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1st year GI > biochemistry > Flashcards

biochemistry Flashcards

1
Q

what is glycogenesis

A

synthesis of glycogen from glucose

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2
Q

what is glycogenolysis

A

breakdown of glycogen to form glucose

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3
Q

what is gluconeogenesis

A

de novo synthesis of glucose from metabolic precursors

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4
Q

where is glycogen stored

A

liver and muscle cells

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5
Q

how is liver glycogen broken down

A

broken down between meals and released to maintain blood glucose levels for red blood cells and the brain

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6
Q

how does muscle glycogen provide energy

A

Provides energy via glycolysis and the TCA during bursts of physical activity

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7
Q

what is the primary source of glucose over night when hepatic glycogen is depleted

A

gluconeogenisis

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8
Q

what is the structure if glycogen

A
  • polymer consisting of glucose molecules
  • joined by alpha 1-4 glycosidic links
  • branches are introduced by alpha 1-6 glycosidic links
  • glycogenin is an enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first few glucose molecules
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9
Q

what is a glycogenic protein

A

A primer of straight chain polymer. Contains at least 4 glucose residues

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10
Q

what is the function of hexokinase in glycogen synthesis

A

Primer for glucose phosphorylation

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11
Q

what is the function of phosphoglucomutase in glycogen synthesis

A

targets glucose away from glycolysis and towards glycogen synthesis by changing the position of the phosphate from group 6 to group 1

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12
Q

what is the function of UDP-glucose pyrophosphorylase in glycogen synthesis

A

Binds UDP to the glucose

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13
Q

what is the function of the glycogen synthase

A

Attaches UDP-glucose as a primed molecule to form glycogen. It adds one glucose molecule to glycogen at a time. It can only extend the glycogen chains and it cannot start new molecules

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14
Q

what is UDP-glucose

A

An activated form of glucose

  • UDP-glucose is used in nucleotide sugar metabolism as an activated form of glucose
  • precursor of glycogen
  • precursor of sucrose, lipopolysaccharides and glycosphingolipids
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15
Q

what are the steps of glycogenolysis

A

Steps of glycogenolysis (glycogen breakdown)

  1. glycogen is broken down Inyo glucose-1-phosphate by the enzyme glycogen phosphorylase
  2. glucose-1-phosphate is broken down into glucose-6-phosphate by the enzyme phosphoglucomutase

3a. liver = glucose-6-phosphate is converted to glucose by the enzyme glucose-6-phosphatase which will travel into the blood via GLUT2 transporter
3b. muscle cells = glycolysis

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16
Q

where does glycogenolysis occur

A

the muscles and the liver

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17
Q

when is glycogenolysis important

A
  • In starved state

- When ATP is low

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18
Q

what is the difference between glycogenolysis in the liver and in the (skeletal) muscle

A

in the liver the glucose-6-phosphate can be de-phosphorylated and the resulting glucose released into the blood stream

in muscle glucose-6-phosphate cannot be de-phosporylated by instead is used to provide energy via glycolysis and the TCA cycle

19
Q

when does gluconeogenesis occur

A
  • During prolonged starvation, new glucose has to be synthesised
  • Proceeds via the synthesis of oxaloacetate in mitochondria
20
Q

what are precursors for the synthesis of glucose in gluconeogenesis

A

lactate, amino acids, glycerol

21
Q

what are the 4 enzymes that gluconeogenesis requires

A
  • glucose-6-phosphate
  • fructose-1,6-bisphosphate
  • PEP carboxykinase
  • pyruvate carboxylase
22
Q

what is the cori cycle

A

metabolic pathway in which lactate produced by anaerobic glycolysis in muscles is transported to the liver and converted to glucose, which then returns to the muscles and is cyclically metabolized back to lactate.

23
Q

what does increased fat intake without appropriate energy expenditure leads to

A
  • increase in number of adipocytes
  • more fat in adipocytes
  • obesity
24
Q

what are features of lipids

A
  • collection of different compounds
  • predominantly hydrocarbon
  • usually contain long chain fatty acids
  • insoluble in water
25
Q

what are the features of triglycerides

A
  • main energy storage form in adipose tissue
  • compact
  • hydrophobic
  • high energy yield per gram
26
Q

what is the structure of triglycerides

A
  • 3 fatty acids

- glycerol

27
Q

how do double bonds affect melting point

A

lower melting point

28
Q

what are the main products of fat digestion

A
  • glycerol
  • fatty acids
  • monoglycerides
29
Q

where is fat absorbed

A

The mucosal cells of the intestine. Short and medium length fatty acids enter the portal blood. Longer chains fatty acids and monoglycerides are resynthesises to triglycerides

30
Q

what are chylomicrons

A

fat is coated with a layer of protein, phospholipid, cholesterol called chylomicron. Formed in the intestinal epithelium to transport long-chain triglycerides to the tissues

31
Q

What is lipolysis

A

the breakdown of lipids

32
Q

where is fat stored

A

adipose tissue

33
Q

what initially cleaves fat, releasing free fatty acids and glycerol

A

hormone sensitive lipases

34
Q

what needs to be done to fatty acids for them to generate energy

A

converted to CoA derivatives and then oxidised

35
Q

what is the carnitine shuttle

A

Carnitine transports long-chain fatty acids into mitochondria to be oxidized for energy production, and also participates in removing products of metabolism from cells.

In the cytoplasm, fatty acids are transferred from acyl-CoA to carnitine. Acyl-carnitine transporter in inner membrane: facilitates anti port of acyl-carnitine into the mitochondrion and carnitine out

Net result = acyl-CoA located in mitochondrial matrix

36
Q

what is beta oxidation of fat

A

beta oxidation consists in breaking down long fatty acids that have been converted to acyl-CoA chains into progressively smaller fatty acyl-CoA chains

37
Q

how is glycerol broken down

A

Activated to glycerol-3-phosphate by glycerol kinase. Dehydrogenated to dihydroxyacetone phosphate

38
Q

How are ketone bodies formed

A

Formed in the liver mitochondria from acetyl-CoA from beta oxidation

39
Q

why are ketone bodies important

A

Important molecules of energy metabolism for heart muscle and renal cortex. Its converted back to acetyl-CoA, which enters the TCA cycle

40
Q

what is ketosis

A

Ketosis is a process that happens when your body doesn’t have enough carbohydrates to burn for energy. Instead, it burns fat and makes things called ketones, which it can use for fuel.

41
Q

what are ketones

A

Ketones are a type of chemical that your liver produces when it breaks down fats.

42
Q

what are the enzymes in glycolysis

A

hexokinase, phosphofructokinase, and pyruvate kinase

43
Q

what are the enzymes in glycogenesis

A

hexokinase, phosphofructokinase, and pyruvate kinase

44
Q

what are the enzymes in glycogenolysis

A

phosphorylase kinase and glycogen phosphorylase.

1st year GI (16 decks)

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