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LAMC Bio 3 Lecture Notes: Chapter 3 – The
Molecules of Cells
Reading Assignment: Chapter 3
Learning Outcomes:
By the end of today’s lecture, you should be able to:
- define organic compound, hydrocarbon, and isomer
- distinguish among the five functional groups
- explain the relationship between monomers and polymers
- compare the processes of dehydration synthesis and hydrolysis
- list the three classes of macromolecules,
- describe the distinguishing characteristics of carbohydrate, lipid and protein
molecules
I. Organic molecules:
Organic compound – a molecule that contains at least one
carbon atom.
Hydrocarbon – molecules that contain only carbon and hydrogen atoms (e.g. CH4).
All hydrocarbons are nonpolar because C-H bonds are nonpolar.
Carbon skeleton – the chain of carbon atoms in an organic molecule.
Isomer – compounds with the same formula, but different structures.
II. Functional groups:
Functional groups – refers to the groups of atoms that
usually participate in chemical reactions. All the functional groups we will
discuss are polar, so the molecules that they are attached to are also polar.
Hydrophilic molecules - molecules that are polar and “water loving”. They
dissolve easily in water.
Hydrophobic molecules – molecules that are nonpolar and “water hating”. They do
not dissolve in water.
Hydroxyl group: ─OH Carboxyl group: ─COOH
Phosphate group: ─OPO3
Carbonyl group: ─C=O Amino group: ─NH2
Monomers are small molecules that are the building blocks
of larger molecules (polymers).
Macromolecules – very large molecules (e.g. carbohydrates, lipids, and proteins)
Dehydration reaction – a reaction that removes a molecule of water and
consequently links monomers together into a polymer.
Hydrolysis reaction – a reaction that breaks the bonds between monomers by
adding a molecule of water.
III. Carbohydrates:
Monosaccharide – a carbohydrate monomer (e.g. glucose,
fructose, galactose)
Disaccharide – a carbohydrate molecule composed of two monosaccharides (e.g.
maltose, sucrose, lactose)
Polysaccharide - a carbohydrate molecule composed of many monosaccharides (e.g.
starch, glycogen, cellulose)
IV. Lipids:
Lipids – diverse compounds that consist mainly of carbon
and hydrogen atoms. They are mostly nonpolar molecules, so they are hydrophobic
(e.g. triglycerides, phospholipids, waxes, steroids)
Saturated fats – contain single bonds and forms a linear structure. These fats
are solid at room temperature.
Unsaturated fats – contain double bonds and forms kinks in the chain. These
fats are liquid at room temperature.
V. Proteins
Protein – a polymer constructed of amino acid monomers
(e.g. enzymes, hemoglobin, antibodies)
A protein’s shape depends on four levels of structure: primary, secondary,
tertiary, quaternary
VI. Nucleic Acids:
- made up of monomers called nucleotides
- make up the DNA and RNA in cells
- nucleotides: adenine (A), cytosine (C), guanine (G), thymine (T) - found only
in DNA, uracil (U) – found only in RNA
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