Presentation on theme: "Cell Membranes Osmosis and Diffusion Visi t ww w.w orld ofte ach ing. co m For 100 s of free po wer poi nts."— Presentation transcript:
Cell Membranes Osmosis and Diffusion Visi t ww w.w orld ofte ach ing. co m For 100 s of free po wer poi nts
Functions of Membranes 1. Protect cell 2. Control incoming and outgoing substances 3. Maintain ion concentrations of various substances 4. Selectively permeable - allows some molecules in, others are kept out
Blood-Brain Barrier Allows some substances into the brain, but screens out toxins and bacteria Substances allowed to cross include: water, CO 2, Glucose, O 2, Amino Acids, Alcohol, and antihistamines. HIV and bacterial meningitis can cross the barrier.
Solutions Solutions are made of solute and a solvent Solvent - the liquid into which the solute is poured and dissolved. We will use water as our solvent today. Solute - substance that is dissolved or put into the solvent. Salt and sucrose are solutes.
Methods of Transport Across Membranes 1. Diffusion 2. Osmosis 3. Facilitated Diffusion 4. Active Transport
Methods of Transport Across Membranes 1. Diffusion -passive transport - no energy expended 2. Osmosis - Passive transport of water across membrane 3. Facilitated Diffusion - Use of proteins to carry polar molecules or ions across 4. Active Transport- requires energy to transport molecules against a concentration gradient – energy is in the form of ATP
Diffusion Movement of molecules from an area of high concentration to an area of low concentration. Movement from one side of a membrane to another, un-facilitated
Tonicity is a relative term Hypotonic SolutionHypotonic Solution - One solution has a lower concentration of solute than another. Hypertonic SolutionHypertonic Solution - one solution has a higher concentration of solute than another. Isotonic SolutionIsotonic Solution - both solutions have same concentrations of solute.
Plant and Animal Cells put into various solutions
OSMOSIS We will make an osmo meter to observe osmosis. We use 2 chicken eggs Place them in vinegar over night to remove the shell. Now each egg behaves as a single cell
Procedure Weigh each egg on an electronic scale Egg # 1 weight in grams 70.4 grams Egg # 2 weight in grams 58.7 grams Place egg # 1 in distilled water Place egg # 2 in corn syrup
HYPOTHESIS Write a hypothesis for the two eggs Which egg will shrink and which egg will become turgid (swollen)? Make an initial diagram and observations. Is the egg firm or flaccid? What is the color and size estimate today? Elmhurst College Website
Final observations the next day After incubation of eggs overnight write your final observations. Which egg is swollen and why? Which egg has shrunk and why? Give reasons for each answer. Which solution was hypertonic and which one was hypotonic?
More questions Which egg had endocytosis Which egg had exocytosis and how did you know that these procedures took place in the eggs.
Final observations What was the colour of the eggs? Draw the final pictures of the two eggs.