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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
Role of gluconeogenesis
Salvage pyruvate and lactate, converting it back into glucose; maintains blood glucose levels
26
What is the Cori Cycle?
Lactate formed by active muscle is converted back into glucose by the liver
27
Role of the Cori Cycle
Shift some of the metabolic burden of active muscle
28
What are the major precursors for gluconeogenesis?
Lactate Amino acids Glycerol
29
Where does gluconeogenesis occur?
Liver mostly, a little in the kidneys
30
Outline fat metabolism
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
Summarise how fatty acids are used as fuels
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
What are lipases activated by?
Epinephrine Norepinephrine Glucagon Adrenocorticotropic hormone
33
What are lipases inhibited by?
Insulin
34
Role of Carnitine
Helps mobilise fats into mitochondrial matrix to be used for energy production
35
Oxaloacetate is important in...
Gluconeogenesis and the Krebs cycle
36
If oxaloacetate is unavailable, Acetyl CoA is diverted to...
Ketogenesis, in the liver
37
Where does ketogenesis occur?
In the liver
38
What are ketone bodies?
Soluble, transportable form of Acetyl CoA
39
The catabolism of amino acids accounts for what percentage of the body's energy production?
10-15%
40
What is involved in the degradation of amino acids?
Removal of alpha-amino group => ammonia | Remaining carbon skeleton is metabolised
41
Where does amino acid degradation take place?
In the liver
42
Where does the urea cycle occur?
In the liver
43
The carbon skeleton of the 20 amino acids are converted into one of 7 molecules, which are:
``` Acetyl CoA Acetoacetyl CoA Pyruvate Alpha-ketoglutarate Succinyl CoA Fumarate Oxaloacetate ```
44
What is the major site for production of ketone bodies?
The liver
45
What must happen before glycolysis?
Glucose must be taken into the cytoplasm by GLUT, which is brought to the cell membrane by activated insulin receptors
46
Name the substrate(s) of glycolysis
Glucose
47
Name the products of glycolysis
2 Pyruvate 4 ATP 2 NADH
48
Where does glycolysis occur?
Cytoplasm
49
Name the substrate(s) of gluconeogenesis
Pyruvate | >> Also: lactate, amino acids, glycerol
50
Name the product(s) of gluconeogenesis
Glucose
51
Where does gluconeogenesis occur?
Liver (and sometimes kidney) cells
52
What is the role of gluconeogenesis?
Maintain blood glucose levels | >> salvage pyruvate, lactate
53
What needs to happen before the Krebs cycle?
Pyruvate needs to be converted to acetyl CoA | Oxaloacetate must be present
54
What are the substrate(s) of the Krebs cycle?
Acetyl CoA (and oxaloacetate)
55
What are the product(s) of the Krebs cycle?
``` GTP 3x NADH 1x FADH2 2x CO2 (oxaloacetate) ```
56
Where does the Krebs cycle occur?
In the mitochondria
57
What are ketone bodies used for?
Acetoacetate >> preferable source of energy for heart muscle and renal cortex Fuel source during 'starvation' periods
58
What are ketone bodies?
Soluble (transportable) forms of Acetyl CoA
59
3 categories of carbohydrates
Sugars Starches (polysaccharides) Fibre
60
What is glycogen?
The body's store of glucose (a polysaccharide)
61
Name 3 beneficial physiological effects of dietary fibre
Laxation Reduction in blood cholesterol Modulation of blood glucose
62
Most of the fats in foods are...
Triacylglycerol
63
What are chylomicrons?
Largest lipoprotein | Transport dietary lipids from intestine
64
Describe the digestion of carbohydrates
Broken down into monosaccharides in stomach and duodenum | Absorbed in jejunum
65
Describe the digestion of proteins
Broken down into amino acids and absorbed in the duodenum
66
Describe the digestion of lipids
Broken down into fatty acids and monoglycerides in duodenum | Absorbed in jejunum

Alimentary (MEDI302) (7 decks)

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