Science 10 Unit C 2.2.notebook

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Science 10 Unit C: 2.2

The Cell Membrane

(p 274­283)

Review: The Particle Theory of Matter

1. All matter is made of particles but the particles may be different in size and composition.

2. The particles are constantly moving or vibrating; particles move least in solids and most in gases. Adding or removing energy will affect the movement.

3. The particles of matter are attracted to one another or are bonded together.

4. Particles have spaces between them that is smallest in solids (except for ice) and greatest in gases. These spaces may be occupied by the particles of other substances

Diffusion: Is the natural movement of particles from an area of high concentration to an area of low concentration.

The rate of diffusion can be increased by adding energy.

Science 10 Unit C 2.2.notebook

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Active Transport Passive Transport

Requires Energy! Will happen naturally! No energy needed!

Cell Membranes and DiffusionThe cell membrane is a selectively permeable membrane (or semi­permeable membrane)

This means it only allows the diffusion of some things.

The diffusion of water across the cell membrane is called osmosis.

Science 10 Unit C 2.2.notebook

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Predicting Water Movement

A hypertonic solution has a higher solute concentration than the inside of the cell.

Water will move OUT of the cell.

A hypotonic solution has a lower solute concentration than the inside of the cell.

Water will move INTO the cell.

Solute concentration is the same inside the cell as outside of the cell. No water movement will occur.

Facilitated Diffusion:Only substances soluble in lipids can pass directly through the cell membrane.

Substances that are insoluble in lipids, but soluble in water need a way to cross the cell membrane. This is done by facilitated diffusion.

Channel Proteins create a pore/channel/tunnel through the cell membrane that certain solutes can pass through.

Carrier Proteins can change shape around a solute and then literally carry them across the cell membrane.

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Active Transport: Active Transport requires energy because it moves particles from an area of low concentration to an area of high concentration.

The form of energy used comes from a substance created in the mitochondria called adenosine triphosphate. ( or ATP)

Science 10 Unit C 2.2.notebook

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Endocytosis: Uses the formation of a vesicle to bring particles into the cell.

Exocytosis: Uses a vesicle fusing with the cell membrane to release particles out of the cell.

Both are active transport, and require ATP

Questions: pg 283: #2,4­7

Science 10 Unit C 2.2.notebook

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Science 10: Unit C 2.4

Is Bigger Better???

p. 289­293

The cell is an efficient, open, life system. As the smallest unit of life, a cell must be able to efficiently carry out all of the life processes. The transport of materials in and out of the cell is therefore critical. This means that the more cell membrane there is in a cell, the more efficiently transport can occur.

In order to maximize efficiency, a cell wants to have the highest surface area to volume ratio.