Unit 4 Biological Membranes

Unit 4 Biological Membranes

Unit 4 Biological Membranes

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Perhaps the most important organelle of the cell is the plasma membrane. This thin layer performs several functions

The Structure of the Cell Membrane

The Fluid Mosaic Model-

Protein blocks are imbedded in a double layer of phospholipids

Phospholipid-

The membrane-

Membrane Proteins-

1.integral membrane proteins-

2. peripheral proteins-

Proteins are oriented so some domains protrude and others intrude

** Position of the proteins is set by the golgi as it sends vesicles

Summary of the Functions of the Membrane Proteins

Protein Type / Function / Location
Cell Adhesion
Intercellular Gates and Transport Proteins
Anchored Enzymes
Signal Transducing Proteins
Cellular Recognition Proteins
Anchors for Cytoskeleton
Ion Pumps

Movement of Materials Across Membranes-

Varies by size of particles

  1. Largest particles- brought through the membrane by ______

Endocytosis-

Types of Endocytosis

Phagocytosis-

Protist Digestive Cycle

  1. Pinocytosis-

Done by villi of the small intestine

  1. Receptor Mediated Endocytosis-

Problem-

** This is a method for returning membrane material to the ER to replace the vesicle membrane materials constantly budded off

  1. Passive Diffusion Processes- molecule sized particles

Diffusion- defn:

Influences-

*

Forms of diffusion-

  1. osmosis-
  1. dialysis-

Generalities about diffusion of paritcles through most cells-

  1. small polar or non-polar molecules
  1. large polar molecules
  1. ions

+

** In osmotic situations salts don’t cross membranes but water does

Turgor pressure-

Protists deal with osmosis using a ______

Environmental Tonicity-

Tonicity refers to the saltiness of the fluid environment a cell exists in. In nature a similar measurement is salinity

There are three tonic conditions

Hypertonic / Hypotonic / Isotonic
Environment high in salt / Environment low in salt / Environment and cell of equal salinity
Cell loses water / Cell gains water / No net gain or loss of water
Leads to ______ / Leads to ______ / No harm to cell
`
Plant cells in salt water / RBCs in freshwater / Saline solution

Dealing With Tonicity- Ecological Strategies

Saltwater Organisms / Freshwater Organisms
Problems-
/ Problems-

Solutions / Solutions

What about?

Osmoconformers-

Anadromous fishes- ex:

Catadromous fishes- ex:

Categories of Tonicity Tolerance

Stenohaline-

Euryhaline-

Example:

Crassostrea virginicavs Urosalpinx cinerea

EuryhalineStenohaline

33-18 ppt33-26 ppt

Some organic processes based on diffusion-

  1. Facilitated diffusion-

Ex: insulin and glucose (skunk in a crowd)

  1. Carrier Transport Across Membranes- Active Transport

******These process often

Sodium Potassium Pump-

Pump requires ATP, 3Na+ and 2K+ to function

3 Na leave- 2 K enter

Diagram-

Integrated Transport Systems-

How do you get large polar molecules through the membrane when they are too large to fit through the protein passages?

Coupled Glucose Transport-

V. Signal Transducing Proteins

Ligands-

Examples-

General diagram-

 There Are Three Known Classes of Cell-Surface Receptor Proteins:

1.

2.

3.

G-Protein Linked Receptors-

Name comes from ______

Inactive-

Activated -

Enzyme Linked Receptor System-

Ex: tyrosine kinase

** signal proteins in this case are growth factors, multiple pathways in the cell activate

Ion Channel Receptor System-

Ex: the depolarization gates of neurons

Transduction- Defn:

Insulin activates this way- insulinis the signal- the cascade flows into the cell and activates glucose absorption and amino acid pathways

______enzymes transfer the P from ATP to each step along the way to allow motion

______ remove the P at the end of each step to deactivate step

\

Calcium Release and IP3

Where?-

Steps-

1

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