Metabolism 3 - Glycolysis Flashcards
Glycolysis Six step
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.
Glycolysis second step
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.
Glycolysis ten step
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.
Glycolysis first step
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.
Glycolysis seventh step
The enzyme phosphoglycerokinase transfers a P from 1,3-bisphosphoglycerate to a molecule of ADP to form ATP.
phosphogluco isomerase
enzyme turns glucose 6-phosphate into fructose-6-phosphate
What are the fates of pyruvate?
In anaerobic conditions it can form either lactate (skeletal muscle) or alcohol (yeast)
Describe the process of alcoholic fermentation.
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+.
Describe the process of lactate fermentation.
Pyruvate is converted to lactate¬ catalysed by lactate dehydrogenase¬ regenerating NAD+ from NADH + H+.
Regulation of phosphofructokinase
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.
Glycolysis eight step
The enzyme phosphoglycerate mutase relocates the P from 3-phosphoglycerate from the third carbon to the second carbon to form 2-phosphoglycerate.
Why is the regeneration of NAD+ essential?
NAD* is important¬ used in dehydrogenation of glyceraldehyde 3-phosphate¬ the first stage generating ATP for the body.
What does presence of lactate dehydrogenase in the blood suggest?
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.
When is Creatine phosphate used in the body?
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.
Glycolysis Fourth Step
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.
Glycolysis Summary
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.
What catalyses the generation of acetyl coA from pyruvate?
Pyruvate dehydrogenase catalyses the reaction¬ which produces CO2 and NADH.
What is present in the pyruvate dehydrogenase complex?
- 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
Glycolysis five step
The enzyme triose phosphate isomerase rapidly inter-converts the molecules dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
What disease is caused by a deficiency in thiamine?
Beri-Beri - damage of the peripheral nervous system¬ weakness of the musculature and decreased cardiac output.
What are the key roles of the pyruvate dehydrogenase complex?
- 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.
Define substrate level oxidation
The production of ATP by the direct transfer of a high energy phosphate group from an intermediate substrate in a biochemical pathway to ADP.
Hexokinase
An enzyme that adds a phosphate group to a molecule of glucose
Glycolysis nine step
The enzyme enolase removes a molecule of water from 2-phosphoglycerate to form phosphoenolpyruvate (PEP).
What occurs with glucose metabolism in cancer?
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.
Glycolysis third step
The enzyme phosphofructokinase uses another ATP molecule to transfer a phosphate group to fructose 6-phosphate to form fructose 1, 6-bisphosphate.
