7.3 CELL TRANSPORT CT Science Framework: Explain the role of the cell membrane in supporting cell functions.

A. Cell membrane 1. Functions: a. protective barrier b. gives structure and shape c. regulates what enters and exits a cell

A. Cell membrane ( cont.) 2. Structure of a. Double membrane of lipids -likes water ; repels waters b. Proteins are embedded within the layer

Photograph of cell membrane The cell membrane is a fluid mosaic of lipids, proteins, and carbohydrates. The cell membrane is a fluid mosaic of lipids, proteins, and carbohydrates. FLUID- because the molecules move about ; like a liquid FLUID- because the molecules move about ; like a liquid MOSIAC- because the proteins are scattered within the lipid layer MOSIAC- because the proteins are scattered within the lipid layer

B. Transport thru the cell membrane 1. Diffusion 1. Diffusion a. passage of materials across a space from an area of high concentration to an area of low concentration until an equilibrium is reached b. Concentration: the mass of a solute in a given volume of solvent (grams/liter) (example: 12 grams of salt in 3 liters of water-what is the concentration?) (example: 12 grams of salt in 3 liters of water-what is the concentration?)

Diffusion (cont) c. Equilibrium: Concentration of a substance is the same across a space

Diffusion (cont)

Diffusion of a liquid

d. Factors that affect diffusion P E S T S P E S T S  Permeability of the membrane  Electrical charge of the substance- neutrally charged substances move easier  Size of the molecule  Temperature speeds up diffusion  Solubility in water

A Cell’s Environment is AQUEOUS ( water-based)

Diffusion ( cont.) 2. Osmosis is a type of: a. Diffusion of water across a space from a point of high concentration to a point of low concentration b. Depends upon the concentration of a solute in a given volume of solvent which determines the type of cell solution

Osmosis ( cont.) 3. CELL SOLUTIONS: a. Isotonic Solution: the amount of solute = the amount of solvent in and out of the cell a. Isotonic Solution: the amount of solute = the amount of solvent in and out of the cell Water moves in BOTH directions Water moves in BOTH directions

Isotonic

Isotonic solution

Osmosis Cont. b. Hypertonic Solution: Has a high concentration of solute vs. solvent Cells SHRINK because they lose water when placed in a hypertonic solution Cells SHRINK because they lose water when placed in a hypertonic solution Example of hypertonic solution is salt water Example of hypertonic solution is salt water

Hypertonic

Hypertonic Solution

Osmosis ( cont.) c. Hypotonic solution: Has a LOW concentration of solute vs. solvent c. Hypotonic solution: Has a LOW concentration of solute vs. solvent Cells SWELL when placed in a hypotonic solution because they GAIN water Cells SWELL when placed in a hypotonic solution because they GAIN water Example: Fresh water Example: Fresh water

Hypotonic

Hypotonic Solution

Solution Environments:

ISOTONIC HYPERTONIC HYPOTONIC

4. In other words…… a. In an isotonic solution….. a. In an isotonic solution….. -__________ happens to a cell, it looks the ___________ b. In a hypertonic solution……. b. In a hypertonic solution……. -the cell _________ due to water ________ c. In a hypotonic solution…………. -the cell ________ due to water ________

4. In other words…… a. In an isotonic solution….. a. In an isotonic solution….. -nothing happens to a cell, it looks the same b. In a hypertonic solution……. b. In a hypertonic solution……. -the cell shrinks due to water loss c. In a hypotonic solution…………. -the cell swells due to water gain

5. Facilitated Diffusion The use of membrane proteins to help diffuse large particles ( eg-glucose, amino acids) across a cell membrane. The use of membrane proteins to help diffuse large particles ( eg-glucose, amino acids) across a cell membrane.

Facilitated diffusion

C. Passive Transport 1. Diffusion and osmosis are types of passive transport. 1. Diffusion and osmosis are types of passive transport. a. Cell does not use energy to move a substance across the membrane/space. b. Cell energy is called ATP

D. Active Transport 1. Energy (ATP) is required to move a substance across the membrane/space. 2. Involves moving large materials into and out of cell. 3. Types of -Endocytosis: move materials into a cell - Exocytosis: move materials out/exits of cell - Exocytosis: move materials out/exits of cell

Endocytosis