Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

4.4Unit 1: Breathing and respiration

Respiration — Cambridge Checkpoint Biology 0893 Revision Notes & Topical Questions

5 min read 9 parts Lesson 4 of 4 2 quizzes

📚 Cambridge Checkpoint Biology 0893 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read
Lesson summary

4.4 Respiration — CHECKPOINT BIOLOGY 0893 notes: State why cells need energy, explain how aerobic respiration releases energy from glucose, and describe how respiration produces heat.The body needs energy for many reasons.Movement.Sending electrical impulses along neurones.Keepin…

  • Mitochondria
  • Keeping the body warm when it is cold
  • All energy comes from the food that is eaten, and carbohydrates are especially good sources of energy
  • The digestive system breaks carbohydrates down to a sugar called glucose, which goes into the blood
  • The blood delivers glucose to every cell in the body
  • Energy has to be changed from one type to another, or transferred, in order to make something happen

Section 1 of 9Why energy is needed

1
The body needs energy for many reasons.
  • Movement.
  • Sending electrical impulses along neurones.
  • Keeping the body warm when it is cold.
2
All energy comes from the food that is eaten, and carbohydrates are especially good sources of energy.
3
The digestive system breaks carbohydrates down to a sugar called glucose, which goes into the blood.
4
The blood delivers glucose to every cell in the body.

Section 2 of 9Releasing energy from glucose

1
Energy has to be changed from one type to another, or transferred, in order to make something happen.
2
Glucose is an energy store, because its energy is locked up inside it.
3
Mitochondria release the energy from glucose so the cell can use it.
  • Mitochondria are tiny structures inside cells, and most cells have many of them.
4
Mitochondria carry out a chemical reaction called aerobic respiration.
  • Aerobic means that it uses oxygen from the air.
5
Energy is released in a very controlled way, a little at a time, just enough for the cell's needs.
6
Cells that use a lot of energy, such as neurones, have more mitochondria than cells such as cheek cells.

Section 3 of 9Aerobic respiration equation

1
Word equation: glucose + oxygen → carbon dioxide + water (+ energy released).
2
Symbol equation: C6H12O6 + 6O2 → 6CO2 + 6H2O.
3
The reactants are glucose and oxygen, and the products are carbon dioxide and water.
4
Carbon dioxide is made in respiration, so expired air contains more carbon dioxide than inspired air.

Section 4 of 9Getting glucose and oxygen to the cells

1
Food is digested and glucose is absorbed into the blood.
2
Oxygen enters the blood in the air sacs of the lungs and is carried by red blood cells.
3
The blood carries glucose and oxygen to the cells.
4
Mitochondria in the cells use them in respiration to release energy.
5
The carbon dioxide made is carried back to the lungs and breathed out.

Section 5 of 9Respiration and heat

1
In every energy transfer, some energy is changed to heat energy.
2
In respiration, chemical energy stored in glucose is transferred to other substances so the cells can use it.
3
Some of the energy becomes heat, so respiring cells are a little warmer than their surroundings.
4
The body of a person is warmer than the chair on which the person sits, because respiration in body cells releases heat.

Section 6 of 9Respiration in peas

  • All living things need energy, so all living things respire, including seeds.
  • Seeds respire especially quickly when germinating, because they need a lot of energy.
  • Seeds start to germinate if they are soaked in water for about an hour.
  • Method:
1
Put live, germinating peas in one flask and dead peas in another flask.
2
Make everything else the same in both flasks, with cotton wool in the top and insulating material around the outside.
3
Measure the temperature in each flask and record it in a results table.
4
Measure and record the temperature at regular intervals, for example every hour.
5
Plot a line graph with time on the horizontal axis and temperature on the vertical axis.
Respiration in peas
The variable changed is whether the peas are alive, the variable measured is the temperature, and the other variables are kept the same.
The live peas become warmer than the dead peas, because they respire and release heat.

Section 7 of 9Respiration and breathing

Respiration and breathing
Respiration happens in all living cells all the time, including the cells of plants.
Breathing moves air in and out of the lungs and is not the same as respiration.

Section 8 of 9Key terms

TermMeaning
RespirationThe chemical reaction in cells that releases energy from food.
Aerobic respirationRespiration that uses oxygen: glucose + oxygen → carbon dioxide + water.
GlucoseA sugar made from carbohydrates that cells use as an energy store.
MitochondriaTiny structures in cells that release energy from glucose.
ReactantA substance that is used up in a chemical reaction.
ProductA substance made in a chemical reaction.

Section 9 of 9Exam technique

1
Saying respiration is breathing — respiration is the reaction that releases energy in cells.
2
Saying mitochondria make energy — they release energy from glucose.
3
Saying only animals respire — plants and seeds respire too.
4
Writing oxygen as a product of respiration — oxygen is a reactant, and carbon dioxide and water are the products.
5
Saying respiration only happens during exercise — it happens all the time in every living cell.

Last updated: