Osmosis

9.1 PLASMA MEMBRANE

I. every(prenominal) stalls must maintain homeostasis in straddle to live.

- they do this by controlling what materials can enter and leave

II. All cells ache a plasma tissue layer that is SELECTIVELY porous - this only allows for specific things to enter and leave the cell

A. Selective permeableness is achieved by the structure of the plasma tissue layer (fig.9.3, pg 220)

1. The cell membrane is composed of 2 layers of PHOSPHOLIPIDS -

phospho = phosphate lipid = fat

· referred to as the phospholipid bilayer

· phospholipids have polar, water-soluble heads attached to long, nonpolar tails.

· The phosphate heads are on the away(p) and the internal of the cell

· The nonpolar tails lie inside the bilayer

B. The phospholipids can move sideways through their layer - this allows the membrane to behave like a fluid, it can flow.

· FLUID MOSIAC MODEL

· new(prenominal) organelles surrounded by a fluid mosiac bilayer include: the nucleus, vacuoles, mitochondria and chloroplasts.

C. end-to-end the membrane, proteins are found between the phospholipid molecules

· these proteins carry out close to of the functions of the p.



membrane

- they determine which particles can pass across the membrane

- some proteins correspond as enzymes (speed up reactions or processes)

- other proteins act as markers that are recognized by chemicals from both the inside and outside of the cell. Some of these markers are involved in fighting disease

9.2 cellular TRANSPORT - the moving of particles across a cellular membrane

I. Brownian thrust (Robert Brown)

- random movement of particles

II. Diffusion - movement of particles from an area of utmost concentration to an area of low

concentration

· tries to balance the concentrations in and outside of the cell - put into equilibrium

· differences in concentrations across a...

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