Cellular Metabolism

Question 1

Catabolic reactions

Answer 1

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

Question 2

Anabolic reactions

Answer 2

Used to build larger molecules from smaller molecules

Question 3

What is an oxidation- reduction reaction

Answer 3

Where electron transfer occurs and it is carried out by dehydrogenases

Question 4

What is a ligation reaction

Answer 4

It is the formation of covalent bonds and requires ATP cleavage

Question 5

What is an isomerization reaction

Answer 5

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

Question 6

What is a group transfer reaction

Answer 6

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

Question 7

What is a hydrolytic reaction

Answer 7

Cleavage of bonds by the addition of water

Question 8

Addition or removal of functional groups

Answer 8

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

Question 9

What are the 6 types of metabolic reactions present ?

Answer 9

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

Question 10

What is step 1 of glycolysis

Answer 10

Glucose phosphorylated to glucose-6-phosphate by hexokinase

Question 11

What is step 2 of glycolysis ?

Answer 11

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

Question 12

What does phosphofructokinase do in step 3 of glycolysis?

Answer 12

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

Question 13

What happens in step 4 of glycolysis?

Answer 13

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

Question 14

What happens to dihdroxyacetone phosphate in step 5 of glycolysis?

Answer 14

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 )

Question 15

What happens to the 2 molecules of G3P?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

3-phosphoglycerate ->

Answer 17

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

Question 18

What does enolase do in step 9 of glycolysis?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is the net result of glycolysis?

Answer 20

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

Question 21

What can pyruvate be used to do ?

Answer 21

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

Question 22

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

Answer 22

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

Pyruvate-> acetaldehyde->ethanol

Question 23

What enzyme is used in the generation of lactate ?

Answer 23

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

Question 24

What is the equation for Creatine phosphate ?

Answer 24

Creatine phosphate -> creatine + ATP

Catalysed by creatine kinase

Question 25

What happens to pyruvate in aerobic conditions?

Answer 25

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

Question 26

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

Answer 26

Pyruvate dehydrogenase complex. CO2 and NADH are also formed

Question 27

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

Answer 27

The thioester bond is a high energy linkage so easily hydrolysed

Question 28

What causes Beri- Beri Disease?

Answer 28

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.

Question 29

Symptoms of Beri Beri?

Answer 29

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

Question 30

What is the net result of the Krebs Cycle?

Answer 30

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

Question 31

Where does the Krebs cycle take place?

Answer 31

The mitochondrial matrix

Question 32

What fundamentally occurs in amino acid degradation ?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

What is a transamination reaction?

Answer 34

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.

Question 35

What is alanine and alphakerogluterate converted to?

Answer 35

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

Question 36

Why is a shuttle needed to move NADH?

Answer 36

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)

Question 37

Where is the glycerol-phosphate shuttle used?

Answer 37

Skeletal muscle, brain

Question 38

Where is the Maltate-aspartate shuttle used

Answer 38

Liver, kidney and heart

Question 39

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

Answer 39

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

Question 40

What happens in TCA cycle defects in cancer?

Answer 40

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)

Question 41

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

Answer 41

They all contain OH groups