Energy II: Acetyl CoA, Mitochondria, Oxygen Flashcards
For each glucose molecule how many of each product are there from the citric
acid cycle and from glycolysis? (NADH, FADH2, GTP, CO2, ATP).
- 6 NADH + 2 NADH (from glycolysis)
- 2 FADH2
- 2 GTP
- 4 CO2 + 2 CO2 (from pyruvate –> acetyl CoA)
- 0 ATP + 2 ATP (from glycolysis)
What are the enzymes involved in the citric acid cycle?
1) Pyruvate Dehydrogenase
2) Citrate Synthase
3) Isocitrate Dehydrogenase
4) α –ketoglutarate Dehydrogenase
What does Citrate Synthase do and what is it inhibited by?
Joins Oxaloacetate and Acetyl CoA to make citrate.
What does Pyruvate dehydrogenase do and what is it inhibited/stimulated by?
Converts Pyruvate to Aceytl CoA.
Stimulated by:
•ADP
•Pyruvate
Inhibited by:
•NADH
•ATP
•Acetyl CoA
What does isocitrate dehydrogenase do and what is it inhibited/stimulated by?
Converts isocitrate to α-ketoglutarate
Stimulated by
ADP
Inhibited by
•NADH
•ATP
What does α –ketoglutarate dehydrogenase do and what is it inhibited/stimulated by?
Catalyses the conversion of α-ketoglutarate to succinyl-CoA.
Inhibited by
•NADH
•ATP
•Succinyl CoA
What regulates entry into the citric acid cycle?
The formation of Acetyl CoA from Pyruvate is irreversible. This commits the glucose carbon skeleton to either oxidation to CO2 and energy production or fatty acid synthesis.
Pyruvate Dehydrogenase is regulated through phosphorylation. Inhibited by phosphorylation (using ATP?)
• In muscles, Pyruvate Dehydrogenase is activated again via the action of a phosphatase; this enzyme is stimulated by Ca2+ (this increases CoA production).
• In the liver, adrenalin increases calcium through the activation of α-adrenergic receptors and IP3.
• In the liver and adipose tissue, insulin (which signifies the feed state) stimulates the phosphatase, which funnels glucose to Fatty Acid synthesis
Build up of NADH and acetyl CoA inform the enzyme that energy needs of the cell are being met, or that fatty acids are been broken down to produce NADH and Aceytl CoA. This has the effect of sparing glucose.
What happens when citrate is transported out of the mitochondria?
- It inhibits PFK, which stops glycolysis.
* It also acts as a source of acetyl CoA for Fatty Acid synthesis.
Describe BeriBeri.
• It’s a disease in which the body has a deficiency in thiamine (Vit B1).
• Thiamine is a prosthetic group for pyruvate and α-ketoglutarate dehydrogenase.
o Therefore, enzymes are compromised leading to the TCA being compromised and so a decrease in ATP production.
• It’s characterised by cardiac and neurological symptoms (impairment of nerves and heart).
• It’s common where rice is a staple. Neurological disorders are common as glucose is a primary source of energy.
Describe BeriBeri.
• It’s a disease in which the body has a deficiency in thiamine (Vit B1).
• Thiamine is a prosthetic group for pyruvate and α-ketoglutarate dehydrogenase.
o Therefore, enzymes are compromised leading to the TCA being compromised and so a decrease in ATP production.
• It’s characterised by cardiac and neurological symptoms (impairment of nerves and heart).
• It’s common where rice is a staple. Neurological disorders are common as glucose is a primary source of energy.
What happens to the NADH and FADH2 produced?
Oxidative phosphorylation.
- Removal of hydrogen atoms from oxidisable substrates, NADH and FADH2 (and succinate?).
- H atoms enter ETC and each is split to give an electron and a proton.
- The electron passes through a series of enzymes called cytochromes ad finally reacts with molecular oxygen.
- Water is formed as oxygen receives the electrons from the 4th protein complex and combines with protons on the inside of the cell.
What happens after hydrogen is pumped across the Intermembrane?
- Hydrogen atom is pumped acorss the IMM which forms a pH gradient transmembrane poteintial (proton motive force).
- This is coupled to ATPsynthase.
- Protons pass through ATPsynthase as they move back into the matrix.
- This movement generates enough energy for it to combine ADP and Pi into ATP.
How many ATP is produced per NADH and FADH2?
NADH forms 3 ATP.
FADH2 forms 2 ATP.
Where is brown fat and white fat found?
Brown fat is found in newborns and white fat is found in adult tissues.
Morphology differs b/w white and brown fat
Why do newborn babies need brown fat?
- New born babies cannot shiver, so they have brown fat (brown due to the high levels of mitochondria).
- High levels of brown fat in newborns provides an alternative way of regulating heat, to protect them from hypothermia.
- The brown fat is distributed around the shoulders and down the back. As they grow, the amount of brown fat they have decreases.
- Mitochondria express uncoupling protein – splits gradients formed from ATP synthesis. – generate heat instead of ATP, after H+ move down their concentration gradient.
