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Lecture

BIOL 2020 Lecture Notes - Lipid Bilayer, Glycerol, Amphiphile

5 pages79 viewsFall 2011

Department
Biology
Course Code
BIOL 2020
Professor
Patrice Cote

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Section 1
December-08-11
10:46 AM
Four types of biological molecules
Carbohydrates (sugars)
o Monosaccharides
(CH2O)n
A single monomer
o Disaccharides
Ex. Sucrose
Two monomers
o Oligosaccharides
A small chain of 3-10 monomers covalently attached to lipids and proteins
Can attach to lipids, and proteins
Are found near the surface of the cell
They're like a cell's ID tag
o Polysaccharides
Composed of many monomers
Many different polysaccharides can be formed with the same sugars, but using
different bonds
Proteins
Nucleic acids
Carbs, proteins and nucleic acids start as monomers and combine into polymers
Lipids
o Soluble in certain organic solvents
o Not soluble in water
o Fats
Composed of three fatty acid tails bound to a glycerol moiety via ester bonds
Used mainly as energy stores
Stores in cells called adipocytes
Fatty Acids
Are amphipathic
Hydrocarbon chain
Hydrophobic
Carboxyl group (-COOH)
Hydrophilic
Kinks in fatty acid tails are C=O
Cis-fatty acid
Kinked unsaturated fatty acid
Liquid at room temperatire
Trans-fatty acid
Unsaturated, but not kinked
C=C bond
o Steroids
Cholesterol is the best known steroid
Found in membranes
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Sits between fatty acid tails
Makes the membrane more rigid
Is amphipathic because of its OH group
The rest of the cholesterol is hydrophobic
This causes molecules of cholesterol to clump together
o Phospholipids
Composed of glycerol moiety with two fatty acid tails, a phosphate group, bound to a
polar head group
Fatty acid tails hydrophobic, the rest is hydrophilic
Are the basic building blocks of cells
Building blocks of macromolecules
Monosaccharides --> Polysaccharides
Fatty acids --> Lipids
Amino acids --> Proteins
Nucleotides --> Nucleic Acids
Amino acids
Alpha carbon bound to:
o Carboxyl group
o Amino group
o R group (side chain)
o Hydrogen
Types of R groups
o Polar charged
Hydrophilic, acts as acid or base, full charge (+ or -), form ionic bonds and tend to be
involved in chemical reactions
o Polar uncharged
Hydrophilic, partial charge (+ or -), can participate in chemical reactions, form H bonds
and associate with water
Usually faces outside of protein
o Nonpolar
Hydrophobic, forms the inner core of soluble proteins. Associates with lipid bilayer in
membranes
Points towards lipids, or inner core of protein
o Unique properties
Glycine
Single H, fits in hydrophilic or hydrophobic environment, at sites of close contact
between two polypeptides
Makes polypeptide chain flexible
Cysteine
Can form a covalent link with another cysteine to form a disulfide link
Proline
Has a cyclic structure; bonds from alpha carbon to the N group on an amino acid
Produces a kink in the chain
Will eventually disrupt the secondary structure of a protein
Join via peptide bonds
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