1. Molecules of Life
Chapter 3

2. Carbon The stuff of life: carbon
Molecules that have primarily hydrogen and carbon atoms are said to be organic
Carbon’s importance to life arises from its versatile bonding behavior – it has four electrons available to bond
Many organic molecules have a backbone that is a chain of carbon atoms

3. Organic Molecules
All living things are made from the same organic subunits – amino acids, fatty acids, nucleotides, and simple sugars
All biological systems are based on these molecules, the details of the molecules differ among organisms

4. Carbon Monomers: subunits of larger molecules
Simple sugars, fatty acids, amino acids, and nucleotides
Polymers: consist of multiple, repeating monomers, also called macromolecules
Cells build polymers from monomers, and break down polymers to release monomers

6. Carbohydrates
Carbohydrate: organic compound that consists of carbon, hydrogen, and oxygen in a 1:2:1 ratio – ALWAYS
Main function is source of energy, some are a source of structure
Three main types -
Monosaccharides: (one sugar) simplest type of carbohydrates

7. Carbohydrates Disaccharides: consist of two monosaccharide monomers
Lactose: glucose + galactose
Sucrose: glucose + fructose
Polysaccharides: chains of hundreds or thousands of monosaccharide monomers, complex carbohydrates
The most common polysaccharides are…

8. Carbohydrates
Cellulose: Main structural component of plants, Tough and insoluble, composed of chains of glucose monomers stretched side by side and hydrogen-bonded at many –OH groups
Chitin: a type of cellulose, durable, translucent, and flexible, reinforces the cell wall and strengthens the outer body covering of animals such as insects, spiders, and lobsters.

9. Carbohydrates
Starch: Main energy reserve in plants, Stored roots, stems, leaves, seeds, and fruits, Composed of a series of glucose monomers that form a chain that coils up
Glycogen: Main energy reserve in animals, Very abundant in muscle and liver cells, Highly branched chains of glucose monomers

10. Lipids Lipids: fatty, oily, or waxy organic compounds
Many incorporate fatty acids – organic molecules with a long hydrocarbon [hydrophobic/fatty] “tail” with a carboxyl group [hydrophilic/acidic] “head”
Main function is to store energy, some are used as insulation

11. Lipids
Fats: lipid that consists of a glycerol molecule with one, two, or three fatty acid tails
Triglyceride: a fat with three fatty acid tails
Saturated Fats: triglycerides with saturated fatty acid tails; only single bonds link the carbons in the tails so they’re flexible and wiggle, solid at room temperature

12. Lipids
Unsaturated Fats: triglycerides with unsaturated fatty acid tails; liquid at room temperature
Olestra is a is a synthetic fat with 8 fatty acid tails - it is very big and bulky. Because it is a fat, foods fry in it, but because of its size, fat-digesting enzymes (lipases) in our intestines cannot break it down...it passes right through our bodies unchanged...sometimes with interesting effects! This makes the food essentially fat-free (but not calorie-free!!)

13. Lipids
Trans fats have unsaturated fatty acid tails with hydrogen atoms around the double bonds
Small amounts of trans fats occur naturally but the main source is an artificial food product called partially hydrogenated vegetable oil
Hydrogenation: adds hydrogen atoms to oils in order to change them into solid fats
Trans fats raise the level of cholesterol in our blood more than any other fat and directly alters the function of arteries and veins
Eating as little as 2 grams a day increases the risk of atherosclerosis, heart attack, and diabetes

14. Lipids Phospholipid: main component of cell membranes
Phospholipids are arranged in two layers called a lipid bilayer
Steroids: lipids with no tails
Examples: estrogen and testosterone
Dictates many sex characteristics

15. Lipids
Wax: complex, varying mixture of lipids with long fatty acid tails bonded to alcohols or carbon rings
Molecules pack tightly, so waxes are firm and water repellent
Plants secrete waxes to restrict water loss and keep out parasites and other pests, other types of waxes protect, lubricate, and soften skin and hair

16. Proteins
Cells can make thousands of different proteins from only 20 kinds of amino acids (monomer)
Amino acids: small compounds made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfur.
Proteins function in movement, defense, and cell communication
Example: enzymes
A protein’s biological activity arises from and depends on its structure

17. Proteins
Heat, some salts, shifts in pH, or detergents can denature (unravel) a protein by breaking hydrogen bonds
Denaturation causes a protein to lose its function

18. Nucleic Acids Nucleic acids: Store and transmit genetic information
RNA (ribonucleic acid) and DNA (deoxyribonucleic acid)
Nucleotide: consists of a sugar with a five-carbon ring bonded to a nitrogen-containing base and one, two, or three phosphate groups
ATP (adenosine triphosphate) is a nucleotide that serves an important role as an energy carrier in cells

19. Nucleic Acids