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Veterinary Physiology > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

1
Q

Carbohydrates

A

Carbon + hydrogen
Most abundant organic molecule

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2
Q

What are the functions of carbohydrates?

A

Energy in the diet
Storage in the form of energy
Serving as a component of cell membrane

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3
Q

Monosaccharides

A

Simple sugars
Those with 3-7 physiological importance

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4
Q

Disaccharides

A

Sucrose, maltose, lactose

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5
Q

Polysaccharides

A

Glycogen (animals)
Starch (plants)
Cellulose (only animals can metabolize)

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6
Q

What are the most important monosaccharides?

A

Glucose, fructose and galactose

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7
Q

Glucose

A

Major mammalian fuel
Wildly distributed in fruits and veggies as monosaccharides, disaccharides and polysaccharides

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8
Q

Why is glucose converted to other carbs?

A

For storage during catabolism

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9
Q

What diseases are associated with glucose metabolism?

A

Diabetes mellitus, galactosemia, glycogen storage disease

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10
Q

Galactosemia

A

Rare, hereditary disorder
Affects the body’s ability to convert galactose to glucose

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11
Q

Glycogen storage disease

A

Inability to form or degrade glycogen in normal metabolic pathways
Affects miniature dog breeds, cats, horses and primates
Prognosis is poor

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12
Q

What are the types of glycogen storage disease?

A

Type 1: G6P deficiency
Type 2 and 3: debranching enzyme deficiency

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13
Q

What are glucose transporters called?

A

GLUT 1-4
SGLT 1 and 2

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14
Q

SGLT glucose transporter

A

Located in the apical membrane of cells that line the proximal tubule (kindey) and small intestine

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15
Q

SGLT-1

A

Moves 2 Na with each glucose
Kidney, small intestine

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16
Q

SGLT3 and SGLT 2

A

Move one Na for each glucose
Kidney

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17
Q

Cells lacking _______ do not respond to insulin

A

GLUT-4

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18
Q

How is glucose absorbed?

A

Na-glucose transporter (absorbed from the lumen)

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19
Q

Hyperglycemia

A

When the GLUT transporter isn’t working
Have high blood glucose

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20
Q

Where is the GLUT-4 transporter located?

A

When insulin is present
Heart, skeletal muscles and fat

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21
Q

Glycolysis

A

Embeden-Meyerhoff Pathway (EMP)
To start removing the energy stored in glucose and make ATP the cell can use
Major route for catabolism of glucose, fructose and galactose
First step for respiration

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22
Q

How much glucose is metabolized via EMP?

A

80-90%

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23
Q

Glycolysis Process

A
  1. GLUCOSE enters the cytoplasm from the blood
  2. 2 ATP are used to energize the glucose
  3. GLUCOSE splits in 2
  4. Two 3-CARBON molecules made
  5. Each 3 CARBON molecule gives HIGH ENERGY ELECTRONS and HYDROGEN to make NADH
  6. Each 3 C molecule then gives energy to make 4 ATP molecules (2 each side)
  7. Each 3 C molecule now becomes a molecule of PYRUVATE (3C)
  8. NADH carries energy to the MITOCHONDRIA to be used in ELECTRON TRANSPORT
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24
Q

Phosphofructokinase deficiency

A

Clinical significance of glycolysis
Glycogen storage disorder
Breeds: american cocker spaniels, english springer spaniels

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25
Q

Pyruvate kinase deficiency

A

Enzyme in the last step of glycolysis that catalyzes the conversion of phophoenolypyruvate in ADP and to pyruvate and ATP in glycolysis
Associated with anemia
Breeds: Basenjis, beagles, cairn terriers, west highland white terriers

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26
Q

Anaerobic glycolysis

A

Glycolysis when oxygen is unavailable for oxidative phosphorylation

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27
Q

Why is anaerobic glycolysis important

A

Because the release of glycolytic energy to the cells can be lifesaving measure for a few minutes when oxygen is unavailable

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28
Q

What does the formation of lactic acid during anaerobic glycolysis allow?

A

The release of extra anaerobic energy

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29
Q

Phosphate Dehydrogenase Deficiency

A

An inherited metabolic disorder affecting Clumber Spaniels
Affected dogs present signs as early as 15 weeks

30
Q

PDH deficiency symptoms

A

Exercise intolerance (no more than 5 mins)
Puppy can’t play along with litter
Walk slowly and rest more often
Collapse during exercise/ play

31
Q

What is another name for Tricarboxylic Acid (TCA) cycle

A

Kreb’s cycle

32
Q

TCA cycle

A

A major integration center for coordinating carbohydrate, lipid and protein metabolism
Produces 2 ATP

33
Q

What reactions is TCA cycle involved in?

A

Transamination, deamination, gluconeogenesis from lactate, animo acids and propionate and lipogenesis in the liver

34
Q

Where in the cell does TCA cycle occur?

A

Mitochondrial matrix

35
Q

TCA ________ are not compatible with life

A

enzyme deficiences

36
Q

Oxidative Phosphorylation

A

Metabolic pathway where cells use enzymes to oxidize nutrients, releasing chemical energy to produce ATP (mitochondria)

37
Q

What does glycolysis produce

A

2 net ATP
2 NADHs
2 Pyruvates

38
Q

What does 1 glucose molecule produce

A

2 ATP from glycolysis
2 ATP from TCA
10 NADH (2+2+6)= 30 ATP
2 FADH2 from 4 ATP
(34 from oxidative phosphorylation)
Total 36-38 ATP

39
Q

How many ATPs does NADH produce?

A

2 ATP

40
Q

Glucneogenesis

A

Process wehre non-carbohydrate substrates are converted into Gluc-6-P in the liver and kidneys
A route to clear certain metabolites from blood
Stimulated by diabetogenic hormones

41
Q

What does gluconeogenesis provide?

A

Plasma glucose to glucose-sensitve tissues such as nerves and RBCs between meals

42
Q

What leads to hepatic glycogenesis in omnivores?

A

High hepatic portal glucose after meals

43
Q

What happens to omnivores between meals?

A

Hepatic glycogenolysis and gluconeogenesis will dominate
Hepatic glycogenolysis will provide glucose needs for 12-28 hours

44
Q

Why do ruminants and strict carnivores rely on Gluconeogenesis?

A

Little or no glucose is absorbed from GI and liver glycogen reserve is limited
so GNG is a continuous process with little or no correlation to food

45
Q

Cori cycle

A

The continuous conversion of lactate from muscle to glucose in liver and back to lactate in muscle
From Gerty and Carl Cori

46
Q

Dog Glycogen Storage Disease (GSD)

A

Glucose 2-phosphatase deficiency when circulating blood glucose levels cannot be increased

47
Q

What is the result of Dog Glycogen Storage Disease?

A

Fasting hypoglycemia
Accumulation of glycogen and fat (liver and kidney issues)

48
Q

What does the shunting of G6P into alternative metabolic pathway results in?

A

Lactic acidosis
Hypertriglyceridemia
Hyperuricemia

49
Q

How much glucose breakdown is not in glycolysis and citric acid cycle?

A

30%

50
Q

What does the pentose phosphate shunt do?

A

Generate NADPH
Provision of ribose for nucleotide and nucleic acid synthesis

51
Q

What happens when a muscle is deficient in Gluc-6-P dehydrogenase?

A

Limited hexo-monophosphate shunt and lipid synthetic activity

52
Q

What dog has G6P D.H. deficiency been reported in?

A

Weimaraner dogs

53
Q

What can G6P D.H. deficiency in humans lead to?

A

Hemolytic anemia

54
Q

What does NADPH deficiency lead to?

A

Impaired GSH reduction and hemoglobin oxidized

55
Q

What is required for hexo-monophosphate shunt ?

A

MG ++ and thiamine

56
Q

What does the oxidative phase of hexo-monophosphate shunt produce

A

It’s irreversible and produces CO2 and NADPH

57
Q

What are the biosynthetic functions of the uronic acid pathway

A

Synthesis of sugar moieties for glycoproteins
Participates in heparin and heparan sulfate formation
Production of UDP-glucoronate for various conjugation reactions
L-ascorbate formation (vitamin c)
Minor route for formation of pentoses that can enter HMS

58
Q

What enzyme of the uronic acid pathway is absent in humans?

A

Gulonolacton oxidase because we can’t synthesize that enzyme
Also absent in fish, flying mammals and songbirds

59
Q

Glucokinase

A

Enzyme in the liver and pancreatic B cell
Inducible in humans but not in ruminant liver because of low glucose absorbed from GI

60
Q

Hexokinase

A

Non-indicible
Present in all mammalian cells
Strongly inhibted by Glc-6-P
Activity in RBC declines with age
Responsible for erythrocyte

61
Q

What is the fate of glucose?

A

Glucose to G6P by enzyme glucokinase and hexokinase, and ATP, then back to phosphate
Glycolysis

62
Q

How is glycogen utilized after absorption into cells?

A

It’s utilized immediately for energy or stored in the form of glycogen

63
Q

Glycogenesis

A

Process of glycogen formation

64
Q

Glucogenolysis

A

Process of glycogen breakdown to re-form glucose

65
Q

What are the features of glycoge storage disease?

A

Exercise intolerance, low blood glucose, hyperlipidemia, ketonemia

66
Q

GSD: G6P deficiency

A

Toy dog breeds

67
Q

GSD: 1,4-glucosidase, acid maltase deficiency

A

Corriedale sheep, lapland dogs, shorthorn and brashman cattle, japanese quail

68
Q

GSD debranching deficiency

A

German shepherds

69
Q

GSD branch deficiency

A

Cat, charolaise cattle, quarter horses

70
Q

GSD: phosphofructokinase deficiency

A

Egnlish spring spaniels, wachtelhunds

Veterinary Physiology (20 decks)

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