Cellular Metabolism Flashcards
Catabolic reactions
The breaking down of large molecules to smaller molecules which releases energy and heat
Anabolic reactions
Used to build larger molecules from smaller molecules
What is an oxidation- reduction reaction
Where electron transfer occurs and it is carried out by dehydrogenases
What is a ligation reaction
It is the formation of covalent bonds and requires ATP cleavage
What is an isomerization reaction
Rearrangement of atoms to form isomers and it is catalysed by isomerases
What is a group transfer reaction
Transfer of a functional group from one molecule to another. It is catalysed by kinases
What is a hydrolytic reaction
Cleavage of bonds by the addition of water
Addition or removal of functional groups
Addition of functional groups to double bonds or their removal from double bonds
What are the 6 types of metabolic reactions present ?
Oxidation-reduction, ligation, isomerization, group transfer, hydrolytic and addition or removal of functional groups
What is step 1 of glycolysis
Glucose phosphorylated to glucose-6-phosphate by hexokinase
What is step 2 of glycolysis ?
Isomerization reaction where glucose-6-phosphate is converted to fructose-6-phosphate
What does phosphofructokinase do in step 3 of glycolysis?
It phosphorylates fructose-6-phosphate to form fructose-1,6-biphosphate which now be split into equal halves later on
What happens in step 4 of glycolysis?
Fructose -1,6-biphosphate is broken down to form 2 high energy compounds ( both contain phosphate groups).
What happens to dihdroxyacetone phosphate in step 5 of glycolysis?
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 )
What happens to the 2 molecules of G3P?
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
What happens to the molecule of 1,3-biphosphateglycerate ( step 7 of glycolysis)?
It is converted to 3-phosphoglycerate and is catalysed by phosphoglycerate kinase.
3-phosphoglycerate ->
2-phosphoglycerate is removal and addition of phosphate group, catalysed by phosphoglycerate mutate
What does enolase do in step 9 of glycolysis?
It removes water from 2-phosphoglycerate to form phosphoenolpyruvate ( double bond is formed). It is a hydration reaction
What happens in step 10 of glycolysis (last stage)?
Phosphoenolpyruvate us converted to pyruvate by pyruvate kinase ( group transfer reaction) . ADP -> ATP.
What is the net result of glycolysis?
2 ATP molecules, 2 NADH molecules and 2 molecules of pyruvate (for every 1 molecule of glucose)
What can pyruvate be used to do ?
It can be used to produce alcohol, generation of lactate, Creatine phosphate and production of acetyl co A
What enzymes are involved in the fermentation of alcohol from pyruvate?
Pyruvate decarboxylase ( H+ -> CO2) and alcohol dehydrogenase ( NAD + is regenerated)
Pyruvate-> acetaldehyde->ethanol
What enzyme is used in the generation of lactate ?
Lactate dehydrogenase - allows NAD+ to be regenerated which allows glycolysis to continue (NAD+ is required in step 6 of glycolysis) in low 02 conditions
What is the equation for Creatine phosphate ?
Creatine phosphate -> creatine + ATP
Catalysed by creatine kinase
What happens to pyruvate in aerobic conditions?
It forms acetyl co A in the link reaction in mitochondria.
What is the enzyme used in the formation of acetyl co A from pyruvate?
Pyruvate dehydrogenase complex. CO2 and NADH are also formed
Why is acetyl Co A easily hydrolysed to then join with oxaloacetate?
The thioester bond is a high energy linkage so easily hydrolysed
What causes Beri- Beri Disease?
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.
Symptoms of Beri Beri?
Damage to peripheral nervous system, weakness of muscles and decreased cardiac output. Brain is also particularly vulnerable as it relies on glucose metabolism.
What is the net result of the Krebs Cycle?
3 NADH, 1 GTP( equiv to 1 molecule of ATP, 1FADH2 and 2 molecules of CO2
Where does the Krebs cycle take place?
The mitochondrial matrix
What fundamentally occurs in amino acid degradation ?
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
What 7 molecules are formed from the degradation of the 20 amino acids?
Pyruvate, acetoacetyl CoA, acetyl CoA, alpha-ketoglutarate, succinylcholine CoA, fumarate and oxaloacetate
What is a transamination reaction?
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.
What is alanine and alphakerogluterate converted to?
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
Why is a shuttle needed to move NADH?
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)
Where is the glycerol-phosphate shuttle used?
Skeletal muscle, brain
Where is the Maltate-aspartate shuttle used
Liver, kidney and heart
How many molecules of ATP are produced from the Krebs Cycle?
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
What happens in TCA cycle defects in cancer?
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)
Why can the amino acids serine, threonine and tyrosine be phosphorylated?
They all contain OH groups
