BELL WORK: Answer the following questions on your bell work page: 1.A scientist finds a unicellular organism. He can see its DNA is free-floating in the center of the cell. What kind of cell is this, and how do you know? 2.Which organelles help produce and move proteins in a cell? (hint: there are THREE)
Today’s Standard (B.4B): Investigate and explain cellular processes including…transport of molecules Today’s Essential Question: How do molecules move in a cell?
Atom Molecule Organelle Cell *Life* Tissue Organ Organ System Organism Does not have Does Have
CELL MEMBRANE: thin, flexible barrier surrounding all cells
What is the cell membrane’s function (job)? (2 things)
Two main functions: 1) regulate what enters (food, water, & oxygen) & leaves (waste) 2) protection & support
What is the cell membrane composed (made) of? (3 types of molecules)
LIPIDS: main component of cell membrane – double layer called the lipid bilayer or phospholipid bilayer – hydrophobic and hydrophilic tails (hydro=water)(phobic=fear) (phile=love) DRAW THIS!
Allot like a basketball
PROTEINS: embedded into the lipid bilayer – Form channels or pumps (pathways) to help move large molecules
CARBOHYDRATES: attached to proteins outside of the bilayer – allow cells to communicate with each other carbohydrates
How do molecules move in or out through the cell membrane?
Why does food coloring spread out in water?
In a solution, particles are constantly moving. They collide with one another and spread out randomly.
DIFFUSION: particles move from an area of HIGH concentration to an area of LOW concentration
CONCENTRATION: the amount of solute (stuff) dissolved into a solvent (liquid) KOOL-AID is the solute WATER is the solvent CONCENTRATION is how much Kool-Aid you put in
CONCENTRATION GRADIENT: a difference between two concentrations If diffusion is going from high concentration to low concentration, what direction is it moving on the concentration gradient? High Concentration Low Concentration
EQUILIBRIUM: the concentration of a solute is the same throughout a system – particles continue to move – the goal of diffusion!
Diffusion does NOT require energy!!
The rate (speed) at which molecules pass through a membrane depends on its permeability.
PERMEABLE membranes allow all substances to pass through IMPERMEABLE membranes allow no substances to pass through
Biological (cell) membranes are SELECTIVELY permeable – Some substances can pass through, while others cannot
OSMOSIS: diffusion of water through a selectively permeable membrane – does NOT require energy!