Exam 2

For the reaction A → B, ΔG’° = -60kJ/mol. A reaction in a test tube is started with 10mmol of A; no B is initially present and no other components are added. After 24rs, analysis reveals the presence of 2mmol of B, and 8mmol of A. Which statement is the MOST likely explanation?

a) A & B have reached equilibrium concentrations

b) B formation is kinetically slow; equilibrium has not been reached by 24hrs

c) Formation of B is thermodynamically unfavorable

d) The result described is impossible, given the fact that ΔG’° is -60kJ/mol

e) An enzyme has shifted the equilibrium toward A

B formation is kinetically slow; equilibrium has not been reached by 24hrs

The type of chemical reaction below that involves the phosphorylation of a molecule using ATP as a co-substrate is:

a) oxidation/reduction

b) isomerization

c) nucleophilic reaction

d) none of these

e) group transfer

group transfer

If reaction #1 has a ΔG’° = -60kJ/mol and reaction #2 has a ΔG’° = -10kJ/mol, which of the following statements is FALSE?

a) the Keq’ for reaction #1 is greater than the Keq’ for reaction #2

b) Reaction #1 is more thermodynamically favorable than reaction #2 under standard conditions

c) Reaction #1 must reach equilibrium faster than reaction #2

d) Reaction #1 is more exergonic than reaction #2 under standard conditions

e) Under equilibrium conditions, the ratio of products to reactants is higher for reaction #1 than reaction #2

Reaction #1 must reach equilibrium faster than reaction #2

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (ΔG’°) of 23.8kJ/mol. Under what conditions (encountered in a normal cell) could this reaction proceed forward?

a) If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate

b) When it is coupled with other nonspontaneous reactions

c) When there is a very high concentration of fructose 1,6-bisphosphate relative to the concentration of products

d) When there is an equal concentration of products and fructose 1,6-bisphosphate

e) The reaction will not proceed under any conditions because the ΔG’° is positive

When there is a very high concentration of fructose 1,6-bisphosphate relative to the concentration of products

Which factor is NOT expected to significantly contribute to the regulation of enzymatic activity in a human cell?

a) enzyme concentration

b) substrate availability

c) all of these are expected to significantly contribute

d) allosteric regulation

e) temperature changes

Temperature changes

Which of the following statements is TRUE regarding the regulation of glycolysis and gluconeogenesis in cells?

a) all of these statements are true

b) Low ATP favors gluconeogenesis

c) Low AMP favors glycolysis

d) High AMP favors gluconeogenesis

e) High AMP favors glycolysis

High AMP favors glycolysis

Which of the following is NOT true regarding the conversion of glucose to glucose 6-phosphate during the first step of glycolysis?

a) It has a positive standard free energy change

b) It increases the intracellular concentration of phosphorylated glucose

c) It adds a charge to glucose, making it more difficult to transport across the membrane

d) It helps trap glucose in the cell

e) ATP is required

It has a positive standard free energy change

Which statement about the pentose phosphate pathway is CORRECT?

a) It generates 2 mol of ATP per mol of glucose consumed

b) It is a reductive pathway since it consumes NADPH

c) It provides precursors for the synthesis of nucleic acids

d) It generates O₂

e) It is an irreversible process

It provides precursors for the synthesis of nucleic acids

The interconversion step of glycolysis that occurs at the end preparatory phase involves the conversion of _____ to ______.

a) glucose 6-phosphate; fructose 6-phosphate

b) 3-phosphoglycerate; 2-phosphoglycerate

c) dihydroxyacetone phosphate; glyceraldehyde-3-phosophate

d) glucose; glucose 6-phosphate

e) phosphoenolpyruvate; pyruvate

dihydroxyacetone phosphate (DHAP) ; glyceraldehyde-3-phosophate (GAP)

The first energy yielding step of glycolysis results in the production of 1,3-bisphosphoglycerate and _____.

a) ATP

b) NADPH

c) NADH

d) NAD+

e) ADP

NADH

You would expect the output of the citric acid cycle to be DECREASED when:

a) the ratio of [ATP]/[AMP] is relatively high

b) the ratio of [ATP]/[AMP] is relatively low

c) [NADH] is low

d) none of these would lead to a decreased output

e) [NAD+] is high

the ratio of [ATP]/[AMP] is relatively high

Which of the following is NOT a component of the organelle where the citric acid cycle takes place?

a) intermembrane space

b) matric

c) inner membrane

d) stroma

e) outer membrane

stroma

The ability of the citric acid cycle to proceed is most directly influenced by the concentration of available:

a) oxaloacetate

b) NADH

c) ATP

d) CO₂

e) glucose

oxaloacetate

Triacylglycerols cannot directly go through B-oxidation because:

a) fatty acids must first be cleaved from glycerol

b) they are mostly unsaturated

c) they are mostly saturated

d) they are only present in lipoproteins

e) they are already fully oxidized

fatty acids must first be cleaved from glycerol

Which statement is TRUE regarding ketone bodies?

a) Excess acetoacetate produced during ketone body production is mostly exhaled

b) Ketone bodies can be used as a source of acetyl-CoA in target tissues when blood glucose is low

c) Ketone bodies can easily travel from one tissue to another in the body due to the presence of Coenzyme A

d) Ketone bodies are only formed during times of starvation

e) Ketone bodies tend to be formed when oxaloacetate concentrations are high

Ketone bodies can be used as a source of acetyl-CoA in target tissues when blood glucose is low

Full oxidation of which molecule would you expect to yield the most energy?

a) glucose

b) oleic acid (18C monounsaturated fatty acid)

c) pyruvate

d) NADH

e) palmitate (16C saturated fatty acid)

oleic acid (18C MUS fatty acid)

Long chain fatty acids are transported into the organelle where B-oxidation takes place through the _____ transporter.

a) ACC

b) Triose-phosphate

c) carbamoyl

d) FAS

e) carnitine

carnitine

The name of the family of enzymes that cleaves fatty acids from glycerol is ________, which can be activated by hormones such as ________.

a) lipases; glucagon & epinephrine

b) kinases; insulin & epinenphrine

c) lipases; insulin & cortisol

d) kinases; glucagon & epinephrine

e) lipases; insulin & epinephrine

lipases; glucagon & epinephrine

Before ammonia can be expelled from the body as urea, it is first used in the synthesis of carbamoyl phosphate within the mitochondria, when then combines with ______ in the first step of the urea cycle.

a) ornithine

b) glutamate

c) bicarbonate

d) glutamine

e) arginine

ornithine

Under which condition(s) would you expect the enzymes of the urea cycle to be at high activity levels?

a) starvation or low protein diet

b) starvation or high protein diet

c) low protein diet

d) high protein diet

e) starvation

starvation or high protein diet

Phosphorylation and oxidative phosphorylation appear to be generally similar processes, both consisting of ATP synthesis driven by the transfer of electrons along the ETC. However, which of the following statement is NOT true?

a) Both processes utilize 4 transmembrane bound protein complexes

b) Water is involved in both processes

c) Both processes involve at least one nucleotide-based electron carrier cofactor

d) Both processes rely on a proton gradient to drive ATP production

e) Both processes contain at least one lipid soluble mobile electron carrier in their electron carrier chains

Both processes utilize 4 transmembrane bound protein complexes

Complex II of the oxidative phosphorylation electron transport chain is directly involved in all of the following except:

a) production of reduced Coenzyme Q

b) reduction of FAD

c) citric acid cycle

d) conversion of succinate to fumurate

e) pumping of electrons into the mitochondria intermembrane space

pumping of electrons into the mitochondria intermembrane space

Much of the oxygen one consumes in breathing is converted to _____ through cellular respiration:

a) CO₂

b) CO and then to CO₂

c) acetyl-Coa

d) oxygen is converted to all of these compounds

e) water

water

Which of the following conformations of the alpha-beta dimers in the enzyme is responsible for ATP synthesis in the mitochondria would be simultaneously bound to ADP and P_i?

a) loose

b) open

c) need more info

d) closed

e) tight

loose

In the mitochondrial electron transport chain, the amount of ATP generated from NADH oxidation is _____ than the amount generated from FADH₂ oxidation b/c only NADH interacts with _____.

a) greater; complex I

b) greater; complex II

c) less; complex I

d) less; complex II

e) greater; complex IV

greater; complex I

The main triose phosphate made in the Calvin Cycle that plants use for the synthesis of starch is:

a) glucose 6-phosphate (G6P)

b) ribulose 1,5-bisphosphate (RuBP)

c) glyceraldehyde 3-phosphate (G3P)

d) 3-phosphoglycerate (3-PGA)

e) dihydroxyacetone phosphate (DHAP)

glyceraldehyde 3-phosphate (G3P)

Within the electron transport chain found within the chloroplast, ____ of the ____ protein complexes are directly involved in pumping protons across a membrane

a) 3;4

b) 2;3

c) 1;4

d) 1;3

e) 2;4

1;3

The assimilation of CO₂ into glyceraldehyde 3-phosphate (G3P) in green plants:

a) takes place at equal rates in light & darkness

b) begins w/ the condensation of a 2-carbon compound with CO₂

c) requires energy from ATP

d) is a four phase process

e) takes place in the cytosol

requires energy from ATP

One round of the Calvin Cycle driven by the energy provided by 9 molecules of _____ and the reducing power provided by 6 molecules of ____.

a) ATP; NADPH

b) G3P; CO₂

c) ATP; CO₂

d) ATP; NADH

e) NADPH; ATP

ATP; NADPH

The 3-carbon molecule that is transported through the Pi-triose phosphate antiporter is used in the synthesis of:

a) starch

b) glycogen

c) ATP

d) sucrose & starch

e) sucrose

sucrose

The reduced coenzyme that is required for fatty acid synthesis in animals can be provided by ______.

a) pentose phosphate pathway, malic enzyme reaction, and the energy transduction steps of photosynthesis

b) pentose phosphate pathway and malic enzyme reaction

c) malic enzyme reaction

d) energy transduction steps of photosynthesis

e) pentose phosphate pathway

pentose phosphate pathway and malic enzyme reaction

The component(s) of triacylglycerol that is/are used to release energy are:

a) glycerol & fatty acids

b) glycerol

c) none are correct

d) glucose 6-phosphate

e) fatty acids

The lipoprotein that is mostly responsible for bringing excess cholesterol back to liver from the tissues is:

a) VLDL

b) VHDL

c) HLDL

d) LDL

e) HDL

HDL

Which of the following is NOT a major class of human plasma lipoproteins?

a) VHDL

b) all are classes of lipoproteins

c) HDL

d) LDL

e) VLDL

VHDL

Which statement is FALSE regarding cholesterol found in the human body?

a) it is mostly found within lipoprotein particles when being transported

b) it is the starting point for steroid hormone synthesis

c) it mostly originates from dietary intake

d) it is built from isoprene subunits

e) it is found in cell membranes

It mostly originates from dietary intake

One amino acid NOT directly involved in the de novo biosynthesis of nucleotides is:

a) aspartate

b) glycine

c) thymine

d) all are amino acids directly involved

e) glutamine

thymine

Which of the following is not considered a key biomolecule intermediate required for synthesis of at least one amino acid?

a) pyruvate

b) ribose 5-phosphate

c) oxaloacetate

d) succinate

e) 3-phosphoglycerate

succinate

An amino acid that can be made from an intermediate of the citric acid cycle being exposed to two consecutive transamination reaction is:
a) aspartate

b) histidine

c) glutamine

d) arginine

e) glutamate

glutamine

The overall biosynthesis of amino acids relies on chemical intermediates from all of the following except:

a) de-novo synthesis

b) citric acid cycle

c) glycolysis

d) pentose phosphate pathway

e) all are involved

de-novo synthesis

The main source(s) of nitrogen during amino acid synthesis is/are:

a) glutamine, glutamate, & glycine

b) glutamate

c) glutamine & glutamate

d) glycine

e) glutamine

glutamine & glutamate