Transcript Enzymes - TeacherWeb

The Chemistry of Life
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Atoms
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All things are made of atoms
Atom -basic unit of all matter
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Normally it is electrically neutral (no
charge)
Made up of
 Protons
 Neutrons
 Electrons
1 water molecule, H2O,
has 3 atoms (2 H and 1 O)
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Atoms

The nucleus is the
center of the atoms and
it contains protons and
neutrons
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Protons + charged particle
 Heavy
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Atoms
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Neutrons Neutrally charged
particle
 Heavy
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Atoms

The electrons zip around the
outside of the nucleus
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Electrons - charged particle
 Light
Most atoms are electrically
neutral so the + protons =
the - electrons
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Elements
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Element-pure substance that consists of just
one type of atom
114 elements in the periodic table
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Have a 1 or 2 letter
symbol
C = carbon
 N = nitrogen
 H = hydrogen
 S = sulfur
 O = oxygen, etc.
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Is water an element?
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Elements
Elements are identified by their number of
protons
Atomic Number=
 Different elements have a
# of protons
different number of protons
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C
Carbon
12.011
Atomic Mass=
7
Where is Sodium?
What is its atomic number?
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Elements
Atomic Number= 11
# of protons
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Na
Sodium
22.990
Atomic Mass= 23
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Elements
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The electrons of an element determine
its properties and reactivity
They move around the nucleus
in energy levels
 Different energy levels hold
different numbers of electrons
 Full and stable: 2 (1st), 8 (2nd), 8 (3rd)
electrons, starting from the center
 Is the carbon atom stable?
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Isotopes
 Isotopes--atoms of same element w/ a
different # of neutrons
 Some are radioactive, some are not
Isotopes of Carbon
Nonradioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
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Radioactive Isotopes
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Isotope with unstable
nucleus due to extra
neutrons
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Break down at a constant rate
Give off dangerous radiation
Have uses too
 C-14 dating
 Cancer treatment
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Bonds
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Bonding -for some atoms to be stable they
must gain, lose, or share electrons with
another atom.
Stability of atoms is based on electrons
2 types of bonds
-Ionic
-Covalent
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Bonds
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Ionic bonds - electrons transferred from
one atom to another
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Normal atoms are electrically neutral, so with
this transfer they gain a charge and form
ions- charged atoms
The oppositely charged ions attract forming
the ionic bond
NaCl has ionic bonds
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Bonds
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Covalent bonds --sharing
electrons
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Stronger than ionic
Molecule--formed when
atoms are joined in a
covalent bond
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Water
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Water covers ¾ of Earth’s
surface
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Most abundant molecule in
living things
Universal solvent…dissolver of
many substances found on
Earth
Connects all parts of the world
with others.
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Properties of Water
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Water has polar, covalent
bonds
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Covalent- H and O share
electrons
Polar- sharing is unequal
Oxygen “pulls” harder on
negative electrons and gives
it slight negative charge.
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Properties of Water
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Opposite charges of polar
molecules can interact to
form hydrogen bonds
 H (+) attracts O (-) like a
magnet
 Gives water special
properties
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Solutions
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Many substances dissolve in water
Solutions occur when one
substance is dissolved
in another
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Solute -gets dissolved
Solvent -does the dissolving
Saltwater
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Acids, Bases, and pH
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Solutions have a pH
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Chemical property to describe
how acidic or basic it is
An acid releases a hydrogen
ion (H+) when it dissolves;
bases take them up
pH scale from 0-14
 Pure water neutral: pH7
 Acids:<7
 Bases: >7
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Buffers
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Human homeostasis-human
blood must be b/t pH 6.77.5
Body uses buffers, which are
weak acids or bases, to
neutralize sharp changes in
blood pH
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Carbon
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Carbon atoms are the
building blocks of life
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Carbon atoms only have 4
electrons in their outer energy
level (recall 8 is stable), so
they want to bond
They are the basis of most
molecules that make up living
things
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Organic Macromolecules
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Long chains of carbon subunits are called
organic macromolecules
have C-C bonds
large molecules
 Each smaller molecule is a subunit called a
monomer
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Organic Macromolecules
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4 types of organic macromolecules found
in living things
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Carbohydrates
Lipids
Nucleic Acids
Proteins
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Carbohydrate Structure
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Composed of C, H and O
Carbs include sugars and starches
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Sugars
 Called monosaccharides
 Basic carbs that are simple sugar
monomers
 Sucrose (table sugar), glucose
(made in photosynthesis)
MONOSACCHARIDES (SUGARS)
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Carbohydrate Structure
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Starches
 Called polysaccharides
 Complex carbs that
are polymers made of
monosaccharide
monomers
 Pasta, potatoes,
cellulose (cell walls
of plants)
MONOSACCHARIDES (SUGARS)
POLYSACCHARIDE
(STARCHES)
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Carbohydrate Function
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Main source of energy for living things
 Converted
to ATP—
gasoline for cells
 Monosaccharides =
immediate E
 Polysaccharides =
longer term E
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Plants store carbs as
cellulose which gives their cells strength
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Lipid Structure
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Composed of C and H
Lipids are polymers made of fatty
acid and glycerol monomers
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Fats, oils, waxes are lipids
Saturated and unsaturated fats
Nonpolar so hydrophobic or ”waterfearing”-not dissolvable in water
FATTY ACIDS AND GLYCEROL
LIPID
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Lipid Function
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Store energy for use later
Hormones
Cell membranes
Waterproof covering (skin)
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How much fat does pop have?
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What organic macromolecule is the main ingredient?
Nucleic Acid Structure
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Made of C, H, O,P (phosphorus) and N
(nitrogen)
Nucleic acids are
polymers made of nucleotide
monomers
NUCLEOTIDES
NUCLEIC ACID
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Nucleotides
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Each nucleotide is
made of 3 parts
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Phosphate group
5 Carbon sugar
Nitrogen base (A,
C, T, G as they are
known in DNA)
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Nucleic Acid Function
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Store and transmit
hereditary (genetic) info
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DNA
RNA
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Protein Structure
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Composed of C, N, O, and H
Proteins are polymers made of amino acid monomers
 20 different amino acids form 1000’s of different
proteins
AMINO ACIDS
PROTEIN
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Protein Structure
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Proteins differ in the number and sequence of the
20 different amino acids
The sequence of amino acids
determines a protein’s
structure (shape), and therefore,
function
 If
the shape is ruined, so is the protein’s
function
 This is the basis of many diseases
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Protein Function
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Enzymes-special proteins that control
chemical reactions
Form bones and muscles
Forms hair and nails (keratin)
Also part of cell membrane with
lipids
Food source: steak, eggs, nuts, cheese
PROTEINS ARE NOT MAJOR SOURCES OF
ENERGY!
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Inorganic
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Inorganic –molecules
that don’t have C-C
or C-H bonds
NaCl, H2O
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Chemical Reactions
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Everything occurring in an
organism is based on chemical
reactions- process that changes
one set of chemicals into
another set
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Slow (rusting) or fast (burning)
Breaking and remaking of bonds
Reactants-products
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Chemical Reactions
Reactant(s)
Product(s)
carbon + oxygen
carbon dioxide + energy
CO2 + energy
C + O2
O
C
O
C
O
+ energy
O
black solid
colorless gas
colorless gas
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Energy in Chemical Reactions
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Reactions involve changes in energy
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Some reactions release energy
 Burning
 Digestion of carbs and lipids
Some must absorb energy to occur
ATP- form of energy absorbed or released when
bonds are made or broken (“cell gasoline”)
 Animals get our ATP and organic
macromolecules for body processes from food
 Plants get it from?
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Chemical Reactions and Enzymes
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Some reactions are too slow
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They need lots of energy (ATP) to jump start them
This energy is called activation energy
Others are too fast and need to be slowed or
neutralized
Activation energy
Reactants
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Products
Chemical Reactions and Enzymes
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Enzymes are the specialized proteins that
control, or catalyze, chemical reactions in living
things
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Digestion, nervous system
signals, etc. all require them
Substrates are the particular
reactants an enzyme acts on
in a chemical reaction
They fit like a lock and key
 If the shape is ruined, so is the protein’s function
 This is the basis of many diseases
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What Are Enzymes?
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Most enzymes are
Proteins (tertiary
and quaternary
structures)
Act as Catalyst to
accelerates a
reaction
Not permanently
changed in the
process
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Enzymes
Are specific for
what they will
catalyze
 Are Reusable
 End in –ase
-Sucrase
-Lactase
-Maltase
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How do enzymes Work?
Enzymes work by
weakening
bonds which
lowers
activation
energy
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Enzymes
Without Enzyme
With Enzyme
Free
Energy
Free energy of activation
Reactants
Products
Progress of the reaction
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Enzyme-Substrate Complex
The substance
(reactant) an
enzyme acts on
is the substrate
Substrate
Joins
Enzyme
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Active Site
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A restricted region of an enzyme
molecule which binds to the
substrate.
Substrate
Active
Site
Enzyme
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Induced Fit
A
change in the
shape of an
enzyme’s active
site
 Induced by the
substrate
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Induced Fit
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A change in the configuration of an
enzyme’s active site (H+ and ionic
bonds are involved).
Induced by the substrate.
Active Site
substrate
Enzyme
induced fit
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What Affects Enzyme
Activity?
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Three factors:
1. Environmental Conditions
2. Cofactors and Coenzymes
3. Enzyme Inhibitors
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Environmental Conditions
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Enzyme activity can be
affected by many variables,
some of which due to
altering the protein’s shape
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pH can alter shape and
function
Temperature can alter shape
and function
Enzyme concentration can
affect how many reactions can
occur: more enzyme=more
activity
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2. Cofactors and Coenzymes
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Inorganic substances (zinc, iron) and
vitamins (respectively) are sometimes
needed for proper enzymatic activity.
Example:
Iron must be present in the quaternary
structure - hemoglobin in order for it to
pick up oxygen.
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Two examples of Enzyme
Inhibitors
a. Competitive inhibitors: are
chemicals that resemble an
enzyme’s normal substrate and
compete with it for the active
site.
Substrate
Competitive inhibitor
Enzyme
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Inhibitors
b.
Noncompetitive inhibitors:
Inhibitors that do not enter the
active site, but bind to another part
of the enzyme causing the enzyme to
change its shape, which in turn
alters the active site.
Substrate
active site
altered
Enzyme
Noncompetitive
Inhibitor
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