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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.