5.2: Respiration Flashcards
Give a simple description of what respiration involves
involves the oxidation of organic molecules to release energy - this energy is used to synthesis ATP from ADP + Pi
What are the two types of respiration and how do they differ
Aerobic - requires oxygen
Anaerobic - doesn’t require oxygen
What is the equation for aerobic respiration
C6H12O6 + 6O2 -> 6CO2 + 6H2O
What are the four stages of aerobic respiration and where do they each occur
1- Glycolysis - cytoplasm
2- Link reaction - mitochondrial matrix
3- Krebs cycle - mitochondrial matrix
4- The electron transport chain - inner mitochondrial membrane / cristae
What is the significance of glycolysis, link reaction, and krebs cycle, taking place in the cytoplasm and mitochondrial matrix?
Location of the necessary enzymes - dehydrogenases being the most important as they catalyse the removal of hydrogen from molecules (oxidation)
What is the role of the loop of DNA and the 70S ribosomes in the mitochondria for aerobic respiration
the loop of DNA contains the genes that code for enzyme whilst the 70S ribosomes they synthesise the enzymes involved in the link reaction and krebs cycle
Explain fully the process of glycolysis in aerobic respiration
1- Glucose is phosphorylated to hexose bisphosphate using 2 ATP: makes glucose more reactive & overcomes the activation energy for the reaction
2- Hexose bisphosphate is split to form two triose phosphate
3- 2x Triose phosphate is oxidised to 2x pyruvate: 2x NAD is reduced to 2x NADH2 at the same time
Energy is released to synthesise 4 ATP from 4 ADP + (2) Pi by substrate level phosphorylation
Give a summary of what is produced at the end of glycolysis in aerobic respiration
each molecule of glucose results in the production of:
2 x pyruvate
2 x NADH2
2 x ATP net (as 2 are used to get 4)
Why does glycolysis have to occur for the link reaction and krebs cycle to be carried out
Glucose can’t enter the mitochondria as there are no glucose carrier proteins within these membranes.
Pyruvate, produced in glycolysis, passes into the mitochondria via carrier proteins in the mitochondrial membrane
Explain fully the process of the link reaction in aerobic respiration
1- Pyruvate is oxidised to acetate, and NAD is reduced to NADH2. Acetate is a 2C molecule so a molecule of CO2 is also produced
2- Acetate combines with co-enzyme A to form acetyl co-enzyme A (Acetyl co-A)
Give a summary of what is produced at the end of the link reaction in aerobic respiration
2 molecules of pyruvate leads to the production of:
2 x NADH2
2 x CO2
2 x Acetyl co-enzyme A
Give a simple description of what the krebs cycle is in aerobic respiration
a series of oxidation and decarboxylation reactions
Give a summary of what is produced at the end of the krebs cycle in aerobic respiration
1 molecule of Acetyl Co-A leads to the production of:
3 x NADH2
1 x FADH2
1 x ATP by substrate level phosphorylation
2 x CO2
Explain fully the process of the krebs cycle in aerobic respiration
Acetyl Co-A (2C) reacts with Oxaloacetate (4C), releasing Co-enzyme A and producing Citrate - a 6C molecule
Citrate is oxidised to 𝝰-ketoglutarate -> one molecule of CO2 is released and NAD is reduced to NADH2
𝝰-ketoglutarate (5C) ix oxidised to Oxaloacetate (4C) -> 2 x NAD are reduced to 2 x NADH2, FAD is reduced to FADH2, 1 molecule of CO2 is released, ATP is synthesised from ADP + Pi
What effect would having less enzymes be on the rate of ATP production in the Krebs cycle in aerobic respiration
less enzymes -> less NADH2 and FADH2 produced -> decreased rate of ATP production
Give a brief description of how the electron transport chain in aerobic respiration works
The reduced co-enzymes NADH2 & FADH2 formed during glycolysis, link reaction and Krebs cycle, provide hydrogen (protons + electrons) for the E.T.C.
E.T.C. take place on the inner-mitochondrial membrane involving a series of electron carriers
What theory is used to explain how the electron transport chain in aerobic respiration works
Chemiosmotic theory
Fully explain the chemiosmotic theory in the electron transport chain in aerobic respiration
When NADH2 and FADH2 are oxidised, protons and high energy electrons are released. These electrons lose energy as they pass along a series of electron carriers
This energy is used to pump protons from the mitochondrial matrix into the intermembrane space, the protons accumulate forming a concentration gradient, the protons move back into the matrix by facilitated diffusion via ATP synthase providing the energy needed to synthesise ATP from ADP + Pi, by oxidative phosphorylation - 1x NADH2 results in 3x ATP, 1x FADH2 results in 2x ATP. The NAD and FAD is reused in the Krebs cycle. Oxygen is the terminal electron acceptor in the ETC, it accepts (2x) protons (from the oxidation of NADH2 and FADH2) and (2x) electrons and is reduced to water
How many molecules of ATP are produced from NADH2 and FADH2 in the E.T.C. in aerobic respiration
Each NADH2 results in 3 x ATP
Each FADH2 results in 2 x ATP
What is the role of oxygen in the E.T.C. in aerobic respiration
Oxygen is the terminal electron acceptor in the E.T.C. -> it accepts protons and electrons, and is reduced to water
What stages in aerobic respiration are substrate level phosphorylation and as oxidative phosphorylation
Glycolysis, Link reaction, Krebs cycle are all substrate level phosphorylation
E.T.C. is oxidative phosphorylation
What is the net number of ATP produced by substrate level phosphorylation in aerobic respiration
4
(2 from glycolysis
2 from 2 cycles of krebs cycle as there are 2x Acetyl Co-A)
What is the net number of ATP produced by oxidative phosphorylation in aerobic respiration
34
What is the total number of ATP produced by in aerobic respiration
38
Without oxygen (anaerobic respiration), what effect does this have in the processes involved in the mitochondria
Without oxygen, the E.T.C. stops, no oxidative phosphorylation occurs, NADH2 can’t be oxidised to NAD, therefore no more NAD can be produced and becomes a limiting factor, preventing the link reaction and Krebs cycle occurring
Explain what happens during anaerobic respiration in animals
Glycolysis continues, as pyruvate is reduced to lactate -> caused by the oxidation of NADH2, and so NAD is available for glycolysis to continue, therefore ATP is still produced
What is the difference in ATP molecules produced in aerobic and anaerobic respiration in animals
In aerobic respiration - 38 molecules of ATP are produced whereas in anaerobic respiration - 2 molecules of ATP are produced as only glycolysis can occur
Explain what happens during anaerobic respiration in plants, fungi & some bacteria
pyruvate is decarboxylated (CO2 molecule is released) so pyruvate (3C) becomes ethanal (2C), ethanal is reduced to ethanol, at the same time NADH2 is oxidised to NAD
What are 4 alternative respiratory substrates to glucose
1- other carbohydrates - glycogen in animals and starch in plants are stores of glucose, glycogen is hydrolysed to glucose, sucrose (hydrolysed to glucose + fructose)
2- Triglycerides
3- Proteins
4- Creatine
Fully describe how triglycerides are used as an alternative respiratory substrate
Triglycerides are hydrolysed into glycerol and fatty acids. Glycerol is a 3C molecule that can be converted to triose phosphate and enter glycolysis. Fatty acids are further broken down into 2C fragments, which enter the link reaction/Krebs cycle. Gram for gram lipids provide about double the ATP than a carbohydrate, but require a large volume/conc of oxygen to respire them, lipids act as thermal insulation in the adipose tissue under the skin.
Fully describe how proteins are used as an alternative respiratory substrate
Proteins are hydrolysed into amino acids, the amino acids are then deaminated in the liver. NH3 is converted into urea and most of the remaining organic acid is converted into acetyl coA -> used in the Krebs cycle
Fully describe how creatine is used as an alternative respiratory substrate
creatine is stored in muscle fibres
at rest creatine is phosphorylated to produce phosphocreatine (CP)
ATP + C -> ADP + CP
During exercise CP is used to quickly regenerate ATP
ADP + CP -> ATP + C
What 3 measurements would you need to take when calculating the rate of oxygen uptake using a pipette with a coloured liquid/bubble inside, boiling tube, and ruler scale
1- distance travelled by liquid/bubble
2- time taken for it to travel that distance
3- internal diameter of capillary tube
What is the units for rate of oxygen consumption
cm3 per minute per gram
