30 August 2010
(P. J. Hollenbeck)
STRUCTURES OF BIOLOGICAL
Read: Chap 2: pp. 50-59; Panels 2-3 thru 2-6;
DVD 2.1-2.3; Problems 11-13; Q2-19
Download from the web syllabus the set of extra figures
that accompany this lecture>
Questions and classes
(A) What we want to know about the macromolecules that make up the cell
(1) There are 4 major classes of macromolecules in the cell that we will consider
repeatedly through out this course.
They have the common chemical composition of :
C, H, O, N, P, S.
They are synthesized from smaller, “building block” molecules
which allows efficient recycling and turnover of the macromolecules in the cell.
they are otherwise very different.
(2) Take the opportunity now to re-familiarize yourself with each of these 4 groups of
As you study them, ask yourself: What are the properties of each?
Which of the seven functional groups do they contain? What building blocks comprise
them, and how are they constructed?
Do they form larger polymers or other
associations? Where are they found in the cell, and what are their functions?
4 classes of macromolecules
(1) Lipids – we will consider steroids and phospholipids, which between them
constitute the bulk of the plasma and organelle membranes.
(2) Carbohydrates – monosaccharides (e.g., glucose, ribose, etc) are the building
blocks for oligosaccharides (e.g., the carbohydrate chains attached to membrane
proteins), and polysaccharides (e.g., cellulose, glycogen, starch)
(3) Nucleic acids – nucleotides are the building blocks for DNA and RNA, as well as
energy substrates and phosphate sources for a multitude of cellular reactions.
(4) Proteins – amino acids are the building blocks of polypeptides (protein molecules)
Structure and function
(1) Lipids in the cell come in 2 general flavors – those with acyl chains
and those with carbon ring backbones.
(2) Those with ring backbones are steroids such as cholesterol (see
shares a 4-ring structure with other steroids but has substituent groups that are unique.
The ring structure is rigid and planar.
The –OH group confers some polar character.
(3) Lipids with acyl chains include triglycerides and phospholipids (see
These have a glycerol backbone, connected by ester linkages to fatty acid chains (2
each for phospolipids, 3 for triacyglycerols).
The long acyl chains can have entirely
single (saturated) C-C bonds, or a mixture of single and double (unsaturated) C-C