(5.7) Respiration Flashcards
What are the 4 stages of respiration?
- glycolysis
- the link reaction
- the krebs cycle
- oxidative phosphorylation
What is essentially happening during respiration?
Glucose is being burnt through chemical reactions (with oxygen) to produce carbon dioxide, water and energy in the form of ATP
Where does glycolysis take place?
In the cytoplasm
What happens during glycolysis?
Glucose (6 carbon molecule) is converted into 2 pyruvates (3 carbon molecule)
Describe the steps of glycolysis
- glucose is phosphorylated (from 2 ATP molecules) creating hexose phosphate
- because the hexose phosphate is unstable, this is immediately broken down into 2 triose phosphate molecules
- hydrogen is removed from 2 triose phosphate to create 2 pyruvate molecules
- this means triose phosphate has been oxidised
What happens to the hydrogen removed from the hexose phosphate molecule in glycolysis?
It is transferred to the coenzyme NAD to create reduced NAD (NADH)
What happens to the NADH created in glycolysis?
It is then used in oxidative phosphorylation
What is the ATP production in glycolysis?
- the conversion of triose phosphate to pyruvate produces 4 molecules of ATP
- 2 ATP molecules are used for the phosphorylation of glucose
- There is a net gain of 2 ATP molecules
Define Phosphorylation
Adding a phosphate group to a molecule
Where does the link reaction take place?
In the mitochondrial matrix
What happens during the link reaction?
Converts pyruvate into acetyl coenzyme a
How much ATP is produced during the link reaction?
There is no ATP created however NADH is produced for oxidative phosphorylation and coenzyme a for the krebs cycle
Describe the steps of the link reaction
- a carbon atom is removed from pyruvate forming carbon dioxide
- this removal of carbon from pyruvate creates acetate (2 carbon molecule)
- when making pyruvate into acetate, hydrogen is removed creating more NADH
- the acetate joins with co-enzyme A to form acetyl co-enzyme A
What happens during the Krebs cycle?
A series of reactions used to generate NADH and FADH needed for oxidative phosphorylation
Describe the steps of the Krebs cycle
- acetyl CoA reacts with oxaloacetate
- CoA is removed from acetyl CoA and returned to the link reaction to be reused
- Citrate is produced (6 carbon molecule)
- Carbon dioxide and hydrogen are removed from citrate creating more CO2 and NADH and citrate becomes a 5 carbon molecule
- decarboxylation and dehydrogenation occurs again which converts the 5 carbon compound into a 4 carbon compound called oxaloacetate
- ATP, 2 molecules of NADH,1 molecule of FAD and 1 CO2 molecule
How many times does the krebs cycle take place for each aerobically respired glucose molecule?
twice
Where does oxidative phosphorylation take place?
The mitochondrial matrix
Describe the steps of oxidative phosphorylation
- NADH and FADH release H atoms which split into H ions and electrons
- electrons passed onto electron carries (embedded in the inner-mitochondrial membrane)
- series of these creates an electron transport chain
- energy is lost as travel between electron carriers
- lost energy is used to pump hydrogen ions from the mitochondrial matrix across the inner membrane
- H ions accumulate in the intermembrane space and generates a proton gradient
- H ions flow back into the matrix through enzyme ATP synthase
- the movement of the of H ions is used to add a phosphate group onto ADP and form ATP (proton movement force)
- once the electrons reach the end of the transport chain passed onto oxygen (final electron acceptor)
- oxygen form with electrons and hydrogen ions to form water
What is the final electron acceptor is oxidative phosphorylation?
Oxygen
What reactions take place in the mitochondrial matrix?
The Link reaction and Krebs cycle
What does the mitochondrial matrix contain?
- enzymes that catalyse the link reaction and krebbs cycle
- NAD and FAD
- oxaloacetate which accepts the acetyl group during the link reaction
- mitochondrial DNA which codes for enzymes and other proteins
- mitochondrial ribosomes - where mitochondrial proteins are assembled
