(how it works)
study of biological function
ability to maintain constant internal balance regardless of the environment (steady state)
-occurs at all levels
-cells exist in fluid environment
-cells must keep cytoplasm
4 factors decide what go through (homeostasis)
-dissolves in water
-conditions inside & outside the cell
At cellular level, homeostasis depends on movement....
in & out of the cell
-all things must pass through cell membrane
can pass through
can't pass through
cell membrane is....
selectively (chemical) and semi-permeable (size, charge)
energy is not required for substances to pass in and out of the cell
moving particles from high to low concentration
-possible because of kinetic energy (energy of motion) atoms move in a straight line
-atoms keep moving til their spread evenly
Factors that affect rate of diffusion
movement of water (diffusion)
-call can't control osmosis - it moves on it's own
some inside & out
-no net water movement
higher outside the cell
-water moves out
lower outside the cell
-water moves in
pressure exerted by cell contents against the cell wall
-helps support soft tissue
loss of tugor pressure
-causes cell contents to shrink away from the cell
bursting of cell from water pressure inside
energy required, low to high.
moves molecules and particles into the cell
-phagocytosis - cytoplasm surrounds the particles
-pinocytosis-collects on the cell membrane and pinches inward
large particles shipped out by golgi apparatus
Passive & active transport...
of materials through the cell membrane are ways cell maintains homeostasis
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