Respiration 5.7 Flashcards
What is the need for cellular respiration?
To make ATP to drive biological processes such as :
- active transport
- exocytosis
- DNA replication
- cell division
- movement
What is respiration?
The process that occurs in living cells which releases the energy stored in organic molecules to synthesise ATP molecules from ADP + Pi
What is energy?
The capacity to do work
What are the components of the mitochondria?
- outer membrane
- inner membrane
- inter membrane space
- matrix
- cristae
- mitochondrial DNA
(stalked paticles - ATP synthase)
What are features of the matrix?
- contain enzymes that catalyse rections in the Krebs cycle
- contains motochondrial DNA
- contains mitochondrial ribosomes
What are features of the outer membrane?
- contains proteins (carrier/ channel)
- similar structure to plasma membrane
What are the features of the inner membrane?
- different lipid composition to outer membrane
- less permeable to small ions
- large SA due to the folds/ cristae
- contains elecron carriers and ATP synthase
What are the stages or respiration?
- glycolysis
- link reaction
- Krebs cycle
- oxidative phosphorylation
Where does glycolysis happen?
In the cell cytoplasm
What is glycolysis?
An anaerobic reaction that converts glucose to pyruvate
What happens during the process of glycolysis?
- glucose (6C) is phosphorylated to become hexose bisphosphate (6C) by hydrolysing two molecules of ATP
- hexose bisphosphate is then split into 2 molecules of triose phosphate (3C)
- the triose phosphates are then oxidated into two molecules of pyruvate (3C) by reducing NAD into NADH and making 4 molecules of ATP
What are the net products of glycolysis?
- 2 ATP (2 were used to kickstart the process)
- 2 NADH
- 2 pyruvate
Where does the link reaction occur?
Mitochondrial matrix
What is the link reaction?
the reaction where pyruvate undergoes oxidative decarboxylation to become Acetyl Coenzyme A
What happens during the process of the link reaction?
- the 2 molecules of pyruvate (3C) are decarboxylated so the carboxyl groups are removed
- it is also dehydrogenated (oxidated) to produce an acetyl group whilst reducing NAD to NADH
- the acetyle group combines with Coenzyme A to produce Acetyl Coemzyme A (2C)
What are the net products of the link reaction from 2 molecules of pyruvate?
- 2 CO2
- 2 NADH
Where does the Kerbs cycle happen?
Mitochondrial matrix
What is the Krebs cycle?
A series of reactions that oxidise acetate to 2 molecules of CO2
What happens during the process of the Krebs cycle?
- the acetyl group (2C) is released from acetyl CoA
- it combines with oxaloacetate (4C) to form citrate (6C)
- citrate is decarboxylted and dehydrogenated, producing a 5C compound, CO2 and NADH
- 5 C compound is decarboxylated and dehydrogenated, producing a 4C compound, CO2 and NADH
- substrate level phosphorylation occurs producing 1 ATP and the 4C compound remains as a 4C compound
- 4C compound is dehydrogenated, producing a different 4C compound and FADH
- 4C compound is dehudrogenated, producing NADH and regenerating oxaloacetate (4C)
How many times does the Krebs cycle happen per molecule of glucose?
The krebs cycle happens 2 times per 1 molecule of glucose
What are the products of the Krebs cycle?
- 6 NADH
- 2 FADH
- 4 CO2
- 2 ATP
Will the Krebs cycle or the link reaction happen in the absence of oxygen?
No, they are aerobic processes
How are fatty acids respired aerobically?
They are broken down into acetate which then enter the Krebs cycle via acetyl CoA
How is glycerol respired aerobically?
It is broken down into pyruvate which enters the Krebs cycle via the link reaction
How are amino acids respired aerobically?
They are deaminated and the rest of the molecule can enter the Krebs cycle directly or be changed to pyruvate or caetyle CoA
Where does oxidative phosphorylation happen?
On the inner mitochondrial membrane/ the cristae
What is oxidative phosphorylation?
The formation of ATP using energy released in the electron transport chain in the presence of oxygen
When does chemiosmosis occur?
Oxidative phosphorylation and photophosphorylation
What is chemiosmosis?
When energy from the ETC is used to pump protons across a membrane forming an elecrochemical gradient and the protons flow down their electrochemical gradient across a membrane, through ATP synthase
What happens during the process of oxidative phosphorylation?
- NADH and FADH are reoxidised when they donate their hydrogen atoms to the electron transport chain (ETC)
- the hydrogen atoms split into H+ ions and e-
- the electrons are passed down the chain of electron carriers
- as the e- are passed down some of their energy is used to pump protons across the inner membrane into the inter membrane space
- protons accumulate in the space and create an electrochemical gradient
- the gradient generates a chemiosmotic potential known as the proton motive force (pmf) and ATP is made using this energy
- protons diffuse down their concentration gradient through the ATP synthase enzymes
- the flow of protons causes the ATP synthase to allow ADP + Pi to combine to form ATP
- O2 is the final e- acceptor and it combines with electrons from the ETC and protons, forming water
How are electrons passed down the electrn transport chain?
- each e- carrier has an iron ion core which become reduced into Fe2+
- Fe2+ can then donate their e- to the Fe ion in the next electron carrier, becoming reoxidised to Fe3+
What are the products of oxidative phosphorylation?
- 28 ATP
- 28 water
- 10 NAD
- 2 FAD
What is the importance of coenzymes in cellular respiration?
They are required to transport protons, electrons and functional groups between the stages of respiration
What are the benifits to being able to respire anaerobically?
It lets organisms live in places where there is little or no oxygen
What happens if oxgen is absent during respiration?
Anaerobic respiration occurs
Where does anaerobic respiration happen in eukaryotes?
Cytoplasm
What is the process of ethanol fermentation?
- pyruvate is decarboxylated by pyruvate decarboxylase to produce ethanal and CO2
- ethanal is reduced to ethanol by ethanol dehydrogenase and by accepting hydrogen atoms from NADH
- this reoxidises NAD so it is ready to accept more hydrogen from triose phosphate
What are the products of ethanol fermentation per molecule of pyruvate?
- CO2
- ethanol
- NAD
What is the process of lactate fermentation?
- pyruvate is reduced to lactate by lactate dehydrogenase by accepting 2 hydrogen atoms from NADH
- This reoxidises NAD so it can now accept more hydrogen atoms from triose phosphate
What are the products of lactate fermentation?
- lactate
- 2 NAD
What happens to the lactate produced in anaerobi respiration?
- it is carried away from the muscles in the blood to the liver
- when more oxygen is present it either is converted to pyruvate or recycled to glucose and glycogen
Explain the ATP yield for anaerobic respiration
- neither fermentation produces any ATP
- they allow for glycolysis to continue with a net gain of 2 ATP per molecule of glucose
- glucose is partly broken down so more moleculs undergo glycolysis per minute so overall yield of YTP is quite large
- for each molecule of glucose the ATP yeild is 1/15of that produced in aerobic respiration
What is a facultive anaerobe?
An organism that will respire aerobically in the presence of oxygen but can respire anaerobically in the absence of oxygen
What is a respiratory substrate?
An organic substance that can be oxidised by respiration, releasing energy to make ATP
How do carbohydrates have to be adapted for respiration?
- disaccharides digested to monosaccharides
- other monosaccharides are changed by isomerase enxymes to glucose
How are lipids (glycogen) converted to be used in respiration?
- triglycerides are hydrolysed by lipase into glycerol and fatty acids
- glycerol is converted into tiose phosphate and then respired
How are lipids (fatty acids) converted to be used in respiration?
- they are combined with coenzyme A
- the complex is transported to the mitochondrial martix
- it is broken down into 2C acetyle groups attached to CoA
- beta oxidation generates NADH and FADH
- acetyle groups are released from CoA and enter the krebs cycle
What are the products of using fatty acids as a substrate per acetyle group oxidised in the krebs cycle?
- 3 NADH
- 1 FADH
- 1 ATP
How are proteins converted to be used in respiration?
- amino acids are deaminated in the liver to form a keto acid
- it can then enter the respiratory pathway as pyruvate, acetyle CoA or a krebs cycle acid (oxaloacetic acid)
Place the respiratory substrates in order from largest energy value per gram to smallest
- lipids
- carbohydrates
- protein
Why do lipids have the highest mean energy value (kJ/G)
They have more hydrogen atoms due to fatty acid tails so there are more protons for chemiosmosis and more ATP can be produced
(more oxygen needed for the respiration as it needs to bind to the H+ to form water)
What is the respiratory quotient equation?
RQ= CO2 produced / O2 consumed (ratio so no units)
What does it mean if RQ value is greater than 1?
Anaerobic respiration is taking place (more CO2 is being produced than O2 being consumed)
