Glycolysis

Glycolysis

The first stage of respiration

Glycolysis

Respiration

• Process of respiration is split into four parts

• By breaking it into four parts we will have less to learn at any one stage

Glycolysis is the first stage of respiration!


Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate



Glucose is a hexose (6-carbon) molecule




Pyruvate is a triose (3-carbon) molecule




Pyruvate is a triose (3-carbon) molecule

Pyruvate is also known as pyruvic acid

• Glycolysis takes place in the cytoplasm of cells.

• Glycolysis takes place in the cytoplasm of cells.

• It’s the first stage of both aerobic and anaerobic respiration.


•It doesn’t need oxygen to take place – so it’s anaerobic


•It doesn’t need oxygen to take place – so it’s anaerobic

There are TWO STAGES of GLYCOLYSIS – Phosphorylation and Oxidation

Glycolysis

Glycolysis

1

2

A

B

Glycolysis

1

2

A

B

These arrows in diagrams just mean that A goes into the main reaction and is

converted to B.

A will normally release or collect something from

molecule 1, e.g. hydrogen or phosphate

Stage One - Phosphorylation


1.Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate.



2.The hexose phosphate is split using water



2.The hexose phosphate is split using water (hydrolysis)



2.The hexose phosphate is split using water (hydrolysis)

3.2 molecules of triose phosphate and 2 molecules of ADP are created.

A triose phosphate is just a simple 3-carbon sugar with a phosphate group attached.

Different books use different names!

What’s the point?

• Glucose can now no longer leave the cell.

What’s the point?

• Glucose can now no longer leave the cell.

• Molecules produced are much more reactive!

Stage Two - Oxidation


1.The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate.



2. Coenzyme NAD+ collects the hydrogen ions, forming 2 reduced NAD (NADH + H+)


1. The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate.


A coenzyme is a helper molecule that carries chemical groups or ions, e.g. NAD+ removes H+ and carries it

to other molecules.




3. 4 ATP are produced, but 2 were used up at the beginning, so there’s a net gain of 2 ATP.

Next in Aerobic respiration….


1. The 2 molecules of reduced NAD go to the electron transport chain (ETC), part 4 of respiration.


1. The 2 molecules of reduced NAD go to the electron transport chain (ETC), part 4 of respiration.

2. The two pyruvate molecules go into the matrix of the mitochondria for the link reaction.

I bet your so excited you can not wait!

The Link Reaction

The Link Reaction

The second stage of respiration

You are now in the matrix of the mitochondria!

Link Reaction – 2nd stage of respiration


The Link Reaction converts Pyruvate to Acetyl Coenzyme A


The Link Reaction converts Pyruvate to Acetyl Coenzyme A

The link reaction happens when oxygen is available.



1. One carbon atom is removed from pyruvate in the form of CO2.



2. The remaining 2-carbon molecule combines with coenzyme A to produce acetyl coenzyme A (acetyl CoA).



2. The remaining 2-carbon molecule combines with coenzyme A to produce acetyl coenzyme A (acetyl CoA).

3. Another oxidation reaction happens when NAD+ collects more hydrogen ions. This forms reduced NAD (NADH + H+).


4. No ATP is produced in this reaction.


The Link reaction happens Twice for every Glucose Molecule


The Link reaction happens Twice for every Glucose Molecule

So for every glucose molecule used in glycolysis, two pyruvate and two acetyl CoA molecules are made.

So for each glucose molecule:


•Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration)





•Two carbon dioxide molecules are released as a waste product of respiration




•Two molecules of reduced NAD are formed and go into the electron transport chain (part 4 of respiration)




•Two molecules of reduced NAD are formed and go into the electron transport chain (part 4 of respiration)

Final thoughts….• Acetyl Co-what?????• It IS very confusing, but you need to know it.• Take your time and fet to grips with one stage at

a time.• Don’t worry if you can not remember all the

details straight away.• If you can remember where each stage starts

and what the products are, you’re getting there!

Technology

Glycolysis