Download 3 Transport in cells

3 Transport in cells
Prior knowledge catch-up
Previously you could have learnt:
•
understand about diffusion in terms of the particle model
•
that breathing is the movement of air in and out of the lungs
•
that plants gain mineral nutrients and water from the soil via their roots.
Key points to remember:
Diffusion is the spreading out of particles from an area of high concentration to an area of low
concentration. When you turn on a gas tap on at school or spray deodorant under your arms it is at a
high concentration. The particles of gas and deodorant will spread out from this area into the room.
This process is how you can smell the gas across the room or your friend’s deodorant if you sit next
to them.
Only gases and liquids can diffuse. Particles in solids are fixed in position and cannot flow. This is
explained by the particle model.
Figure 3.1 Particles in a solid, a liquid and a gas
Breathing is called ventilation. Breathing in is called inhalation and breathing out is called exhalation.
(Respiration is a chemical reaction in which the energy your body needs is released from glucose in
your food. This is nothing to do with the process of breathing.)
When you breathe in your intercostal muscles contract, which expands your ribcage. Your
diaphragm contracts, which also increases the volume of your chest. This makes the pressure inside
your lungs lower and so air is pulled into your lungs. When you breathe out your intercostal muscles
relax and your ribcage contracts. Your diaphragm also relaxes, which decreases the volume of your
lungs. This makes the pressure inside your lungs increase and so air is pushed out of your lungs.
© Hodder & Stoughton Limited 2016
3 Transport in cells
Prior knowledge catch-up
Photosynthesis is a process that occurs in all green parts of plants (thin stems and leaves). The word
equation for photosynthesis is:
The cells of plant roots have hair-like structures that stick out from them into the soil. These cells are
called root hair cells. These cell increase the area of the plant that can absorb water and mineral
from the soil. Water is needed for photosynthesis and minerals keep the plant healthy.
© Hodder & Stoughton Limited 2016
3 Transport in cells
Prior knowledge catch-up
Student worksheet
Questions
1 What is diffusion?
2 In which substances can diffusion happen?
a Solids only
b Solids, liquids and gases
c
Gases and liquids
3 What is an everyday example of diffusion?
4 Join up the correct word to its definition.
Inhalation
Breathing in
carbon dioxide + water → glucose + oxygen
Photosynthesis
glucose + oxygen → carbon dioxide + water
Breathing out
5 What is the scientific name for breathing out?
6 What happens to your intercostal muscles when you breathe in?
7 What happens to your diaphragm when you breathe out?
8 In which parts of plants does photosynthesis occur?
9 What two substances do root hair cells absorb?
10 What adaptation do root hair cells have?
Now try and complete the questions from the beginning of Chapter 3 from the book:
1 Name the specialised cell that helps plants to absorb water.
2 Describe the process of diffusion.
3 Explain why breathing and respiration are not the same thing.
© Hodder & Stoughton Limited 2016