Energy II

Question 1

Citric acid cycle

Answer 1

1. Glucose is broken down into 2 pyruvate molecules
2. In the presence of oxygen, each pyruvate is made into acetyl CoA
3. Pyruvate reacts with oxaloacetate to form citrate
4. Isomerases into isocitrate
5. Made into alpha-ketogluterate after decarboxylation and NADH production
6. Made into succinyl CoA after decarboxylation and NADH production
7. Oxaloacetate molecule made after GTP production, FADH2 production and NADH production

Question 2

What is the net gain of the citric acid cycle

Answer 2

• 6 NADH
• 2 GTP
• 2 FADH2
• 2 CO2

Question 3

What regulates entry into the citric acid cycle and why

Answer 3

Pyruvate dehydrogenase since it turns pyruvate into acetyl CoA which commits the glucose carbon skeleton to either oxidation to CO2 and energy production or fatty acid synthesis

Question 4

How is pyruvate dehydrogenase regualted

Answer 4

Inhibited by its product NADH and acetyl CoA through feedback inhibition and also its inhibited by phosphorylation

Question 5

How is pyruvate dehydrogenase regulated in muscle

Answer 5

Its activated via the action of a phosphatase, which itself is stimulated by Ca2+

Question 6

How is calcium regulated in liver

Answer 6

Adrenaline causes an increase in calcium concentration through the activation of alpha adrenergic receptors and IP3

Question 7

What happens in the liver and adipose tissue when glucose concentrations are high

Answer 7

Insulin is secreted which stimulates phosphatase which funnels glucose to fatty acid synthesis

Question 8

What regulates citrate synthase action

Answer 8

Citrate

Question 9

What regulates isocitrate dehydrogenase

Answer 9

NADH and ATP

Question 10

What stimulates isocitrate dehydrogenase

Answer 10

ADP

Question 11

What regulates alpha-keto gluterate dehydrogenase

Answer 11

NADH, ATP and succinyl CoA

Question 12

What is beriberi

Answer 12

Its a deficiency in thiamine (Vit B1)

Question 13

Where is beriberi common and what are the symptoms

Answer 13

In the far east where rice is staple

characterised by cardiac and neurological symptoms

Question 14

Why does beriberi occur

Answer 14

Thiamine is a prosthetic group for pyruvate and alpha-keto-gluterate
Therefore when thiamine is deficient these enzymes are compromised and cannot function properly, so the generation of ATP is reduced

Question 15

How does oxidative phosphorylation work

Answer 15

1. The NADH/FADH2iiii will donate a H atom, which will split into a proton and an electron
2. The electron will be passed from complex 1 all the way to complex IV down the electron transport chain
3. As it does this, the electron will loose energy, this will be used to pump protons into the inter-membrane space
4. An electrochemical gradient is set up, called the proton motive force
5. ATP is generated when protons move down their concentration gradient to add Pi to ADP to create ATP

Question 16

How much ATP is generated from NADH and FADH2 and why

Answer 16

every NADH forms 3 ATP
every FADH2 forms 2 ATP
FADH2 only enters the electron transport chain at complex II therefore more energy is released from NADH2

Question 17

Why do newborn babies have brown fat

Answer 17

Brown fat is rich in mitochondria that have uncoupling proteins
this protein allows protons to move back into the mitochondrial matrix instead of ATP synthase
The energy released is not used to make ATP but rather is released as heat

Question 18

what is an OXPHOS disease

Answer 18

A common degenerative disease thats caused by mutations in genes encoding proteins of electron transport chain
Symptoms; fatigue, epilepsy and dementia

Question 19

What regulates the electron transport chain

Answer 19

Its governed by the need for ATP, regulated uncoupling leads to the generation of heat