MEH 3 - Energy Production Flashcards

1
Q

What is stage 1 of catabolism?

A

Breakdown to building blocks

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2
Q

Where/how is stage 1 of catabolism carried out in the body?

A
  • SALIVA contains amylase
  • the PANCREAS contains amylase
  • SMALL INTESTINE contains disaccharidases
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3
Q

What are the three types of lactase deficiency?

A
  • primary lactase deficiency (absence of lactase persistence allele)
  • secondary lactase deficiency (caused by injury to small intestine)
  • congenital lactase deficiency (autosomal recessive defect in lactase gene)
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4
Q

What are the symptoms of lactose intolerance?

A
  • bloating/cramps
  • flatulence
  • diarrhoea
  • vomiting
  • ‘rumbling’ stomach
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5
Q

How are monosaccharides absorbed into the blood?

A
  • active transport by sodium dependent glucose transporter (SGLT1)
  • facilitated diffusion via GLUT2 transport proteins into blood supply
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6
Q

Where are GLUT2 and GLUT4 proteins found?

A
  • GLUT2 - kidney, liver, pancreatic beta cells, small intestine
  • GLUT4 - adipose tissue, striated muscle
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7
Q

Which cells have an absolute requirement for glucose as a food?

A
  • red blood cells
  • neutrophils
  • innermost cells of kidney medulla
  • lens of the eye
  • brains prefers glucose but can use ketone bodies
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8
Q

What is stage two of catabolism?

A
  • breakdown to metabolic intermediates

- release of reducing power and energy

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9
Q

What are the functions of glycolysis?

A
  • oxidation of glucose
  • NADH production
  • synthesis of ATP from ADP
  • production of C6 and C3 intermediates
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10
Q

Can glycolysis occur anaerobically?

A

Yes - with the addition of an enzyme (PDH) it is the only pathway that can operate anaerobically.

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11
Q

How much ATP and NADH is produced in glycolysis?

A
  • 2 ATP produced per glucose

- 2 NADH produced per glucose

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12
Q

Which enzyme converts glucose into glucose-6-P?

A

Hexokinase (or glucokinase in the liver)

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13
Q

Which enzyme converts fructose-6-P into fructose 1,6-bis-P?

A

Phosphofructokinase-1

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14
Q

Which enzyme converts phosphoenolpyruvate into pyruvate?

A

Pyruvate kinase

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15
Q

Why is glucose phosphorylated?

A

It makes glucose negatively charged so it cant pass back through the plasma membrane. It also increases reactivity to permit subsequent steps.

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16
Q

How many steps are there in glycolysis?

A

10

17
Q

Which steps of glycolysis use ATP?

A

1 and 3

18
Q

Which steps of glycolysis form ATP?

A

7 and 10, which occur twice per glucose

19
Q

Why is reaction 10 (conversion of phosphoenolpyruvate to pyruvate) irreversible?

A

Large -ve delta G

20
Q

How is glycolysis regulated?

A
  • Phosphofructokinase is the main regulator.
  • allosteric regulation in muscle
  • hormonal regulation in liver
  • hexokinase product inhibition
  • metabolic regulation
  • pyruvate kinase regulation
21
Q

How do hormonal and allosteric regulation take place?

A

Allosteric:

  • inhibited by high ATP
  • stimulated by high AMP

Hormonal:

  • stimulated by insulin
  • inhibited by glucagon
22
Q

What is glycerol phosphate?

A
  • byproduct of step 4 and 5 of glycolysis

- important to triglyceride and phospholipid synthesis

23
Q

What is 2,3-bisphosphoglycerate?

A
  • 1,3-bisphopsphoglycerate (glycolysis intermediate) can be converted into this
  • produced in red blood cells
  • regulator of haemoglobin O2 affinity
24
Q

What is lactate dehydrogenase used for?

A

It converts NAD+ to NADH and vice versa, allowing continued aerobic respiration in tissues, the heart and the liver and kidney

25
Q

What is lactic acidosis?

A

Occurs when plasma lactate rises above 5 mM, and blood pH is lowered

26
Q

What is hyperlactaemia?

A

A less severe form of lactic acidosis when plasma lactate reaches 2-5mM, but there is no change in blood pH due to its buffering capacity

27
Q

What is normal plasma lactate concentration?

A

Less than 1 mM

28
Q

How is the galactose from milk digested?

A
  • milk splits into glucose and galactose
  • galactose turned into galactose-1P by galactokinase
  • galactose-1P converted into glucose-1P by uridyl transferase, then converted into glucose-6P and undergoes glycolysis
  • galactose-1P can also be converted into UDP-galactose by UDP-galactose epimerase
  • it is then converted into UDP-glucose, which forms glycogen
29
Q

Describe fructose metabolism

A
  • using ATP, converted into fructose-1P by fructokinase
  • aldolase converts into glyceraldehyde and DHAP
  • triose kinase (uses ATP) and TPI convert these into 2 x glyceraldehyde-3-P
  • these undergo glycolysis
30
Q

What is the difference between essential fructosuria and fructose intolerance?

A

Essential fructosuria is fructose in urine due to missing fructokinase.
Fructose intolerance is fructose-1P accumulating in liver due to missing aldolase.

31
Q

What does the pentose phosphate pathway start with?

A

Glucose-6-phosphate

32
Q

The pentose phosphate pathway is an important source of NADPH. What is this required for?

A
  • reducing power for biosynthesis
  • maintenance of GSH levels
  • detoxification reactions
33
Q

The pentose phosphate pathway produces C5-sugar ribose. What is this required for?

A

Synthesis of nucleotides, DNA and RNA.

34
Q

What is the rate limiting enzyme in the pentose phosphate pathway?

A

Glucose-6-phosphate dehydrogenase

35
Q

True or false - both ATP and CO2 are produced in the pentose phosphate pathway?

A

False - only CO2 is produced