How Does Stuff Get Into and Out of the Cell Cell Movement How Does Stuff Get Into and Out of the Cell

Major Factor Cell Membranes All cells have a cell membrane Functions: Controls what enters and exits the cell to maintain an internal balance called homeostasis Provides protection and support for the cell

About Cell Membranes Cell membranes have pores (holes) in it Selectively permeable: Allows some molecules in and keeps other molecules out The structure helps it be selective! Pores

Define selectively permeable membrane A membrane that allows only certain materials to cross it Materials pass through pores in the membrane Small molecules pass through – ex: water Large molecules can’t pass through – ex: proteins and complex carbohydrates

KEY CONCEPT… Materials move across membranes because of concentration differences. HIGH to LOW NO ENERGY Energy NOT REQUIRED for particles to move from areas of HIGH concentration to areas of LOW concentration. (Passive Transport) Energy REQUIRED for particles to move from areas of LOW concentration to HIGH concentration. (Active Transport) LOW to HIGH ENERGY

Types of Cellular Transport high low Weeee!!! Passive Transport - cell does not use energy Diffusion (of small particles) Osmosis Active Transport - cell does use energy Endocytosis Exocytosis high low This is gonna be hard work!!

Passive Transport cell uses no energy molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration. (High  Low)

Passive Transport: 1. Diffusion Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) Diffusion continues until all molecules are evenly spaced (equilibrium is reached)- Note: molecules will still move around but stay spread out.

Diffusion The movement of molecules from a area in which they are highly concentrated to a area in which they are less concentrated. Occurs without control or energy use Affected by: Size of molecules Size of pores in a membrane Temperature

Passive Transport: 2. Osmosis Osmosis animation 2. Osmosis: diffusion of water through a selectively permeable membrane. Water moves from high to low concentrations Water moves freely through pores.

(Low  High) Active Transport cell uses energy actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration (Low  High)

Endocytosis Very large molecules or substances must enter the cell by the membrane pinching inward:

Types of Active Transport Endocytosis 1. Endocytosis: taking bulky material into a cell Uses energy Cell membrane in-folds around food particle “cell eating” forms food vacuole & digests food This is how white blood cells eat bacteria!

Endocytosis in action…..

Exocytosis The cell gets rid of secretions or wastes

Types of Active Transport Exocytosis: Forces material out of cell in bulk membrane surrounding the material fuses with cell membrane Cell changes shape – requires energy EX: Hormones or wastes released from cell

Why are osmosis & diffusion important?

Why are osmosis & diffusion important? All living things have certain requirements they must satisfy in order to remain alive – maintain homeostasis These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes. These tasks happen at the cellular level. Molecules move through the cell membrane by diffusion.