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Transcript
Video from Youtube on Diffusion and osmosis – www.youtube.com/watch?v=AYNwynwaALo Homeostasis Steady state Balance an organism maintains by self regulating adjustments Example: Body Temperature and Heart Rate (blood Flow supply o2 and nutrients) DIFFUSION Process by which molecules spread due to their random movement from an area of high concentration to low concentration Example: when you spray lysol CONCENTRATION GRADIENT Difference in concentration of a substance in a given area MOLECULES move naturally from high concentration to low concentration until equilibrium is reached. Equilibrium means balance or homeostasis Three Ways to increase rate of diffusion: concentration increase pressure Heat (makes molecules move faster) Cell Membrane – regulate molecules – the flow of materials in and out of the cell Permeable – if substance passes through it is permeable to that substance Selectively permeable – only allows some substance through Solution – a mixture of one or more substances dissolved in it Solvent – water Solute – salt Idea: kool aid – water is the solvent and the packet of mix is the solute THREE TYPES OF SOLUTIONS: Hypotonic solution – concentration of solutes in the environment lower than in the cell (H2O moves in) Hypertonic – concentration of solutes in the environment is higher than in cell (H2O moves out) Isotonic solution – equal concentration of solute in cell and environment ( h20 in and out equally) Maintains equilibrium or homeostasis Type of Solutions Type of Solutions If the con cent ratio n of solu te (salt ) is equ al on both side s, the wat er will mov e back in fort h but it won 't hav e any resu lt on the over all amo unt of wat er on eith er side. "IS O" mea ns the sam e The wor d "HY PO" mea ns less, in this case ther e are less solu te (salt ) mol ecul es outs ide the cell, sinc e salt suck s, wat er will mov e into the cell. The cell will gain wat er and gro w larg er. In plan t cells , the cent ral vac uole s will fill and the plan t beco mes stiff and rigid , the cell wall keep s the plan t from burs ting In ani mal cells , the cell may be in dan ger of burs ting, orga nell es calle d CO NT RAC TIL E VAC UO LES will pum p wat er out of the cell to prev ent this. The wor d "HY PER " mea ns mor e, in this case ther e are mor e solu te (salt ) mol ecul es outs ide the cell, whi ch caus es the wat er to be suck ed in that dire ctio n. In plan t cells , the cent ral vac uole loses wat er and the cells shri nk, caus ing wilti ng. In ani mal cells , the cells also shri nk. In both case s, the cell may die. This is why it is dan gero us to drin k sea wat er its a myt h that drin king sea wat er will caus e you to go insa ne, but peop le mar oon ed at sea will spee d up deh ydra tion (an d deat h) by drin king sea wat er. This is also why "salt ing field s" was a com mon tacti c duri ng war, it wou ld kill the crop s in the field , thus caus ing food shor tage s. Isotonic Solution – equal concentration of solute in cell and environment (H2O in and out equally) Osmosis – diffusion of water from areas of greater concentration to lesser concentration Turgor pressure – as water diffuses into a plant cell it exerts a force against the cell wall Plasmolysis – cell shrink Cytolysis – cell bursts Contractile vacuole – some single cell animals in the water use this to pump out the excess water Passive transport – movement across a membrane without use of energy (Diffusion and Osmosis) Active Transport – movement across a membrane with energy Carrier Molecule – proteins which function in transport a. Facilitate diffusion – uses a carrier molecule to speed up diffusion but does not use energy Example: Glucose needs insulin to speed diffusion into cell b. Active transport – uses carrier molecules to go against concentration gradient. Uses energy. MOVEMENT OF LARGE MOLECULES Endocytosis (endo – in)process by which cells engulf substances which are too large to diffuse through the cell membrane a. Phagocytosis – food b. Pinocytosis – liquid Example: ameba white blood cells Exocytosis ( exo-out) movement of large molecules out of the cell Example: wastes Active and Passive Transport video on transport and endocytosisi Review of Terms: A difference in concentration creates a concentration gradient Prefix that means “inside” is endo A word that means “cell” – cyto Prefix that means “outside” – exo Active transport will remove sodium ions, while taking in potassium ions Channel proteins can help move things across the membrane Organelle that helps remove excess water; contractile vacuole The outer boundary of the cell is the membrane