LARGE BIOLOGICAL MOLECULES
Chapter 5
FUEL FOR LIVING SYSTEMS
Large molecules are important for the basic
processes of life
 Grouped into 4 classes of organic compounds

Carbohydrates*
 Lipids
 Proteins*
 Nucleic acids*

Important to know how these are made, stored,
and destroyed
 Also, structure and function

* are considered macromolecules
POLYMERS

Chain of similar repeating units linked by
covalent bonds
E.g CAT-CAT-CAT-CAT=CAT-CAT or the alphabet
 Carbs, proteins, and nucleic acids are examples


The similar repeating units are called
monomers
E.g CAT or any letter of alphabet
 Joined and broken by reversible reactions


Enzymes can speed the reaction
 E.g digestion: cells need organic molecules broken down
so can be absorbed after which they can be rebuilt
POLYMERS
Making polymers

Breaking polymers
Dehydration reaction
Links monomers
 Loss of water for each
monomer added
 Forms a covalent bond

1
2

Hydrolysis reaction
Breaks polymers
 Addition of water for
each broken bond

4
3
1
1
2
3
2
3
4
4
1
2
3
4
EXAMPLES OF POLYMERS
Small molecules are ordered to dictate life
 DNA is a polymer composed of 4 monomers
(nucleiotides)



Creates variation based on arrangement
Proteins are polymers from 20 different amino
acids (AA’s)

Sequence variation separates humans from flowers and
individuals from individuals
CARBOHYDRATES

Simple sugars and polymers of simple sugars

Sugars are broken down based on the number of
polymers
Monosaccharides
 Disaccharides
 Polysaccharides



Each is joined by a dehydration reaction
Polymers of sugar are actually what is generally
considered a carbohydrate or starchy food
MONOSACCHARIDES

Glucose is most common
Major nutrient for cells
 Respiration, fuel for cellular work, and raw material


Trademarks of sugars
Molecular repeating unit of CH2O Carbonyl and hydroxyl functional groups
 3-7 carbons long

Hexoses (6 carbons, e.g glucose and fructose)
 Pentoses (5 carbons, e.g ribose and dioxyribose)


End in “-ose”
GLUCOSE VS FRUCTOSE
Also are examples of what?
DISACCHARIDES

2 monosaccharides
joined by a covalent
bond
Result of dehydration
reaction
 Form a glycosidic
bond/linkage


Maltose
glucose + glucose
 Whoppers, malts, beer


Sucrose
Glucose + fructose
 Table sugar
 Plant sap


Lactose

galactose + glucose
POLYSACCHARIDES
Multiple glycosidic linkages
 Storage material until needed


Hydrolysis will break apart to provide sugars to cells
Building materials for cell protections
 4 types

Starch
 Glycogen
 Cellulose
 Chitin

POLYSACCHARIDES FOR STORAGE

Starch
Polymer of many glucose monomers
 Plants use as storage

Form of plastids
 Stockpiled glucose = stored E



E.g potatoes, grains, wheat, and corn
Glycogen
More branched polymer of glucose
 Vertebrate storage in liver and muscles

Hydrolyzed when sugar is needed
 Not good for long term because depleted quickly

CELLULOSE
Cell wall of plant cells
 Most abundant organic compound on Earth
 Polymer of glucose with different linkages
 Straight molecule, grouped to form microfibrils =
strong



Major component of paper and only of cotton
Most animals can’t hydrolyze
Undigested, stimulates GI tract through abrasion to
stimulate mucous secretion
 Most fresh fruits, vegetables, and whole grains


Insoluble fiber on packages
CHITIN

Composes arthropod exoskeletons
CaCO3 covers body and hardens
 Molted off and commonly eaten as Ca2+ source

Cell walls in fungi
 Used for surgical thread


Dissolvable stitches
LIPIDS

‘Grab bag’ of
molecules


Not true polymers
Not really big enough
to be macromolecules
All mix poorly with
water due to
hydrophobic nature
(hydrocarbon chains)
 Form ester linkages
 3 types

Fats
 Phospholipids
 Steroids

FATS

Glycerol (alcohol w/ 3 carbons) and fatty acids
(16-18 carbons and carboxyl end)

Hydroxyl and carboxyl linkage = ester linkage
(triglyceride)
Can be saturated or unsaturated
 Hydrogenated vegetable oils


Unsaturated synthetically to saturated by adding
hydrogens
Peanut butter and margarine to prevent separation
 Trans fats when conversion changes conformation of
double bond


Necessary for energy storage (hydrogen bonds)
More compact, better for mobility
 Adipose storage


Cushions vital organs and insulates
SATURATED VERSUS
UNSATURATED CHAINS
Saturated



All single
bonds with H
Most animal
fats
Solid, close
bonds; e.g
butter
Unsaturated



Carbon carbon
double bonds
Most plant
and fish fats
Liquid, can’t
bind close =
bend; e.g olive
oil
PHOSPHOLIPIDS
Makes up cell membranes
 Glycerol with 2 FA’s and 1
phosphate (negative charge)

Hydrocarbons make
hydrophobic (form tails)
 Phosphate and attachment
are hydrophilic (form heads)


Bi-layered to protect
hydrophobic from water
STEROIDS
Lipids with 4 fused rings
 Synthesized from cholesterol, common in
animal cell membranes
 Precursor to sex hormones
 Synthetic variants


Anabolic steroids (Testosterone)
PROTEINS
Necessary for almost anything living organisms
do
 Know types and functions from table 5.1


Enzymes regulate metabolism by acting as catalysts

Speed reactions w/o being consumed
Unique 3D shapes
 Formed from polypeptides (polymers of amino
acids)

20 AA’s, same set for all
 Protein = 1+ polypeptide folded and coiled into
specific 3D shape

AMINO ACID MONOMERS

Common structure
Carboxyl and amino group
 α-carbon is middle with H
and R group (variable)



Determines specific AA
from fig. 5.17
Side chains grouped by
properties
Nonpolar, hydrophobic
 Polar, hydrophilic
 Acidic, (-) charge b/c
carboxyl group
 Basic, (+) charge b/c amino
group



Charges = hydrophilic
Polymers formed by
peptide bonds
STRUCTURE AND FUNCTION
Polypeptides ≠ protein
 AA sequence does
 4 levels of structure

1°-seq of AA, determined by genes
 2°-repeated coils or folds for overall shape

H-bonds b/w carboxyl and amino backbone
 α-helix = H bonds b/w 4th AA
 ß-pleated sheet = 2+ regions of H bonds


3 °- interactions b/w side chains
Hydrophobic interaction = side chains cluster in
 Disulfide bridges = -SH side chain interactions


4°-overall structure of 2+ polypeptides
PROTEIN STRUCTURE AND FUNCTION
Polypeptides ≠
protein
 1°: genes decide
 2°: H-bonds b/w
carboxyl and amino
 α-helix: 4th AA
 Β-sheet: 2+
regions of side by
side H-bonds
 3°: hydrophobic side
chains and disulfide
bridges
 4 : 2+ polypeptides

CHANGING PROTEIN STRUCTURE

Sickle cell

Single AA substitution in hemoglobin


Abnormal shape RBC’s that clogs vessels
Denaturation
Proteins unravel and lose shape
 pH, [salt], temp, and other effects can cause
 Inactivates proteins



Removing agents might reverse
Misfolding
Accumulate and cause detrimental problems
 E.g Alzheimer’s and Parkinson’s disease

PROTEIN MISFOLDING
Often times
unfolding
exposes
hydrophobic
areas to the
aqueous
solutions
surrounding the
protein
Aggregates to
protect itself
NUCLEIC ACIDS

Polymers of nucleotides (polynucleotides)


Blueprint for proteins to control all of cellular workings
Control of reproduction

DNA
RNA
proteins
Central dogma of molecular biology
 Occurs in ribosomes


Monomer is a nucleotide

Structure consists of 3 components
Nitrogenous base
 5 carbon sugar
 Phosphate group

NUCLEOTIDE

Nitrogenous base

Pyrimidine = a 6 member carbon and nitrogen ring


cytosine (C), thymine (T), uracil (U)
Purines = 6 member carbon ring fused to a 5 member
ring (smaller name, bigger structure)

adenine (A) and guanine (G)
DNA – C, T, G, and A
 RNA – C, U, G, and A


5 Carbon sugar
Ribose
 Deoxyribose (missing oxygen)

NUCLEOTIDE POLYMERS

Phosphodiester linkage = phosphate joins
sugars of 2 nucleotides
For backbone of DNA
 Phosphate on 5’ carbon joins hydroxyl on 3’ carbon

DNA codes 5’ -3’
 Sequence of bases unique to each gene


Linear order of nitrogenous bases in a gene
specifies AA sequence (which level of structure ?)

Start codon


ATG and AUG = DNA and RNA
Stop codon

UAG, UAA, UGA
DOUBLE HELIX

1st proposed by
Watson and Crick
Sugar-phosphate
backbones are
antiparallel
 Nitrogenous bases face
in and H-bonds hold
them together

2 strands are
complementary
 Binding specific

A binds w/ T
 G binds w/ C
