bio unit 2

In a comparison of NAD+ (NAD) and NADH, which of these combinations is true?
A. NAD+ is more reduced and has higher free energy
B. NAD+ is more reduced and has lower free energy
C. NAD+ is more oxidized and has higher free energy
D. NAD+ is more oxidized and has lower free energy

D

The direct product of glycolysis reactions must be converted to which molecule before it can enter the Krebs Citric Acid Cycle?
A. Acetyl (2C)
B. Citric acid (6C)
C. Glucose
D. NAD+
E. Pyruvate (3C)

A

What is the function of fermentation reactions that use pyruvate?
A. To produce more ATP after glycolysis
B. To convert pyruvate to a molecule that can be used in the Citric Acid Cycle
C. To produce oxidized NAD
D. To produce reduced NAD
E. To produce ethanol and lactic acid for use in the cell

C

To produce the ATP they need, yeast cells can conduct either aerobic or anaerobic respiration (glycolysis & fermentation) using glucose as fuel. What would be a difference under the two conditions?
A. a greater rate of sugar consumed in aerobic respiration
B. a greater rate of fats consumed in aerobic respiration
C. a greater rate of sugar consumed in anaerobic respiration
D. a greater rate of fats consumed in anaerobic respiration

C

The main oxidized product released from the Krebs Citric acid cycle is ______; while a major reduced product of that set of reactions is ______.
A. ATP ; NAD
B. CO2 ; NAD
C. NAD+ ; NADH
D. CO2 ; NADH
E. CO2 ; ATP

D

When there is no O2 present, the Krebs Citric Acid Cycle stops. What is the immediate reason this reaction cycle stops when there is no O2?
A. a reactant within the Citric Acid Cycle is the final electron acceptor in the ETC
B. a product of the Citric Cycle is the final electron acceptor in the ETC
C. a reaction step in the Citric Acid Cycle uses/requires O2
D. a reaction step in the Citric Acid Cycle uses/requires oxidized NAD

D

The energy from the hydrocarbon chain of fats enters cellular respiration as what molecule and at what point?
A. as glucose, in Glycolysis
B. as acetyl, in Citric Acid Cycle
C. as pyruvate, in Citric Acid Cycle
D. as NADH, in Electron transport chain

B

Oxygen molecules (O2) are used directly in which part of cellular respiration?
A. Glycolysis
B. Citric acid cycle
C. Electron transport chain
D. Fermentation of pyruvate to lactate or ethanol
E. O2 is used directly in more than one of the above

C

Which of these provides the energy to build up a high concentration of H+ ions (proton gradient) between inner and outer mitochondrial membranes?
A. energy released from ATP hydrolysis
B. energy from heat in the mitochondria
C. energy released as NAD gets reduced to NADH
D. energy released as electrons flow down the electron transport chain

D

In eukaryotic cells, the enzymes controlling reactions of glycolysis are located ______; while the enzymes controlling reactions of the Krebs Citric acid cycle are located _______.
A. in the cytosol (cytoplasm); in the cytosol
B. in the cytosol ; in the mitochondrial matrix
C. in the cytosol ; embedded in the inner mitochondrial membrane
D. in the cytosol ; in the space between the inner and outer mitochondrial membranes
E. in the mitochondrial matrix ; in the cytosol
F. in the mitochondrial matrix ; embedded in the inner mitochondrial membrane
G. in the mitochondrial matrix ; in the space between the inner and outer mitochondrial membranes

B

The source of energy that directly drives the synthesis of ATP during oxidative phosphorylation is which one of these?
A. the oxidation of glucose and other fuels
B. the flow of electrons down the ETC;
C. transfer of phosphate from an organic substrate onto ADP
D. movement of protons due to the H+ concentration gradient

D

Cells can ONLY metabolize the products made from beta oxidation of fat hydrocarbons under which of these conditions?
A. In the total absence of pyruvate in the cell
B. in the presence of O2 in the cell
C. In the absence of ATP in the cell
D in the presence of NADH and FADH2 in the cell

B

During oxidation of pyruvate (a 3-carbon molecule) in conversion to acetyl (a 2-carbon molecule), a molecule of CO2 is formed and released. What else is formed and released, in a redox-coupled reaction at that step?
A. O2
B. ATP
C. NAD
D. NADH

D

Most of the carbon dioxide that we breathe out is formed in
A. Electron transport chain
B. Glycolysis
C. Citric acid cycle
D. ATP synthase

C

What is the final electron acceptor in the electron transport chain in mitochondria?
A. O2
B. CO2
C. ATP
D. NAD
E. NADH

A

What is the evolved function of the processes collectively known as cellular respiration?
A. to make CO2
B. to make H2O
C. to make ATP
D. to make NAD

C

Which describes the roles of NAD(ox) and NADH(re) in glycolysis?
A. NAD is used up in glycolysis
B. NADH is used up in glycolysis
C. NAD is formed in glycolysis
D. NADH is formed in glycolysis
E. A and D are true
F. B and C are true

E

Which metabolic pathway is common to both fermentation and aerobic respiration of a glucose molecule?
A. Citric acid cycle (Krebs cycle)
B. Electron transport chain
C. Glycolysis
D. Reduction of pyruvate to lactate

C

When a muscle becomes anaerobic during strenuous exercise and temporary low O2, why must cells convert pyruvate to lactate? (In other words, what is the function of lactic acid fermentation pathways?)
A. to decrease NAD+ and increase NADH
B.to decrease NADH and increase NAD+
C. to produce more ATP from pyruvate
D. to use up more ATP after pyruvate
E. . to keep oxidative phosphorylation running

B

The enzyme PFK (a kinase) catalyzes a key reaction early in glycolysis, leading to the production of more ATP. PFK is allosterically inhibited by ATP. This is an example of which?
A. Competitive inhibition control
B. End product feedback control
C. A kinase being inhibited by another kinase
D. Kinase action being controlled by phosphatase

B

In the cellular respiration of glucose, which of these processes produce the most ATP per glucose?
A. Citric Acid (Krebs) cycle
B. ETC and ATP synthase
C. Glycolysis
D. Fermentation
E. Pyruvate oxidation to acetyl

B

Which is true about the relative production of ATP and NADH from carbohydrates in glycolysis and citric acid cycle (=Krebs Cycle)?
A. Citric acid cycle produces much more ATP per glucose than glycolysis does
B. Glycolysis produces much more ATP per glucose than citric acid cycle does
C. Citric acid cycle produces much more reduced NADH per glucose than glycolysis does
D. Glycolysis produces much more reduced NADH per glucose than citric acid cycle does

C

According to the second law of thermodynamics, when a reaction occurs (within a closed system) which of these tends to happen?
A. energy is destroyed
B. energy changes form
C. enthalpy H increases
D. entropy S increases

D

Which of these states is associated with greater free energy, that is, greater capacity to do work?
A. high entropy (S)
B. high enthalpy (H)
C. more stability
D. more randomness
E. two of these

B

If the delta G of ATP hydrolysis is -7.3 kcal/mol, then ATP hydrolysis can be energy-coupled with and drive forward reactions having which of the following values of delta G?
A. + 5.3 kcal/mol
B. + 7.3 kcal/mol
C. + 9.3 kcal/mol
D. A or B but not C
E. A or B or C

A

Which of the following statements about enzymes is FALSE?
A. enzymes do not affect equilibrium point of reactions
B. enzymes lower the activation energy of a reaction
C. enzymes convert endergonic reactions to exergonic reactions
D. enzymes are highly specific

C

A ball at the bottom of the hill has lower free energy than the same ball at the top of a hill because:
A. It has greater capacity to do work
B. It is less stable
C. It is endergonic
D. It contains less chemical bond energy
E. It has higher entropy

E

ATP hydrolysis (releasing a phosphate) is exergonic. Which of these names an endergonic process that must be driven by (i.e., energy-coupled with) ATP breakdown and the protein that does the coupling?
A. flow of sodium ions through passive ion channel protein
B. movement of H+ ions from low to high concentration through proton pump protein
C. movement of sugar from low to high concentration through co-transport protein
D. flow of water molecules through an aquaporin
E. more than one of these is an example of ATP breakdown coupling

B

Many cell functions that are done by proteins rely on the protein’s capacity to change shape slightly. What aspect of protein structure permits that?
A. their capacity to be denatured at high heat
B. their capacity to bind to other macromolecules in the cell
C. the fact that weak bonds between R groups hold their structure
D. the fact that peptide bonds link the amino acids together

C

When an enzyme’s function is to catalyze two reactions at once, one an exergonic reaction and one an endergonic reaction, the two reactions are said to be
A. substrates
B. non-spontaneous
C. kinetic
D. activated
E. energy-coupled

E

The statement “Enzymes are highly specific” means certain
A. enzymes are found in certain cells
B. enzymes catalyze reactions with certain substrates
C. enzymes require certain concentrations of substrates
D. reactions with certain activation energy levels are catalyzed by certain enzymes
E. enzymes can catalyze many different reactions, one at a time

B

Since most biological enzymes are proteins, which is the best explanation for how an enzyme can work only on specific reactions?
A. it has a specific overall size
B. it consists of only one specific amino acid.
C. its active site has a specific shape and polarity
D its active site has a specific volume
E. it only works with specific inhibitors

C

Competitive inhibitors of enzymes work by
A. fitting into the active site
B. fitting into a site other than the active site
C. altering the shape of the enzyme
D. changing the enzyme into an inactive form
E. increasing the activation energy of the enzyme-catalyzed reaction

A

In what way can enzymes lower the activation energy and speed up reactions?
A. By adding heat energy into the reaction
B. By being used up in the reaction
C. By holding two substrates close together in the active
D. By changing endergonic reactions to exergonic reactions
E. By allosteric inhibition or activation

C

Some bacteria are metabolically active in hot springs because
A. they are able to maintain a lower internal temperature
B. high temperatures make catalysts unnecessary
C. their enzymes have high optimal temperature
D. their enzymes are completely insensitive to temperature

C

Feedback inhibition works to control the rate of an enzyme-catalyzed reaction sequence in which way?
A. The product of the first reaction in the pathway binds to and inhibits the enzyme that produced it
B. The product of the first reaction in the pathway binds to and inhibits the last enzyme in the pathway
C. The end product of the pathway binds to and inhibits the enzyme that produced it
D. The end product of the pathway binds to and inhibits the first enzyme in the pathway
E. The last enzyme in the pathway binds to and inhibits the first enzyme in the pathway

D

When a molecule becomes oxidized in a chemical reaction, which of the following is true, by definition?
A. it gains electrons
B. it loses electrons
C. it gains H+ ions
D. it loses H+ ions

B

NAD+ is a dinucleotide coenzyme that is important in cellular respiration. It is (becomes) _______ when gaining electrons and then is (becomes) _______ when it loses electrons.
A. oxidized . . . reduced
B. reduced . . . oxidized
C. oxidized . . . energized
D. reduced . . . energized

B

Which one of these states has higher free energy?
A. high entropy
B. high enthalpy
C. high randomness
D. high stability

B

Which of these is an example of an “energy-coupled” reaction?
A. Exergonic glucose breakdown driven by endergonic ATP synthesis
B. Exergonic ATP breakdown driven by endergonic ATP synthesis
C. Endergonic protein synthesis driven by exergonic ATP breakdown

C

In comparison to the Reactants, the Transition state is:
A. more stable and has lower free energy
B. less stable and has higher free energy

B

In what way can enzymes lower the activation energy and speed up reactions?
A. By adding heat energy into the reaction
B. By the enzyme molecule being used up in the reaction
C. By binding two substrates close together in the active site

C

Which of the following factors would tend to increase animal cell membrane fluidity at cooler temperatures?
A. greater proportion of saturated phospholipids in the membrane
B. relatively high abundance of cholesterol in the membrane
C. relatively high abundance of aquaporins in the membrane
D. none of these would affect membrane fluidity

B

How do unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing tightly together.
B) Unsaturated fatty acids have a higher cholesterol content that prevents adjacent lipids from packing tightly together.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds result in shorter fatty acid tails and therefore thinner membranes.

A

Which of the following can move through the phospholipid bilayer portion of a membrane without requiring a transport protein?
A. potassium ion
B. glucose
C . O2
D. a fatty acid molecule
E. two of these
F. all three of these

E

Which of the following processes includes all the others?
A. osmosis
B. diffusion of a solute across a membrane
C. passive transport
D. transport of an ion down its electrochemical gradient

C

Which of the following describes the action of the sodium-potassium pump with respect to concentration gradients?
A. transports Na+ ions against their gradient and K+ ions down their gradient
B. transports K+ ions against their gradient and Na+ ions down their gradient
C. transports both Na+ ions and K+ ions down their gradients
D. transports both Na+ ions and K+ ions against their gradients

D

Which of these gradients, by itself, could influence the net direction of K+ movement across the membrane through passive K+ ion channels?
A. a sucrose gradient
B. a solute gradient
C. an electrical charge gradient
D. an ATP gradient

C

A Na+ ion gradient across the membrane has the capacity to do work because:
A. the gradient can use ATP to diffuse more Na+ ions across the membrane
B. the gradient can power the sodium-potassium pump to transport Na+ ions
C. Na+ ions will spontaneously move to equal concentrations

C

When a neuron begins an action potential, the membrane is depolarized and the inside of the cell, usually negative, briefly becomes more positive. Which ion event explains this depolarization in the action potential?
A. K+ ions leave the cell
B. Na+ ions enter the cell
C. Cl- ions enter the cell
D. action of the sodium-potassium pump

B

Sodium ions (Na+) are more concentrated on the outside of a neuron cell. Which of the following builds this sodium ion gradient?
A. flow of Na+ through passive channels
B. flow of water across the membrane
C. action of Na+/glucose co-transporters
D. action of the sodium-potassium pump

D

Plant cells have many H+/sucrose co-transporters that move the two substances into cells. What would be the effect on co-transport rate when the H+ concentration just outside the cell membrane increases?
A. decrease in transport of sucrose into the cell
B. increase in transport of sucrose into the cell
C. increase in the rate of ATP use for transport
D. increase in the rate of water movement out of the cell

B

Oral rehydration therapy helps treat patients who are dehydrated. Why does the fluid given contain more than just plain water?
A. patients need the sugar in the fluid for a source of energy
B. adding solutes will provide ATP for active pumping of water across the gut cell membrane
C. adding solutes that are easily absorbed into gut cells increases uptake of water into those cells

C

ATP, the energy currency molecule, is a modified form of the monomer from which of these four groups of biomolecules?
A. carbohydrates
B. lipids
C. nucleic acids
D. proteins

C

Phosphatase enzymes in signal transduction pathways function primarily to
A) transfer a phosphate group from a kinase to the next relay molecule in a series.
B) inactivate protein kinases to turn off signal transduction pathways.
C) amplify signal transduction so it activates multiple relay molecules.
D) amplify the second messenger cAMP

B

The primary function of kinases in signal transduction is to
A) inactivate relay molecule to turn off signal transduction.
B) regulate gene expression by serving as a transcription factor.
C) inactivate second messengers such as cAMP.
D) activate protein kinases or other relay molecules in a series.

D

Which of the following enzymes adds a phosphate group to target proteins?
A. kinase
B. phosphatase
C. G protein-coupled receptor
D. adenylyl cyclase

A

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because:
A. they are species-specific (different enzymes in different species)
B. they always lead to the same cellular response
C. they amplify the original signal manyfold
D. they counter the harmful effects of phosphatases

C

Carbon dioxide crosses the plasma membrane by simple diffusion. What determines the rate at which carbon dioxide enters the cell?
A. the amount of ATP being produced by the cell
B. the amount of a specific carrier protein in the membrane
C. the concentration of carbon dioxide on each side of the membrane

C

Sucrose is an electrically neutral disaccharide. In a H+/sucrose co-transport system, sucrose will enter the cell
A. Against its concentration gradient
B. Down/with its concentration gradient
C. Against its electrical gradient
D. Down/with its electrical gradient

A

Which of the following statements correctly describes osmosis?
A. Osmosis is an energy-demanding, ATP-requiring, "active" process
B. In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
C. In osmosis, solutes move across a membrane from areas of higher solute concentration to areas of lower solute concentration
D. Two of these are true

B

Which of the following describes the action of the sodium-potassium pump with respect to ion concentration gradients?
A. transports Na+ ions against (up) their gradient and K+ ions down (with) their gradient
B. transports K+ ions against their gradient and Na+ ions down their gradient
C. transports both Na+ ions and K+ ions down their gradients
D. transports both Na+ ions and K+ ions against their gradients

D

The inside of a cell is generally negatively charged at rest. When a neuron “fires” (responds) a wave of voltage change, the action potential, moves along the membrane. The depolarization phase beginning the action potential is due to which of these?
A.Chloride ions flow through passive channels
B. Potassium ions flow through passive channels
C. Sodium ions flow through passive channels
D. Sodium-potassium pump
E. Two of these are directly involved in the depolarization

C

The inside of a cell is generally negatively charged at rest. When a neuron “fires” (responds) there is a wave of voltage change, the action potential,. The repolarization phase, ending the action potential, when the neuron gets back to its negative resting potential, is due to which of these?
A. Chloride ions flow through passive channels
B. Potassium ions flow through passive channels
C. Sodium ions flow through passive channels
D. Sodium-potassium pump
E. Two of these are directly involved in the depolarization

B