Transcript Chapter 2

Chapter 2: Chemistry
Raw materials and fuel for our bodies
Lectures by Mark Manteuffel, St. Louis Community College
The Chemistry of LOVE
• “You just feel it!”
• Chemical Structure =
Biological Function
(Shape is a language)
– Endorphins kill pain and
cause pleasure
– Oxytocin (the cuddle
chemical)
– PEA (phenylethylamine
– a natural speed)
No wonder they say love is addictive!
The Birth of
Venus
By Botticelli
Learning Objectives
•





Describe what atoms are, their structure, and
how they bond.
Understand water’s features that help it
support all life.
Describe carbohydrates—their structure and
function.
Describe lipids—their structure and function.
Describe proteins—their structure and
function.
Describe nucleic acids—their structure and
function.
2.1 Everything is made of atoms.

An element is a
substance that cannot
be broken down
chemically into any other
substances.

An atom is a bit of
matter that cannot be
subdivided any further
without losing its
essential properties.
Atomic
Number
and
Atomic
Mass
4 major
elements
that
compose
the human
body…
C, H, N, O
2.2 An
atom’s
electrons
determine
how (and
whether) the
atom will
bond with
other atoms.
Electron Shells
Ions: The
atom
receiving the
electron
becomes
more
negative.
The atom
donating the
electron
becomes
more positive.
Ionic Bonds
result from
equal and
opposite
charges
between ions
and form
compounds.
Covalent
Bonds result
from the sharing
of electrons
between 2 or
more atoms and
form
molecules.
Hydrogen Bonds
Water is a polar molecule.
Covalent bonds, in which
atoms share electrons, are
the strongest.
In ionic bonds, the next
strongest, one atom
transfers its electrons to
another and the two
oppositely charged ions are
attracted to each other,
forming a compound.
Hydrogen bonds, the
weakest, involve the
attraction between a
hydrogen atom and another
polar atom or molecule.
Chemical Reactions: The formation of water
Chemical reactions do not create or destroy matter, they
rearrange it.
02-UNp27-ChemicalReact-L.jpg
 Cohesion
 Large
heat
capacity
 Low
solid
density as a
 Good
solvent
2.5 Hydrogen bonds make water cohesive.
Basilisk Lizard “The Jesus Lizard”
H-bonds
give water
great
cohesiveness.
Cohesion
also
supports
the
transport
of water
through
vegetation.
Heat Capacity
Why do coastal areas have milder, less
variable climates than inland areas?
Why
does ice
float?
Water has
Low
Density as
a Solid.
In this
aqueous
solution,
NaCl is the
solute. By
definition,
water is the
solvent in
any
aqueous
solution.
2.7 Living systems are highly
sensitive to acidic and basic
conditions.
H+ =
Hydrogen ion
OH -
O
H
Ionized Hydroxide
Molecule
H2O
O
H
H
Non-Ionized Water
Molecule
The amount of H+ in a solution is a measure
of its acidity and is called pH.
2.4 A molecule’s shape gives it
unique characteristics.
Shape
determines
function…
Different
shapes
send
different
signals to
your brain.
Molecular
Interactions
and Insect
Mating
Behavior
Biomolecules – Shapes and Functions
Four Types of Macromolecules
(Biomolecules)
Carbohydrates (sugars and starches)
 Lipids (fats, sterols, and phospholipids)



Proteins (made from amino acids)


Long hydrocarbon chains store lots of energy –
energy is released when the chemical bonds are
broken.
specialty functions – includes enzymes and hormones
Nucleic acids (DNA and RNA)

Nucleic acids possess the information to make
functional proteins.
Carbohydrates

C, H, and O

Carbohydrates
are the primary
fuel for running
all cellular
machinery and
also form much
of the structure
of cells in all life
forms.
2.9 Simple sugars are the most
effective source of energy.
 Monosaccharides
Glucose
 Most
carbohydrates
— ultimately
converted into
glucose
 Blood
sugar
Building Giant Molecules:
Macromolecules
Monomers = small molecules
Polymers = a string of
monomers
Dehydration synthesis builds
polymers.
Hydrolysis breaks polymers
apart.
This is the process your cells
use to digest giant molecules
and make their components
available to your cells.
2.10 Complex
carbohydrates are
time-released
packets of energy.
More than 1 sugar
(monosaccharide) unit
 Disaccharides

•
•

sucrose
lactose
Polysaccharides
•
•
•
starch
glycogen
cellulose
2.11 Not all carbohydrates are
digestible.
 Chitin
 Cellulose
The Cellulose in our diet is fiber.
As it moves
through our
digestive system,
it stimulates the
more rapid
passage of food
and possibly
harmful products
of digestion
through our
intestines. Fiber
reduces the risk of
colon cancer.
How do termites digest cellulose?
2.12 Lipids are macromolecules with
several functions, including energy storage.
Why does a salad dressing made with
vinegar and oil separate into two layers
shortly after you shake it?
 Hydrophobic
– non-polar, “water fearing”
 Hydrophilic – polar, “water loving”
 Lipids
are non-soluble in water and greasy
to the touch.
 They are valuable to organisms in longterm energy storage and insulation,
membrane formation, and as hormones.
THREE TYPES OF LIPIDS
FATS
FUNCTION
Long-term
energy
storage and
insulation
STEROLS
PHOSPHOLIPIDS
FUNCTION
Regulate
growth and
development
FUNCTION
Form the
membranes
that enclose
cells
2.13 Fats are tasty molecules too
plentiful in our diets.
 Glycerol:
region
 Fatty
“head”
acid “tails”
 Triglycerides
Fat molecules contain much more stored
energy than carbohydrate molecules.
Saturated vs. Unsaturated Fats


# of bonds in the hydrocarbon chain in a fatty acid
Health considerations
 Many
snack foods contain “partially
hydrogenated” vegetable oils.
What are
trans fats?
2.15 Proteins are versatile macromolecules
that serve as building blocks.
20 different
amino acids
are strung
together in
different
combinations
to provide a
huge variety of
important
functions.
2.16 Proteins are an essential
dietary component.
 Growth
 Repair
 Replacement
Food labels indicate an
item’s protein content.
Why is this insufficient for
you to determine whether
you are protein deficient,
even if your protein intake
exceeds your
recommended daily
amount?
Complete Proteins
Have all 8
essential
amino
acids –
Cannot be
made by
our bodies
and must
be
consumed.
2.17 Protein functions are influenced by
their three-dimensional shape.
 Peptide bonds
Primary Structure
 The
sequence of
amino acids
 Each aa is like a
letter in a chain
that spells a
word.
 How are amino
acids joined
together?
Secondary Structure
 Hydrogen
bonding
between amino acids
 The two most common
patterns:
• twist in a corkscrew-like
shape
• zig-zag folding
Tertiary Structure
 Folding
and
bending of the
secondary structure
 Due
to bonds such
as hydrogen bonds
or covalent sulfursulfur bonds.
Quaternary Structure
 When
two or more
polypeptide chains
are held together by
bonds between the
amino acids on the
different chains.
 Hemoglobin
 Egg
whites contain a lot of protein.
 Why does cooking them change
their texture and color?
Summary: Protein Structure
and Function

The particular amino acid sequence of a protein
determines how it folds into a particular shape.

This shape determines the protein's functions,
such as which molecules it will interact with.

When a protein's shape is deformed
(denaturation), the protein usually loses its
ability to function.
2.18 Enzymes are proteins that
initiate and speed up chemical
reactions.
“Misspelled” Proteins and Enzyme
Inhibitors
 Mutations
in a person’s DNA or mistakes in
the translation process can lead to an
incorrect amino acid sequence.
 This
may result in active site disruptions.
 Chemicals
called inhibitors can also disrupt
the active site.
 Directly
or indirectly
Why do some adults get sick
when they drink milk?
Enzyme Inhibitors disrupt enzyme function by
blocking the substrate or changing the shape of the
active site.
Inhibition
can be
good or
bad.
Two Types of
Nucleic Acids

Deoxyribonucleic
acid (DNA)

Ribonucleic acid
(RNA)

Both play central
roles in directing the
production of
proteins.
Information Storage
The information in a molecule of DNA is
determined by its sequence of bases.
 Adenine, guanine, cytosine, and thymine

Base pairing:
A&T
G & C
 What is the complimentary strand to this strand:
CCCCTTAGGAACC?

2.20 DNA
holds the
genetic
information
to build an
organism.
2.21 RNA is a universal translator,
reading DNA and directing protein
production.
In what three important ways does
RNA differ from DNA structurally?
 The
sugar molecule of the sugarphosphate backbone: ribose vs.
deoxyribose
 Single-stranded
 Uracil
(U) replaces thymine (T)
Evolutionary biologists use fossil history and differences in
amino acid sequences of proteins to construct evolutionary
tape measures.
You are what you eat!
• Eat mostly plants, especially leaves.
– Our early ancestors possessed the biological ability to
make vitamin C from scratch.
– But there was so much vitamin C in our plant-rich diet
that over time we lost the ability to make the compound
ourselves.
– Our biological dependence on plants runs deep.
– Why not just take vitamin C supplements?
• Plants also contain omega-3’s, fiber, other
antioxidants and vitamins, and all in nature’s healthy
balance.
– Why are wild plants generally more nutritious than
crops?
• Soil differences?
• Breeding for quantity not quality?
Purslane: High in Calcium and Iron (slightly more
than Spinach or Swiss Chard – 3 x more than other
garden vegetables)
Pigweed: Twice as much protein, 3 x more Calcium,
and 10 x more vitamin A than many garden vegetables,.
You are what you eat eats too.
• For meat eaters:
– Grass-fed animals have healthier fats (more
omega-3’s) and higher levels of vitamins and
antioxidants.
– Factory farms use a high levels of growth
hormones and antibiotics
– Grain-fed animals may ingest large quantities
of pesticides.
– Fish-meal fed animals may ingest large
quantities of heavy metals.