Energy production : carbohydrate 4

Question 1

What is the role of pyruvate dehydrogenase?

Answer 1

• Transform pyruvate to acetyl CoA through decarboxylation
• pyruvate + CoA + NAD+ –PDH–> acetyl CoA + CO2 + NADH + H+

Question 2

What is the characteristics of pyruvate decarboxyation?

Answer 2

• Occurs in the matrix
• irreversible
• key regulatory step

Question 3

What is the characteristics of PDH

Answer 3

• large multi-enzyme complex (5 enzymes)
• different enzyme activities require different cofactors
• sensitive to Vitamin B1 deficiency

*Vitamin B1 is a type of cofactor

Question 4

What are the roles of the tricarboxylic acid cycle TCA in metabolism?

Answer 4

• 1 cycle produces :
  
  • 3 NADH, 1 FADH2, 1 GTP and 2 CO2
• produces precursors for biosynthesis

Question 5

How is the TCA cycle regulated?

Answer 5

(+)

• ADP, NAD+

(-)

• NADH, ATP

Question 6

Name the enzymes that are the involved in the TCA cycle of comitting steps?

Answer 6

• Isocitrate dehydrogenase
• a-ketoglutarate dehydrogenase

Question 7

What are the functions of Isocitrate dehydrogenase and a-ketoglutarate dehydrogenase?

Answer 7

• Isocitrate dehydrogenase : converts isocitrate to a-ketoglutarate
• a-ketoglutarate dehydrogenase : converts a-ketoglutarate to succinyl-CoA

Question 8

What are the characteristics of TCA cycle?

Answer 8

• Mitochondrial matrix
• central pathway in the catabolism of sugars, f.a, ketone bodies, amino acids and alcohol
• Oxidative
• Does not function in absence of O2
• Intermediates act catalytically
• breaks all C-C bonds
• breaks all C-H bonds
• trasnfers all H atoms to NAD+ and FAD

Question 9

How is energy obtained to drive ATP synthesis?

Answer 9

• High energy electrons in NADH & FADH2 transferred to O2
• release of large amounts of energy

Question 10

What are the 2 processes involved in ATP synthesis?

Answer 10

• Electron Transport
• Oxidative phosphorylation

Question 11

Where does ATP synthesis occur?

Answer 11

Inner mitochondrial membrane

Question 12

Describe the electron transport mechanism, ATP synthesis and oxidative phosphorylation

Answer 12

Electron transport mechanism

• electrons transferred through series of carrier molecules
• energy released use to move H+ across membrane
• H+ gradient across inner mitochondrial membrane (proton motive force) formed

ATP synthesis

• H+ return across membrane via ATP synthase - synthesises ATP

Oxidative phosphorylation

• O2 receives e- and H+ released from NADH and FADH2 and forms water

Question 13

How many proton translocating complex, PTC does NADH and FADH2 use and why?

Answer 13

• NADH : 3
• FADH2 : 2
• electrons in NADH have more energy

Question 14

What regulates oxidative phosphorylation?

Answer 14

Mitochondrial [ATP]

Question 15

What happens when there is high ATP

Answer 15

* High ATP = low ADP

• low ADP, no substrate for ATP synthase
• inward flow of H+ stops
• [H+] in intermembrane space increases
• electron transport stops

Question 16

What are the examples of electron transport inhibitors and what do they do?

Answer 16

• cyanide, CO
• block flow of electrons
• prevent proton motive force

Question 17

What are the examples of uncouplers and what do they do?

Answer 17

• dinitrophenol, fatty acids
• increases permeability of membrane to H+
• H+ enters mitochondria without driving ATP synthetase
• no oxidative phosphorylation

Question 18

What is OXPHOS disease?

Answer 18

• Genetic defect in protein of PTCs and ATP synthase
• decrease in electron transport and ATP synthesis

Question 19

What does the efficiency of coupling of oxidative phosphorylation depend on?

Answer 19

• Tightness of coupling

Question 20

How does brown adipose tissue response to cold?

Answer 20

• noradrenaline released activates lipase
• lipase releases f.a from triacylglycerol
• F.a oxidised and form NADH/FADH2 for electron transport
• UCP 1 activated and transports H+ back into mitochondria

Question 21

What is the role of UCPs?

Answer 21

Heat generation by uncoupling

Question 22

What are the differences between oxidative and substrate level phosphorylation?

Answer 22