respiration

why do organisms need to respire

why do organisms need to respire

• produce ATP for

  • active transport against conc gradients ex. to absorb nutrients from s intestine/soil

  • metabolic reactions ex. form peptide bonds in protein synthesis

  • muscle contraction

• releases heat energy for thermoregulation

structure of mitochondrion

• double membrane bound organelle

• folded inner membrane forms cristae: site of ETC

• fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins

4 main stages of aerobic respiration + location

glycolysis: cytoplasm

link reaction: mitochondrial matrix

krebs cycle: mitochondrial matrix

oxidative phosphorylation: via ETC, membrane of cristae

stages of glycolysis

glucose phosphorylated to hexose bisphosphate by 2 ATP

hexose bisphosphate splits into 2 triose phosphate

2 TP oxidised to 2 pyruvate

net gain of 2 reduced NAD, 2 ATP per glucose

how pyruvate from glycolysis enters mitochondria

active transport

stages of link reaction

oxidation of pyruvate to acetate

net gain of 1 CO2 (decarboxylation), 2 H atoms (used to reduce 1 NAD)

acetate combines w coenzyme A to form acetylcoenzyme A

summary equation for link reaction

Pyruvate + NAD + CoA → acetyl CoA + reduced NAD + CO2

stages of 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 electron transfer chain (ETC)

series of carrier proteins embedded in membrane of cristae of mitochondria

produces ATP by oxidative phosphorylation via chemiosmosis during anaerobic respiration

what happens in electron transfer chain (ETC)

electrons released from reduced NAD + FAD undergo successive redox reactions

energy released is coupled to maintain proton gradient/released as heat

oxygen acts as final electron acceptor

how does chemiosmosis produce ATP during aerobic respiration

some energy released from ETC is coupled to active transport of protons from mitochondrial matrix to intermembrane space

protons move down conc gradient into mitochondrial matrix via channel protein ATP synthase

ATP synthase catalyses ADP + Pi → ATP

state role of oxygen in aerobic respiration

final electron acceptor in ETC

produces byproduct water

stages in respiration that produce ATP by substrate level phosphorylation

glycolysis (anaerobic)

krebs cycle (aerobic)

what happens during anaerobic respiration in mammals?

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 produced compared to aerobic respiration

pyruvate decarboxylated to form ethanal

ethanal reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis

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 = max yield of ATP in conditions

suggest how student could investigate effect of named variable on rate of respiration of single celled organism

use respirometer - pressure changes in boiling tube cause drop of coloured liquid to move

use dye as terminal electron acceptor for ETC

purpose of sodium hydroxide solution in respirometer set up to measure rate of reaction

absorbs CO2 = net decrease in pressure as O2 is consumed

how could rate of respiration be calculated using respirometer

volume of O2 produced or CO2 consumes/time x mass of sample

volume = distance moved by coloured drop x (0.5 x capillary tube diameter)2 x pi

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 anaerobically respiring (anaerobic values = larger)

why diff respiratory substrates have diff relative energy values

depends on number of hydrogens in structure which are oxidized to water ex. number of hydrogens is greater in fatty acids than carbohydrates