3. Movement in and out of cells Flashcards
Diffusion
the net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement
energy for diffusion comes from and movement of substances into and out of cells
the kinetic energy of random movement of molecules and ions
some substances move into and out of cells by diffusion through the cell membrane
importance of diffusion of gases and
solutes in living organisms
obtain many of their requirements
get rid of many of their waste products
carry out gas exchange for respiration
factors that influence diffusion
surface area
temperature
concentration gradient
distance
osmosis
the net movement of
water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
effects on plant cells of immersing
them in solutions of different concentrations
high concentration- water diffuses out of cell. vacuole and cytoplasm shrink and the cell membrane pulls away from cell. it becomes flaccid and may become plasmolysed
low concentration- water diffuses into the cell. vacuole gets bigger, pushing the cell membrane against the cell wall.
effects on animal cells of immersing
them in solutions of different concentrations
high concentration- water diffuses out of cell. vacuole and cytoplasm shrink so the cell gets smaller.
low concentration- water diffuses into the cell. cell swells, cell membrane stretches and the cell gets bigger until eventually the strain is too much and the cell bursts.
role of water as a solvent
digestion- food and enzymes in alimentary canal
excretion- kidneys excrete urea dissolved in water, to form urine
substances are transported around the body dissolved in water in blood plasma
plants are supported by
the pressure of water inside the cells pressing outwards on the cell wall
active transport
the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration
importance of active transport
root hair cells take in nitrate ions from soil. concentration of nitrate ions inside the cell is higher than the concentration in cell. diffusion gradient is out of cell and into soil.
protein carriers
in cell membranes, change shape and move molecules or ions across a membrane during active transport using energy from respiration
