7.4 – Cellular Transport

Remember from 7.2….. Selective Permeability – substances do NOT enter the cell indiscriminately. –Nonpolar molecules tend to cross membrane easily –Polar molecules (water, glucose) cross membrane slowly

Passive Transport  Movement of particles across the cell membrane without using energy 7.4 Cellular Transport Cellular Structure and Function Three Modes of Passive Transport  Diffusion  Facilitated Diffusion  Osmosis Chapter 7

Diffusion  Movement of particles from an area of high concentration to an area of lower concentration  Tendency to spread evenly through space Cellular Structure and Function Starting Conditions Diffusion LowHigh Low 7.4 Cellular Transport Chapter 7

 Diffusion is controlled by: Cellular Structure and Function  Temperature  Pressure  Concentration Dynamic Equilibrium  Reached when diffusion of material into the cell equals diffusion of material out of the cell  Molecules continue to move, but the concentrations of molecule on both sides stays the same. 7.4 Cellular Transport Chapter 7

DIFFUSION DEMO MOLECULES FROM THE SPRAY ARE HIGHLY CONCENTRATED CLOSEST TO ME. OVER TIME, THEY WILL DIFFUSE THROUGH THE AIR TO THE BACK OF THE ROOM.

Facilitated Diffusion - Still no energy needed Cellular Structure and Function  Movement of materials across the plasma membrane using transport proteins 7.4 Cellular Transport Chapter 7 Two main types of proteins used = Carrier proteins and Channel Proteins

Cellular Structure and Function Carrier Proteins Channel Proteins 7.4 Cellular Transport Chapter 7 Channel Proteins – a hollow protein that spans the width of the cell membrane and acts as a tunnel for small particles. Carrier Proteins - A protein that transports specific substance through intracellular compartments, into the extracellular fluid, or across the cell membrane.

Osmosis Cellular Structure and Function  Diffusion of water across a selectively permeable membrane Three Types of Solutions  Isotonic  Hypotonic  Hypertonic 7.4 Cellular Transport Chapter 7

Osmosis Water always moves from an area of LOW solute concentration to an area of HIGH solute concentration. OR From an area of HIGH water to an area of LOW water

LEFT SIDE = 15 Sugar Molecules 10 H2O Molecules Ratio = 1.5 Sugar per H2O RIGHT SIDE = 3 Sugar Molecules 27 H2O Molecules Ratio = 0.1 Sugar per H2O LEFT SIDE = 15 Sugar Molecules 23 H2O Molecules Ratio = 0.65 Sugar per H2O RIGHT SIDE = 3 Sugar Molecules 14 H2O Molecules Ratio = 0.2 Sugar per H2O Eventually, both sides of the partially permeable membrane will have equal concentration of sugar and water molecules.

Osmosis in Plant and Animal Cells…. Tonicity – ability of a cell to gain or lose water Three types: –Isotonic –Hypertonic –Hypotonic In plant cells, the cell wall makes sure only so much water is allowed to enter the cell. The wall maintains balance.

Blood Cell Plant Cell Isotonic Solution Cellular Structure and Function  Water and dissolved substances diffuse into and out of the cell at the same rate. 11,397x 7.4 Cellular Transport Chapter 7

Blood Cell Hypotonic Solution Cellular Structure and Function  Solute concentration is higher inside the cell.  Water diffuses into the cell. Plant Cell 13,000x 7.4 Cellular Transport Chapter 7

Plant Cell Hypertonic Solution Cellular Structure and Function  Solute concentration is higher outside the cell.  Water diffuses out of the cell. Blood Cell 13,000x 7.4 Cellular Transport Chapter 7