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- Animal Energetics and Homeostasis > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

(69 cards)

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1
Q

What is glycolysis?

A

A pathway that enable glucose to be manipulated for energy extraction and cleavage into 2 pyruvate molecules

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2
Q

What are the three roles of glycolysis?

A
  • Extract energy and store as NADPH
  • Enable glycogen formation
  • Cleave glucose into pyruvate
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3
Q

What are the three stages of carbohydrate catabolism?

A
  • Hydrolysis of ploysaccharides
  • Glycolysis to pyruvate to acetyl-CoA
  • Citric acid cycle to produce CO2 and H2O
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4
Q

What are the common end products of carbohydrate catabolism?

A

CO2, H2O and ATP

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5
Q

What are four other alternative processes in carbohydrate catabolism?

A
  • Ruminant fermentation
  • Secondary pathways
  • Anaerobic metabolism
  • Storage polysaccharides
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6
Q

What is the chemical equation fro glycolysis?

A

Glucose –> 2 pyruvate + 2 ATP + 2 NADH

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7
Q

How many enzyme catalysed reactions are in glycolysis?

A

10

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8
Q

What are the 2 phases of glycolysis?

A
  • Energy investment
  • Cleavage
  • Energy payoff
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9
Q

Where does glycolysis occur?

A

In the cytoplasm

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10
Q

How does fructose enter glycolysis?

A

Through alternate pathways depending on tissue type

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11
Q

How does fructose enter the liver?

A

Via fructokinase

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12
Q

What inhibits pyruvate kinase?

A

ATP and alanine

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13
Q

What inhibits phosphofructokinase (PFK)?

A

Inhibited by ATP and citrate

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14
Q

What stimulates phosphofructokinase (PFK)?

A

Fructose 6 phosphate

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15
Q

What inhibits hexokinase?

A

Glucose 6 phosphate

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16
Q

What kind of regulation controls glycolytic enzymes?

A

Feedback inhibition via downstream metabolites like ATP, alanine, citrate

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17
Q

What is gluconeogenesis?

A

Synthesis of glucose from non carbohydrate precursors

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18
Q

Why is gluconeogenesis important?

A

Maintains blood glucose from brain function during fasting and replenishes glucose stores

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19
Q

How long do glycogen reserves last?

A

About 1 day

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20
Q

How is gluconeogenesis similar to glycolysis?

A
  • Both are central metabolic pathways
  • Share 7 reversible reactions
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21
Q

What makes gluconeogenesis different from glycolysis?

A
  • Uses different enzymes for 3 irreversible steps
  • Occurs in the liver not muscle
  • Consumers more energy
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22
Q

Which glycolytic steps are bypassed in gluconeogenesis?

A
  • Hexokinase –> glucose 6 phosphate
  • PFK –> fructose 1 6 bisphosphate
  • Pyruvate kinase –> pyruvate carboxylase + PEP carboxykinase
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23
Q

What is fermentation?

A

Anaerobic metabolism of pyruvate

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24
Q

Why is fermentation important?

A

Allows ATP production without oxygen by regenerating NAD+

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25
What are the two products of the oxidative branch of the pentose phosphate pathway?
NADPH and ribose 5 phosphate
26
What is NADPH used for?
Reductive biosynthesis such as fatty acid synthesis
27
What is ribose 5 phosphate used for?
Nucleotide synthesis such at ATP, DNA and RNA
28
What are the two branches of pentose phosphate pathway?
- Oxidative - Non oxidative
29
What does the oxidative branch of pentose phosphate pathway produce?
NADPHY + ribose 5 phosphate
30
What occurs during the non oxidative branch of pentose phosphate pathway?
Sugar interconversion
31
Where does the sorbitol pathway occur?
- Testes - Pancreas - Brain - Eye lens
32
What enzymes are involved in converting glucose to fructose via sorbitol?
- Aldose reductase - Sorbitol dehydrogenase
33
What does aldose reductase do?
Glucose --> sorbital
34
What does sorbitol dehydrogenase do?
Sorbitol --> fructose
35
Why is fructose important in the tissues where the sorbitol pathway occurs?
- Energy for sperm - Osmoregulation
36
What happens with excess sorbitol in diabetes?
- Sorbitol accumulates in the lens - Causes protein precipitation - Leads to cataracts
37
Why are some steps in glycolysis and gluconeogenesis irreversible?
As they are highly exergonic
38
What is a futile cycle?
It is a wasteful loop where glycolysis and gluconeogenesis run simultaneously
39
What are the main substrates for gluconeogenesis?
- Glycerol - Lactate - Pyruvate - Glucogenic amino acids - Propionate
40
What is the source of glucogenic amino acids?
From protein breakdown
41
What is the source of propionate?
From odd chain fatty acid and amino acid oxidation
42
What vitamin is essential for propionate metabolism?
Vitamin B12
43
Where does PEP carboxykinase act in gluconeogenesis?
- Mitochondria - Cytoplasm
44
What is regulatory relationship between glycolysis and gluconeogenesis?
They are reciprocally regulated only one is active at a time
45
Which enzyme does AMP activate in glycolysis?
Phosphofructokinase
46
What enzyme does AMP inhibit in gluconeogenesis?
Fructose 1, 6 bisphosphatase
47
What is the cori cycle?
It is the cycle where lactate from muscle is converted back to glucose in the liver
48
Why is the cori cycle important?
It helps maintain energy supply during anaerobic muscle activity
49
What is glycogen?
A branched storage polysaccharide made of glucose
50
Where is glycogen stored?
In intracellular granules in the liver and skeletal muscle
51
What are two major functions of glycogen?
- Regulate blood glucose - Fuel muscle activity
52
Which enzyme cleaves glycogen during degradation?
Glycogen phosphorylase
53
What is the product of glycogen phosphorylase activity?
Glucose 1 phosphate
54
Why can't phosphorylase fully degrade branched glycogen?
It stops 4 residues before a branch point
55
What two enzymes are involved in debranching glycogen?
- 4-α-glucanotransferase - α-1,6-glucosidase
56
How is glycogen synthesised?
Glycogen synthase adds glucose units from UDP-glucose to glycogen primer
57
How are glycogen synthesis and degradation regulated?
They are reciprocally regulated only one pathway is active at a time
58
How does phosphorylation affect glycogen metabolism enzymes?
- Stops synthesis - Promotes degradation
59
Which enzyme controls enzyme activation via dephosphorylation?
Protein phosphatase 1
60
How does adrenaline affect glycogen metabolism?
It stimulates glycogen degradation and inhibits glycogen synthesis
61
How does glucagon affect glycogen metabolism in the liver?
It stimulates glycogen breakdown and inhibits synthesis in response to low blood glucose
62
What are glycogen storage diseases?
Genetic disorders caused by enzyme deficiencies in glycogen metabolism leading to abnormal glycogen accumulation and hypoglycemia
63
What are common features of glycogen storage diseases?
- Glycogen accumulation - Hypoglycemia - Enzyme deficiency
64
What is diabetes mellitus?
Insulin production or function is impaired leading to high blood glucose levels
65
What does insulin do to glucose uptake?
Increase uptake by increasing number of glucose carrier proteins
66
Besides glucose uptake what other processes does insulin regulate?
- Amino acid transport - Lipase activity - Protein, fat and glycogen synthesis
67
Why are newborn piglets particularly susceptible to hypoglycemia?
The gluconeogenic mechanisms are underdeveloped until about 10 days of age
68
What is metabolic acidosis?
A decrease in blood and tissue pH due to accumulation of acidic compounds
69
What can cause metabolic acidosis?
Excess lactic acid or ketone bodies

- Animal Energetics and Homeostasis (21 decks)

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