Organic molecules

Characteristics & Properties

Organic chemistry is the chemistry of Carbon

Organic molecules contain

• Backbone of Carbon atoms -C-C-C-C-C-C- C
• Functional groups containing C, H, O, N, P, S

Functional groups See Fig. 4.10

Functional groups

• are attached to carbon backbone
• give molecules different properties
• is this molecule soluble in water?

Isomers, see Fig. 4.7

• Two or more compounds may have different structures, called isomers
• glucose, galactose, fructose, mannose are isomers of six carbon sugars with the formula C₆H₁₂O₆.

Polymers

• a large molecule made from many similar small molecules called subunits or monomers

Subunits are connected by covalent bonds formed by condensation or dehydration reactions (remove water), See Fig. 5.2a

Polymers can be broken into subunits by adding water in hydrolysis reactions, See Fig. 5.2b

Four major classes of organic compounds in organisms

For the classes of organic compounds, remember
Elemental composition
Types of functional groups
Functions for organisms
Do not need to memorize structures

Carbohydrates

• Subunits are sugars
• Contain C, H, O in ratio of 1:2:1
• (CH₂O)_x such as C₆H₁₂O₆
• Functional groups are -OH & C=O (Hydrophilic ?)
• Sugars typically contain 3-8 C

Glucose is a 6-C sugar, See Fig.5.4

Functions of Sugars (monosaccharides)

• provide energy - readily broken down to release energy
• serve as building blocks of other molecules (Disaccharides, Polysaccharides)

Disaccharides

Polysaccharide - polymer of sugars

Functions of polysaccharides

• Long term storage of sugars (energy), See Fig. 5.6
• Starch - polymer of glucose in plants, bond between C-1 and C-4
• Glycogen - polymer of glucose in animals, more branched than starch
• Structural elements such as cell walls in plants -
• Cellulose - polymer of glucose, bond between C-1 and C-4 is different, See Fig. 5.7
• Cellulose - major structure of cell wall, See Fig. 5.8

Lipids (fats)

• Complex group of molecules
• Contain primarily C & H, less O
• (may contain other elements, P, N)
• Hydrophobic - not soluble in water
• Types of lipids: neutral fat (triacylglycerol), phospholipids, steroids

Neutral fats (Triacylglycerols)

• composite molecules - composed of two types of molecules - glycerol & fatty acids
• Glycerol - 3-C with hydroxyl functional groups
• Fatty acid - long chains of C & H (14-22 C) with a carboxyl group on one end

Synthesis of a neutral fat, See Fig. 5.11 a & b

Fatty acids, See Fig. 5.12

• Saturated - no double bonds
• HOOC-CH₂-CH₂ -(CH₂)_n-CH₂ -CH₃
• Unsaturated - contain 1 or more double bonds
• HOOC -(CH₂)_n -CH =CH -(CH₂)_n -CH₃

Fatty acids

• Unsaturated fatty acids melt at lower temperatures than saturated fatty acids - may be oils
• Plant fats are typically more unsaturated than animal fats

Functions of neutral fats

• Energy storage - higher amount of energy/gram in fats than in carbohydrates - animals, seeds
• Insulation of warm-blooded animals
• Cushion internal organs

Phospholipids

• Similar to neutral fats in that they are composite molecules
• Contain glycerol, 2 fatty acids, and phosphorylated alcohol
• Contain C, H, O, P (sometimes N)

Phospholipids

• Fatty acids are nonpolar, hydrophobic
• Phosphorylated alcohol is ionic, hydrophilic
• Part of molecule associates with water, part does not

Phospholipid, See Fig. 5.13

Function of Phospholipids

• When placed in water, phospholipids associate to form micelles or bilayers which allow hydrophobic fatty acid side chains to avoid water, See Fig. 5.14
• Phospholipid bilayers form structure of most biological membranes (will discuss more in membranes)

Steroids

• Third type of lipid includes steroids
• Have complex ring structure, contain C, H, little O
• Functions
• Stabilize membranes - cholesterol
• Chemical messengers - sex hormones, (testosterone, estradiol)