Respiration
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Transcript of Respiration
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RESPIRATION
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RESPIRATION
• This is the release of energy from food.• Different from gas exchange or breathing.• Respiration occurs in cells, in the
cytoplasm and the mitochondria.
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SOURCES OF ENERGY
• We get energy from carbohydrates, lipids and proteins.
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AN ANALOGY
• The energy in the food we eat is a $100 bill, if you tried to buy a box of matches or some gum, you would be asked for something smaller like a $5 bill.
• The glucose in the food we eat is the $100 and the smaller $5 is ATP (adenosine triphosphate).
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ATP – THE UNIVERSAL ENERGY CARRIER
• This carries the energy to power all metabolic reactions in living things.
• ATP and ADP (Adenosine diphosphate) are very similar, ATP carries the energy, while ADP is an empty carrier.
• The energy is carried in the 3rd phosphate bond.
• When ATP gives up energy it loses a phosphate to become ADP.
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ATP CONT
• The ADP then goes back into the cytoplasm and the mitochondria to be recharged.
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THE ENERGY CYCLE
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NAD – THE HYDROGEN CARRIER
• Most of the energy used to charge up ATP comes from the hydrogen in glucose.
• The carbon dioxide formed is a waste product which is exhaled.
• The Hydrogen from various steps needs to be carried to where it is needed, this is done by a hydrogen carrier NAD (nicotinamide adenine dinucleotide)
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NAD – THE HYDROGEN CARRIER
NAD NADH2
H2
H2
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NAD CONT
• NAD is a coenzyme, which uses one of the B complex vitamins in its structure. If this is missing from the diet, an animal will become deficient in NAD.
• Respiration will be affected and the animal will always be tired.
• In humans the deficiency disease is pellagra, symptoms include dermatitis, diarrhoea, mental disturbance, muscular weakness and fatigue.
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FAD
• Flavin adenine dinucleotide.• Another hydrogen carrier involved in the
Kreb’s cycle.
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CO-ENZYME A
• An acetyl group is formed in glycolysis.• This has to be carried to the next step by a
carrier called co-enzyme A.
Acetyl Co-A Co-A
Acetyl
Acetyl
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AEROBIC RESPIRATION
• This requires oxygen.
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
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GLYCOLYSIS• Takes place in the cytoplasm.• Needs 2 ATP to kick start.• The process charges 4 ATP so there is a net
gain of 2 ATP.• Glucose is converted into 2 molecules of a 3C
pyruvate.
• 2 NADs pick up Hydrogen to become NADH2. These are carried off to the mitochondrial membranes and the electron transport chain.
• No oxygen is needed in glycolysis.
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GLYCOLYSIS
Glucose
2 Pyruvate
2 ADP
2 ATP
NAD
NADH2
Aerobic pathway
To electron transport chain
Anaerobic pathway
Anaerobic
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FORMATION OF ACETYL CO-ENZYME A
• The pyruvate loses a C (forming CO2) to become a 2C acetyl group.
• This is carried by Co-A to the Kreb’s Cycle.
• This takes place in the matrix of the mitochondria.
• The Co-A drops off the acetyl group, then goes back to the end of glycolysis to pick up more acetyl groups.
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FORMATION OF ACETYL CO-ENZYME A
Pyruvate (C3)
Acetyl Co-A (C2)
Co-A
The Kreb’s Cycle
2NADH2
CO2
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THE KREB’S CYCLE
• This takes place in the inner matrix of the mitochondria.
• In a complex series of chemical reactions, the acetyl group joins with other chemicals in a returning cycle.
• CO2 is released and a small amount of ATP is produced.
• Many NADs are charged to form NADH2, which are carried to the electron transfer system.
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KREB’S CYCLE (CITRIC ACID CYCLE)
Acetyl Co-A (C2)
Citric Acid (C6)
C5
C4
CO2
CO2NAD
NAD
NADH2
NADH2
ADP
ATP
To electron transport
chain
To electron transport
chain
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THE ELECTRON TRANSFER SYSTEM OR RESPIRATORY
CHAIN• This is located on the membranes or
cristae of the mitochondria.• The system consists of a row of
cytochromes, which pass hydrogen electrons down from one to the other.
• This results in a series of oxidation and reduction reactions which release about 3 ATPs for every hydrogen involved.
• One molecule of glucose can charge up to 38 molecules of ATP.
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THE ELECTRON TRANSFER SYSTEM OR RESPIRATORY
CHAIN• Think of the cytochromes as a row of
springs, the electrons bounce down the springs.
• Each bounce gives off energy to help charge up ADP to form ATP.
• At the end of this stage the low energy hydrogen joins with oxygen and forms water.
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ANAEROBIC RESPIRATION OR FERMENTATION
• If there is no oxygen, the electron transport system blocks up, the Kreb’s Cycle jams up and so on. Another acceptor has to be found for all the hydrogen.
• In the absence of oxygen, glycolysis can still occur.
• Different things happen in plants and animals.
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ANAEROBIC METABOLISM IN PLANTS
• Ethyl alcohol and carbon dioxide are given off.
• The NAD is cleared to pick up some more hydrogen.
Pyruvate + NAHD2 ethanol + Carbon dioxide + NAD + 2 ATP
•Quite common in bacteria, fungi such as yeast, and the seeds of some plants e.g. peas
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ANAEROBIC METABOLISM IN ANIMALS
• The hydrogen is passed to the pyruvate, and the end product is lactic acid.
• The NAD is cleared to keep this cycle of glycolysis going.
Pyruvate + NAHD2 lactic acid + NAD + 2 ATP
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SUMMARISING ANAEROBIC
RESPIRATIONGlucose
Pyruvate
Lactic Acid
Ethanol + Carbon Dioxide
NADH2
NADH2
NAD NAD
2ADP2ATP
PlantsAnimals
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FACTORS THAT CAN AFFECT RESPIRATION
• The process of respiration is run by enzymes, so anything which affects enzyme action will affect respiration.– Temperature– pH– Enzyme and substrate concentration– Can be poisoned
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FACTORS THAT CAN AFFECT RESPIRATION
• An energy source is needed (glucose, fats or proteins.)
• Sufficient oxygen is needed• Carbon dioxide must not be allowed to
accumulate or it will slow respiration down.• With anaerobic metabolism, the ethanol
produced can poison off yeast cells.