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

Biology

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

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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

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Phospholipid Bilayer

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Fluid Mosaic Model

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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.

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Methods of Transport Across Membranes

1. Diffusion 2. Osmosis 3. Facilitated Diffusion 4. Active Transport

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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

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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

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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.

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Plant and Animal Cells put into various solutions

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Types of Transport

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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?

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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.

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Test for Chloride ions

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

present.

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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

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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

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Osmosis

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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