Transcript Proteins - (www.ramsey.k12.nj.us).

Chapter 3:
The Molecules of Life
Organic Compounds
Compounds in the natural
world that contain the
element carbon (bonded to
hydrogen).
 Hydrocarbons – contain only
C & H (ex. CH4)
 Most also include oxygen and
some also have nitrogen,
phosphorus and sulfur.
 Carbon can form thousands of
different compounds because
it can form 4 strong covalent
bonds

Variations in Carbon Skeletons
Functional Groups
A group of atoms within
a molecule that interacts
in predictable ways with
other molecules is called
a functional group
 Functional groups
determine the properties
of organic molecules.
For example, hydrophilic
groups (such as –OH)
attract water and
hydrophobic groups
repel.

The Process of Polymerization

The formation of carbon-based compounds

Monomers (small compounds) become Polymers
(complex compounds)

Macromolecules are very large polymers
Monomers
Polymer
Dehydration Synthesis & Hydrolysis
Compounds of Life (Biomolecules)

There are four groups of organic
compounds that are found in living things.
–
–
–
–

Carbohydrates
Proteins
Lipids
Nucleic Acids
These compounds all come from our foods
and are needed by our bodies.
Self-Assessment

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
Draw a molecule that has a 3-C (carbon)
skeleton and a hydroxyl group on the middle
carbon. (Hint: formula is C3H8O)
Explain the connection between monomers and
polymers.
Draw at least three ways in which five carbon
atoms can be drawn to make different carbon
skeletons.
What molecule is released during the
construction of a polymer? What is this process
called?
Try This:
The diagram below shows two amino acids, the monomers
of a protein. Draw these amino acids in your notes. What
has to happen for these two molecules to combine? (What
must be done for bonds to be made in biological systems?)
Represent this process by redrawing the amino acids
bonded together and drawing the bi-product formed.
Dehydration Synthesis
In living systems, bonds are made by removing water. An –
OH from one molecule and an –H from the other combine
to form water. The removal of these atoms provides
“space” for the new bond to form, by leaving atoms with
unfilled valence shells.
Carbohydrates
An Example of Isomers
The formula for all three monosaccharides glucose,
fructose and galactose is C6H12O6
 Although they contain the atoms in the same
proportion, their structural arrangement differs.

In aqueous solutions,
most monosaccharides
form ring structures as
shown for glucose
Also note the trademark
functional groups of
sugars, multiple hydroxyl
groups and a carbonyl
group
Is fructose an aldose or a ketose?
Is glucose an aldose or a ketose?
Carbohydrates: Monosaccharides

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Sugars
Made of C, H, and O
Can contain 2-7 carbons
– most have 5 (pentose) or 6 (hexose)
Trademarks: 1 carbonyl group & multiple hydroxyls
– Hydroxyl group makes a sugar an alcohol
– Carbonyl group makes it either an aldose (aldehyde sugar) or a
ketose (ketone sugar)
Breaking of their covalent bonds releases energy (fuels cellular work)
Monosaccharide Examples (single sugars)
– Glucose (sugar green plants produce)
– Galactose (found in milk)
– Fructose (found in fruits)
Three Ways to Represent Glucose
Disaccharides
 Formed by the dehydration synthesis of 2
monosaccharides
 Examples:
– Sucrose
– Lactose
– Maltose
Carbohydrates: Polysaccharides

complex carbs made up of 100s-1000s of
monosaccharides (glucose)

Takes a long time to digest and break down
polysaccharides into glucose through hydrolysis
Taste is not sweet
 Examples:

 Starch: used in plants as an energy storage molecule
 Cellulose: makes up cell walls of plants; most abundant
compound on Earth
 Chitin: found in exoskeleton of insects and crustaceans and
the cell walls of fungi
 Glycogen: used by animals to store excess sugar (liver &
muscles)
Self-Assessment
1.
2.
3.
4.
Write the formula for a monosaccharide
that has 3 carbons.
Why do isomers, which have the same
formula, have different properties?
Explain the relationship between a
monosaccharide and a disaccharide. Give
an example of each.
Compare and contrast starch, glycogen,
cellulose and chitin.
Lipids

Non-polar; hydrophobic

Three categories:

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Triglycerides
Phospholipids
steroids

Contain C, H & O, but lower
proportion of oxygen than carbs

Lipids store more energy than
carbohydrates because they
have twice as many energy rich
(C-H) bonds than carbohydrates.
(9 cal/g v. 4cal/g)
Categories of Lipids

Trigylcerides (Neutral Fats)
– Glycerol & 3 fatty acids “tails”
– Fatty tissue – insulation & reserve
energy

Phospholipids
– Polar phosphate “head” and nonpolar fatty-acid “tails”
 Amphiphilic (amphipathic)
– Make up plasma membranes

Steroids
– 4 ring structure
– Ex) Cholesterol
 helps provide support in animal cell
membranes
 Start material for other steroids,
such as hormones
Categories of Triglycerides
 Saturated -carbons are
joined by all single bonds
(not healthy)
 Unsaturated -2 carbons are
joined by a double bond
 Polyunsaturated -carbons
have many double bonds
(most healthy)
Self-Assessment
1.
2.
3.
4.
What property do all lipids share?
What are the parts of a fat (triglyceride)
molecule?
Describe two ways that steroids differ from
fats.
What does the term “unsaturated fat” on a
food label mean?
Proteins

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A peptide bond is the
covalent bond that joins
amino acids
A Polypeptide is a long
chain (100+) of amino
acids
A (functioning) protein is
one or more polypeptide
chains precisely coiled,
twisted and folded into a
unique three-dimensional
shape
-Note dehydration synthesis reaction
involved in forming a peptide bond.
- How is a peptide bond broken?
Proteins
Contains N,H,C, and O
 Proteins come from animal foods
 Examples: (very diverse group)

– Enzymes (biological catalysts)
– Structural (hair, connective tissue, such as
ligaments & tendons)
– Defensive (antibodies)

Proteins are polymers of Amino Acids
– All 20 amino acids are similar except for an
“R” group


A proteins amino acid sequence
determines it’s shape which determines
its function.
If the shape changes, function is
disrupted and protein is denatured.
Structural Levels of a Protein
• Primary: sequence of chain
of amino acids
• Secondary: AA sequence
linked by H-bonds into an
alpha-helix or Beta-pleated
sheet
• Tertiary: Attractions
between helixes and/or
sheets (usually R-groups)
lead to further coiling into a
3D shape (globular or
fibrous)
• Quaternary: 2+ polypeptide
chains (sub-units)
Nucleic Acids
Large molecules composed
of N,H,O, C and P.
 The monomers are called
nucleotides
 Two types of nucleic acids
are RNA and DNA
 DNA:

 Hereditary info: Directions
for making proteins
 Controls cellular activities

RNA:
 Carries out the instructions
of DNA to make proteins
DNA & RNA Structure