Energy II: Acetyl CoA, Mitochondria and Oxygen Flashcards
How is glycolysis related to the tricarboxylic acid cycle?
Glycolysis produces pyruvate, which in the presence of oxygen, will enter into the TCA cycle (krebs cycle)
How is glycolysis related to oxidative phosphorylation?
Glycolysis leads to the production of pyruvate in the presence of oxygen, which then will produce products that enter into ATP synthesis (oxidative phosphorylation)
Where are enzymes of the TCA?
In the mitochondrial matrix
Where does oxidative phosphorylation take place?
Inner mitochondrial membrane
Where does the TCA cycle take place?
Mitochondrial matrix
What is pyruvate converted into?
What does this require and what is produced in the process?
2C Acetyl CoA - This is by decarboxylation (removal of CO2)
An NADH molecule is produced in the process
What does acetyl CoA react with?
Oxaloacetic acid (4C), forms Citrate (6C)
What does citrate undergo?
Citrate undergoes 2 decarboxylations, meaning it loses 2 carbon dioxide molecules, and produces 2 NADH molecules. It forms a 4C compound
Firstly, citrate is switched to it’s isomer isocitrate
Then the first decarboxylation produces alpha- ketoglutarate (5C)
The second decarboxylation produces Succinyl CoA (4C)
What happens to the 4C Succinyl CoA compound produced from citrate?
Produces GTP, FADH2 and NADH to form oxaloacetate (4C).
GTP is produce when Succinyl CoA is converted into Succinate (GDP is phosphorylated into GTP)
FADH2 is produced when 4C succinate is converted into 4C fumarate (FAD is reduced into FADH2)
Fumarate is converted into malate, forming a molecule of water in the process
Malate is then converted into oxaloacetate, producing NADH as NAD+ is reduced
What are the net products of the TCA cycle?
For each pyruvate:
6 NADH + 2 NADH (from conversion of pyruvate to acetyl CoA)
2 FADH2
2 GTP
4 CO2 + 2 CO2 (from conversion of pyruvate to acetyl CoA)
What enzyme regulates entry into the TCA cycle and what is it inhibited by?
Pyruvate dehydrogenase, inhibited by NADH and Acetyl CoA
Regulates conversion of pyruvate into acetyl CoA.
Also regulated through phosphorylation by a kinase and a phosphatase
What does Isocitrate dehydrogenase do?
What would inhibition of this lead to?
Regulates conversion of 6C isocitrate into alpha-ketoglutarate (5C). Inhibition of this enzyme would lead to a build-up of citrate.
The citrate would act as a source of acetyl CoA for fatty acid synthesis.
What does alpha-ketoglutarate dehydrogenase do?
Regulates conversion of alpha-ketoglutarate into Succinyl CoA.
What is the electron transport chain?
A series of complexes that transfer electrons from donors to acceptors via redox reactions, and couples this electron transfer with the transfer of protons (H+ ions) across the inner mitochondrial membrane
How are NADH and FADH2 involved in the electron transport chain?
Their H atoms can be removed due to these being their reduced states.
NADH donates an electron to complex I, producing NAD+
FADH2 donates electron to complex II (succinate dehydrogenase), produced FAD
Electrons from either complex flow into coenzyme Q (ubiquinone)
Coenzyme Q passes electrons to cytochromes (proteins with heme groups: complex III (cytochromes and c1) → cytochrome c → complex IV (cytochrome oxidase: cytochromes a, a3)→ oxygen (this is when oxygen acts as the terminal electron acceptor)
