Biological Membranes Flashcards
What are the properties of a fluid mosaic model
Is a bilayer of amphipathic lipids
Has proteins: integral, peripheral, lipid anchored
Components are mobile
Components can interact
What 4 properties are shared by all membranes
~6 nm thick
Stable
Flexible
Capable of self assembly
What three classes of membrane proteins
Integral
Lipid anchored
Peripheral
What is membrane fluidity determined by
Nature of lipid in the membrane
Temperature
What increases membrane fluidity
Unsaturated lipids
Warming
What decreases membrane fluidity
Cooling
Saturated lipids
What is a transition temperature
The temperature at which the membrane enters a crystalline gel state
Why is membrane fluidity crucial to cell function
Brings balance between ordered (ridged) structure and disordered structure
Mechanical support and flexibility
Dynamic interactions between membrane components
Membrane assembly and modification
Why is cholesterol important in membrane fluidity
Alters packing and flexibility of lipids
What are glycolipids and glycoproteins
Lipids and proteins with carbohydrates attached
Composition of cell membranes can be changed by
Desaturation of lipids
Exchange of lipid chains
What are lipid rafts
Small areas of the plasma membrane that are enriched in certain types of lipids like cholesterol
Describe the properties of lipid rafts
Rafts are relatively ridged
Some membrane proteins accumulate in rafts
May form a functional compartment
What can pass easily across a membrane
Small uncharged mollecules
What cannot easily pass across the mebrane
Large /polar/ charged
Name the 4 basic mechanisms for moving molecules across membranes
Simple diffusion
Diffusion through a channel
Facilitated diffusion
Active transport
What passes by simple diffusion
Very small molecules
Uncharged
Sown a gradient
O2 CO2 H2O
What passes by diffusion through a Chanel
Small charged molecules, ions
Down a gradient
Na+ K+ Ca+ Cl-
What are ion channels formed by
Formed by integral membrane proteins that line in an aqueous pore
What passes through an ion channel
Only one type of ion can pass
Down a conc gradient
Often are gated
What are the 3 types of gated channels
Voltage gated channels
Ligand gated channels
Mechano gated channels
What passes by facilitated diffusion
Compounds bind to integral membrane protein called a facilitative transporter and the change in conformation allows compound to be released on the other side of the membrane
What active transport
Compunds binds specifically to integral membrane and change in conformation allows compound to be released on other side of membrane
Moves against a gradient
What is a glycocalyx
An assembly of carbohydrate groups attached to proteins and lipids on the outside of the plasma membrane
What is the purpose of a glycocalyx
Mediates cell cell and cell EMC interactions
Provides mechanical protection
Serves as a barrier to some particles
Binds regulatory factors
What are the 6 functions of biological membranes
Cell boundary
Define/enclose compartments
Control movement of material into/out of the cell
Allows response to external stimuli
Enable interactions between cells
Provide scaffold for biochemical activities
