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Respiration

Aerobic – requires oxygen and produces carbon dioxide, water and much ATP

Anaerobic – absence of oxygen and produces lactate (animals) or ethanol and carbon
dioxide (plants and fungi)
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Glycolysis Link Reaction Krebs Cycle Oxidative Phosphorylation

Glycolysis Fermentation

Glycolysis
• Takes place in cytoplasm of cells
...

• Doesn’t require oxygen
...
Phosphorylation of Glucose to Glucose Phosphate – glucose must first be made more
reactive by adding 2 phosphate molecules (phosphorylation)
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The phosphate molecules come
from the hydrolysis of 2 ATP molecules
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2
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3
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The hydrogen carrier
NAD collects the hydrogen ions forming 2 reduced NAD
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• Occurs twice for every glucose molecule as 2 pyruvates are given off from glycolysis
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1
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The 3-carbon pyruvate loses a carbon dioxide
molecule (decarboxylated) and 2 hydrogens
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2
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• Takes place in matrix of mitochondria
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1
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Coenzyme A goes back into the link reaction to be reused
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Citrate undergoes decarboxylation and dehydrogenation (hydrogen used to produce
reduced NAD) to produce a 5-carbon molecule
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The 5-carbon molecule is converted into a 4C molecule (oxaloacetate) which then
combines with a new molecule of acetylcoenzyme A to begin the cycle again
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• The coenzyme NAD works with dehydrogenase enzymes that catalyse the removal
of hydrogen atoms from substrates and transfer them to other molecules involved in
oxidative phosphorylation
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g
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Products form 2 Krebs Cycles
2 Coenzyme A
2 Oxaloacetate

4 Carbon Dioxide
2 ATP
6 Reduced NAD
2 Reduced FAD

Where it Goes
Reused in Link Reaction
Regenerated for use in the next Krebs
Cycle
Released as Waste Products
Used for Energy
Oxidative Phosphorylation
Oxidative Phosphorylation





















Oxidative Phosphorylation
• Takes place in cristae of mitochondria
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• Many mitochondria in metabolically active cells e
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muscle cells
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1
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The hydrogen atoms split into protons and electrons
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The electrons move down the electron transport chain (made up of electron
carriers) losing energy at each stage
...
Concentration of protons is higher in the intermembrane space than the
mitochondrial matrix so it forms an electrochemical gradient
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Protons move down the electrochemical gradient via ATP synthase channels
synthesising the formation of ATP
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5
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Oxygen is the final proton acceptor
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•

The greater the energy that is released in a single step the more of it is released as
heat and the less there is available for more useful purposes
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For this reason the electrons carried by NAD and FAD are not transferred in one
explosive step but instead are passed along a series of electron carrier molecules
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Respiration of Lipids
Before being respired lipids are first hydrolysed to glycerol and fatty acids
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The fatty acid component is broken down into 2C fragments which are
converted to acetyl coenzyme A
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Oxidation of lipids
produces 2C fragments of carbohydrate and hydrogen atoms
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Respiration of Protein
It is hydrolysed to its constituent amino acids which undergo deamination (removal
of amino acids group) before entering the respiratory pathway at different points
depending on the number of carbon atoms they contain
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Mitochondrial Diseases
• Affect functioning of the mitochondria and affect how proteins are involved in
oxidative phosphorylation or the Krebs cycle function, reducing ATP production
...

• Some lactate will also diffuse into the bloodstream leading to high lactate
concentration in the blood
...

For glycolysis to continue its products of pyruvate and hydrogen must constantly be
removed
...
Replenishment of NAD is achieved by the pyruvate molecule from glycolysis
accepting the hydrogen from reduced NAD
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Plants and some Microorgansims – bacteria, fungi and some cells of plants e
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root cells
under waterlogged conditions
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Pyruvate + Reduced NAD Ethanol + Carbon Dioxide + Oxidised NAD
Used in the brewing industry e
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wine and beer production
...
Lactate is
an acid it causes pH changes effecting enzyme action
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This is cytochrome oxidase that catalyses the addition of
hydrogen ions and electrons to oxygen to form water
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1
...

2
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3
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Complete
Nuclei Only
Ribosomes Only
Mitochondria
Remaining

Homogenate

Only

Cytoplasm Only



Carbon
Dioxide

Lactate

Carbon
Dioxide

Lactate

Carbon
Dioxide

Lactate

Carbon
Dioxide

Lactate

Carbon
Dioxide

Lactate

Glucose



















































Pyruvate
Glucose +
Cyanide
Pyruvate
+ Cyanide

Respirometer Experiment
• Used to indicate rat of aerobic respiration by measuring the amount of oxygen
consumed by and organisms over a period of time
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• Control tube set up in same way as woodlouse tube but eh woodlice are substituted
with glass beads of the same mass
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CO2 is absorbed by potassium hydroxide
...

• Oxygen consumption can also be calculated by recording the movement of the fluid
in the manometer
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For 10 mins allow the apparatus to equilibrate by removing the syringe and opening
the tap and to allow the respiration rate of the woodlice to stabilise in their new
environment
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After 10 mins close the tap and attach the syringe
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Use the syringe to reset the manometer so that the ends of the fluid are at the same
level on either side of the ‘U’
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4
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5
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The difference between this figure and the figure taken at the start of the
experiment is he oxygen consumption for this time period
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Repeat experiment to calculate mean volume of oxygen usage
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• Rate of CO2 production gives an indication of yeast’s respiration rate
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g
...

• Can use a control experiment at each temperature where no yeast is present
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Aerobic
1
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g
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Place test tube in water bath at one of the temperatures being investigated and leave
for 10 mins to allow the temperature of the substrate to stabilise
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Add known mass of dried yeast e
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Saccharomyces cerevisiae to the test tube and
stir of 2 minutes
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Once the yeast has dissolved put a bung with a tube attached to a gas syringe in the
tip of the test tube
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Start a stopwatch once bung is on
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At regular time intervals record the volume of CO2 in the gas syringe
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7
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Anaerobic
1
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After the yeast has dissolved trick some liquid paraffin down the inside of the test
tube so that it settles on and completely covers the surface of the solution to stop
oxygen form reaching the yeast
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Put a bung with a tube attached to a gas syringe (syringe set at 0)
4

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