Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
UNIT 1 : RESPIRATION
1.1 The human respiratory system
What is breathing? –
We have to remember all the parts involve in this system.
Mechanisms of breathing
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
Fill up the blanks with correct answers.
Draw the flowchart of the mechanism
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
1.2 Gas exchange
We must know “How gas exchange takes place?”
- Movement and Exchange of TWO main gases in our body
What are those?:
- The gases always flow from an area of HIGHER CONCENTRATION to LOWER
CONCENTRATION.
- the exchange happens in our AIR SAC @ ALVEOLI
Now lets go to the mechanisms
1. The air inhaled into the alveolus has a
higher concentration of oxygen compared
to the concentration of oxygen in the blood.
Therefore, oxygen will diffuse through the
wall of the alveolus into the walls of the
capillaries and into the blood.
2. In red blood cells, there is a dark red-coloured
compound known as haemoglobin. Haemoglobin
will combine with oxygen to form
oxyhaemoglobin which is an unstable compound
and bright red in colour.
Haemoglobin + oxygen ⇌ oxyhaemoglobin
3. Blood with oxyhaemoglobin is
transported from the lungs to the heart
and pumped to the other parts of the body.
4 .When the blood reaches the area around the body
cells that has a low concentration of oxygen, the
oxyhaemoglobin being an unstable compound will
decompose to release oxygen molecules and
change back into haemoglobin.
5. In the body cells, the diffused oxygen oxidises
glucose molecules into carbon dioxide, water and
energy through the process of cellular respiration as
summarised in the following chemical equation.
Glucose + oxygen → carbon dioxide + water + energy
Oxyhaemoglobin → haemoglobin + oxygen
6. Carbon dioxide released by the cells diffuses
into the blood capillaries and is transported to the
alveolus to be removed during exhalation.
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
1. On your diagram, draw a green arrow to show how oxygen diffuses from the
air into the blood.
2. How many cells does the oxygen move through, as it leaves the blood and goes
into the air?
3. On your diagram, draw a blue arrow to show how carbon dioxide diffuses from
the blood into the air.
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
We also need to know how Alveolar structure will help in gas
exchange.
Why? – to increase the efficiency and maximize the exchange of
gases in the human body.
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
6
Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
1.3 Breathing
What is breathing:
How it works:
Inhalation (Breathe IN)
When you inhale,
• intercostal muscles contract and pull the rib cage upwards and outwards
• diaphragm muscles contract and pull the diaphragm to descend and become flat.
• movements of the rib cage and diaphragm make the thoracic cavity bigger and
cause air pressure in the thoracic cavity to decrease.
• the higher air pressure outside forces air to enter the lungs
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
4. Exhalation (Breathe OUT)
When you exhale,
• intercostal muscles relax and the rib cage moves downwards and inwards
• diaphragm muscles relax and curve upwards.
• movements of the rib cage and diaphragm make the thoracic cavity smaller and
cause the air pressure in the thoracic cavity to increase.
• the higher air pressure in the lungs pushes the air out
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
1.4 Respiration
•
Our body need energy to do anything.
•
•
•
Glucose is the main supplier for energy and it is the energy store.
Energy in glucose is locked inside.
Glucose come from carbohydrates goes into our blood.
•
Blood delivers it to every cells and cells uses glucose to get energy they
need.
How energy released from glucose
•
Before our cells can use the energy, it has to relased by the glucose first.
Who will do this work? → Mitochondria
•
Most cells has mitochondria inside them
•
•
It relase energy from glucose for the cells to use it
Mitochondria do aerobic respespiration
Aerobic respiration : uses oxygen and produce energy
Anaerobic respiration : uses energy and produce oxygen
Respiration and heat production
•
Chemical energy stored in glucose is transferred to other
•
•
substances, so that cells can use it.
In this process, some of the energy is changed to heat energy.
•
So respiring cells get a little bit warmer than their surroundings.
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
1.5 Blood
Every cell in your body needs a good supply of glucose and oxygen, and the carbon
dioxide and water that the cell makes must be taken away.
The delivery and removal is done by the blood.
Lets discuss about blood
Blood plasma
•
liquid part of the blood
•
•
mostly water
very pale yellow color
•
contains many other substances, which transported from digestive system to
all cells
Red blood cells
•
•
Floats in blood
Do not have nuclei and mitochondria
•
They have only red pigments : Haemoglobin
Why don’t they have nuclei or mitochondria?
Scientists think that not having a nucleus makes more space for haemoglobin. They
also think that not having mitochondria stops the red blood cells from using up all
the oxygen for themselves, instead of delivering it elsewhere.
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Teacher Mahen
Name:
Date: 29 September 2022
Lesson 1 Science IGCSE L8
White blood cells
Some bigger size than red blood cells
Have nuclei
Now lets see what this white blood cells will do?
Some bad fellas will come into our body to harm us : Bacteria and Viruses
The fellas are called Pathogens
WBC will fight these pathogens
WBC will change shape (like a eating-monster) to catch pathogens
WBC will release some chemicals that kill and digest the bacterium : Phagocytosis
or Antibodies
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Teacher Mahen