Pre-class activity 11/3

A cell membrane is responsible for maintaining the environment of a cell by determining which substances to let in and out of the cell.

Which of the 7 properties of life (from chapter one) best matches the function of the cell membrane?

Metabolism Responsiveness Reproduction

Growth Homeostasis Heredity

Cell Organization

The maintenance of a constant internal state in a changing environment

Homework (due 11/5)

Vocab, 1st 8 terms

Organization of the Cell Membrane

Phospholipid Bilayer

(Water loving) (Water hating)

Membrane Proteins

Proteins have both polar and nonpolar parts. The nonpolar parts are attracted to the inside of the membrane while the polar parts are attracted to the outside of the membrane. This is how proteins can become embedded in the cell membrane.

4 Types of Proteins

Cell Surface Markers

A chain of sugars attached to proteins on the cell’s surface

Receptor ProteinsCells sense their surroundings by binding to certain substances outside the cell which cause changes inside the cell.

Enzymes

Help with biochemical reactions

Transport Proteins

Aid the movement of substances into and out of the cell that wouldn’t normally be able to pass through the bilayer

Pre-class Activity 11/5

How does that cell membrane function to maintain homeostasis (balance) in the cell?

It allows the movements of substances in and out of the cell. As nutrients are used up or wastes build up, they can be replenished or removed to create balance in the cell.

Cell Transport(How cell move substances across the cell membrane)

Passive Transport

(Does not require energy)

Active Transport

(Requires Energy)

Diffusion Osmosis

Simple Facilitated

PumpsVesicles

Endocytosis Exocytosis

Solutions

A mixture of a solid and a liquid

Solvent Solute

Dilute

Concentrated

Concentration/Strength

Diffusion

The movement of substances from an area of high concentration to an area of low concentration (concentration gradient) to create balance.

Simple Diffusion vs. Facilitated Diffusion

Simple DiffusionSmall, non-polar molecules pass directly through the bilayer

Facilitated Diffusion

Large, polar molecules and ions required channel proteins or carrier proteins to cross the membrane.

Pre-class Activity 11/11/08

Examine these two glasses of KoolAid. Which has the greater amount of solute?

How can you tell?

Homework

Last 3 vocab Terms, Chapter 8 Vocab Quiz Friday 11/14

A B

B

Darker in color, less dilute

Pre-class Activity 11/12/08

Why do these two plants look different?

What structure within the plant cell has been most effected by this change?

Vacuole

Osmosis

The movement of water across a selectively permeable membrane from an area of high concentration of water to an area of low concentration of water.

Movement of Water

When the extracellular fluid is…….

HypertonicHigh SoluteLow Water

HypotonicLow SoluteHigh Water

IsotonicEqual SoluteEqual Water

With respect to the inside of the cell

Cell Transport(How cell move substances across the cell membrane)

Passive Transport

(Does not require energy)

Active Transport

(Requires Energy)

Diffusion Osmosis

Simple Facilitated

PumpsVesicles

Endocytosis Exocytosis

Passive Transport vs. Active Transport

+

With the Concentration Gradient Against the Concentration Gradient

No Energy Required Energy Required

Active Transport - Pumps

Sodium-Potassium Pump

Active Transport - Vesicles

Pre-Class Activity 11/17/08

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++ ++ +

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If the substance was able to move through the membrane which direction would it go? What is the name of the process that describes the motion of particles?

Diffusion

If only water was able to move through the membrane which direction would it go? What is the name of the process that describes the motion of water?

Osmosis

Homework (due 11/18): Chapter 8 Section Quizes Chapter 8 Test: Thursday

Cell Communication

Sending SignalsHow signals are sent depends on how far away target cells are.

Close targets are signaled by direct contact

Far away targets are signaled by chemicals and nerve cells

Signals can come from within or outside of the body

Cell CommunicationReceiving SignalsReceptor Proteins receive specific signals by binding substances at specific binding sites.

Receptor proteins enable a cell to detect its environment

Once it binds a signal molecule, the protein changes its shape in the membrane which relays information into the cytoplasm

Cell Communication

Responding to SignalsOnce a signal molecule binds to a receptor protein, one of

three things can occur

1. Change in the permeability of the membrane

2. Activation of enzymes that trigger chemical reactions in the cell

3. Formation of a second messenger (acts as a signal molecule inside the cell)