Lecture 18: Fermentation and Integration

Question 1

What is fermentation?

Answer 1

An extension of glycolysis
• Includes reactions that regenerate NAD+
by transferring electrons from NADH to
pyruvate or derivatives of pyruvate

Question 2

• Describe and compare the processes of lactic acid and ethanol
fermentation; including the circumstances during which they occur, the
reactions that are carried out in order to make lactic acid and ethanol, and the
amount of energy generated

Answer 2

Lactic Acid Fermentation:
- pyruvate is converted to lactic acid, NADH oxidized to NAD+ in the process.
Ethanol Fermentation:
Pyruvate converted to ethanol in 2 steps:
1. 2 Pyruvate to 2 acetaldehyde
2. 2 acetaldehyde to 2 ethanol.

BOTH OCCUR IN THE ABSENCE OF OXYGEN!

Question 3

• Know how excess glucose is stored in animal and plant cells and the
processing stored glucose undergoes in order to participate in Glycolysis

Answer 3

• In ANIMAL CELLS: stored in liver as glycogen
• Excess glucose is stored as starch in PLANT CELLS.
- glucose molecules are cleaved from the ends of glycogen and starch, in order for glycolysis to proceed.

Question 4

• Know the contribution of other sugars to Glycolysis

Answer 4

Many other sugars contribute to glycolysis!!!!!!

Question 5

• Describe the process of Beta-oxidation and its role in harvesting energy from
lipids

Answer 5

• Fatty acids are shortened by βoxidation:
removes 2-carbon units
from the ends.
- Produces a lot of reduced electron carriers. ie) NADH and FADH2
- Complete oxidation of Palmitic Acid, a fatty acid with 16 carbons,
produces 106 molecules of ATP

Question 6

Describe how ATP levels regulate cellular respiration

Answer 6

• ATP levels in the cell indicate how
much energy a cell has
• High ATP levels: the cell does not
need to keep making ATP so the
pathways that generate it are
slowed down or inhibited
• Low ATP levels: the cell activates
the pathways that lead to ATP
synthesis

Question 7

• Describe how the enzyme Phosphofructokinase-1 responds to varying ATP
concentrations in the cell

Answer 7

• When ATP levels are low, PFK-1 is activated, allowing glycolysis to continue.
• When ATP or citrate levels are high, PFK-1 is inhibited, and glycolysis slows.