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Alimentary (MEDI302) > Metabolism (Glucose, Fat & Protein) > Flashcards

Metabolism (Glucose, Fat & Protein) Flashcards

1
Q

Name the transporter responsible for moving glucose into the cell

A

GLUT (1, 2, 3, 4)

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2
Q

How does glucose get into the cells?

A

Through GLUT transporters

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3
Q

Where is GLUT1 found, and what is its specialty?

A

Fetal tissue; adult erythrocytes and endothelial cells.

Low level glucose uptake (all cells)

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4
Q

Where is GLUT2 found, and what is its specialty?

A

Liver and pancreatic (beta) cells, renal tubular cells, small intestine epithelium
Allows glucose flow in 2 directions (allows for monitoring of blood sugar levels)

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5
Q

Where is GLUT3 found, and what is its specialty?

A

Neurons, placenta

Allows glucose transport at very low concentrations (so neurons keep working even when not eating)

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6
Q

Where is GLUT4 found, and what is its specialty?

A

Adipose cells, striated muscle cells

Insulin regulated: responsible for insulin regulated glucose storage

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7
Q

Which GLUT receptor is found in fetal tissue and adult erythrocytes?

A

GLUT1

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8
Q

Which GLUT receptor is responsible for low level glucose uptake in all cells?

A

GLUT1

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9
Q

Which GLUT receptor is found in liver and pancreatic cells?

A

GLUT2

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10
Q

Which GLUT receptor allows for glucose flow in 2 directions (allowing for monitoring of blood sugar levels)?

A

GLUT2

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11
Q

Which GLUT receptor is found in neurons?

A

GLUT3

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12
Q

Which GLUT receptor is responsible for glucose transport at very low concentrations, and why is this important?

A

GLUT3

So neurons don’t shut off

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13
Q

Which GLUT receptor is found in adipose and striated muscle cells?

A

GLUT4

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14
Q

Which GLUT receptor is insulin regulated?

A

GLUT4

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15
Q

What is glycolysis?

A

The breakdown of glucose into pyruvate in the cell cytosol.

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16
Q

Give an overview of glycolysis

A

Glucose => (enzymatic reactions, consuming 2ATP) => 2 3-carbon molecules => (reactions producing 4ATP) => 2 pyruvate molecules

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17
Q

What are the 3 metabolic pathways that can occur after glycolysis?

A

Fermentation
Lactate production
Oxidation

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18
Q

Name the steps from glucose in the blood to energy

A
  1. Transport glucose into cell
  2. Glycolysis
  3. Transport pyruvate into mitochondrial matrix
  4. Krebs cycle
  5. Electron transport chain
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19
Q

What is the role of pyruvate dehydrogenase?

A

Irreversibly convert pyruvate into Acetyl CoA

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20
Q

Which enzyme converts pyruvate into Acetyl CoA?

A

Pyruvate dehydrogenase

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21
Q

How is pyruvate dehydrogenase regulated?

A

Product inhibition (inhibited by Acetyl CoA)
NADH inhibited
NAD+ activated

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22
Q

What is the most important molecule in the Krebs cycle, that is the same at the beginning as at the end?

A

Oxaloacetate

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23
Q

What is the importance of oxaloacetate?

A

Most important molecule (starts and finishes) the Krebs cycle

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24
Q

Explain the Electron Transport Chain

A

Electrons are passed into the membrane complexes, pumping H+ ions across to set up a concentration gradient. The energy in this gradient is used to synthesise ATP from ADP by ATP synthase.

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25
Q

Role of gluconeogenesis

A

Salvage pyruvate and lactate, converting it back into glucose; maintains blood glucose levels

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26
Q

What is the Cori Cycle?

A

Lactate formed by active muscle is converted back into glucose by the liver

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27
Q

Role of the Cori Cycle

A

Shift some of the metabolic burden of active muscle

28
Q

What are the major precursors for gluconeogenesis?

A

Lactate
Amino acids
Glycerol

29
Q

Where does gluconeogenesis occur?

A

Liver mostly, a little in the kidneys

30
Q

Outline fat metabolism

A
  1. Fats ingested
  2. Bile salts/lipase degrades triacylglycerols
  3. Fatty acids taken up by intestinal mucosa, converted back to triacylglycerols
  4. Chylomicrons formed
  5. Chylomicrons move through lymphatic system/bloodstream to tissues
  6. Lipoprotein lipase releases fatty acids and glycerol
  7. Fatty acids enter cells
  8. Fatty acids are oxidised as fuel or re-esterified for storage.
31
Q

Summarise how fatty acids are used as fuels

A
  1. Mobilisation (triacylglycerols degraded, released from adipose tissue, transported to tissue requiring energy [bound to albumin])
  2. Transport into mitochondrial matrix
  3. Breakdown of fatty acids (into acetyl CoA for Krebs cycle)
32
Q

What are lipases activated by?

A

Epinephrine
Norepinephrine
Glucagon
Adrenocorticotropic hormone

33
Q

What are lipases inhibited by?

34
Q

Role of Carnitine

A

Helps mobilise fats into mitochondrial matrix to be used for energy production

35
Q

Oxaloacetate is important in…

A

Gluconeogenesis and the Krebs cycle

36
Q

If oxaloacetate is unavailable, Acetyl CoA is diverted to…

A

Ketogenesis, in the liver

37
Q

Where does ketogenesis occur?

A

In the liver

38
Q

What are ketone bodies?

A

Soluble, transportable form of Acetyl CoA

39
Q

The catabolism of amino acids accounts for what percentage of the body’s energy production?

40
Q

What is involved in the degradation of amino acids?

A

Removal of alpha-amino group => ammonia

Remaining carbon skeleton is metabolised

41
Q

Where does amino acid degradation take place?

A

In the liver

42
Q

Where does the urea cycle occur?

A

In the liver

43
Q

The carbon skeleton of the 20 amino acids are converted into one of 7 molecules, which are:

A 
Acetyl CoA
Acetoacetyl CoA
Pyruvate
Alpha-ketoglutarate
Succinyl CoA
Fumarate
Oxaloacetate
44
Q

What is the major site for production of ketone bodies?

45
Q

What must happen before glycolysis?

A

Glucose must be taken into the cytoplasm by GLUT, which is brought to the cell membrane by activated insulin receptors

46
Q

Name the substrate(s) of glycolysis

47
Q

Name the products of glycolysis

A

2 Pyruvate
4 ATP
2 NADH

48
Q

Where does glycolysis occur?

49
Q

Name the substrate(s) of gluconeogenesis

A

Pyruvate

|&raquo_space; Also: lactate, amino acids, glycerol

50
Q

Name the product(s) of gluconeogenesis

51
Q

Where does gluconeogenesis occur?

A

Liver (and sometimes kidney) cells

52
Q

What is the role of gluconeogenesis?

A

Maintain blood glucose levels

|&raquo_space; salvage pyruvate, lactate

53
Q

What needs to happen before the Krebs cycle?

A

Pyruvate needs to be converted to acetyl CoA

Oxaloacetate must be present

54
Q

What are the substrate(s) of the Krebs cycle?

A

Acetyl CoA (and oxaloacetate)

55
Q

What are the product(s) of the Krebs cycle?

A 
GTP
3x NADH
1x FADH2
2x CO2
(oxaloacetate)
56
Q

Where does the Krebs cycle occur?

A

In the mitochondria

57
Q

What are ketone bodies used for?

A

Acetoacetate&raquo_space; preferable source of energy for heart muscle and renal cortex
Fuel source during ‘starvation’ periods

58
Q

What are ketone bodies?

A

Soluble (transportable) forms of Acetyl CoA

59
Q

3 categories of carbohydrates

A

Sugars
Starches (polysaccharides)
Fibre

60
Q

What is glycogen?

A

The body’s store of glucose (a polysaccharide)

61
Q

Name 3 beneficial physiological effects of dietary fibre

A

Laxation
Reduction in blood cholesterol
Modulation of blood glucose

62
Q

Most of the fats in foods are…

A

Triacylglycerol

63
Q

What are chylomicrons?

A

Largest lipoprotein

Transport dietary lipids from intestine

64
Q

Describe the digestion of carbohydrates

A

Broken down into monosaccharides in stomach and duodenum

Absorbed in jejunum

65
Q

Describe the digestion of proteins

A

Broken down into amino acids and absorbed in the duodenum

66
Q

Describe the digestion of lipids

A

Broken down into fatty acids and monoglycerides in duodenum

Absorbed in jejunum

Alimentary (MEDI302) (7 decks)

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