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GI system > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

What is the role of glycogen as an energy store?

A

Liver glycogen - broken down in-between meals to maintain blood glucose levels
muscle glycogen - provides energy via glycolysis

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2
Q

How can glucose residues be added to a glycogen chain?

A

can only be added to an existing glycogen chain with a primer being used that is attached to a protein called (glycogenin)

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3
Q

What is UDP-glucose?

A

activated form of glucose and can synthesise glycogen from it

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4
Q

How is glycogen cleaved to produce glucose?

A

glucose 1 phosphate is converted to glucose 6 phosphate that can be dephosphorylated in the liver and released into the blood stream

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5
Q

Define glycogenesis, glycogenolysis and gluconeogenesis

A

synthesis of glycogen from glucose

breakdown of glycogen to form glucose

de novo synthesis of glucose from metabolic precursors

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6
Q

How can new glucose be synthesised during prolonged starvation?
(study summary on notion)

A

lactate - skeletal muscle
amino acids - muscle protein
glycerol - triglycerides

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7
Q

What is the general structure of triglycerides

A
  • glycerol and 3 fatty acids
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8
Q

General structure of fatty acids?

A

mainly straight chains can have double bonds or no double bonds

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9
Q

What is the difference between plant fats and animal fats

A

Plant fats are unsaturated = liquid

animal fats are solid.

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10
Q

What are the main products of fat digestion?

A

glycerol, fatty acids and monoglycerides

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11
Q

What are the products of beta oxidation?

A

1 acetyl coA, 1FADH2, 1 NADH and H+ and 1 fatty acid acyl CoA, shortened by 2 carbon atoms

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12
Q

What condition must be filled in order to oxidise fatty acids?

A

converted into CoA derivatives to be transported to cell matrix

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13
Q

Where are ketones formed and why are they important?

A

liver mitochondria and important in energy metabolism for heart muscle and renal cortex - diffuse into peripheral tissues

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14
Q

Why are ketones important in starvation or diabetes?

A

oxaloacetate is consumed for gluconeogensis
Acteyl CoA is converted into ketone bodies which if present in high levels in the blood cause severe acidosis
smell of acetone can be detected in breath

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15
Q

Describe the process of synthesising new triglycerides from citrate (from the TCA cycle)

A

citrate transports acetyl group into cytoplasm, Acetyl CoA is activated to malonyl CoA (caroxylase) , this then turns into fatty acyl CoA which turns into triglycerides (esterification)

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16
Q

How is nitrogen excreted (degradation of proteins)

A

urea, uric acid and creatinine - exerted ammonium is toxic at high concentrations

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17
Q

what are major carriers of nitrogen in the blood to liver?

A

alanine and glutamine

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18
Q

What is the carbon skeleton left over after alpha amino group is removed used for?

A

converted to glucose or oxidised in the TCA cycle

19
Q

Describe the pathway of glycogen synthesis

A

Glucose to glucose 6 phosphate (catalysed by hexokinase) then to glucose 1 phosphate (phosphglucomutase) then UDP glucose (UDP=glucose pyrophosphorylase) then to glucose (glycogen synthase)

20
Q

What are some limitations of glycogen synthase?

A

adds one glucose molecule to glycogen at a time, only extend chains and not introduce branches (UDP glucose is rate limiting enzyme)

21
Q

What catalyses glycogenolysis?

A

Glycogen phosphorylase - rate limiting step… (breakdown of glycogen to glucose 1 phosphate)

22
Q

where does gluconeogensis take place?

energy is from what? released from where?

A

usually in the liver and the energy is from oxidation of fatty acids released from adipose tissue

23
Q

How does gluconeogenisis proceed?

A

via the synthesis of oxaloacetate in mitochondria - TCA cycle intermediate that accepts acetyl intermediates which is important for accepting acetyl groups in fat breakdown

24
Q

What is the product of gluconeogensis

A

glucose, 4ADP, 2GDP, 6phosphate, 2NAD+ and 2 protons

25
Q

Why is the cori cycle useful?

A

buys time and shifts metabolic burden from muscle to other organs

26
Q

What hormones are useful in the control of glycolysis and gluconeogenisis

A

glucagon - inhibits glycolysis

insulin - inhibits gluconeogensis

27
Q

What is the products of amino acid degradation

A

Produces amonia and ammonium ions - NH4+ is toxic at high concentrations, build up leads to severe problems

28
Q

How is urea synthesised?

A

ammonium ions and aspartic acid

29
Q

What is the product of producing urea

A

urea, 2ADP, AMP and fumarate (plus others)

30
Q

what are the two functions of ketogenic and glycogenic amino acids?

A

degraded to acetyl COA

degraded to pyruvate or TCA cycles

31
Q

What is the treatment for excess ammonia in the blood

A

low protein diet - or use drugs that are involved in the removal of nitrogen

32
Q

what are lipids?

A

Collection of different compounds - simple, compound or steroids

hydrocarbon, insoluble in water and contain long chain fatty acid

33
Q

What is the threshold of fatty acids at room temperature for the state it is in?

A

up to 8Carbons are liquid at room temp but longer ones are solid

34
Q

What happens to chylomicrons?

A

attacked and cleaved by lipoprotein lipases, synthesised into triglycerides or to provide energy

35
Q

What is the carnitine shuttle?

A

used to transport acetyl across the cell membrane

36
Q

What is required for the breakdown of glycerol?

A

Activated to glycerol 3 phosphate by glycerol kinase and then dehydrogenated to dihydroxyacetone phosphate

37
Q

where does beta oxidation take place?

A

Mitochondrion

38
Q

Where does fatty acid synthesis take place

A

Mainly in cytoplasm of liver, takes place during excess energy intake

39
Q

Why are elecrons required in lipgenesis?

A

It is a reductive process

40
Q

Why is citrate useful in lipogenesis?

A

Transports actyl groups into cytoplasm

41
Q

What is the longest fatty acid released ?

A

palmitic acid (C16) is the longest fatty acid created by fatty acid synthase

42
Q

What enzyme regulates the conversion of acetyl CoA to Malonyl CoA?
What are the

A

acetyl CoA carboxylase

43
Q

What are the regulatory components included in Acetyl CoA carboxylase

A

insulin - signals fed state
glucagon - signals starved state
Epinephine - requirement for energy

citrate stimulates allosterically - levels are high when acetyl-CoA and ATP are abundant

antagonised by palmitoyl-CoA

44
Q

What does the synthesis of triglycerides require?

A

glycerol 3 phosphate from liver, adipose tissue(fed state)

GI system (8 decks)

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