metabolic stores

Question 1

where is glycogen stored in the body?

Answer 1

liver and skeletal muscles

Question 2

how many hours of moderate exercise is the store of glycogen sufficient for?

Answer 2

3-5 hours

Question 3

what is the main source of alternative fuel stores in the body?

Answer 3

triglycerides

Question 4

what is the structure of one molecule of triglyceride?

Answer 4

one glycerol and three fatty acids joined by esterification reaction

Question 5

what type of enzymes break down triglycerides into glycerol and fatty acids?

Answer 5

lipases

Question 6

what happens to the glycerol that is released during this process?

Answer 6

it is used in glycolysis to produce pyruvate

Question 7

what happens to the fatty acids that are released by the lipase enzymes from the triglycerides?

Answer 7

the fatty acids are linked to coenzyme A, they are then oxidised to remove 2 carbon acyl units from the fatty acids which are used as acetyl coA in the citric acid cycle

Question 8

whereabouts in the body are fatty acids mainly metabolised?

Answer 8

in the liver

Question 9

what happens to the electrons that are passed from the fatty acids when they are oxidised?

Answer 9

they are passed along the respiratory chain, indirectly reducing ATP

Question 10

when no other fuels are available, why does the breakdown of fatty acids lead to the formation of ketone bodies?

Answer 10

because oxaloacetate levels are depleted and therefore cannot be combined with the acetyl coA from fatty acid breakdown. The acetyl coA is therefore converted to ketone bodies.

Question 11

what are the three main ketone bodies?

Answer 11

acetoacetate, 3-hydroxybutyrate and acetone

Question 12

why is oxaloacetate depleted when there are no other fuels available?

Answer 12

because the liver converts it to pyruvate to produce glucose.

Question 13

what happens to amino acids in the diet that are not required for building new protein?

Answer 13

they are used as a metabolic fuel

Question 14

what happens when an amino acid is DEAMINATED?

Answer 14

its amino group is removed to produce NH4 and a keto acid that can be used in the citric acid cycle or in glycolysis

Question 15

what happens to amino acids that cannot release their amine group as NH4?

Answer 15

TRANSANIMATION: they pass their amino group to a keto acid which can then be deaminated, and they are covered to a veto acid which can be used in glycolysis or citric acid cycle

Question 16

what happens to the NH4 which is produced during TRANSAMINATION?

Answer 16

it is broken down to form urea in the kidneys and excreted

Question 17

what is GLUCONEOGENESIS?

Answer 17

the formation of glucose from non-carbohydrate sources

Question 18

what substrates can be used for gluconeogenesis?

Answer 18

glycerol, amino acids (Alanine), lactate and pyruvate

Question 19

where does glycerol come from for lipid synthesis?

Answer 19

glycerol can be made from glucose through GLYCOLYSIS

Question 20

where do fatty acids come from for lipid synthesis?

Answer 20

two carbon acyl units from acetyl CoA (from pyruvate) are linked together to form fatty acids by fatty acid synthetase

Question 21

where are triglycerides mainly stored in the body?

Answer 21

in adipose tissue

Question 22

what is the type of fuel most efficient for the body to use?

Answer 22

carbohydrate

Question 23

what is the largest source of MOBILISABLE proteins in the body?

Answer 23

muscle

Question 24

what is the only fuel the brain can use?

Answer 24

glucose

Question 25

can the brain store glucose or glycogen?

Answer 25

no - needs a constant supply

Question 26

what other alternative fuel can the brain use in times of need?

Answer 26

ketone bodies

Question 27

what prevents the brain from using fatty acids for fuel?

Answer 27

the blood brain barrier

Question 28

what type of fuel does resting muscle mainly use?

Answer 28

fatty acids

Question 29

what fraction of the bodies overall glycogen store does skeletal muscle contain?

Answer 29

3/4

Question 30

why does skeletal muscle inly use glucose-6-phosphate?

Answer 30

it cannot break glucose-6-phosphate down so cannot export glucose

Question 31

what happens to the extra pyruvate produced in muscle, because the rate of glycolysis far outpaces the citric acid cycle?

Answer 31

the pyruvate is converted t lactate (to regenerate NAD+). The latte is converted back to glucose in the liver.

Question 32

when muscle protein is being broken down, what do many amino acids do in skeletal muscle?

Answer 32

many amino acids pass their amino group to pyruvate to form alanine which can then be converted to glucose in the liver

Question 33

where is the main location where triglycerides are synthesised?

Answer 33

adipocytes

Question 34

what determines the rate at which triglycerised are synthesised?

Answer 34

the availability of glucose

Question 35

what is the activity of lipase (that breaks down triglycerides) dependant on?

Answer 35

hormone dependent

Question 36

which portal system ensure the liver has ready access to nutrients absorbed from the gut?

Answer 36

the hepatic portal system

Question 37

when fuel stores are available, what can the liver synthesise and release fatty acids as?

Answer 37

very low density lipoprotein (VLDL)