aerobic respiration

where does aerobic respiration in eukaryotic cells take place

the mitochondria

how many membranes does the mitochondria have

2 - the outer and inner membrane

features of the outer membrane of the mitochondria

smooth and permeable to several small molecules

features of the inner membrane of the mitochondria

folded (cristae), less permeable, site of electron transport chain and location of atp synthase (both used in oxidative phosphorylation)

features of the intermembrane space of the mitochondria

low pH due to the high concentration of protons, concentration gradient across the inner membrane is formed during oxidative phosphorylation - essential for atp

features of the matrix in the mitochondria

is an aqueous solution within the inner membranes of the mitochondrion, contains ribosomes, enzymes and circular mitochondrial DNA needed for function

3 ways the structure of the mitochondria is adapted / helps carry out its function

1. have a large surface area due to the presence of cristae - enables the membrane to hold many etc proteins and atp synthase enzymes

2. more active cells have larger mitochondria, more tightly packed cristae enabling synthesis of more ATP due to larger surface area

3. number of mitochondria in each cell can vary depending on cell activity ie muscle cells

aerobic respiration

the transfer of chemical potential energy from nutrient molecules into a usable energy form (through atp synthesis) that can be used for work within an organism - breaking down a respiratory substrate

aerobic respiration chemical equation

C6 H12 06 + 6O2 —> 6CO2 + 6H20 + 2870KJ

aerobic respiration word respiration

glucose + oxygen —> carbon dioxide + water + energy

autotrophs

organisms that are able to synthesis their own usable carbon compounds from co2 in the atmosphere through photosynthesis

heterotrophs

require a supply of pre-made usable carbon compounds which they get from food

four stages of aerobic respiration

glycolysis, link reaction, krebs cycle, oxidative phosphorylation

summarise glycolysis and where it takes place

phosphorylation and splitting of glucose molecule in 2 in cell cytoplasm

summarise the link reaction and where it takes place

decarboxylation and dehydrogenation of pyruvate in the matrix of mitochondria

summarise the krebs cycle and where it takes place

cyclical pathway with enzyme-controlled reactions in the matrix of mitochondria

summarise oxidative phosphorylation and where it takes place

production of ATP through oxidation of hydrogen atoms in the inner membrane of mitochondria

what does glycolysis produce

2 pyruvatre (3c) molecules, net gain 2 ATP and 2 reduced NAD

what are the 5 steps of glycolysis

phosphorylation, lysis, oxidation, dephosphorylation, pyruvate produced

explain phosphorylation and give the equation - first step of glycolysis

glucose (6c) is phosphorylated by 2 ATP to form fructose bisphosphate (6c) - glucose + 2atp —> fructose bisphosphate

explain lysis and give the equation - second step of glycolysis

fructose bisphosphate (6c) splits into two molecules of triose phosphate (3c) - fructose bisphosphate —> 2 triose phosphate

explain oxidation - third step of glycolysis

hydrogen is removed from each molecule of triose phosphate and transferred to coenzyme NAD, forming 2 reduced NAD

chemical equation for oxidation in glycolysis - third stage

4H + 2NAD —> 2NADH + 2H+

explain dephosphorylation and give the equation - fourth step of glycolysis

phosphates are transferred from the intermediate substrate molecules to form 4 atp through substrate-linked phosphorylation - 4pi + 4adp —> 4atp

explain when pyruvate is produced and give the equation - fifth (last) step of glycolysis

the end product of glycolysis which can be used in the next stage of respiration - 2 triose phosphate —> 2 pyruvate

what happens to the pyruvate after glycolysis

when oxygen is available it will enter the mitochondrial matrix, across the double membrane of the mitochondria via active transport

what does the active transport of pyruvate across the mitochondrial matrix require

a transport and a small amount of atp

why is it called the link reaction

it links glycolysis to the krebs cycle

what is the first step of the link reaction

dehydrogenation - pyruvate is oxidised by enzymes to produce acetate, CH3CO(O) and carbon dioxide, requiring the reduction of NAD to NADH

the second step of the link reaction

combination with coenzyme A to form acetyl coenzyme A (acetyl CoA)

what does the link reaction produce

acetyl CoA, co2 and reduced NAD

chemical equation of the link reaction

pyruvate + NAD + CoA —> acetyl CoA + co2 + reduced NAD

what does coenzyme A consist of

a nucleotide (ribose and adenine) and a vitamin

how many pyruvate molecules are produced per glucose molecule (link reaction)

two

what does the krebs cycle consist of

a series of enzyme-controlled reaction

what enters the krebs cycle from the link reaction and other metabolic pathyways

2 carbon acetyl CoA and amino acids

what takes place in the first reaction of the krebs cycle where coenzyme A is released

4c oxaloacetate accepts 2c acetyl fragment from acetyl coa to form 6 carbon citrate

what happens after the 6c citrate is formed in the first stage of the krebs cycle

citrate is converted back into oxaloacetate through a series of oxidation reduction (redox) reactions

as well as the regeneration of oxaloacetate, what else happens to the citrate after it is formed

decarboxylation - releases co2 and oxidation/dehydrogenation - releasing H atoms that reduce coenzymes NAD and FAD

dehydrogenation of citrate in the krebs cycle chemical equation

3NAD and 1 FAD —> 3NADH + H+ and FADH2

What does substrate linked phosphorylation produce in the krebs cycle

a phosphate is transferred to ADP, forming 1 ATP

how many times does the krebs cycle turn per molecule of glucose

2 times per glucose molecule

what is produced in the krebs cycle per glucose molecule

2 ATP molecules, 6 NADH molecules, 2 FADH molecules and 4CO2 molecules

why are the coenzymes FAD and NAD important

accept hydrogen atoms when they become available at points during aerobic respiration, transferring them to the electron transport chain on the inner mitochondrial membrane - where hydrogen are removed from coenzymes

what happens when the hydrogen atoms are removed from the coenzymes

the coenzymes are oxidised

why are hydrogen ions and electrons important in the etc at the end of respiration

they play a role in the synthesis of ATP

what happens to the electrons and hydrogen ions from reduced NAD and FAD

electrons are given to the electron transport chain and hydrogen ions are released when the electrons are lost

what does the electron transport chain drive

a proton gradient, driving hydrogen ions across the inner mitochondrial membrane space

what provided the energy required for atp synthesis

movement of hydrogen ions down the proton gradient - my h+ ions in the intermembrane space

redox reaction of NAD

NAD + 2H ->← NADH + H+

redox reaction of FAD

FAD + 2H →← FADH2

how much and where is reduced NAD produced (what cycles)

2 from glycolysis, 2 from the link reaction and 6 from the krebs cycle

how much and where is reduced FAD produced (what cycles)

2 from the krebs cycle

what does oxidative phosphorylation produce

many atp molecules and water from oxygen

name of the current model for oxidative phosphorylation

chemiosmotic theory

what does the chemiosmotic theory state (3)

1. energy from electrons passed through a chain of proteins in the membrane is used to pump protons up their concentration gradient into the intermembrane space

2. the H are then allowed to flow by facilitated diffusion through a channel in ATP synthase into the matrix

3. energy of the H flowing down their conc gradient is harnessed resulting in the phosphorylation of ADP into ATP

first steps of oxidative phosphorylation

hydrogen atoms are donated by reduced NAD and FAD from the krebs cycle, hydrogen atoms split into protons (H+ ions) and electrons

what happens to the electrons after hydrogen atoms splits (oxidative phosphorylation)

electrons enter the electron transport chain, release energy as they move through the electron transport chain

what happens to the energy released as the electrons move through the electron transport chain (oxidative phosphorylation)

the released energy is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space - establishing a proton gradient between the intermembrane space and the matrix

how is atp produced in the final steps of oxidative phosphorylation

protons return to the matrix via facilitated diffusion through the channel protein atp synthase, the movement of protons down their concentration gradient provides energy for ATP synthesis

how is water produced, finally, in oxidative phosphorylation

oxygen acts as the final electron acceptor and combines with protons and electrons at the end of the electron transport chain to form water

why is oxygen important for oxidative phosphorylation (2)

oxygen acts as the final electron acceptor, without o2 the electron transport chain cannot continue as electrons have nowhere to go. without o2 accepting electrons (and hydrogens) the reduced coenzymes NADH and FADH2 cannot be oxidised to regenerate NAD and FAD

why do electron carriers - part of the electron transport chain - have to establish a concentration gradient between the matrix and the inner membrane

the inner membrane is impermeable to hydrogen ions so electron carriers pump protons across the membrane

what chemicals from the krebs cycle does oxidative phosphorylation require

NADH and FADH2

6 consequences when there isn’t enough oxygen available

1. no final acceptor of electrons from the electron transport chain

2. electron transport chain stops functioning

3. no more ATP produced via oxidative phosphorylation

4. reduced NAD and FAD aren’t oxidised by an electron carrier

5. no oxidised FAD and NAD for dehydrogenation in the krebs cycle

6. krebs cycle stops