Osmosis and Diffusion, Cell Biology - Biology - Lecture Slides, Slides for Biology. Alagappa University


Description: These are the lecture slides of Biology. Key important points are: Osmosis and Diffusion, Cell Biology, Cell Membranes, Functions of Membranes, Maintain Ion Concentrations, Selectively Permeable, Phospholipid Bilayer, Fluid Mosaic Model, Blood-Brain Barrier
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Cell Membranes Osmosis and Diffusion

Cell Membranes Osmosis and Diffusion


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


Phospholipid Bilayer


Fluid Mosaic Model


Blood-Brain Barrier

Allows some substances into the brain, but screens out toxins and bacteria

Substances allowed to cross include: water, CO2, Glucose, O2, Amino Acids,

Alcohol, and antihistamines. HIV and bacterial meningitis can cross the barrier. Docsity.com

SolutionsSolutions 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



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 Solution - One solution has a lower concentration of solute than another.

Hypertonic Solution - one solution has a higher concentration of solute than another.

Isotonic Solution - both solutions have same concentrations of solute.


Plant and Animal Cells put into various solutions


Types of Transport


Today’s Lab

We are using dialysis tubing as the cell membrane - It is selectively permeable

The solute is either the eosin starch solution or the sugar solution

What is the solvent?


Membrane PermeabilitySolute is eosin-starch-chloride solution Solvent is Water Indicator for presence of starch is IKI Starch is made of amylose and amylopectin –

amylopectin is insoluble Iodine is not very soluble in water, but with KI it

forms a I3- (triiodine ion) which is soluble. I3- combines with the amylose and the starch

molecule turns blue-black.


Test for Chloride ions

Indicator for presence of chloride ions is silver nitrate, AgNO3 A white precipitate, AgCl, forms if chloride is



Test for Sulfate ions Indicator for the presence of sulfate ions is

Barium chloride, BaCl Barium sulfate, BaSO4 - forms a white

precipitate BaCl + NaSO4 ----> BaSO4 + NaCl


Living Cells

Beet cubes will be used to see the result of boiling and adding alcohol to a live membrane.

Yeast cells are used to see effects of heat Fern gametophytes are used to see result of

putting live cells in solutions of varying tonicity



We will make an osmometer to see osmosis Sugar solution in a dialysis tube is used to

simulate a cell membrane. Various concentrations of solute may be used

around the room.


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