Respiration Flashcards
What are the 4 stages of aerobic respiration?
1) Glycolysis
2) Link reaction
3) Krebs cycle
4) Oxidative phosphorylation
Where does glycolysis occur?
In the cytoplasm
What are the 3 steps of glycolysis?
1) Phosphorylation of glucose - glucose phosphate using ATP
2) Production of TP
3) Oxidation of TP into pyruvate with gain of ATP + NADH
Describe phosphorylation of glucose
- 2 ATP are hydrolyzed to ADP and each releases a phosphate which attach at each end of the 6C glucose
- Glucose phosphate produced = very high energy
Describe production of TP
- Since glucose phosphate is very high energy and highly reactive it will split into 2 3C TP
Describe production of pyruvate
- Both TP will be oxidized
- The coenzyme NAD picks up a H from the TP = NAD is now reduced to NADH = TP oxidized
- This forms 2 pyruvate
- 2 ATP produced per pyruvate
Why is there a net gain of only 2 ATP when 4 are produced?
- Since we use 2 ATP at the start of glycolysis
- 4 are produced but overall the net gain will be 2 excluding the 2 ATP used
What are the products of glycolysis and what happens to them?
- 2 Pyruvate
- 2 NADH
- 2 net gain ATP
The pyruvate and NADH are actively transported to the mitochondrial matrix
Where does the link reaction take place?
In the mitochondrial matrix
Describe the link reaction
- Pyruvate is oxidized into a 2C acetate
- The H that is released during oxidation is picked up by coenzyme NAD - NADH
- 1C is released as CO2
- Acetate is then converted into 2C acetylcoenzyme A
- Acetate + Coenzyme A = Acetylcoenzyme A
What are the products of the link reaction for a glucose molecule?
- 2 Acetyl CoA
- 2 NADH
- 2 CO2
Where does the krebs cycle take place?
In the mitochondrial matrix
Describe the krebs cycle
- Acetyl CoA reacts with a 4C releasing CoA back to be recycled = 6C which enters cycle
- Decarboxylation to remove 2C as CO2
- Substrate level phosphorylation will form ATP from ADP + Pi
- A series of redox reactions that reduce 3 NAD and 1 FAD -> NADH + FADH
What are the products of the krebs cycle per cycle?
- 3 NADH
- 1 FADH
- 1 ATP
- 2 CO2
Where does oxidative phosphorylation take place?
In the mitochondrial cristae
Describe oxidative phosphorylation
- NADH + FADH carry the H to the cristae
- The H will split into H+ and e-
- e- move down the ETC through the embedded proteins in the cristae
- As it moves from protein-protein it releases energy
- The H+ is pumped across from matrix to intermembrane space using the energy
- Results in an electrochemical gradient in the IMS
- Go down the concentration gradient via ATP synthase via facilitated diffusion
- Diffusion causes the catalysis and phosphorylation of ADP + Pi = ATP
- Oxygen is the final electron acceptor in the chain
- The O2 in the matrix will pick up e- from the of ETC + H+ that have come back via ATP synthase = H2O
- 1/2(O2) + (2H+)+ 2e- → H2O
Why is aerobic respiration only 32% efficient?
- Proton leaks across mitochondrial membrane during oxidative phosphorylation
- ATP used to transport pyruvate and NADH to matrix
- Energy lost as heat
What is anaerobic respiration?
-Respiration in the absence of oxygen
- Takes place only in the cytoplasm
Describe anaerobic respiration for animals
- Incomplete breakdown of glucose
- Pyruvate is produced at the end of glycolysis and a net gain of 2 ATP
- Pyruvate is reduced by gaining a H+ from NADH which is oxidized to NAD
- Lactate is produced + H2O = Lactic acid which will denature enzymes = muscle fatigue = therefore anaerobic short term
- NAD can be reused in glycolysis and it can keep happening in absence of O2
What happens to the lactate produced in anaerobic respiration
- Transported to liver via bloodstream
- Converted into pyruvate
- Can enter the link reaction in liver cells
Describe anaerobic respiration for plants and microorganisms
- Incomplete breakdown of glucose
- Pyruvate is produced at the end of glycolysis and a net gain of 2 ATP
- Pyruvate is reduced by gaining a H+ from NADH which is oxidized to NAD
- Ethanol and CO2 is produced
- Ethanol = toxic = denature enzymes = only short term
- NAD can be reused in glycolysis and it can keep happening in absence of O2
Compare the efficiency between both respirations
AEROBIC:
- Total yield from 1 glucose molecule is 38 ATP
- More efficient
ANAEROBIC:
- Total yield from 1 glucose molecule is 2 ATP
- Less efficient
How do you investigate a variables effect on rate of respiration?
- Use a respirometer
- As the pressure changes in test tube as oxygen is taken in and CO2 is absorbed by NaOH
- Set a timer and see how far the colored liquid moves in a set period of time
- The volume decreases = pressure decreases
- Pressure is higher in the control tube = liquid moves towards experimental tube
How do you calculate rate of respiration?
Volume of O2 consumed or CO2 produced/ time * mass of sample
- Volume = π r2 * distance moved by colored liquid
Explain the benefit of the respirometer set up
AIR TIGHT:
- To prevent air entering and exiting which would change the volume/pressure effecting the movement of colored liquid
USE OF NaOH:
- Absorbs the CO2 so there is a net decrease in pressure as O2 is consumed and so we can measure the O2 consumed
What is the unit for respiration?
Unit volume per time per mass
What are some alternative respiratory substrates?
- Proteins: Amino acids
- Lipids: Fatty acid + glycerol
How can lipids be used as an alternative?
1) Phosphorylation of glycerol = TP for glycolysis
2) Fatty acid = acetate for link reaction
3) H atoms produced for oxidative phosphorylation
How can proteins be used as an alternative?
De-amination produces:
1) 3C compounds = pyruvate for link reaction
2) 4/5C compounds = used in Krebs cycle
