Biology 107
Macromolecules I
September 2,
2005
Macromolecules I
Student Objectives: As a result of this lecture and the assigned
reading, you should understand the following:
1.
The four major types of organic macromolecules are:
carbohydrates, lipids, proteins, and nucleic acids.
2.
Carbohydrates generally have molecular formulas that are some
multiple of CH2O, and carbohydrates range from single small
sugar molecules (monosaccharides) to long polymers of sugar
monomers (polysaccharides).
a. Structure - Monosaccharides have two or more -OH groups
and either an aldehyde or a ketone group. Polysaccharides
may be straight or branched molecules of hundreds or
thousands of sugar monomers. Some sugars are highly
negatively charged because they are commonly sulfated
(SO3-) or because they contain a carboxyl group (COO-).
Macromolecules I
b. Functions - energy source, recognition or signaling, and/or
structural.
3.
Lipids consist mainly of C and H atoms linked by nonpolar
covalent bonds; consequently, lipids are not attracted to polar
water molecules, and lipids are hydrophobic.
a. Structure –
Fats and oils are large lipids made from glycerol and fatty acids.
Triglyceride fats consist of three (3) fatty acid chains hooked to a
glycerol molecule. For saturated fats, every C atom of the carbon
skeleton (except the carboxyl carbon) carries 2 H atoms (the
maximum number of hydrogens). In contrast, unsaturated fats
contain double bonds and less than the maximum number of
hydrogens possible.
Macromolecules I
Phospholipids, the major components of cellular membranes,
are structurally similar to fats except they contain a phosphate
group and only 2 fatty acid chains attached to the glycerol.
Steroids are lipids with the carbon chain bent to form fused
rings. Cholesterol is a common substance in animal cell
membranes. Animal cells also use cholesterol as a
precursor for making other steroids, including male and female
sex hormones.
b. Functions - energy storage, membrane structure, hormone
signaling, and/or insulation.
Four Main Types of Macromolecules
Common Carbohydrates Classified by Number of
Carbons
Examples of Hexose Isomers
Examples of Linear Compared to Ring Forms of
Carbohydrate
Disaccharides
Polysaccharides
Examples:
Starch – Fxn as
storage form of
energy
Cellulose – Fxn
as structural
material
Storage Polysaccharides
• Starch and glycogen are storage polysaccarides in animals and
plants. Polymers of glucose. Reserve fuel.
• Starch (plant cells) is an isomer of cellulose with a-glycosidic
bonds. Unbranched (amylose) and branched (amylopectin).
• Glycogen (animal cells) is similar structure to starch but with ßglycosidic bonds and highly branched. Degraded from end, so
branches allow rapid degradation.
Starch
Glycogen
• Large branched polymer
• Most glucose units linked by a-1,4 glycosidic bonds
• Branches formed by a-1,6 glycosidic bonds every
~10 glucose units
Structural Oligosaccharides
Cellulose - plant cell walls, load bearing. Fifty percent of
carbon in biosphere. May have up to 15,000 glucose
residues
Chitin - exoskeletons (crustaceans, insects), cell walls
of fungi and algae.
Lipids - Fats
Triglyceride Fats
Saturated Fatty Acid Chains
Unsaturated Fatty Acid Chains
Comparison of Saturated and Unsaturated Fatty
Acid Chains
Sources of Saturated and
Unsaturated Fatty Acids
Phospholipids
Phospholipids in Water
Structure of Phospholipids and Steroids
Examples of Lipids Other Than
Phospholipids or Steroids
Different Types of Macromolecules May
be Covalently Linked (e.g., Glycolipids)