Thursday, March 25, 2010

[Biology Form 4] Movement Across The Plasma Membrane

1. Three types of passive transport.
  • Simple diffusion
  • Osmosis
  • Facilitated diffusion

  • Active Transport

  • Passive Transport
    • Simple Diffusion: The movement of molecules from region of high concentration to low concentration.
    • The movement of molecules from region of high concentration to a region of low concentration with the help of carrier proteins.
    • Osmosis: The movement of water molecules from dilute solution to a concentrated solution across a Semi permeable membrane.

The figure below shows the model of the plasma membrane. Label L, M, N, and O shows four types of nutrients. P1, P2 and P3 show three types of protein.

(i) Name the processes labelled L, M, N, O.
L : Simple diffusion
M : Fasilitated diffusion
N : Fasilitated diffusion
O : Active transport

(ii) Name the protein labelled P1, P2 and P3.
P1 : Pore protein
P2 : Carrier protein
P3 : Carrier protein

(iii) State two characteristics of the molecules that are transported into the cell by process L.
1. Small
2. Soluble in lipid

4. The figure shows a model of the active transport system that depends on several carrier proteins found in the cell membrane.

(i) Explain what do you understand by active transport.
Movement of particles across the plasma membrane
  1. by carrier proteins,
  2. against the concentration gradient and
  3. requires energy.

(ii) Give an example of active transport in plants.
Ion or mineral uptake by plant root hairs.

(iii) State two differences between active transport and diffusion.
Any two differences – energy, gradient concentration, living membrane.

5. The table below shows the effect of hypotonic, isotonic and hypertonic solution on spinach strips, red blood cells and plant cells.

Hypotonic solution

Isotonic solution

Hypertonic solution

Spinach strip in distill water

· Distill water is hypotonic compared to the cell sap.

· Water enters into spinach cell through cut surface by osmosis . Epidermis is water proof.

· The epidermis layer curved inward.

Spinach strip in 5% sucrose solution

· The rate of water entering and leaving the spinach cell through semi permeable mambrane

is the same.

· The shape of spinach strip remains the same

Spinach strip in 30% sucrose solution

Red blood cell in distill water.

Red blood cell in isotonic solution

Red blood in 30% sodium chloride solution

Plant cell in distill water

Plant cell in isotonic solution

Plant cells in 30% sucrose solution


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