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The Cell in its Environment. Cellular Biology Part 2 Mr. N ajera. Objectives. Describe how most small molecules cross the cell membrane. Explain why osmosis is important to cells Tell the difference between passive and active transport. . Selectively Permeable .
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The Cell in its Environment Cellular Biology Part 2 Mr. Najera
Objectives • Describe how most small molecules cross the cell membrane. • Explain why osmosis is important to cells • Tell the difference between passive and active transport.
Selectively Permeable • Some substances can pass through the membrane while others cannot.
Passive transport • Diffusion and Osmosis are both passive. • Require no extra energy • They rely on a chemical concentration gradients
Diffusion • Main method by which small molecules move across the cell membrane. • Definition: Process by which molecules move from an area of higher concentration to an area of lower concentration.
What causes diffusion? • Molecules are always moving. • Randomly bumping into each other until they are spread apart equal distance. (called equilibrium) • Glass bowl demo…
Osmosis • The diffusion of water through a selectively permeable membrane. • Because cells cannot function properly without adequate water, many cellular processes depend on osmosis.
What’s the difference? • Remember water will move to areas that have higher (salt) molecule concentrations • Non-water molecules will move in the opposite direction high concentration to low concentration.
Effects of osmosis on blood • Draw on the board (page 105)
Active Transport • Requires the cell to use it owns energy to move some molecules across the membrane in either direction. • Performed by transport proteins embedded in the membrane that actively PUMP the molecules across the membrane.
