Transcript Chemical Reactions

 Matter and Energy
 Matter: anything that occupies
space and has mass
 Energy: The capacity to do
•
work
Two types of energy
–
Potential energy (PE):
• stored energy
• ball on top of hill about to roll
down
–
Kinetic energy (KE):
• energy of motion
• Ball rolling down hill
Elements: the simplest type of matter with unique
chemical properties; composed of atoms of only one kind
 118 total (92 natural)
 Twenty-five elements are essential to life
 Four of these make up about 96% of the weight of the
human body
–
–
–
–
–
C (18.5%)
O (65%)
H (9.5%)
N (3.3%)
Remaining 4% elements are
• (Ca, P, K, S, Na ,Cl, Mg)
• Trace elements occur in
smaller amounts (less than 0.01%)
Atoms: Indivisible, smallest particle of an element that
has chemical characteristics of that element
 Composed of subatomic particles:
 Protons (p)
– Subatomic particles that carry positive charges
– Found in the atom’s nucleus
 Neutrons (n)
– Carry NO charges
– Found in atom’s nucleus
 Electrons (e)
– Carry negative charges
– Orbit around the nucleus
– Atoms are neutrally charged:
# electrons = # protons
• Atomic number
= # of protons in nucleus of the atom
• Mass number
= # of protons + # of neutrons
• Most of atom’s mass is in the nucleus
• Electrons virtually weigh nothing!
• What is the mass number of Uranium??
– (92 protons, 143 neutrons)
– Answer = 235
• Isotopes:
 Atoms with the same # of protons but different # of
neutrons
 Atoms with the same atomic number but different
mass numbers
• What determines whether an atom will interact with others?
– The number & arrangement of electrons in outermost (valence) shell
– Atoms whose outer shell are not full tend to interact
– Electrons move around in orbitals
– First orbital holds 2 e’, Second orbital holds 8 e’
– Unfilled outer shell = READY TO BOND!!!, Very reactive
– Helium – First shell is full with 2 electrons – chemically unreactive
– Atoms whose outer shells are not full share
or transfer electrons to other atoms, forming
compounds by chemical bonding
– Two major types of chemical bonds between
atoms form compounds
• Ionic bonds
• Covalent bonds
• Ionic Bonds: When atoms bond by losing/gaining electrons
– When an atom loses or gains electrons, it becomes
electrically charged
• Charged atoms are called ions
• Cation: positively charged ion
• Anion: negatively charged ion
• Ionic bonds are formed between oppositely charged
ions
• Covalent Bonds: When atoms bond by sharing
electrons
• Atoms held together by covalent bond form a molecule
• Eg. Hydrogen gas, oxygen gas, methane etc.
• Single covalent: two atoms share one pair of electrons
• Double covalent: Two atoms share 4 electrons
Nonpolar covalent:
When electrons are
shared equally because
nuclei attract the electrons
equally. Eg. CO2
Polar covalent:
Electrons not shared
equally because one
nucleus attracts the
electrons more than the
other does. Eg. water
 Hydrogen bond forms between polar covalent
bond, weak bond
 Polar covalent molecules have positive &
negative ends. Eg. Water
 Hydrogen bond forms when the positively
charged H of one molecule is attracted to the
highly negatively charged O, N or F of another
molecule
– For eg, in water the positively charged
hydrogen atoms of one water molecule
form hydrogen bond with the negatively
charged oxygen atoms of other water
molecules
– Hydrogen bonds play an important role in
determining the shape of complex
molecules
– Eg. Water, DNA, RNA, Protein
 Molecules: two or more like atoms combined
chemically
– Eg. hydrogen molecule (H2)
 Compounds: two or more different atoms combined
chemically
– Eg. Sodium chloride (NaCl)
Chemical Reactions – Change
in the chemical composition of
matter
Chemical reactions include:
Reactants: substances that
enter into a chemical reaction
Products: substances that
result from the reaction
Chemical reactions cannot
create or destroy matter
 They only rearrange it
 During chemical reactions chemical
bonds are formed (synthesis reaction)
and broken (decomposition reaction)
 Two or more reactants chemically combine to form a
new and larger product – Synthesis Reaction
A+BC
– Water is removed: Dehydration
– Produce chemicals characteristic of life: carbohydrates, proteins,
lipids, nucleic acids, ATP.
– All of Synthesis reactions occur within body – Anabolism
– Anabolic reactions - Responsible for growth, maintenance and
repair
 A large reactant is broken down to form smaller products
– Decomposition Reaction
AB  A + B
– Water is added – Hydrolysis
– All of decomposition reactions occur within body – Catabolism
– Includes digestion of food molecules, breakdown of fat store
etc.
– All of the catabolic and anabolic reactions - Metabolism
 All chemicals found in the body are classified
into two types of molecules
 Inorganic Compound: Generally, substances that
do not contain carbon
– Eg. Water, salts, acids and bases
– Exceptions: CO, CO2, and HCO3 Organic Compound: Are carbon-containing
substances
 Water
– Water is basis of life
– Accounts for about 2/3 of
body weight
– Composed of one atom of O
and two atoms of H
– Water molecules are polar
– H bonds between the water
molecules hold the water
molecule together
• High heat capacity: large amount of heat required to
raise temperature of water, resist large temp. fluctuations
– Stabilizes body temperature
• Cushioning
– Serves as a protective function
– Lubricant, eg. tears
– fluid cushion around the organs eg. Cerebrospinal fluid
surround the brain
• Chemical Reactivity
– Many reactions take place in water
– Dehydration and hydrolysis
 Polarity/Solvent properties
 Water is an excellent solvent
– Solvent: that which dissolves the solute, eg. water
– Solute: that which dissolves in the solvent, eg. Salt
 Solution: mixture of liquids, gasses, or solids that are
uniformly distributed and chemically combined
 Mixture: substances physically blended but not
chemically combined
– Suspension: materials separate unless stirred. Eg.
Sand and water, Blood and plasma
– Colloid: dispersal of tiny particles through a medium.
Eg. Milk
• Salts
– Easily dissociate into ions
in the presence of water
– When ionic compds
dissolve in water –
dissociate
– Vital to many body
functions
– eg. Sodium and potassium
ions – essential for nerve
impulse
– All salts are electrolytes
which conduct electrical
currents
Acids and Bases
 Acid: a proton donor or any substance that releases
hydrogen ions
HCl  H+ + Cl
 Base: a proton acceptor or any substance that binds
to or accepts hydrogen ions and release hydroxide
ions (OH-)
NaOH  Na+ + OH• Neutralization reaction
– Acids and bases react to form water and a salt
HCl + NaOH  H2O + NaCl
• Refers to the Hydrogen ion
(H+) concentration in a
solution
– Neutral: pH of 7 or equal
hydrogen and hydroxide
ions
– Acidic: a greater
concentration of hydrogen
ions
– Alkaline or basic: a greater
concentration of hydroxide
ions
– Physiologic pH is 7.4
– Buffers: chemicals that can
regulate pH change
• Four major groups of Organic compounds
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
• Carbohydrates: Include sugars and starches
• composed of carbon, hydrogen, oxygen
• Molecular formula – CH2O
• Eg. Glucose – C6H12O6
- Monosaccharides
- Disaccharides
- Polysaccharides
 Single sugars Glucose is found in sports drinks, found
in blood (blood sugar)
 Fructose is found in fruit
 Very important in the diet as energy sources
 Sugars like ribose and deoxyribose are components of
ATP, DNA and RNA
Two simple sugars bound together by dehydration
 Eg: sucrose or table sugar ( glucose + fructose)
Lactose or milk sugar (glucose + galactose)
Maltose or malt sugar ( glucose + glucose)
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Polysaccharides: long-branching chains of linked
simple sugars
Some polysaccharides are energy storage molecules
– Starch in plants
– Glycogen in animals
•
Cellulose – Polysaccharide found in plants
- Important structural component of cell wall
• Lipids enter the body in the form of egg yolks,
milk products, oil
• Consist mostly of hydrocarbons, lower ratio of
oxygen and phosphorous and N in some lipids
• Do not mix with water
• Eg. Fats, phospholipids, steroids
• Fats are major type of lipid
• Functions: protection, insulation, energy source
• Dietary fat consists largely of the molecule triglyceride,
constitute 95% of fat
• Triglyceride is a combination of glycerol and three fatty acids
• Formed by dehydration reactions
• Fatty acids may be saturated or unsaturated
– Saturated Fatty acid – contains all single bonds in the
carbon chain, which produces a more rigid structure
– eg. butter
– Unsaturated Fatty acid – contains one (mono) or more
(poly) double bonds in the carbon chain, which produces
a more relaxed structure
– eg. Olive oil, corn oil, sunflower oil
• Better because they do not stick to the inside of blood
vessels.
Phospholipids
– Contain only two fatty acid
groups attached to glycerol
– Have a phosphate group instead
of a third fatty acid attached to
glycerol
Polar (hydrophilic) at one
end; nonpolar (hydrophobic)
at the other
 Important structural
component of cell
membranes
Steroids are very different from fats in structure
and function.
• The carbon atoms bound together into four ringlike structures
– Cholesterol is the “base steroid” from which our body
produces other steroids.
• For eg. bile salts, reproductive hormones estrogen,
testosterone
 Important component of cell membrane
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•
Account for over 50% of organic matter in the body
Functions
– Structural: hair, cell cytoskeleton
– Contraction: Actin and myosin in muscle are
responsible for muscle contraction
– Storage: sources of amino acids, such as egg white
– Defense: antibodies, membrane proteins
– Transport: carriers of molecules such as
hemoglobin, membrane proteins
– Signaling: hormones, membrane proteins
– Enzymes: regulators of the speed biochemical
reactions
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Basic building blocks for proteins are 20 amino acid
molecules
Each amino acid contains
– An amino group
– A carboxyl group
– A hydrogen atom
– One of twenty side ("R") chains
•
The three groups and a hydrogen atom are bonded to
a central "alpha" carbon
 Covalent bonds formed between amino acids
during protein synthesis – peptide bond
 Dipeptides are two amino acids long
 Polypeptides are from several to more than a thousand
amino acids long
• Based on the shape and
structure, proteins are
classified as
• Fibrous Protein
• Globular Protein
• Fibrous proteins
– Also known as structural
proteins
– Appear in body structures
– Eg. collagen – found in
bones, cartilage, tendons
– Keratin – hair, nails
– Highly Stable
• Globular proteins
– Also known as
functional proteins
– Function as
antibodies or
enzymes
– Can be denatured
– with change in
temp., pH
• An enzyme is a protein catalyst
• increases the rate of chemical
reaction
• Three-dimensional shape
contains an active site where
reactants attach
 There are two types of nucleic acids:
• DNA, deoxyribonucleic acid
• RNA, ribonucleic acid
DNA – DNA is a genetic material of cells
Copies of DNA are transferred from one
generation of cells to next
DNA determines the structure of protein
Composed of 2 strands of nucleotides
 Each nucleotide is composed of a five-carbon
sugar (deoxyribose), a nitrogenous base, and a
phosphate
– Each DNA nucleotide has one of the following
nitrogenous bases:
•
•
•
•
Adenine (A)
Guanine (G)
Thymine (T)
Cytosine (C)
– Purines - A & G
– Contains double C ring
– Pyrimidines - T & C
– Contains single C ring
– DNA is a double helix
• Two strands of
polynucleotides are
twisted around each
other, forms ladder like
structure – Double Helix
• Uprights of ladder are
formed of sugar and
phosphates
• Rungs of ladder –
nitrogenous base
• Nitrogenous base
connected to other base
by H bond
• Complementary base pairing rule:
• Adenine pairs with thymine
• Cytosine pairs guanine
• Two strands of DNA are said
to Complementary
• If base sequence of one strand
is known – other can be predicted
because of base pairing rule
• Sequence of base determines Protein
structure
• DNA defines all cellular activities
– RNA, ribonucleic acid, is different from DNA.
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Its sugar (ribose) has an extra OH group.
It has the base uracil (U) instead of thymine (T).
Single strand polynucleotide
Responsible for interpreting the code within DNA into
the primary structure of proteins
• Energy currency of the body
• Consists of adenine, ribose and 3 phosphate
groups
• Provides energy for other chemical reactions
• All energy-requiring chemical reactions stop
when there is inadequate ATP