carbohydrate metabolism

Question 1

too high blood glucose

Answer 1

release of water from tissues due to osmotic pressure

dehydration and death

Question 2

too low blood glucose

Answer 2

lack of fuel to produce ATP
brain/CNS depend on glucose
red blood cells low on ATP unable to provide oxygen to tissues

Question 3

what regulates blood glucose

Answer 3

insulin
glucagon
adrenaline

Question 4

ratio of blood homrones

Answer 4

more glucagon, less insulin
- release of glucose when blood glucose levels fall
vise versa
uptake of glucose, stored as glycogen

Question 5

sourcseof glucose

Answer 5

diet
glycogen degredation
gluconeoensis
fatty acid oxidation provides energy

Question 6

breakdown of dietary carbs

Answer 6

Breakdown with saliva, a amylase in the saliva/mouth
- breaks down amylose and other components of carbohydrates into a- dextrins
- further broken down by a amylase from the pancreas into oligo/tri saccharides, disaccharides (maltose), isomaltose
- These can be taken up upon the brush border of the small intestine/gut
Maltase and isomaltase can help breakdown maltose in the gut

Sucrase and lactase can break down substituents to allow absorption of the monomers (sucrose)

Question 7

carbs in form of fibre

Answer 7

fibre fermented in gut

gut can absorb as short chain fatty acids

Question 8

sources of glucose during fasting

Answer 8

glucose stores

no dietary carbs being absroed

Question 9

where are glycogen stores

Answer 9

liver

muscles

Question 10

structure of glycogen

Answer 10

branche chains glucose
1-4 alpha glycosidic linkages
branching via the linkages
carbon joined to glycogenin

Question 11

function of glycogen

Answer 11

sore of carb

source of glucose for aTP

Question 12

synthesis of glycogen

Answer 12

• requires energy in form of UTP
• starts of as glucose 1 phosphate combines with UTP
• forms UDP glucose
• glucose is transferred from UDP glucose to the priming protein glycogenein
• glycogen synthase transfers glucose from UDP glucose to growing chain
• this forms a1-4 linkages
• when the 11 residues (glucose molecules) is reached, 6-8 are cleaved off and rejoined by a1-6 linkaged by branching enzyme

Question 13

which enzymes are involeved in glycogen degredation

Answer 13

glycogen phosphoryalse

debranchig enzyem

Question 14

debranching enzyme

Answer 14

acts as transferase removes glucose near branch point

cleaves at branch point

Question 15

glycogen phsophorylase

Answer 15

removes glucose at ends of chains

Question 16

types of deb ranching enzymes

Answer 16

4,4 transferase and a1-6 glucosidase

Question 17

regulation of metabolism in each part

Answer 17

In liver
- glycogen regulates blood glucose levels
- supply glucose to other tissues
in muscle
- responds to changes in energy (ATP) needs
- useful as muscles are high energy, don’t need to wait for energy to be supplied

Question 18

regulation of metabolism in the liver

Answer 18

• Regulated by hormones involved in blood glucose homeostasis, responds to changes in environment to release glucose

Question 19

hormones involved in regulation of liver metabolism

Answer 19

insulin
glycagon
adrenaline

Question 20

regulation of metabolism in muslce

Answer 20

simple feedback-
glycogen supplies glucose for ATP generation
- Low ATP (=high AMP) stimulates glycogen degradation,
- Calcium (indicates muscle fibre activity) and adrenaline also stimulate glycogen degradation

Question 21

disorders of metablism

Answer 21

caused by mutations of enzymes

may only affect liver or muscle enzymes therefore differing severity

Question 22

gluconeogensis

Answer 22

1) fed state taken up into tissues
2) then break down the glycogen
3) gluconeogenesis then slowly increases, to provide energy
produces glucose from non carb sources

Question 23

which pathway will dominate if there is lots of glucose

Answer 23

glycolysis will dominate

Question 24

what regulation is involved in the glycolysis pathway

Answer 24

allosteric regualtion

Question 25

what is fructose 6 phosphate converted into and what enzyme

Answer 25

fructose 1 6 bisphosphate

- phosphofructose kinase

Question 26

regulation of the cnversio of fructose 6 phosphate into fructose 1-6 bisphospahse

Answer 26

• when there is a lot of fructose 6 phosphate there is another enzyme which can generate a different product to speed up the pathway
  fructose 2,6 bisphosphate increases PFK 1 action (glycolysis) and also switches off the F1, 6BP which goes the opposite way (i.e. inhibiting gluconeogenesis)
  -forces reaction in the glycolysis pathway

Question 27

steps undergo if blood glucose drops

Answer 27

1) drop in blood glucose (decrease in insulin and increase in glucagon), tells the body to increase blood glucose level
2) this stimulates the liver to breakdown some glycogen to generate glucose (see glycogen degredation)
3) glucose is released into the blood to reach the tissues requiring it eg brain, RBC
4) RBC can undergo anaerobic respiration producing lactate, which can go back to the liver

Question 28

steps to form energy from fat

Answer 28

2) adipose tossue releases fatty acids in form of lipids
3) Glyerol is also released to the liver to be used as a substrate to form glucose for gluconeogenesis
4) lactate is also substrate for gluconeogenesis (RBC)
5) fatty acids can be burnt in the muscle and liver to generate ATP
6) if starvation is occurring, blood glucose has been low for a while
7) muscle can start to breakdown protein, can be used as a substrate for gluconeogenesis (amino acid) generateing glucose
8) urea is erected through kidney

Question 29

ketone bodies are produced from

Answer 29

acetyl Co A in liver
only produced when gluconeogensis is taking place
- can be converted back into acetyl co A to enter TCA cycle for ATP

Question 30

what occurs during fasting

Answer 30

ketone bodies produced by liver
fuel for Brian and muscl
excess can lead to ketosis

Question 31

ketosis signs

Answer 31

acetone smell on breath