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Chemical Compounds for Life

• All living things are mostly composed of 4 elements: H, O, N, C "honk"
• Compounds are broken down into 2 general categories:
• Inorganic Compounds:
• Do not contain carbon
• Organic compounds
• Contain significant amounts of carbon.
• Often found with common "functional groups"

Carbon: The "swiss army knife" of chemistry.

• Carbon is essential to life for several reasons:

1. It can form strong stable (usually nonpolar) covalent bonds
2. It can form up to 4 chemical bonds
3. It can form multiple bonds

• Organic Compounds often form Polymers
• Long chains of smaller molecules (not atoms) called monomers, bind to form huge Macromolecules.

Organic Compounds of life:

• 4 Types: Carbohydrates, Lipids, Proteins & Nucleic acids

CARBOHYDRATES:

• Includes: Sugars, starches, cellulose & glycogen
• Made of Carbon ( C ), Hydrogen ( H ), and Oxygen (O )
• Following ratio of elements C_nH_2nO_n
• Sugars: Provide & store energy for cells
• Simple sugars include Glucose & Fructose since these are made of only 1 Carbohydrate molecule they are known as Monosaccharides.

• Monosaccharides can be linked together through the process of Dehydration Synthesis
• Water is removed from 2 monocaccharides - resulting in a covalent bond between the 2 molecules
• Sucrose (table sugar) is made of 2 sugars linked together and these are called Disaccharides
• Often referred to as transport saccharides
• Require some digestion to be used by cells

Dehydration Synthesis

• Starches are many monosaccharides linked together in a single chain. These are called Polysaccharides.
• Plants use this for energy storage e.g. Potatoes
• Two types
  • Amylose - Long strait unbranched chains
  • Pectins - many linked short Amylose chains

Starch

• Cellulose is made of long polysaccharide chains
• Plants use this for structure (e.g. Wood) - not very digestible
• Due to the reverse orientation of the monosaccharide sububnits, digestive enzymes cannot hydrolize the bonds between them

Cellulose

• Glycogen is a moderately branched polysaccharide
• Animals use this for energy storage.

Glycogen

Lipids:

• Lipids are macromolecules including fats, waxes & oils
• Primary function is energy storage.
• Energy is stored in C-H bonds.
• More efficient in storing energy
• Lipids are made of 2 parts
• Glycerol - an alcohol - Serves as backbone of the molecule
• 3 Fatty acids - Long hydrocarbon chains

Saturated fats have long chains with no double-bonds

Unsaturated fats have double bonds

Polyunsaturated fats have many double bonds

Each time a double bond is encountered, the molecule "Bends" slightly, resulting in a lower density of the lipid. This makes the molecule more likely to remain liquid at room or body temperatures.

4 Major types of biologically important Lipids

Phospholipids - Important for membrane structure

Steroids - eg. Cholesterol & testosterone. Provide membrane support / serve as hormones

Terpenes - serve as important components of pigments

Prostaglandins - appear to act like localized hormones to induce cellular/tissue responses.

• Proteins are made of Amino Acids
• There are 20 different amino acids. Each having a similar general structure - Differ only in their "R" groups

example amino acids

• Amino acids form proteins via deyhdration sythesis forming peptide bonds

• Two amino acids linked together are called dipeptides
• More than 2 linked together are called polypeptides - polypeptides can be thousands of amino acids long

• Protein types include globular proteins which are usually enzymes and Fiberous proteins which usually serve for structure (eg. Hair)
• Proteins Exhibit 4 "levels of structure.

• Primary Structure of a protein is it’s sequence of amino acids.

• The Sequence (primary structure) causes parts of a protein molecule to fold into sheets or bend into helix shapes - this is a protein’s Secondary Structure.

• The protein then can compact and twist on itself to form a mass called it’s Tertiary Structure

• Several Proteins then can combine and form a protein’s Quaternary Structure.

• Various conformations are usually caused by the formation of hydrogen or disulfide bonds
• PH, changes or heat can disrupt these bonds, permanently denaturing the protein.

Nucleic Acids

• Two types of Nucleic acids
• DNA (Deoxyribonucleic Acid)
• RNA (Ribonucleic acid)
• DNA is Formed of in a "Double Helix" - like a spiral staircase.

• DNA is formed by Nucleotides
• These are made from 3 components
• A 5-Carbon Sugar
• A Nitrogenous base
• A Phosphate group

• Nucleotides form a backbone through linkages from the OH group of the 3^rd carbon to a phosphate group of the adjoining nucleotide. These are called Phosphodiester bonds

• For DNA There are 4 different Nucleotides categorized as either Purines (double ring) or Pyramidines (single ringed). These are usually represented by a letter. These Are:
• Adenine (A)
• Cytosine (C)
• Guanine (G)
• Thymine (T)

• Each "Rung" of the DNA "staircase" is formed by the linking of 2 Nucleotides through Hydrogen Bonds.
• These Hydrogen bonds form only between specific Nucleotides. This is known as Base Pairing. The rules are as follows:
• Adenine (A) will ONLY bond to Thymine (T)
• Cytosine (C) will ONLY bond to Guanine (G)

• RNA differs from DNA in several important ways.

1. It is much smaller
2. It is single-stranded
3. It does NOT contain Thymine, but rather a new nucleotide called Uracil which will bind to Adenine.

Comparison of DNA & RNA

• ATP is closely related to nucleic acids.
• Composed of Ribose, Adenine & a phosphate group
• Phosphate group has ability to bind/release additional phosphate group allowing it to store or release energy.

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Mr. Stanley

Last Updated: March 11, 2004