Chapter 9 Quiz
New biosensors, applied like a temporary tattoo to the skin, can alert serious athletes that they are about to "hit the wall" and find it difficult to continue exercising. These biosensors monitor lactate, a form of lactic acid, released in sweat during strenuous exercise. Which of the statements below is the best explanation of why athletes would need to monitor lactate levels?
During anaerobic respiration, lactate levels increase when muscles cells need more energy, however muscles cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration.
Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?
30-32
For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle (see the accompanying figure)?
4
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of _____.
ATP, CO2, and ethanol (ethyl alcohol)
Which of the listed statements describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced.
A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
Catabolic processes are activated that generate more ATP.
During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
A young dog has never had much energy. He is brought to a veterinarian for help and she decides to conduct several diagnostic tests. She discovers that the dog's mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of the dog's condition?
His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.
Which of the following statements about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in the accompanying figure?
Oxaloacetate will accumulate and citric acid will decrease.
Given what you know about glycolysis and regulation of metabolism by PFK, what is the likely mechanism by which PFK activity differs depending on ATP concentration?
PFK is an allosteric enzyme that is inhibited by ATP and stimulated by AMP. PFK is an allosteric enzyme that is inhibited by ATP. Thus, at higher concentrations of ATP, the enzyme is less active. At low ATP concentrations in the cell, the concentrations of AMP and ADP are higher, and AMP stimulates activity of PFK. Therefore, PFK activity is higher when the concentration of ATP is low.
Based on the graph, is PFK more active at low or high ATP concentration?
PFK is more active at low ATP concentration. Under both conditions, the PFK enzyme increases in activity as the concentration of the substrate increases, up until a point at which the rate levels off. Under conditions of low ATP concentration, however, PFK enzyme activity increases faster and reaches its maximum rate sooner.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
In chemiosmosis, what is the most direct source of energy that is used to convert ADP + i to ATP?
energy released from movement of protons through ATP synthase, down their electrochemical gradient
During aerobic respiration, electrons travel downhill in which sequence?
glucose → NADH → electron transport chain oxygen
Substrate-level phosphorylation occurs _____.
in both glycolysis and the citric acid cycle
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
One function of both alcohol fermentation and lactic acid fermentation is to _____.
oxidize NADH to NAD+
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+
pyruvate
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____.
reduced
In glycolysis, for each molecule of glucose oxidized to pyruvate _____.
two molecules of ATP are used and four molecules of ATP are produced.