transport across cell membranes Flashcards
e.g. passive transport, diffusion, osmosis, plasmolysed cells
the cell membrane is composed of
phospholipids and proteins
the cell membrane is
selectively permeable
a difference in concentration of a substance is a
concentration gradient
passive transport……. require energy
doesn’t
passive transport is the movement of
molecules down a concentration gradient from high water concentration to low water concentration
examples of passive transport include
diffusion and osmosis
diffusion is the movement of
molecules down a concentration gradient from high water concentration to low water concentration
examples of substances that enter most cells by diffusion are
oxygen, glucose and amino acids
examples of a substance that leave most cells by diffusion is
carbon dioxide
diffusion is important to cells because
it helps provide the cell with raw materials and helps to remove waste products
osmosis is the movement of
water molecules from a high water concentration to low water concentration through a selectively permeable membrane
an animal cell placed in a solution with a higher water concentration than inside the cell will
gain water by osmosis and could burst
an animal cell placed in a solution with a lower water concentration that inside the cell will
lose water by osmosis and could shrink
a plant cell placed in a solution with a higher water concentration than inside the cell will
gain water by osmosis and become turgid
a plant cell placed in a solution with a lower water concentration that inside the cell will
lose water by osmosis and become plasmolysed
turgid is when
the vacuole in a cell has swollen due to water gain and pressures the cytoplasm and cell membrane agaisnt the cell wall
plasmolysed is when
the vacuole in a cell has shrunk due to water loss, causing the cell membrane to pull away from the cell wall
active transport is the movement of
molecules against a concentration gradient from low water concentration to high water concentration
active transport ……….. require energy
does
the energy required by active transport is provided by
ATP
active transport needs energy so it can
allow membrane proteins to move molecules and ions against the concentration gradient
