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.
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