Citric Acid Cycle

Question 1

where does the citric acid cycle occur?

Answer 1

within the matrix of the mitochondria

Question 2

describe the inner and outer mitochondrial membranes

Answer 2

• outer membrane is freely permeable
• large inner membrane is mostly impermeable; molecules get across the membrane via active transport
• proteins for electron transport chain are found in the inner membrane

Question 3

T or F:

mitochondria have their own separate genome, inherited from paternal line

Answer 3

false

their separate unique genome is inherited from the maternal line

Question 4

what is apoptosis?

Answer 4

programmed cell death; mitochondria are involved in signaling apoptosis - cytochrome c moves from the cysterna of the mitochondria into the cytosol of the cell to activate a signaling cascade of procaspases which ultimately result in apoptosis

Question 5

T or F:

mitochondria with higher energy demands have more cisternal folds

Answer 5

true

Question 6

what enzyme converts pyruvate to acetyl-coa?

Answer 6

• pyruvate dehydrogenase complex
• utilizes CoA-SH and NAD+, and produces NADH in the process
• acetyle-coa is then used in the citric acid cycle

Question 7

the citric acid cycle reduces which 2 electron carriers?

Answer 7

• NAD+ is reduced to NADH
• FAD+ is reduced to FADH2
• these are oxidative phosphorylation electron sources

Question 8

the citric acid cycle is an 8-step cycle driven by the presence of what two molecules?

Answer 8

acetyl-coa and oxaloacetate

Question 9

T or F:

the citric acid cycle does not require oxygen

Answer 9

false

it actually requires oxygen in an indirect way

Question 10

describe the energetics of the citric acid cycle.

how many of each product is produced per turn?

how many turns are completed per glucose molecule utilized?

Answer 10

• per turn: 3 NADH, 2CO2, 1 GTP (ATP), and 1 FADH2
• two turns per glucose molecule

Question 11

what is the electron transport chain complex II?

Answer 11

• the conversion of succinate to fumarate by succinate dehydrogenase in the citric acid cycle
• the succinate dehydrogenase is part of the electron transport chain complex II (so it is actually a protein component of the ETC)

Question 12

describe how the citric acid cycle is allosterically regulated

Answer 12

• energy substrates/products allosterically regulate enzymes
• regulated at the most exergonic steps (release of energy)
• mass action also regulates function ([NADH]/[NAD+], [ATP]/[ADP], and oxaloacetate

Question 13

the citric acid cycle is an important synthetic pathway and produces precursors for what important products?

Answer 13

• amino acids
• nucleic acids
• fatty acids
• gluconeogenesis
• neurotransmitters
• hemes