Notes on Chapter 6.2 & Notes on Chapter 6.2 & 6.36.3

Movement through the Movement through the MembraneMembrane

Homeostasis Homeostasis

• Examples: Examples: • Body temperatureBody temperature• SweatingSweating• ShiveringShivering• DehydrationDehydration• Over-hydrationOver-hydration

DefinitionDefinition: Process by which : Process by which organisms maintain a relatively organisms maintain a relatively stable internal environmentstable internal environment

A. DefinitionsA. Definitions1. 1. Semi-permeable:Semi-permeable: allows only certain substances to passallows only certain substances to pass Ex: cell membranes and nuclear Ex: cell membranes and nuclear membranesmembranes

2. 2. PermeablePermeable: allows all substances to pass : allows all substances to pass throughthrough

II. SEMI/SELECTIVELY PERMEABLE II. SEMI/SELECTIVELY PERMEABLE MEMBRANEMEMBRANE

3. 3. ImpermeableImpermeable: no substances can : no substances can

pass throughpass through

B.B.Live cell membranes are Live cell membranes are semi-permeablesemi-permeable

D. Cell membrane FunctionD. Cell membrane Function• Regulates the substances that enter and Regulates the substances that enter and

leave the cellleave the cell

D. Cell Membrane Functions Con.’t

• A barrierA barrier• ProtectionProtection• SupportSupport• CommunicationCommunication

Lipid bilayer consists of: phospholipidsLipid bilayer consists of: phospholipids

These are the Parts that Make Up Cell These are the Parts that Make Up Cell MembranesMembranes

• Bilayer = Bilayer = Double layerDouble layer

• ‘‘Head’: Head’: hydrophilichydrophilic

• ‘‘Tails’: Tails’: hydrophobichydrophobic

III. Passive TransportIII. Passive Transport

A. A. DefinitionDefinition: : Movement of molecules into and out of cell Movement of molecules into and out of cell

that requires no energythat requires no energy

B. B. WhyWhy?: ?: Molecules are always in random motion!Molecules are always in random motion!

Will always move from area of high Will always move from area of high

concentration to lowconcentration to low

C. Types of passive transport:

1. Diffusion1. Diffusiona. Movement of ANYTHING from a. Movement of ANYTHING from high high concentration to low concentrationconcentration to low concentration

» Does Does notnot require energy! require energy!

•Examples:Examples:•Food coloring Food coloring •Tea bagTea bag•PopcornPopcorn•PerfumePerfume

2. Osmosis- Water Only!2. Osmosis- Water Only!

a. a. DefinitionDefinition::

- Special kind of diffusion of - Special kind of diffusion of waterwater over over

selectively permeable membraneselectively permeable membrane

- From high concentration to low- From high concentration to low

concentrationconcentration

b. Examples:b. Examples:

Isotonic

97% H2O

Diagram

Where is the most water?

Which way does water go?

Result?

Big words

Examples

97% H2O 97% H2O

Same

Inside and outside

Even, same concentration overall

“dynamic equilibrium” “homeostasis

contact lens solution,

HypotonicDiagram

Where is the most water?

Which way does water go?

Result?

Big words

Examples

92% H2O 97% H2O

Outside

Inside

Burst, get bigger; firm

“plasmoptysis”- to burst; “turgid”- get firm; “turgor pressure” :pressure inside plant cells to help stand upright

Distilled water

Paramecium

HypertonicDiagram

Where is the most water?

Which way does water go?

Result?

Big words

Examples

97% H2O 80% H2O

Inside

Outside

Smaller, shrink, go limp

“plasmolysis”- to wilt, shrivel, loss of pressure “flaccid”- go limp

Candy, sugar, salt on bushes/grass, gargle with salt water

Hypertonic

3. Facilitated Diffusion3. Facilitated Diffusion

a.a. DefinitionDefinition: :

Uses proteins in cell membrane to escort

larger molecules across, from area of high

concentration to low.

b. Ex:b. Ex:» Alcohol, HAlcohol, H22O, small lipids O, small lipids

» Allows in bigger moleculesAllows in bigger molecules» No energy required!No energy required!

IV. Active transportIV. Active transportA. A. DefinitionDefinition:: movement of molecules across a movement of molecules across a membrane membrane requiring energyrequiring energy; ; from from LOWLOW to to HIGHHIGH concentration! concentration!

B.B.TypesTypes Endocytosis- materials come into cell Exocytosis- materials leave cell

V. Concentration GradientV. Concentration Gradient Explanation: Explanation:

measurement of how the concentration of measurement of how the concentration of

something changes from one place to another something changes from one place to another

A. A. Passive TransportPassive Transport: :

molecules go molecules go DOWNDOWN concentration gradient from concentration gradient from

HIGHHIGH to to LOWLOW concentration concentration

B. B. Active TransportActive Transport: :

molecule go molecule go UPUP concentration gradient from concentration gradient from LOWLOW

to to HIGHHIGH concentration concentration