Cell Membrane Structure and Function (week 2) Flashcards
what is the function of the phospholipid bilayer?
- creates a barrier
- protects intracellular space
- regulates what enters and leaves a cell (semipermeable)
what make up integral proteins?
transport and receptors
function of peripheral proteins
tethering points for cytoskeleton and enzymes
what make up integral proteins?
support and enzyme proteins
function of integral proteins
channel/carriers + receptors
function of cholesterol
- keeps membrane integrity, particularly at high temps
- maintains membrane integrity at more extreme temperature
conditions. - reduces fluidity at extreme high temperatures and increases fluidity at extreme low temperatures
- prevents membranes from being too fluid and too permeable at warmer temperatures.
- separates the phospholipids, preventing them from crystallizing at lower temperatures,
functions of glycoproteins/lipids
cell ID, cell to cell interaction
what happens when you increase cholesterol?
slightly reduces membrane permeability
what are integral proteins
proteins that penetrate the membrane
why are the heads hydrophilic?
phosphates are polar since they are negatively charged
why are the tails hydrophobic?
Since they are composed of hydrogen and carbon atoms, which are non polar
what factors increase membrane permeability/fluidity?
- Increase temperature
- Increase amount of unsaturated bonds
- Make fatty acid tails shorter
- Reduce concentration of cholesterol
what factors decrease membrane permeability/fluidity?
- Decreases temperature
- Decrease amount of unsaturated bonds
- Make fatty acid tails longer
- Increase concentration of cholesterol
passive transport
no ATP needed (high to low concentration to achieve equilibrium)
active transport
ATP needed (low to high concentration gradient)
which types of molecules have the hardest time passing through?
small non-polar molecules and large polar molecules (without a channel)
which types of molecules have the easiest time passing through?
large non-polar (steroid hormones) and small, charged molecules (h2O)
why do ions need a channel?
due to their charge
what is osmosis
movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules, through a cell’s partially permeable membrane
what is diffusion
1.Spontaneous movement of particles from an area of high concentration to an area of low concentration
2. Does not require energy
3. Occurs via random kinetic movement
4. Net diffusion stops when equilibrium is reached
5. Molecules can continue to move, but no net change in concentration
6. Diffusion of one compound doesn’t depend on the diffusion of another compound
isotonic
same concentration as cytoplasm, in equilibrium (no change to cell)
Hypotonic
lower concentration than cytoplasm; cell swells and bursts
Hypertonic
higher concentration than cytoplasm; cells shrink and burst
what are some of the factors that influence that ease by which substances can cross the cell membrane?
solubility (polar vs. non polar), molecular size, charge, presence of channel/carrier
sequence the following in order of what can easily pass to cannot pass through the cell membrane: oxygen, potassium, glucose, water
oxygen, water, glucose, potassium
what substances require move via facilitated transport methods?
ions, polar large molecules (glucose, amino acids, protein-based hormones)
what is facilitated diffusion?
- Allows diffusion of large, membrane insoluble compounds such as sugars, amino acids, and ions across a biological membrane down their concentration gradients
- Does not require energy (passive)
- Highly Selective
- Substance binds to membrane-spanning transport protein - Binding alters protein conformation, exposing the other surface
- Movement rate of particles reaches a max because there are only so many transporter
what are the 3 types of channel variations?
- Uniport (transport of one substance across a membrane
- Symport (Transport of two or more
substances one direction) - Antiport (Transport of two or more substances in opposite directions)
what are the types of ion channels?
leakage, ligand gated, mechanically gated, voltage gated
leakage channels
no stimuli bc they are always open
ligand gated channels
ligand binding
mechanically gated channels
pressure/mechanical change
voltage gated channels
change in membrane voltage
exocytosis (passive)
large wastes or cell products are released from inside to outside a cell
endocytosis (osmosis)
large particles are surrounded by the membrane and taken into the cell
equilibrium (active)
a state reached when particles continue to move but in equal amounts in and out of the cell
kinetic energy
energy of motion/movement (ex: water falling over a waterfall or throwing a football)
potential energy
stored energy (ex: stored in springs of mattresses or stored within bonds of molecule)
Phagocytosis
large particles, ex: bacteria
pinocytosis
anything that is in the extracellular liquid
receptor-mediated endocytosis
specific ligands, ex: cholesterol
