Revision questions - week 2

Question 1

glucose converted to ATP by

Answer 1

glycolysis

acetyl coa

Question 2

triglycerides converted to ATP by

Answer 2

lipolysis
- broken down into free fatty acids and glycerol
beta oxidation

Question 3

protein converted to ATP by

Answer 3

deamination (removal of amine group from carbon skeleton)

Question 4

ethanol converted to ATP by

Answer 4

alcohol dehydrogenase ->acetaldehyde - >acetyl Coa enters TCA cycle and turns to ATP

Question 5

ATP yield of protein

Answer 5

no yield

Question 6

ATP yield of glucose

Answer 6

38ATP

Question 7

ATP yield of triglycerol

Answer 7

30 ATP

Question 8

ATP yield of ethanol

Answer 8

5 ATP

Question 9

Explain each pathway in dot points, ensuring that you name the 
key steps with substrate and product 


Answer 9

Metabolic pathways
Anabolic pathways
Catabolic pathways

Question 10

What molecule sits at the crossroad of energy metabolism? 


Answer 10

Acetyl CoA

Question 11

What are ketone bodies

Answer 11

a molecule formed out of two acetyl coa when there is access in the liver, used in muscle, heart, brain

Question 12

How/where are ketone bodies formed?

Answer 12

formed in liver from breakdown of fatty acids during periods when fat is the primary source of energy

Question 13

How/where are ketone bodies used?

Answer 13

in extra hepatic tissues

Question 14

ketosis

Answer 14

a state with raised ketone bodies in the blood

Question 15

ketoacidosis

Answer 15

is a metabolic state associated with high concentrations of ketone bodies (life threatening condition - complication of type 1 diabetes)

Question 16

pathway of gluconeogenesis

Answer 16

Gluconeogenesis starts from oxaloacetate -> Oxaloacetate is formed from glucogenic amino acids carbon backbones( GGAACB), e.g. not fatty acids, or pyruvate -> Pyruvate is formed from glucose or GGAACB, not fatty acids -> Fatty acids are oxidised to acetyl-coA (2 carbons molecules) -> Acetyl coA cannot be converted back to pyruvate (irreversible reaction) -> Acetyl coA enters the CAC to form citrate with oxaloacetate. The CAC is an open cycle /circuit, meaning that the intermediates are formed from a variety of substrates coming from other pathways, and carbons atoms are lost all along as CO2 -> Therefore the acetyl coA 2 carbons do not “exist” by the time oxaloacetate is formed.

Question 17

Describe the metabolic “shifts” that occur in substrate utilisation for energy production, for maintenance of blood glucose level, and for sparing lean body mass when fasting from a few hours to several days

Answer 17

• ATP production relies on glycogen stores then lean body mas then fat stores and ketone bodies
• Maintenance of BGL – glucose used up, then use liver glycogen, then lean body mass is used in gluconeogenesis to continue supply of BGL.
• Long period of fasting result in using ketone bodies as primary energy source
  therefore body does not need to provide as much glucose and can spare lean body mass from being used for gluconeogenesis

Question 18

Key factors and their roles in the regulation of energy metabolism

Answer 18

• Liver – most reactions take place
• Substrate availability dictates whether anabolic or catabolic
• ATP levels determine activity of AMPK and whether catabolic states are activated
• Enzymes are necessary for reactions
• Hormones dictate whether anabolic (insulin) pathway or catabolic (glucagon) pathway
• Vitamins and minerals necessary for transfer of ions (NAD and FAD) and act as cofactors to metabolism enzymes

Question 19

Can typical fatty 
acids be used as substrate for gluconeogenesis? Why? Why not? 


Answer 19

• cannot make glucose out of fatty acids
• because the carbons in acetyl acetate are not the same carbons in acetyl coA (lost during the period), it is an open cycle, needs to come from an outside substrate

Question 20

Substrates(a) Intermediates(b) Products(c)

Answer 20

a) Compounds at the start of the pathway

b) Compounds formed throughout a pathway c) Compounds resulting from the pathway

Question 21

metabolic pathway

Answer 21

• biochemical reaction occur in progression from substrate to product, usually involving enzymes and cofactors
• Niacin and riboflavin help transfer hydrogens from energy-yielding compounds to oxygen

Question 22

Anabolic pathway

Answer 22

– Pathways that build molecules and use energy (ATP)

- AA, sugars, FAs, glycerol ->proteins, glycogen, triglycerides and other lipids

Question 23

Catabolic pathway

Answer 23

– Pathways that break down substrates and produce energy (ATP)
- protein, CHO, fat -> CO2, H2O, NH3