Metabolic Stores

Question 1

how are carbohydrates stored in the liver and muscle

Answer 1

glycogen (a branched glucose polymer)

Question 2

when glucose is broken down what is it directly converted to

Answer 2

glucose-6-P and this is without consuming ATP
CAN ONLY OCCUR IN THE CELL IT IS FORMED
as it cannot easily pass through the cell membrane

Question 3

what happens when glucose is required somewhere else in the body

Answer 3

the glucose-6-P is only phosphorylated when it has been transported to its destination as once phosphorylated it is not easily removed
THIS USES ATP
in the liver there is an enzyme known as glucose-6-phosphotase which can cleaves the phosphates it can escape

Question 4

how may horse worth of glycogen in the body

Answer 4

3-5 hours

Question 5

what is the major form in which fuel is stored

Answer 5

lipids

Question 6

triglycerides/triacylglycerols

Answer 6

produce about 6 times s much energy as glycogen

Question 7

what is fat mainly stored as

Answer 7

triglycerides (triacylglycerols) these are esters of glycerol and fatty acids
as esterification occurs at carbon 123

Question 8

what is an ester

Answer 8

formed by reaction of an alcohol with an organic acid

Question 9

tell me about the oxidisation of fatty acids

Answer 9

they are linked to coenzyme A before they are oxidised and 2-carbon fragments cleaved off (as acetyl-Co-A)

Question 10

What happens during the oxidisation of fatty acids

Answer 10

no ATP is directly generated however hydrogen and electrons are removed and are passed along the respiratory chain so are indirectly producing ATP

Question 11

where are fatty acids and glycerol released from

Answer 11

adipose tissue and are mainly metabolised in the liver

Question 12

when there are no other fuels available, the breakdown of fatty acids leads to what

Answer 12

the formation of chemicals known as ketone bodies

Question 13

what ketone bodies are mainly present post breakdown of fatty acids

Answer 13

acetoacetate
3-hydroxybutyrate
acetone

Question 14

how are ketone bodies produced

Answer 14

acetyl-CoA formed in the breakdown of fatty acids cannot enter the citric acid cycle since oxaloacetate becomes depleted because the liver converts it to pyruvate to produce glucose by glycogenesis
so acetyl-CoA = ketone bodies

Question 15

omega-3 fatty acids

double bond at three position

Answer 15

not metabolised
has to be acquired in the diet
vital fatty acid

Question 16

What is the appearance of ketone bodies

Answer 16

fruity smell (often smelled on breath when fasting.)

Question 17

what happens to amino acids not needed for making new proteins as they cannot be stored

Answer 17

they are used as metabolic fuel
some can be deaminated, yielding nh4 + a ketone acid that are intermediates of the glycolytic pathway or of the citric acid cycle

Question 18

what happens to the products of transamination

Answer 18

the resulting ketone acids can be fed into glycolysis or the citric acid cycle (as pyruvate , acetylene-Co-A, oxalocetate

Question 19

what happens to the NH4+ formed from transamination

Answer 19

rapidly converted to urea as it is very toxic

Question 20

gluconeogenesis

Answer 20

formation of glucose from non-carbohydrate sources )glycerol and the carbon backbone of amino acids can be fed into this pathway)

Question 21

where does the bulk of gluconeogenesis take place

Answer 21

the liver

Question 22

where are the bulk triglycerides stored

Answer 22

adipose tissue

Question 23

why do athletes load up on carbs before an event

Answer 23

fats are not used as effectively as fuel carbohydrate so energy production cannot be as high when using lipids rather than carbs
(when fasting, burns fat so produces more keto bodies hence fruity breath)

Question 24

tell me about fuel in the brain

Answer 24

glucose is normally only source
can’t store glucose glycogen so needs constant supply in the blood
60% of all glucose used by the body
in times of starvation can use ketone bodies)acetoacetate and 3-hydroxybutyrate) formed in other tissues
CANT USED FATTY ACIDS due to BBB that protects the brain from other potentially dangerous chemicals

Question 25

what stores can muscle (large glycogen stores) use

Answer 25

glucose, fatty acids and ketone bodies

Question 26

resting muscle uses

Answer 26

fatty acids

Question 27

tell me about the actions in muscle

Answer 27

glucose-6-P is formed from glycogen
Like brain, muscle cannot convert this to glucose, so
neither tissue can export glucose
When muscle is active the rate of glycolysis far outpaces the
citric acid cycle
pyruvate must be converted to lactate
The lactate passes into the blood and to the liver, where it is converted back to glucose

Question 28

under conditions where muscle protein is being broken down

Answer 28

amino acids pass their amino group pyruvate (through transamination) to form alanine

Question 29

role of alanine

Answer 29

enters the blood and in the liver can be converted back to pyruvate which is used to synthesise glucose

Question 30

main function of adipose tissue

Answer 30

to synthesize and store triglycerides (=triacylglycerols) and release fatty acids and glycerol in times of need

Question 31

what is the role of lipase

Answer 31

hydrolyses triglycerides and is HORMONE SENSITIVE

Question 32

What determines the rate at which fatty acids are esterified

Answer 32

the availability of glucose

Question 33

tell me about the role of the liver

Answer 33

the hepatic portal system ensures that the liver has ready access to nutrients absorbed by the gut.
readily store, release glucose and make new glucose from lactate, alanine and glycerol in the diet or released by other tissues.

Question 34

what is the formation of glucose known as

Answer 34

gluconeogenesis

Question 35

When fuel supplies are available what does the liver do

Answer 35

synthesizes fatty acids, esterifies them and then secretes them into the blood as very low density lipoprotein (VLDL)