Ch. 2 Some Basic Chemistry

Acid – substance that increases conc. of H+ in water solution

Base – substance that decreases conc. of H+

pH scale measures acidity or alkalinity (basicity) of solutions (Fig. 2-5)◦ 0 (most acidic) to 14 (most basic)◦ 7 = neutral ◦ < 7 = acidic◦ > 7 = basic (alkaline)

Acids, Bases, pH

Acidic – higher conc. of H+

Basic – higher conc. of OH-

Change of one pH unit is a 10-fold change in H+ concentration [H+]

Cells, internal fluids have a pH close to 7◦ Intracellular fluid = 6.8◦ Blood = 7.35 to 7.45 (critical range)

Acids, Bases, pH (cont.)

Chemical or pair of chemicals ◦ Minimize(s) pH change by reacting with strong

acids (SA) or strong bases (SB)

Buffer Systems

All contain covalently bonded C,H atoms 4 major groups

◦ Carbohydrates◦ Proteins◦ Lipids◦ Nucleic acids

Organic Compounds of Importance

Serve as sources of energy in cell respiration

Contain C, H, O Classified as:

◦ Monosaccharides◦ Disaccharides◦ Oligosaccharides◦ Polysaccharides

Carbohydrates

Simple sugars Glucose

◦ Hexose (6-C sugar)◦ Fructose, galactose have same formula, but

different atom arrangement Pentose (5-C sugar)

◦ Structural components of nucleic acids DNA (deoxyribose) RNA (ribose)

Monosaccharides

Double sugars◦ 2 monosaccharides linked by covalent bond◦ Sucrose = glucose + fructose◦ Lactose = glucose + galactose◦ Maltose = glucose + glucose◦ Broken down into monosaccharides & used for

energy production

Disaccharides

3 to 20 monosaccharides Found on outer surface of cell membranes Serve as antigens

◦ chemical markers that identify cells

Oligosaccharides

Thousands of glucose molecules Starches

◦ energy storage by plant cells Glycogen

◦ energy storage by animal cells

Polysaccharides

Nearly straight chain of glucose produced by plant cells as part of cell walls

We have no enzymes to digest cellulose◦ Serve as fiber to promote peristalsis (contraction)

of undigested food thru the colon

Cellulose

Contain C, H, O◦ Some contain P

3 types◦ True fats◦ Phospholipids◦ Steroids (Fig. 2-7)

Lipids

Made of 1 glycerol molecule and 1, 2, or 3 fatty acid (f.a.) molecules

Triglyceride◦ 3 f.a. bonded to a glycerol

Diglyceride◦ 2 f.a. bonded to a glycerol

Monoglyceride◦ 1 f.a. bonded to a glycerol

True fats (neutral fats)

Fatty acids may be saturated or unsaturated (Fig. 2-7)

Saturated◦ Only single bonds between its C atoms◦ Usually solid at room temp.◦ beef, pork, eggs, cheese

Unsaturated◦ At least 1 double bond between C atoms◦ Often liquid at room temp.◦ Corn/sunflower/safflower oil; some fish oils

True fats (cont.)

Trans fats◦ Unsaturated fats changed to saturated fats ◦ Hydrogen has been added◦ Gives a more pleasant texture or taste◦ Provides longer shelf life◦ Contribute to atherosclerosis

Abnormal cholesterol deposits clog arteries Triglycerides

◦ Storage form for excess food Potential energy

True fats (cont.)

Diglycerides with a phosphate (PO4) group in the third bonding site of glycerol

Structural components of cells Myelin

◦ Forms myelin sheath around nerve cells◦ Provides insulation for nerve impulse transmission

Phospholipids

Cholesterol◦ Made of 4 rings of C, H (Fig. 2-7)◦ Component of cell membranes◦ Precursor for making other steroids

estrogen or testosterone◦ Cholesterol in skin converts to vitamin D upon

sunlight exposure◦ Liver cells use cholesterol to synthesize bile salts◦ See Table 2-4

Steroids

Made of subunits called amino acids (AA)◦ Contain C, H, O, N◦ Some AA contain S for building disulfide bonds◦ 20 AA make up human proteins (Fig. 2-8)◦ Each AA has a central C bonded to a H atom, an

amino (NH2) group, and a carboxyl (COOH) group◦ A variable R group is found at the 4th bond of the

central carbon◦ Peptide bond – bond between 2 AA◦ Polypeptide – short chain of AA linked by a

peptide bond

Proteins

Consists of 50 to 1000s of AA Primary structure

◦ Sequence of AA is specific to each protein Secondary structure

◦ Protein is folded into a helix (coil) or pleated sheet Tertiary structure

◦ Protein folds into a globular structure (Fig. 2-8) Quaternary structure

◦ Some proteins consist of more than one AA chain Hemoglobin has 4 AA chains

Proteins

Some require trace elements (Fe, Zn) to complete their structure & function properly

Functions (Table 2-5) Excess AA will be converted to

carbohydrates or fat to be stored as potential energy

Proteins

Type of protein that catalyzes reactions◦ Catalyst – speed up chemical rxns

Most human enzymes function in normal range of body temp. (97 to 99°F)

At 106°F, enzymes can lose their shape (denature)◦ Unable to function as catalyst◦ May cause brain damage or death because

enzymes are permanently denatured

Enzymes

Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) Made of subunits called nucleotides

consisting of:◦ Pentose sugar◦ Phosphate group◦ Nitrogenous base

Nucleic Acids

Nucleotide◦ Pentose sugar – deoxyribose◦ Nitrogenous bases – adenine (A), guanine (G),

cytosine (C), and thymine (T) A:T; C:G

◦ Fig. 2-10 Looks like a ladder 2 strands of nucleotides called a double helix

◦ Alternating P and sugars form the uprights and pairs of N-bases form the rungs

DNA

Makes up the chromosomes of cells◦ The genetic code for hereditary characteristics

Gene ◦ Sequence of bases for one protein

DNA

Nucleotides◦ Pentose sugar – ribose◦ Nitrogenous bases – A, G, C, uracil (U)

A:U; C:G◦ Single strand of nucleotides (Fig. 2-10)◦ Synthesized from DNA in cell’s nucleus◦ Carries out function in the cytoplasm

Protein synthesis

RNA

Adenosine triphosphate◦ Specialized nucleotide consisting of A, ribose

sugar, 3 phosphate groups◦ Product of cell respiration◦ Energy transfer molecule

Transfers potential energy in food to cell processes◦ See Table 2-6

ATP