Functions: – Structural support & protection – Helps maintain HOMEOSTASIS – Selective barrier –SEMIPERMEABLE Water, food, oxygen, waste and nutrients are transported through the cell membrane.
Structure Lipid Bilayer = Double layer of phospholipids Each Phospholipid has: – 2 non-polar tails: Hydrophobic (Repels water, Water FEARING) – 1 polar head: Hydrophilic (Attracted to water, Water LOVING) Proteins, carbohydrates, and cholesterol are also in the membrane
Homeostasis The maintenance of stable internal conditions within the cell or organism. The body’s ability to maintain equilibrium BALANCE Conditions within and around organisms are constantly changing (temperature, water, oxygen), so our cells need a way to adjust to the changing conditions.
Semipermeable Some substances can pass across it and others can not Also called “Selectively Permeable” Large molecules such as proteins and sugars don’t pass freely and must be transported into the cell Large molecules such as proteins and sugars don’t pass freely and must be transported into the cell
Passive Transport Allows some particles to move in or out of cell without the use of energy. Using Diffusion
http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/ani mation__how_diffusion_works.html Diffusion- – particles spread from high concentration to low concentration until equilibrium is reached – movement of Solutes (sugar, salt, minerals) – No energy required Concentration Gradient- difference in concentration between two areas across from each other. Molecules will move with the gradient from a high concentration to a lower concentration. “Rolling down a hill doesn’t require energy”
Solutions Solute is the material that is being dissolved (sugar) Solvent is doing the dissolving (water)
Types of Diffusion Simple—unassisted diffusion of small particles or lipid-soluble molecules Simple—unassisted diffusion of small particles or lipid-soluble molecules Osmosis—unassisted diffusion of water Osmosis—unassisted diffusion of water Facilitated diffusion—diffusion with the help of carrier proteins Facilitated diffusion—diffusion with the help of carrier proteins
Osmosis: – diffusion of water from an area of high to low water concentration – Occurs continuously (all the time) in the cell – No energy required
HYPERTONIC solution: 1. Solute concentration outside the cell is higher (less water) 2. Water diffuses out of the cell 3. Cell will shrink cell membrane pulls Plant cell-cell membrane pulls away from the cell wall (wilts) HYPOTONIC solution: 1. Solute concentration greater inside the cell (less water) 2. Water moves into the cell 3. Cell will swell & burst (Lysis) Plant cell-pressure on cell wall increases- (Turgor) ISOTONIC solution: 1.Concentration of solutes is the same inside & outside the cell
Facilitated Diffusion – transport proteins embedded in cell membrane “carries” the substance across the membrane. – Substances like glucose, amino acids, and ions use these – No energy required http://highered.mcgraw- hill.com/sites/0072495855/stu dent_view0/chapter2/animati on__how_facilitated_diffusion _works.html
Cell in Isotonic Solution CELL 10% NaCL 90% H 2 O 10% NaCL 90% H 2 O What is the direction of water movement? The cell is at __________. ENVIRONMENT NO NET MOVEMENT Equilibrium
Cell in Hypotonic Solution CELL 10% NaCL 90% H 2 O 20% NaCL 80% H 2 O (More H 2 0 outside of cell than inside) What is the direction of water movement?
Cell in Hypertonic Solution CELL 15% NaCl 85% H 2 O 5% NaCl 95% H 2 O (More H20 inside than outside) What is the direction of water movement? ENVIRONMENT
Active Transport Movement of substances from a lower concentration to a higher concentration Energy is needed – ATP (adenosine triphosphate) is the source of the energy. Transport goes AGAINST concentration gradient (going up a hill requires energy) Carrier Proteins (Transport Proteins) – Endocytosis – Exocytosis
Carrier Proteins (Transport Proteins) – Use ATP to pump molecules into or out of the cell – Low concentration to high concentration
Endocytosis – Cell membrane folds inward surrounding the material to transport it INTO the cell – Once inside the cell it’s transported to a lysosome
Two Types of Endocytosis Phagocytosis “Cell Eating” Engulfs large materials like bacteria Pinocytosis “Cell Drinking” Engulfs extracellular fluid, including sugar and proteins
Exocytosis – Materials, like waste, are surrounded by a vesicle and transported to the cell membrane – Vesicle fuses with the cell membrane and releases its contents OUTSIDE the cell