I. The Plasma Membrane

Quiz:

1. Controls what comes in and out of the cell. It is selectively permeable.

Cell Membrane

2. Protects and separates the cell fromits environment

3. It is often called a 3. It is often called a fluid mosaic fluid mosaic modelmodel

b. Made of a phospholipid bilayer

• i. Two layers of phospholipids• ii. Arranged tail to tail

ii. Has various ii. Has various proteins, carbohydrates proteins, carbohydrates and cholesteroland cholesterol mixed inmixed in

Figure 6-1Simple Plasma Membrane

• proteins are imbedded in the plasma membrane like raisins in raisin bread

II. Passive Transport- the movement of particles in and

out of the cell without using the cell’s energy.

• A. Diffusion - movement of particle- like gases across the cell membrane.

• B. Makes use of a concentration gradient-

the SOLUTE always moves from HIGH concentration to low concentration.

Will continue until Will continue until dynamic equilibrium dynamic equilibrium is reachedis reached

•Can make use of transport proteins- which are selective for certain particles.

Diffusion of Oxygen

C. Facilitated Diffusion

• c. Facilitated diffusion- process of moving particles across the cell membrane using transport proteins.

– i. Transport proteins-found in the cell membrane• 1. Allow some types of ions, sugars and amino acids to

pass through the cell membrane

• 2. There are different types -each is selective - specific for certain particles

– ii. Move particles from areas of HIGH concentration to areas of LOW concentration-moves down the concentration gradient

– iii. Form of passive transport ---no energy

Facilitated diffusion Fig. 6-3

d. Osmosis-type of passive diffusion -it does not use the cell’s energy

1. It is always the movement of WATER particles

2. It moves WATER molecules across a selectively permeable membrane through which the solute (dissolved particles) cannot pass

• ii. Makes use of a concentration gradient -always moves from HIGH concentration to low concentration

• Iii. Will continue until dynamic equilibrium of the solute is reached.

Osmosis the movement of water

•

3. Hypotonic solution

2. Hypertonic Solution

1. Isotonic Solution

Osmosis can create 3 types of solutions:

• 1. Isotonic solution -the solution on the outside of the plasma membrane has the same concentration as the solution on the inside of the membrane.– a. There is no NET movement of WATER

molecules– b. Water will move in and out of the cell at the

same rate– c. The cell will remain the same size– d. Animal cells do best in isotonic solution

Isotonic Solution

2. Hypertonic solutions--the solution outside the cell has less water and more solute than the

solution inside the cell.

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

• a. Water rushes out of the cell• b. Cell shrivels up• c. Causes plasmolysis in plants, plants wilt

Ex: slugs

• 3. Hypotonic solution - the solution on the inside of the cell membrane has less water and more solute than the solution outside of the cell.

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

• a. Water rushes into the cell

• b. Cell swells like a big O

c. Plant cells become turgid due to water pressing outward against cell wall---creates turgor pressure

d. Plant cells do best in a hypotonic solution.

• e. Animal cells swell & burst (lyse) if they take in too much water

III. Active Transport- transport proteins, endocytosis and exocytois

• A. Moves molecules in and out of the cell– Moves materials AGAINST the concentration

gradient– Requires the cell’s energy-- $$$$$$

• iii. Uses transport proteins to help move materials in and out of the cell—3 types include:

1. Carrier Proteins

2. GATE Proteins

3. Channel Proteins-like a straw things can pass through

b. Endocytosis-the process of taking in large particles

i. surrounds the particles with the cell membraneii. Requires cell energy --$$$$$iii. “en” - means “ enter”

2 types of endocytosis

• 1. Phagocytosis- process of engulfing solid particles to create vesicles

• 2. Pinocytosis- the process of engulfing liquid particles

c. Exocytosis - process of removing large particles

i. Used to get rid of wastes, undigested food or to release hormonesii. In the cell the material is enclosed in a vesicle, vesicle fuses with the cell membrane and the material is released outside of the celliii. “ex” - means “exit”

•1. Look at the diagram below. The animal cell has a concentration of 0.7% inside the cell membrane and it is placed in a salt solution with a concentration of 18.5 %. What will happen if the cell remains in the solution? Explain your answer in terms of osmosis.

18. 5% 0.7%

• 2. A red blood cell contains a 0.9% concentration of salt inside the cell. If the red blood cell is placed in a solution that is pure water, what will happen to the cell? Is the solution hypertonic, hypotonic, or isotonic?

• 3. A plant cell contains a 1% concentration of solute inside the cell. If the plant cell is placed in a solution that is 5% solute, what will happen to the cell? It the solution hypertonic, hypotonic or isotonic?

• Saturated fats Unsaturated fats