!!!

Question 1

Where does this take place?
1. glycolysis

Answer 1

cytosol

Question 2

2. citric acid cycle

Answer 2

mitochondria

Question 3

3. conversion of pyruvate to activated acetyl groups

Answer 3

mitochondria

Question 4

4. oxidation of fatty acids to acetyl CoA

Answer 4

mitochondria

Question 5

5. glycogen breakdown

Answer 5

cytosol

Question 6

6. release of fatty acids from triacylglycerols

Answer 6

cytosol

Question 7

7. oxidative phosphorylation

Answer 7

mitochondria

Question 8

T/F:
Facilitated diffusion can be described as the favorable movement of one solute down its concentration gradient being coupled with the unfavorable
movement of a second solute up its concentration gradient.

Answer 8

FALSE
- coupled transport

Question 9

The electrochemical gradient for K+
across the plasma membrane is small. Therefore, any movement of K+
from the inside to the outside of the cell is driven
solely by its concentration gradient.

Answer 9

FALSE
-includes both a concentration gradient and an electrical gradient, collectively influencing K+’s movement across the membrane

Question 10

Describe the process by which gut epithelial cells use transporters to take up ingested glucose (against the concentration gradient) and to
distribute glucose to other tissues by moving it back out of the cell (down the concentration gradient).

Answer 10

Gut epithelial cells use a two-step transport process to handle glucose. First, glucose is taken up from the intestinal lumen against its concentration gradient
into the epithelial cells. This is achieved through a co-transport mechanism.

Once inside the epithelial cells, glucose moves down its concentration gradient into the bloodstream through another set of transporters, specifically the
GLUT2 transporters located at the basolateral membrane. This step involves facilitated diffusion, where glucose exits the cell passively without the direct
expenditure of energy, reaching other tissues where it can be utilized.

Question 11

2) Although ATP and NADH are both important activated carrier molecules, ATP hydrolysis provides the direct molecular energy for most
biochemical reactions. Why do the mitochondria also need to generate high levels of NAD+?

Answer 11

NAD+ is crucial as a coenzyme in oxidative phosphorylation and the citric acid cycle, where it functions as an essential electron carrier. During these
metabolic processes, NAD+ accepts electrons, becoming reduced to NADH. The regenerated NAD+ allows continuous processing of metabolic cycles, as it
is required for the dehydrogenation of substrates in the citric acid cycle and other metabolic pathways.
Furthermore, high levels of NAD+ are necessary to maintain the NAD+/NADH ratio, which is critical for cellular redox balance and the overall metabolic
health of the cell.

Question 12

1. H2O ↔ ½O2 + 2H+ + 2 e
   mV?

Answer 12

B. +820 mV

Question 13

2. reduced ubiquinone ↔ oxidized ubiquinone + 2H+ + 2 e
   mV?

Answer 13

D. –320 mV

Question 14

3. NADH ↔ NAD+ + H+ + 2 e
   mV?

Answer 14

C. +230 mV

Question 15

4. reduced cytochrome c ↔ oxidized cytochrome c + e
   mV?

Answer 15

A. +30 mV

Question 16

How do these standard redox potentials support our understanding of the stepwise electron transfers that occur in the electron-transport chain?
(2)

Answer 16

Electrons flow from carriers with lower or more negative redox potentials to those with higher or more positive redox potentials. This gradient in
redox potential drives the sequential transfer of electrons, ensuring efficient energy capture through the establishment of a proton gradient that is used to synthesize ATP.

The differences in redox potentials prevent the simultaneous release of large amounts of energy and maintaining efficiency in ATP production

Question 17

Why would it not be advantageous for living systems to evolve a mechanism for the direct transfer of electrons from NADH to O2? (2)

Answer 17

A direct electron transfer from NADH to O2 would be energetically wasteful. The large potential energy difference between NADH and oxygen
would lead to the release of a significant amount of energy at once, which could not be efficiently captured for ATP synthesis.
Moreover, a direct transfer could increase the risk of forming reactive oxygen species (ROS).

Question 18

Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the
postsynaptic cell from firing an action potential?

Answer 18

(d) by opening Cl–
channels

Question 19

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a
single step is that ________________.

Answer 19

energy can be extracted in usable amounts.

Question 20

Fatty acids can easily be used to generate energy for the cell. Which of the following fatty acids will yield more energy?
(a) CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH=CH-COOH
(b) CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH
(c) CH3-CH=CH-CH2-CH2-CH2-CH2-CH=CH-COOH
(d) CH3-CH2-CH2-CH2-CH2-CH2-CH2-COOH

Answer 20

(b) CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

Question 21

Cells have oligosaccharides displayed on their cell surface that are important for cell–cell recognition. Your friend discovered a transmembrane
glycoprotein, GP1, on a pathogenic yeast cell that is recognized by human immune cells. He decides to purify large amounts of GP1 by expressing it in
bacteria. To his purified protein he then adds a branched 14-sugar oligosaccharide to the asparagine of the only Asn-X-Ser sequence found on GP1 (Figure).
Unfortunately, immune cells do not seem to recognize this synthesized glycoprotein. Which of the following statements is a likely explanation for this
problem?

Answer 21

The oligosaccharide needs to be further modified before it is mature.

Question 22

The Figure shows the orientation of the Krt1 protein on the membrane of a Golgi-derived vesicle that will fuse with the plasma membrane.

Answer 22

When this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be in the extracellular space.