Introduction to macromolecule
structure / function
Macromolecule types
1)
carbohydrates
2)
fats
3)
nucleic acids
4)
proteins
Big and small …

Simplest unit = monomer

Many monomers together = polymer

Many can polymerize indefinitely
(exception: fats)
Putting together

= dehydration synthesis

Uses: storage, construction

Reaction also produces H2O molecule
(H and OH ripped off, combine)
Dehydration synthesis
Example: carbohydrate synthesis
Example: peptide synthesis
Example: DNA synthesis
H2O
Breaking up polymers

= hydrolysis – using water to split a
polymer
(also splits water itself as H is added to
one side, OH to other)

Uses: digestion, defense, recycling
Hydrolysis – general example
Carb hydrolysis
Macromolecule overview
1) carbohydrates

Roots: –ose (not all the time)

Components: C:H:O ~ 1:2:1 ratio

monosaccharide is monomer
Carbohydrate functions
a) Quick energy
ATP
glucose
glycogen – animals
starch - plants
unstable
immediate usage
fats
(converted
carbs)
stable
long-term storage
Carbohydrate functions
b) Structural support

Cellulose – plant
cell walls

Chitin – fungal cell walls
(also arthropod exoskeletons)
Carbohydrate functions
c) Cellular identification

Glycoprotein – sugar ID tag attached to
membrane protein – (we’ll study more in
ch. 43 – immune system)
Fig. 7.9d
white blood cell
recognizes ID tag by
binding to it, does not
attack this cell
human body cell
with carbohydrate ID tag
Macromolecule overview
2) Lipids (fats – solid, oils – liquid)

Components: CHO (lots more CH than
carbs)
fatty acids
glycerol
Fat synthesis
can be repeated with two other fatty acids
= triglyceride
Lipid functions

a) Energy storage

b) Insulation

c) Cell membrane component
(phospholipids)
Macromolecule overview
4) Proteins

Roots: -ase (for many enzymes)

Components: CHONS
(sulfur present in certain amino acids)

Monomer: amino acids
Protein functions - EVERYTHING
a)
enzymes – speed up chemical reactions
b)
c)
transport proteins – let certain materials in /
out of cell
motor proteins – move things around in cell
d)
receptor proteins – receives signals sent to cell
e)
transcription factors – binds to DNA to regulate
protein production)
(and more … this is just a sample)
Protein structure / function

How is diversity of function possible?

How is specificity possible (each protein
only interacts with one particular
component)?

Answer: each protein has unique
conformation (= 3-D shape) to interact
with particular component
Protein monomer

Amino acid
abbreviation for
the unique side
chain of each
amino acid
ic acid
How get a unique 3-D conformation?

Must have unique combination of bonds that
hold it in its precise shape

We will talk about different types of bonds
that form as a protein folds up
1)
2)
3)
4)
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
* Really important,
please study carefully
Primary structure
= which amino acids combined in which order



order prescribed by DNA
code, constructed by
ribosomes.
type of bond formed:
peptide bond
this forms the polypeptide
(which must fold into 3-D
shape to be called a protein)
Secondary structure

Interactions between “core” parts of amino acids
(amino and carboxyl groups) that used to be far
away

Type of bond: hydrogen bonding
(O—H
N—H attractions)

Because all amino acids have these parts, repeated
hydrogen bonding forms two possible shapes:
α-helix or β-pleated sheet
Secondary structure
α helix
Tertiary structure

Additional bonds between side chain “R”
groups of amino acids

Many types of
bonds possible
(depends on R
groups interacting)
Amino acid interactions
might seek out
other polar AAs
nearby and
hydrogen bond
(+) AAs might seek out (-)
AAs and make ionic bonds
Amino acid interactions
might be pushed
by water into
clustering in a
hydrophobic
region
Quaternary structure

(Not all proteins)

Sometimes overall protein =
combination between multiple
polypeptide subunits

Type of bond: depends
(probably hydrogen
bonding)
Result of all that bonding

Uniquely shaped protein

We will focus first on one subgroup:
enzymes – bind to a specific substrate to
speed up a chemical reaction
Sample enzyme - sucrase

Speeds up the hydrolysis of sucrose
active
site of
enzyme
4. enzyme’s active site
is open for another
substrate molecule to
collide (reusable)
1. enzyme and
substrate molecules
must collide
2. enzyme helps
chemical reaction
occur
3. product molecules
do not fit well in active
site, so they leave
Environmental factors affect enzymes

Also discussed in lab 2 introduction
1)
temperature changes
2)
pH changes
3)
salt concentration changes
Temperature and enzyme activity

Below optimum (as it gets “cold”) , reaction rate drops
because fewer enzyme / substrate collisions

Enzymes do NOT denature in cold temperatures
Temperature and enzyme activity

Above optimal temperature, reaction rate quickly drops
as heat energy breaks weak bonds holding protein
conformation = denaturation

Can no longer bind to substrate = zero activity
pH and enzyme activity

Unlike temperature, different enzymes have different ideal pH
environments

Too much H+ (too acidic) or OH- (too basic) can disrupt
electrical attractions, bonds that give protein shape
Salt concentration and enzymes

Ideal salt concentration may differ for
different enzymes also

Salts may interfere with electrical
attractions within protein structure
(hydrogen / ionic bonding)

Salt levels also affect water balance in
cells
Maintaining environments

A balanced temperature, pH, and salt
concentration must be maintained for
protein activity (and survival)

Using energy to maintain a balance =
homeostasis

Cell level homeostasis

Overall body homeostasis = temp, pH and
salt levels
Cell regulation of enzyme activity

Cells want to control overall enzyme activity
a) regulate enzyme production levels
(regulate DNA transcription)
b) regulate how active these existing enzymes are
Two types of inhibitors
uninhibited enzyme
(substrate can bind)
competitive inhibitor – noncompetitive inhibitor –
molecule directly blocks molecule binds to
active site
allosteric site and changes
active site shape so
substrate cannot bind
Another example of binding site

ATP often
transfers a
phosphate to
binding site to
activate
protein
Inhibitor / enzyme balance

Most inhibitors bind weakly and reversibly
to proteins

Enzyme regulation = balance of inhibitors
moving randomly, binding and falling off
enzymes

Many of the strongest poisons are
irreversible protein inhibitors (ex: cyanide)
Feedback inhibition

Best inhibitor is
often the end
product itself

Got enough
product? =
enzymes blocked

Too little product?
then few inhibitors
= enzymes active