic pathways are usually ____, whereas catabolic pathways are usually ____. Anabolic pathways are associated with ____ in entropy.
- A.
Endergonic; exergonic; an increase
- B.
Endergonic; exergonic; a decrease
- C.
Exergonic; endergonic; no charge
- D.
Exergonic; endergonic; an increase
- E.
Endergonic; exergonic; no change
Correct Answer
B. Endergonic; exergonic; a decreaseExplanation
Anabolic pathways are usually endergonic, meaning they require an input of energy to proceed. On the other hand, catabolic pathways are usually exergonic, meaning they release energy as they break down molecules. In terms of entropy, anabolic pathways are associated with a decrease. This is because anabolic reactions typically involve the synthesis of complex molecules, which leads to a decrease in disorder or randomness in the system.Rate this question:
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- 24.
Which of the following represents potential energy?
- A.
Chemical bonds
- B.
Concentration gradient
- C.
Electric charge imbalance
- D.
Both a and b
- E.
All of the above
Correct Answer
E. All of the aboveExplanation
All of the options listed represent potential energy. Chemical bonds store potential energy because breaking them releases energy, while forming them requires energy. Concentration gradient represents potential energy because it can be used to do work when substances move from an area of high concentration to an area of low concentration. Electric charge imbalance also represents potential energy because it can be used to do work when the charges are allowed to equalize. Therefore, all of the options mentioned in the question represent potential energy.Rate this question:
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- 25.
The first law of thermodynamics states that the total energy in the universe is
- A.
Decreasing
- B.
Increasing
- C.
Constant
- D.
Being converted to free energy
- E.
Being converted to matter
Correct Answer
C. ConstantExplanation
The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, but it can only be transferred or converted from one form to another. This means that the total energy in the universe remains constant over time. Therefore, the correct answer is "constant".Rate this question:
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- 26.
In any system, the total energy includes usable and unusable energy. The unusable energy is a measure of the disorder of the system and is referred to as
- A.
Free energy (G).
- B.
Entropy (S).
- C.
Chaos theory.
- D.
Thermodynamics.
- E.
Equilibrium.
Correct Answer
B. Entropy (S).Explanation
In any system, the total energy includes both usable and unusable energy. The unusable energy is a measure of the disorder or randomness of the system, and this measure is referred to as entropy (S). Entropy is a fundamental concept in thermodynamics and is used to quantify the amount of energy that is unavailable to do useful work. It is a measure of the system's level of disorder, with higher entropy indicating a higher degree of disorder. Therefore, the correct answer is entropy (S).Rate this question:
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- 27.
The standard free energy change for the hydrolysis of ATP to ADP +Pi is -7.3 kcal/mol. From this information one can conclude that
- A.
The reaction will never reach equilibrium.
- B.
The free energy of ADP and phosphate is higher than the free energy of ATP.
- C.
The reaction requires energy.
- D.
The reaction is endergonic.
- E.
The reaction is exergonic.
Correct Answer
E. The reaction is exergonic.Explanation
The standard free energy change for the hydrolysis of ATP to ADP + Pi is -7.3 kcal/mol. This negative value indicates that the reaction is exergonic, meaning that it releases energy. In an exergonic reaction, the products have lower free energy than the reactants. Therefore, the free energy of ADP and phosphate is lower than the free energy of ATP. Since the reaction releases energy, it does not require an input of energy and will reach equilibrium.Rate this question:
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- 28.
A readily reversible reaction, in which reactants and products have almost the same free energies, is indicated by a
- A.
Large negative (delta) G
- B.
Change in free energy.
- C.
Negative (delta) G.
- D.
(delta) G near zero.
- E.
Large positive (delta) G.
Correct Answer
D. (delta) G near zero.Explanation
A reaction with a (delta) G near zero indicates that the reactants and products have almost the same free energies. This suggests that the reaction is in equilibrium, meaning that the reaction can easily proceed in both the forward and reverse directions. In other words, the reaction is readily reversible, as indicated in the question. A large negative (delta) G would indicate that the reaction is energetically favorable in the forward direction, while a large positive (delta) G would indicate that the reaction is energetically favorable in the reverse direction.Rate this question:
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- 29.
An RNA molecule that has enzyme activity is called
- A.
RNAse.
- B.
Ribonuclease
- C.
All allosteric enzyme.
- D.
A regulatory enzyme.
- E.
A ribozyme.
Correct Answer
E. A ribozyme.Explanation
A ribozyme is an RNA molecule that has enzyme activity. Unlike most enzymes, which are made of proteins, ribozymes are made of RNA. They can catalyze specific biochemical reactions, just like protein enzymes, and play important roles in various biological processes. Therefore, a ribozyme is the correct term for an RNA molecule with enzyme activity.Rate this question:
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- 30.
Which of the following statements about enzymes is false?
- A.
An enzyme changes shape when it b inds to a substrate.
- B.
Enzymes lower the activation energy.
- C.
Enzymes are highly specific
- D.
An enzyme may orient substrates, induce strain, or temporarily add chemical groups.
- E.
Most enzymes are much smaller than their substrates.
Correct Answer
E. Most enzymes are much smaller than their substrates.Explanation
Enzymes are biological catalysts that speed up chemical reactions in the body. They do this by lowering the activation energy required for the reaction to occur. Enzymes are highly specific, meaning they only catalyze specific reactions. They can change shape when they bind to a substrate, which allows them to perform their catalytic function. Enzymes can also orient substrates, induce strain, or temporarily add chemical groups to facilitate the reaction. However, it is not true that most enzymes are smaller than their substrates. In fact, enzymes are typically larger than their substrates and have a complex three-dimensional structure that allows them to interact with the substrate and catalyze the reaction.Rate this question:
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- 31.
What is a transition state?
- A.
The place where a substrate molecule binds to an enzyme
- B.
A reactant with high potential energy
- C.
The combination of a substrate and an enzyme
- D.
The state at which the bonds of reactants are unstable
- E.
The active site where reactants are oriented.
Correct Answer
D. The state at which the bonds of reactants are unstableExplanation
A transition state refers to the state at which the bonds of reactants are unstable. During a chemical reaction, reactant molecules undergo a transition state where their bonds are in the process of breaking and forming new bonds to produce the products. This state is highly unstable and has a high potential energy. The transition state is a crucial point in a reaction as it determines the rate and outcome of the reaction.Rate this question:
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- 32.
Trypsin and elastase are both enzymes that catalyze hydrolysis of peptide bonds. But tryspsin only cuts next to lysine and elastase only cuts next to alanine. Why?
- A.
Trypsin is a protein, and elastase is not.
- B.
DG for the two reactions is different.
- C.
The shape of the active site for the two enzymes is different.
- D.
One of the reactions is endergonic and the other is exergonic.
- E.
Hydrolysis of lysine bonds requires water; hydrolysis of alanine bonds does not
Correct Answer
C. The shape of the active site for the two enzymes is different.Explanation
The shape of the active site for the two enzymes is different. This difference in shape allows trypsin to specifically bind and cut next to lysine, while elastase can only bind and cut next to alanine. The active site of an enzyme is where the substrate binds and the catalytic reaction occurs. The specific shape of the active site determines the enzyme's specificity for certain substrates. In the case of trypsin and elastase, their active sites have different shapes, leading to their different specificities for lysine and alanine, respectively.Rate this question:
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- 33.
The statement "enzymes are highly specific" means that certain
- A.
Enzymes are found in certain cells.
- B.
Reactions involving certain substrates are catalyzed by specific enzymes.
- C.
Enzymes require certain concentrations of substrates.
- D.
Reactions with certain activation energies are catalyzed by certain enzymes.
- E.
Concentration of substrates work with certain enzymes.
Correct Answer
B. Reactions involving certain substrates are catalyzed by specific enzymes.Explanation
The statement "enzymes are highly specific" means that certain reactions involving certain substrates are catalyzed by specific enzymes. Enzymes are biological catalysts that speed up chemical reactions in living organisms. They have a unique three-dimensional structure that allows them to bind to specific substrates, or reactant molecules, and convert them into products. This specificity ensures that enzymes only catalyze specific reactions and do not interfere with other biochemical processes. Therefore, the correct answer is that reactions involving certain substrates are catalyzed by specific enzymes.Rate this question:
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- 34.
An active site is
- A.
The part of the substrate that binds with an enzyme.
- B.
The part of the enzyme that binds with a substrate.
- C.
The site where energy is added to an enzyme catalyst.
- D.
The site where enzymes are found in cells.
- E.
None of these.
Correct Answer
B. The part of the enzyme that binds with a substrate.Explanation
The active site of an enzyme is the specific region where the substrate binds and undergoes a chemical reaction. It is a highly specific and complementary shape to the substrate molecule. This binding is essential for the enzyme to catalyze the reaction, as it brings the substrate molecules together in the correct orientation and provides the necessary conditions for the reaction to occur. Therefore, the correct answer is "the part of the enzyme that binds with a substrate."Rate this question:
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- 35.
The molecules that are acted on by an enzyme are called
- A.
Products.
- B.
Substrates.
- C.
Carriers.
- D.
Prosthetics.
- E.
Effectors.
Correct Answer
B. Substrates.Explanation
Enzymes are catalysts that facilitate chemical reactions in living organisms. They bind to specific molecules, called substrates, and convert them into different molecules, known as products. Therefore, the correct answer is substrates, as these are the molecules that are acted on by an enzyme. The other options, such as carriers, prosthetics, and effectors, do not accurately describe the molecules that are acted on by an enzyme.Rate this question:
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- 36.
The enzyme sucrase increases the rate at which sucrose is broken down into glucose and fructose. Sucrase works by
- A.
Increasing the amount of free energy of the reaction.
- B.
Lowering the activation energy of the reaction.
- C.
Decreasing the equilibrium constant of the reaction.
- D.
Supplying energy to speed up the reaction.
- E.
Changing the shape of the active site.
Correct Answer
B. Lowering the activation energy of the reaction.Explanation
Sucrase works by lowering the activation energy of the reaction. Activation energy is the energy required to initiate a chemical reaction. By lowering the activation energy, sucrase makes it easier for the reaction to occur, thus increasing the rate at which sucrose is broken down into glucose and fructose. This allows the reaction to happen more quickly and efficiently.Rate this question:
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- 37.
Which of the followig statements about enzymes is true?
- A.
Enzymes are proteins.
- B.
Enzymes have a specific amino acid sequence.
- C.
Enzymes are highly specific.
- D.
Enzymes lower the energy barrier.
- E.
All of the above.
Correct Answer
E. All of the above.Explanation
All of the statements about enzymes are true. Enzymes are proteins, which means they are made up of amino acids. Enzymes have a specific amino acid sequence that determines their structure and function. Enzymes are highly specific, meaning they can only catalyze specific chemical reactions. Additionally, enzymes lower the energy barrier, or activation energy, required for a chemical reaction to occur. Therefore, the correct answer is "All of the above."Rate this question:
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- 38.
The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction glyceraldehyde 3-phosphate to 1,3-diphosphoglycerate. The binding of the glyceraldehyde 3-phosphate to the enzyme creates a(n)
- A.
Transition state.
- B.
Aactivations groove.
- C.
Catalyst.
- D.
Enzyme-substrate complex.
- E.
Energy barrier.
Correct Answer
D. Enzyme-substrate complex.Explanation
The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction between glyceraldehyde 3-phosphate and 1,3-diphosphoglycerate. When the glyceraldehyde 3-phosphate binds to the enzyme, it forms an enzyme-substrate complex. This complex is a temporary association where the enzyme and the substrate are bound together. In this complex, the enzyme facilitates the conversion of the substrate to the product. Therefore, the correct answer is enzyme-substrate complex.Rate this question:
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- 39.
The enzyme glucose oxidase binds the six-carbon sugar glucose and catalyzes its conversion to glucono - 1,4-actone. Mannose is also a six-carbon sugar, but glucose oxidase cannot bind mannose. The specificity of glucose oxidase is based on the
- A.
Freee energy of the transition state.
- B.
Activation energy of the reaction.
- C.
Change in free energy of the reaction.
- D.
Three-dimensional shape and structure of the active site.
- E.
Rate constatn of the reaction.
Correct Answer
D. Three-dimensional shape and structure of the active site.Explanation
The specificity of glucose oxidase is based on the three-dimensional shape and structure of the active site. The active site of an enzyme is a region where the substrate binds and undergoes a chemical reaction. In this case, glucose oxidase has a specific active site that is complementary in shape and structure to glucose, allowing it to bind and catalyze its conversion to glucono - 1,4-actone. However, the active site is not compatible with mannose, preventing glucose oxidase from binding and catalyzing its conversion. This demonstrates the importance of the three-dimensional shape and structure of the active site in determining enzyme specificity.Rate this question:
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- 40.
Enzymes catalyze a reaction by ___
- A.
Orienting
- B.
Inducing strain in
- C.
Adding chemical groups to
- D.
Adding charges to
- E.
All of the above
Correct Answer
E. All of the aboveExplanation
Enzymes catalyze a reaction by orienting the reactants in a favorable position, inducing strain in the reactant molecules to facilitate the reaction, adding chemical groups to the reactants to enhance their reactivity, and adding charges to the reactants to stabilize the transition state. Therefore, all of the above options are correct explanations for how enzymes catalyze a reaction.Rate this question:
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- 41.
The ability of an enzyme to change shape when it binds to its substrate is called
- A.
Induced fit.
- B.
Enzyme flex.
- C.
The lock and key paradox
- D.
Substrate-induced active site shaping.
- E.
Enzyme retrofit.
Correct Answer
A. Induced fit.Explanation
The ability of an enzyme to change its shape when it binds to its substrate is known as induced fit. This phenomenon allows the enzyme to better accommodate and interact with the substrate, enhancing the efficiency of the catalytic reaction. The enzyme undergoes conformational changes upon substrate binding, resulting in a tighter fit between the two molecules and facilitating the chemical reaction. This induced fit mechanism ensures that the enzyme specifically recognizes and acts upon its substrate, contributing to the specificity and effectiveness of enzymatic reactions.Rate this question:
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- 42.
Many enzymes require ATP and ADP for a reaction to occur. They temporarily bind to and then release from the substrate to participate in other reactions. ATP and ADP are considered
- A.
A side chain
- B.
Coenzymes
- C.
A coupled reaction.
- D.
A prosthetic group.
- E.
Cofactors.
Correct Answer
B. CoenzymesExplanation
Enzymes are biological catalysts that facilitate chemical reactions in the body. Many enzymes require ATP (adenosine triphosphate) and ADP (adenosine diphosphate) to carry out their functions. ATP and ADP act as coenzymes, which means they temporarily bind to the enzyme and then release from the substrate to participate in other reactions. Coenzymes work alongside enzymes to enhance their activity and are essential for the proper functioning of many metabolic processes. Therefore, the correct answer is coenzymes.Rate this question:
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- 43.
The rates of enzymatic reactions eventually become saturated as substrate concentration increases because
- A.
Enzymes have the maximum possible number of hydrogen atoms attached to them.
- B.
The concentration of substrate reaches a point at which it cannot increase any further.
- C.
Substrates are inhibitors of enzymes.
- D.
The activation energy of the reaction reaches a point at which it cannot be lowered further.
- E.
There are a limited number of the enzyme molecules present.
Correct Answer
E. There are a limited number of the enzyme molecules present.Explanation
The correct answer is that there are a limited number of enzyme molecules present. As substrate concentration increases, the rate of enzymatic reactions initially increases because more substrate molecules are available to bind with the enzymes. However, at a certain point, all of the enzyme molecules become occupied by substrate molecules, and adding more substrate does not increase the reaction rate further. This is because there is a limited number of enzyme molecules available to catalyze the reaction, and once all of them are bound to substrate, the reaction rate becomes saturated.Rate this question:
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- 44.
How do competitive and noncompetitive enzyme inhibitors differ?
- A.
Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site.
- B.
Competitive inhibitors have a higher energy of activation than noncompetitive inhibitors have.
- C.
They function at different pH values.
- D.
Noncompetitive enzyme inhibitors contain magnesium, whereas competitive inhibitors contain iron.
- E.
Noncompetitive enzyme inhibitors are reversible, whereas competitive inhibitors are irreversible.
Correct Answer
A. Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site.Explanation
Competitive inhibitors and noncompetitive inhibitors differ in their mechanism of action. Competitive inhibitors bind to the active site of the enzyme, competing with the substrate for binding. This prevents the substrate from binding and reduces the enzyme's activity. On the other hand, noncompetitive inhibitors bind to a different site on the enzyme, causing a conformational change in the active site. This change makes the active site less effective in catalyzing the reaction. Therefore, competitive inhibitors directly interfere with substrate binding, while noncompetitive inhibitors indirectly affect the enzyme's activity by altering its shape.Rate this question:
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- 45.
Enzymes are sensitive to
- A.
Temperature.
- B.
PH
- C.
Irreversible inhibitors such as DIPF.
- D.
Allosteric effectors.
- E.
All of the above
Correct Answer
E. All of the aboveExplanation
Enzymes are sensitive to temperature, pH, irreversible inhibitors such as DIPF, and allosteric effectors. Temperature affects the rate of enzyme-catalyzed reactions, with higher temperatures generally increasing the reaction rate until a certain point where the enzyme denatures. pH also plays a crucial role in enzyme activity, as each enzyme has an optimal pH range in which it functions most effectively. Irreversible inhibitors like DIPF permanently bind to the enzyme, rendering it inactive. Allosteric effectors can either enhance or inhibit enzyme activity by binding to specific sites on the enzyme, causing a conformational change. Therefore, all of these factors can significantly impact enzyme function.Rate this question:
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- 46.
An allosteric inhibitor
- A.
Decreases the concentration of an inactive enzyme.
- B.
Changes the shape of an enzyme.
- C.
Increases the concentration of a product.
- D.
Changes the shape of substratye
- E.
Increases the concentration of an enzyme-substrate complex.
Correct Answer
B. Changes the shape of an enzyme.Explanation
An allosteric inhibitor is a molecule that binds to an enzyme at a site other than the active site, causing a conformational change in the enzyme's shape. This change in shape can result in the enzyme becoming less active or completely inactive. By altering the enzyme's shape, the allosteric inhibitor prevents the enzyme from effectively binding to its substrate and carrying out its catalytic function. Therefore, the correct answer is that an allosteric inhibitor changes the shape of an enzyme.Rate this question:
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- 47.
The process that involves an end product acting as an inhibitor of an earlier step in a metabolic pathway is called
- A.
Feedback activation
- B.
Feedback inhibition
- C.
Positive feedback
- D.
Concerted activation
- E.
Competitive inhibition
Correct Answer
B. Feedback inhibitionExplanation
Feedback inhibition is the correct answer because it refers to the process in which the end product of a metabolic pathway acts as an inhibitor of an earlier step in the pathway. This mechanism helps regulate the production of the end product by preventing excessive accumulation. When the concentration of the end product reaches a certain level, it binds to and inhibits an enzyme involved in an earlier step, effectively slowing down or stopping the pathway. This negative feedback loop helps maintain homeostasis and balance in metabolic processes.Rate this question:
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- 48.
Denatured enzymes are the same as
- A.
Ribozymes
- B.
Abzymes
- C.
Isozymes
- D.
Enzymes that can no longer function.
- E.
Coenzymes
Correct Answer
D. Enzymes that can no longer function.Explanation
Denatured enzymes are enzymes that have undergone a structural change, usually due to extreme conditions such as high temperature or pH. This structural change disrupts the enzyme's active site, rendering it unable to catalyze chemical reactions effectively or at all. Therefore, denatured enzymes can no longer function properly.Rate this question:
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- 49.
Denatured enzymes are the same as
- A.
Ribozymes
- B.
Abzymes
- C.
Isozymes
- D.
Enzymes that can no longer function
- E.
Coenzymes
Correct Answer
D. Enzymes that can no longer functionExplanation
Denatured enzymes are enzymes that have undergone a change in their structure, usually due to high temperature or extreme pH conditions. This structural change disrupts the enzyme's active site, rendering it unable to bind to its substrate and catalyze a reaction. Therefore, denatured enzymes can no longer function properly and their catalytic activity is lost.Rate this question:
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- 50.
When organisms move from one environment to another, they sometimes syntehsize variations of existing enzymes which are called
- A.
Coenzymes.
- B.
Abzymes.
- C.
Isozymes.
- D.
Effectors.
- E.
Activators.
Correct Answer
C. Isozymes.Explanation
When organisms move from one environment to another, they may encounter different conditions that require specific adaptations. One way organisms can adapt is by synthesizing variations of existing enzymes, known as isozymes. These isozymes have similar functions but slightly different structures, allowing them to perform optimally in the new environment. Coenzymes, on the other hand, are small molecules that assist enzymes in their catalytic activities. Abzymes are antibodies with catalytic activity, effectors are molecules that regulate enzyme activity, and activators are molecules that enhance enzyme activity.Rate this question:
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