Module 9 Flashcards
Cell Membranes
Composition of cell membranes
Lipid Bilayer
Phospholipids
Glycerol backbone attached to a phosphate group of 2 fatty acids
Phosphate head
Hydrophilic and polar
H-bond with H20
Amphipathic
Both hydrophobic and hydrophilic ends
Hydrophilic Heads
Outside surface, interacts with H20
Hydrophobic Tails
Isolated from contact with H20
Liposomes
When phospholipids are placed in H20 with a pH of 7, they spontaneously form a cell shape
Dynamic Cell Membranes
Lateral movements of lipids and other components within the membrane
Dynamic membrane allows what
VESICLES to easily detach and rejoin, cells to change SHAPE and cells to ENGULF other cells and particles
How do phospholipids move
Move with their tails interacting
laterally with the plane of the membrane
Rapidly
How can Lipids move
Rapidly around their vertical axis, spinning around
Fatty acid rails flex and bend
What influences the membrane fluidity
Composition of the membrane
Longer fatty acid tails= less fluid
NUmber of C-C bonds in the fatty acids tails
Why are longer fatty acid tails less fluid?
Longer tails= more surface area for Van der Waals bonding with other tails, holding each other in place
What makes the membrane less fluid
More bonding and interactions between fatty acid tails.
What type of fatty acids have stronger Van der Walls, why?
Saturated fats have stronger Van Der waals
They are straight and able to pack more tightly –> More stable, less fluid
Have one or more C-C double bonds
Unsaturated fatty acids
Cannot pack as tightly because of weaker Van der Waals; less stable
What kind of fat is Animal Fat
Saturated, less fluid
solid at room temp
What kind of fat is plant fat
Unsaturated, fluid
Liquid at room temp
30% of membranes mass
Cholesterol; inserts itself into the lipid bilayer
Is cholesterol hydrophilic or hydrophobic
BOTH
Amphipathic
High temp effect on fluidity
Increased fluidity
High temp effect on fluidity with the presence of cholesterol
Decreased fluidity, pulling phospholipids closer together
How is homeostasis maintained by cholesterol
Prevents dramatic transitions in fluidity as temp increases
Lipid Rafts
Defined patches of lipids that are assemble together
Are cell membranes always uniform
NO
Functions of protiens
Transport molecules
Pass electrons to harness energy for photosynthesis and CR
Enzymes
Anchor other proteins to maintain cell structure and shape
What accounts for 50% of mass of RBC membranes
protiens
Transport protiens
Move ions and other molecules across the membrane
Receptor protein
Allow the cell to receive SIGNALS from the environment
Integral membrane proteins
PERMANENTLY ASSOCIATED with cell membranes
-transmembrane proteins
Transmembrane proteins
Span entire lipid bilayer
What happens if you try to remove an integral protein
Destroys the membrane
3 regions of integral membrane proteins
2 hydrophilic regions 1 hydrophobic region
2 Hydrophilic regions on integral membrane proteins
Protrude from each face of the membrane in contract with the aqueous environment inside and outside the cell
Hydrophobic region
Spans the hydrophobic interior of the membrane
Peripheral membrane proteins
TEMPORARILY associated with the lipid bilayer or integral membrane proteins
Easily removed, leaving membrane unharmed
