Topic 5: Respiration Flashcards
What are autotrophic organisms?
Organisms that make their own food
What are heterotrophic organisms?
Organisms which eat and digest other organisms to get food and energy from cellular respiration
What is cellular respiration?
The process by which energy is transferred from the chemical bonds in respiratory substrates to form ATP
What is aerobic respiration?
Respiration in the presence of oxygen
What is ATP?
Adenosine triphosphate
Give some characteristics of ATP
Energy currency
Universal
Name and give the reaction which forms ATP
Phosphorylation
ADP + Pi —-> ATP + H2O
Describe the structure of ATP
A DNA molecule with two extra phosphate groups
What enzyme breaks down ATP?
ATPase
Is the formation of ATP exothermic or endothermic?
Exothermic
Name all the stages of aerobic respiration
Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation
Where does glycolysis take place?
Cytoplasm
Where does the glucose for glycolysis come from?
From the blood
Form the breakdown of glucagon in the muscles and liver
Summarise the stages of glycolysis
Glucose is phosphorylated
Phosphorylated carbon is broken down into two molecules of G3P
G3P oxidised to pyruvate
How is glucose phosphorylated in glycolysis?
Two phosphate groups are added to the glucose using two ATP molecules
Why do you need to phosphorylate glucose in glycolysis?
It raises its energy level so its more reactive
Makes it unable to pass through the cell membrane
How is G3P converted into pyruvate?
Loses a hydrogen atom which is picked up by a molecule of NAD which is reduced to NADH.
How many ATP molecules are made for every molecule of G3P that’s oxidised?
2
What is the net number of ATP molecules produced in glycolysis
2
What determines what happens to pyruvate once it’s been formed?
Whether there is enough oxygen or not
If there is not enough oxygen present in an animal, what happens to pyruvate?
Pyruvate is reduced to lactate (lactic acid)
NADH —> NAD
Why is the regeneration of NAD important?
To carry on glycolysis in aerobic respiration
If there isn’t enough oxygen present in plants, what happens to pyruvate?
Pyruvate is decarboxylated to ethanal and then reduced to ethanol
What does the breakdown of pyruvate anaerobically in plants produce?
Ethanol and carbon dioxide
Why is the fermentation of glucose irreversible in plants?
Because the carbon dioxide dissipates/diffuses
What is the link reaction?
The reaction which links glycolysis to the Krebs cycle
Summarise the link reaction
Pyruvate is decarboxylated to acetate which joins to coenzyme A to form acetyl coenzyme A
What does NAD do in the link reaction?
It becomes NADH because the pyruvate is dehydrogenated
In the presence of oxygen, where does pyruvate go?
It’s transported across the inner and outer mitochondrial membrane into the matrix by active transport
Where does the link reaction take place?
Matrix of the mitochondria
Where does the Krebs cycle take place?
In the mitochondrial matrix?
What is the purpose of the Krebs cycle?
To make the NADH and FADH needed in the electron transport chain
Summarise the Krebs cycle
Acetate + oxaloacetate –> 6C
6C decarboxylated to 5C: CO2 and NADH formed
5C decarboxylated to 4C: CO2 and NADH formed
4C to another 4C: ATP
4C to another 4C: FADH
4C to oxaloacetate: NADH
For every glucose molecule, how many times does the Krebs cycle go around?
Twice
Summarise the products of the Krebs cycle
3 NADH
1 FADH
2 CO2
1 ATP
Where does oxidative phosphorylation take place?
Inner mitochondrial matrix
Summarise the events of oxidative phosphorylation
NADH and FADH are oxidised so they lose a H
H —> H+ + e-
Electrons passed down chain and release energy
H+ is pumped through proteins into inter-membrane space with energy
H+ ions flood into the matrix through ATP synthase, forming ATP
Electrons passed onto oxygen to combine with 2 H+ molecules to form water
What does oxidative phosphorylation mean?
The formation of ATP using energy from oxidation in the electron transport chain
Give another term for water in the ETC
The terminal electron acceptor
