Cellular Transport

Cell Borders Cell Wall – Provides support and protection. (In plants!) Made of cellulose – a tough carb Cell Membrane – Controls what enters and leaves cell. (In ALL cells!)

Cell Membrane Its function is to maintain a balance called homeostasis within the cell. Remember that the cell membrane is semi- permeable or selectively permeable. It controls how, when, and how much stuff enters and leaves the cell. It is picky.

Cell Membrane Structure Phospholipids: arranged in a bilayer with polar phosphate heads out and non-polar fatty-acid tails in (allows the cell to easily separate the outside environment from the inside environment)

Cell Membrane Structure Transport Proteins: move needed substances into and out of the cell that will not easily pass through the phospholipids

Cell Membrane Structure Cholesterol: keeps the fatty-acid tails from sticking together and adds to the fluidity of the membrane Carbohydrate chains: defines cells characteristics and helps to read chemical signals

How is a window screen like a cell membrane? What are some things that can pass through a window screen? What are some things that cannot? Why is it important for a cell membrane to regulate what moves into and out of a cell?

Fluid Mosaic Model

Solutions and Cellular Transport Solution: a mixture formed when one substance is dissolved into another substance; ex: Kool-Aid, Jell-o Solute: the substance being dissolved; ex: Kool-Aid mix, Jell-o mix Solvent: the substance doing the dissolving; ex: water Concentration Gradient: the difference in concentrations of solute between two areas There is a concentration gradient across the cell membrane.

Essential Questions What are the processes of diffusion, facilitated diffusion, and active transport? What is the effect of a hypotonic, hypertonic, or isotonic solution on a cell? How do large particles enter and exit cells?

2 Ways to Cross the Membrane Passive Transport – NO energy is required to move a substance across the membrane. Movement of solute along/with the gradient; ex: floating in the lazy river Active Transport – Energy IS REQUIRED to move a substance across the membrane. Movement of solute against the gradient; ex: trying to swim upstream or against the current

Passive Transport - Diffusion Diffusion - movement of particles from areas of high concentration of solute to areas of low concentration of solute. (water, oxygen, carbon dioxide) When the concentration is the same throughout, equilibrium is reached. Temperature and size of molecule affect the rate of diffusion.

Passive Transport - Diffusion

Passive Transport - Osmosis Osmosis – the diffusion of water particles across a membrane. *****Water moves from low solute to high solute.***** Why is osmosis important for cells?

How Osmosis Works in the Cell Hypotonic - Concentration of solutes outside is lower than it is inside the cell. Water in

How Osmosis Works in the Cell Hypertonic - Concentration of solutes outside are higher than inside of the cell. Water out

How Osmosis Works in the Cell Isotonic – Concentration of solutes outside and inside cell are equal. Equilibrium – water moves in and out at the same rate

Passive Transport: Facilitated Diffusion Facilitated Diffusion – Larger molecules (like glucose, sodium ions, and chloride ions) move across the membrane with the help of protein channels. Moves from high concentration of solutes to low concentration of solutes– no energy required.

Active Transport Large molecules (glucose) and ions (Na+, K+, Ca+2) pass across the membrane using proteins and ATP ENERGY when moving from low to high concentrations.

Active Transport: Exocytosis - Wastes and products are packaged in vesicle by the Golgi and sent OUT of cell

Active Transport: Endocytosis – cell membrane forms vesicle and brings things INTO the cell.

Types of Endocytosis Phagocytosis – engulfs by surrounding membrane around solids. “Phago-” means “to eat” Pinocytosis – pinches membrane and brings in liquids. “Pino-” means “to pinch”

Odd Man Out Osmosis Diffusion Cell membrane

Odd Man Out Semi permeable Cell membrane Phospholipid

Hydrophillic Protein Channels Diffusion

Osmosis Passive Transport Active transport

Facilitated Diffusion ATP Passive Transport

Solute Water Solvent

Osmosis ATP Active transport

Homeostasis Hydrophillic Protein Channels

Solvent Isotonic Solution Hypotonic Solution

Isotonic solution Hypertonic solution Semi Permeable