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Biology Lecture Notes-Chapter 2

by: Adriana Proctor

Biology Lecture Notes-Chapter 2 BIO-101-105

Marketplace > Chesapeake College > Science > BIO-101-105 > Biology Lecture Notes Chapter 2
Adriana Proctor
Chesapeake College
GPA 4.0

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About this Document

These notes are written the second week of class and are taken for every chapter provided by the Professor. These notes include topics such as: -States of Matter -Elements and Compounds -Atoms ...
Fundamentals of Biology I
Doctor Hatkoff
Class Notes
Biology, structure of atoms, atoms and elements, Periodic Properties of Elements, periodic table
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This 11 page Class Notes was uploaded by Adriana Proctor on Monday August 29, 2016. The Class Notes belongs to BIO-101-105 at Chesapeake College taught by Doctor Hatkoff in Fall 2016. Since its upload, it has received 20 views. For similar materials see Fundamentals of Biology I in Science at Chesapeake College.


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Date Created: 08/29/16
*Biology Lecture Notes  Chapter 2  EXPLAIN ON BOTTOM    A Chemical Connection to Biology  There is a purpose of the chemistry that we know that links to the study of life.  Many organisms and their  environments  are natural systems in which the impression of both chemistry and physics are applied to.  The lowest level of this biological organism is the atoms that embody the molecules of the cell.    Matter consists of chemical elements in pure form and in  combinations called compounds    Matter­​What organisms are composed of, which is anything that has mass and takes up space.    Elements and Compounds    Element­​Substance that cannot be broken down to other substances by chemical reactions.  Compound­​A substance that consists of two or more different elements combined in a fixed ratio(table  salt, NaCl).    *Refer to an original Periodic Table for  elemental names as well as numbers that  are at a better visibility.    20­25% of the natural elements are essential elements that an organism needs to live a healthy productive  life.  Four of the elements make up around 96% of living matter:  ● Oxygen(O)  ● Carbon(C)  ● Hydrogen(H)  ● Nitrogen(N)  Other elements make up the other 4% , and are known as trace elements(Calcium[Ca]).  Evolution of Tolerance to Toxic Elements    ● Some ​naturally occurring elements are toxic to organisms.  ● Some species have become adapted to environments  containing elements that are usually toxic.  ­Sunflower plants can take up lead, zinc, and other heavy metals ​in concentrations lethal to most  organisms.  ­Sunflower plants were used to detoxify contaminated soils after Hurricane Katrina!  An element’s properties depend on the structure of its atoms Atom­​ The smallest unit of matter that still retains the properties of an element.  Subatomic Particles  ​ Subatomic particles are composed of smaller parts of an atom, otherwise known as neutrons, which have  an electrically neutral charge.  Protons have a positive charge(pro) and electrons have a negative  charge(eleCtrON=con).      Neutrons and protons are found in the atomic nucleus, whereas the electrons are found in a cloud around  the atomic nucleus.  The unit of measurements for an atom and its subatomic particles is the dalton, which  is based on the “weight” of neutrons and protons.                                    Atomic Number and Atomic Mass  An atomic number represents the number of protons, which is important to that element.  The mass  number and atomic mass is the sum of the number of protons/neutrons in the atomic nucleus.                                              Bohr Model  An early model  of atomic  structure in which electrons travel around the nucleus in a number of discrete stable orbits determined by  quantum conditions.                          Isotopes  ● Some atoms have more neutrons than others atoms of the same element, and as a result have a  greater mass.  The different atomic forms of the same element is called an isotope.  ● A radioactive isotope is one where the nucleus decays, which randomly gives off particles and  energy.  ● Cells use the radioisotope as they would the non­radioactive isotope, thus a diagnosis can be  made.  ● Radiometric Dating is used to study evolution.  The half­life of a radioactive isotope is measured  to determine the age of a fossil.    Some applications of radioactive isotopes in biological research are  ● Dating fossils  ● Tracing atoms through metabolic processes  ● Diagnosing medical disorders  The energy level of electrons  Only electrons are directly involved in chemical reactions between atoms.  An atom’s electrons vary in  the amount of energy they contain.    Energy is defined as the capacity to do work.  The more distant an electron is from the nucleus, the  greater its potential energy.  Electrons are found in different electron shells.  Electron Distribution and Chemical Properties  ● The chemical behavior of an atom can be determined by the distribution of electrons in the atom’s  electron shells.  You can “build” atoms by adding one proton and electron at a time.  ● Such chemical behavior of an atom is decided mostly on the number of electrons in the outermost  shell.  ● The outermost electrons are the valence electrons, and the outermost electron shell is the valence  shell.  ● Certain atoms are chemically reactive because they have incomplete valence shells.  Electron Orbitals  An orbital is where a three dimensional space where an electron is found 90% of the time.  The reactivity  of an atom arises from the presence of unpaired electrons in their valence shells.     The Formation and Function of Molecules depend on Chemical  Bonding between Atoms    ● Atoms combine to form molecules and compounds.   ● Atoms with incomplete valence shells interact such that each of their valence shells becomes  complete.  This interaction creates chemical bonds.  Covalent bonds  A covalent bond is sharing a pair of valence electrons by two atoms.  Two or more atoms held together by  covalent bonds constitute a molecule.    A compound is a combination of two or more different elements.  The attraction of a certain atom for the  electrons of a covalent bond is known as its electronegativity.  The more electronegative the atom is, the  stronger it pulls shared electrons towards itself.  For different atoms that have similar electronegativities,  they will share the electrons equally and form a nonpolar covalent bond.    When one atom has a stronger electronegativity than the other, the electrons seem to lean towards the  more electronegative atom, which is called polar covalent bond.  I know it seems confusing now, but as  you reread this and continue on, it will begin to make sense.             ​             Molecular Shape and Function    ● A molecule has a precise size and shape, and the shape of that molecule is very important to its  function in the living cell.  ● Molecular shape is crucial in biology since it determines how biological molecules recognize and  respond to one another with specificity.     Chemical Reactions make and Break Chemical Bonds    ● Chemical reactions are the making and breaking of chemical bonds.   ● Starting materials used is called the reactants and they are converted to products.  ● One of the factors affecting the reaction rate is the concentration of the reactants.  ● Chemical reactions can reach chemical equilibrium, where the reactants and products  concentrations have stabilized at a specific ratio.                                     Properties of Water  The four emergent properties of water that contribute to Earth’s sustainability for life include:  ● Cohesion  ● Moderation of temperature by water  ● Floating of ice on liquid water  ● Water as a solvent  Cohesion of Water Molecules  ● Water molecules are linked by multiple hydrogen bonds  ● The molecules stay close together because of cohesion.  ● Cohesion, due to the bonding of hydrogen, contributes to the transport of water and nutrients  against gravity in plants.  ● Adhesion is the clinging of one substance to another.    Moderation of Temperature by Water  ● Water absorbs heat from warmer air and releases stored heat to cooler air  ● Water can absorb or release a large amount of heat with only a slight change in its own  temperature.      Floating of Ice on Liquid Water  ● Ice melts in liquid water because hydrogen bonds in ice are more dense, making ice less of a  liquid.  ● If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth.        The Chemistry of Life is Sensitive to Acidic and Basic Conditions  In liquid water, a small percentage of water molecules break apart into ions.  ● Some are hydrogen ions(H+).  ● Some are Hydroxide ions(OH­).  ● Both types are very reactive.  The lower the pH, the more A ​ CIDIC.  Acid­​Increases the H+ concentration.  Base­​Reduces the H+ concentration.  The higher the pH, the more BASIC.                                    The pH scale is a log scale  ● A solution with a pH 3 has 1 times more H+ ions than a solution with a pH 4.  ● A solution with a pH 12 has ten times less H+ ions than a solution with a pH 2.  Buffers  Buffers are substances that minimize changes in concentrations of H+ and OH­ in a solution.  The internal  pH of most living cells must remain close to pH 7.2.  Acidification:A Threat to Our Oceans  ● Human activities such as burning fossil fuels threaten water quality.  ● CO2 is a product of fossil fuel combustion.  ● About 25% of human­generated CO2 is absorbed by the oceans  ● CO2 dissolved in seawater forms carbonic acid; this causes ocean acidification.  ● As seawater acidifies, hydrogen ions combine with carbonate ions to form bicarbonate  ions(HCO3­)  ● It is predicted that carbonate ion concentrations will decline by 40% by the year 2100.  ● This is a concern because organisms that build coral reefs or shells require carbonate ions.            *These lecture notes are to be used as notes only, and some information may or may not be  presented in the exams.  It is best to ask professors for a list of what will be in each exam. 


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