Lecture 16 - Mem. I Flashcards
Biological membranes are easily dissociable due to______
Non-covalent bonding between phospholipids.
What is meant by the “fluid structure” of a membrane?
Lipids readily diffuse LATERALLY, but do not flip from inner to outer leaflets (or vice versa).
Describe how micelles are important to biological f(x).
Polar head groups face aqueous environment. The fatty acid tails produce an environment that can “dissolve,” or surround, hydrophobic molecules, like fats.
Most phospholipids form a bilayer instead of a micelle. Why?
Though both are driven by hydrophobic forces, most phospholipid fatty acid tails are too bulky to fit in a micelle interior (most micelles
Between FA tails, there are _______ interactions.
van der Walls
There are _____ and _____ forces between water and polar heads.
Hydrogen bonding; electrostatic
Hydrophobic interactions lead to these three “major consequences” in membrane formation.
1) lipid membranes are extensive
2) membranes close on themselves
3) membranes are self sealing (E* favorable)
The cholesterol ring structure produces (increased fluidity/stiffness) in a plasma membrane.
Stiffness
The hydrocarbon tail associated with a cholesterol molecule produces (fluidity/stiffness) of a membrane.
Fluidity (hydrophobic interactions)
In plasma membrane permeability (w/o any channels/transporters), what molecules readily diffuse?
Water (small, no net charge, high [ECF])
In plasma membrane permeability (w/o any channels/transporters), what molecules do not readily diffuse?
Large, charged molecules
Integral membrane proteins 1* interact with the PM by _______.
Hydrophobic interactions.
Integral membrane proteins can be removed from the PM by _______.
Dissociation of the membrane through detergents (disrupts Hydrophobic interactions).
Peripheral proteins are bound to the membrane by _____ and ______ interactions.
Electrostatic; hydrogen-bond
Peripheral proteins are dissociated from the membrane by ____ and _____.
- pH changes (changes the side chains of the AAs interacting with polar heads)
- salts (interact with the water in solution, causing dissociation and “salting out”)
Why are alpha helices the most common membrane spanning motif?
Alpha helices are very flexible (important in the fluid/pliable PM) and have OUTWARD facing hydrophobic R groups due to the helix
These proteins are covalently linked to the PM.
Lipid linked proteins
Phospholipids that are bound to proteins via sugar linkages.
GPI (glycosyl phosphotidylinositol) linked proteins
What critical membrane proteins are found attached by GPI linkages?
Cell adhesion molecules
Location of oxidative phosphorylation in the mitochondria.
Inner mitochondrial membrane
Site of TCA cycle and fatty acid oxidation
Mitochondrial matrix
Which mitochondrial membrane is highly permeable to most ions? Why is this important?
Outer membrane. Important for substrates to be able to readily diffuse.
Explain the driving force behind lipid bilayer formation.
The amphipathic nature of phospholipids (polar head, non-polar tail) promotes formation. The polar heads face themselves toward the aqueous environment, and fatty acid tails form a hydrophobic area.
