1. Active transport
Lesson Objectives
• All will be able to define active transport
• Most will be able to explain in detail how
active transport happens
• Some will be able to give example and
suggest reasons why active transport is
important
2. Draw an animal and plant cell
(remember to label all the different organelles!)
3. Movement in and out of cells
How do substances get in and out of cells?
4. True or false?
1. Osmosis involves the movement of water
2. Diffusion requires energy
3. Diffusion occurs in liquids, solids and gases
4. Osmosis requires a semi permeable membrane
5. All molecules can pass through a semi permeable
membrane
6. A hypotonic solution is a strong solution
7. A hypertonic solution is a strong solution
8. If water moves into a plant cell it will burst
9. Water is produced by actively respiring cells
10. Osmosis and diffusion will continue until dynamic
equilibrium is reached
5.
6.
7. Jot down a quick definition of
osmosis and diffusion
8. Active transport
• Another way of getting
molecules into cells
• Animal and plant cells cannot
rely on diffusion alone to get
the molecules they need.
• What if they need molecules
that are in a higher
concentration inside the cell
than outside?
9. What is active transport?
During active transport, protein
carriers in the cell membrane ‘pick
up’ particles and move them against
the concentration gradient.
As the name suggests, active transport
requires energy from the cell, which is
made available by respiration.
10.
11. Key words: Active
What is needed for transport; Energy; Carrier
protein
active transport?
• Unlike osmosis and diffusion energy and a
carrier protein is needed to transport
molecules across the cell membrane
12. Active transport
• Stick the pictures showing active transport
in your book, label and explain what is
happening at each stage:
• Key words:
– Carrier protein, energy (ATP), membrane,
high concentration, low concentration,
mitochondria, against concentration gradient
13. Hwk: Active transport
• How do animals and plants use active
transport?
• Use text books to research ways which
active transport is used
14. Diffusion, Osmosis and Active
Transport compared
Active
Diffusion Osmosis Transport
Movement by
concentration
Molecule
transported
Energy used
Carrier protein
15. Diffusion, Osmosis and Active
Transport compared
Active
Diffusion Osmosis Transport
Movement by
concentration From high to low From high to low From low to high
Molecule
transported Any Water Any
Energy used No No Yes
Carrier protein No No Yes
Editor's Notes
Teacher notes This illustration contains several discussion points relating to movement in and out of cells, including: Rats escaping from prison This section of the illustration represents diffusion. The rats are running from the prison through the gaps in the fence (representing a partially-permeable membrane). The rats are running from an area of high concentration (inside the prison) to an area of low concentration (outside the prison), i.e. along a concentration gradient. Prison guard watering wilted flowers This section of the illustration represents osmosis. The water being sprayed from the hosepipe represents water particles moving from an area of high concentration to an area of low concentration (the parched soil), i.e. along a concentration gradient. Objects being passed through the wire fence This section of the illustration represents active transport. The bags represent cellular substances and the fence represents a partially-permeable membrane. The bags are being passed from an area of low concentration (outside the prison) to high concentration (inside the prison), i.e. against a concentration gradient.
Teacher notes This activity could be used as a starter exercise to work on diffusion.
Teacher notes This activity could be used as a starter exercise to work on osmosis.
What if you need to transport molecules against the concentration gradient – i.e. from a high to low conc.? Can’t use diffusion then! When would you need this for? In plants: Plants need mineral salts (eg nitrates) for making proteins and growth. Nitrates are at a higher concentration inside the root cells than they are when dissolved in the water around the soil particles. In humans: Active transport takes place during digestion of food in the ileum (small intestine). After food has been absorbed by the villi for some time, the concentration of food molecules inside the villi increases, making it impossible for more food to diffuse into the villi. So simple sugars, amino acids, minerals and vitamins are actively absorbed into the villi, from an area of lower to an area of higher concentration.
Teacher notes This two-stage animation shows how substances are transported across the cell membrane. Suitable prompts could include: Start: What kind of molecules are transported by active transport? (e.g. sodium and potassium in muscle cells) Stage 1: Which process provides the energy for active transport? (respiration)
Record the definition of diffusion in your own words. Make sure you include the above.
