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Medicine Semester 1 > Metabolism - Energy Reactions 2 > Flashcards

Metabolism - Energy Reactions 2 Flashcards

1
Q

During strenuous exercise, how much lactate can be generated?

A

30g per 5 minutes

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2
Q

What pathological situations can cause lactate build up?

A

Shock

Congestive Heart Failure

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3
Q

What damage is required to cause Congestive Heart Disease?

A

Damage to heart valves or left ventricular muscle. Or both.

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4
Q

Why is left ventricular heart failure congestive?

A

There is back pressure of blood.

Causes congestion of organs (lungs)

Fluid accumulation results in pulmonary oedema

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5
Q

How does cardiogenic shock result from left ventricular heart failure?

A

Pulmonary oedema causes reduced arterial blood flow from the heart. This results in peripheral circulatory failure.

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6
Q

What is a normal blood lactate concentration?

A
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7
Q

Why is hyperlactaemia generally not a physiological problem?

A

At 2-5mM, this is below renal threshold.

Buffering capacity can cope to avoid fall in pH

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8
Q

Where can you get fructose from?

A

Cane / Beet sugar

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9
Q

What is sucrose?

A

A disaccharide of Fructose and Glucose monomers.

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10
Q

What are the clinical consequences of enzyme deficiency in Fructose metabolism?

A

If low fructokinase - fructosuria. No clinical signs.

If low Aldolase, there is F-1-P accumulation which causes liver damage

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11
Q

How common is galactosaemia?

A

Approximate incidence of 1 in 30,000 births

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12
Q

What enzymes are involved in Galactose Metabolism?

A

Galactokinase

Galactose-1-P uridyl transferase

UDP-galactose 4’ epimerase

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13
Q

What is the most common enzyme deficiency for galactosaemia?

A

Galactose 1P uridyl transferase

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14
Q

Where is the activity of the Pentose Phosphate Pathway highest?

A

Liver - lipid synthesis

Adipose Tissue - Lipid synthesis

Bone Marrow - nucleotides for dividing tissues

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15
Q

How much lactate is produced per day in normal circumstances?

A

Roughly 40 to 50g per 24 hours.

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16
Q

In cases of galactosaemia, what enzyme is activated to produce a novel new product?

A

Aldose reductase - high Km value

Generation of Galactitol

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17
Q

What is the consequence of coenzyme use in Galactitol formation?

A

NADPH is used and converted to NADP.

Depletion results in inability to maintain free SH (cysteine) groups.

Leads to cross-linking and structural damage. S-S bridges form, and cataracts can result for example.

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18
Q

What can 3 C5 sugars be converted to from the Pentose phosphate pathway?

A

Fructose 6 Phosphate (x2)

1 Glyceraldehyde 3 Phosphate

19
Q

Give 3 functions if the Pentose Phosphate Pathway

A
  1. NADPH production for biosynthetic reducing power, e.g. In lipid synthesis.
  2. NADPH production for maintenance of free Cysteine residues (SH) and avoiding formation of disulphide bridges
  3. Production of C5 sugars for nucleotide synthesis in dividing tissues such as bone marrow.
20
Q

Where is lactate typically metabolised?

A

Heart and Liver

21
Q

What reaction to Lactate Dehydrogenase catalyse?

A

NADH + H + Pyruvate –> Lactate + NAD

22
Q

Without aldose, what can result?

A

F-1-P accumulation in the liver, which may cause liver damage

23
Q

Phosphofructokinase 1 is involved in what stage, step and reaction in CHO metabolism?

A

Glycolysis

Step 3

Converts F-6-P to Fructose 1,6 phosphate

24
Q

What is lactate used for in the liver?

A

Gluconeogenesis

25
Name 3 conditions which may disrupt use of lactate for gluconeogenesis in the liver.
Thiamine (Vitamin B1) Alcoholism - high NADH conc. produced, causing product inhibition so reduced production of pyruvate from lactate. Liver disease - again, impaired production of pyruvate from lactate
26
How is Galactose 1 P converted to Glucose 1 P? (2 steps)
1. UDP Galactose is converted to UDP Glucose through UDP- Galactose 4' Epimerase activity. 2. The UDP of UDP-Glucose is then transferred to Galactose in exchange for the phosphate group, through activity of Galactose 1-P Uridyl Transferase.
27
What enzyme catalyses reaction of PEP to Pyruvate?
Pyruvate Kinase
28
Give 3 characteristic features of The Pentose Phosphate Pathway
1. No ATP produced 2. Irreversible due to loss of CO2 3. G6P dehydrogenase activity is controlled by NADP+:NADPH ratio.
29
How does the heart muscle utilise lactate?
Converts it to CO2 (Metabolised this way, whereas it is used for Pyruvate production, gluconeogenesis, in the liver
30
What enzyme converts 1,3-BPG to 2,3-BPG?
BPG mutate
31
What is important with regards to NAD+ and RBCs?
NAD+ is usually regenerated in stage 3 and 4 of metabolism. Stage 3 and 4 of metabolism does not occur in RBCs.
32
Where is lactate usually produced?
Liver and Heart
33
Where are disaccharidases found?
Brush border of the epithelium of the small intestine.
34
Where is supply of Oxygen usually reduced in the body.
Muscles and gut
35
Why can glycolysis stop at step 6 of glycolysis?
NAD+ is not regenerated. Build up of NADH results in product inhibition, so 1,3 BPG cannot be produced
36
What can increase phosphofructokinase 1 activity in the liver? How?
A high Insulin:Glucagon ratio. Dephosphorylation - helps to produce more energy from glycolysis through concertive effect on increasing enzyme activity.
37
What the effect on Pyruvate Kinase activity in case of high insulin:Glucagon ratio?
Increases. Can produce energy from glycolysis. Insulin signals there is plenty of energy to get through metabolism
38
What form of allosteric regulation occurs at step 3 of glycolysis?
At muscle, allosteric inhibition by high ATP:AMP ratio
39
How can G6PDH deficiency result in anaemia?
1. NAPDH reduced. 2. Not able to maintain SH groups in RBCs 3. Aggregates of proteins form, due to disulphide bond formation. 4. Heinz Bodies form 5. Haemolysis results Note: will also see build up of bilirubin and therefore jaundice.
40
For what pathway is Thiamine important? Why?
Pentose Phosphate Pathway. For NADPH production.
41
Name 2 diseases caused by thiamine deficiency.
BeriBeri Wernicke-Korsakoff's Syndrome
42
Wernicke-Korsakoff's syndrome is characterised how?
Patient develops short term memory problems and confabulations.
43
List 3 defining features of Wernicke's encephalopathy.
Nystagmus (jerky eye movement) Opthalmoplegia Ataxia

Medicine Semester 1 (6 decks)

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