chapter 3 - the plasma membrane Flashcards
unit 1 aos 1
the function of the plasma membrane
is selectively permeable, which means that only particular molecules can enter and exit the cell.
the structure of the plasma membrane
is a phospholipid bilayer (arranged in two layers) embedded with proteins, carbohydrates, and cholesterol.
structure of phospholipid
phosphate head
made up of glycerol and a phosphate group.
negatively charged, making it hydrophilic and polar (eg water).
2 fatty acid chains
made up of long chains of carbon and hydrogen.
uncharged, making it hydrophobic and non-polar.
amphipathic molecule
makes plasma membrane stable.
types of protein
integral: permanent part of the membrane
transmembrane: integral proteins that span the entire bilayer
peripheral: temporarily attached to the plasma membrane
function of protein
transport
communication
catalysis
adhesion
structure of carbohydrates
usually in chains that extend outside the cell, rooted in the membrane to lipids (glycolipids) or proteins (glycoproteins).
function of carbohydrates
aids with:
cell-cell communication
signalling
adhesion
recognition of molecules
structure of cholesterol
lipid steroid that embeds itself between the fatty acid tails of the phospholipid bilayer in animal cells.
is replaced with similar molecules in other kingdoms, but are all functionally similar.
function of cholesterol
regulates fluidity of membrane
at higher temperatures, it keeps phospholipids bound together.
at lower temperatures, it stops phospholipids from becoming solid.
the fluid mosaic model
the plasma membrane is fluid because phospholipids continually move laterally (side to side) in the membrane.
the mosaic component of the model comes from the proteins and carbohydrates embedded in the model.
explains:
molecules that make up the membrane are not held static in one place.
many different types of molecules are embedded in the plasma membrane.
diffusion
the movement of particles down the concentration gradient
passive transport
process that doesn’t require energy to move things across the plasma membrane.
simple diffusion
when molecules move from an area of high concentration to an area on low concentration (down concentration gradient)
happens due to kinetic energy stored inside each molecule which causes them to move around and bounce off each other.
leads to even dispersion of the molecules in an area
which molecules can freely diffuse across the plasma membrane?
non-polar and small (like water) molecules
facilitated diffusion
passive movement of molecules down the concentration gradient through membrane bound proteins (proteins channels).
allows large molecules to move between the intra and extracellular environments.
protein channels and carrier proteins both are specific to the molecules they transport and the selective permeability of the plasma membrane.
protein channels
pores or holes in the membrane that let specific substances in