Respiration Flashcards
Why do organisms need to respire
Produces ATP currency for:
a) active transport against concentration gradients e.g. to absorb nutrients to small intestine and soil
b) metabolic reactions e.g. to form peptide bonds in protein synthesis
c) muscle contraction
Releases heat for thermoregulation
Describe the structure of a mitochondrion
Surrounded by double membrane
Folded inner membrane forms cristae: site of electron transport chain
Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids proteins
Name the 4 stages of aerobic respiration and where they occur
Glycolysis: Cytoplasm
Link reaction: Mitochondrial matrix
Krebs cycle: Mitochondrial matrix
Oxidative phosphorylation via electron transfer chain: membrane of cristae
Outline the stages of glycolysis
Glucose is phosphorylated to hexose bisphosphate
Hexose bisphosphate splits into 2x triose phosphate
2x TP is oxidised to 2x pyruvate
Net gain of 2x reduced NAD and 2x ATP per glucose
How does pyruvate from glycolysis enter the mitchondria
Via active transport
What happens during the link reaction
- Oxidation of pyruvate to acetate. Per pyruvate molecule: net gain of 1x CO2 (decarboxylation) and 2H atoms (used to reduce 1x NAD)
- Acetate combines with Coenzyme A (CoA) to form Acetylecoenzyme A
Give a summary reaction for the link equation
Pyruvate + NAD + CoA —> Acetyl CoA + reduced NAD + CO2
What happens in the Krebs cycle
Series of REDOX reactions produces:
- ATP by substrate level phosphorylation
- Reduced Coenzymes
- CO2 from decarboxylation
Begins when acetyl group from Acetyle CoA (2C) reacts with oxaloacetate (4C). Cycle regenerates oxaloacetate
What is the electron transfer chain (ETC)?
Series of carrier proteins embedded in membrane of the cristae of the mitochondria
Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration
What happens in the electron transfer chain
Electrons released from reduced NAD and FAD undergo successive redox reactions
The energy released is coupled to maintaining successive redox reactions
Oxygen acts as final electron acceptor
How does chemiosmosis produce ATP during aerobic respiration
Some energy released from the ETC is coupled to active transport of H+ ions (Protons) from mitochondrial matrix into intermembrane space
H+ ions move down concentration gradient into mitochondrial matrix via channel protein ATP synthase
State the role of oxygen in aerobic respiration
Final electron acceptor in electron transfer chain
(produces water as a byproduct)
Name the stages in respiration that produce ATP by substrate-level phosphorylation
Glycolysis (anaerobic)
Krebs cycle (aerobic)
What happens during anaerobic respiration in animals
Only glycolysis continues
Reduced NAD + pyruvate —> oxidised NAD (for further glycolysis) + lactate
What happens during anaerobic respirartion in some microorganisms e.g. yeast and some plant cells
Only glycolysis continues, so much less ATP is produced compared to aerobic respiration
Pyruvate is decarboxylated to form ethanol
Ethanal is reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis
What are the benefits of being able to respire anaerobically
ATP production for vital metabolic processes continues
Production of ethanol / lactate converts reduced NAD back into NAD so glycolysis can continue = maximum yield of ATP in the conditions
Suggest how a student could investigate the effect of a named variable on the rate of respiration of a single-celled organism
- Use respirometer (pressure changes in boiling tube cause a drop of coloured liquid to move)
- Use a dye as the terminal electron acceptor for the ETC
What is the purpose of sodium hydroxide solution in a respirometer set up to measure the rate of anaerobic respiration
Absorbs CO2 so that there is a net decrease in pressure as O2 is consumed
How could a student calculate the rate of respiration using a respirometer
Volume of O2 produced or CO2 consumed / time x mass of sample
Volume = distance moved by coloured drop x (0.5 x capillary tube diameter)^2 x Pi
Name two types of molecule that can be used as alternative respiratory substrates
Amino acids from proteins
Glycerol and fatty acids from lipids
What is the respiratory quotient (RQ)?
RQ = CO2 produced / O2 consumed
Can be used to determine: respiratory substrate being used (carbohydrates: 1.0, lipids: 0.8, proteins: 0.9)
If organism is undergoing anaerobic respiration (anaerobic values are larger)
Why do different respiratory substrates have different relative energy values
Depends on the number of hydrogens in the structure which are oxidised to water e.g. the number of hydrogens is greater in fatty acids than carbohydrates
