Metabolism
1, Introduction:
History:
Glycolytic enzymes were the first enzymes to be discovered. And in 1860,
Pasteur proved that fermentation requires living cells. Then, as a response to
this, in 1897, Eduard Buchner proved that fermentation can also happen with
yeast extract, saying that you don’t need the whole
cell, but only certain parts.
Finally, in 1909 to 1942, the first glycolytic enzymes
were identified and purified.
Glycolysis:
Fats will be broken down into fatty acids and glycerol,
proteins will be broken down into amino acids, and
polysacchrides will be broken down into glucose and
other sugars. All have their own specific break down
pathway.
Glucose is our favorite fuel to turn into ATP.
The overall reaction of glycolysis is; 1 glucose (C6) —
> 2 pyruvate (C3). This one is called the; Embden-
Meyerhof-Parnas pathway.
It consists of three stages. And in stage 2, two
products are formed; dihydroxyacetone phosphate
and glyceraldehyde 3-phosphate. These are
interchangeable.
During glycolysis, also NADH is formed, this is an
electron carrier. It is formed with;
1 NAD+ + 1 H+ + 2 e- —> 1 NADH.
So it carries two electrons.
The fate of the pyruvate; (sounds like a good
movie)
It all depends on whether there is an external electrons acceptor. If yes, it does
respiration and the pyruvate is turned into acetyl-CoA. If no, it does
fermentation and the pyruvate gets turned into either lactate or ethanol. In
fermentation, the NADH donates its electron to the pyruvate, turning it.
Glycolytic pathways are used for cancer treatments, because glycolysis and
cancer are tightly intertwined. Shutting down this pathway, would certainly kill
the tumor. But since every other cells also uses this pathway, healthy cells
would die as well.
Gibbs energy (∆G0’):
A reaction only happens when the Gibbs free energy is negative.
Gibbs energy is the driving force of all biological processes. It balances energy
and entropy;
Entropy is the probability to which the energy will move, for example from
high concentration to low concentration.
,Energy is the electrical force, the repulsion and the rejection of the charges.
To make ATP, you need 4 driving forces to start the reaction;
1. The negative charges on the phosphate repel each other.
2. Resonance structures stabilize the inorganic phosphate that forms after
separation.
And in the case of hydrolysis (breaking down
water);
3. Two molecules are formed from one.
4. The ADP and inorganic phosphate are
stabilized by the bound water molecules.
Enzymes couple the uphill and down hill
reactions. And kinases are enzymes who drive
the glycolysis in the forward direction. If this were not the case, only the down
hill reactions would take place. Because down hill reactions happen
spontaneous.
ATP is a good carrier for Gibbs free energy, because;
- ATP hydrolysis has a strong driving force, hence ATP is capable of driving
uphill reactions.
- There are reactions with even more negative ∆G0’, these are required to
recharge the carrier.
- ATP is stable in absence of enzymes.
The ∆G0’ is additive, meaning you
can stack them. For example the
first step of glycolysis;
Enzyme kinetics:
The michealis-menten equation explains the
relationship between the substrate S and the
enzyme E. Because as we all know, enzymes lower
the activation energy and accelerate the reaction. It
goes like this;
E + S ⇌ ES ⇌ E + P
All enzyme reaction follow a certain curve line;
Km is where the concentration of the substrate is at
half of the maximum velocity. If the [S] >> Km, then
the V=Vmax.
Competitive inhibitor I can inhibit the enzyme by taking the place
of the substrate.
, Vmax= same, Km= goes up.
Noncompetitive inhibitor binds to the enzyme on a place
that doesn’t inhibit the binding of the substrate.
Vmax= goes down, Km= same
Draw to the right how you can see the 1/Vmax and 1/Km;
1, Introduction:
History:
Glycolytic enzymes were the first enzymes to be discovered. And in 1860,
Pasteur proved that fermentation requires living cells. Then, as a response to
this, in 1897, Eduard Buchner proved that fermentation can also happen with
yeast extract, saying that you don’t need the whole
cell, but only certain parts.
Finally, in 1909 to 1942, the first glycolytic enzymes
were identified and purified.
Glycolysis:
Fats will be broken down into fatty acids and glycerol,
proteins will be broken down into amino acids, and
polysacchrides will be broken down into glucose and
other sugars. All have their own specific break down
pathway.
Glucose is our favorite fuel to turn into ATP.
The overall reaction of glycolysis is; 1 glucose (C6) —
> 2 pyruvate (C3). This one is called the; Embden-
Meyerhof-Parnas pathway.
It consists of three stages. And in stage 2, two
products are formed; dihydroxyacetone phosphate
and glyceraldehyde 3-phosphate. These are
interchangeable.
During glycolysis, also NADH is formed, this is an
electron carrier. It is formed with;
1 NAD+ + 1 H+ + 2 e- —> 1 NADH.
So it carries two electrons.
The fate of the pyruvate; (sounds like a good
movie)
It all depends on whether there is an external electrons acceptor. If yes, it does
respiration and the pyruvate is turned into acetyl-CoA. If no, it does
fermentation and the pyruvate gets turned into either lactate or ethanol. In
fermentation, the NADH donates its electron to the pyruvate, turning it.
Glycolytic pathways are used for cancer treatments, because glycolysis and
cancer are tightly intertwined. Shutting down this pathway, would certainly kill
the tumor. But since every other cells also uses this pathway, healthy cells
would die as well.
Gibbs energy (∆G0’):
A reaction only happens when the Gibbs free energy is negative.
Gibbs energy is the driving force of all biological processes. It balances energy
and entropy;
Entropy is the probability to which the energy will move, for example from
high concentration to low concentration.
,Energy is the electrical force, the repulsion and the rejection of the charges.
To make ATP, you need 4 driving forces to start the reaction;
1. The negative charges on the phosphate repel each other.
2. Resonance structures stabilize the inorganic phosphate that forms after
separation.
And in the case of hydrolysis (breaking down
water);
3. Two molecules are formed from one.
4. The ADP and inorganic phosphate are
stabilized by the bound water molecules.
Enzymes couple the uphill and down hill
reactions. And kinases are enzymes who drive
the glycolysis in the forward direction. If this were not the case, only the down
hill reactions would take place. Because down hill reactions happen
spontaneous.
ATP is a good carrier for Gibbs free energy, because;
- ATP hydrolysis has a strong driving force, hence ATP is capable of driving
uphill reactions.
- There are reactions with even more negative ∆G0’, these are required to
recharge the carrier.
- ATP is stable in absence of enzymes.
The ∆G0’ is additive, meaning you
can stack them. For example the
first step of glycolysis;
Enzyme kinetics:
The michealis-menten equation explains the
relationship between the substrate S and the
enzyme E. Because as we all know, enzymes lower
the activation energy and accelerate the reaction. It
goes like this;
E + S ⇌ ES ⇌ E + P
All enzyme reaction follow a certain curve line;
Km is where the concentration of the substrate is at
half of the maximum velocity. If the [S] >> Km, then
the V=Vmax.
Competitive inhibitor I can inhibit the enzyme by taking the place
of the substrate.
, Vmax= same, Km= goes up.
Noncompetitive inhibitor binds to the enzyme on a place
that doesn’t inhibit the binding of the substrate.
Vmax= goes down, Km= same
Draw to the right how you can see the 1/Vmax and 1/Km;
