Basic 9 · Science · Human Body Systems
Respiration and Breathing
In this topic you will explain the concept of respiration, and show how the respiratory and circulatory systems complement each other.
By the end of these notes you should be able to:
- Distinguish respiration from breathing
- Describe the respiratory system
- Explain how the respiratory and circulatory systems work together
What you already know
- Circulatory system
Copy everything that has a blue line on its left into your notebook. The other parts are for reading.
Lesson 1
- Strand
- Systems
- Sub-strand
- Human Body Systems
- Indicator
- B9.3.1.1.2 – Explain the concept of respiration and show how the respiratory and circulatory systems complement each other
Introduction
You eat food to have energy. Respiration is the process that releases that energy in each of your cells.
1. Respiration and Breathing
| Feature | Respiration | Breathing |
|---|---|---|
| what it is | chemical release of energy | movement of air in and out |
| where | in all cells | in the lungs |
| type | chemical | physical |
2. Aerobic Respiration
Aerobic respiration: Releasing energy from food using oxygen.
Most energy is released through aerobic respiration, in the mitochondria of cells. The word equation is: glucose + oxygen → carbon dioxide + water + energy. The energy is stored in a molecule called ATP, which cells use for movement, growth and keeping warm. This takes place all the time, in all living cells, including those of plants.
3. Anaerobic Respiration
Anaerobic respiration: Releasing energy without oxygen.
| Organism | Equation | Use |
|---|---|---|
| humans | glucose → lactic acid + energy | short bursts of hard exercise |
| yeast | glucose → alcohol + carbon dioxide + energy | bread, palm wine, pito |
During hard exercise, muscles may not get enough oxygen, so they switch to anaerobic respiration. Lactic acid builds up, and this causes tired, aching muscles. Anaerobic respiration releases less energy than aerobic. After exercise, you keep breathing hard to repay the oxygen debt.
4. Fermentation in Ghana
Yeast respires without oxygen, producing alcohol and carbon dioxide. This is fermentation. It is used in brewing pito and in making palm wine, as well as in the production of akpeteshie. Bread rises because of the carbon dioxide from yeast. Kenkey and koko also ferment, but mainly through lactic acid bacteria, which give a sour taste. Understanding respiration explains these familiar foods.
5. Evidence for Respiration
Testing for carbon dioxide
How can you show that exhaled air contains more carbon dioxide than inhaled air?
- Pass exhaled air through limewater.
- It turns milky quickly.
- Inhaled air turns it milky very slowly.
Answer: Exhaled air contains more carbon dioxide
Limewater turns milky in the presence of carbon dioxide. Germinating seeds can also be shown to give out heat, which is further evidence that they respire.
New words
- respiration
- Releasing energy from food.
- aerobic
- Using oxygen.
- anaerobic
- Without oxygen.
- fermentation
- Anaerobic respiration by yeast.
Summary
- Respiration releases energy, and breathing moves air.
- Aerobic respiration uses oxygen.
- Anaerobic respiration gives lactic acid or alcohol.
Class activity: Yeast Balloon
- Mix yeast, sugar and warm water in a bottle.
- Put a balloon over the top.
- Observe and explain the change.
You need: Plastic-bottle lung model, Mammalian heart model, Printed cardio-respiratory diagram
Exercises
Answer in your exercise book first, then check your answers.
1. Aerobic respiration uses…
- A. oxygen
- B. salt
- C. nitrogen
- D. sand
Show answer
Answer: oxygenTerm.2. Yeast produces…
- A. alcohol and carbon dioxide
- B. lactic acid only
- C. oxygen
- D. protein
Show answer
Answer: alcohol and carbon dioxideFermentation.3. Plants respire.
- A. True
- B. False
Show answer
Answer: TrueAll cells.4. Limewater turns milky with ______ dioxide.
Show answer
Answer: carbonTest.5. State one difference between respiration and breathing.
Show answer
Answer: Respiration is chemical, and breathing is physical.Comparison.6. Why do muscles ache after hard exercise?
Show answer
Answer: Anaerobic respiration produces lactic acid.Explanation.
Lesson 2
- Strand
- Systems
- Sub-strand
- Human Body Systems
- Indicator
- B9.3.1.1.2 – Explain the concept of respiration and show how the respiratory and circulatory systems complement each other
Introduction
You take thousands of breaths a day without thinking. Each one depends on a beautifully designed system.
1. Parts of the System
| Part | Function |
|---|---|
| nose | filters and warms air |
| trachea | carries air to the lungs |
| bronchi | branch into each lung |
| bronchioles | smaller tubes |
| alveoli | exchange gases |
| diaphragm | muscle that helps breathing |
| ribs | protect the lungs and aid breathing |
2. How Breathing Works
| Stage | Diaphragm | Ribs | Lung volume |
|---|---|---|---|
| inhaling | contracts and flattens | move up and out | increases |
| exhaling | relaxes and domes | move down and in | decreases |
When the chest cavity gets larger, the pressure falls, and air flows in. When it gets smaller, air is pushed out. You can feel your ribs rise when you breathe in deeply.
3. Alveoli
The lungs contain hundreds of millions of tiny air sacs called alveoli. Together, they have a huge surface area, about the size of a tennis court. They have very thin, moist walls and a rich supply of capillaries. Oxygen diffuses into the blood, and carbon dioxide diffuses out. This process is called gaseous exchange.
| Gas | Inhaled | Exhaled |
|---|---|---|
| oxygen | about 21% | about 16% |
| carbon dioxide | about 0.04% | about 4% |
| nitrogen | about 78% | about 78% |
4. Health Challenges
| Disease | Cause | Prevention |
|---|---|---|
| asthma | narrowed airways | avoid triggers, inhalers |
| tuberculosis | bacteria | vaccination, treatment |
| pneumonia | infection | vaccination, clean air |
| lung cancer | mostly smoking | do not smoke |
| COVID-19 | virus | vaccination, hygiene |
5. Protecting Your Lungs
Smoking damages alveoli, cilia and the blood vessels. Second-hand smoke harms those nearby too. Smoke from wood fires and burning rubbish can also hurt the lungs. Dust in mines and on building sites is harmful, so masks are needed. Exercise helps lungs to work well. Tuberculosis, which is spread by coughing, is treatable, and free treatment is available in Ghana. Anyone with a cough that lasts more than two weeks should see a doctor.
New words
- alveoli
- Tiny air sacs in the lungs.
- diaphragm
- A muscle below the lungs.
- diffusion
- Movement from high to low concentration.
- trachea
- The windpipe.
Summary
- Air travels from the nose to the alveoli.
- The diaphragm and ribs move air in and out.
- Gases are exchanged in the alveoli.
Class activity: Lung Model
- Make a model with a bottle and balloons.
- Pull the base to show breathing.
- Explain how it works.
You need: Plastic-bottle lung model, Mammalian heart model, Printed cardio-respiratory diagram
Exercises
Answer in your exercise book first, then check your answers.
1. Gases are exchanged in the…
- A. alveoli
- B. trachea
- C. ribs
- D. nose
Show answer
Answer: alveoliFunction.2. When you inhale, the diaphragm…
- A. contracts and flattens
- B. relaxes
- C. disappears
- D. rises
Show answer
Answer: contracts and flattensBreathing.3. Exhaled air has more carbon dioxide than inhaled air.
- A. True
- B. False
Show answer
Answer: TrueRespiration.4. The windpipe is also called the ______.
Show answer
Answer: tracheaTerm.5. State three features of alveoli.
Show answer
Answer: Large surface area, thin walls and many capillaries.Features.6. Why is smoking harmful to the lungs?
Show answer
Answer: It damages alveoli and cilia, and it can cause cancer.Health.
Lesson 3
- Strand
- Systems
- Sub-strand
- Human Body Systems
- Indicator
- B9.3.1.1.2 – Explain the concept of respiration and show how the respiratory and circulatory systems complement each other
Introduction
Your lungs bring in oxygen, but your heart delivers it. Neither can work without the other.
1. Working Together
- Air enters the alveoli.
- Oxygen diffuses into capillaries.
- Red blood cells carry it to the heart.
- The heart pumps it to the body.
- Cells use oxygen for respiration.
- Carbon dioxide returns in the blood.
- The heart pumps blood to the lungs.
- Carbon dioxide leaves through the alveoli.
2. During Exercise
| Change | Reason |
|---|---|
| faster breathing | takes in more oxygen |
| faster heartbeat | delivers more oxygen |
| sweating | cools the body |
| red skin | more blood near the surface |
Muscles need more energy during exercise, so they need more oxygen and glucose. The brain senses a rise in carbon dioxide and signals the heart and lungs to work harder. After exercise, breathing and heart rate return gradually to normal. The faster this recovery, the fitter a person is.
Reading data
A runner's pulse goes from 70 to 150 beats per minute. Find the increase, and the percentage increase.
- Increase: 150 − 70 = 80.
- Percentage: 80/70 × 100.
Answer: An increase of 80 beats, or about 114%
3. Oxygen Transport
Haemoglobin in red cells picks up oxygen in the lungs, where there is plenty of it. It releases it in the tissues, where oxygen is low. Carbon monoxide binds to haemoglobin much more strongly than oxygen. That is why carbon monoxide is so dangerous. It blocks oxygen transport, even if there is air to breathe. At high altitudes, there is less oxygen, and the body makes more red cells over time.
4. When the Link Fails
| Problem | Effect on both systems |
|---|---|
| anaemia | less oxygen carried, so breathlessness |
| heart failure | fluid in lungs |
| smoking | damages lungs and arteries |
| lung disease | heart must work harder |
5. Staying Fit
Aerobic exercise such as walking, running, football and dancing strengthens both the heart and the lungs. Aim for at least an hour of activity a day at your age. Walking to school counts. Avoid smoking, and remember that vaping is also harmful. Good health today protects you throughout your life.
New words
- complement
- To work together with something.
- recovery
- A return to the normal state.
- oxygen transport
- Carrying oxygen in the blood.
- fitness
- The body's ability to do activity.
Summary
- The lungs and heart work as a team.
- Exercise increases breathing and heart rate.
- Harm to one system harms the other.
Class activity: Fitness Test
- Measure resting pulse and breathing rates.
- Exercise for two minutes.
- Record the recovery time.
You need: Plastic-bottle lung model, Mammalian heart model, Printed cardio-respiratory diagram
Exercises
Answer in your exercise book first, then check your answers.
1. Oxygen is carried by…
- A. red blood cells
- B. platelets
- C. plasma only
- D. nerves
Show answer
Answer: red blood cellsTransport.2. During exercise, the heart rate…
- A. increases
- B. stops
- C. falls
- D. stays the same
Show answer
Answer: increasesExercise.3. Carbon monoxide blocks oxygen transport.
- A. True
- B. False
Show answer
Answer: TrueSafety.4. Fast recovery after exercise shows good ______.
Show answer
Answer: fitnessTerm.5. Describe how oxygen reaches the muscles.
Show answer
Answer: From the alveoli to the blood, pumped by the heart to the muscles.Pathway.6. Why do you breathe faster in exercise?
Show answer
Answer: Muscles need more oxygen, and more carbon dioxide must be removed.Reason.
Homework
- Draw a flow chart showing how oxygen moves from the air to a muscle.