Question

2. A biochemist wanted to study how various substances were used in cellular respiration. In one experiment, she allowed a mouse to breathe air containing O2 "labeled" by a particular isotope. In the mouse, the labeled oxygen first showed up in
a. ATT.
b. NADH
C. CO2
d. H2O

3. A gram of fat produces _____ as much ATP as a gram of glucose.
a. two times
b. three times
c. four times
d. five times

4. The intermembrane space of mitochondria has a large concentration of
a. FADHz.
b. hydrogen ions.
C. NAD
d. oxygen

5. During pyruvate oxidation, a carboxyl group is first removed before NAD+ is reduced to NADH. Which of the following molecules does the oxidized two-carbon molecule combine with to produce the final substrate?
a. acetyl CoA
b. coenzyme A
C. pyruvate dehydrogenase
d. succinate

6. Which of the following is a true distinction between cellular respiration and fermentation?
a. NADH is oxidized by passing electrons to the electron transport chain in respiration only.
b. Only respiration oxidizes glucose.
C. Substrate-level phosphorylation is unique to fermentation;
cellular respiration uses oxidative phosphorylation.
d. Fermentation is the metabolic pathway found in prokaryotes;
cellular respiration is unique to eukaryotes.

Answer 1

2) the 1st step in cellular respiration is glycolysis that is breakdown of glucose into energy. the oxygen combines with protons and electrons produced during the catalysis to yield water. hence the 1st appearance of oxygen will be seen in water.

3) A gram of fat has twice the energy as compared to an equivalent of carbohydrate molecule. each gram of fat has around 9 calories while a sugar has only 4- 4.5 calories.

4) Due to the ETC running through the complexes present on the membranes of the mitochondria it finally results in a gradient in which there is a high concentration of protons(hydrogen ions) in the intermembrane space.this then causes the protons to move back into the lumen through the ATPase producing ATP.

5) Coenzyme A. This is a step that occurs in between glycolysis and krebs cycle.

The pyruvate which is the product of glycolysis gets oxidised to a 2 carbon molecule by pyruvate dehydrogenase that then combines with coenzyme A that finally yields acetyl CoA that is the substrate for krebs cycle.

6) NADH is oxidised through ETC in respiration only.

Fermentation occurs only in anerobic conditions. Hence whatever NADH is produced is gone back into NAD+.Since all the generated NADH is consumed, there is no NADH which can enter the ETC. That is why fermentation is truly not considered respiration though it produces small amounts of energy.