Transcript Chapter 2 - (www.ramsey.k12.nj.us).

Chapter 5:
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 organic compounds 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

Inorganic Compounds & Functional Groups
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Inorganic compounds
do not contain carbon
– Ex) H2O, O2
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.
Polymerization

During polymerization, building-block molecules
called monomers (small compounds) are joined to
become polymers (complex compounds)

Macromolecules are very large polymers
Monomers
Polymer
Dehydration Synthesis & Hydrolysis
• Dehydration Synthesis: water is removed (-H from one molecule,
-OH from another) so that a bond can form between molecules.
• Hydrolysis: water is added (-H to one molecule, -OH to another)
so that a bond can be broken to separate molecules.
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.
What molecule is released during the
construction of a polymer? What is this process
called?
Draw at least three ways in which five carbon
atoms can be drawn to make different carbon
skeletons.
Compounds of Life (Biomolecules)

There are four groups of organic
compounds that are found in living things.
–
–
–
–
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Carbohydrates
Proteins
Lipids
Nucleic Acids
These compounds all come from our foods
and are needed by our bodies.
DO NOW:
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
Carbohydrates: Monosaccharides
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Sugars
Made of C, H, and O
Can contain 2-7 carbons – most have 5 (pentoses) or
6 (hexoses)
Breaking of their covalent bonds releases energy (food
for cells)
Monosaccharides (single sugars)
– Glucose (sugar green plants produce)
– Galactose (found in milk)
– Fructose (found in fruits)
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
Disaccharides
Formed when two
monosaccharides are
joined by dehydration
synthesis
(condensation)
 Examples:

– Sucrose
– Lactose
– Maltose
Carbohydrates: Polysaccharides

Polysaccharides: complex sugars made up of many
monosaccharides (polymer)

Takes a long time to digest and break down
polysaccharides into glucose through hydrolysis

Taste is not sweet

Starch: used in plants as an energy storage molecule

Cellulose: makes up cell walls of plants; most
abundant compound on Earth

Glycogen: used by animals to store excess sugar
Self-Assessment
1.
2.
3.
Explain the difference between a
monosaccharide and a disaccharide. Give
an example of each.
Compare and contrast starch, glycogen and
cellulose.
How do animals store excess glucose
molecules? (two steps)
Lipids

Non-polar; hydrophobic

Triglycerides (Waxes, oils, fats),
phospholipids and 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
non-polar fatty-acid “tails”
 Amphiphilic (amphipathic)
– Make up plasma membranes

Steroids
– 4 ring structure
– Found in cell membranes
– Base of steroid hormones; bile
salts & vitamin D
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 : Peptides
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A peptide bond is the
covalent bond that joins
amino acids
A Polypeptide is a long
chain of amino acids
Note the water molecule
lost when a peptide bond
is formed –(dehydration
synthesis)
To break a bond, water
would be added
(hydrolysis)
Proteins
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Contains N,H,C, and O
Proteins come from
animal foods
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 shape changes, function
is disrupted, denaturing
Enzymes
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1000’s of chemical
reactions occur in the
body (ex: digestion)
Theses reactions need to
be sped up
Catalysts speed up
chemical reactions by
lowering the activation
energy required to start
the reaction.
Enzymes, a type of
protein, are biological
catalysts
Self-Assessment
State two “everyday examples of proteins.
What are their functions?
 How are amino acids, polypeptides and
proteins related?
 What parts of amino acids are the same
between the 20 different amino acids?
What part is the same?
 Heat can alter the shape of a protein. What
affect will this probably have?

Types of Chemical Reactions
Endothermic
Energy is absorbed (endo = enter)
Exothermic
Energy is released (exo = exit)
Enzymes – A Closer Look
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Enzymes bind to a substrate at an “active site”
Each enzyme is specific to a certain reaction (induced-fit
hypothesis)
Ex: Lactase only works on lactose to break it down into
glucose and galactose. Lactase added to sucrose would
not break it down into it’s monosaccharide monomers
Enzymes
Self-Assessment
Explain the role of activation energy in a
reaction. How does an enzyme affect
activation energy?
 Describe how a substrate interacts with an
enzyme.
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Nucleic Acids
Large molecules composed
of C,H,O, N 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
Self-Assessment
What is the monomer of nucleic acids?
 Draw and label the three parts of a
nucleotide.
 How are the functions of DNA and RNA
related?
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Summary Assessment
Some food labels list the ingredient “partially
hydrogenated vegetable oil.” This means that
hydrogens have been added to some of the double
bonds (creating single bonds instead) in the oil’s fatty
acid chains. Does this make the food more or less
healthy?
 Many humans are lactose-intolerant, meaning they
cannot digest milk products containing the
disaccharide lactose. Use the information learned in
this chapter to hypothesize a cause of lactose
intolerance.
 Which of the three polysaccharides you learned about
in this chapter are most likely found in paper? Explain.
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