CHAPTER 2: CHEMICAL BASIS OF LIFE

2.2 STRUCTURE OF MATTER All matter is made up of atoms – the smallest building blocks of matter Atoms make up elements – pure chemical substance w/ only 1 type of atom There are 118 elements on the current periodic table 92 of these are naturally occurring Living organisms require about 20 elements Oxygen, Carbon, Hydrogen, & Nitrogen make up more than 95% of the human body (table 2.1)

ATOMIC STRUCTURE

2.3: CHEMICAL CONSTITUENTS OF CELLS Organic – can dissolve in water but more likely to dissolve in organic liquids (Ether or alcohol) ones that do dissolve in H 2 O do not release ions  nonelectrolytes contain both carbon and hydrogen Inorganic – generally dissolve in water or react with water to release ions  electrolytes

INORGANIC SUBSTANCES Water - Most abundant compound in living material - Accounts for 2/3 of the weight of an adult human - Major component of blood and other body fluids, including those within cells Oxygen - Enters the body through the respiratory organs - Transported throughout the body by blood and red blood cells

INORGANIC SUBSTANCES Carbon Dioxide - Simple carbon-containing compound, waste product when certain metabolic processes release energy - Exhaled from the lungs Salts - Abundant in tissues and fluids - Provide many necessary ions needed for metabolic processes like transport substances into and out of cells, muscle contraction, & nerve impulse conduction

ORGANIC SUBSTANCES Carbohydrates - Provide much of the energy that cells require - Supply materials to build certain cell structures - Often stored as reserve energy supplies - Molecules contain atoms of carbon, hydrogen, & oxygen - Usually have twice as many hydrogen atoms as oxygen atoms - Carbon atoms of carbohydrate molecules join in chains whose lengths vary with the type of carbohydrate

CARBOHYDRATES Monosaccharides (simple sugars) - Have six carbon atoms (hexoses) - Building blocks of more complex carbohydrate molecules - Ex. Glucose, fructose, galactose

CARBOHYDRATES Disaccharides (double sugars) - Molecules each contain two simple-sugar building blocks - Ex. Sucrose (table sugar) & lactose (milk sugar) Polysaccharides - Made up of many simple-sugar units joined together - Ex. Plant starch & glycogen  humans synthesize this polysaccharide (similar to starch)

LIPIDS Insoluble in water but soluble in certain organic solvents (ether & chloroform) Include fats, phospholipids & steroids Fats – used to store energy for cellular activities; can store more than carbohydrates - Fatty acids and glycerol are the building blocks of fats - Each one contains carbon, hydrogen & oxygen atoms - Each fat contains a glycerol molecule and three fatty acid molecules - The glycerol portion of every fat is the same, but many different combination of fatty acids - Fatty acids with with single carbon-carbon bonds are called saturated fats - Ones with double bonds between carbon atoms are unsaturated fats

LIPIDS Phospholipid - Similar to a fat molecule in that it has a glycerol molecule and fatty acid chains - Only has 2 fatty acid chains instead of 3 - Third portion is a phosphate group that is soluble in water Steroid - Include four connected rings of carbon atoms - Ex. Cholesterol, estrogen, progesterone, testosterone, & several hormones from the adrenal glands

PROTEINS -Serve as structural materials, energy sources, and hormones -Combine with carbohydrates to function on cell surfaces as receptors -Specialized to bond to particular kinds of molecules -Antibodies act against foreign substances that enter the body -Enzymes – catalyze vital metabolic processes -Speed specific chemical reactions without being consumed by the reactions

NUCLEIC ACIDS Form genes Take part in protein synthesis Generally very large & complex molecules Contain atoms of carbon, hydrogen, oxygen, nitrogen, & phosphorus These are bound into building blocks called nucleotides

NUCLEIC ACIDS 2 major types: RNA (ribonucleic acid) – composed of molecules containing ribose DNA (deoxyribonucleic acid) – contains deoxyribose DNA stores information in the form of a genetic code cells use this info to make protein molecules RNA molecules aid in protein synthesis