part 2 Flashcards
Functions of the Plasma Membrane
-gatekeeper of the cell/selective barrier -defines boundaries of cell -controls what moves in and out -governs interaction with other cells
The structures of the Plasma Membrane
-98% lipids —75% phospholipids (forms a bi-layer) —20% cholesterol —2% Proteins
Transmembrane Proteins
penetrates into the phospholipid bi-layer
Peripheral Proteins
adheres to intersurface of membrane
Phospholipid
amphiphatic molecule that arrange themselves in a bi-layer with hydrophobic phospate containing heads facing outside of cell or inside -hydophobic tails are inside the cell to avoid H2O
Receptor protein
a receptor that binds to chemical messengers such as hormones sent by other cells
Enzyme (membrane protein)
an enzyme that breaks down as chemical messenger and terminates its effect
Ion Channel
A channel protein that is constantly open and allows ions to pass into and out of the cell
Gated Ion Channel
A gated channel that opens and closes to allow ions through only at certain times
Cell-Identity marker
a glycoprotein acting as a cell-identity marker distinguishing the body’s own cells from foreign cells
Why is plasma membrane a selective barrier?
Because of chemical and structural nature of phospholipid bi-layer. Hydrophobic core- only lipid soluble molecules and some small molecules are able to pass through
What can pass through cell membrane?
Water and lipid soluble substances Gases
What happens if large or charged molecules need to enter/exit?
Need a carrier or vesicle
Types of Passive Transport:
DOESN’T NEED ENERGY filtration diffusion osmosis facilitated diffusion
Types of Active Transport:
NEED ATP active transport endocytosis extocytosis
Filtration:
-movement of materials between cells (NOT THROUGH MEMBRANE) -movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system. –Filtration is seen in blood capillaries where blood pressure forces fluid through gaps in capillary wall
hydrostatic pressure
blood pressure with capillary vessels the pressure exerted
Diffusion
movement of particles from higher concentration to lower concentration -movement until equilibrium is reached
In passive transport, substances diffuse _________ their concentration gradient
Down
Factors that affect diffusion rate
- Temperature increase–> diffusion rate increase 2. Steepness of concentration gradient–> diffusion rate increases 3. Membrane surface are increase–> diffusion rate increases 4. Membrane permeability increases–> diffusion rate increases 5. Molecular weight increases–> diffusion rate decreases
Facilitated Diffusion
for molecules that are too large to pass through membrane -requires a carrier -NO energy needed because substance moves down concentration gradient
Osmosis
-net flow of H2O across membrane -from high [H2O] to low [H2O] or flow from low [solute] to a high [solute]
