• The convenience is that one mole of hydrogen atoms weighs 1.01 grams, the same in grams as the atomic mass of hydrogen in Daltons.– 1 mole of oxygen atoms = 15.999 grams– 1 mole of sodium atoms = 22.989 grams– 1 mole of any atom or molecule is found in the

atomic mass of that element, or the molecularmass of that compound.

Methods of Measurement

• pH = –log[H+] (concentration of H+ in moles/l)

• It is a scale that runs from 0 to 14

Acids, Bases and Buffers

• The pH scale is a logarithmic scale, not a linear scale. Because of the “negative” in the formula, the lower the number, the higher the H+ concentration ([H+]).

• Because it is logarithmic, a change of two or three pH units represents a change in the [H+] of 100 or 1000.– A solution with pH=1 is 100 times more

concentrated in H+ ions than a solution with a pH=3.– A solution with pH=11 contains 1000 times less H+

ions than a solution with a pH=8.

Acids, Bases and Buffers

Acids, Bases and BufferspH < 7 is acidic ([H+] > [OH-]); pH > 7 is alkaline ([H+] < [OH-])A salt (like KCl) is neutral

• The pH values of different parts of the body are maintained fairly constant by buffer systems, which usually consist of a weak acid and a weak base.– Buffers convert strong acids and strong bases into

weak acids and weak bases. They do this by “hiding” excess H+ ions or excess OH– ions as other molecules (like HCO3

– ) .– The major buffer system in the body is carbonic acid-

bicarbonate buffer system.

Acids, Bases and Buffers

Acids, Bases and BuffersInteractions Animation

• Acids and Bases

You must be connected to the internet to run this animation.

Functional groups are certain molecular configurations

which are easy to recognize.

They are found attached to the carbon skeleton and

impart certain properties to the organic molecule.

• Some of the more common functional groups are:

– Esters, amino, carboxyl, phosphate groups

– Others are found on the following chart (next slide)

Organic Compounds

Organic Compounds

Organic Compounds

Organic Compounds

• Very large molecules are called macromolecules (or

“polymers” if all the monomer subunits are similar).

• Isomers have the same

molecular formulas but different

structures (glucose & galactose

are both C6H12O6).

Organic Compounds

• Carbohydrates provide most of the energy needed for life and include sugars, starches, glycogen, and cellulose.

• Some carbohydrates are converted to other substances which are used to build structures and to generate ATP.

• Other carbohydrates function as food reserves.• Carbohydrates are divided into three major

groups based on their size: monosaccharides, disaccharides, and polysaccharides .

Organic Compounds

• Monosaccharides (Carbohydrates) are the simplest sugars:– 5 carbon sugars are used in

nucleic acids.

– 6 carbon sugars are the most

easily recognizable in our diet.

Organic Compounds

Disaccharides are made by combining 2 monosaccharides by removing a water molecule (dehydration synthesis): sucrose = glucose + fructose lactose = glucose + galactose

Organic Compounds

• Polysaccharides are the largest carbohydrates and may contain hundreds of monosaccharides.

• The principal polysaccharide in the human body is glycogen, which is stored in the liver or skeletal muscles.

• When blood sugar level drops, the liver hydrolyzes glycogen to yield glucose which is released from the liver into the blood.

Organic Compounds

• Lipids are another major group of organic molecules.

– Like carbohydrates, they contain carbon, hydrogen, and oxygen;

unlike carbohydrates, they do not have a 2:1 ratio of hydrogen to

oxygen.

• They have few polar covalent bonds, which makes them

hydrophobic and mostly insoluble in water.

• They combine with

proteins (lipoproteins)

for transport in blood.

Organic Compounds

• Triglycerides are the most plentiful lipids in the body and provide protection, insulation, and energy (both immediate and stored).– At room temperature, triglycerides may be either

solid (fats) or liquid (oils).– Triglyceride storage is virtually unlimited.– Excess dietary carbohydrates, proteins, fats, and oils

are deposited in adipose tissue as triglycerides.

Organic Compounds

Triglycerides provide more than twice as much energy per gram as either carbohydrates or proteins.

Organic Compounds

• Phospholipids are important membrane components.

• Both polar and nonpolar regions make them soluble in both water and fats (this is called amphipathic—they are both hydrophilic and lipophilic.)– They have a polar head formed from a phosphate

group (PO4-3) & a glycerol molecule (forms H-bonds

with water), and 2 nonpolar fatty acid tails that interact only with lipids.

Organic Compounds

Phospholipids have a polar head and 2 non-polar tails:

Organic Compounds

• Steroids are lipids molecules that have four rings of carbon atoms. They include: – Sex hormones– Bile salts– Some vitamins– Cholesterol, which serves as an important

component of cell membranes and as starting material for synthesizing other steroids

Organic Compounds

• Steroids are based on the lipid cholesterol molecule.– They include the molecules

used as sex hormones, as well as other hormones used in coping with stress (cortisol).

Organic Compounds

• Nucleic acids are huge organic molecules composed of monomeric nucleotides (like the one shown below):– They contain carbon, hydrogen, oxygen, nitrogen, and

phosphorus, and form the principle molecules that contain our genetic code – DNA and RNA.

– We will return to discuss nucleic acids in more detail later in this chapter.

Organic Compounds