Bioenergetics

Question 1

What is the order of energy released during combustion and metabolism?

Answer 1

Combustion: carbohydrates (least) - protein - alcohol - fat (most)
Metabolism: alcohol (least) - fat - protein - carbohydrates (most)

Question 2

Whys do carbohydrates release more energy in metabolism than combustion?

Answer 2

Metabolism is a controlled oxidative process where OH groups can be broken down but C-C bonds are not easy to access so energy release (from fats) is not as large

Question 3

Can fat be metabolised without oxygen?

Answer 3

no

Question 4

What aspects of the structure of ATP allow it to work better?

Answer 4

Mg2+ ion changes ATP shape to 3D and allows greater attraction of phosphate groups. Also increases energy of ATP 3-fold as it gives the phosphate group a push during hydrolysis which generates more power
Adenosine also push electrons in one direction along the phosphate chain which gives the chain more energy

Question 5

What is the difference between hexokinase and glucokinase?

Answer 5

Hexokinase has a higher affinity than glucokinase for glucose. Glucokinase is present in the liver and will only take up glucose if there is a high concentration in the blood

Question 6

What three reaction types are there in the metabolism of fuels?

Answer 6

Rearrangement (isomerisation)
Condensation (splitting)
Oxidation/reduction

Question 7

What is glycolysis?

Answer 7

Breakdown of glucose (6C) to 2x pyruvate (3C)

Also produces 2 ATP (net) + 2NADH

Question 8

What are the two phases of glycolysis?

Answer 8

Energy investment phase and energy payoff phase

Question 9

What are the three irreversible steps in glycolysis?

Answer 9

Reaction 1 - hexokinase/glucokinase (phosphorylates glucose and traps it in the cell, 1ATP required)
Reaction 3 - phosphofructokinase (commitment stage, 1ATP required. F6P converted to F1,6BP)
Reaction 10 - pyruvate kinase (produces 2ATP)

Question 10

What is PFK regulated by?

Answer 10

High ATP, citrate and pH

Question 11

What are the anaerobic products of respiration?

Answer 11

Lactate, 2NAD+ and 2ATP

lactate is formed to regenerate NAD+ from NADH

Question 12

How is lactate produced and why?

Answer 12

In the absence of oxygen, NADH is not reconverted and NAD+ runs out.
Lactate dehydrogenase produces lactate from pyruvate and reforms NAD+ in the absence of oxygen

Question 13

Why is lactate buildup painful?

Answer 13

Lactate is not acidic but it reacts with nociceptors. Pyruvate is acidic in cells and when ATP breaks down to ADP, H+ is released

Question 14

What is the Cori cycle?

Answer 14

Process in the liver that regenerates glucose from lactate released by the muscles (6ATP required)