Cellular respiration

Cellular Respirationfor Dummies

Step 1.

(Is the process in which sugars are broken down to form 2 pyruvates and 2 NADH)

Glycolyses (Breaking/splitting of sugars)

Glyco – Glucose Lyses – to break

- Occurs in the cytoplasm, 2 ATP needed/invested in this step to form 4 ATP.

- These are made through substrate level phosphorylation. This means that a substrate with 1 phosphate and an ADP (Adenosine Di Phosphate) with 2 phosphates are connected to an enzyme.

- The substrate then hands over its phosphate to the ADP to form a new phosphate group ATP (Adenosine tri phosphate) which has 3 phosphates.

- Also 2 NAD+ each gaining hydrogen (electron) during this process, making 2 NADH

- So what happened was a 6 carbon sugar (glucose) was split into two 3 carbon pyruvates (pyruvic acid)

-Produced a net of 2 ATP through substrate level phosphorylation

- 2 NADH were made


Step 2.

Oxidisation of the Pyruvates (2) - Pyruvates enter the mitochondrion where it loses an electron

- Both pyruvates then release Carbon Dioxide (CO2) and undergo major transformation into Acetyl groups

- Acetyl groups are attracted (loves) the co-enzyme “A”. They get together to form Acetyl Coenzyme-A (Acetyl Co-A)

- Acetyl Co-A now have only 2 carbons as they dropped one in the form of CO2 and produced 2 NADH (1 per pyruvate)

-So what happened was 2 pyruvates dropped a carbon molecule in the form of CO2 transforming them into Acetyl which then bonded with the co-enzyme “A” making 2 Acetyl Co-A.

-2 NADH were also produced


Step 3.

The Citric Acid Cycle (Krebs Cycle) - Occurs in the inner matrix of the mitochondrion

- This cycle input is: 1 ATP, 3 NADH, 1 FADH2 and 2CO2 - Output (input x2): 2 ATP, 6 NADH, 2 FADH2 and 4 CO2

-The Krebs cycle occurs twice and doubles the input of molecules

- At the beginning of the Krebs cycle we start with 1 ATP, 3 NADH, 1 FADH2 and 2 CO2s

- We end up with 2 ATP, 6NADH, 2 FADH2 and 4 CO2


Review so far

-We started with a simple sugar (glucose): C6 H12 O6

So what happened to all of our elements?

- in oxidation of pyruvate : 2 CO2’s were produced + - in Citric Acid (Krebs) Cycle : 4 CO2’s were produced

Total : 6 CO2

And what happened to our 12 hydrogen?

- Glycolyses : 2 NADH- Oxidization of pyruvate : 2 NADH- Citric Acid (Krebs) Cycle : 6 NADH

: 2 FADH2 Total : H12

Note: only a net of 4 ATP have been Produced so far


Step 4.

The Electron Transport Chain (ETC) - Occurs in a chain of proteins along the cristae (inner matrix membrane) of the mitochondrion

- Here proteins that make up the ETC pass along electrons causing the NADH and FADH2’s to alternate between oxidisation and reduction

- The passing of electrons continues until the last protein in the chain hands off remaining electrons to Oxygen (02), the final acceptor

- all the while and the main process of the ETC is to pump hydrogen/positive ions against the concentration gradient into the inner membrane

- However the positively charged ions need to find a way to get into the inner matrix and ATP synthase allows them to rush in by creating a gap in the ETC. This process is called chemiosmosis and is the main stage in the production of ATP.


Summing Up. What has Cellular Respiration achieved?

Science

Cellular respiration