Cells Part 3

Fluid Mosaic Model

Double layer of phospholipids w/ embedded proteins

Within the phospholipid bilayer are Polar Heads and Non-Polar Tails

Peripheral Proteins

Attached to inner or outer membrane surface

Intrinsic/Integral Proteins

Embedded IN the membrane

Some move ions or molecules across the membrane

Some attach the membrane to the cytoskeleton

Cholesterol

Embedded in the interior of the membrane

Makes the membrane less permeable to water-soluble substances

Add rigidity

Glycocalyx (Cell coat)

Glycolipids and Glycoproteins on surface of plasma membrane

“Fingerprint” of the cell

Cell membrane

Site for receptors containing glycocalyx

Selectively permeable

Maintains homeostasis

Types of Passive Transport

Simple Diffusion

Facilitated Diffusion

Osmosis

Simple Diffusion

Movement of molecules from areas of high to low concentration

Move until equilibrium is reached

No energy required

Facilitated Diffusion

Diffuse from high to low concentration using a carrier protein

NECESSARY for large molecules and some that are not lipid soluble

Temporarily binds with a carrier protein in the plasma membrane and transported to low concentration

Osmosis

Diffusion of water across a selectively permeable membrane from high to low

No energy required

Types of Osmosis

Isotonic

Hypertonic

Hypotonic

Isotonic

Same concentration of solutes outside and inside

Hypertonic

Shriveling

Solute concentration is higher outside than inside

Water moves OUT of the cell

Low salt outside

Hypotonic

Swelling

Solute concentration is higher inside than outside

Water moves into the cell

High salt outside

Types of active transport

Filtration

Endocytosis

Exocytosis

Filtration

Molecules are forced across selectively permeable membranes by hydrostatic or blood pressure

Endocytosis

Bulk movement of materials across plasma membrane into the cell

3 forms of Endocytosis

Pinocytosis

Phagocytosis

Receptor-Mediated Endocytosis

Pinocytosis

“Cell drinking”

Uptake of small droplets of extracellular fluid

small portion of plasma membrane becomes invaginated, surrounds droplets, seals itself, and forms a vesicle (Like snake.io)

Phagocytosis

“Cell eating”

Uptake of large solid particles

Recepter-Mediated Endocytosis (w.i.p)

A receptor on the membrane recognizes a molecule outside the cell and binds with it, resulting in an indentation and forms a vesicle

Exocytosis

Secretory vesicle fuses w/ plasma membrane and releases contents out of the cell

This process adds new membrane material and replaces plasma membrane material lost during endocytosis (Cycle)