Question

1. The first step in the process of cellular respiration is glycolysis, in which glucose is converted to pyruvate, and NAD+ is reduced to NADH. This process creates 2 net ATP. In order for glycolysis to continue repeatedly, NADH must be oxidized back to NAD+. (Note: You may want to review Figure 1 on p. 62 in the lab manual, shown below, and the Fermentation video in the Canvas module to answer the two questions below.) Glucose Glycolysis 2 Pyruvate, 2 NADH, 2 ATP (net) What happens to the electrons donated to NADH? In a eukaryote there are several possibilities... Anaerobic homolactic fermentation (Occurs in muscle, electrons donated back to pyruvate) Aerobic oxidation (Electrons donated to oxygen via electron transport chain) Anaerobic alcoholic fermentation (Occurs in yeast, pyruvate is decarboxylated to yield CO2 and CH3CHO [acetaldehyde]; electrons are donated to acetaldehyde to form alcohol.) 2 Lactate 2 NAD+ Pyruvate breakdown Citric Acid Cycle (CAC) Oxidative phosphorylation (OP) 2 CO2 2 Ethanol (CH3CH2OH) 2 NAD+ 6 CO2, 6 H2O, 2 NAD+ (Not all the products of pyruvate break down, CAC and OP are shown.) Figure 1. One of the products of glycolysis is NADH, which is rich in electrons. What happens to those electrons? In eukaryotes in the presence of oxygen, NADH donates its electrons to the electron transport chain in the inner membrane of the mitochondria. If oxygen is not present, then pyruvate remains in the cytosol. NADH then donates its electrons back to pyruvate. If this occurs in muscle the product is lactate (CH3CH(OH)COO-); if this occurs in yeast the product is ethanol (CH3CH2OH). a. In the presence of oxygen, how is NADH oxidized back to NAD+? (1 pt) b. Fermentation occurs in the absence of oxygen, so it cannot use the same process to regenerate NAD+. How does alcoholic fermentation solve the problem of converting NADH to NAD+ so that glycolysis (and therefore ATP production) can continue? (1 pt)

          1. The first step in the process of cellular respiration is glycolysis, in which glucose is converted to pyruvate, and NAD+ is reduced to NADH. This process creates 2 net ATP. In order for glycolysis to continue repeatedly, NADH must be oxidized back to NAD+. (Note: You may want to review Figure 1 on p. 62 in the lab manual, shown below, and the Fermentation video in the Canvas module to answer the two questions below.)

Glucose
Glycolysis
2 Pyruvate, 2 NADH, 2 ATP (net)

What happens to the electrons donated to NADH?
In a eukaryote there are several possibilities...

Anaerobic homolactic fermentation
(Occurs in muscle, electrons donated back to pyruvate)
Aerobic oxidation
(Electrons donated to oxygen via electron transport chain)
Anaerobic alcoholic fermentation
(Occurs in yeast, pyruvate is decarboxylated to yield CO2 and CH3CHO [acetaldehyde]; electrons are donated to acetaldehyde to form alcohol.)

2 Lactate
2 NAD+
Pyruvate breakdown
Citric Acid Cycle (CAC)
Oxidative phosphorylation (OP)
2 CO2
2 Ethanol (CH3CH2OH)
2 NAD+

6 CO2, 6 H2O, 2 NAD+
(Not all the products of pyruvate break down, CAC and OP are shown.)

Figure 1. One of the products of glycolysis is NADH, which is rich in electrons. What happens to those electrons? In eukaryotes in the presence of oxygen, NADH donates its electrons to the electron transport chain in the inner membrane of the mitochondria. If oxygen is not present, then pyruvate remains in the cytosol. NADH then donates its electrons back to pyruvate. If this occurs in muscle the product is lactate (CH3CH(OH)COO-); if this occurs in yeast the product is ethanol (CH3CH2OH).

a. In the presence of oxygen, how is NADH oxidized back to NAD+? (1 pt)

b. Fermentation occurs in the absence of oxygen, so it cannot use the same process to regenerate NAD+. How does alcoholic fermentation solve the problem of converting NADH to NAD+ so that glycolysis (and therefore ATP production) can continue? (1 pt)

1. The first step in the process of cellular respiration is glycolysis, in which glucose is converted to pyruvate, and NAD+ is reduced to NADH. This process creates 2 net ATP. In order for glycolysis to continue repeatedly, NADH must be oxidized back to NAD+. (Note: You may want to review Figure 1 on p. 62 in the lab manual, shown below, and the Fermentation video in the Canvas module to answer the two questions below.)

Glucose
Glycolysis
2 Pyruvate, 2 NADH, 2 ATP (net)

What happens to the electrons donated to NADH?
In a eukaryote there are several possibilities...

Anaerobic homolactic fermentation
(Occurs in muscle, electrons donated back to pyruvate)
Aerobic oxidation
(Electrons donated to oxygen via electron transport chain)
Anaerobic alcoholic fermentation
(Occurs in yeast, pyruvate is decarboxylated to yield CO2 and CH3CHO [acetaldehyde]; electrons are donated to acetaldehyde to form alcohol.)

2 Lactate
2 NAD+
Pyruvate breakdown
Citric Acid Cycle (CAC)
Oxidative phosphorylation (OP)
2 CO2
2 Ethanol (CH3CH2OH)
2 NAD+

6 CO2, 6 H2O, 2 NAD+
(Not all the products of pyruvate break down, CAC and OP are shown.)

Figure 1. One of the products of glycolysis is NADH, which is rich in electrons. What happens to those electrons? In eukaryotes in the presence of oxygen, NADH donates its electrons to the electron transport chain in the inner membrane of the mitochondria. If oxygen is not present, then pyruvate remains in the cytosol. NADH then donates its electrons back to pyruvate. If this occurs in muscle the product is lactate (CH3CH(OH)COO-); if this occurs in yeast the product is ethanol (CH3CH2OH).

a. In the presence of oxygen, how is NADH oxidized back to NAD+? (1 pt)

b. Fermentation occurs in the absence of oxygen, so it cannot use the same process to regenerate NAD+. How does alcoholic fermentation solve the problem of converting NADH to NAD+ so that glycolysis (and therefore ATP production) can continue? (1 pt)

Added by Julie K.

Question

Please give Ace some feedback