2.5 CELLULAR RESPIRATION

A molecule is said to be oxidized if:
(i)   it receives oxygen.
(ii)  it losses hydrogen.
(iii) its oxidation number is increased.

 
A molecule is said to be reduced if:
(i)   it losses oxygen.
(ii)  it receives hydrogen.
(iii) its oxidation number is reduced.


There are 3 types of cellular respiration, which are:
(i)   Aerobic respiration
(ii)  Anaerobic respiration
(iii) Fermentation

A.  AEROBIC RESPIRATION

Overall process of cellular respiration

A labelled diagram of mitochondrion

Substrate-level phosphorylation

3 stages:

(i)  Glycolysis 
     - Glycolysis = sugar splitting
     - Sugar = glucose  

     - has 10 steps
     - has 2 phases which are ENERGY 

       INVESTMENT PHASE and ENERGY  

       PAYOFF PHASE

     - occurs in the cytosol of cell

     - can occur WITHOUT oxygen
     - produces NADH (nicotinamide adenine  

       dinucleotide) which is a type of coenzyme, 

       can be derived from vitamin niacin.

     - produces ATP from substrate-level 

       phosphorylation.
     - Net yield: 2 ATP and 2 NADH

(i) Glycolysis (phase 1)

(i)  Glycolysis (phase 2) 

(ii) Pyruvate oxidation/Link reaction  and Krebs cycle/ citric acid cycle/ tricarboxylic acid cycle
    - Named Krebs cycle honoring Hans Krebs, a   
      German-British scientist
    - have 3 steps + 8 steps
    - occurs in the matrix of mitochondria 

 

(ii) (a) Pyruvate oxidation

(ii) (b)  Krebs cycle/citric acid cycle/ 

tricarboxylic acid cycle

(iii)  Oxidative phosphorylation  
(electron transport chain and chemiosmosis) 
   - occurs in the inner membrane of mitochondria

 

 (iii) Oxidative phosphorylation (electron transport chain and chemiosmosis)

B.   ANAEROBIC RESPIRATION

- Generate ATP without using oxygen.

- Example in certain prokaryotic organisms which live in environments without oxygen.

- Have electron transport chain but the final electron acceptor at the end of the chain is not oxygen.

C.  FERMENTATION

-  do not use oxygen.

 - do not use electron transport chain as in aerobic respiration and anaerobic respiration.