Chp 7.3:Cells and their Environments Bio A

Cell Theory 1. All living things are made of one or more cells. 2. Cells are the basic units of structure and function in organisms. 3. All cells arise from existing cells.

Prokaryote vs. Eukaryote Prokaryote- a single celled organism that lacks a nucleus and other internal compartments. The only organisms on Earth for 2 billion years. Eukaryote- organism whose cells have a nucleus.

The Plasma Membrane - Gateway to the Cell

Photograph of a Cell Membrane

Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell

Structure of the Cell Membrane

Passive Transport- Movement across cell membrane that does NOT require energy from the cell Concentration Gradient- a difference in the concentration of a substance. ***Substances move from areas of high concentration to areas of low concentration. Equilibrium- condition in which the concentration of a substance is equal throughout a space.

Diffusion - the movement of high concentration to an area of low concentration caused by the random motion of particles of the substance. Diffusion Animation- #2 #3

Diffusion of Liquids

Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

Cell Membrane Allows Some Things to Pass Through… Osmosis- the diffusion of water through a selectively permeable membrane. #2 Tutorial Cell Membrane is selectively permeable to substances

Permeable- allows most all things to pass through Semi permeable- allows some things to pass through Impermeable- things can not pass through

Cell Membrane Is a lipid bilayer… Has polar heads and non-polar tails Cell membrane Animation The non polar part of the lipid bilayer repels most polar molecules, preventing these substances from passing (except water). So in contrast… very small, non polar substances, pass across cell membrane. Diffusion of such molecules across the cell membrane is known as … Passive Transport.

Hyper, Hypo, Iso….Tonic Fluid outside cell Outside fluid considered… #2 #3 Fluid outside cell Outside fluid considered… Water Diffuses Effect on cell Low water High Solute. Hypertonic * Cell Shrinks High water Low Solute. Hypotonic Cell Swells Same water and Solute Isotonic Stays same size

Cell Membrane Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses

The Plasma Membrane 12/1/2018 G. Podgorski, Biol. 1010

Cells in Solutions

Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic

hypotonic hypertonic isotonic hypertonic isotonic hypotonic

Three Forms of Transport Across the Membrane The Plasma Membrane Three Forms of Transport Across the Membrane 12/1/2018 G. Podgorski, Biol. 1010