Biochemistry EXAM Chapter 11

Membrane Structure and Dynamics

Membranes are Barriers Membranes are highly selective permeability barriers –Control flow of information between cells and environment –Some generate signals –Energy conversion processes carried out by membranes photosynthesis

Dynamic structures in which proteins and lipids diffuse rapidly in the plane of the membrane –Unless restricted by special interactions Rotation of lipids from one face of a membrane to the other is usually very slow Degree of fluidity of a membrane partly depends on the chain length of its lipids and how unsaturated the fatty acids are Continued…

Common Features Closed boundaries between compartments Made of lipids proteins and carbohydrates Hydrophilic and hydrophobic moiety Electrically polarized Lipids fuel molecules, energy stores, signal molecules, and components of membranes Major kinds: phospholipids, glycolipids, cholesterol

Phospholipids Abundant in all biological membranes Contain even number of carbon atoms Glycolipids Sugar containing lipids Cholesterol evolved after earths atmosphere became aerobic Plasma membranes of eukaryotic cells are usually rich in cholesterol

Chapter 10 Sugars and Polysaccharides

Monosaccharides Basic units of carbohydrates –Simplest form of sugars Classification classified according to the chemical nature of their carbonyl group and the number of their C atoms Smallest monosaccharide has 3 carbon atoms, called triosis D-glucose is the only aldose (type of monosaccharide) that commonly occurs in nature as a monosaccharide

Polysaccharides Complex carbohydrates Made of chains of monosaccharides linked together by glycosidic bonds Structure categorized into two broad groups Cellulose Chitin

Categories of Polysaccharides Cellulose Component of plant cell walls Fully permeable to water and solutes –Ideal for allowing substance out of cell Most abundant organic substance in the living world Chitin Closely related to structure of cellulose Found in the cuticles of arthropods in sponges, molluscs and annelids. Can also be found in the cell walls of most fungi and in some green algae.

Functions of Polysaccarides Can be used as energy stores –Large and insoluble in water –Fold into compact shapes –Easily converted to needed sugars Two ways Polysaccharides are used as energy stores: Glycogen found in nearly all animal cells and in certain protozoa and algae In humans it is stored in the liver and muscles –main form of stored carbohydrate in the body, –reservoir of glucose for when the body is being starved of food Starch Similar to glycogen Found in plant cells, protists and certain bacteria

The End