Unit 3

 Smallest unit of living organisms  Four basic parts of the cell  Cell membrane – encloses the cell  Nucleus – houses genetic material  Cytoplasm- fills the cell (mostly water)  Organelles – specialized structures in cell

 Thin, flexible, elastic  Selectively permeable  Oxygen & Carbon Dioxide diffuse easily and are soluble in lipids  Small polar (H2O) small enough to pass between lipid molecules (aquaporins)  Large water soluble molecules and ions cannot pass without help  Lipid Bilayer  Phospholipids  Hydrophobic tails  Hydrophilic heads

Cell Membrane Structure carrier protein protein channel Globular proteins carbohydrate phospholipid bilayer Fibrous Proteins Cholesterol molecule

 Passive Mechanisms – no energy required Molecules move down their concentration gradient.  Diffusion-  Random movement of molecules  molecules move from high concentration to low concentration  until equilibrium is reached

Diffusion high concentration low concentration

 Osmosis- water moves across a semi- permeable membrane from low solute concentration to high solute concentration  Isotonic solution  Two solutions with same solute concentration  Hypotonic solution  Solution with lower solute concentration and higher water concentration  Hypertonic solution  Solution with higher solute concentration and low water concentration

 1 = Isotonic  no net movement of water  Normal state for animal cells  2 = Cell- hypertonic; environment – hypotonic  Water enters cell; cell swells & burst  Cytolysis; cell dies  3 = Cell- hypotonic; environment – hypertonic  Water exits cell; cell shrinks & dies

Filtration – small molecules forced to move through membrane Tissue Fluid: -result of filtration -composed of water & small dissolved substances Force used: -Blood pressure -hydrostatic pressure

Facilitated diffusion- Diffusion of solutes across membrane with help of transport proteins (channel/carrier) Passive transport Transport proteins are specific Model Protein has 2 conformations Solute binds to protein Protein changes shape Solute released to other side of membrane

Facilitated Diffusion high concentration low concentration

 Requires cell energy (ATP)  Materials moved against concentration gradient (low to high)

 Pumps  Molecule or ion combine with carrier protein  Shape of carrier protein changes with the help of energy (ATP)  Particle is able to move against the concentration gradient  Other examples:  Sugar, amino acids  sodium, potassium, calcium, hydrogen ions

 Endocytosis (1-4)  Intake of large molecules, solids, food  Material collects in pocket of cell membrane  Pocket pinches off forming vesicle

 Exocytosis (5-8)  Release of large molecules, solids, wastes from cell  Vesicle fuses with cell membrane  Contents released to outside

 Cell eating  Intake of solids, food, bacteria  nonspecific

 Cell drinking  Intake of small droplets of liquid (oil)  nonspecific

 Specific  Model (picture)  Molecule binds to receptor protein  Complex migrates to coated pit  Pit pinches off forming vesicle  Receptor protein returns to cell membrane