Chapter 2, Section 2The Cell in Its Environment

Monday, October 5, 2009Pages 56 -- 60

Objectives

Describe the three methods by which materials move into and out of cells.Compare passive transport to active transport.Explain why cells are small.

Vocabulary Words

Selectively permeableDiffusionOsmosisPassive transportActive transport

Diffusion Demo

Think about the following as you observe the demonstration:

Why did the water in the bag turn purple?Why didn’t the water in the cup turn purple?

Gatekeeper

The cell membrane serves as a gatekeeper.

Some substances are allowed in while others are kept out.

Substances move into and out of a cell through one of these three methods:

DiffusionOsmosisActive transport

Diffusion

It is the process by which molecules move from a higher concentration to a lower concentration.

What causes diffusion and how does it work?

QuickTime™ and aTIFF (Uncompressed) decompressor

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QuickTime™ and aTIFF (Uncompressed) decompressor

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Osmosis

Osmosis is the diffusion of water molecules through a selectively permeable membrane.

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QuickTime™ and aTIFF (Uncompressed) decompressor

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QuickTime™ and aTIFF (Uncompressed) decompressor

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Normal shape ofred blood cell. Cell has shrunk because

water has moved out byosmosis.

Cell is swollen with water that is moved in by osmosis.

Active Transport

Active transport requires the use of energy to move materials through a cell membrane.Passive transport does not require the use of energy.

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Active Transport Proteins

These are also known as ATPs.Their role is to “pick-up” molecules outside the cell and carry them in using energy.Calcium, potassium, and sodium are examples of molecules that must be carried in.

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Engulfing

Engulfing is another form of active transport.

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Why are cells so small?

Think about the organization of organelles within the cell.Think about the cytoplasm.

Homework

Workbook 2.2 -- Due on Wednesday, 10/7.Vocabulary Quiz--Sections 1 and 2 on Wednesday, 10/7.REMINDER: Lab write-up due on Tuesday, 10/6.