Chapter 7:

Cell Transport

Structure of the cell membrane:

Passive Transport – movement of molecules without using energy

1. Diffusion-molecules move from high to low concentration

2. Osmosis – diffusion of water

to speed up diffusion – stir, heat, or increase the concentration

Types of solutions:

Hypotonic- high concentration outside the cell, water moves into the cell, cell swells

Hypertonic – high concentration inside the cell, water moves out, cell shrinks

Isotonic – equal concentration inside and out side of the cell, no change in size

Which type of solution is each cell in?

Examples:1. Ameba in a pond

Hypotonic:

- More water outside than inside, water moves into the cell

- Uses its contractile vacuole to constantly pump water out of the cell

- Cytolysis – cell bursts from internal pressure

Examples:2.plant roots in moist soil

Hypotonic:

-water diffuses into the roots

-Central vacuole is full, pushes against the cell wall

-cell has high turgor pressure(water pressure inside the plant cell)

Examples:3.plant roots in dry soil

Hypertonic:

-water diffuses out

-Central vacuole shrinks, cell collapses, plant wilts

-plasmolysis- loss of turgor pressure

Problems:1. Why does saltwater dry out cells?

Osmosis is the movement of water10%salt 90% water20%salt 80% water

Water moves from high to low so it moves out of the cell.

2. Why was salt used to preserve meat?It created a hypertonic environment, drew moisture out of bacteria, and the meat was safe

3. Why does gargling with salt water help ease sore throat pain?It draws water out of the cells, reducing swelling

4. Why is a mister used on vegetables in the grocery store?It creates a hypotonic environment, water diffuses into the cells, keeping them crisp

5. What will happen to the cell in each of the following solutions?

the cell is 10% salt

A) pure water

B) 10% saltwater

C) 15% saltwater

Cell is 90% water

A) 100% water, hypotonic, water moves in

B) 90% water, isotonic, No change

C) 85% water, hypertonic, water moves out

Another type of passive transport:

3. Facilitated Diffusion- carrier proteins assist larger

molecules across a membrane from high to low concentration

Glucose enters the cell this way

4. Ion Channels -

• Ions move through the membrane

from high to low concentration through channel proteins

• Each protein has a specific shape, fits only one type of ion

Active Transport using energy (ATP) to move molecules from low to high concentration

1.Sodium Potassium Pump:

- uses carrier proteins to move 3 Na+ out of the cell and 2 K+ into the cell

- this creates a build up of charge, allowing an electrical impulse to jump from nerve cell to nerve cell

speed: 450 Na+ out and 300 K+ in

each second

2. Endocytosis – cells use energy to ingest fluids or large particles

Steps:1. a pouch forms in the membrane2. material enters the pouch3. the pouch pinches off, forming a

vessicle.

Pinocytosis – ingesting fluidPhagocytosis – ingesting particles or

whole cells

Endocytosis

Exocytosis

3. Exocytosis – reverse of endocytosis

• Substances packaged by the Golgi leave the cell this way