Glycolysis and the TCA Flashcards
What is the main aim of metabolism?
converting an energy source into carbon dioxide and water
Name the 2 pathways that metabolism is split into?
- Anabolic
2. Catabolic
What is the anabolic pathway of metabolism?
These are pathways concerned with the synthesis of cellular components
They decrease entropy and are reductive in nature
What is the catabolic pathway of metabolism?
These pathways are concerned with the degradation of cellular components
They are energy liberating
Name the currency of energy
ATP
How is ATP suited to its job
As it is unstable energy and energy rich
Name the bond that makes ARP energy rich
The acid anhydride bond
Why are the acid anhydride bonds energy rich?
- Due to charge repulsion between the adjacent phosphate groups
Each negative charge repels one another making the molecule less stable than it would be otherwise
2 .Due to the resonance of phosphate ions
Define oxidation
The removal of electrons and protons
What type of reaction is oxidation
Exogenic
Name the ultimate electron acceptor
Oxygen
What does TCA stand for?
Tricarboxylic acid cycle
Name the most common fuel in mammals?
GLUCOSE
Why is glucose important?
It is the only fuel that the brain uses
Describe the structure of glucose
It tends to have a ring conformation
Briefly happens to glucose molecules in glycolysis?
Glucose is converted into pyruvate
How can pyruvate be further broken down?
- Complete oxidation
2. Fermentation
Does fermentation or complete oxidation produce the most free energy ?
complete oxidation
Name the 2 parts of glycolysis
- Investment phase (costs us ATP)
2. Return phase
Name the stages of the ATP consuming phase of glycolysis?
- Phosphorylation of glucose into G-6P
- Isomerisation of G-6P into fructose-6-phosphate
- Phosphorylation of fructose-6-phosphate into fructose 1,6-bisphosphate
- Break down of fructose 1,6-bisphosphate into GAP and DHAP
Go though the first step of glycolysis
Glucose enters the cell using a transport protein and is phosphorylated to give Glucose – 6 Phosphate (G-6P)
What does glucose need help to enter the cell?
It cannot diffuse through due to its negative charge
What does the phosphorylation of glucose require?
ATP
What is the phosphorylation of glucose catalysed by?
Hexokinase
What does Hexokinase need to function?
Magnesium
Is Glucose – 6 Phosphate stable or unstable? why?
Unstable due to the addition of a negative charge (Phosphate group )
What does glucose have a preference to form?
A 6 carbon ring
What is isomerisation?
When the molecular component of a compound doesn’t change but the structural arrangement does
What catalysis the Isomerisation of G-6P?
phosphoglucose isomerase
What is Glucose-6-phosphate isomerised into?
- An aldehyde
- Then a ketone
- Finally Fructose-6-phosphate
Name the end product of the iomerisation of glucose-6-phosphate
Fructose-6-phosphate
What happens to fructose-6-phosphate once it has formed?
It is phosphorylated
What does the Phosphorylation of fructose-6-phosphate require?
ATP
What is fructose-6 -phosphate phosphorylated into?
fructose 1,6-bisphosphate
Name the enzyme involved in the Phosphorylation of fructose-6-phosphate
phosphofructokinase (PFK)
Name the rate determining step in glycolysis
The Phosphorylation of fructose-6-phosphate
Why is the Phosphorylation of fructose-6-phosphate the rate determining step of glycolysis?
As the reaction favours the products
What do we need do to fructose-6-phosphate and why?
Need to break it down to release energy
How is fructose-6-phosphate broken down?
By Aldolase
What does is fructose 1,6- biphophate broken down into?
1. Glyceraldehyde 3-phosphate (GAP) 2. Dihydroxyacetone phosphate (DHAP)
Is GAP needed in glycolysis or DHAP (or both)
GAP (Glyceraldehyde 3-phosphate)
What do we need to do to DHAP to make glycolysis more effective?
Convert it into GAP so it can be used in glycolysis
Name the enzyme that converts DHAP into GAP
Triose phosphate
isomerase
Name all the enzyme involved in the ATP consuming stage of glycolysis
- Hexokinase (phosphorylation of glucose into G6P)
- Phosphoglucose isomerase (somerisation of G-6P)
- Phosphofructokinase-1 (Phosphorylates fructose 6-phophate into fructose 1,6-bisphosphate)
- Aldose (Breaks down fructose 1,6-bisphosphate)
- Triose phosphate isomerase (isomerisation of GAP to DHAP)
In a nut shell summarise the ATP consuming phase of glycolysis
The break down of a single 6 carbon molecule to 2 three carbon molecules costing TWO ATPs
How many ATPs are used in the ATP consuming phase of glycolysis?
2 ATPs
What does the ATP generation stage of glycolysis begin with?
Begins with the phosphorylation of Glyceraldehyde -3-phosphate
Name the stages of the ATP generating phase of glycolysis
- phosphorylation of Glyceraldehyde -3-phosphate
- Removal of phosphate from (1,3-BPG) to form
3-phosphoglycerate - 3 phosphoglycerateis converted into 2 phophoglycerbte
- 2- phosphoglycerate is converted into PEP
- PEP loses its phosphate group to form pyruvate and ATP
What is Glyceraldehyde -3-phosphate phosphylated into?
1,3-bisphosphogltcerate
1,3-BPG
What molecules are involved into the phosphorylation of GAP into 1,3- biphophogitcerate
NAD+ and Phosphate
Which enzyme is involved in the phosphorylation of Glyceraldehyde -3-phosphate ?
Glyceraldehyde
3-phosphate
dehydrogenase
What does the Glyceraldehyde
3-phosphate
dehydrogenase result in?
1,3-bisphosphogltcerate
(1,3-BPG)
NADH
H+
Describe 1,3-bisphosphogltcerate
1,3-BPG
It has a high phosphorylation transfer potential
What does the fact that 1,3 BPG having a high phosphorylation transfer potential allow?
Allows for phosphate transferal onto ADP in the next step
What happens to 1,3-bisphosphogltcerate
(1,3-BPG) after it has been formed?
When it is in close proximity to ADP it removes its phosphate group
What does the removal of phosphate from 1,3-bisphosphogltcerate
(1,3-BPG) require?
ADP and H+
Which enzyme aids the removal of phosphate from 1,3-bisphosphogltcerate
(1,3-BPG)?
Phosphoglycerate
kinase
What does the removal of phosphate from 1,3-bisphosphogltcerate
(1,3-BPG) form?
3-phosphoglycerate
and ATP
What happens to the 3-phosphoglycerate once it has formed?
It is converted into 2-phosphoglycerate
Name the enzyme that aids the the conversion of 3-phosphoglycerate into 2- phosphoglycerate
Phosphoglycerate mutase
How can we obtain ATP from 3-phophoglycerate?
3-phophoglycerate is converted in 2-phophoglycerate with the aid of Phosphoglycerate mutase
Then Enolase converts the 2-phophoglycerate into Phosphenolpyruvate
(PEP). This reaction yields ADP
PEP is of high energy and wants to remove its phosphate the removal of this phosphate forms pyruvate and ATP
Which enzyme aids the conversion of 2-phophoglycerate into Phosphenolpyruvate
(PEP)?
Enolase
How does PEP help release an ATP?
PEP is of high energy and wants to remove its phosphate the removal of this phosphate forms pyruvate and ATP
How many ATPs does the ATP consuming phase of glycolysis use?
2
How many ATPs does the ATP generating phase produce?
4
What does the break down of glucose produce overall?
2 ATPs and 2 pyruvate
Is the redox equilibrium of glucose break down balanced?
NO
We used 1 NAD+ to convert GAP into 1,3BPG
What must be regenerated through the metabolism of pyruvate and whY?
NAD+ needs to be regenerated as the redox equilibrium of glucose break down isn’t balanced
State the overall equation for glucose metabolism in glycolysis
Glucose + 2Pi + 2ADP + 2NAD+ -> 2pyruvate + 2ATP + NADH + 2H+ + 2H2O
What can pyruvate be broken down into?
- Ethanol
- Lactase
- Acetyl CoA
Why does fermentation occur?
When there’s a lack of Oxygen
When pyruvate is broken down in a fermentation reaction what happens
- Pyruvate is converted into Acetaldehyde realising CO2
2. Acetaldehyde is converted into ethanol (NAD+ is produced)
Name some organisms that do fermentation
Yeast
What is released when pyruvate is produced into lactate?
NAD+ is produced
When does the conversion of pyruvate into lactate occur?
When theres a lack of oxygen and the body is in need of energy
After glycolysis what does the pyruvate need to enter?
The citric acid cycle
Name the only entry point into the Krebs cycle?
Acetyle CoA
Through which reaction is pyruvate converted into Acetyl CoA?
Through an oxidative decarboxylation
What is the conversion of pyruvate into acetyl CoA mediated by?
Pyruvate dehydrogenase (PDH)
What is pyruvate dehydrogenase?
It is a multi enzyme complex of pyruvate decarboxylase, dihydro transacetylase and
dihydrolipoyl dehydrogenase
Name the enzymes involved in the multi enzyme complex that aids the formation of acetyl CoA
- pyruvate decarboxylase,
- dihydro transacetylase
- dihydrolipoyl dehydrogenase
What is the benefit of having a multi enzyme complex?
All the enzymes are attaches so there is no release of intermediates making the reaction bette
Go through the reactions involved in the pyruvate dehydrogenase (PDH) reaction
- Decarboxylation
- Oxidation
- Acetyl CoA is added
Where does the pyruvate dehydrogenase reaction occur?
In the matrix of the mitochondria
What is produces in the Pyruvate dehydrogenase reaction?
NAD+ is converted into NADH
Talk though the stages of the TCA cycle?
1, Acetyl CoA production
- Acetyl- CoA oxidation in the citric acid cycle
- Electron transfer and oxidative phosphorylation occurs in the electron transport chain
What is the main aim of the TCA cycle?
To harvest high energy electrons from carbon fuel
Talk though the stages of the TCA cycle?
1, Acetyl CoA production
- Acetyl- CoA oxidation in the citric acid cycle
- Electron transfer and oxidative phosphorylation occurs in the electron transport chain
What does the TCA cycle provide?
The substrate for electron transport chain
Precursors for building amino acids, nucleotides and components of blood
What do the intermediates in the TCA cycle provide?
They proves a regulatory barrier
Name the main stages of the citric acid cycle
- Citrate synthase
- break up of the carrier
- Oxidative decarboxylation of isocitrate
- Oxidative
Decarboxylation
(5C to 4C) - Oxidative
Decarboxylation
(5C to 4C) - Oxidation
- Oxidation, hydration
What does hexokinase do?
Catalyses the phosphorylation of glucose into Glucose – 6 Phosphate
What does phosphoglucose isomerase do?
Aids the isomerisation of G-6P
What does phosphofructokinase (PFK) do?
Phosphorylates fructose 6-phophate into fructose 1,6-bisphosphate
What is significant about the Phosphorylation of fructose-6-phosphate ?
It is the rate determine step of glycolysis
What does aldose do?
Breaks down fructose 1,6-bisphosphate into: 1. Glyceraldehyde 3-phosphate (GAP) 2. Dihydroxyacetone phosphate (DHAP)
What does Triose phosphate
isomerase do?
Aids in the conversion of DHAP into GAP
What does Phosphoglycerate
kinase do?
Phosphorylates GAP into 1,3 - BPG
What does Phosphoglycerate
kinase do?
Aids the removal of phosphate from 1,3-bisphosphogltcerate
1,3-BPG
What does Phosphoglycerate mutase do?
Aids in the concversion of 3-phophoglycerate into 2-phophoglycerate
What does enolase do?
Converts 2-phophoglycerate into Phosphenolpyruvate
(PEP)?
What is the condensation of acetyl CoA and oxaloacetate catalysed by?
citrate synthase
What does the equilibrium in the aldol condensation reaction favour?
citrate synthase
What does acetyl CoA react with when it enters the mitochondria?
Reacts with Oxaloacetate
to form citrate and citryl CoA
How many carbons are formed at the end of the first condensation reaction in the citric acid cycle?
2C + 4C=6C
What happens to the citrate in the citric acid cycle?
It is dehydrated then isomerism and hydrated again to form isocitrate
Why does citrate have to be dehydrated before it can be isomerased?
As the hydroxyl group isn’t ideally located o the citrate from oxidative decarboxylation
Name the enzyme that catalyses the isomerisation and hydration of citrate
Aconitase
What happens to isocitrate once it has been formed?
It undergoes oxidative decarboxylation
Name the enzyme that catalyses the oxidative decarboxylation of isocitrate
Isocitrate dehydrogenase
What is formed when oxidative decarboxylation of the isocitrate occurs?
Alpha-ketoglutarat
What is special about the formation of a-ketoglutarat
The rate of formation of a-ketoglutarate determines
the overall rate of the citric acid cycle
What is special about the oxidative decarboxylation of isocitrate
It is the first 4 oxidation-reduction reactions
and generates the first high transfer
high potential electron carrier NADH
What happens after the oxidative decarboxylation of isocitrate ?
Oxidative Decarboxylation of succinyl coA
5C to 4C
What happens after the Decarboxylation of succinyl CoA?
Substrate
level phosphorylation
What happens after substrate level phosphorylation
Oxidation
Name the 3 steps that are irreversible in the citric acid cycle?
- Citrate synthase
- Oxidative decarboxylation of isocitrate
- Oxidative
Decarboxylation
(5C to 4C)
Name the electron acceptor for the oxidation react in the citric acid cycle?
FAD as the reducing power of succinate isn’t sufficient
How many ATPs are yielded in the TCA cycle?
2 ATPs
How many NADH are yielded in the TCA cycle?
6 NADH
How many FADH are yielded in the TCA cycle?
2 FADH
What does Aconitase do?
It catalyses the dehydration, isomerisation and hydration of citrate
What does Isocitrate dehydrogenase do?
It catalyses the the oxidative decarboxylation of isocitrate