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CELL MEMBRANE & TRANSPORT

CELL MEMBRANE & TRANSPORT. PRE-AP BIOLOGY. CELL MEMBRANE. Separates cell contents from the environment Composed of 2 groups Phospholipids Head with 2 tails Phosphate group & lipid HEAD: polar, attracts hydrogen molecules (hydrophilic) TAIL: non-polar; repels water (hydrophobic)

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CELL MEMBRANE & TRANSPORT

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  1. CELL MEMBRANE & TRANSPORT PRE-AP BIOLOGY

  2. CELL MEMBRANE • Separates cell contents from the environment • Composed of 2 groups • Phospholipids • Head with 2 tails • Phosphate group & lipid • HEAD: polar, attracts hydrogen molecules (hydrophilic) • TAIL: non-polar; repels water (hydrophobic) *Grease on hands (need soap) -The pushing & pulling (repelling/attracting water) forms a layer of phospholipids: LIPID BILAYER • Proteins • Located within the layer & act as passageways for some things to pass • Example: food, wastes

  3. LIPID BILAYER • Not firm or continuous • More fluid • Non-polar zone keeps particles from getting into the cell: “barrier” • Phospholipids float within bilayer • Example: light oil or a soap bubble

  4. FLUID MOSAIC MODEL • Components of membrane are fluid or constantly moving • Fluid property allows it to seal itself if broken • Arrangement of phospholipid & protein molecules resemble the tiles of a mosaic art

  5. CELL MEMBRANE IS SIMILAR TO A DOOR • PROTEIN=LOCK • THINGS THAT CAN CROSS=KEY • EVERYTHING MOVES FROM HIGH CONCENTRATION TO LOW CONCENTRATION

  6. CELL MEMBRANE: LIPID BILAYER

  7. PASSIVE TRANSPORT • Movement of substances through a cell’s membrane without using energy • Diffusion a. Water molecules move quickly & randomly b. Movement from high # to low # water molecules c. CONCENTRATION GRADIENT d. Once all molecules have diffused throughout the solution, equilibrium is reached 1. Solute: dissolved substances 2. Solvent: dissolves solute 3. Solution: mixture of solutes & solvents **Oxygen in, Carbon dioxide out; Kidney dialysis

  8. PASSIVE TRANSPORT 2. Osmosis a. Diffusion of water molecules across a selectively permeable membrane from high to low concentration of solutes b. Water molecules accumulate on one side & create pressure, can be great enough to burst cell c. Osmotic pressure 1. increased water pressure resulting from osmosis 2. strong cell wall can withstand pressure

  9. PASSIVE TRANSPORT 3. Facilitated Diffusion a. Diffusion through selective pores b. No energy used c. Example: glucose moves into most cells by facilitated diffusion HOW? -Glucose is not lipid soluble, too large for membrane channels -Channels do NOT change -Carrier molecules change shape so that glucose can be ‘carried’ across membrane -Once released, glucose’s original shape returns -Insulin facilitates glucose movement

  10. P.T. (cont.) 4. FILTRATION -Separation of solids from liquids -Molecules forced through a membrane a. Filter Paper: water is forced through a porous membrane (paper) -Example: coffee filter -Capillaries release water & small dissolved substances through pores -Larger particles (protein) not released -Movement driven by blood pressure -Proteins retain water=causing occasional edema due to overproduction of tissue fluid (edema=swelling)

  11. RELATING TO OSMOSIS • Hypertonic: Osmostic pressure of solution is greater than that of body fluid (more solutes) • Example: eating country ham, salt on a slug • Isotonic: Osmostic pressure of solution is greater than that of body fluid (equal solutes) • IV Solution • Hypotonic: Osmotic pressure of solution is lower than that of body fluid • Slug in example above • Hyper: cells lose water & shrink • Hypo: cells gain water & swell

  12. ACTIVE TRANSPORT • Uses energy to transport a particle through a membrane against a concentration gradient (low to high) • Transports molecules that the cell needs to survive (very little on the outside of the cell) • Needs energy to cross, cannot diffuse • Example: food, molecules

  13. ACTIVE TRANSPORT (cont.) • Sodium-Potassium Pump • Most important energy-using process in your body • Over 1/3 of energy used by a human cell, that is not dividing, is used in this pump • Nerves use this pump to send signals through the body • Also transports food molecules

  14. ACTIVE TRANSPORT (cont.) 2. Endocytosis a. Larger meal b. Engulfs particle c. Requires energy d. Vesicle forms & transports food e. 2 types -Phagocytosis *Cell eating *Cell takes in solids rather than liquids *Ex: White blood cell engulfing bacteria (vesicle forms around bacteria & decomposes, which expels it) -Pinocytosis *Cell drinking *Cell takes in liquid & a vesicle forms to hold the liquid *Liquid eventually becomes part of the cytoplasm (supplying proteins & nutrients) Phagocytosis & Pinocytosis engulf molecules near cell membrane

  15. A.T. (cont.) 3. EXOCYTOSIS a. Dumping of wastes out of the cell (through the vesicle) -Vesicle fuses with cell membrane & expels wastes -Example: Gland cells secrete hormones into the bloodstream

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