Molecules of Life Chapter 3

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

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

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

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

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…

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.

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

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

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

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!!)

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

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

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

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

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

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

Nucleic Acids