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Assignment of General Biochemistry | Fatima khan

Definition



Glycolysis

{Gr
...

Glycolysis is universally found in organisms
...
It can take place with or without oxygen
...
In the absence of oxygen glycolysis
allowed cells to make small amount of ATP through the process of fermentation
...

Glycolysis is important in the cell because glucose is the main source of fuel for tissues in
the body
...
Thus, the intermediates of glycolysis are useful for the synthesis of
amino acid and fats
...
They are
1
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Splitting phase
3
...
10 different enzymes are involved in whole
process
...
Energy Investment Phase:
In energy investment phase, the ATP is used or invested for the conversion of glucose
into different molecules
...


Step no: 1:
In the first step the enzyme “hexokinase or glucokinase” phosphorylates or adds a
phosphate group to glucose in a cells cytoplasm
...
One molecule of ATP is
consumed in this step
...


Step no: 3:
In third step, the enzyme “phosphofructokinase” use another ATP molecule to transfer a
phosphate group F6P to form fructose- 1, 6- biphosphate or FBP
...


2
...


Step no: 4:
In the fourth step, the enzyme “aldolase” split fructose- 1, 6- biphosphate into a ketone
and an aldehyde molecule
...


Step no: 5:
In fifth step, the enzyme for “phosphotriose isomerase” converts DHAP into GAP
...
Thus,
two molecules of GAP are obtained from one molecule of glucose
...
Energy Harvesting Phase:
In energy harvesting phase, the energy ATP is produced from the remaining steps it
involve 5 steps
...


Step no: 6:
In sixth step, the enzyme “3- phosphate dehydrogenase” serves to function in the
reaction
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 Second, GAPDH adds a phosphate to oxidize GAP to form 1, 3biphosphoglycerate (BPG)
...
This is called substrate level
phosphorylation this reaction yield two 3- phosphoglycerate (3PGA) molecule
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Step no: 8:
In the eighth step, the enzyme “phosphoglyceromutase” relocates the phosphate of
3PGA molecule from the 3rd to 2nd carbon to form 2- phosphoglycerate (2PGA)
molecule
...


Step no: 10:
In the last step, the enzyme “pyruvate kinase” transfer a phosphate from PEP to form
pyruvate and ATP
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Assignment of General Biochemistry | Fatima khan

Flow Chart of Glycolysis:

Assignment of General Biochemistry | Fatima khan


Glycolysis Results

Inputs

Outputs

Glucose

2 Pyruvate

2 NAD+

2 NADH

2 ATP

4 ATP (net 2 ATP)

2 ADP+2 P



Krebs cycle or Citric Acid Cycle or
Tricarboxylic Acid Cycle

Krebs cycle or citric acid cycle or tricarboxylic cycle is a cyclic metabolic pathway located
in the matrix of mitochondria
...


Definition
Krebs cycle is a series of chemical reactions used by all aerobic organisms
...

The citric acid cycle is the final common oxidative pathway for carbohydrates, fats and
amino acids
...
About 65 to 70% of the
ATP is synthesized in Krebs cycle
...


Reaction Centre
Krebs cycle takes place in mitochondria
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Cristae are folds of inner membrane that jut
out into matrix
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Assignment of General Biochemistry | Fatima khan

Reactions of Krebs cycle or citric acid cycle or
TCA cycle:
The initial reaction is the “transition reaction” is so called because it connects glycolysis
to Krebs cycle
...
This is an
oxidation reaction, electrons are removed that are used by NAD+ as coenzyme
...


Reaction: 2 Citrate is isomerized to Isocitrate:
In the second reaction, the enzyme “aconitase” dehydrates citrate to form cis- aconitate
an intermediate and again lose water molecule and convert into citrates isomer
isocitrate
...
The formation of NADH and elaboration of carbon dioxide
occur at this stage
...


Assignment of General Biochemistry | Fatima khan

Reaction: 5 Conversion of alpha-Ketoglutarate
to Succinyl CoA:
In this reaction, the enzyme “alpha-ketoglutarate dehydrogenase” convert through
oxidative decarboxylation
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In this
enzyme is dependent on NAD+, FAD and CoA
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This reaction is coupled with the phosphorylation of GDP to GTP this is a
substrate level phosphorylation
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Reaction: 7 Conversion of Succinate to
Fumarate:
This reaction is the dehydration reaction that converts succinate to fumarate by the help
of enzyme “succinate dehydrogenase”
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Reaction: 8 Formation of Malate:
In this reaction, the enzyme “fumarase” converts fumarate into malate with the
addition of water
...
The third and last synthesis of NADH occurs at this stage
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Assignment of General Biochemistry | Fatima khan

Krebs cycle

Assignment of General Biochemistry | Fatima khan

The Krebs cycle turns twice for each original glucose molecule

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