Study Question 10
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Why is NAD considered to be a coenzyme rather than an enzyme?
A coenzyme is an organic molecule which is required by the enzyme to catalyze a reaction
Which of the following are true statements about the process of glycolysis?
Ancient prokaryotes are thought to have used glycolysis to make ATP long before oxygen was present in the earth's atmosphere. At the end of the glycolysis reactions, NAD+ accepts electrons from the H atoms that were initially removed from glucose It probably evolved early in history of life It is the first step in both fermentation and aerobic respiration
Explain why there was a decrease in oxygen concentration and an increase in lactate concentration in the muscle cells at the most strenuous part of the runner's exercise regimen.
At the peak of the athlete's exercise routine, his cells were consuming oxygen as fast as it could be supplied to his muscle cells resulting in a decrease in the oxygen concentration in his muscle tissue. Once his muscle cells were depleted of oxygen they began producing lactate via fermentation. As a result, the concentration of lactate would increase in the muscle tissue.
During yeast fermentation (Steps 1 and 2) why is there an increase in temperature inside the fermentation vats?
During biochemical reactions energy is lost in the form of heat
Explain why you chose your answer to question #41 above.
Oxidation is the loss of e- or H atoms from a molecule whereas reduction is the gain of e- (s) or H atom (s) from a molecule. • In this reaction pyruvate gains H atoms so it is reduced whereas NADH loses H so it is oxidized.
A biologist isolated a species of true bacterium from deep in the mud of a swamp. The oxygen levels in the mud were measured to be near zero. Analysis of the bacterium's metabolism indicated that it was capable of oxidizing decaying vegetation in the mud to produce small amounts of ATP. He also found that the cells would grow in the lab under normal levels of oxygen levels and produced nearly 20 times more ATP than when growing in the mud. Which of the following are true statements concerning this bacterium?
The bacterium is prokaryotic. The bacterium possesses a cell wall The bacterium is a facultative anaerobe
The gas escaping from the one-way valve of the fermentation vat is _________.
carbon dioxide
What is the name of the enzyme in this reaction responsible for catalyzing the addition or removal of H from organic molecules such as pyruvate and lactate?
dehydrogenase
During glycolysis, ATP is produced during the oxidation of glucose by the process of substrate level phosphorylation. During this process, a(an) ______ catalyzes the ______ of a phosphate functional group from an organic molecule. The phosphate group is picked up by ____ to produce _______.
enzyme; removal; ADP; ATP
Which of the following occur during Step 2 of the fermentation by the yeast?
ethyl alcohol is produced NADH is oxidized to form NAD+ Carbon dioxide is produced
Which of the following occur during Step 1 (Glycolysis) in the runner's muscle cells during his strenuous exercise? Check all that apply.
glucose is oxidized Pyruvate is produced. For each molecule of glucose metabolized by the muscle cells, a net amount of 2 ATP molecules are produced in the cytoplasm.
Select all of the True statements about the yeast used in the fermentation vat.
heterotrophic eukaryotes belonging to the Kingdom: Fungi
When lactate is converted to pyruvate, lactate is __________ and NAD+ is _______
oxidized; reduced
When pyruvate is converted into lactate, pyruvate is ___________ and NADH is ________
reduced; oxidized
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The net results of the complete oxidation of 10 molecules of glucose by a Lactobacillus bacterium would result in the production of which of the following substances?
2O ATP 20 lactate
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What is the primary function of the molecule NAD in biochemical reactions?
NAD functions to carry H atoms (e-) in biochemical reactions.
After the runner stops his strenuous exercise, explain why there is both a rapid increase in oxygen consumption and a rapid decline in lactate production in his muscle cells.
Once the athlete stops his strenuous exercise routine, the oxygen levels reaching his cells via the blood increases and his cells shift from fermentation to aerobic respiration, thus stopping the continued production of lactate; resulting in a decrease in levels of lactate in his muscle tissue. Note: When oxygen is no longer limited, the lactate is converted back to pyruvate which can then enter into the aerobic respiration cycle.
Which of the following occur during Step 2 in the runner's muscle cells during his strenuous exercise?
Two molecules of pyruvate are converted to 2 molecules of lactate NAD+ is produced which is used in Step 1 (glycolysis) to pick up more H atoms.
Why was air pumped out of the fermentation vat and no air allowed to enter via the one-way valve?
Yeast are facultative anaerobes which means that under high oxygen concentrations, they carry out aerobic respiration which doesn't result in the production of ethanol. When under low oxygen concentration the yeast carry out alcohol fermentation resulting in the production of ethanol • Therefore, to force the yeast cells to undergo alcohol fermentation the oxygen concentration in the vats must be lowered (1)by pumping out oxygen and (2) preventing oxygen in the air from entering the vat by addition of a one way valve into the vat but still allowing for CO2 (a product of fermentation) to leave the vat.
What sugar in the milk is being oxidized by the bacteria during the production of yogurt ?
lactose or glucose
Since no sugar was added to the fermentation vat, what was the source of the sugar (glucose) being oxidized by the yeast cells?
wheat seeds
Why are the Lactobacillus bacteria grown under low oxygen concentrations?
• Lactobacillus is a facultative anaerobe • when under high oxygen concentrations, it carries out aerobic respiration which doesn't product lactate required in the yogurt making process. • When under low oxygen concentration the lactobacillus carries out lactate fermentation resulting in the production of lactate required for yogurt making.