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Chapter 3
Vocabulary:
Macromolecule
Monomer
Dehydration reactions
Hydrolysis reactions
ATP
NAD and FAD
Motifs
Domains
Carbohydrates
Nucleic acids
Proteins
Lipids
Outline
3.1 Carbon
6 elements make up macromolecules: C, H, N, O, P, S (arranged like this they resemble
the word chin ups)
C is central to macromolecules because of its chemistry
Functional groups:
Hydroxyl (polar, found in all macromolecules, can hydrogen bond)
Carbonyl (polar, found in carbs and nucleic acids, can hydrogen bond)
Carboxyl (polar, found in proteins and lipids, acidic)
Amino (polar, found in proteins and nucleic acids, weak base)
Sulfhydryl (found in proteins, stabilizes them)
Phosphate (polar, found in nucleic acids, energy storing bonds)
Methyl (non-polar, hydrophobic, found in proteins)
Spending a few minutes on these functional groups helps them understand the
macromolecules better and allows you to revisit bonding.
Monomers
Polymers
Macromolecule – large organic molecules made of covalently bonded repeating subunits
called monomers
Dehydration builds
Hydrolysis breaks
I show a generic example like the one below before showing the bonding between actual
monomers
H-monomer-OH
H-monomer-OH
- H2O
H-monomer—monomer-OH
3.2 Carbohydrates
Major fuel molecule (used as structural material and energy source)
Formula (CH2O)N
Monomer is monosaccharide
Very versatile
Used as monosaccharide (ex. Glucose, fructose, galactose, ribose, deoxyribose)
Disaccharides (ex. Lactose, Sucrose, maltose)
Short chain carbohydrates (used as markers on cell – allow cell to cell
communication, provide mechanism for immune response, self-recognition)
Complex carbohydrates
1)glycogen – energy storage in animals, made in the liver when there’s too much
glucose in the blood. Can be broken down later into glucose and used as energy. Keeps
blood glucose levels stable.
2)starch – energy storage in plants
Glycogen and starch are easily degraded and can be used when necessary for energy.
3) chitin – structural storage in animals (ex. shrimp shells, cockroach crunch)
4) cellulose – structural storage in plants
Chitin and cellulose are designed to be strong and unbreakable. Insect shells provide
protection. In plants the cellulose provides rigidity to plants blowing in the wind.
Cellulose cannot be digested by humans because we lack the enzymes necessary to break
the bonds. Termites and cows have symbiotic bacteria living in their guts that have the
enzymes necessary to break the bonds in cellulose.
Starch has alpha linkages that form valleys. Cellulose has beta linkages that form
mountains. Our enzymes can cross the valley, but not climb the mountain. This is why
there are calories in potatoes, but not lettuce.
3.3 Nucleic Acids
Two main types: DNA and RNA
DNA carries the genetic code
RNA working nucleic acid – responsible for reading DNA and building proteins
Function also as energy molecules (ATP) and
Electron carriers (NADH, FADH2)
Nucleic acids are made of nucleotides
Nucleotides have three parts:
Phosphate group
Nitrogenous base (A, T, C, G, U)
Pentose sugar (ribose or deoxyribose)
DNA
Double helix
Covalent phosphodiester bonds link the sugar of 1 nucleotide to the PO4- group of
another nucleotide by dehydration synthesis
Two strands are held together by weak Hydrogen bonds between complimentary bases
A=T
C=G
The complimentary base pairs have to do with the shape of the bases
A and G are purines and have a double ring structure
T and C are pyrimidines and have a single ring structure
Bases are at the center of the double stranded molecule and essentially form the rungs of
the ladder
RNA
Not as stable, short-term molecule
Working nucleic acid
Single stranded
Uses A, U, C, G
3 types:
mRNA
tRNA
rRNA
Central Dogma of Biology
DNARNAproteins
Transcription
translation
3.4 Proteins
Function as work force of the cell
Proteins made of amino acids (NH3 – C (H, R) – COOH)
20 amino acids
The physical expression of DNA
Large and complicated molecules – shape is integral to function
4 levels of structure:
Primary – string of amino acids
Secondary – folding due to Hydrogen bonds attracting amino acids (can cause
standard shapes of alpha helix, or beta sheet)
Tertiary – folding due to hydrophobic exclusion, ionic bonds and disulfide bonds
(bonds between functional groups with S).
Quaternary – bond to another structure
Shape is more important than linear sequence (Ex. hammer and screw driver)
Motif
Domains
Denaturation
Functions:
Act as enzymes (catalysts for chemical reactions)
Involved in membrane transport
Involved in most types of movement (muscle contractions, flagella, actin and
myosin)
Serve as messengers in the body (hormones such as insulin, growth hormones)
Structural molecules (keratin protein in hair, nails, found in cartilage and
ligaments, collagen)
Cellular transport (hemoglobin carries O2 in the blood)
Defense (Ab in the immune system and venom in snakes)
3. 5 Lipids
Oils, waxes, fats
Non-polar hydrophobic group
Functional group is hydrocarbon chains
Can be saturated (all possible locations have H on them, solid at room temp
because densely packed) or unsaturated (kinks form in the chain due to the presence of
double bonds, liquid at room temperature because cannot order themselves as
strenuously). Trans fats have double bonds, but resemble saturated fats.
Functions of lipids:
Triglycerides are a large energy storage molecules (stored as fat in animals,
provides a huge amount of energy or insulation or cushion)
Waterproof (waxy coatings on plants protect them from drying out, wax coatings
on bird wings)
Hormones (chemical messengers that carry signals)
Vitamins A (vision), D (calcium absorption), E (antioxidant to protect cells), K
(helps form blood clots)
Pigments that gather energy during photosynthesis
Phospholipids are important components of cell membrane.
Has a polar head and a non-polar fatty acid tail.
Steroids (unique chemical structures found in cell membranes. Some hormones
are a type of steroids – chemical messengers)
Waxes that protect, lubricate and lend pliability to hair and skin. Also beeswax
used to build houses.
Cholesterol – important membrane protein that provides rigidity and serves as a
pre-cursor to other sterols and hormones.
75% of cholesterol is make in the liver 25% comes from diet
LDL (low lipo-density) cholesterol is “bad”. It is found in saturated and trans fats.
It clogs arteries and leads to heart attack.
HDL (high lipo-density) cholesterol is “good”. It carries “bad” cholesterol to the
liver for disposal.
There is a lot of chemistry in this chapter! The focus should NOT be on the chemistry; it
should be on the macromolecules. The chemistry of carbon is important (ability to make
4 bonds, how saturated and unsaturated fats satisfy carbon’s octet, why functional groups
confer properties etc). The biochemistry of isomers is NOT important. The chemistry of
bonding is important (covalent bonds between monomers, hydrogen bonds in proteins
and nucleic acids, etc.). The chemistry of molecules is important (polarity of lipids and
how this affects their behavior).
What students need to know about each macromolecule are basically the monomer, the
structure of the monomer, the function of each macromolecule and examples of each.