respiration

How many stages of respiration are there and what are they called?

1. glycolysis

2. link reaction

3. krebs cycle

4. oxidative phosphorylation

define aerobic respiration

describe the structure and adaptations of the mitochondria.

describe the process of glycolysis (1st stage of respiration)

• glucose is phosphorylated by 2 phosphates from 2 ATP hydrolysis to form 1 molecule of glucose phosphate

• this is highly reactive so split into 2 molecules of triose phosphate

• triose phosphates are oxidised to form 2 molecules of pyruvate- NAD collects the H+ ions and forms 2 reduced NAD (NADH)

• net gain of 2 ATP, 2 NADH, 2 pyruvate

where does glycolysis occur?

In the cell cytoplasm

Where does the link reaction occur?

Mitochondrial matrix

Where does the Krebs cycle occur?

In the mitochondrial matrix

Where does oxidative phosphorylation occur?

In the mitochondrial inner membrane- cristae

What are the 2 types of anaerobic respiration and where do they occur?

• alcohol fermentation occurs in plants and yeast

• lactate fermentation occurs in animal cells & some bacteria

Describe the process of alcohol fermentation in plants and yeast

• pyruvate is converted into ethanal - CO2 released as a waste product

• then ethanal converted into ethanol - NADH is converted to NAD

Describe the process of lactate fermentation in animals and some bacteria

• pyruvate is converted into lactate (lactic acid) - NADH is converted into NAD

Describe and explain the link reaction

1. pyruvate is oxidised to form acetate

2. So NADH picks up H and becomes reduced NAD (NADH), CO2 is released as a waster product

3. coenzyme A combines with acetate to form acetylcoenzymeA

Describe and explain the Krebs cycle

1. acetylcoenzyme A (2C) from link reaction combines with oxaloacetate (4C) to form citrate (6C) and release coenzyme A back to the link reaction to be reused

2. 6C molecule is decarboxylated and dehydrogenated to remove CO2 as a waste product and NAD forms NADH

3. 5C then converted to a 4C molecule- oxaloacetate is reformed to be used again in Krebs cycle

   • by decarboxylated n and dehydrogenation occurring, producing 1 molecule of reduced FAD (FADH2) and 2 molecules of NADH

   • ATP is produced by direct transfer of phosphate group to ADP

describe the process of oxidative phosphorylation

• The reduced NAD and reduced FAD give up electrons and Ht ions at the start of the electron transport chain, and they are oxidised

• The electrons move down the ETC in a series of redox reactions

• This releases energy which allows H+ to be pumped / actively transported from the matrix to the intermembrane space

• The Ht diffuse back into the matrix through ATP synthase down their electrochemical gradient

• This allows ADP + Pi to react to form ATP

• The electrons and hydrogen ions are picked up by oxygen which is the terminal electron and hydrogen ion acceptor forming water