Respiration (AQA GCSE Combined Science: Trilogy: Biology): Flashcards
Exam code: 8464
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Cellular respiration
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Cards in this collection (21)
Cellular respiration
An exothermic reaction, occurring continuously in all living cells, that transfers energy from glucose.
This energy supplies all the processes needed for life.
State three things organisms need the energy from respiration for.
Chemical reactions to build larger molecules from smaller ones.
Movement (muscle contraction).
Keeping warm (maintaining body temperature).
State the word equation for aerobic respiration.
glucose + oxygen → carbon dioxide + water
State the balanced symbol equation for aerobic respiration.
C6H12O6 + 6O2 → 6CO2 + 6H2O
Give the equation for anaerobic respiration in animals, and explain why it transfers less energy.
glucose → lactic acid
The oxidation of glucose is incomplete, so much less energy is transferred than in aerobic respiration.
Give the equation for anaerobic respiration in plants and yeast, and state its economic importance.
glucose → ethanol + carbon dioxide
In yeast this is called fermentation, used to make bread (CO2 makes dough rise) and alcoholic drinks (ethanol).
Compare aerobic and anaerobic respiration in terms of oxygen, products and energy.
Aerobic: needs oxygen; products are carbon dioxide + water; transfers more energy.
Anaerobic: no oxygen; products are lactic acid (animals) or ethanol + carbon dioxide (plants/yeast); transfers less energy.
True or False?
Respiration is the same as breathing.
False.
Respiration is a chemical reaction that transfers energy from glucose inside every living cell. Breathing (ventilation) is the movement of air in and out of the lungs.
State three ways the body responds during exercise to supply muscles with more oxygen.
Heart rate increases.
Breathing rate increases.
Breath volume increases.
Why do heart rate and breathing rate increase during exercise?
Exercising muscles contract more, needing more energy from respiration.
These changes supply the muscles with more oxygenated blood and remove carbon dioxide faster.
What happens in the muscles if insufficient oxygen is supplied during vigorous exercise?
Muscles carry out anaerobic respiration, incompletely oxidising glucose to produce lactic acid.
This releases much less energy than aerobic respiration.
What causes muscle fatigue during long periods of vigorous exercise?
A build-up of lactic acid in the muscles, which causes them to stop contracting efficiently.
Oxygen debt (Higher Tier Only)
The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
How is lactic acid removed from the body after vigorous exercise? (Higher Tier Only)
Blood transports the lactic acid to the liver, where it is converted back into glucose.
The lactic acid is oxidised using the extra oxygen taken in, repaying the oxygen debt.
Metabolism
The sum of all the reactions in a cell or the body.
What supplies the energy for metabolic reactions, and what controls them?
Energy is transferred by respiration.
The reactions are enzyme-controlled and are used to synthesise new molecules.
State the building blocks used to synthesise carbohydrates, lipids and proteins.
Carbohydrates: built from sugars (e.g. glucose).
Lipids: built from fatty acids and glycerol.
Proteins: built from amino acids.
Name three substances that glucose is used to synthesise in organisms.
Starch (energy store in plants).
Glycogen (energy store in animals).
Cellulose (strengthens plant cell walls).
How is a lipid molecule formed?
From one molecule of glycerol combined with three fatty acid molecules.
How are amino acids and proteins formed in metabolism?
Glucose and nitrate ions are used to form amino acids.
Amino acids are then used to synthesise proteins.
What happens to excess protein in the body?
It is broken down to form urea, which is excreted from the body.
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