3.2 Diffusion and Cell Transport

POINT > Describe the cell membrane as selectively permeable POINT > Define diffusion POINT > Describe osmosis POINT > Distinguish between passive and active transport POINT > Identify types of active transport

POINT > Describe the cell membrane as selectively permeable ALL cells have a cell membrane made of lipids, with some proteins and carbohydrates

SOME cells have cell walls – ex: plants, fungi and bacteria POINT > Describe the cell membrane as selectively permeable SOME cells have cell walls – ex: plants, fungi and bacteria

Plant cells have a cell wall made of cellulose, a carbohydrate POINT > Describe the cell membrane as selectively permeable Plant cells have a cell wall made of cellulose, a carbohydrate Bacteria and fungi also have cell walls, but they do not contain cellulose Cell walls are porous. Water, carbon dioxide, oxygen and nutrients pass through easily

POINT > Describe the cell membrane as selectively permeable The cell membrane separates the inside of a cell from the outside environment The cell membrane is the “Gatekeeper” of the cell. It controls the movement of materials into and out of the cell

POINT > Describe the cell membrane as selectively permeable The cell membrane is selectively permeable: it allows some substances to pass through and stops other substances

CHECK: What is the cell membrane made of? What is the plant cell wall made of? What does selectively permeable mean?

Diffusion does not require energy from the cell, it is passive POINT > Define diffusion Diffusion is the movement of particles from an area of high concentration to an area of low concentration Diffusion does not require energy from the cell, it is passive Passive means no energy is required outside of cell inside of cell

POINT > Define diffusion Particles move from high concentration to low concentration during diffusion

POINT > Define diffusion Diffusion is an important way that small molecules can enter cells Ex. Oxygen moves into cells and carbon dioxide moves out of cells by diffusion (ex.in the lungs) Unicellular organisms also use diffusion to get gases and other nutrients from the environment

POINT > Define diffusion

POINT > Define diffusion

POINT > Define diffusion

CHECK: What does “passive” mean? Does diffusion require energy from the cell?

POINT > Describe osmosis Osmosis is the diffusion of water through a selectively permeable membrane (like the cell membrane) Water diffuses across a membrane from an area of high concentration to an area of low concentration

POINT > Describe osmosis Osmosis can be a problem if the cell gains or loses too much water Blood must be isotonic with the cell!

POINT > Describe osmosis Cell in Blood Cell in pure water Cell in very salty water

CHECK: What is osmosis? During osmosis, water a) does not move b) goes from low concentration to high concentration c) goes from high concentration to low concentration What happens to a cell placed in pure water? What happens to a cell placed in very salty water?

Larger molecules cannot diffuse through the membrane POINT > Distinguish between passive and active transport Larger molecules cannot diffuse through the membrane Protein channels and carrier proteins help larger molecules like glucose diffuse across. This is also passive transport

CHECK: How does a larger molecule like glucose get across the cell membrane? Does the diffusion of glucose into the cell by a carrier protein require energy?

POINT > Identify types of active transport Active transport is the movement of molecules from areas of low concentration to areas of high concentration Energy is required because molecules must be moved against the concentration gradient

POINT > Identify types of active transport Here a transport protein uses energy to move a sugar against its concentration gradient

CHECK: Does active transport require energy? Active transport requires energy because a) movement is with the concentration gradient b) movement is against the concentration gradient

White Blood Cells engulf bacteria, this also requires energy POINT > Identify types of active transport White Blood Cells engulf bacteria, this also requires energy Some unicellular organisms feed by engulfing

CHECK: Tell whether it is passive transport or active transport: 1) osmosis 2) diffusion 3) engulfing

Homework: Read pages 80-85 S.A. page 85 #1-3 GRAS pages 42-43