5.2.2: Respiration Flashcards
Why do organisms need to respire?
● Produces ATP as energy currency for:
a) active transport against concentration gradients e.g.
to absorb nutrients from small intestine/soil.
b) metabolic reactions e.g. to form peptide bonds in
protein synthesis.
c) muscle contraction.
● Releases heat energy 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 main stages in 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 by 2x ATP. - Hexose bisphosphate splits into 2x triose
phosphate (TP). - 2x TP is oxidised to 2x pyruvate.
Net gain of 2x reduced NAD & 2x ATP per glucose.
How does pyruvate from glycolysis enter the
mitochondria?
active transport
What happens during the link reaction?
- Oxidation of pyruvate to acetate.
per pyruvate molecule: net gain of 1xCO2
(decarboxylation) & 2H atoms (used to reduce
1xNAD). - Acetate combines with coenzyme A (CoA) to
form Acetylcoenzyme A
Give a summary equation for the link reaction.
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 Acetyl 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 mitochondria.
Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration.
What happens in the electron transfer chain (ETC)?
Electrons released from reduced NAD & FAD
undergo successive redox reactions.
The energy released is coupled to maintaining
proton gradient or released as heat.
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.
ATP synthase catalyses ADP + Pi → ATP
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 respiration 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 ethanal.
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 aerobic
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 π.
Name 2 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 = carbon dioxide produced / oxygen 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
