Energy II

Question 1

what is aerobic respiration and where does it take place?

Answer 1

→Aerobic respiration is the process of producing cellular energy involving oxygen.
→ it occurs ONLY in the presence of oxygen
→ it yields more energy than anaerobic respiration in the form of ATP (around 38)
→it takes place in the mitochondria

Question 2

what are the steps in the citric acid cycle?

Answer 2

→Pyruvate (3C) is converted to Acetyl CoA (2C), releasing a CO2 molecule and an NADH molecule.

→This is done by the enzyme Pyruvate Dehydrogenase.

→ Acetyl CoA (2C) is then joined with Oxaloacetate (4C) to make citric acid (6C).

→This is done by the enzyme Citrate Synthase.

→ Citric Acid (6C) is then converted to Isocitrate (6C).

→Isocitrate (6C) is then converted to α-ketoglutarate (5C) by Isocitrate Dehydrogenase. This releases a molecule of CO2 and NADH.

→ α-ketoglutarate (5C) is converted to Succinyl CoA (5C) by α-ketoglutarate dehydrogenase. This, again, releases a molecule of CO2 and NADH.

→Succinyl CoA (5C) is converted to Succinate (4C), releasing GTP.

→ Succinate (4C) is then converted to Fumarate (4C), releasing FADH2.

→Fumerate (4C) is converted to Malate (4C).

→ Malate (4C) is finally converted to Oxaloacetate (4C), releasing NADH.

Question 3

what does pyruvate dehydrogenase do and what is it inhibited and stimulated by?

Answer 3

→converts Pyruvate to Acetyl CoA
→ inhibited by NADH, ATP, Acetyl CoA -
→stimulated by ADP and Pyruvate

Question 4

what does citrate synthase do and what is it inhibited by?

Answer 4

→joins Oxaloacetate and Acetyl CoA to make Citrate

→ inhibited by citrate

Question 5

what does isocitrate dehydrogenase do and what is it inihbited and stimulated by

Answer 5

→it converts Isocitrate to α-ketoglutarate
→inhibited by NADH and ATP
→ stimulated by ADP

Question 6

what does α ketoglutarate dehydrogenase do and what is it inhibited by?

Answer 6

→catalyses the conversion of α-ketoglutarate to succinyl-CoA
→inhibited by NADH, ATP and Succinyl CoA

Question 7

how many molecules of FADH and NADH and GTP are made in every citric acid cycle?

Answer 7

→FADH2 = 1
→NADH = 3
→GTP  = 1

Question 8

what regulates entry into the citric acid cycle?

Answer 8

→ formation of Acetyl CoA from Pyruvate (by Pyruvate Dehydrogenase) is irreversible.
→This commits the glucose carbon skeleton to either oxidation to CO2 and energy production or fatty acid synthesis.

Question 9

how is pyruvate dehydrogenase activated in muscles?

Answer 9

→In muscles, Pyruvate Dehydrogenase is activated again via the action of a phosphatase; this enzyme is stimulated by Ca2+ (this increases CoA production)

Question 10

how do calcium levels increase in the liver?

Answer 10

→In the liver, adrenalin increases calcium through the activation of α-adrenergic receptors and IP3

Question 11

how is phosphatase stimulated in the liver?

Answer 11

→ In the liver and adipose tissue, insulin (which signifies the fed state) stimulates the phosphatase, which funnels glucose to Fatty Acid synthesis

Question 12

what is beri beri?

Answer 12

→disease in which the body has a deficiency in thiamine (Vit B1).
→Thiamine is a prosthetic group for pyruvate and α-ketoglutarate dehydrogenase.
→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.

Question 13

how many ATP molecules are produced each from NADH and FADH2?

Answer 13

→For every NADH molecule, 3 ATP molecules are formed.

→For every FADH2 molecule, 2 ATP molecules are formed.

Question 14

how does ATP Synthase generate ATP?

Answer 14

→due to the H+ gradient created, the ions now move back down into the matrix of the mitochondria through ATP Synthase down their electrochemical gradient

→This movement generates enough energy for it to combine ADP and phosphate into ATP.

Question 15

why do newborn babies need brown fat and where is this distributed?

Answer 15

→newborn babies can’t 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.

Question 16

what are OXPHOS Diseases and what are the symptoms?

Answer 16

→Common degenerative diseases

→Caused by mutations in genes encoding proteins of ETC

→Lead to a number of symptoms, including fatigue, epilepsy, dementia

→dependent on the mutation, symptoms may be evident near birth to early adulthood

→Metabolic consequence can be congenital lactic acidosis