0226 The TCA cycle Flashcards

 Metabolite entry to the mitochondria is regulated  Entry to TCA cycle for catabolism is acetyl-CoA  Multiple entry points for anapleurotic reactions  TCA cycle produces NADH and FADH2 for energy production  Discrete reactions subject to regulation by energy status  Intermediates may for amino-acids, glucose and porphyrins

1
Q

Where does ATP synthesis and the TCA cycle occur

A

Both occur in the mitochondrial matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What enzymes regulate the concentration of pyruvate that is destined for TCA cycle

A

Glycogen phosphorylase, glycogen synthase, hexokinase, PFK-1, Pyruvate kinase, GA3PDH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the cellular redox statuses that affect the primary pathway of carbohydrates to pyruvate (think ratios of energy molecules)

A

The ratios of [ATP]/[ADP] and [NADH]/[NAD+]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What type of transporter that carriers pyruvate into the mitochondria where it can be converted in acetyl CoA

A

OH- antiporter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What molecules inhibit the conversion of pyruvate to acetyl CoA in the mitochondria (hint: think products of the TCA cycle)

A

ATP, Acetyl CoA,NADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True or False: conversion of pyruvate to acetyl CoA is a single step reaction in the mitochondria

A

False. It is actualyl a complex reaction involving 4 steps (decarboxylation, oxidation, transter of CoASH and oxidation again)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the entry point of the TCA cycle

A

The entry point is the formation of citrate from Acetyl CoA (2 carbon) and oxaloacetate (4 carbon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Broadly describe the TCA cycle

A

A series of oxidative reactions in the mitochondrial matrix that produces reduced cofactors NADH and FADH2, GTP and CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many molecules of CO2 are produced from one round of the TCA cycle

A

2 molecules of CO2 (remember starting point if citrate 6 carbon and ending point is oxaloacetate 4 carbon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

True or false: the concentrations of intermediates in the TCA cycle are relatively high

A

False. The concentrations of intermediates are low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What cellular redox statuses inhibit and stimulate the TCA cycle

A

Inhibits TCA = increased NADH or ATP (relative to NAD+ and ADP). Stimulates TCA = increased ADP (relative to ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What regulatory mechanisms are there for the TCA cycle (hint: there are 5 categories)

A
  1. Substrate supply (acetyl CoA)
  2. Committed Step (formation alpha KG)
  3. Metabolic branching points (e.g. citrate to FA synthesis)
  4. Feedback/forward loops (several products and late stage intermediates)
  5. Cellular energy status (NADH/NAD, ATP,ADP ratios)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the committed step in the TCA cycle

A

The commited step in the TCA cycle si the conversion of isocitrate to alpha-keto-glutarate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the potential branching points for TCA cycle

A

Fatty acid synthesis (citrate), Amino acid synthesis (alpha KG), glucose synthesis (oxaloacetate), porphryins (succinyl CoA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly