Lecture 2- Cells and Transport

Plasma membran

a dynamic bilayer of phospholipids, with hydrophilic heads facing outward and hydrophobic tails inward. Cholesterol stabilizes membrane fluidity, while integral proteins span the bilayer for transport and signaling, and peripheral proteins attach to the surface for structural and signaling roles. Glycolipids and glycoproteins on the extracellular side aid in cell recognition and communication. This flexible structure allows molecules to move within it, maintaining the membrane's function and integrity.

Intracellular fluid

The water and dissolved substances that fill the inside of cells

Extracellular fluid

all the body's water that's not inside cells

Interstitial fluid

a clear, watery substance that fills the spaces between cells and tissues throughout the body

Diffusion

Nonpolar Lipid soluble, across membrane

Osmosis

Definition: Water across a semi-permeable membrane

Energy source: Chemical gradient

Example: Movement of H2O

Hypertonic solution

1.5% solute 98.5% solvent

Hypotonic solution

0.0% solute 100% solvent

Isotonic solution

0.9% solute 99.1% solvent

Five factors that affect the rate of transport of substances across cell membranes

Active transport

tight junctions

desmosomes

gap junctions

Vesicular transport

Facilitaed diffusion

Polar, Channels & Carriers

Energy source: Chemical gradient

Example: Movement of glucose into cells

Simple diffusion

Energy source: Chemical gradient

Example: Movement of O2 through membrane

Channels & Carriers

Channel proteins and carrier proteins are both transmembrane proteins that move substances across cell membranes