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Foundations of Medicine > Metabolism > Flashcards

Metabolism Flashcards

1
Q

How is energy produced in the body?

A

Through the breakdown of glucose, proteins and lipids

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2
Q

What is glycolysis?

A

Process by which glucose is broken down into pyruvate.

It produces a net gain of 2 ATP

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3
Q

What is the first stage of glycolysis?

A

Phosphorylation of glucose to glucose 6 phosphate.
Catalysed by hexokinase.
Uses 1 ATP
Irreversible reaction ΔG = -ve

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4
Q

What is the second stage of glycolysis?

A

Glucose 6 phosphate to fructose 6 phosphate.

Reversible.

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5
Q

What is the third stage of glycolysis?

A 
Phosphorylation of fructose 6 phosphate to fructose 1-6 biphosphate. 
Catalysed by phosphofructokinase 1. 
Uses 1 ATP. 
Irreversible reaction ΔG = -ve
Commitment step.
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6
Q

What is the fourth stage of glycolysis?

A

Fructose 1-6 biphosphate to G3P and dihydroxyacetone phosphate.
Reversible

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7
Q

What is the fifth stage of glycolysis?

A

Dihydroxyacetone phosphate to G3P

Reversible

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8
Q

What is the sixth stage of glycolysis?

A

G3P to 1,3 - Bisphosphoglycerate.

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9
Q

What is the seventh stage of glycolysis?

A

1,3 - Bisphosphoglycerate to 3-phosphoglycerate.

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10
Q

What is the eighth stage of glycolysis?

A

3-phosphoglycerate to 2-phosphoglycerate

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11
Q

What is the ninth stage of glycolysis?

A

2-phosphoglycerate to PEP

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12
Q

What is the tenth stage of glycolysis?

A

Phosphoenolpyruvate to ADP producing pyruvate
Catalysed by pyruvate kinase
2 ATP produced
Irreversible reaction ΔG = -ve

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13
Q

What is one of the limiting factors for glycolysis?

A

Presence of NAD, all fates of glucose produce NAD which replenishes the store. This is known as redox balance.

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14
Q

What are the fates of glucose ?

A
  • Ethanol in yeast
  • Lactate when oxygen is lacking and in RBCs which don’t have any mitochondria
  • Acetyl CoA when oxygen is present.
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15
Q

What is the cori cycle?

A

The conversion of glucose to lactate in the muscle, the lactate then moves to the liver where it is converted back into glucose.

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16
Q

What is glyconeogensis?

A

The reverse of glycolysis. Which contains 4 bypass reactions. The first two are carried out in the mitochondria and the last two are carried out in the cytosol.

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17
Q

What are the bypass reactions ?

A

Reaction A is the conversion of pyruvate to oxaloacetate.
Reaction B is the conversion of oxaloacetate to PEP.
Reaction C is the irreversible conversion of Fructose 1-6 biphosphate back to fructose 6 phosphate by the enzyme 1,6-bisphosphatase.
Reaction D is the irreversible conversion of glucose 6 phosphate back into glucose by 6-phosphatase.

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18
Q

How are galactose and fructose converted to pyruvate?

A

They can come in at many points. Galactose can be converted to glucose 6 phosphate. Fructose can be converted to fructose 6 phosphate or G3P or dihydroxyacetone phosphate.

19
Q

How does drinking alcohol affect glycolysis?

A

Breaking down Alcohol uses a lot of NAD. If there is no NAD then there is no glycolysis.

20
Q

What does the citric acid cycle do?

A

Breaks down acetyl CoA to releases many electrons which can be used to produce ATP later on.

21
Q

Why is the citric acid cycle so efficient?

A

Cyclonical

Only a small number of citric acid cycle molecules can make lots of elections.

22
Q

How does pyruvate become acetyl CoA ?

A

Using the catalyst pyruvate dehydrogenase the pyruvate undergoes decarboxylation, oxidation and group transfer.

23
Q

Describe the pyruvate dehydrogenase enzyme

A

Very large with 10 subunits. E1 carries out the decarboxylation, E2 carried out the acetyl group transfer, E3 recycles lipoyllysine.

24
Q

What is used and produced in one turn of the citric acid cycle?

A

Used - 1 Acetyl CoA

Produced - 2CO2, 3NADH, 3H+, FADH, GTP

25
Q

How is the citric acid cycle controlled?

A

Regulating the enzymes of the irreversible reactions:

  • Regulation of pyruvate dehydrogenase. If there is lots of energy then the enzyme action is slowed by the negative feedback of NADH, Acetyl CoA and ATP. if there is no energy the enzyme action is increased by ADP and pyruvate.
  • Isocitrate dehydrogenase.
  • a-ketoglutarate dehydrogenase
26
Q

How can the citric acid cycle be useful anabolicaly?

A

It produces biosynthetic precursors

27
Q

Where does oxidative phosphorylation occur?

A

In the mitochondria

28
Q

Why does it matter where the electron transport chain occurs?

A

Because although most of the electron carrying metabolites are in the mitochondria already (i.e. the once’s from the B oxidation and the citric acid cycle, the metabolites from glycolysis are outside and have to be brought in.

29
Q

How do you get the metabolites from glycolysis into the mitochondria?

A

Using the glycerol phosphate shuttle. Which is when NADH is converted to FADH to get it across the membrane and so there is a loss of energy.

30
Q

What happens in the electron transport chain ?

A

Complex I = NADH-Q oxidoreductase, passes the electrons from NADH to Q. To do this electrons are passed through a series of Fe-S centres which generates energy which is used to pump H+ into the intermembrane space.
Complex II = Succinate-Q reductase, passes electrons from FADH to Q. To do this electrons are passed through a series of Fe-S centres but here there is no H+ pumping.
Complex III = Q-cytochrome C oxidoreductase takes one of the electrons from Q and passes it to cytochrome C. This generates energy allowing H+ to be pumped into the intermembrane space.
Complex IV = Cytochrome C oxidase takes electrons from Cytochrome C and passes them O2 to produce water. This generates energy which is used to pump H+ to the other side of the membrane.

31
Q

What is the name for the movement of electrons in the ETC?

A

Chemiosmosis.

32
Q

How does the ETC produce ATP?

A

ATP synthase is an protein in the membrane which converts ADP to ATP as H+s flow through it back into the matrix of the mitochondria.

33
Q

Describe the structure of ATP synthase.

A

F0 is a conducting unit containing 11 sub-units one of which connects to
F1 which is the the catalyst for ATP synthase and where the ATP is produced.

34
Q

Describe the binding-change mechanism of the ATP synthase

A

ADP + Pi enter the open subunit in the F1, this the changes conformation so that it has a loose fit before changing conformation again to a tight fit converting ADP into ATP. The tight fit then opens to allow the release of ATP and binding of another ADP + Pi.

35
Q

What is meant by coupling and uncoupling?

A

Coupling is where the membrane is selectively permeable meaning that ATP synthase is functioning, uncoupling is when the membrane is not selectively permeable allowing anything through and meaning that the ATP Synthase doesn’t function but that the tissue gets very hot. This is found in brown fat.

36
Q

How do we get Nitrogen?

A

Through our diet

Through the destruction of other intracellular proteins

37
Q

How many amino acids do we have?

A

There are 20 amino acids, 11 are non-essential and 9 are essential.

38
Q

What are the enzymes that are used in the process of digesting proteins ?

A

Pepsin - Cuts protein’s into peptides
Trypsin and chymotrypsin - Cut proteins and large peptides into small peptides in the small intestine.
Aminopeptidase and carboxypeptidase A and B - Degrade peptides into amino acids in the small intestine.

39
Q

Key words in BioChem 4

A 
Pepsin
trypsin
chymotrypsin
aminopeptidase
carboxypeptidases
Phenylalanine 
Tyrosine
PAH enzyme
40
Q

What is PKU?

A

A serious condition where there is a failure to convert phenylalanine to tyrosine. It is an autosomal recessive disorder where there is a lack of PAH.

41
Q

How is PKU detected?

A

It is normally picked up neonatally on a heel prink test. If it wasn’t detected it would cause problems with feeding, irritation and left too long may cause mental developmental and neurological features.

42
Q

How is PKU treated?

A

Low protein diet
Careful maintenance of Phe levels (120-360)
Carful maintenance of Tyr levels

43
Q

How is nitrogen removed from the body?

A

Through the urine, through the conversion of ammonia to urea.

44
Q

What are some conditions that can arise as a result of problems in the urea cycle?

A

OTC deficiency causing hyperammonaemia.

Foundations of Medicine (25 decks)

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