biochemistry 3

Question 1

what is gluconeogenesis

Answer 1

• creation of new glucose

Question 2

where does gluconeogenesis occur

Answer 2

• mainly in liver and Kinsey cortex

Question 3

when does gluconeogenesis occur

Answer 3

• starvation and prolonged exercise

Question 4

what is the point of no return in carbohydrate biochemistry

Answer 4

phosphonolpyruvate —>pyruvate

Question 5

what regulates gluconeogenesis

Answer 5

• pyruvate carboxylase
• phosphoenolpyruvate carboxylkinase
• fructose-1,6-bisphosphatase
• glucose- 6- phosphatase

Question 6

where is glucose-6-phosphate found

Answer 6

liver and ER

Question 7

where is pyruvate carboxylase found

Answer 7

mitochondria

Question 8

where is phosphoneolpyruvate carboxylkinase

Answer 8

cytosol

Question 9

what are the precursors of gluconeogenesis

Answer 9

• lactate - skeletal muscles
• amino acids - skeletal muscles or food
• glycerol - adipose tissue

Question 10

when is gluconeogenesis activated

Answer 10

• low energy stores
• low carbohydrate intake

Question 11

what causes a fructose-1,6-bisphosphate deficiency and what does it cause

Answer 11

• autosmal reccesive disorder
• mutation in FBP1
• reduce gluconeogenesis leads to hypoglycaemia

Question 12

what does gierke disease cause - type 1- glycogen storage disease

Answer 12

• decreased glucose-6-phosphate in liver or low endoplasmic reticulum uptake
• increased liver glycolysis –> increased blood lactate and pyruvate

Question 13

what are the symptoms of type 1 - glycogen disgorge disease - gierke disease

Answer 13

• hyperglycaemia between meals
• enlargement of liver
• no raise in blood glucose with epinephrine and glucagon
• increases fat metabolism

Question 14

what ethanol metabolism 1

Answer 14

Ethanol —> acetaldehyde by alcohol dehydrogenase

acetaldehyde –> acetate by aldehyde dehydrogenase

• both produce NADH

Question 15

how does increased NADH decrease gluconeogenesis

Answer 15

1) lactic acid build up
2) amino acids converted to pyruvate
3) glycerol converted to glyceraldehyde-3-phosphate
4) oxaloacetate converted to malate
- causes lactic acidosis, fatty liver, hyperglycaemia

Question 16

how does fatty liver develop

Answer 16

• from glyceraldehyde-3-phosphate –> lipids

Question 17

how does alcoholic hepatitis occur

Answer 17

liver cells die resulting in inflammation

Question 18

how does cirrhosis occur

Answer 18

• scar tissue forms
• not able to convert ammonia into urea
• rise in blood ammonia
• neural toxicity

Question 19

what causes alcoholic flush

Answer 19

• dominant causing allele
• higher protein degradation
• acetaldehyde build up
• overactive ADH

Question 20

what are the naturally occurring glycosidic links

Answer 20

1,2
1,4 - linear
1,6 - branched

Question 21

what is the structure importance of glycogen

Answer 21

• glycogen spheres
• large amount of glucose
• short glucose chains - soluble
• less water interacting

Question 22

glucose-6-phosphate to glucose-1-phosphate

Answer 22

phosphoglucomutase

Question 23

what converts glucose-1-phosphate to UDP-glucose

Answer 23

• UDP glucose pyrophohorylase
• UPT –>PPI

Question 24

what are the stages of glycogenesis

Answer 24

• starts with glycogenin
• transfer of glucose from UDP-glucose
• autocatalysis - 6-7 units
• glycogen synthase recruited and further elongation
• branching induced by branching enzyme from 1,4 to 1,6

Question 25

what is ethanol metabolism 2

Answer 25

ethanol --> acetaldehyde by MEOS - microsomal ethanol-oxidising system

Question 26

what are the stages of glycogenolysis

Answer 26

1) glycogen phosphorylase breaks down q,4 bonds and glucose-1-phosphate released 2) debranching enzymes - 1,6 residues hydrolysed tp glucose and truncate branch to 1,4 chain 3) phosphoglucomutase - isomerism glucose-1-phosphate to glucose-6-phosphate

Question 27

what does glycogen synthase do

Answer 27

- promotes glycogen synthesis - covalent modification pf insulin ang glucagon - glucagon signalling --> phosphorylated - inactive - insulin signalling --> dephosphorylated - active

Question 28

what does glycogen phosphorylase do

Answer 28

- promotes glycogen degradation - allosteric control of muscle and liver - glucose, ATP and glucose-6-phosphate inhibited and AMP activated - covalent modification of insulin and glucagon glucagon - active insulin - inactive

Question 29

what causes type 2 glycogen storage disease (Pompe disease) and what are the symptoms

Answer 29

- mutation of alpha 1,4 glucosidase - lysosomal enzyme - enlargement of the liver and proximal muscle weakness causing cardiorespiratory failure and death before 2

Question 30

what causes type 3 glycogen storage disease (cori disease ) and what are they symptoms

Answer 30

- mutation of amyloid-1,6-glucosidase - hyperglycaemia, enlargement of liver, no rain in blood glucose with epinephrine and glucagon - increase fat metabolism

Question 31

what causes type 5 glycogen storage disease (McArdle disease) and what are the symptoms

Answer 31

- mutation in muscle glycogen phosphorylase activity making it absent - increased creatine phosphate breakdown - short exercise causes fatigue, muscle pain and cramps