Main types of organic molecules

Transcription

1 Main types of organic molecules Carbohydrates Proteins Nucleic acids Lipids Typical composition of organisms by mass CARBOHYDRATES carbon chain with equal numbers of OH and H and a few carbonyl general formula "CH 2 O" Includes: monosaccharides (simple sugars) and polysaccharides (complex carbohydrates) 1

2 Monosaccharides Simple sugars small chains or ring structure, with H, OH, and one =O Triose, tetrose, pentose, hexose sugars name depends on number of carbons in the chain Sugars may be aldose or ketose depending on whether aldehyde or ketone The structure and classification of some monosaccharides Monosaccharides, continued Important as fuel for energy metabolism (glycolysis, cellular respiration) Building blocks (monomers) for polysaccharides such as starch, cellulose Monosaccharide example: glucose 2

3 Glucose An aldose hexose C 6 H 12 O 6 Primary fuel for cells Linear and ring forms (structural isomers) Polysaccharides polymers (chains) of monosaccharides condensation reactions link monosaccharides hydrolysis reactions separate them 3

4 Polymers Large molecules built from chains of smaller molecules (monomers) Important polymers include Polysaccharides (polymers of ring-form hexose sugars) Proteins (polymers of amino acids Nucleic acids (polymers of nucleotides) Condensation reactions make polymers from monomers Hydrolysis reactions take polymers apart 4

5 Example of a condensation (or dehydration ) synthesis the disaccharide maltose formed from two glucose monomers by 1-4 linkage By the way names for short chains: Mono-, di-, tri-, tetra-, penta-, etc. and oligo- Functions of polysaccharides 1. Fuel storage - small molecules such as glucose affect the osmotic concentration of body fluids must be sequestered to store in large quantities 2. Structural long molecules used to toughen and support cells and tissues Glucose storage polysaccharides starch in plants and glycogen in animals Both are polymers of the glucose isomer α-glucose Helical filaments, differ in branching pattern. 5

6 Alpha-glucose α and β glucose are structural isomers of glucose Beta-glucose Storage polysaccharides Structural polysaccharides Cellulose is a polymer of β-glucose. Plant cell-walls Most abundant (greatest mass quantity) of any organic molecule on earth Straight chains cross-linked by hydrogen bonds. 6

7 The arrangement of cellulose in plant cell walls Starch and cellulose structures Starch Cellulose 7

8 Structural polysaccharides, continued Chitin cell walls of fungi, exoskeletons of arthropods Tough, resistant to digestion Similar to cellulose but with acetylamino attached to each glucose: -NH-CO-CH 3 Chitinase - enzyme to break down chitin produced by certain microorganisms and plants but not animals Cellulose aminoacetyl Chitin If you thought that was exciting wait till you hear about LIPIDS! 8

9 LIPIDS Diverse molecules, grouped mainly because of hydrophobicity Mostly hydrocarbon: few polar functional groups Types of lipids include fatty acids, triglycerides, waxes, phospholipids, and steroids Fatty acids Carboxyl group at one end of a long hydrocarbon tail ionized at physiological ph A fatty acid HO O C The sodium salt of a fatty acid ( soap ) O O C amphipathic Hydrophilic Hydrophobic 9

10 How Soap works Triacylglycerol (fats and oils) Three fatty acids joined to glycerol. Important energy stores in animalshydrocarbons to be used as metabolic fuel. Fats are H-saturated, have higher melting temperature Oils are H-unsaturated, so have lower melting temperature Saturated and unsaturated fatty acids 10

11 Unsaturated fat Triacylglycerol synthesis 1. Dehydration linkage of a fatty acid to glycerol Triacylglycerol synthesis 2. Completed triacylglycerol molecule 11

12 Phospholipids Two fatty acids plus hydrophilic phosphate head attached to glycerol Amphipathic molecules ionized, hydrophilic head and hydrocarbon, hydrophobic tails important structural functions The structure of a phospholipid Phospholipid functions Cell membranes phospholipid bilayer Water outside cell Water inside cell 12

13 Phospholipid functions Lung surfactant interface between air and moist surface Breakfast cereal additive? Steroids Another class of lipids, but structurally unrelated to FA and triglycerides Example: cholesterol is a component of cell membranes also precursor of steroid hormones, including androgens and estrogens 13