Membranes. Structure and Function

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Slide 1

Cell Membranes

Structure and Function

Slide 2

Animal Cell Membrane

Slide 3

Semi-permeable Membranes

Lipid membranes are semi-permeable, also called selectively permeable

Water moves across the membrane freely

Ions (charged particles) do not move across the membrane freely

Many large molecules do not move across the membrane freely

Slide 4

Passive Transport

Diffusion – the movement of substances from an area of higher concentration to an area of lower concentration

Osmosis – the movement of water from an area of higher water content to an area of lower water content

Slide 5

Active Transport

The movement of a substance against the concentration gradient (from lower concentration to higher concentration

Active transport requires the use of energy

Slide 6

Membrane proteins play an important role in passive and active transport

Slide 7

Very large molecules may be taken in by endocytosis

Slide 8

Exocytosis secretes substances