Respiration (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
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Cellular respiration
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Cellular respiration
An exothermic reaction occurring continuously in living cells that releases energy from nutrient molecules, either with oxygen (aerobic) or without oxygen (anaerobic).
Aerobic respiration
The chemical reaction in cells that uses oxygen to break down nutrient molecules to release energy. It is the complete breakdown of glucose and releases a relatively large amount of energy.
Anaerobic respiration
The chemical reaction in cells that breaks down nutrient molecules to release energy without using oxygen. It is the incomplete breakdown of glucose and releases a relatively small amount of energy.
Give the word equation for aerobic respiration.
Glucose + oxygen → carbon dioxide + water (+ energy released)
Give the balanced symbol equation for aerobic respiration.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
List three things organisms need the energy from respiration for.
Chemical reactions to build larger molecules from smaller ones.
Muscle contraction to allow movement.
Keeping warm (to maintain a constant temperature for enzyme activity).
Give the word equation for anaerobic respiration in animals (e.g. in muscles during vigorous exercise).
Glucose → lactic acid (+ energy released)
Give the word equation for anaerobic respiration in plants and fungi (yeast).
Glucose → ethanol + carbon dioxide (+ energy released)
What is fermentation, and why is it economically important?
Fermentation is anaerobic respiration in yeast.
It is important in baking (the carbon dioxide produced makes dough rise) and in brewing (the ethanol produced makes beer).
What is the 'oxygen debt'?
The amount of oxygen required to break down the lactic acid that has built up in the muscles during anaerobic respiration (producing carbon dioxide and water).
Compare the amount of energy released by aerobic and anaerobic respiration.
Aerobic respiration completely breaks down glucose and releases a relatively large amount of energy.
Anaerobic respiration incompletely breaks down glucose and releases a relatively small amount of energy.
In animal muscle cells, anaerobic respiration breaks down glucose to produce , which lowers the pH and can enzymes.
lactic acid / denature
Respirometer
Apparatus used to measure and investigate the rate of oxygen consumption during aerobic respiration in organisms.
What measurement is usually taken as the rate of respiration in a respirometer experiment?
The rate of oxygen consumption (cm³ min⁻¹).
Why are soda-lime pellets included in the respirometer tubes?
To absorb the carbon dioxide produced by the respiring organisms, so that any change in gas volume is due to oxygen being used up.
Why are germinating seeds used in the respirometer experiment?
They are actively respiring and consuming oxygen.
How is the effect of temperature on the rate of respiration investigated?
The respirometer is placed in a thermostatically controlled water bath. The change in gas volume per minute is measured, then the temperature is changed and the experiment is repeated several times at different temperatures.
Which formula is used to calculate the volume of oxygen consumed?
πr²h, where r is the radius of the capillary tube (cm) and h is the distance moved by the manometer fluid (cm) in a minute.
Why can a respirometer not be used to measure the rate of anaerobic respiration?
No oxygen is consumed during anaerobic respiration, so there is no change in gas volume for the apparatus to measure.
Why does the rate of respiration change with temperature?
Respiration relies on enzymes. At low temperatures molecules collide less often, so the rate is slow. At very high temperatures the enzymes denature, so the rate falls.
A respirometer measures the rate of consumption during aerobic respiration.
oxygen
pellets are placed in the tubes to absorb the carbon dioxide produced.
Soda-lime
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