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Metabolism > 2. Energy production I Carbohydrates, glycolysis, Pentose phosphate pathway > Flashcards

2. Energy production I Carbohydrates, glycolysis, Pentose phosphate pathway Flashcards

1
Q

What are the main monosaccharides obtained from our diet?

A

Glucose
Fructose
Galactose

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2
Q

What is table sugar made of?

A

Sucrose
Disaccharide
Glucose + fructose

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3
Q

What type of bonds do starch and glycogen have?

A

Alpha 1-4 glucose bonds

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4
Q

Where is amylase found?

A

Saliva

Pancreas - released into duodenum

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5
Q

What does amylase break down? And into what?

A

Polysaccharides Starch & glycogen

Into Monosaccharide glucose

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6
Q

What type of enzymes does the small intestine have?

A

Disaccharides

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7
Q

Name 4 disaccharides

A

Lactase
Sucrose
Pancreatic amylase
Isomaltase

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8
Q

What type of bonds does cellulose contain?

A

Beta 1-4 bonds

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9
Q

What type of food groups is cellulose particularly found in ?

A

Dietary fibre

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10
Q

What is the difference between amylase found in saliva and amylase found in pancreas ?

A

Saliva - breaks down starch/glycogen to dextrins (oligosaccharides)

Pancreas - breaks down starch/glycogen to glucose
Include disaccharides

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11
Q

What is the cause of primary lactase deficiency ?

A

Absence of lactase persistence allele

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12
Q

Does primary lactase deficiency occur in adults or children?

A

Adults

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13
Q

What causes lactose intolerance ?

A

Deficiency of enzyme lactase

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14
Q

What types of food should lactose intolerant patients avoid?

A

Milk
Cheese
Yogurt
Cream

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15
Q

Which type of lactase deficiency is reversible?

A

Secondary lactase deficiency

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16
Q

What causes secondary lactase deficiency ?

A

Injury to small intestine

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17
Q

Can secondary lactase deficiency occur in infants or adults?

A

Both

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18
Q

What is coeliac disease?

A

Inflammation of small intestine

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19
Q

What causes coeliac disease?

A

Adverse reaction to gluten

Gluten is a dietary protein found in 3 types of cereal (wheat, barley, rye)

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20
Q

What is crohns disease?

A

Long term inflammation of the lining of the digestive system.
Anywhere in alimentary canal

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21
Q

What two main symptoms does gastroenteritis cause?

A

Vomiting

Diarrhoea

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22
Q

What are some causes of gastroenteritis ?

A

Food poisoning

Noravirus

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23
Q

Name 4 conditions that can result in secondary lactase deficiency ?

A

Gastroenteritis
Crohn’s disease
Coeliac disease
Ulcerative colitis

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24
Q

What is the most rare form of lactase deficiency ? And what causes it ?

A

Congenital lactase deficiency
Autosomal recessive mutation of lactase gene
Cannot digest breast milk

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25
What are the symptoms of lactose intolerance
``` Bloating Vomiting Diarrhoea Rumbling stomach Flatulence (gas accumulation in alimentary Canal ) ```
26
How does glucose enter from the intestinal lumen into the apical side of the intestinal epithelial cell?
``` Secondary active transport Via SGLT1 (Symporter with sodium) ```
27
How does glucose enter the bloodstream from the basolateral end of the intestinal epithelial cell ?
Via transport protein GLUT 2
28
Which transporter does galactose enter blood through in intestine ?
Glut 2
29
How do monosaccharides go from blood into cells?
Facilitated diffusion via GLUT 1-5 transport proteins
30
Where are GLUT 1 transport proteins found?
Fetal tissue Erythrocytes Blood brain barrier
31
Where are GLUT 2 transport proteins found?
Kidney Liver Pancreas beta cells Small intestine
32
Where are GLUT 3 transport proteins found?
Neurones | Placenta
33
Where are GLUT 4 transport proteins found?
Adipose Striated muscle (Insulin regulated)
34
Where are GLUT 5 transport proteins found?
Spermatozoa | Intestine
35
Which cells can only metabolise glucose?
Erythrocytes Neutrophils Innermost cells of kidney medulla Lens of eye
36
What fuels of energy can the brain use?
Glucose | Ketone bodies
37
When does the brain use ketone bodies?
Times of starvation
38
What is glycolysis?
Intracellular Pathway in which monosaccharides get converted to pyruvate
39
What are the two phases of glycolysis ?
Investment | Payback
40
What is produced at the end of glycolysis per glucose molecule?
2 molecules of pyruvate (each 3 carbon) 2 NADH 2 net ATP
41
How many carbons does one molecule of pyruvate have at the end of glycolysis?
3
42
Where does glycolysis take place in a cell?
Cytoplasm
43
Glycolysis is exergonic, what does this mean?
Accompanied by release of energy
44
Which enzyme has a lower affinity for glucose, hexokinase or glucokinase ?
Hexokinase
45
Which enzyme is inhibited by glucose 6 phosphate?
Hexokinase
46
Which tissue is hexokinase found in?
All
47
Which tissue is glucokinase found in?
Liver
48
What do hexokinase & glucokinase do? Is energy required?
Glucose to glucose 6 phosphate. | 1 molecule of ATP required
49
What does phosphofructokinase-1 do? Does it require energy?
Fructose-6-P to Fructose 1,6-bis-P Uses 1 molecule of ATP
50
In the investment phase which enzymes require ATP and what are the reactions they each catalyse?
1) hexokinase/glucokinase : glucose to glucose-6-P | 2) phosphofructokinase-1 : fructose-6-P to fructose-1,6-bis-P (COMMITTING STEP - ONLY WAY NOW IS GLYCOLYSIS)
51
What is substrate level phosphorylation?
Converting ADP - ATP
52
What is gluconeogenesis ?
Converting pyruvate to glucose
53
In glycolysis how many irreversible steps are there?
3
54
What does pyruvate kinase do? Does it require energy?
Phosphoenolpyruvate to pyruvate No releases 1 molecule of ATP
55
Do cancer cells have a higher rate of glycolysis?
Yes
56
What is 2-18-F-2-deoxyglucose (FDG)? What is it used for ?
RADIOACTIVE MODIFIED HEXOKINASE SUBSTRATE Imaging cancer cells with positron emission tomography
57
In glycolysis what is the key regulator ? And in what 2 ways is it regulated ?
Phosphofructokinase - allosteric regulation & hormonal regulation
58
Where does allosteric regulation of phosphofructokinase occur?
Muscle
59
Where does Hormonal regulation of phosphofructokinase occur?
Liver
60
What inhibits phosphofructokinase?
ATP (MUCLE) (ALLOSTERIC) | INSULIN (LIVER) (HORMONAL)
61
What stimulates phosphofructokinase ?
AMP (MUSCLE) (ALLOSTERIC) | GLUCAGON (LIVER) (HORMONAL)
62
WHICH ENZYME CAN BE REGULATED Hexokinase or glucokinase? By what?
Hexokinase | Inhibited by glucose-6-P
63
What regulates pyruvate kinase?
Stimulated by high insulin, low glucagon
64
How is glycolysis regulated ?
1) phosphofructokinase (stimulated: AMP, Insulin. Inhibited: ATP, glucagon) 2) hexokinase (inhibited: glucose-6-P) 3) pyruvate kinase: (stimulated: high insulin, low glucagon) 4) high NADH, low NAD+ = INHIBITION
65
WHAT TWO IMPORTANT INTERMEDIATES ARE FORMED FROM GLYCOLYSIS?
2,3- BISPHOSPHOGLYCERATE - | GLYCEROL PHOSPHATE
66
What is 2,3-Bisphosphoglycerate?
Produced in erythrocytes Regulates haemoglobin Promotes o2 release from Hb
67
What is the function of glycerol phosphate?
Needed for Triglyceride and phospholipid biosynthesis | Produced in adipose via glycolysis
68
What does the enzyme bisphosphoglycerate mutase do ?
Catalyse | 1/,3-bis phosphoglycerate to 2,3-bis phosphoglycerate
69
What does glycerol 3-phosphate dehydrogenase do?
Catalyse | DIHYDROXYACETONE-P TO GLYCEROL PHOSPHATE
70
How many molecules of NADH is produced per glucose?
2
71
Which enzyme converts pyruvate into lactate & lactate into pyruvate ?
Lactate dehydrogenase
72
When would anaerobic respiration be used by a cell?
- no mitochondria (RBC) - reduced blood supply - little o2 available
73
What happens to lactate that travels to the liver?
- some of it used as an energy source and converted back to pyruvate to be oxidised and release energy - most of it converted back to pyruvate and undergoes gluconeogenesis.
74
What is gluconeogeneis?
Metabolic pathway that results in generation of glucose from certain non-carbohydrate carbon substrates (eg lactate)
75
What happens to lactate that is formed by a cell in anaerobic respiration?
Travels in blood to 1) heart - converted back to pyruvate and used as energy source 2) liver - converted back to pyruvate and undergoes gluconeogenesis.
76
In anaerobic respiration after glycolysis what happens to the NADH?
Reduced back to NAD+ via lactate dehydrogenase
77
What is the normal concentration of lactate in the blood?
<1mM
78
What is the plasma concentration of lactate in hyperlactaemia?
2-5mM and
79
What is the plasma concentration of lactate in lactic acidosis ?
>5mM
80
At what level of lactate can the kidneys not cope with the plasma concentration of lactate?
>5mM | Lactic acidosis
81
What is milk sugar made from?
Lactose = galactose + glucose
82
What is galactosaemia?
Autosomal recessive disorder | Reduced ability to metabolise galactose
83
Galactosaemia can be caused by deficiency in which 3 enzymes?
- galactokinase - uridyl transferase - UDP - galactose epimerase
84
What does galactokinase do?
Galactose to galactose-1P
85
What does uridyl transferase do?
Galactose-1P to glucose-1P
86
What does UDP-galactose epimerase do?
Galactose-1P to UDP-galactose Product can be converted to glycogen for storage
87
Where is fructose metabolised ?
Liver
88
What does the enzyme Fructokinase do? Is energy required?
Fructose to Fructose-1P | Yes 1 molecule of ATP
89
What does the enzyme Aldolase do?
Fructose-1P to glyceraldehyde-3-p (which can undergo glycolysis)
90
Which enzyme is missing in essential fructosuria ?
Fructokinase
91
What are the clinical signs of essential fructosuria?
There are none
92
Which enzyme is missing in fructose intolerance?
Aldolase
93
What organ can be damaged in fructose intolerance ? Why?
Liver due to build up of fructose-1P
94
What is the treatment for fructose intolerance?
Remove fructose from diet
95
What is the function of the pentose phosphate pathway?
1) produce NADPH | 2) produce pentose (C5) sugars needed for synthesis of nucleotides, DNA & RNA
96
How much ATP is produced from the pentose phosphate pathway ?
None
97
Which molecule does the pentose phosphate pathway start with?
Glucose - 6- phosphate
98
What is the rate limiting enzyme in the pentose phosphate pathway?
Glucose 6 phosphate dehydrogenase
99
What is NADPH required for?
- regeneration of glutathione (GSH) - ANTIOXIDANT - FATTY ACID & STEROID BIOSYNTHESIS - REDUCING POWER FOR BIOSYNTHESIS
100
WHAT IS GLUTATHIONE (GSH)?
Antioxidant

Metabolism (4 decks)

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