Every card in Human body systems, Year 10: respiration and exercise
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- Respiration transfers energy to the surroundings. Which word describes a reaction of this type? (one word)
exothermic
HintThe first part of the word means 'out', as in 'exit'.
WhyCellular respiration releases the energy stored in glucose. Some of it is transferred to the surroundings by heating, which is how birds and mammals keep warm.
- Aerobic respiration in symbols: C₆H₁₂O₆ reacts with ____ to give CO₂ and H₂O.
O₂
HintIt is the gas your lungs take from the air.
WhyIn words: glucose + oxygen → carbon dioxide + water. The substances are the same four as in photosynthesis, with reactants and products swapped. AQA asks you to recognise the symbols, not to balance the equation.
- Organisms need the energy from respiration for chemical reactions that ____, for ____, and for keeping ____.
build larger molecules; movement; warm
HintOne is about making things, one is about muscles, and one is about body temperature.
WhyThe energy transferred by respiration supplies everything a living thing does: joining small molecules into big ones such as proteins, contracting muscles, and, in birds and mammals, holding a steady body temperature.
- A pupil says that plants respire only at night, when they cannot photosynthesise. What is wrong with this?
Respiration goes on continuously, day and night, in all living cells
HintAsk whether a cell can ever manage without a supply of energy.
WhyEvery living cell needs energy all the time, so respiration never stops. In daylight a plant photosynthesises as well, usually faster than it respires, which hides the respiration but does not switch it off.
- Respiration that uses oxygen
Aerobic respiration
HintThe same prefix appears in the name of a keep-fit class that leaves you breathing hard.
WhyThis is the usual form of respiration in plant and animal cells. Glucose is completely oxidised to carbon dioxide and water, which transfers far more energy than respiration without oxygen.
- Why does anaerobic respiration transfer much less energy than aerobic respiration?
The glucose is not completely oxidised
HintWithout oxygen the breakdown stops part-way.
WhyIn aerobic respiration, glucose is broken right down to carbon dioxide and water. Without oxygen the breakdown is incomplete, and much of the energy stays locked in the products, such as lactic acid.
- How do the products of anaerobic respiration in muscle cells differ from those in yeast cells?
Muscle cells make lactic acid; yeast cells make ethanol and carbon dioxide
HintOne has a single product that builds up during a sprint; the other gives two, one of them a gas.
WhyBoth start from glucose and neither uses oxygen. In muscles: glucose → lactic acid. In plant and yeast cells: glucose → ethanol + carbon dioxide.
- Anaerobic respiration in yeast cells
Fermentation
HintBrewers and bakers both rely on it.
WhyYeast is a single-celled fungus. When it respires without oxygen it converts glucose to ethanol and carbon dioxide, and the process has economic importance in making bread and alcoholic drinks.
- Fermentation by yeast produces ethanol and carbon dioxide. Which product matters to a baker, and which to a brewer?
Carbon dioxide to the baker; ethanol to the brewer
HintOne of them wants bubbles in dough; the other wants the alcohol.
WhyIn bread dough, the gas forms bubbles that make the dough rise, and the small amount of ethanol evaporates in the oven. In brewing and wine-making, the ethanol is the alcohol in the drink.
- Yeast cells respire anaerobically to give ethanol and carbon dioxide. The cells of which other group of living things do the same: animals or plants? (one word)
plants
HintThink of roots in waterlogged soil, with no air spaces left.
WhyAnimal cells make lactic acid when they respire without oxygen. Plant cells, like yeast, make ethanol and carbon dioxide; AQA gives one equation for both.
- During exercise the ____ rate (felt as the pulse), the breathing rate and the breath ____ (the amount of air in each breath) all increase, supplying the muscles with more oxygenated blood.
heart; volume
HintOne blank is an organ; the other is a quantity measured in cm³ or dm³.
WhyThree things change. Breathing faster and more deeply brings more oxygen into the blood, and a faster pulse delivers that blood to the working muscles more quickly.
- During exercise the lungs take in more air. Why must the heart beat faster as well?
To carry the oxygenated blood to the muscles more quickly
HintOxygen in the lungs is no use to a leg until something delivers it.
WhyWorking muscles respire faster and need more oxygen and glucose. The lungs load more oxygen into the blood, but it is the circulation that delivers it, and that also carries away the extra carbon dioxide.
- During a long period of vigorous activity, muscles become fatigued. What does this mean for the way they work?
They stop contracting efficiently
HintThink about what a muscle's job is, and how well a tired one does it.
WhyIf too little oxygen reaches the muscles, they respire anaerobically and lactic acid builds up, creating an oxygen debt. After a long spell of hard work the muscles cannot keep contracting as strongly as before.
- A pupil's pulse is 70 beats per minute at rest and 133 beats per minute just after running. What is the percentage increase? (number only)
90
HintFind the rise first, then compare it with the starting value, not the final one.
WhyIncrease = 133 − 70 = 63 beats per minute. Percentage increase = 63 ÷ 70 × 100. Measuring pulse or breathing rate before and after activity is the standard way to investigate the effect of exercise on the body.
- After exercise, where is the lactic acid from the muscles taken, and what happens to it there?
Blood carries it to the liver, where it is converted back into glucose
HintThe same organ deals with alcohol and stores glycogen.
WhyLactic acid does not stay in the muscles. It is transported in the blood flowing through them to an organ that turns it back into a useful sugar, and this needs oxygen.
- The extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
Oxygen debt
HintFinancially, the second word is something you owe and must repay.
WhyIt is why you keep breathing hard after you stop running. The amount depends on how much lactic acid built up, so a harder or longer burst of anaerobic work takes longer to recover from.
1★ GCSE-BIOL-HUM-0033
2★ GCSE-BIOL-HUM-0034
3★ GCSE-BIOL-HUM-0035
4★ GCSE-BIOL-HUM-0036
5★ GCSE-BIOL-HUM-0037
6★ GCSE-BIOL-HUM-0038
7★ GCSE-BIOL-HUM-0039
8★ GCSE-BIOL-HUM-0040
9★ GCSE-BIOL-HUM-0041
10★ GCSE-BIOL-HUM-0042
11★ GCSE-BIOL-HUM-0043
12★ GCSE-BIOL-HUM-0044
13★ GCSE-BIOL-HUM-0045
14★ GCSE-BIOL-HUM-0046
15★ GCSE-BIOL-HUM-0047
16★ GCSE-BIOL-HUM-0048
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