MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE. The necessity for movement of substances across the plasma membrane. All movement of substances go through the cell membrane , which is also known as the plasma membrane .
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Movement of substances out of the cell
Movement of substances into the cell
Figure 3.1: Movement of substances in and out of the cell
3. The phospholipid bilayer is permeable to:
a) Small non-polar (hydrophobic) molecules that are lipid-soluble, such as fatty acids, glycerol, steroid, vitamin A, D, E and K.
4. The phospholipid bilayer is not permeable to:
a) Large polar molecule, that are not soluble in lipid, such as glucose, amino acids, nucleic acids and polysaccharides.
1. Solute move across the plasma membrane by two main process:
3. Osmosis is the special name given to simple diffusion of water molecules through a semi-permeable membrane.
Concentration gradient = difference in concentration of a particular substance in one region compared to another region
Potassium manganate (vii) crystals
b) The molecules diffuse out along the concentration gradient in all direction.
a) The crystals starts to dissolve, forming a region of high concentration of solute molecules.
A sample experiment to illustrate the physical process of diffusion
ii. Pore proteins open up pores or channel across the membrane to allow entry or exit.
Remains of cell surface membrane
Crenation: Red blood cell shrinks and turns ’spiky’
Red blood cell
Haemolysis: Red blood cell finally burst
CRENATION AND HAEMOLYSIS OF RED BLOOD CELL
Red blood cell
GASEOUS EXHANGE BY SIMPLE DIFFUSION IN THE ALVEOLUS