Chemistry of Life

Atoms

Smallest particles that retain properties of an element.

Made up of subatomic particles.

Protons (+)

Electrons (-)

Neutrons (no charge)

Elements

Fundamental forms of matter

Can't be broken by normal means

92 occur naturally on Earth

The most common elements in living organisms are Oxygen, Carbon, Nitrgoen and Hydrogen.

Molecules

A molecule is a group of atoms held together by energy

The holding force is called a chemical bond.

There are 3 kinds of chemical bonds

1. Ionic bonds

2. Covalent bonds

3. Hydrogen bonds

Ionic Bonds

An ion is a charged atom or molecule.Ions of opposite charge may form an ionic bond.

Covalent Bonds

Molecules are groups of atoms linked by covalent bonds.

Hydrogen Bonds

Hydrogen bonding occurs between polar molecules.

Water makes up a large portion of living organisms. It has several unusual properties that make it essential for life. Hydrogen bonds lie behind these important properties.

Specific heat capacity – 1 calorie is required to elevate temperature of 1 gram of water 1°C. Moderates environmental changes.

High heat of vaporization – more than 500 calories are required to convert 1 g of liquid water to water vapor.

Cooling produced by evaporation of water is important for expelling excess heat.

Unique density behavior - while most liquids become denser with increasing temperature, water's maximum density is at 4 degrees C.

Water has high surface tension. Because of the hydrogen bonds between water molecules at the water-air interface, the water molecules cling together. Water has low viscosity.

Water acts as a solvent – salts dissolve more in water than in any other solvent.Result of the dipolar nature of water.

Acids and Bases

Acids increase the hydrogen ion concentration of a solution.

Bases decrease the hydrogen ion concentration of a solution.

pH scale measures the strength of acids and bases.

Neutral solution with a pH of 7: [H+] = [OH-]

Basic solution with a pH above 7: [H+] < [OH-]

Acidic solution with a pH below 7: [H+] > [OH-]

Buffer: Molecules that prevent dramatic changes in the pH of fluids. lRemove H+ and OH- in solution and transfers them to other molecules. Example: Bicarbonate Ion (HCO3-)

Recall the four major categories of biological macromolecules:

1. Carbohydrates
2. Lipids
3. Proteins

4. Nucleic Acids

Carbohydrates are compounds of carbon (C), hydrogen (H) and oxygen (O). Usually found 1C:2H:1O. Usually grouped as H-C-OH.

Function as structural elements and as a source of chemical energy (ex. glucose)

Plants use water (H2O) and carbon dioxide (CO2) along with solar energy to manufacture carbohydrates in the process of photosynthesis. 6CO2 +6H2O ----> light

---->C6H12O6 + 6O2

Life depends on this reaction – it is the starting point for the formation of food.

3 classes of carbohydrates

• Monosaccharide: Glucose, Fructose and ribose
• Disaccharide: Maltose (Glucose + Glucose) and Sucrose (Glucose + Fructose)
• Polysaccharide: Starch (made of glucose subunits) and
• Glycogen (made of glucose subunits, but linked differently from starch). (Plants use mostly starch, humans use mostly glycogen)
• Also note that most polysaccharides are insoluble.

State one function of a monosaccharide and one function of a polysaccharide.

Glucose, a monosaccharide has many important functions.

Glucose molecules are used in respiration.

Glucose is builidng blocs larger carbohydrates such as starch, glycogen, and cellulose.

Starch, a storage polysaccharide for plants.Cellulose and Chitin, are polysaccharides important for structure.

Advantages of Carbohydrates

1. More easily digested, so energy is releases more easily from them.

2. Carbohydrates are soluble in water, so easier to transport.

Lipids are fatty substances

Nonpolar - insoluble in water

Neutral fats

Phospholipids

Steroids

lNeutral fats are the major fuel of animals.

lTriglycerides – glycerol and 3 fatty acids

lSaturated fatty acids occur when every carbon holds two hydrogen atoms.

lUnsaturated fatty acids have two or more carbon atoms joined by double bonds.

Phospholipids are important components of cell membranes.

lThey resemble triglycerides, except one fatty acid is replaced by phosphoric acid and an organic base.

lThe phosphate group is charged (polar)..

lSteroids are complex alcohols with fatlike properties.lCholesterol

lVitamin D

lAdrenocortical hormones

lSex hormones

Proteins are large complex molecules composed of amino acids.

Amino acids linked by peptide bonds

Two amino acids joined – dipeptide

Many amino acids – polypeptide chain

lProteins are complex molecules organized on many levels.

lPrimary structure – sequence of amino acids.

lSecondary structure – helix or pleated sheet. Stabilized with H-bonds.

lTertiary structure – 3-dimensional structure of folded chains. Eg. Disulfide bond is a covalent bond between sulfur atoms in two cysteine amino acids that are near each other.

lQuaternary structure describes proteins with more than one polypeptide chain. Hemoglobin has four subunits.

Proteins serve many functions.

Structural framework.

Enzymes that serve as catalysts

Enzymes are protein catalysts that accelerate certain chemical reactions by providing alternative mechanism in which energy-of-activation bariers are lower than in the original reaction mechanim.

Nucleic acids are complex molecules with particular sequences of nitrogenous bases that encode genetic information.

lThe only molecules that can replicate themselves – with help from enzymes.

lDeoxyribonucleic acid (DNA)

lRibonucleic acid (RNA)

lThe repeated units, called nucleotides, each contain a sugar, a nitrogenous base, and a phosphate group.