Unit 1.6 Respiration Flashcards
Respiration
The release of energy stored in glucose molecules, when chemical bonds are broken.
Respiration is enzyme controlled, and happens at low temperatures in all cells.
ATP
An energy transfer molecule found in all cells.
Energy released in respiration is stored in a high energy bond which attaches the 3rd phosphate onto ADP to make ATP.
This bond is broken when energy is required by the cell.
Why do cells need energy?
Active transport
Muscle contraction
Cell division
Protein synthesis
Synthesis of sugars (Calvin cycle)
Bioluminescence
Respiration - 1st stage
Takes place in the cytoplasm and does not require oxygen.
Glucose is broken down into 2 molecules of pyruvate in a series of enzyme controlled steps.
2 molecules of ATP are generated.
Aerobic respiration
2nd stage of respiration that occurs when oxygen is present.
Pyruvate enters the mitochondria and is fully broken down to carbon dioxide and water in a series of enzyme controlled reactions.
Energy rich hydrogen is used to generate large quantities of ATP, before combining with oxygen to produce water.
Equation for aerobic respiration
glucose + oxygen ——————-> carbon dioxide + water + energy
Fermentation (anaerobic respiration)
The alternative 2nd stage of respiration that occurs in the absence of oxygen.
Pyruvate is partially broken down to ethanol and carbon dioxide in plants and yeast, and lactate in animals.
It occurs in the cytoplasm.
No more ATP is generated (just the 2 x ATP from the 1st stage).
Fermentation occurs to remove the pyruvate and keep the 1st stage running.
Lactate
Product of fermentation in animal cells - formed by the partial breakdown of pyruvate.
Causes muscle fatigue under anaerobic conditions eg. sprinting.
Converted back to pyruvate when oxygen is available again, repaying the ‘oxygen debt’.
Fermentation equation (plant and yeast cells)
glucose ——————–> carbon dioxide + ethanol + energy
Fermentation equation (animals cells)
glucose —————————–> lactate + energy
Mitochondria (mitochondrion = singular)
The site of aerobic respiration in cells.
Pyruvate enters the mitochondria and is fully broken down in the presence of oxygen.
Very active cells have larger numbers of mitochondria. eg. muscle cells.
Respirometer
A piece of equipment used to measure the rate of respiration by measuring oxygen uptake.
Sodium hydroxide/soda lime is used to absorb carbon dioxide, so that the coloured dye moves along the scale towards the organism as oxygen is taken in.
