Biology

The Molecules of Cells

Carbon and Functional Groups

I. Why is Carbon Important?

A. What is Organic Chemistry?

• The study of carbon compounds is know as Organic Chemistry

• Organic molecules are molecules that contain carbon

A Look at History

• Vitalism (Early 19th Century) Belief in a life force outside the jurisdiction of chemical/physical laws.

• It was believed that only living organisms could produce organic compounds.

• Mechanism – Belief that all natural phenomena are governed by physical and chemical laws.

• Began to synthesize organic compounds from inorganic molecules.

B. Carbon – A Close Look

• Has an atomic number of 6, leaving 4 valence electrons.

• Forms four covalent bonds.

C. Carbon Variations

• Length (Ethylene to Fatty Acids)

• Shape (Straight Chain, branched, rings)

D. Hydrocarbons

• Molecules containing only Carbon and Hydrogen

• Major components of fossil fuels.

E. Isomers

• Compounds with the same molecular formula but with different structures and hence different properties.

II. Functional Groups

• Contribute to the molecular diversity of life.

• Frequently bonded to the carbon skeleton of organic molecules.

• Often determine the unique chemical properties of organic molecules.

• Are the regions of organic molecules which are commonly chemically reactive.

III. Macromolecules

• A. Polymer Principal

– Most Macromolecules are polymers.

– Polymer – large molecule consisting of many identical or similar subunits connected together.

– Monomer – Subunit or building block molecule of a polymer.

– Macromolecule – large organic polymer

B. Four classes of macromolecules

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic Acids

C. Polymers are synthesized by a process know as dehydration synthesis.

D. Polymers are broke apart by a process known as hydrolysis.

IV. Carbohydrates

• Fuel and building material.

• Organic molecules made of sugars and their polymers.

• Monomers are called monosaccharides.

• Classified by the number of simple sugars.

A. Monosaccharides

• Simple sugar in which C, H, & O occur in a ratio of (CH2O)

• Major nutrients for cells (glucose)

• Store energy in their chemical bonds.

B. Disaccharides

• A double sugar consisting of two monosaccharides joined by glycosidic linkage

C. Polysaccharides

• Macromolecules that are polymers of a few hundred or thousand monosaccharides.

• Formed by dehydration synthesis.

• Have two functions: energy storage and structural support.

V. Lipids

• Insoluble in water

• Groups include; fats, phospholipids, and steroids

A. Fats

• Store large amounts of energy (One gram of fat stores twice as much energy as a gram of polysaccharide)

• Cushions vital organs in mammals.

• Insulates against heat loss.

• Two classes of fats; saturated fat and unsaturated fat.

1. Saturated fat

• No double bonds between carbons in fatty acid tail

• Most animal fats (Ex: bacon grease, butter)

2. Unsaturated fat

• There are double bonds between carbons in fatty acid tail.

• Most plant fats (Ex: peanut and olive oil)

B. Phospholipids

• Major constituents of cell membranes

C. Steroids

• Lipids which have four fused carbon rings with various functional groups attached.

VI. Proteins

• A macromolecule that consists of one or more polypeptide chains folded and coiled into specific conformations.

• Polypeptide chain – polymers of amino acids that are arranged in a specific linear sequence and are linked by peptide bonds.

• Are abundant – making up 50% or more of cellular dry weight.

• Have many functions

– Structural support

– Catalysis of biochemical reactions (enzymes)

– Transport (hemoglobin)

– Signaling (chemical messengers)

– Movement (contractile proteins)

– Defense against antigens (antibodies)

A. Amino Acids

• Only 20 amino acids make millions of different proteins

• Building block molecules of a protein

• Consists of;

B. Peptide Bond – a covalent bond formed by a dehydration synthesis reaction.

C. Function is dependent upon structure.

• Protein conformation – 3D shape of a protein.

• Denaturation – A process that alters a proteins conformation and biological activity.

– Transfer to an organic solvent.

– Breaking hydrogen bonds, ionic bonds, and disulfide bridges

– Excessive heat

1. Four levels of protein structure.

a. Primary structure – unique sequence of amino acids in a protein.

b. Secondary structure – regular, repeated coiling and folding of a protein’s polypeptide backbone.

i. Two types: Alpha helix and Beta pleated sheets

c. Tertiary structure – the three-dimensional shape of a protein.

d. Quaternary structure – interactions between several polypeptide chains.

VII. Nucleic Acids

• Stores and transmits hereditary information.

• Two types – DNA & RNA

A. DNA (Deoxyribonucleic acid)

• Contains coded information that programs all cell activity

• Contains directions for its own replication

- DNA continued

• Is copied and passed from one generation of cells to another.

• In eukaryotic cells, found primarily in the nucleus

• Makes up your genes

B. RNA (Ribonucleic Acid)

• Functions in the actual synthesis of proteins coded for by DNA

C. Parts of Nucleic Acid

• Nucleic acid – Polymer of nucleotides linked together

• Nucleotide – Building block molecule, made up of;

D. Nitrogenous bases

• Two families of bases

1. Pyrimidine – Six membered ring

- Includes: Cytosine (C), Thymine (T), & Uracil (U)

2. Purine – Five membered ring fused to a six-membered ring

- Includes: Adenine (A) and Guanine (G)

E. Functions of Nucleotides

• Monomers for nucleic acids

• Transfer chemical energy from one molecule to another (ATP)

• Are electron acceptors in enzyme – controlled redox reactions (NAD)

• Each gene contains a unique linear sequence of nitrogenous bases; which in turn code for a unique linear sequence of amino acids in a protein.

F. DNA and Proteins

• Can be used as a tape measure of evolution.

• More closely related species have more similar sequences of DNA and amino acids.