QOD: How is a receptor different from a recognition protein? LG: Understand how cells maintain homeostasis by explaining how different environmental conditions can affect the cell

Chapter 7.3 Cell Transport

Concentration Gradient Concentration – the amount of solute compared to water in the solution – High Concentration = large amount of solute in the solution – Low Concentration = small amount of water in the solution

Concentration Gradient Concentration Gradient– the difference in the amount of solute between different parts of the solution (sometimes across two sides of a membrane).

Cell membrane transport There are 2 types of cell membrane transport: – Passive Transport Things flow from High to low concentration DOES NOT USE ATP (energy) – Active Transport Things flow from Low to high concentration USE ATP (energy)

Another perspective on passive and active transport

THE “GOAL” of molecules IS…..Equilibrium! When is equilibrium reached when discussing cell membrane transport? – When the concentrations of particles are the same on both sides

Passive Transport Diffusion – The movement of particles from areas of high concentration to low concentration – –

Facilitated Diffusion Particles flow from high concentration to low concentration but this time they need the help of proteins to get through the cell membrane.

Facilitated diffusion

Passive transport Osmosis – The facilitated diffusion of water across a selectively permeable membrane – Important in maintaining cell homeostasis – Water moves from high concentration to low concentration

Osmosis Osmosis is controlled by the amount of solutes on either side of a membrane

Review of Solution Terms Solution = Saltwater Solvent = Water Solute = Salt

Osmosis – Types of Solutions When dealing with osmosis, water can either move into the cell or out of it. The solute cannot move to equal out the solution so the water has to. We describe the solutions that cells are in as either hypotonic, isotonic, or hypertonic. What are the concentrations? 90 % solute 40% solute

1.Isotonic 2.Hypertonic 3.Hypotonic

Isotonic Solution Isotonic solution – Concentration of solute is the same in the cell and the area around the cell. Give me an example of an isotonic solution that some of you use everyday

Isotonic solution

Hypertonic Solution Hypertonic solution – concentration of solute is higher in the solution than in the cell. Where is water going to move in order to reach equilibrium (Equal concentrations)? – Outside the cell

Hypertonic solutions Since water moves out of the cell the cell will shrink So, Hypertonic solution, high concentration of solute, cell will shrink

Plant and animals cells in a Hypertonic Solution

Hypotonic Solution Hypotonic Solution – Concentration of solute is lower in the solution than in the cell. Where is water going to move in order to reach equilibrium (Equal concentrations)? – Inside the cell

Hypotonic solutions Since water moves into the cell the cell can explode So, Hypotonic solution, low concentration of solute, cell can explode

Plant and animal cells in a hypotonic solution

Osmosis L06/rbc.html L06/rbc.html

Active Transport Molecules move from low concentration to high concentration – Requires energy….why?

Active Transport Molecular Transport – moves small molecules – Protein Pumps Bulk Transport- moves larger molecules – Endocytosis – Exocytosis

Protein Pumps Small molecules and ions carried across the cell membrane by proteins in the membrane that act like pumps Low  high

Other membrane transport activities that require energy Endocytosis – Engulfing of large particles or liquids from outside the cell

Other membrane transport activities that require energy Exocytosis – Release of large particles or liquids from inside the cell Inside the cell Outside the cell