AP Bio - 2.3 cell size & 2.4 plasma membranes

Mostly 2.4

Why are cells typically small? (2.3)

Moving materials, such as nutrients and waste, in and out of cells gets more difficult the larger a cell is because of surface area-to-volume ratio

Amphipathic

hydrophilic and hydrophobic

How are phospholipids amphipathic?

hydrophilic phosphate head is polar, and hydrophobic fatty acid tail is non polar

Where are peripheral proteins found?

loosely bound to the surface of the membrane

Traits of peripheral proteins

Hydrophilic with charged and polar side groups

Where are integral proteins found?

Span the membrane

Traits of integral proteins

Hydrophilic with charged and polar side groups, hydrophobic with non polar side groups penetrate hydrophobic interior of bilayer of phospholipids

Ex: transmembrane proteins

What role do embedded proteins play in maintaining the internal environment of the cell?

Transport, cell-cell recognition, enzymatic activity, signal transduction intercellular joining, attachment for extracellular matrix or cytoskeleton

Fluid Mosaic Model

The framework of the cell membranes, structured as a mosaic of protein molecules in a fluid bilayer of phospholipids

Traits of the structure of the Fluid Mosaic Model

Structure is not static and is held together primarily by hydrophobic interactions which are weaker than covalent bonds. Most lids and some proteins can shift and flow along the surface or across the bilayer

Where cholesterol is found

Randomly distributed and wedged between phospholipids in the cell membrane of eukaryotic cells

Function of cholesterol

Regulates bilayer fluidity under different environmental conditions

Function of carbohydrates

Diversity and location of carbohydrates and lipids enable them to function as markers

Glycoproteins

One or more carbohydrate attached to a membrane protein

Glycolipids

Lipid with one or more carbohydrate attached