Metabolism 3 - Glycolysis

Question 4

Glycolysis Six step

Answer 4

The enzyme triose phosphate dehydrogenase serves two functions in this step. First the enzyme transfers a hydrogen (H-) from glyceraldehyde phosphate to NAD+ to form NADH. Next triose phosphate dehydrogenase adds a phosphate (P) from the cytosol to the oxidized glyceraldehyde phosphate to form 1, 3-bisphosphoglycerate.

Question 5

Glycolysis second step

Answer 5

The enzyme phosphoglucoisomerase converts glucose 6-phosphate into its isomer fructose 6-phosphate. Isomers have the same molecular formula, but the atoms of each molecule are arranged differently.

Question 6

Glycolysis ten step

Answer 6

The enzyme pyruvate kinase transfers a P from PEP to ADP to form pyruvate and ATP. This reaction yields 2 molecules of pyruvate and 2 ATP molecules.

Question 7

Glycolysis first step

Answer 7

The enzyme hexokinase phosphorylates adds a phosphate group to glucose in the cell’s cytoplasm. In the process, a phosphate group from ATP is transferred to glucose producing glucose 6-phosphate.

Question 9

Glycolysis seventh step

Answer 9

The enzyme phosphoglycerokinase transfers a P from 1,3-bisphosphoglycerate to a molecule of ADP to form ATP.

Question 10

phosphogluco isomerase

Answer 10

enzyme turns glucose 6-phosphate into fructose-6-phosphate

Question 10

What are the fates of pyruvate?

Answer 10

In anaerobic conditions it can form either lactate (skeletal muscle) or alcohol (yeast)

Question 11

Describe the process of alcoholic fermentation.

Answer 11

Pyruvate is converted to acetaldehyde using pyruvate decarboxylase¬ releasing CO2. In the second stage¬ acetaldehyde is converted to ethanol using alcohol dehydrogenase and NADH + H+.

Question 11

Describe the process of lactate fermentation.

Answer 11

Pyruvate is converted to lactate¬ catalysed by lactate dehydrogenase¬ regenerating NAD+ from NADH + H+.

Question 12

Regulation of phosphofructokinase

Answer 12

When the glycolytic pathway is producing plenty of phosphenolpyruvate and ATP, the phosphenolpyruvate can act as a feedback inhibitor to slow the pathway be decreasing the rate of the reaction catalyzed by phosphofructokinase.

Question 13

Glycolysis eight step

Answer 13

The enzyme phosphoglycerate mutase relocates the P from 3-phosphoglycerate from the third carbon to the second carbon to form 2-phosphoglycerate.

Question 13

Why is the regeneration of NAD+ essential?

Answer 13

NAD* is important¬ used in dehydrogenation of glyceraldehyde 3-phosphate¬ the first stage generating ATP for the body.

Question 13

What does presence of lactate dehydrogenase in the blood suggest?

Answer 13

Lactate dehydrogenase is in the blood if the body tissues are damaged. Can be indicative of stroke¬ heart attack¬ liver disease¬ muscle injury¬ muscular dystrophy¬ and pulmonary infarction.

Question 14

When is Creatine phosphate used in the body?

Answer 14

Creatine phosphate is hydrolysed in the body to Creatine¬ catalysed by Creatine kinase. High levels of creative kinase can occur following myocardial infarction¬ and to determine the extent of muscular disease.

Question 15

Glycolysis Fourth Step

Answer 15

The enzyme aldolase splits fructose 1, 6-bisphosphate into two sugars that are isomers of each other. These two sugars are dihydroxyacetone phosphate and glyceraldehyde phosphate.

Question 16

Glycolysis Summary

Answer 16

In summary, a single glucose molecule in glycolysis produces a total of 2 molecules of pyruvate, 2 molecules of ATP, 2 molecules of NADH and 2 molecules of water.

Question 17

What catalyses the generation of acetyl coA from pyruvate?

Answer 17

Pyruvate dehydrogenase catalyses the reaction¬ which produces CO2 and NADH.

Question 18

What is present in the pyruvate dehydrogenase complex?

Answer 18

• Pyruvate decarboxylase with prosthetic group thiamine phosphate (loses a proton) - Lipoamide reductive-transacetylase with a lipoamide prosthetic group (undergoes oxidation and reduction) - Dihydrolipoyl dehydrogenase has prosthetic group FAD - NAD+ and CoA cofactors

Question 19

Glycolysis five step

Answer 19

The enzyme triose phosphate isomerase rapidly inter-converts the molecules dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.

Question 20

What disease is caused by a deficiency in thiamine?

Answer 20

Beri-Beri - damage of the peripheral nervous system¬ weakness of the musculature and decreased cardiac output.

Question 21

What are the key roles of the pyruvate dehydrogenase complex?

Answer 21

• Generate an acetyl group and transfer it to coA so it can enter the TCA cycle. - Regenerate an active PDH complex for the next reactions.

Question 22

Define substrate level oxidation

Answer 22

The production of ATP by the direct transfer of a high energy phosphate group from an intermediate substrate in a biochemical pathway to ADP.

Question 23

Hexokinase

Answer 23

An enzyme that adds a phosphate group to a molecule of glucose

Question 24

Glycolysis nine step

Answer 24

The enzyme enolase removes a molecule of water from 2-phosphoglycerate to form phosphoenolpyruvate (PEP).

Question 25

What occurs with glucose metabolism in cancer?

Answer 25

Glucose metabolism is increased¬ and rapidly metabolised to lactate - this aids tumour growth. There is increased expression of glucose transporters as well as hexokinase and phosphofructokinase.

Question 26

Glycolysis third step

Answer 26

The enzyme phosphofructokinase uses another ATP molecule to transfer a phosphate group to fructose 6-phosphate to form fructose 1, 6-bisphosphate.