5. Carbohydrate Metabolism (1) Flashcards
1
Q
Nutrition vs metabolism
A
2
Q
In chemistry:
A
3
Q
In metabolism:
A
4
Q
What is a) Catabolic processes (catabolism)? (3)
A
5
Q
Overview of catabolic processes in metabolism. (3)
A
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
7
Q
What are the catabolic pathways in lipids (fats)? (2)
A
8
Q
What are the catabolic pathways in proteins? (2)
A
a) proteolysis, deamination
b) oxidation of amino acids
9
Q
What are anabolic processes?
A
10
Q
The major anabolic pathways include: (5)
A
o glycogen synthesis
o gluconeogenesis
o fatty acid synthesis
o lipogenesis
o protein synthesis
11
Q
Fill in the rest of the diagram and identify the catabolic and anabolic processes.
A
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)
13
Q
What are the 3 adenosine molecules?
A
14
Q
What are the other nucleotide energy-containing nucleosides? (3)
A
15
Q
What are the ATP storage molecules?
A
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
17
Q
What are Reduction-oxidation (redox) reactions in metabolism?
A
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
19
Q
What happens to the electrons?
A
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.
21
Q
Other electron carriers: (3)
A
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
23
Q
What is the function of CoA?
A
24
Q
What are acyl groups?
A
25
What is Acetyl CoA?
26
What is the regulation of blood glucose?
27
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
homeostasis
4.1mmol/l
5.9mmol/l
physiological
28
Dietary sources of carbohydrate: (4)
* 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
29
Recommended daily intake of carbohydrate:
* 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
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.
flora
diverticulitis
diabetes
31
Dietary sources of fibre: (2)
* Vegetables (green), cabbage, broccoli, lettuce, mushrooms, peppers,
beans, legumes, nuts, seeds
* Whole grains – brown bread, brown rice, samp, etc., bran
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What are Carbohydrates?
33
Three chemical classes of carbohydrates: (3)
1. Monosaccharides
2. Disaccharides
3. Dietary polysaccharides (glucose polymers)
34
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)
Hexoses
intermediates
35
What are hexose sugars?
36
1 Monosaccharides - Pentoses (5-carbon sugars)
Most common are _____ and _______e
Components of nucleic acids and ATP, GTP etc.
Synthesised in body.
37
Disaccharides
Each contain 2 __________ subunits
*Sucrose (table sugar)
*Maltose (breakdown product of starch and glycogen)
*Lactose (milk sugar)
monosaccharide
38
Glucose storage polysaccharides –
_______ in animals
Starch in plants
Plant structural polysaccharides
________
Glycogen
Cellulose
39
What is the general structure of starch and glycogen?
40
___ 1-6 (branches) and ____ 1-4 (chains) glycosidic bonds can be _________ digested by humans.
Therefore, glycogen and starch are digestible
41
General structure of cellulose:
42
Digestion of starch and glycogen
Enzyme α–amylase (produced by salivary glands and pancreas) cleaves large starch molecules into:
43
Digestion and absorption of mono-/disaccharides and α-limit _____
Glucose carrier = Sodium-dependent ______ transporter (SGLT)
dextrin
glucose
44
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)
portal vein
GLYCOLYSIS
GLYCOGENESIS
45
Remedy:
* Avoid dairy products or use lactose-free dairy products
* Yoghurt is tolerated better than unfermented dairy products
46
Excess carbohydrate intake:
47
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)
ingestion
cytosol
Anabolic
phosphate
48
Why is insulin increased?
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
How is glucose taken up into the cells?
50
1. Regulation of glycolysis
What are the 2 enzymes?
51
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.
insulin.
GLUT-4
glucose
SGLT
glucose-6-phosphate
52
1. Glycolysis: energy investment and splitting (5)
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2. Glycolysis: energy production/yield steps
Aerobic conditions (6)
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1. Glycolysis: Overall reaction from glucose to pyruvate
(aerobic glycolysis)
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Glycolysis: energy production/yield steps
Anaerobic conditions (6)
56
2. Glycolysis: OVERALL reaction from glucose to lactate
(anaerobic glycolysis)
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Tissue dependence on glycolysis for energy production:
Red blood cells:
Muscle:
Brain:
Adipose tissue:
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
2. Regulation of glycolysis cont.....
Phosphofructokinase-1 (PFK-1) (fructose-1P + ATP → fructose-1,6-bisP + ADP)
Enzyme activity stimulated by: (3)
* increased AMP concentration
* increased concentration of glycolytic substrates
* insulin (indirectly)
59
2. Regulation of glycolysis cont.....
Phosphofructokinase-1 (PFK-1) (fructose-1P + ATP → fructose-1,6-bisP + ADP)
Enzyme activity inhibited by: (3)
* increased ATP concentration
* increased citrate concentration
* Also glucagon, adrenaline (indirectly)
60
3. Regulation of glycolysis cont.....
Pyruvate kinase (phosphoenolpyruvate + ADP → pyruvate + ATP)
Activity stimulated by: (2)
Activity inhibited by: (2)
Fructose-1,6-bisphosphate
Insulin
ATP
glucagon
61
Lactate dehydrogenase (pyruvate + NADH → lactate + NAD+)
Activity stimulated by: (3)
increased pyruvate
increased NADH
decreased NAD+
62
What are the fates of glucose-6-phosphate?
63
What is the pentose phosphate pathway (hexose monophosphate shunt)? (6)
64
What is the Synthesis of glycogen (glycogenesis) from glucose-6-phosphate? (8)
65
Whole body view of blood glucose homeostasis:
66
Blood glucose homeostasis
Glucose homeostasis is aimed at:
* Maintaining blood glucose concentration at 4.1 – 5.9 mmol/l
67
Excess blood glucose
* glucose is removed from the blood when it is in ______
* stored as ______ (in liver and muscle)
* stored as fat
excess
glycogen
68
The primary organ of glucose homeostasis when glucose concentration is decreased is the ______.
liver
69
Decreased blood glucose concentration
* liver glycogen stores are utilised
* the synthesis of glucose occurs
* _______ fat instead of glucose when little/no carbohydrate is eaten
catabolism
70
What is the process of the regulation of glycogen synthesis (glycogenesis? (9)
