Homeostasis

Mrs. Harlin

1.2.1

Explain how homeostasis is maintained in the cell and within an organism in various environments (including temperature and pH).

HomeostasisHomeostasis is a state of maintaining an

internal balance within cells.Cells use buffers to regulate cell pH.Cells respond to maintain temperature, glucose

levels, and water balance.

Plasma MembraneThe plasma membrane is responsible for

maintaining homeostasis.

1. Passive TransportRequires no

energy to move across a membrane.

Goes with the concentration gradient.

DiffusionThe movement of a substance from an area of

high concentration to an area of low concentration.

Diffusionhttp://highered.mcgraw-hill.com/sites/

0072495855/student_view0/chapter2/animation__how_diffusion_works.html

OsmosisDiffusion of water across a selectively

permeable membrane.

Osmosishttp://highered.mcgraw-hill.com/sites/

0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Scenario 1If the concentration of substances in the

solution is the same as inside the cell. Water constantly moves in and out of the cell.No shape change.Equilibrium is reached.

Scenario 2Higher concentration inside the cell. Water moves IN the cell in attempt to reduce

the concentration- swelling

Animal cells may burst if too much water comes in! Called lysis.

Plant cells will only become more and more firm.

Scenario 3Higher concentration outside the cell than

inside.Water will move OUT in attempt to reduce

the outside concentration.Cells will shrivel and shrink. Plants will wilt.Ex: When you put salt on a slug, it shrinks

and dies.

2. Active TransportRequires energy. Uses the carrier proteins

to change shape in order pass a particle.

Substances can either go with or against the concentration gradient.

Examples- Endocytosis, exocytosis, Sodium-Potassium Pump

Sodium-Potassium Pumphttp://highered.mcgraw-hill.com/sites/

0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Facilitated DiffusionType of passive or

active transport across a membrane with using a transport protein.