Cell Metabolism - Practice Questions
What factors influence enzyme activity?
- temperature - pH - concentration of substrate
What is the net production of ATP, pyruvate, and NADH when one molecule of glucose undergoes glycolysis? A) 2 ATP, 2 NADH, and 2 pyruvate B) 4 ATP, 1 NADH, 2 pyruvate C) 4 ATP, 2 NADH, and 4 pyruvate D) 2 ATP, 1 NADH, and 1 pyruvate
2 ATP, 2 NADH, and 2 pyruvate
Identify each of the following molecules as either a reactant or a product of cellular respiration. A) C6H12O6 (glucose) B) H2O (water) C) CO2 (carbon dioxide) D) O2 (oxygen) E) ATP
A) reactant B) product C) product D) reactant E) product
Identify each of the following molecules as reactants or products of the Krebs cycle. A) Acetyl CoA B) Carbon dioxide C) NAD+ D) NADH E) FADH2 F) FAD
A) reactant B) product C) reactant D) product E) product F) reactant
Which of the following molecules is used as "energy currency" for the cell? A) ATP B) Water C) ADP D) Phosphate group
ATP ATP is a small, relatively simple molecule that is used as the main "energy currency" of the cell. The energy release by the breakdown of ATP is used to power many cellular reactions.
Which of the following correctly describes the structure of ATP and how it provides energy? A) ATP contains a 5-carbon sugar, three phosphate groups, and an adenine base. Energy is released when the bond between the adenine base and the sugar is broken. B) ATP contains a 6-carbon sugar, two phosphate groups, and an adenine base. Energy is released when a single phosphate group is added to the existing two phosphate groups. C) ATP contains a 6-carbon sugar, three phosphate groups, and an adenine base. Energy is released when bonds within the 6-carbon molecule are broken. D) ATP contains a 5-carbon sugar, three phosphate groups, and an adenine base. Energy is released when the bond between the second phosphate group and third phosphate group is broken.
ATP is made of a 5-carbon sugar (ribose), three phosphate groups, and an adenine base. The phosphate groups are negatively charged, making the bonds between them unstable. When the bond between the second and third phosphate group breaks, energy is released.
After glycolysis, pyruvate is oxidized to produce carbon dioxide, NADH, and a molecule that contains 2 of the 3 carbons from the pyruvate. Which product of pyruvate oxidation enters the Krebs cycle? A) Glucose B) Carbon dioxide C) NADH D) Acetyl-CoA
Acetyl-CoA acts as the fuel for the Krebs cycle during cellular respiration. The coenzyme A helps activate the acetyl group, preparing it to undergo the necessary reactions to enter the Krebs cycle.
What is the difference between anabolic and catabolic pathways?
Anabolic pathways, which build larger molecules from smaller molecules, require energy. This energy is provided by catabolic pathways, which break down complex molecules into simpler ones, releasing energy.
Which of the following are roles of amino acids at an enzyme's active site? A) Preventing the substrate from entering the chemical reaction B) Changing the enzyme itself C) Converting the enzyme to receive a different substrate D) Binding the substrate to the enzyme
Binding the substrate to the enzymeThe active site of an enzyme is the part of the enzyme where the substrate binds.
How do competitive inhibitors operate in comparison to noncompetitive inhibitors?
Competitive inhibitors occupy the active site of an enzyme so nothing else can bind to it. Noncompetitive inhibitors do not compete with a substrate, instead they bind to the allosteric site which changes the shape of the enzyme so that the proper substrates cannot bind properly.
Why does a chemical require increased activation energy without an enzyme as a biological catalyst?
Disrupting the electron configuration requires energy, which is energy added to the system known as activation energy. This ordinarily comes from collisions of molecules. The molecules must be oriented properly and collide with sufficient force to disrupt the electron configuration. Enzymes lower the activation energy by holding the reactants in exactly the correct orientation.
What is the main transformation that occurs during glycolysis? A) Glycolysis produces CO2, NAD, and pyruvate by oxidizing glucose. B) Glycolysis produces ATP, pyruvate, and NADH by oxidizing glucose. C) Glycolysis produces pyruvate and ATP through by oxidizing glucose and NAD+. D) Glycolysis produces ATP through the process of oxidative phosphorylation.
Glycolysis produces ATP, pyruvate, and NADH by oxidizing glucose. During glycolysis, a single glucose molecule is broken down into two pyruvate molecules. As a result of this process, NADH and ATP are also produced.
In what part of the cell does glycolysis take place? A) Cytoplasm (cytosol) B) Mitochondria C) Ribosome D) Nucleus
Glycolysis takes place in the cytoplasm (cytosol) of the cell.
Which of the following statements is true regarding anabolism? A) Energy is released during anabolic reactions. B) In anabolism, larger molecules are made from smaller molecules. C) Anabolism uses the process of hydrolysis to join molecules together. D) Anabolism is the sum of all the chemical reactions in a cell.
In anabolism, larger molecules are made from smaller molecules. Anabolic processes build complex molecules from simpler ones. An example of this is the building of polysaccharides from simple sugars.
What is true of a competitive inhibitor? A) It has a structure similar to the substrate. B) It has the same mass as the substrate. C) It forms the same products as the substrate. D) It binds with the enzyme in a place other than the active site.
It has a structure similar to the substrate. Competitive inhibitors "compete" with the substrate for the active site. They bind to an enzyme's active site and block the substrate from attaching.
A+B+energy⟶AB Which of the following best describes the above reaction? A) It is a catabolic reaction. B) It is a hydrolysis reaction. C) It is an anabolic reaction. D) It is an exergonic reaction.
It is an anabolic reaction. This reaction is anabolic, since it consumes energy to build a more complex molecule from simpler molecules.
How does an enzyme affect the rate of a reaction? A) It lowers the activation energy of the reaction, decreasing the reaction rate. B) It lowers the activation energy of the reaction, increasing the reaction rate. C) It raises the activation energy of the reaction, decreasing the reaction rate. D) It raises the activation energy of the reaction, increasing the reaction rate.
It lowers the activation energy of the reaction, increasing the reaction rate. Enzymes lower activation energy of a reaction, decreasing the amount of energy required to start the reaction. This allows the reaction to occur faster than it would without the enzyme.
Pepstatin binds to the enzyme pepsin. The substrate is still able to bind to the active site, but the reaction is blocked. What is this an example of? A) Noncompetitive inhibition B) Competitive inhibition C) Compartmentalization D) Allosteric activation
Noncompetitive inhibition Pepstatin binds to the enzyme and blocks the reaction, but the substrate is still able to bind to the active site. It is "noncompetitive" because the both pepstatin and the substrate can be bound at the same time.
Which statement is true regarding catabolic pathways? A) Polymers are broken down into their monomers. B) Catabolic reactions consume energy. C) Molecules are synthesized using dehydration synthesis. D) Catabolic pathways are used to construct macromolecules such as carbohydrates, lipids, and proteins.
Polymers are broken down into their monomers.Catabolic pathways break down polymers (or larger molecules) into monomers (simple units). An example of a catabolic pathway is cellular respiration, which breaks down glucose to make energy for the cell.
Which 3-carbon molecule is one of the final products of glycolysis? A) 2-Phosphoglycerate B) Pyruvate C) ADP D) Glucose
Pyruvate Overall, glycolysis converts one 6-carbon molecule of glucose into two 3-carbon molecules of pyruvate.
Which of the following are components of adenosine triphospate (ATP)? A) Ribose, an adenine base, and a triphosphate group. B) Deoxyribose, a cytosine base, and a triphosphate group C) Deoxyribose, an adenine base, and a triphosphate group D) Ribose, a cytosine base, and a triphosphate group
Ribose, an adenine base, and a triphosphate group. ATP is a molecule made of a ribose sugar, an adenine base, and a chain of three phosphate groups (triphosphate).
In what part of the cell does the Krebs cycle take place? A) Chloroplast B) Mitochondria C) Cytoplasm (cytosol) D) Ribosome
The Krebs cycle takes place in the inner space of the mitochondria.
Which statement is true of enzymes? A) Enzymes work independent of substrate concentration. B) The activity of an enzyme might change as pH changes. C) Changes in temperature do not affect enzymes. D) Enzymes are non-specific.
The activity of an enzyme might change as pH changes. Enzymes work best within a certain pH range, and, as with temperature, extreme pH values (acidic or basic) can make enzymes denature.
Cellular respiration is a type of oxidation-reduction (redox) reaction. What is getting oxidized and reduced during cellular respiration? A) Both the carbon atoms in glucose and oxygen are reduced. B) Both the carbon atoms in glucose and oxygen are oxidized. C) The carbon atoms in glucose are oxidized, and oxygen is reduced. D) The carbon atoms in glucose are reduced, and oxygen is oxidized.
The carbon atoms in glucose are oxidized, and oxygen is reduced. In cellular respiration, the carbon atoms in glucose are oxidized because they lose H atoms. Oxygen is reduced because it gains H atoms.
How does the enzyme-substrate complex lower the activation energy of the reaction?
The enzyme orients the substrate into a position that increases the probability of a reaction, which enables the collisions to be more effective.
Which of the following is true regarding the yield of ATP during aerobic cellular respiration? A) The theoretical yield of ATP from aerobic cellular respiration is 30 ATP, but often the actual yield is much higher. B) Aerobic cellular respiration always yields 38 ATP once the process has completed. C) It is impossible to determine the theoretical yield of ATP from aerobic respiration. D) The theoretical yield of ATP from aerobic cellular respiration is 38 ATP, but often times the actual yield is lower.
The theoretical yield of ATP from aerobic cellular respiration is 38 ATP, but often times the actual yield is lower. Depending on the cell's efficiency, the actual yield of ATP from aerobic respiration may be closer to 30 ATP due to energy losses.
How do noncompetitive inhibitors interact with enzymes? A) They bind to a location other than the active site, stopping the enzyme from functioning. B) They bind to the active site, preventing the substrate from binding. C) They bind to a location other than the active site, enhancing the enzyme's activity. D) They bind to the active site, causing more substrate to bind.
They bind to a location other than the active site, stopping the enzyme from functioning. Noncompetitive inhibitors attach at a site other than the active site, blocking the enzyme from doing its job. They are "noncompetitive" because the inhibitor and substrate can both be bound at the same time.
What is the primary function of cofactors? A) To aid in enzyme function B) To synthesize enzymes C) To inhibit enzymes D) To break down old enzymes
To aid in enzyme function Most enzymes do not function optimally, or even at all, unless bound to other non-protein helper molecules called cofactors.
How does ATP provide the energy for synthesis?
When complex molecules are catabolized, some of the energy is transferred to and trapped in ATP, and releases it to drive anabolic reactions