Aerobic Respiration Flashcards
What is the first stage of aerobic respiration
Glycolysis
What is glycolysis
The process by which glucose is broken down into two molecules of pyruvate
Why does glycolysis take place
To release energy in the form of ATP, that the cells can use
Where does glycolysis take place
- in the cell cytoplasm
What are the four stages of glycolysis
1) Phosphorylation (of glucose)
2) Splitting of the hexose 1,6-bisphosphate
3) Oxidation of triose phosphate
4) Conversion of triose phosphate to pyruvate
What is the start product of glycolysis
Glucose (6C)
What is the end product of glycolysis
2 Pyruvates (3C)
Describe glycolysis
1) starts with glucose (6C)
2) Glucose is phosphorylated by ATP which leaves ADP as a product as well as Glucose-6-P
3) Glucose-6-P is unstable and breaks down to fructose-1-P
4) Fructose-1-P is phosphorylated, making Hexose 1,6-bisphosphate as well as ADP
5)Hexose 1,6-bisphosphate is also an unstable molecule so this breaks down to 2 Triose phosphate (3C) molecules
6) Triose phosphate is oxidised (looses a H) forming 2 Intermediate compound s(3C) molecules which reduces 2 ADP and 2 NAD to form 2 ATP and 2 NADH
7) The intermediate compounds (3C) is also oxidised to form 2 Pyruvate (3C) molecules which reduces another 2 ADP molecule to 2 ATP
What are the reactants in glycolysis, and how many of each molecule
- 2 ATP
- 2 NAD
- 4 ADP
- Glucose
What are the products in glycolysis, and how many of each molecule
- 4 ATP
- 2 ADP
- 2 NADH
- 2 Pyruvate
Name and describe the 3 types of ATP production
1) Photophosphorylation
- occurs in the chlorophyll during photosynthesis (requires co-enzyme NADP)
2) Oxidative phosphorylation
- occurs in the mitochondria during the electron transport chain (part of respiration requires co-enzymes NAD or FAD —> both shuttle hydrogen)
3) Substrate-level phosphorylation
- when phosphate groups are transferred from donor molecules to ADP
What is the mitochondria
The site of aerobic respiration
What are the parts of the mitochondria
1) Outer membrane
2) Inner membrane
3) Inter membrane space
4) Crista
5) Matrix
What is the role of the outer mitochondrial membrane
- a barrier that stops large molecules from entering the mitochondria (but it allows pyruvate in)
What is the role of the inner mitochondrial membrane
- a barrier which prevents many small molecules from the cytoplasm from entering (impermeable to most small ions) the matrix
- contain electron carriers and ATP synthase molecules
What is the role of the inter membrane space
- act as a temporary energy store before the energy is used to make ATP
What is the role of the matrix
- contains the enzymes of the Krebs cycle
-site of Link and Kreb reaction
What is the role of the crista
- highly folded which creates a large surface area to hold electron carriers and ATP synthase molecules
How is ATP generated in respiration
1) Substrate level phosphorylation
2) Oxidative phosphorylation ( has to have a H+ pump/ electron chain)
What is the Link reaction
The reaction where Pyruvate gets decarboxylated and dehydrogenated
Where does the Link reaction take place
- the mitochondrial matrix
Describe the Link reaction
1) Pyruvate (3C) undergoes decarboxylation and looses a CO2 molecules
2) Pyruvate also undergoes dehydrogenation and the H+ ion it looses is used to reduce NAD forming NADH
3) the decarboxylation and dehydrogenation of pyruvate forms an acetate (2C) group
4) this acetate group (2c) combines with coenzyme A (CoA) to become acetyl CoA
5) the CoA from acetyl CoA is removed forming an acetyl group which goes into the Krebs reaction
What is the Krebs cycle
- a series of enzyme-catalysed reactions that oxidise the acetyl CoA from the link reaction to two molecules of carbon dioxide whilst also conserving energy by reducing the coenzymes NAD and FAD
Where does the Krebs cycle take place
- the mitochondrial matrix
Describe the Krebs cycle
1) the acetate in the acetyl group (2C) combines with oxaloacetate (4C) forming citrate (6C)
2) this citrate (6C) is then decarboxylated and dehydrogenated, forming a 5C compound, NADH and CO2
3) this 5C compound is further decarboxylated & dehydrogenated producing a 4C compound, NADH and CO2
4) this 4C compound combines temporarily to CoA and then it is released. Substrate- level phosphorylation takes place producing ATP
5) the 4C compound is dehydrogenated producing a different 4C compound and FAD2H
6) the 4C molecule’s atoms are rearranged catalysed by an isomerase enzyme, and further dehydrogenation takes place, producing NADH
7) the 4C molecule is regenerated to oxaloacetate so the cycle can continue.
What are the reactants in the Link reaction
- Pyruvate
- NAD
- CoA
What are the products in the Link reaction
- Acetyl CoA
- NADH
- CO2
- H+
How many NADH molecules are made in the Link reaction
2
How many FADH molecules are made in the Link reaction
0
How many CO2 molecules are made in the Link reaction
2
How many ATP molecules are made in the Link reaction
0
How many NADH molecules are made in the Krebs cycle
6
How many FADH molecules are made in the Krebs cycle
2
How many CO2 molecules are made in the Krebs cycle
4
How many ATP molecules are made in the Krebs cycle
2
How many times does the Link and Krebs reaction happen, and why
Twice, as there are 2 Pyruvate molecules
What is oxidative phosphorylation
- the final stage of aerobic respiration
- it produces ATP using oxidative phosphorylation
Where does oxidative phosphorylation takes place
- on the inner membrane of the mitochondria
Describe oxidative phosphorylation
1) the dehydrogenase enzyme oxidises NADH to NAD producing an electron and H+ ions
2) these electrons move through the electron carrier chain completing a series of oxidation, reduction reactions, loosing energy at each stage
3) this lost energy is used to allow H+ to travel through the proton pump into the inter membrane space
4) this increases the H+ concentration in the inter membrane space creating a H+ concentration gradient
5) then the H+ ions move down the concentration gradient through ATP synthase
6) the H+ ions hydrolyse the formation of ATP
7) the electrons are then accepted by the final electron acceptor (O2) and reacts with 2H+ to form water ( 2H+ + 1/2 O2 —> H2O)
For every 2 hydrogen donated to the electron transport chain by NADH, How many ATP molecules are made
3
For every 2 hydrogens donated to the electron transport chain by FAD2H, How many ATP molecules are made
2
Why do cells not actually produce 38 ATP molecules
- as energy is used to:
-transport ADP & ATP into the mitochondria from the cytoplasm
-protons could “leak” across the membrane reducing the number to generate the proton motive force
-active transport of pyruvate (cytoplasm) into the mitochondria
Describe the respiratory substrates
- Glycogen/ Strach to glucose to pyruvate (glycolysis).
- Pyruvate to Acetyl coenzyme A (link reaction)
- Protein is broken to amino acid and goes into both pyruvate and acetyl coenzyme A
- Lipids are broken to fatty acids and goes into acetyl coenzyme A
- acetyl coenzyme A goes into the Krebs cycle
What is one feature that fats and proteins both have in common
They can both be respired (after being broken down to amino acids and fatty acids)
Why do fats release more energy per gram
- Because there are more hydrogen molecules per gram (twice the amount) which produced more NADH and FAD2H so more ATP can be made
What is the structure of a carbohydrate
-alpha and beta glucose
Alpha:
OH on carbon 1 on the bottom
6 carbon ring
Beta:
OH on carbon 1 on top
6 carbon ring
What is the structure of a protein
Amino group
Carboxyl group
Joined with a CHR group
What is the structure of a lipid
- Triglyceride:
Glycerol
3 fatty acids
What is the respiratory quotient
The ratio of CO2 produced to O2 consumed per unit time by an organism
What is the equation for RQ
Volume of CO2 given off
—————————————
Volume of O2 taken in
What are two features of the RQ
1) there are no units as it is a ratio
2) different substances have different RQ values
What is the RQ value of glucose
1
What is the RQ value of amino acids
0.9
What is the RQ value of fats
0.7
What is the RQ value of anaerobic respiration
> 1
What happens if a mixture of substrates is being used
Then the figure will be different from the other “known” RQ values
What could an RQ value of 0.8 be
- could be both a protein and a fat being used as multiple things are usually respired at once
What does a high RQ value usually indicate
- that anaerobic respiration is taking place. As it shows more CO2 is being produced than O2 is being consumed
Calculate the RQ value for this reaction
2C18H34O2 + 51O2 = 36CO2 + 34H2O
36CO2
———— = 0.7
51O2
How can the RQ (and oxygen uptake) be measured
Using a respirometer
How many ATP molecules in total are made from glycolysis
8
((2 ATP + 2 NADH, which equals 3 x2 (6), so 2 +6))
How many ATP molecules in total are made in the Link reaction
6
(1 NADH= 3ATP but the cycle happens twice as there is two pyruvate molecules)
How many ATP molecules in total are made in the Krebs cycle
24
( 1 ATP + 3 NADH (9 ATP) + FAD2H (2 ATP) =12, cycles happens twice so 24
How many ATP molecules do we make from 1 Glucose molecule
38 ATP (net gain)
Define the term chemiosmosis
- the generation of ATP from a proton gradient. It occurs in all living things
What is the overall equation of aerobic respiration
Glucose + Oxygen ———> Carbon dioxide + Water
C6H12O6 +6O2 ———> 6CO2 + 6H2O
