energy storage- glycogen and fat

Question 1

where is glucose a required substrate and why

Answer 1

in RBC- no mitochondria, in neutrophils- mitochondria specialised for respiratory burst, middle kidney medulla cells- deep in centre, poor blood supply, lens of the eye- not many blood vessels so we can see. all these cells rely on anaerobic glycolysis

Question 2

what is hypoglycaemia

Answer 2

+8.0mmol. common in diabetics, no insulin/ don’t respond to it. affects the microvasculculture so when ulcers develop on foot they don’t notice, becomes infected and they need it amputated

Question 3

what is hyperglycaemia

Answer 3

2.8-0.6 mol. leads to confusion and even brain damage and death as brain requires glucose and can only make 50% use of ketone bodies

Question 4

what do glycogen stores look like under microscope, where is it stored

Answer 4

they are black granules found in muscle and liver

Question 5

what is the glycogen structure

Answer 5

has branched structure due to the 1,6 glycosidic bonds ever 25 monomers. in the centre there is a dimer protein called glycogenin which the glycogen polymers are attached to

Question 6

what are the advantages of glycogen being branched

Answer 6

multiple points where enzymes can release glucose form and it doesnt have an osmotic effect on cell being stored in one structure like it would if they were monomers

Question 7

explain the process of glycogenesis (build up)

Answer 7

build up of glycogen. adding phosphate group to glucose using ATP and enzyme hexokinase to make G6P. converted to G1P via phosphoglutamase. then G1P added to UTP and water to make UDP glucose and PPi. Add UDP glucose to glycogen to extent it by 1 glucose molecule. UDP given off. keep doing this to extend by 1 monomer.

Question 8

name the enzymes used to add UDP glucose to glycogen in glycogenesis

Answer 8

glycogen synthesis adds a monomer with a 1,4 bond and branching enzyme adds a glucose with a 1,6 monomer

Question 9

explain glycogenolysis (degradation)

Answer 9

add a phosphate to glycogen to form G1P and glycogen with on less glucose. catalysed by glycogen phosphorylase or de-branching enzyme. G1P is then converted to G6P by phosphoglutamase.

Question 10

what happens to G6P when it enters the muscle

Answer 10

enters glycolysis. no way of G6P being converted back to glucose so can’t leave the muscle. this is because it lacks the glucose 6 phophotase enzyme

Question 11

what happens to G6P when it enters the liver

Answer 11

converted to glucose and enters plasma via a GLUT transporter. conversion catalysed by the enzymes glucose 6 phosphatase.

Question 12

which transporters are used to get glucose in and out of the muscle and the liver from the blood

Answer 12

GLUT 4 transports glucose into the muscle and GLUT 2 transports glucose in and out of the liver

Question 13

how are enzymes in the process of glycogenolysis and glycogeneisis regulated

Answer 13

glucagon/ adrenaline stimulate glycogen phosphorylase and inhibit glycogen synthase. insulin inhibits glycogen phosphorylase and stimulate glycogen synthase

Question 14

which enzyme is activated by AMP and why

Answer 14

glycogen phosphorylase because when ATP low means need more glucose for production of energy

Question 15

why does glucagon have no effect on muscle - can’t get glucose to be released into the blood

Answer 15

because muscles do not have glucagon receptors

Question 16

what is von gierkes

Answer 16

G6Phosphatase deficiency where can’t relate gycogen from liver. leads to hepatomegaly

Question 17

what is mcardle disease

Answer 17

muscle glycogen phosphorylase deficiency where get very tiered when exercising because no energy for muscle contraction

Question 18

when does gluconeogenesis take place

Answer 18

8 hours into starving this process happens when glycogen stores are used up

Question 19

what are the precursors of gluconeogeneis

Answer 19

lactate (from anaerobic respiration), glycerol (from adipose break down) and amino acids

Question 20

why is lactate an important precursor for the muscle

Answer 20

because lactate enters the cori cycle where it is taken to the liver and broken down to glucose and then travels back to the muscles where it can be used again

Question 21

draw out the entry points of the precursors in gluconeogensis and add in the relevant enzymes

Answer 21

enzymes include PEPCK, fructose 16 bisphosphate and glucose 6 phosphate

Question 22

how are fructose 1,6 bisphophate and PEPCK regulated

Answer 22

glucagon and cortisol stimulate these enzymes because need new glucose whereas insulin inhibits these enzymes because already got enough glucose

Question 23

time course of the utilisation of these process’

Answer 23

glucose can be used for 2 hours, then glycogen stores last up to 10 hours after this and then over this glujconeogeneis is used

Question 24

how is lipid stored

Answer 24

lipid droplet with TAG/cholesterol in it. organelles found at edge of cytoplasm. more fat = more fats cells = easier to regain weight because fat cells have already divided

Question 25

how fat is metabolised

Answer 25

broken down in small intestine by pancreatic lipase into fatty acids and glycerol. absorbed by epthithelal cell and then carried into the lymph via a chylomicron. enters blood stream at left subclavian vein and is then either stored in adipose tissue or is utilised in the tissue to produce energy

Question 26

how is adipose tissue metabolised

Answer 26

its release is stimulated by glucagon and adrenaline and it is carried to tissue by albumin to be converted to energy

Question 27

explain lipogenesis (lipid synthesis)

Answer 27

occurs in liver. glucose is converted to pyruvate by glycolysis and then converted to citrate and acetyl co A in the mitochondria. citrate is then converted to acetyl co A in the cytoplasm and this is converted to mayor coA (3C). in a fatty acid complex manoyl co A and NADPH from the pentose phosphate pathway and synthesis of maleate is used to add 2 carbons to the fatty acid tail attached to the glycerol. co2 is given off from manoyl co A (DRAW)

Question 28

how is TAG transferred outside the cell once it is synthesised

Answer 28

transferred by very low density lipoprotein

Question 29

explain lipolysis

Answer 29

TAG is related from adipose by hormone sensitive lipase. it enters the blood as glycerol and fatty acids . goes to the liver for glycogenesis and with an albumin to the muscle where it undergoes beta oxidation and is used as energy

Question 30

how is the release of TAG from adipose regulated

Answer 30

glucagon/ adrenaline activate HSL (hormone sensitive lipase) to break down TAG and insulin inhibits its break down.

Question 31

where are fats lipids stored in the body

Answer 31

as liver glycogen, muscle glycogen, muscle protein and as TAG. most of it is stored as TAG and is the only store that will increase when you gain weight.

Question 32

differences between fatty acid synthesis and beta oxidation (fatty acid metabolism)

Answer 32

beta oxidation; occurs in mitochondria, is oxidative (produces NADH) and is inhibited by insulin.
Fatty acid synthesis; occurs in cytoplasm, is reductive (requires NADH) and is stimulated by insulin

Question 33

clinical consequences of glycogen storage diseases

Answer 33

liver/muscle damage, excess glycogen storage leads to tissue damage, hypoglycaemia and poor exercise tolerance

Question 34

why is TAG an efficient energy storage molecule in adipose tissue

Answer 34

hydrophobic (stored in anhydrous form n adipose tissue)

efficient energy storage molecule

prolonged exercise, stress, starvation, during pregnancy

storage/mobilisation under hormonal control