Biology Lecture Notes-Chapter 2
Biology Lecture Notes-Chapter 2 BIO-101-105
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Adriana Shania Proctor
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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 MatterWhat organisms are composed of, which is anything that has mass and takes up space. Elements and Compounds ElementSubstance that cannot be broken down to other substances by chemical reactions. CompoundA 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. AcidIncreases the H+ concentration. BaseReduces 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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