COVALENT BOND - hovanscience

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Transcript COVALENT BOND - hovanscience

THE CHEMISTRY OF
LIFE
CHAPTER 2
BEWARE!
SECTION 2-1: THE NATURE OF
MATTER
• REMEMBER from a long, long
time ago…
• Atoms are made up of electrons
(-), neutrons (neutral), and
protons (+)
• If the number of +s in the
nucleus = the number of –s in the
electron shells the atom is stable.
• If not the atom wants to bond.
Bonds
• Ionic bond – when electrons are
transferred from one atom to
another
–Example NaCl
• Covalent bond – electrons are
shared between atoms
–Example H2O
Bonds
• All of what we do in this unit will focus
on different types of COVALENT BONDS
• Now let’s look at the difference between
Polar and NON-Polar Covalent bonds.
BEWARE!
SECTION 2-2: PROPERTIES OF WATER
• Polarity – uneven distribution of
electrons between the hydrogen
and oxygen atoms
– Oxygen is bigger and attracts
the electrons more than
hydrogen
• Hydrogen bonds – slightly positive,
polar H atoms are attracted to
polar negative atoms like O
• Cohesion – attraction between
molecules of same substance
– Water has high surface tension
(allows some bugs to walk on
water)
• Adhesion - attraction between
molecules of different substances
– Capillary action (water moves
up a straw along the sides)
Acids, Bases, and pH
H2O
Water
H+
Proton
+
OH+ Hydroxide
Ion
• pH scale – indicates the
concentration of H+
• pH = 7 = neutral (H+ = OH-)
• Base = pH above 7 (lower H+ than
pure water)
• Acid = pH below 7 (higher H+ than
pure water)
• Buffer – weak acids or bases that
can prevent sharp, sudden
changes in pH
– Example: bicarbonate
http://www.epa.gov/acidrain/education/site_students/phscale.html
LIFE’S BACKBONE
• Most of the compounds that make up
living things contain carbon.
• Carbon makes up the basic structure,
or “backbone,” of these compounds.
• Each atom of carbon has four
electrons in its outer energy level,
which makes it possible for each
carbon atom to form four bonds with
other atoms.
Carbon Backbone
From this guy!!!
And why is he called the cigarette snail?
SECTION 2-3: CARBON COMPOUNDS
• Organic compounds- those
compounds that contain carbon
• Chemical Formulas - show how
many and which atoms are in a
compound
• Structural Formulas - show the
arrangement of the atoms in a
compound
• Isomers - compounds with
the same chemical formula,
but different structure (ex.
propanol and isopropanol)
COVALENT BOND #’S
• Atoms want to fill their
electron shells. An atom
wants to make just enough
bonds to fill its shells.
• H (white) makes one bond
• O (red) makes two bonds
• C (black) makes four bonds
Important Biological Molecules
• What are they?
–Carbohydrates
–Lipids
–Proteins
–Nucleic acids
• We’ll learn about them one at
a time.
CARBOHYDRATES
• Organic compounds
composed of carbon,
hydrogen and oxygen with a
ratio of two hydrogen atoms
to every one oxygen atom
• Made up of smaller units
called simple sugars
(monosaccharides)
USE OF CARBOHYDRATES
• Source of energy for
many living things
• Also used to build body
structures
• Examples: sugar and
starch, cellulose and
chitin
Chitin!
TYPES OF CARBOHYDRATES
• Monosaccharides
• Disaccharides
• Polysaccharides
MONOSACCHARIDES
• Only one sugar molecule
• Examples -glucose, fructose,
and galactose
• All three are C6H12O6, but
they are isomers
• Draw Glucose
DISACCHARIDES
• Double sugars (two
monosaccharides combined)
• Examples: sucrose, lactose, and
maltose
• All are isomers with the chemical
formula C12H22O11
POLYSACCHARIDES
• Long chains of
monosaccharides joined
together
• Examples: starch, glycogen,
and cellulose
• Plants store excess sugar
as starch, and break it down
for energy
Representation of a Polysaccharide
• Humans store excess
sugar as glycogen, &
break it down for energy
• Cellulose used by plants
for structural purposes.
DEHYDRATION SYNTHESIS
• Two molecules join together
by losing a molecule of
water
HYDROLYSIS REACTION
• Larger molecules broken
down into smaller molecules
by the addition of water
Lipids
Aka The Fat
Cat Sat on a
Flat Mat
Section
LIPIDS
• Include fats, oils, steroids &
waxes
• Composed of carbon,
hydrogen and oxygen, but
the # of H atoms per
molecule is much greater
than the # of O atoms
• An example, C57H110O6
Other examples
USES OF LIPIDS
• Stored for energy
• Form basic structure of cell
membranes
• Protection
• Insulation
• Waterproof coverings
THE STRUCTURE OF SOME IMPORTANT
FATS
• Built from 2 basic molecules:
–Glycerol - an alcohol
–Fatty Acids - a long carbon
chain with a -COOH
(carboxyl group) at one end
Triglyceride Structure
Phospholipid Structure
•
http://library.tedankara.k12.tr/chemistry/vol5/polarity%20and%20activity/z247.htm
• Different types of fatty acids:
–Saturated - all single, covalent
bonds in between carbons in
chain
–Unsaturated - one double bond
between carbons in chain
–Polyunsaturated - many
double bonds between
carbons in chain
• Cholesterol - another lipid,
made by animals, both
helpful & harmful
Proteins
Yaw dis is
aboout da
Proteens !
PROTEIN
• Made up of amino acids
linked together
• Composed of C, H, & O as
well as nitrogen, N, and
possibly sulfur
USES OF PROTEINS
• build living materials like
muscle
• act as enzymes to help carry
out chemical reactions
• fight disease
• transport particles into or out
of cells
• act as markers on cells
General
Structure
Alanine
Serine
There are 20 main amino acids
• Each has same basic structure
with the only difference being
the “R” group
• Amino acids are linked by
peptide bonds (formed by
dehydration synthesis)
Essential Amino Acids
• Peptide bond is between two
amino acids
• Polypeptide – (a protein)
many amino acids joined
Amino
acids
Nucleic Acids
Nucleic Acids
• Nucleic Acids are molecules that are
used for the storage of energy or
information.
• Some examples of Nucleic Acids are
DNA (deoxyribonucleic acid), RNA
(ribonucleic acid), and ATP (adenosine
triphosphate)
• Nucleic Acids are made of monomers
called NUCLEOTIDES.
Nucleotides
http://dnatesting.biz/nucleotides.png
• DNA 3D
MATTER AND ENERGY
SECTION 2-4: CHEMICAL REACTIONS
• Chemical reactions always
involve breaking bonds in
reactants and making bonds in
products
• Some reactions release energy
and therefore usually occur
spontaneously
• Other reactions need energy to
happen
• Activation energy – the
minimum amount of energy
needed to start a reaction
• Enzymes are catalysts which
speed up chemical reactions
• Enzymes are proteins that
lower activation energy and
allow reactions to occur at
normal temperatures
Reaction pathway Activation energy
without enzyme without enzyme
Activation energy
with enzyme
Reaction pathway
with enzyme
• Each enzyme is specific and
has a specific shape
• Enzymes are not
permanently changed and
are not used up in the
reaction
• They are continuously
recycled!
• Most enzymes end in -ase
• Reactants are called
substrates
Enzymes
•The area where the enzyme
interacts is called the active site
•Think of the substrate as a flexible
key that must fit into the active site
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Enzyme
Substrates
Products
Active
site
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