Cell
Cell Diversity
- Types differ in size, shape, sub-cellular components, and functions
General Cell (All Cells)
Plasma Membrane
Flexible outer boundary
-lipid bilayer and proteins constantly changing fluid mosaic
-plays dynamic role in cellular activity
Separates intracellular fluid (ICF) from extracellular (ECF)
–Interstitial fluid (IF)= ECF that surrounds cells
Membrane Lipids
Lipid Bilayer
Phospholipids
Membrane Proteins
-Allow communication with environment
-Most specialized membrane functions
2 Types
-Integral Proteins
-Peripheral Proteins
Integral Proteins
Firmly inserted into membrane
Peripheral Proteins
6 Functions of Membrane Proteins
Look at Diagram Cards
Glycocalyx
“sugar coverings” at cell surface
Cell Junctions
2 types
3 subtypes
Some are "free" EX- blood cells, sperm cells Some bond into communities 3 types: -Tight junctions -Desmosomes -Gap junctions
Tight Junctions
Adjacent integral proteins fuse form impermeable junction encircling cell
-prevents movement
Desmosomes
“Rivets” or “spot-welds” that anchor cells together at plaques (thickenings on plasma membrane)
Gap Junctions
Transmembrane proteins form pores that allow small molecules to pass from cell to cell
-for spread of ions, simple sugars, and other small molecules between cardiac or smooth muscle cells
Plasma Membrane
Cells currounded by interstitial fluid (IF)
-contains thousands of substances; amino acids, sugars, fatty acids, vitamins, hormones, salts, waste products
Plasma membrane allows cell to:
-obtain what is needed from IF
-Keep out what it does not need
Membrane Transport
Plasma membranes selectively permeable -some molecules pass through easily; some do not Two ways substances cross membrane -Passive processes -Active processes
Passive Processes
Diffusion
Molecules to move down or with their concentration gradient (speed of movement is determined by molecule size and temperature
Molecule will passively diffuse through membrane if:
-lipid soluble
-small enough to pass through membrane channels
-assisted by carrier molecule
3 Types of Diffusion
Look at Diagram Cards
Simple Diffusion
Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayer
EX. oxygen, carbon dioxide, fat-soluble vitamins
Carrier-Facilitated Diffusion
Certain lipophobic molecules transported passively by;
-binding to protein carriers
-moving through water-filled channels
Transmembrane integral proteins are carriers
Used when sugars are too large for channels
Channel-Facilitate Diffusion
Watery channels formed by transmembrane proteins
Selectively transport ions or water
Two types:
-Leakage (always open)
-Gateway (controlled by chemical or electrical signals)
Osmosis
Water moves through: -lipid bilayer -specific water channels Occurs when either water or solvent is too high on one side or the other than either: -through impermeable; osmosis occurs until equilibrium reached -through permeable; both solutes and water across membrane until equiilibrium reached
Pressures of Osmosis
Hydrostatic: back pressure of water on membrane
Osmotic: tendency of water to move into cell by osmosis