BIOL 109 Lecture Notes - Lecture 4: Chemical Polarity, Hydrogen Atom, Atomic Nucleus

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9 Dec 2016
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2.1
Matter- anything that takes up space and has mass
Mass- amount of materials in matter
Atoms- smallest stable units of matter
Normally contain equal protons and electrons
Subatomic particles
Protons (p+)- positive charge
Neutrons (n) neutral
Electrons (e-) negative
nucleus - the central region of an atom
Atomic number- number of protons in an atom
Electron cloud- sphere electrons travel around the nucleus
Electron shell-outside part of an atom around the atomic nucleus
Element- pure substance composed of one type of atom
92 natural elements, 24 created in nuclear reactions
Atomic nuclei are unaltered by ordinary chemical processes
Principle elements in the human body
Oxygen (65%)
Carbon (18.6%)
Hydrogen (9.7%)
Nitrogen (3.2%)
Calcium (1.8%)
Phosphorus (1%)
Potassium (0.4%)
Sodium (0.2%)
Chlorine (0.2%)
Magnesium (0.06%)
Sulfur (0.04%)
Iron (0.007%)
Iodine (0.0002%)
Isotopes- atoms of the same element whose nuclei contain different numbers of
neutrons
Have essentially identical chemical properties and are alike but in mass
Mass number- total number of neutrons and protons in the nucleus
Used to designate isotopes
Radioisotopes- spontaneous breakdown and give off subatomic particles or
radiation in measurable amounts
Process called radioactive decay
Half-life the time required for half of a given amount of the isotope
to decay
Atomic weight- average of different atomic masses
mole - specific quantity with weight in grams equal to that element's atomic weight
Valence shell- outermost energy level in the electron cloud
2.2
Inert- elements that do not readily participate in chemical processes
Reactive- elements that readily combine with other atoms
Chemical bonds
Molecule- atoms that shares an electron
Compound- made up of two or more elements
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The Chemical Level of Organization
Molecular weight- sum of atomic weights of the atoms that make up the
molecule or compound
Ionic bonds- chemical bonds created by electrical attraction between anions and
cations
Ion- atom or group of atoms that have an electric charge
Cations- ions with positive charge
Charge of +1 or more
Anions- ions with negative charge
Charge of -1 or less
Formation of an ion
1. Electron donor loses one or more electrons
and becomes a cation
2. The electron acceptor gains the electrons
and becomes an anion
3. Attraction between the opposite charges
draws the two together
Covalent Bonds- sharing electrons with other atoms
Single covalent bond- sharing one pair of electrons
Double covalent bond- shares two pairs of electrons
Nonpolar covalent bonds- equal sharing of electrons of two of the same
type of atom
Polar covalent bonds- involving different types of atoms; share electrons
unequally
Often create polar molecules water is the most important one
Weaker than nonpolar bonds
Hydrogen Bonds- attraction between a slight positive charge on a hydrogen
atom of a polar covalent bond and slight negative charge on an oxygen, nitrogen,
or fluorine atom of a polar covalent bond .
Solid- keep volume and shape at ordinary temperatures and pressures
Liquid- constant volume but no fixed shape
Gas- no constant volume or fixed shape
2.3
Chemical reaction- new chemical bond Forms between atoms or existing bonds
between atoms are broken down
Reactants- reacting substance
Products- different substance
Metabolism- reactions underway in the cells and tissues of the body at any given
moment
Work- movement of an object or a change in the physical structure of matter
Energy- capacity to do work
kinetic energy- the energy of motion
Potential energy- stored energy
Energy cannot be destroyed it can only be transformed into one form or another
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The Chemical Level of Organization
Conversion between energy is never a hundred percent efficient. Each
time the energy exchange occurs some energy is released in the form of
heat.
Types of chemical reactions
Decomposition reactions- Breaks down a molecule into smaller
fragments
AB=a + b
Hydrolysis- one of the bonds in a complex molecule is broken
and the components of the water molecules are added to the
resulting fragments
A-B+H2O=A-H+HO-B
Catabolism- the decomposition reactions of complex molecules
within the body cells and tissues
Covalent bond is a form of potential energy
When covalent bonds are broken down it releases kinetic
energy that can do work
Synthesis reaction- opposite of decomposition. Assembles smaller
molecules into larger molecules.
A+B=AB
Synthesis always involved in the formation of new
chemical bonds whether it's reactants or atoms or
molecules
Dehydration synthesis- formation of a complex molecule by the
removal of a water molecule. Opposite of hydrolysis
A-H+HO-B=A-B+H2O
Anabolism synthesis- of new molecules within the body cells
and tissues
Takes energy to create chemical bond
Exchange reactions- molecules are shuffled around to produce new
products
AB+CD=AC+BD
Reversible reaction- in theory all chemical reactions are reversible
If a+b=ab then ab=a=b
2.4
Activation energy- amount of energy required to start a reaction
Enzymes- promote chemical reactions by lowering activation energy required
Enzymes perform most of the complex synthesis and decomposition reactions in
your body
Can only affect rate of reaction
Metabolic pathway- complex reactions that support life take place in
series of interlocking steps
Separate enzymes are often involved
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