Unit 4: The Cell & Its EnvironmentCh. 2:1 (pg. 31) Cell Theory

Ch. 2:3 (pgs. 38-40) Special Cell Processes (Diffusion & Osmosis)

Cells• Who first

observed cells?

• What was he looking at?

• Did he see live cells?–No, just cell

walls.

Robert Hooke

cork

Further Discoveries Lead to the Cell Theory1. All organisms are made of one or more cells.

(Schleiden & Schwann)

2. The cell is the basic unit of structure and function in organisms. (Schleiden & Schwann)

3. Cells are produced from other cells (Virchow)

Cell Theory Rap

Properties of the Plasma Membrane• What are the functions (jobs)

of the cell membrane?1. Boundary between cell & its

environment2. “Gatekeeper”

• Lets certain materials in/out (“selectively permeable”)

A Model of the Plasma Membrane• In general, what does the plasma

(cell) membrane look like?–phospholipid bilayer

• What does the plasma (cell) membrane look like in more detail?–“Fluid Mosaic Model”

• Molecules (like proteins) embedded in phospholipid bilayer & in constant motion

A Model of the Plasma Membrane

Membrane Movement Animation

• What is passive transport?– Does passive transport require energy?

• Why/why not?– Ex. of passive transport?

Movement of Materials Across the Cell Membrane:

Passive Transport

Concentration gradient = differences in concentration

• Ex. Diffusion–How do

molecules of solute move?• Do they ever

completely stop?

Movement of Materials Across the Cell Membrane: Passive Transport

• What is the special name for the diffusion of water?– osmosis

Movement of Materials Across the Cell Membrane: Passive Transport

• What is an isotonic solution?–concentration of

solutes (& water) same on both sides of the membrane

• Which way would water move?

Effects of Water Concentrations on Cells

How osmosis works animation

• What is a hypotonic solution?–lower concentration

of solutes outside cell• higher concentration

of water outside cell• Which way would

water move?

Effects of Water Concentrations on Cells

How osmosis works animation

• What is a hypertonic solution?–higher concentration

of solutes outside cell• lower concentration of

water outside cell• Which way would

water move?

Effects of Water Concentrations on Cells

How osmosis works animation

plasmolysis

cytolysis

What adaptation prevents the plant cell from bursting?

What happens to cells in different types of solutions?

Effects of Water Concentrations on Cells: Cytolysis & Plasmolysis

Which cells were in salt water?How can you tell?

Elodea in salt water

• Even though they’re going w/ the concentration gradient (high low) some substances:– can not dissolve in lipid bilayer– are too large to squeeze through

Membrane FunctionPassive Transport: Facilitated Diffusion

carrier

• So how can these materials permeate the membrane???–Facilitated diffusion

• With the help of:–Channel proteins (pores)–Carrier proteins–Gate proteins

–Does facilitated diffusion require energy? Why/why not?• No, b/c going from high low

Membrane FunctionPassive Transport: Facilitated Diffusion

carrier

Channel & Gate Protein Animations

carrier (transport) protein

channel protein (pores)

Gate opens & ions can pass through

Signal molecule combines w/ gate

Signal molecule not combined w/ gate (gate closed)

Once ions pass through, signal molecules unbind & gate closes

gat e protein

• What is active transport?– Does active transport

require energy?• Why/why not?

– Ex. of active transport?

Movement of Materials Across the Cell Membrane: Active Transport

Concentration gradient = differences in concentration

• How can materials be moved against the concentration gradient (low high)?– transport proteins (pumps) that

use energy (ATP)

Movement of Materials Across the Cell Membrane: Active Transport

Protein/Transport Pumps Animation Active Transport Animation

Passive & Active Transport Animation

• Not all materials can pass through membrane…– So, how do they get into/out of the cell?

• Membrane encloses the material pinches off releases the material on the other side– endocytosis– exocytosis

Exocytosis & Endocytosis Animation 1 Endocytosis & Exocytosis Animations 2

Active Transport:Endocytosis & Exocytosis

• Which way do substances move during endocytosis?– What are 2 types of endocytosis?

• phagocytosis• pinocytosis

– What types of materials are moved by phagocytosis & pinocytosis?

– Do they require energy?

Exocytosis & Endocytosis Animation 1

Endocytosis & Exocytosis Animations 2

Liquid droplets

Active Transport:Endocytosis & Exocytosis

• Which way do substances move during exocytosis?– What types of materials

are moved by exocytosis?• Does exocytosis

require energy?

Exocytosis & Endocytosis Animation 1

Endocytosis & Exocytosis Animations 2Active Transport:

Endocytosis & Exocytosis

The Cell Wall• What is the cell wall?• Where is it located in the cell?• What is it made of?• What type of organisms have cell walls?• What does the cell wall do for the cell?• Does it affect the cell’s permeability?