transport across cell membrane Flashcards
the cell membrane consists of ____
phospholipids and proteins
(is selectively permeable)
3 parts of cell membrane
phospholipid bilayer
receptor protein
protein with pore
PRACTICE LABELLING ERINA
describe the cell membranes permeability
the cell membrane is selectively permeable as only small molecules/ions can pass through it
1) the cell membrane separates ________
2) the proteins on the surface of the membrane act as ____
1) separates the cell contents from its surrounding
2) receptor sites for antibodies and hormones
what’s the function of channels or pores in the cell membrane
they allow certain molecules and ions to pass through the membrane, depending on size and relative concentrations inside and outside the cell
define passive transport
2 examples of this?
passive transport occurs down a concentration gradient and doesn’t require energy
examples: diffusion and osmosis
define diffusion
diffusion in cells is the movement of molecules down a concentration gradient, from a higher to lower concentration
examples of substances that diffuse across a cell membrane (4)
glucose
amino acids
oxygen
carbon dioxide
what is diffusion important for in humans (3)
1) gas exchange in lungs
2) absorption of digested food in small intestine
3) reabsorption of water in large intestine
READ NOTES ABOUT WHERE THIS OCCURS e.g. from alveoli to capillaries
what is diffusion important for in plants (2)
1) gas exchange in leaf - through pores called stomata
2) absorption of water - from soil water through root hairs
what is osmosis
osmosis is the movement of water molecules from a higher water concentration to a lower water concentration through a selectively permeable membrane
1) what happens to animal cells in osmosis
2) what happens to plant cells
1) animal cells can burst or shrink
2) plant cells can become turgid or plasmolysed
1) when do animal cells burst due to osmosis
2) when do they shrink
1) in pure water
2) in concentrated solution of sugar or salt
why do plant cells become turgid but do not burst in pure water?
the cell wall prevents them from bursting
why do plant cells become plasmolysed in concentrated solutions of sugar or salt
water moves out of the cell by osmosis and cell becomes plasmolysed
LOOK AT DIAGRAMS ERINA
