Cell Transport

What can cross the cell membrane easily?

• 1) Hydrophobic molecules- like lipids, carbon dioxide, and oxygen can dissolve in membrane and cross it w/ ease

• 2) Water- although it is polar it’s tiny enough to pass b/w the fatty acid tails of the membrane (osmosis)

• *These molecules use passive transport (diffusion & osmosis) (no energy used) to cross the membrane

Cell Membrane

What molecules have trouble crossing the cell membrane?

• 1) Sugars and amino acids (large molecules)

• 2) ions (polar) (ex. Na+ , K+)• *These molecules use facilitated

diffusion (w/ help from transport proteins like channel or carrier proteins) (no energy used) to cross the membrane or they use active transport (requires energy)

Crazy Cell Transport Vocab Words We Need to Know

• Equilibrium- concentration of a substance is the same throughout a space

• Solute- substance that dissolves in another

Ex. Sugars, salt, amino acids, & ions

• Solvent- substance that dissolves the solute

Ex. In cells, solvent is water

• Solution- mixture of solutes and solvent

Passive Transport

• Passive Transport- movement of a substance through a cell’s membrane WITHOUT USING ENERGY

• *PARTICLES MOVE FROM AN AREA OF HIGHER CONCENTRATION (LARGE AMOUNT) TO AN AREA OF LOWER CONCENTRATION (SMALL AMOUNT).

Concentration Gradient

HIGH

LOW

Types of Passive Transport

• Osmosis- movement of water through a membrane from an area of high conc. to low conc.

• *water always moves across cell membranes to maintain equilibrium

Types of Osmosis• Isotonic Solution- solute conc. in the

solution outside of the cell is the same as it is inside the cell

• -Likewise, conc. of water in the solution outside the cell is the same as the conc. of water inside the cell

• ex. Equal amounts of water will move into and out of the cell, cell volume/shape is maintained

• ex. IV’s at the hospital are isotonic to your cells.

Isotonic Solution

• Isotonic Animation

• *Red dots = solute

• *Black dots = water

Types of Osmosis• Hypotonic Solution- solute conc. in

the solution outside the cell is lower than inside the cell

• -Therefore, more water is present outside the cell than inside

• ex. Water moves into the cell and may cause it to burst

• ex. Why grocery stores spray fruits and veggies

Hypotonic Solution

• Hypotonic Solution Animation

• *Red dots = solute

• *Black dots = water

Types of Osmosis

• Hypertonic Solution- solute conc. in the solution outside the cell is higher than inside the cell

• -Therefore, more water is present inside the cell than outside

• ex. Water moves out of the cell and causes it to shrivel

Hypertonic Solution

• hypertonic solution animation

• *Red dots = solute

• *Black dots = water

Review of Isotonic, Hypertonic, and Hypotonic Solutions

• Isotonic, Hypertonic, and Hypotonic Solutions' Animations

Types of Passive Transport (continued)

• Diffusion- movement of particles directly through a membrane from an area of high concentration to low conc. (ex. Oxygen, carbon dioxide, water, lipids all use this process)

• Ex. Oxygen diffuses into the blood stream b/c there is a higher conc. of oxygen in the lung’s air sacs than there is in the blood

• Animation: How Diffusion Works

Types of Passive Transport (cont.)

• Facilitated diffusion- transport of large particles through a membrane by a channel or carrier protein

• Ex. Glucose, amino acids, ions• *particles move from a high conc. to

a low conc.• *no energy used• Facilitated Diffusion animation

Active Transport

• Active Transport- transport of specific particles through a membrane by a channel or carrier protein

• ex. Ions, etc.• *particles move from a low conc. to a

high conc.• *REQUIRES ENERGY

Active Transport

• Active Transport Video

Types of Active Transport• *Sometimes some food molecules are too large to

move into the cell by transport proteins• 1. Endocytosis- process by which large food particles and extracellular particles are engulfed by a portion of the cell’s membrane• ex. Phagocytosis (cell eating)- white blood cells engulf bacteria• ex. Pinocytosis (cell drinking)- uptake of extracellular fluid• ENTER THE CELL• Animation: Phagocytosis

Types of Active Transport (cont.)

• Exocytosis- reverse of endocytosis- dumping of waste materials outside a cell by discharging them from waste vesicles that fuse w/ the plasma membrane

• EXIT CELL

Exocytosis Animation

Overall Idea of Cell Transport

• cell is able to function b/c it is able to control what enters or leaves

• -like a home, a cell membrane has “doors with locks” that only allow certain particles to pass through

• -plasma membrane is selectively permeable b/c it allows the passage of some solutes but not others