Transcript 2 Carboxyl Groups

LG 3 Presentation Outline
Molecules of Cells
Carbon
3 Carbon Bonding
Functional Groups in
BiologicalMolecules
2 Hydroxyl Groups –
2 Carbonyl Groups –
2 Carboxyl Groups –
2 Amino Groups –
3 Phosphate Groups –
2 Sulfhydryl Groups –
Biological Molecules
14 Carbohydrates –
10 Lipids –
10 Nucleotides
Proteins
5 Amino Acids –
Levels of Structure
2 Primary Structure –
2 Secondary Structure –
2 Tertiary Structure –
2 Quaternary Structure –
Role of Enzymes
6 Enzymes –
Enzyme Activity
4 Activation Energy –
4 Enzyme Specificity –
2 Cofactors –
2 Coenzymes –
5 Transition State –
6 Factors Affecting Enzyme Activity –
Effect of Enzyme Inhibitors
2 Competitive Inhibition –
2 Noncompetitive Inhibition –
4 Allosteric Regulation –
Unit IV
Learning Goal 3
Analyze the molecules that
make up cells.
Carbon
Carbon Bonding
Carbon atoms form 4
covalent bonds to fill their
outer electron shells.
This allows them to form
a variety of chain and ring
structures that form the
backbone of all biological
molecules.
• These are known as
organic molecules.
• Molecules consisting of
carbon and hydrogen are
called hydrocarbons.
Functional Groups in Biological
Molecules
• Hydroxyl Groups
Consist of an oxygen
atom linked to a
hydrogen (--OH).
They give the
molecule they are
attached to a polar
nature.
Key component of
alcohols.
• Carbonyl Groups
A carbon atom linked
to an oxygen atom by
a double bond (C=O).
Important molecules
for cellular energy.
• Carboxyl Groups
A combination of a
carbonyl group and a
hydroxyl group.
(--COOH).
Characteristic functional
group of organic acids
because it releases
hydrogen in water
solutions.
Examples are citric and
acetic acid.
• Amino Groups
Contain a nitrogen
atom bonded to two
hydrogen atoms
(--NH2).
Functional group of
amino acids which
are the building
blocks of proteins.
• Phosphate Groups
Consists of a central
phosphorus bound to
oxygen atoms and
hydroxyl groups
(--OPO32-).
Form chemical bridges
between organic
molecules.
Added or removed to
release energy.
Control chemical activity
of many proteins.
• Sulfhydryl Groups
A sulfur atom is linked on
one side to a hydrogen
atom and on the other to
a carbon chain (-SH).
Act a molecular fastener
holding protein molecules
in their folded form or
linking protein subunits
into larger structures.
Biological Molecules
Carbohydrates
Monosaccharides
Smallest carbohydrate
molecules.
Consist of 3, 5, or 6
carbon atoms bonded to
hydrogen.
Can be linear or ring
forms.
Many exist as isomers,
meaning same chemical
formula but different
molecular structures
causing them to react
differently.
• Disaccharides
Consist of two
monosaccharides linked
together by a
dehydration synthesis
reaction.
Sucrose (fructose +
glucose) is the sugar
transported in plants and
crystalized to form table
suger.
Lactose
(glucose+galactose) is
sugar found in milk.
• Polysaccharides
Long chains of
monosaccharides
linked to form
macromolecules.
Result from the
polymerization of
monosaccharide
monomers into larger
polymers.
• Plant Starches
Storage form of
carbohydrates in
plants.
Long chains of
glucose molecules
that are digestible by
humans.
• Glycogen
Storage form of
carbohydrates in
animal livers.
Highly branched
chains of glucose
molecules.
• Cellulose
Most abundant
carbohydrate in nature.
Primary structure of plant
cell walls .
Can be digested by
herbivores, but not by
humans.
Still important fiber for
healthy digestive
functions.
• Chitin
Tough carbohydrate
chains with nitrogencontaining groups.
Main component of
the shells of
arthropods such as
insects and crabs.
Also cell walls of fungi
such as mushrooms.
Lipids
• Neutral Lipids
Lipids are a group of
water-insoluble, nonpolar
molecules made up
mostly of hydrocarbons.
Neutral lipids have no
charged groups at cellular
pH.
Consist of fats, oils, and
waxes made from a
glycerol backbone and 3
fatty acid side chains.
• Fatty Acids
Single hydrocarbon
chains with a carboxyl
group at one end.
If it contains the
maximum number of
hydrogen atoms is
considered saturated.
Main component of fats
which are semisolid.
If one or more double
bonds link the carbon
atoms it is considered
unsaturated.
These are the main
component of oils which
are liquid a biological
temperatures.
Unsaturated lipids are
considered healthier in
the human diet than
saturated.
• Phospholipids
Formed from a glycerol
backbone attached to two
fatty acid side chains and
a polar phosphate group.
In a polar environment
(such as water)
phospholipids assume
arrangements in which
only their polar ends are
exposed to water.
This is the reason cell
membranes form a lipid
bilayer.
• Steroids
Group of lipids with
structures based on four
carbon rings.
Most abundant are the
sterols which have a
single –OH group linked
to one end of the ring
framework and a
complex, nonpolar
hydrocarbon chain at the
other end.
Nucleotides and Nucleic Acids
• Nucleotides
A nucleotide consists of
three parts linked
together by covalent
bonds:
1. a nitrogenous base
(either a purine or a
pyrimidine)
2. a five-carbon, ringshaped sugar (either
ribose or deoxyribose)
3. one to three phosphate
groups
• Nucleotide Functions
Important molecules such
as ATP (adenosine
triphosphate) and GTP
(guanosine triphosphate)
are the primary molecules
that transport chemical
energy in cells.
Nucleotides are the
building blocks (subunits)
of nucleic acids.
• Nucleic Acids
DNA (deoxyribose nucleic
acid)
Consists of two nucleotide
chains wrapped around each
other to form a double helix.
Sugar (deoxyribose) and
phosphate molecules make up
the backbone and pairs of
nitrogen bases make up the
center.
Nitrogen bases come in four
varieties: adenine, guanine,
cytosine, and thymine.
• RNA (ribonucleic acid)
Single stranded chain of
nucleotides bound
together by sugar (ribose)
and phosphate bonds.
Nitrogen bases are the
same as DNA except
uracil replaces thymine.
Proteins
• Amino Acids
Cells use 20 different
amino acids to build
proteins.
Amino acids consist of a
central carbon atom
attached to an amino
group, a carboxyl group,
and a hydrogen atom.
The remaining bond of
the central carbon is
linked to different side
groups.
Amino acids are linked
into protein molecules by
peptide bonds.
These are formed by a
dehydration synthesis
reaction between the –
NH2 group of one amino
acid and the –COOH
group of a second.
A chain of amino acids
formed this way is called
a polypeptide.
Levels of Structure
• Primary Structure
The sequence of amino
acids makes up a
proteins primary
structure.
One amino acid out of
place can alter the entire
structure and function of
a protein such as in the
disease sickle-cell
anemia.
• Secondary Structure
The folding of an
amino acid chain into
various
arrangements.
They are alpha helix,
beta strands, and
random coils.
• Tertiary Structure
The content of alphahelical, beta-strand, and
random-coil segments,
together with the number
and position of disulfide
linkages and hydrogen
bonds, folds each protein
into its tertiary structure.
This is its overall threedimensional shape.
• Quaternary
Structure
When two or more
amino acid chains
combine to form a
protein it is known as
quaternary structure.
Role of Enzymes
Enzymes
Proteins that increase
the speed of reactions
millions to trillions of
times.
Many reactions would
proceed too slowly at
cellular temperature.
Enzymes have names
ending in –ase.
Example: Enzymes
that break down
proteins are called
proteinases or
proteases.
Substances with the
ability to accelerate
spontaneous
reactions without
being changed by the
reactions are called
catalysts.
Enzyme Activity
• Activation Energy
Enzymes accelerate
reactions by reducing
the activation energy
of a reaction.
This is the initial input
of energy required to
start a reaction.
Reactions that take
place in biological
systems would
normally require a
large input of heat.
Enzyme Specificity
• Each type of enzyme
catalyzes the reaction
of only a single type
of molecule or group
of closely related
molecules. This
characteristic is
known as enzyme
specificity.
The reacting molecule
is known as the
substrate.
The region of an
enzyme that
recognizes and
combines with a
substrate molecule is
the active site.
Cofactors
Many enzymes include a
cofactor, an inorganic or
organic nonprotein group
that is necessary for
catalysis to take place.
Many are inorganic ions
like iron, copper,
magnesium, zinc, and
potassium.
Coenzymes
Organic cofactors,
also called
coenzymes, are
complex chemical
groups of various
kinds. Many are
derived from vitamins.
Transition State
Enzymes reduce
activation energy by
forming an enzymesubstrate complex
know as the
transition state.
Three mechanisms
contribute to the
formation of the
transition state:
• Bringing the reacting molecules into close
proximity.
• Orienting the reactants in positions that
favor the transition state.
• Exposing the reactant molecules to altered
environments that promote their
interaction.
Factors Affecting Enzyme Activity
• Temperature and pH
Enzymes typically
operate best in the range
of about 0-40 degrees
Celsius.
Above 40 degrees, the
increasing kinetic motion
begins to unfold the
enzyme, reducing the
rate of enzyme activity.
Most enzymes have a
pH optimum near the
pH of the cellular
contents, about pH 7.
Exceptions are
enzymes of the
digestive tract such
as pepsin.
• Substrate
Concentration
At very low
concentrations, substrate
molecules and enzyme
collide less often.
As substrate
concentration increases
so does reaction rate to a
point called saturation.
Effect of Enzyme Inhibitors
Competitive Inhibition
Enzyme inhibitors are
substances that reduce
enzyme activity by
combining with enzyme
molecules.
Inhibitors that combine
with the active site
compete with the
substrate. This is called
competitive inhibition.
Noncompetitive Inhibition
Inhibitors that combine
with enzymes at locations
other than the active site
often alter the
conformation of the
enzyme.
Because they don’t
compete directly with the
substrate this is called
noncompetitive
inhibition.
Allosteric Regulation
Occurs by the reversible
combination of a
regulatory molecule with
the allosteric site, a
location on the enzyme
outside of the active site.
Frequently allosteric
inhibitors are a
product of the
metabolic pathway
that they regulate.
This is called
feedback inhibition
because as the
product builds up it
inhibits the activity of
the enzyme.
LG 3 and 4 Terms
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Organic
Carbohydrate
Lipid
Nucleic Acid
Protein
Enzyme
Activation Energy
Feedback Inhibition
Allosteric Site
Competitive vs
Noncompetitive
Inhibition
1. Oxidative
Phosphorylation
2. Glycolysis
3. Citric Acid Cycle
4. Electron Transfer
System
5. Fermentation
6. CO2 Fixation
7. Chloroplast Structure
8. Photosystems
9. Calvin Cycle
10. C4 Cycle