Chapter 2: Chemical Basis of Life

Elements In the Human Body

Major Elements Symbol Percentage in bodyOxygen O 65%Carbon C 18.5% Hydrogen H 9.5%Nitrogen N 3.2Calcium Ca 1.5Phosphorus P 1.0Potassium K 0.4Sulfur S 0.3Chlorine Cl 0.2Sodium Na 0.2 Magnesium Mg 0.1

2.3 Chemical Constituents of Cell

Organic – contain carbon and hydrogen atoms.Inorganic – molecules that does not contain

carbon and hydrogen.Inorganic substances dissolve in water or react

with water to release ions --- called electrolytes.

Inorganic Substances

Water, oxygen, carbon dioxide, and salts.Water:-major component of blood.-important solvent-aqueous portion of blood carries vital

substances such as oxygen, sugars, salts, and vitamins, from the organs of digestion and respiration to the body cells.

Oxygen

Transported throughout the body by the blood.RBC bind and carry oxygen.Cells use oxygen to release energy from teh

sugar glucose and other nutrients.Energy drives the cell’s metabolic activities.

Carbon Dioxide

CO2

Produced as a waste product when certain metabolic processes release energy, and it is exhaled from the lungs.

Salts

Compound composed of oppositely-charged ions.Na+ and Cl- ------ NaCl saltSalts provide necessary ions: Na+, Cl-, K+, Ca+2…

Ions are important in metabolic processes.Transport of substances into and out of cells,

muscle contraction, and nerve impulse conduction.

Review questions

1. How do inorganic and organic molecules differ?Organic contains hydrogen and carbon.Inorganic doesn’t contain both hydrogen and

carbon.2. How do electrolytes and nonelectrolytes differ?Inorganic substances that dissolve in water and

release ions are called electrolytes ---organic substances that dissolve in water do not release ions and are called nonelectrolytes.

Organic Substances

CarbohydratesLipidsProteinsNucleic Acids

Carbohydrates

Provide much of the energy that cells require.Used to build cell structures.Stored energy.

Molecules:Carbon, hydrogen, and oxygen(twice as many hydrogen than oxygen atoms)

C6H12O6 glucose

Sugars

• Carbohydrates with shorter chains.– monosaccharides

Complex Carbohydrates

Disaccharides – double sugars.- sucrose, lactose.

Polysaccharides – many simple sugars joined.- plant starch- glycogen

Lipids

• Organic substances that are insoluble in water.• Soluble in certain organic solvents.Ex. Fats, phospholipids, steroids

Fats

• Store energy for cellular activities.• Can supply more energy per gram than

carbohydrate molecules.

Molecules:Carbon, hydrogen and oxygen-have a much smaller proportion of oxygen

atoms than do carbs.

Fatty acids and glycerol

• Building blocks of fat molecules.• Each glycerol molecule bonds with three fatty

acid molecules to produce a single fat. (triglyceride)

• Glycerol portions of all fat molecules are the same but the fats are diverse because there are many kinds of fatty acids.

Saturated vs. Unsaturated

Sing carbon-carbon bones –saturated fatty acid.Each carbon atom is bound to as many hydrogen

atoms as possible.

Other fatty acid chains do not have the max number of hydrogen atoms bound to it. Have one or more double bonds of carbon molecules. –unsaturated

Saturated and unsaturated fats.

PhospholipidPhospholipid – contains a glycerol portion and

two fatty acid chains and a phosphate group.Phosphate group is soluble in water. (hydrophilic)Fatty acid portion is insoluble in water. (hydrophobic)

Steroids • Complex structures with four connected rings

of carbon atoms.• Ex. Estrogen, progesterone, testosterone..

Proteins

• Energy source• Hormones• Structural materials• Glycoproteins – found on cell surfaces as

receptors that bond with certain molecules.• Antibodies – detect and destroy foreign

substances in the body.• Enzymes – catalyzes reactions.

Amino acids

• Building blocks of protein.• Contain: Nitrogen, sometimes sulfur

-NH2 (amino group)-COOH (carboxyl group)-R group (this distinguishes what type of amino

acid it is)

20 different amino acids

• Polypeptide chain

• Structure: primary, secondary, and tertiary levels.• Conformation: 3-d shape• Conformation determines its function.Types:Long and fibrous – keratin, forms hairGlobular – enzymes, ion channels, carrier proteins.

Denatured

When hydrogen bonds in a protein break because of excessive heat, radiation, electricity, pH changes, other chemicals.

Ex. Heat denatures the protein in egg white (albumin), changing it from a liquid to a solid.

Nucleic Acids

• Form genes and take part in protein synthesis.• Contain: Carbon, Hydrogen, Oxygen, Nitrogen,

and Phosphorus• Nucleotides: ribose or deoxyribose, phosphate

group, nitrogenous bases.

2 types

RNA (ribonucleic acid)DNA (deoxyribonucleic acid)

Adenosine triphosphate (ATP) – provide energy to certain chemical reactions.

Prions

• Type of protein that can cause disease.Ex. mad cow disease, Creutzfeldt-Jakob disease