CH 5 BIO

Membrane structure

• Hydrophilic head

• Hydrophobic tail

Fluid mosaic model

describes the membrane as a “mosaic of proteins” floating in or on the lipid bilayer, like boats on a pond

Fluid mosaic model 4 parts

• Phospholipid bilayer

• Transmembrane proteins

• Interior protein network

• Cell-surface markers

cell surface markers

glycoproteins and glycolipids that help cells recognize “self” from “non-self”

3 classes of lipids

• Glycerol phospholipids

• Sphingolipids

• Sterols

Glycerol phospholipids

• Diverse

• Lipid head

• Tails

  • function: cell stability and permeability

Sphingolipid Structure

• saturate hydrocarbons

Sterols

• are chains of carbon rings with hydroxyl group

• Cholesterol most common sterol

Cholesterol

impacts membrane fluidity

High temps: cholesteral will reduce fluidity to stop the membrane from becoming overly flluid.

Low Temp: cholesterol disrupts the tight packing of phospholipids which prevents membrane from becoming too stiff

Factors that influence membrane fluidity

• Saturated vs unsaturated fatty acids

• Temprature

• Desaturase

• Composition of lipids present

Diverse functions of protein

• Transportation, selective permeable

• Enzymes; attach to the surface

• cell surface recepters, detec chemical signals from other cells

• Cell surface idenity markers: act as ID tag

• Cell to cell adhesion protein:

• Attachment to cytoskeleton

Membrane pores

• nonpolar regions

• B barrel

• Polar

  • allow water and small polar molecules to pass though the membrane

Passive transportation

• simple diffusion/ facilitated diffusion

• From high to low concentration

Active transportation

• moves against concentration gradient

• energy required

Hypotonic

cell has low water and high solute, cells about to burst

Hypertonic

cell has high water and low solute, cells deinflated

Osmotic pressure

force needed to stop osmotic flow

Sodium Potassium pump

moves 3 Na+ ions out the cell for every 2K + ions

• atp needed

• Phosphorylation addition of P is required during this process

Coupled Transport

• Glucose— Na+ symporter

• ATP indirectlyy

• binding sites for NA+ and glucose

Endocytosis

cell moves particles into the cell, requires energy

Types of endocytosis

• phagocytosis: cell takes paticulate matter

• Pinocytosis: cell takes extracellular fluid

• Receptor mediated endocytosis

Exocytosis

When cell moves particles out of the cell, requires energy

Receptor mediated endocytosis (REM) function

• aka clathrin-dependedent endocytosis

• internalize macromolecules in eukariotic cells

Dysfunction of REM can lead to

Familial Hypercholesterolemia. causes plaques inisde arteries leading to heart attacks