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Cellular Metabolism Flashcards

1
Q

Catabolic reactions

A

The breaking down of large molecules to smaller molecules which releases energy and heat

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2
Q

Anabolic reactions

A

Used to build larger molecules from smaller molecules

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3
Q

What is an oxidation- reduction reaction

A

Where electron transfer occurs and it is carried out by dehydrogenases

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4
Q

What is a ligation reaction

A

It is the formation of covalent bonds and requires ATP cleavage

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5
Q

What is an isomerization reaction

A

Rearrangement of atoms to form isomers and it is catalysed by isomerases

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6
Q

What is a group transfer reaction

A

Transfer of a functional group from one molecule to another. It is catalysed by kinases

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7
Q

What is a hydrolytic reaction

A

Cleavage of bonds by the addition of water

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8
Q

Addition or removal of functional groups

A

Addition of functional groups to double bonds or their removal from double bonds

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9
Q

What are the 6 types of metabolic reactions present ?

A

Oxidation-reduction, ligation, isomerization, group transfer, hydrolytic and addition or removal of functional groups

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10
Q

What is step 1 of glycolysis

A

Glucose phosphorylated to glucose-6-phosphate by hexokinase

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11
Q

What is step 2 of glycolysis ?

A

Isomerization reaction where glucose-6-phosphate is converted to fructose-6-phosphate

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12
Q

What does phosphofructokinase do in step 3 of glycolysis?

A

It phosphorylates fructose-6-phosphate to form fructose-1,6-biphosphate which now be split into equal halves later on

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13
Q

What happens in step 4 of glycolysis?

A

Fructose -1,6-biphosphate is broken down to form 2 high energy compounds ( both contain phosphate groups).

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14
Q

What happens to dihdroxyacetone phosphate in step 5 of glycolysis?

A

It is isomerise good form a more useful and high energy compound Glyeraldehyde-3-phosphate. Catalysed by triose phosphate isomerase ( if there is a deficiency in this, most sufferers die within first 6 years of life )

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15
Q

What happens to the 2 molecules of G3P?

A

Redox reaction occurs and NAD+ is used as the reducing agent . NADH is formed which can be used to generate ATP in oxidative phosphorylation later on

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16
Q

What happens to the molecule of 1,3-biphosphateglycerate ( step 7 of glycolysis)?

A

It is converted to 3-phosphoglycerate and is catalysed by phosphoglycerate kinase.

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17
Q

3-phosphoglycerate ->

A

2-phosphoglycerate is removal and addition of phosphate group, catalysed by phosphoglycerate mutate

18
Q

What does enolase do in step 9 of glycolysis?

A

It removes water from 2-phosphoglycerate to form phosphoenolpyruvate ( double bond is formed). It is a hydration reaction

19
Q

What happens in step 10 of glycolysis (last stage)?

A

Phosphoenolpyruvate us converted to pyruvate by pyruvate kinase ( group transfer reaction) . ADP -> ATP.

20
Q

What is the net result of glycolysis?

A

2 ATP molecules, 2 NADH molecules and 2 molecules of pyruvate (for every 1 molecule of glucose)

21
Q

What can pyruvate be used to do ?

A

It can be used to produce alcohol, generation of lactate, Creatine phosphate and production of acetyl co A

22
Q

What enzymes are involved in the fermentation of alcohol from pyruvate?

A

Pyruvate decarboxylase ( H+ -> CO2) and alcohol dehydrogenase ( NAD + is regenerated)

Pyruvate-> acetaldehyde->ethanol

23
Q

What enzyme is used in the generation of lactate ?

A

Lactate dehydrogenase - allows NAD+ to be regenerated which allows glycolysis to continue (NAD+ is required in step 6 of glycolysis) in low 02 conditions

24
Q

What is the equation for Creatine phosphate ?

A

Creatine phosphate -> creatine + ATP

Catalysed by creatine kinase

25
Q

What happens to pyruvate in aerobic conditions?

A

It forms acetyl co A in the link reaction in mitochondria.

26
Q

What is the enzyme used in the formation of acetyl co A from pyruvate?

A

Pyruvate dehydrogenase complex. CO2 and NADH are also formed

27
Q

Why is acetyl Co A easily hydrolysed to then join with oxaloacetate?

A

The thioester bond is a high energy linkage so easily hydrolysed

28
Q

What causes Beri- Beri Disease?

A

Beri Beri Disease is caused by a deficiency in thiamine which is a cofactor in the PDH complex and catalysed the formation of acetyl coA . Affects glucose metabolism.

29
Q

Symptoms of Beri Beri?

A

Damage to peripheral nervous system, weakness of muscles and decreased cardiac output. Brain is also particularly vulnerable as it relies on glucose metabolism.

30
Q

What is the net result of the Krebs Cycle?

A

3 NADH, 1 GTP( equiv to 1 molecule of ATP, 1FADH2 and 2 molecules of CO2

31
Q

Where does the Krebs cycle take place?

A

The mitochondrial matrix

32
Q

What fundamentally occurs in amino acid degradation ?

A

The amino group is removed ( excreted as urea) and the carbon skeleton is either used in the production of glucose or fed into the Krebs Cycle

33
Q

What 7 molecules are formed from the degradation of the 20 amino acids?

A

Pyruvate, acetoacetyl CoA, acetyl CoA, alpha-ketoglutarate, succinylcholine CoA, fumarate and oxaloacetate

34
Q

What is a transamination reaction?

A

Group transfer reactions where the amine group is transferred from an amino acid to a keto acid to produce a new amino acid and keto acid.

35
Q

What is alanine and alphakerogluterate converted to?

A

Pyruvate and glutamate through the action of alanine aminotransferase . Pyruvate can enter Krebs cycle and glutamate is made into alpha-ketoglutarate generating NH4+ which is eventually made into urea

36
Q

Why is a shuttle needed to move NADH?

A

NADH is produced in the glycolysis in the cytoskeleton but is needed in the mitochondria to be used in oxidative phosphorylation and to regenerate NAD+ ( finite amount present and without NAD+ , glycolysis would stop)

37
Q

Where is the glycerol-phosphate shuttle used?

A

Skeletal muscle, brain

38
Q

Where is the Maltate-aspartate shuttle used

A

Liver, kidney and heart

39
Q

How many molecules of ATP are produced from the Krebs Cycle?

A

Oxidation of 1 acetyl CoA gives 3x NADH, 1x FADH2, 1xGTP = 12 ATP
Three ATP molecules are formed from the reoxidation of each NADH
Two ATP molecules are formed by FADH2

40
Q

What happens in TCA cycle defects in cancer?

A

Mutations in Isocitrate Dehydrogenase , Succinate Dehydrogenase and Fumerase decrease Krebs Cycle activity and form lactate ( even in sufficient O2) . This happens in cancerous cells ( Warburg effects)

41
Q

Why can the amino acids serine, threonine and tyrosine be phosphorylated?

A

They all contain OH groups

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