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MBBCh 2- PHSL2004A > 5. Carbohydrate Metabolism (1) > Flashcards

5. Carbohydrate Metabolism (1) Flashcards

1
Q

Nutrition vs metabolism

A
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2
Q

In chemistry:

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3
Q

In metabolism:

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4
Q

What is a) Catabolic processes (catabolism)? (3)

A
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5
Q

Overview of catabolic processes in metabolism. (3)

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6
Q

What are the catabolic pathways in carbohydrates? (4)

A

a) glycolysis
b) tricarboxylic acid (TCA or Krebs’ or citric acid) cycle
c) oxidative phosphorylation\
d) glycogenolysis

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7
Q

What are the catabolic pathways in lipids (fats)? (2)

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8
Q

What are the catabolic pathways in proteins? (2)

A

a) proteolysis, deamination
b) oxidation of amino acids

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9
Q

What are anabolic processes?

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10
Q

The major anabolic pathways include: (5)

A

o glycogen synthesis
o gluconeogenesis
o fatty acid synthesis
o lipogenesis
o protein synthesis

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11
Q

Fill in the rest of the diagram and identify the catabolic and anabolic processes.

A
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12
Q

What is the function of ATP? (3)

A
  • ATP is the key energy source
    – nitrogenous base, ribose sugar and phosphate
    – may be other nucleotide triphosphates such as uridine
    – two high-energy bonds that provide energy
  • for anabolic processes
  • energy-consuming processes (e.g. muscle contraction)
  • atpase pumps in cell walls (insulin is required to produce ATP)
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13
Q

What are the 3 adenosine molecules?

A
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14
Q

What are the other nucleotide energy-containing nucleosides? (3)

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15
Q

What are the ATP storage molecules?

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16
Q

What are Electron carriers? (2)

A
  • Energy packets in the form of NADH and FADH2 contain energy but require an additional pathway to release ATP.
    – Redox reactions and electron carriers are used to couple energy released from food molecules to synthesis of ATP.
  • Vitamins are critical for complete utilization of the energy in food.
    – Vitamins B1, B2 and B3 are critical as co-enzymes in the carbohydrate metabolism pathways
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17
Q

What are Reduction-oxidation (redox) reactions in metabolism?

A
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18
Q

Enzyme =
The electrons released when substances are _______ have potential energy.
This potential energy is used to synthesise ATP in the electron transport chain (ETC) in the _________.

A

lactate dehydrogenase (LDH))
oxidised
mitochondria

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19
Q

What happens to the electrons?

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20
Q
A

NADH is transported
into the mitochondrion
and transfers electrons
to the electron transport
chain (ETC)

All of the electron carriers are co-enzymes made from vitamins.

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21
Q

Other electron carriers: (3)

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22
Q

Why are vitamins critical? (3)

A
  • Vitamins are critical for complete utilization of the
    energy in food.
    – B1 - co-enzyme for pyruvate dehydrogenase (PDH)
    – B2 – Riboflavin for FAD+ production
    – B3 - Niacin (nicotinomide) for NAD+ production
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23
Q

What is the function of CoA?

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24
Q

What are acyl groups?

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25
Q

What is Acetyl CoA?

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26
Q

What is the regulation of blood glucose?

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27
Q

Hormonal Regulation:

  • Regulation of blood glucose and energy
    production is a critical component of _______.
  • Blood glucose is maintained in a very narrow
    range ____mmol/l to ____ mmol/l
  • If an imbalance occurs there are two
    _________ mechanisms to counteract either
    – increase
    – decrease
A

homeostasis
4.1mmol/l
5.9mmol/l
physiological

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28
Q

Dietary sources of carbohydrate: (4)

A
  • Sugar, sweets, chocolate, fruit, honey
  • Starchy vegetables, potato, pumpkin, squash, sweet
    potato, butternut, chips.
  • Grains and grain products, wheat, maize, rice, bread,
    porridge/pap, pasta, cake, biscuits,
  • glycogen in meat
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29
Q

Recommended daily intake of carbohydrate:

A
  • Dietary guidelines USDA/NHS - 200-300 g, 45-65% of
    energy
  • Less processed starchy foods are recommended –
    eg.whole grains, legumes and root vegetables,
  • Eat less refined starches and sugars
  • Brain - 130 g/day
30
Q

Dietary fibre
Dietary fibre is indigestible carbohydrate e.g. cellulose.
* Increases intestinal ____ = the microbiome.
* Adds bulk to faeces, retains water in the GIT, speeds intestinal transit – eases passage of faeces.
* May prevent ______ and hemorrhoids.
* Slows digestion and absorption – slower blood glucose change in ______ lower cholesterol.

A

flora
diverticulitis
diabetes

31
Q

Dietary sources of fibre: (2)

A
  • Vegetables (green), cabbage, broccoli, lettuce, mushrooms, peppers,
    beans, legumes, nuts, seeds
  • Whole grains – brown bread, brown rice, samp, etc., bran
32
Q

What are Carbohydrates?

A
33
Q

Three chemical classes of carbohydrates: (3)

A
  1. Monosaccharides
  2. Disaccharides
  3. Dietary polysaccharides (glucose polymers)
34
Q
  1. Monosaccharides
    Vary from 3 (triose) to 9 (nonose) carbons
    _______ (6-carbon sugars)
    Used as fuel and for synthesis of metabolic _______
    * Glucose (sweets)
    * Fructose (from fruit)
    * Galactose (derived from milk)
A

Hexoses
intermediates

35
Q

What are hexose sugars?

A
36
Q

1 Monosaccharides - Pentoses (5-carbon sugars)
Most common are _____ and _______e
Components of nucleic acids and ATP, GTP etc.
Synthesised in body.

A
37
Q

Disaccharides
Each contain 2 __________ subunits
*Sucrose (table sugar)
*Maltose (breakdown product of starch and glycogen)
*Lactose (milk sugar)

A

monosaccharide

38
Q

Glucose storage polysaccharides –
_______ in animals
Starch in plants
Plant structural polysaccharides
________

A

Glycogen
Cellulose

39
Q

What is the general structure of starch and glycogen?

A
40
Q

___ 1-6 (branches) and ____ 1-4 (chains) glycosidic bonds can be _________ digested by humans.

Therefore, glycogen and starch are digestible

A
41
Q

General structure of cellulose:

A
42
Q

Digestion of starch and glycogen
Enzyme α–amylase (produced by salivary glands and pancreas) cleaves large starch molecules into:

A
43
Q

Digestion and absorption of mono-/disaccharides and α-limit _____

Glucose carrier = Sodium-dependent ______ transporter (SGLT)

A

dextrin
glucose

44
Q

Absorption of carbohydrates”

Monosaccharides are transported in bloodstream
via the ______ _______ circulation
Taken up into cells.
* Used immediately for energy
_________
or
* Stored as glycogen in muscles and liver
____________
or
* Converted into fatty acids (liver) and stored (adipose tissue)

A

portal vein
GLYCOLYSIS
GLYCOGENESIS

45
Q

Remedy:

A
  • Avoid dairy products or use lactose-free dairy products
  • Yoghurt is tolerated better than unfermented dairy products
46
Q

Excess carbohydrate intake:

A
47
Q

Blood glucose homeostasis
INSULIN - REGULATORY HORMONE
Pathways of glucose metabolism after ________ of carbohydrate
* Glucose uptake into cells
– Critical for the production of ATP
– ATPase pumps
* in the _______ of the cell
– Catabolic
* Glycolysis
– ________
* Pentose __________ pathway
* Glycogenesis (Glycogen synthesis)

A

ingestion
cytosol
Anabolic
phosphate

48
Q

Why is insulin increased?

A

Insulin is increased
1. Glycolysis – pathway in cytosol to extract the
energy from glucose.
2. Glycogenesis – pathway to store glucose as
glycogen for use when fasting
3. Ribose - Pentose Phosphate pathway

49
Q

How is glucose taken up into the cells?

A
50
Q
  1. Regulation of glycolysis

What are the 2 enzymes?

A
51
Q

Glucose uptake into cells from
blood
* Glucose uptake into most tissues is controlled by _______.
* Glucose transporter in peripheral tissues, ______ (glucose
transporter 4) - increased by insulin.
* Glucose uptake into liver, brain, red blood cells and
pancreas is not regulated by insulin. It depends on blood ______ concentration.
– Results in ________ of the cells – primarily seen in red blood cells (HB1aC)
* Insulin-independent cells have different insulin-
independent glucose transporters (GLUT-2).
– _______ receptors – SGLT2 antagonist drugs prevent glucose reabsorbtion in the nephrons of the kidney
* Glucose phosphorylation reaction is irreversible and
________-_______ cannot cross cell membranes.
* Glucokinase activity is increased by cellular glucose &
induced by insulin.

A

insulin.
GLUT-4
glucose
SGLT
glucose-6-phosphate

52
Q
  1. Glycolysis: energy investment and splitting (5)
A
53
Q
  1. Glycolysis: energy production/yield steps
    Aerobic conditions (6)
A
54
Q
  1. Glycolysis: Overall reaction from glucose to pyruvate
    (aerobic glycolysis)
A
55
Q

Glycolysis: energy production/yield steps
Anaerobic conditions (6)

A
56
Q
  1. Glycolysis: OVERALL reaction from glucose to lactate
    (anaerobic glycolysis)
A
57
Q

Tissue dependence on glycolysis for energy production:
Red blood cells:
Muscle:
Brain:
Adipose tissue:

A

Red blood cells – Totally dependent on anaerobic glycolysis (no mitochondria).

Muscle – Very dependent on glycolysis both aerobically and anaerobically.

Brain – Prefers aerobic glycolysis.

Adipose tissue – Glycolysis needed for lipid synthesis and cell

58
Q
  1. Regulation of glycolysis cont…..
    Phosphofructokinase-1 (PFK-1) (fructose-1P + ATP → fructose-1,6-bisP + ADP)

Enzyme activity stimulated by: (3)

A
  • increased AMP concentration
  • increased concentration of glycolytic substrates
  • insulin (indirectly)
59
Q
  1. Regulation of glycolysis cont…..
    Phosphofructokinase-1 (PFK-1) (fructose-1P + ATP → fructose-1,6-bisP + ADP)

Enzyme activity inhibited by: (3)

A
  • increased ATP concentration
  • increased citrate concentration
  • Also glucagon, adrenaline (indirectly)
60
Q
  1. Regulation of glycolysis cont…..
    Pyruvate kinase (phosphoenolpyruvate + ADP → pyruvate + ATP)
    Activity stimulated by: (2)

Activity inhibited by: (2)

A

Fructose-1,6-bisphosphate
Insulin

ATP
glucagon

61
Q

Lactate dehydrogenase (pyruvate + NADH → lactate + NAD+)

Activity stimulated by: (3)

A

increased pyruvate
increased NADH
decreased NAD+

62
Q

What are the fates of glucose-6-phosphate?

A
63
Q

What is the pentose phosphate pathway (hexose monophosphate shunt)? (6)

A
64
Q

What is the Synthesis of glycogen (glycogenesis) from glucose-6-phosphate? (8)

A
65
Q

Whole body view of blood glucose homeostasis:

A
66
Q

Blood glucose homeostasis
Glucose homeostasis is aimed at:

A
  • Maintaining blood glucose concentration at 4.1 – 5.9 mmol/l
67
Q

Excess blood glucose
* glucose is removed from the blood when it is in ______
* stored as ______ (in liver and muscle)
* stored as fat

A

excess
glycogen

68
Q

The primary organ of glucose homeostasis when glucose concentration is decreased is the ______.

A

liver

69
Q

Decreased blood glucose concentration
* liver glycogen stores are utilised
* the synthesis of glucose occurs
* _______ fat instead of glucose when little/no carbohydrate is eaten

A

catabolism

70
Q

What is the process of the regulation of glycogen synthesis (glycogenesis? (9)

A

MBBCh 2- PHSL2004A (19 decks)

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