Chapter 3: Organic Compounds

AP Biology

Organic Compounds

Carbon atoms covalently bonded to each other forming the backbone of the molecule

More than 5 million Hydrocarbons can be produced in a wide

variety of shapes Many organic compounds are large

macromolecules

Properties of Carbon

4 valence electrons Form 4 covalent bonds

Can bond to another Carbon Or another element

Carbon-Carbon bonds are strong Not limited to single bonds (C-C)

Can form double (C=C) or triple (C=C) bonds

Properties of Carbon

Carbon Chains can be: Unbranched Branched Rings

Do not form in a single plane 3-D Symmetrical

Properties of Carbon

Freedom of rotation around each carbon-carbon single bond Organic molecules are flexible Variety of shapes

Can link together in variety of patterns creating even wider variety of shapes

Isomers

Compounds with the same molecular formula but different structures Different properties Different names

Cells can distinguish between isomers

Functional Groups

Change the properties of organic molecules

Participates in chemical reactions Replace a hydrogen P. 46 - 47

Functional Group Name of compounds Functions

Hydroxyl -OH Alcohols hydrophilic and polar

Aldehydes (when the =O

occurs at the end of chain)

Carbonyl -CO Ketones (when the =O hydrophilic and polar

occurs in the middle of chain)

Carboxyl -COOH Carboxylic Acids act as acids, donate protons

Amino -NH2 Amines act as bases, pick up protons

from acids

Macromolecules Important to Life

Carbohydrates Lipids Proteins Nucleic Acids

Polymers

Most macromolecules are polymers, produced by linking small organic compounds called monomers

This diversity comes from various combinations of the 40-50 common monomers. (These monomers can be connected in

various combinations like the 26 letters in the alphabet can be used to create a great diversity of words).

Carbohydrates

Sugars, starches, and cellulose Used for fuel and structural materials Carbon, Hydrogen, and Oxygen in

1:2:1 ratio Ex.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 5.3

Carbohydrates

1 sugar unit: monosaccharide 2 units: disaccharide many sugar units: polysaccharide Pentoses – 5 carbon sugars

Deoxyribose Ribose

Monosaccharides

Simple sugars 3-7 carbon atoms Glucose and

fructose Glucose important

energy source for cells

Many are ring structures

Disaccharides

2 monosaccharides combined Examples: sucrose, lactose

Polysaccharides

polymers (long chains of repeating units) of monosaccharides

Starch and glycogen Starch – main storage carbohydrate of plants Glycogen – main storage carbohydrate of animals

Starch Plants store starch within plastids, including

chloroplasts. Plants can store surplus glucose in starch and

withdraw it when needed for energy or carbon. Animals that feed on plants, especially parts rich

in starch, can also access this starch to support their own metabolism.

Cellulose Most abundant polysaccharide 50% or more of all the carbon in plants Humans cannot digest cellulose Symbiotic Relationships - Herbivores

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 5.8

Other Polysaccharides with Special Roles

Chitin External skeletons

Insects Crayfish Other arthropods

Cell walls of fungi Tough structures

Multiple hydrogen bonds

Glycoproteins Carbohydrates +

proteins Outer surface of

cells Protection Allow cells to stick

together Ex. mucus

Lipids

Exception: do not have polymers, just large molecules

Fats or fatlike Insoluble in water (hydrophobic)

Nonpolar covalent bonds Mainly hydrogen and carbon, few

oxygen-containing functional groups

Lipids

Types: Fats Phospholipids Steroids (Cholesterol & Some Hormones) Waxes

Functions of Lipids: Reserve energy storage

2x as much energy/gram than carbohydrates Carbs and proteins can be transformed into fats

and stored in adipose tissue Structural components of cellular

membranes Hormones Insulation Cushioning

Triglycerides (fats) Fatty Acid + Glycerol

Glycerol consists of a three-carbon skeleton with a hydroxyl group attached to each.

A fatty acid consists of a carboxyl group attached to a long carbon skeleton

Fat Molecule - Triglyceride3 fatty acids joined to glycerol

Saturated Fats

Contain max. possible # of hydrogen atoms

No double bonds Solid at room temperature

Animal fat and solid vegetable shortening

Not a dietary requirement

Unsaturated Fats

Liquid at room temperature Include double bonds Monounsaturated – 1 double

bond Polyunsaturated – more than 1

double bond Some are essential nutrients that

must be obtained from food

Saturated vs. Unsaturated Fats

Phospholipids

2 fatty acids + glycerol Cell membranes

Inside = hydrophobic Outside = hydrophilic

Steroids Ring structure with different functional

groups attached Cell membranes Required to make all hormones

Proteins

Complex structures Structure relates to function!

Often, function depends on its ability to recognize and bind to another molecule. Ex. Antibodies, Enzymes

Functions of Proteins (p.59)

Support (keratin for hair and nails & collagen for ligaments, tendons, skin)

Enzymes to catalyze reactions Transport across cell membranes Hemoglobin – oxygen transport Defense from infection Hormones (such as insulin) Cell movement

Proteins

Polymers made of amino acids Amino acids are joined by peptide

bonds Chains are called polypeptides

Amino acids form a wide variety of structures Building blocks for living tissue 20 common amino acids (monomers)

Amino Acids

Plants and bacteria can synthesize all amino acids

Animals can manufacture some of the important amino acids If animals cannot synthesize them, they are

essential amino acids Must be obtained from diet

List of Amino Acids & Functions Amino Acid Structure (Animation)

Protein Structure Different functional groups determine

the amino acid Combination of aa’s determine the protein

One or more polypeptides folded into a complex 3-D structure

Shapes of Proteins

Polypeptide chains are twisted or folded to form a 3-D shape such as: Long fibers Globular – tightly folded into compact,

spherical shape Close relationship between shape and

function

Shapes of Proteins

Primary Structure - sequence of amino acids that form the polypeptide chain

Secondary Structure - Parts of the polypeptide fold into local patterns (alpha helix or pleated sheet) p.63

Tertiary Structure - the overall 3D shape (globular or fibrous) p.64

Quaternary Structure - consists of two or more polypeptide chains or subunits p.65

Changes to Protein Shape

A protein’s conformation can change in response to the physical and chemical conditions.Alterations in pH, salt concentration, temperature, or other factors can unravel or denature a protein.

Nucleic Acids

Informational polymers Contain hereditary information Code that determines what proteins a cell

manufactures DNA (deoxyribonucleic acid)

Makes our genes RNA (ribonucleic acid)

Takes part in process of making proteins

Structure of DNA

5 carbon sugar (deoxyribose) Nitrogen base (adenine, thymine,

guanine, cytosine) Phosphate group

All 3 of these = nucleotide (monomer) Complimentary base pairing: A-T, G-C

Important nucleotides ATP (adenosine triphosphate)

Functions in energy storage Composed of adenine, ribose, 3

phosphates

Table 3-3 p.68-69

Summary of the Important Biological Compounds

Study this table!