Honors Biology

 BIG biological molecules  Made of smaller parts  Monomers  Carbon-based (organic)  Carbohydrates  Nucleic acids  Proteins  Lipids

 Monomer?  Glycerol head  Fatty acid tail  Used for:  Long term energy storage  Insulation  Major component of membranes  Signaling molecules and hormones  Examples:  Fats, oils, waxes  Found in:  All the good tasting foods

 All cells have cell membranes  Some cells (eukaryotes) have membranes surrounding organelles  Example: nucleus  All cells need to import and export molecules in order to function properly and maintain homeostasis

1. Regulate passage of nutrients, wastes, gases, and water into and out of cell 2. Selectively permeable – “picky” about what passes 3. Separate cell from the environment 4. Allow cells to communicate with other cells via receptors on the surface

 Made of phospholipid bilayer  Phosphate (hydrophilic) “head”  Lipid (hydrophobic) “tail” Phospholipid bilayer

 Channel protein  Allow large molecules to pass through Protein channels

 Receptor Protein  Receives messages from outside the cell  Cell communication is key for homeostasis! Receptor Protein

 Cholesterol  Lipids that prevent freezing  Helps membrane remain fluid (flexible) Cholesterol

 All cells exist in a liquid environment.  The cell membrane must keep the cell’s internal environment constant. (homeostasis)  The cell membrane regulates the movement of molecules in and out of the cell.  Insulin maintains homeostasis

 Passive transport—the movement of materials across the cell membrane without the use of energy

 Diffusion—the movement of molecules from an area of high concentration to an area of low concentration.  Substances will move toward the area where it is less concentrated until it is evenly distributed.  Equilibrium—When the concentration of a substance on both sides of the cell membrane is the same.

 The concentration gradient is the direction particles move in order to reach equilibrium. The concentration gradient is always from high concentrations to low concentrations.

 Facilitated diffusion—When molecules are too large,channel proteins embedded in the cell membrane facilitate, or help, the diffusion of specific materials across the cell membrane.  There are hundreds of different channel proteins that allow specific substances across the cell membrane. Ex: Channel proteins help glucose molecules move into a cell - they are too big to fit in between the lipid bilayer

 Osmosis—The diffusion of water through a selectively permeable membrane.  Water will move across the membrane until equilibrium is reached.

 Isotonic solution—When the concentrations of water and dissolved material (solute) are the same on both sides of the membrane.  Equilibrium has been reached in an isotonic solution.  Water will continue to move in both directions across the membrane but there is no net movement of water.

 Hypertonic solution—”above strength” When there is a greater amount of solute outside of the cell than inside the cell.  Water will move out of the cell until equilibrium is reached.  Plasmolysis—cell shrinkage due to water loss

 Hypotonic solution—”below strength” When there is less solute outside the cell than inside the cell.  Water will move into the cell until equilibrium is reached.  This can cause an animal cell to swell or even burst if it is placed in fresh water.  Plant cells have cell walls, so are not as vulnerable to bursting.

 Active transport—the movement of materials across the cell membrane against the concentration gradient. Active transport requires energy.

 Remember, active transport requires energy. It involves moving molecules against the concentration gradient.  Movement of molecules from low to high concentrations requires energy.  2 types of active transport:  Molecular (small molecules)  Bulk (larger molecules or clumps of molecules)

 Small molecules and ions are carried across the cell membrane by protein pumps.  Much of the cell’s energy is used transporting molecules from low concentrations to high concentration.  This allows cells to concentrate substances in a particular location and to transport materials against the concentration gradient.

 Endocytosis—”into the cell” When a cell takes in large molecules, clumps of food, or other cells. The cell membrane folds in on itself, forming a pocket.  Phagocytosis—when a cell takes in food or other cells  Pinocytosis—when a cell takes in a large amount of water by pinching its cell membrane off into vacuoles

 Exocytosis—”out of the cell” When cells release large amounts of material. The membrane of the vacuole fuses with the cell membrane, forcing material out of the cell.