Hydrogen bonding in water is the consequence of water?
polar covalent bonds between hydrogen and oxygen and the bond angle resulting in a dipole
Hydrogen bonding between water molecule results in what?
high MP
High BP
High Surface Tension
hydrophobic effect
tendency of nonpolar molecules to self-associate in water rather than to dissolve individually, driven by the loss of hydrogen bonding and the higher entropic cost of forming a cavity around nonpolar molecules
the hydrophobic is a critical
contributor to stabilizing structure of biological membranes
phospholipid property
ampiphilic
-water loving and water hating
the two principal chemical constituents of membranes
1. lipid - key contributor to barrier characteristic
2. protein - function of membrane
what concept about phospholipids is huge in understanding biological membranes?
self assembly
flippases
ATP requiring enzymes that allow for translational diffusion of phospholipids to occur
-use ATP to flip of PLs from one bilayer to another = NEW BILAYER
lack of translational diffusion is associated with
stability of phospholipid and maintenance of barrier function
Summary of steps in bilayer biosynthesis (3)
1. enzymatic synthesis of phospholipid
2. insertion of phospholipid into cyctoplasmic face of ER
3. distribution of PLs across ER membrane by means of ATP-dependent flippases
the presence of bilayer reduces
free diffusive passage of water by 10,000 fold
water crosses cell membranes or lipid bilayer faster?
cell membrane
-10 to 100+ faster
Integral membrane proteins
-mediate transport of molecules across membrane
-attach cells to neighboring cells or surfaces
-interacting with extracellular molecules to induce intercellular changes
integral membranes have a _____ structure
amphillic
integral membranes reside in
plane of lipid bilayer
Peripheral MPs
- on periphery
-associated with membrane surfaces
- hydrophillic
- weak electrostatic interactions
Peripheral MPs can be removed
by increasing salt concentration
Peripheral MPs critical for organizing
clustering enzymes by one another, facilitating interaction
movement of integral MPs
-laterally diffuse
-cannot flip (hydrophillic heads stay as is)
NOT ALL CAN LATERALLY DIFFUSE (location is key)
Aquaporins originally isolated from
RBCs as contaminent
aquaporins are
integral MPs
moving water across membrane
-3A pore that water can pass protons cannot
what are the physical process the influencethe movement of water (and solutes) acrossthe membrane?
Diffusion & Osmosis
___________ is everything
LOCATION
- where proteins are expressed is critical in defining their impact on cell PSIO