biological membranes Flashcards
what is the fluid mosaic model
theory of cell membrane structure with proteins embedded in a sea of phospholipids
what is a glycolipid
lipid/ phospholipid with a chin of carbohydrate molecules attached
what are cell membranes
partially permeable barriers
how do substances pass through the cell membrane
-some diffuse through membrane
-some dissolve in the lipid layer and pass through
-other substances pass through protein channels or are carried by carrier proteins
what are some roles of the plasma membrane
-seperates the cell components from its external environment
-regulates transport of materials in and out of the cell
-may contain enzymes involved in metabolic pathways
what is simple diffusion
movement of particles from a high concentration to low
what is facilitated diffusion
movement of particles from a high concentration to low using a channel protein or carrier protein
factors that affect diffusion
-size diffusing molecule
-surface area
-temperature
-diffusion distance
-concentration gradient
what is active transport
substances move across a biological membrane against a concentration gradient, relying on the cell’s metabolic energy
what is endocytosis
how large substances are brought into the cell
what is exocytosis
how large molecules are exported out the cell
how are large molecules passed through the cell via bulk transport
a vesicle containing the molecule fuses with the plasma membrane. ATP is required
what is pinocytosis
cell engulfs the liquid
what is phagocytosis
cell engulfs solid matter
what happens when the temperature of the plasma cell membrane decreases
-saturated fatty acids are compressed
-when unsaturated acids compress the kinks in their tails push adjacent phospholipids molecules away- this maintains fluidity
-proportions of unsaturated and saturated fatty acids in a cell membrane determine the fluidity at cold temp
-cholesterol prevents reduction in membranes fluidity by preventing phospholipids from packing together too close
what happens when the temperature of the plasma cell membrane increases
-more kinetic energy so can move around more
- increases fluidity of membrane
-increases permeability
what does an increase of fluidity of the membrane affect
-the unfolding of the plasma membrane during phagocytosis
-changes the ability of cells to signal other cells by releasing chemicals by exocytosis
what does cholesterol do when an increase temp of plasma membrane
cholesterol buffers the effect of increase of heat as it reduces the increases in membrane fluidity
