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Biology 101

by: Alondra Notetaker

Biology 101 101

Alondra Notetaker

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About this Document

These notes cover the second chapter of the Biology book focused on the chemistry of biology
General Biology
Class Notes
Biology, Chemistry, general
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This 5 page Class Notes was uploaded by Alondra Notetaker on Sunday September 18, 2016. The Class Notes belongs to 101 at Loyola University Chicago taught by Castignetti in Fall 2016. Since its upload, it has received 3 views. For similar materials see General Biology in Science at Loyola University Chicago.


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Date Created: 09/18/16
WhystudychemistryifweaimtolearnBiology? ● Chemistry is essential to learning the basics of Biology ○ Learn how biomolecules work ○ Explains fermentation, respiration and photosynthesis E​ ample:Ants use a substance called formic acid that comes from their abdomens and they shoot this when they feel threatened this can also be an evolutionary advantage. ElementsandCompounds: ● As stated before, organisms are composed of ​matter ​= anything that takes up space and has mass ● Matter is made up of elements ○ Elements:​substances that cannot be broken down to other substances by chemical reactions ■ Examples: Oxygen, Hydrogen, Nitrogen etc ○ Compound:​ ​is a substance that consists of two or more different elements in a fixed ratio ■ Example: Sodium Chloride(NaCl) also known as table salt ● There are 92 natural elements, Oxygen, Carbon, Nitrogen and Hydrogen make up 96% of living matter ○ Essentialelements:​​20-25% are essential for an organism to live a healthy life ○ Traceelements:​ required by organisms in only small quantities ■ Calcium, Phosphorus, Potassium and Sulfur ● Some trace elements are needed by all living things and others are only needed for specific organisms *There are some species that have evolved to be able to live in high exposure to trace elements that other species cannot survive in, an example of this is the Serpentine plant ● Each element consists of a certain type of atom ○ Atom:​​smallest unit of matter that still retains properties of an element ■ Atoms are mostly empty space ● Subatomic​ particles are are even smaller parts of an atom that are created by colliding atoms together ● Three main types are electrons, neutrons and protons ○ Protons:​ particles with a positive charge ○ Neutrons:​ particles with a neutral charge ○ Electrons: ​particles with a negative charge ● Protons and neutrons are packed tightly in the atomic nucleus which is at the center of the atom ○ Protons give the nucleus a positive charge while electrons form a cloud around giving it a negative charge (opposites attract) ○ Unit of measurement =​ Dalton ○ Electrons are directly involved in chemical reactions ○ Dalton is the same as the atomic mass unit ● Atomicnumber=t ​ he number of protons and electrons within a nuclei ○ Unless indicated all atoms are neutral in electrical charge ○ Written as a subscript ● Massnumber=​ the number of neutrons plus protons ○ Written as a superscript to the left of an element's symbol ○ To find # of neutrons subtract atomic number from the mass number *Almost all of an atom’s mass is in its nucleus* ● Isotopes:​​some atoms have more neutrons than other atoms of the same element and have greater masses ○ Examples include Carbon-12 (most common) or Carbon-13 ○ All behave relatively the same in chemical reactions and have 6 protons otherwise they would not be carbon ○ Both carbons shown above are stable this means that they do not have a tendency to lose their subatomic particles ● RadioactiveIsotope: ​Nuclei are unstable and dissipate excess energy ○ Gives off particles and energy ○ Decay can lead to a change in the number of protons and change one element to a different one ○ Radioactive Isotopes can be useful in medicine in very small amounts, generally used in PET scans ○ They can also be very harmful in large amounts ● RadiometricDating:​Scientists use this to to measure the ratio of different isotopes and calculate how many half-lives have passed since an organism was fossilized ○ Half-Life:​​time it takes for 50% of the parent isotopes to decay ● Energy:​capacity to cause change by doing work ● Potentialenergy:​ energy that matter possesses because of its location/ structure ○ Example: water in a reservoir on a hill ○ Matter has a natural tendency to move toward the lowest possible state of PE ○ Changes in PE can only occur in steps of fixed amounts ■ Ball rolling down the steps it can’t go up unless there is work done on it and it can’t stay in between steps ● Electrons energy level is correlated with its average distance from the nucleus ○ ElectronShells​:​an orbit followed by electrons around the nucleus ■ Each has a set energy level and and distance from the nucleus ■ Closest shell has the lowest potential energy and it gets higher the farther out ■ Electrons can move from shells but they must absorb or lose an amount of energy equal to difference in potential energy between position in old shell to new shell ■ Shell gains energy = moves out farther from nucleus ■ Shell loses energy = moves closer to the nucleus ● ValenceElectrons:​ electrons in the outermost shell ○ Atoms with the same number of of electrons in their valence shell exhibit similar chemical behavior ■ Atom with a completed valence shell is unreactive also known as inert (chemically unreactive) Electronorbitals: ● It is good to visualize an electron’s ​orbital path as a concentric circle​ but in reality we do not know the exact location of an electron because it is always moving ○ Orbital:​ three-dimensional space where an electron is found 90% of the time, component of an electron shell ○ Electrons are distributed among a specific # of orbitals of distinctive shapes ○ No more than 2 electrons can be in a single orbital ○ Reactivity of an atom is caused by unpaired electrons in one or more orbitals of its valence shell ChemicalBonding: ● Atoms with ​incomplete valence shells can interact with other atoms ​to fulfill each atom with 8 electrons in its outermost shell ● ChemicalBonding:​when atoms share or transfer electrons and stay close together ○ CovalentBond​:​ Sharing of a pair of valence electrons by two atoms ○ Example: 2 Hydrogen molecules share electron to fulfill their outermost shell; each have a total of 2 valence electrons ○ Molecule:​ 2 or more atoms held together by a covalent bond ○ Single bond ⇒ H-H Double bond ⇒ O=O ○ Valence:​​total number that a valence shell can reach, once this requirement is met they tend to not accept any more electrons ○ Electronegativity​: attraction of a particular atom for the electrons of a covalent bond ■ More electronegative an atom is the stronger the pull ​is towards that atom ○ Nonpolarcovalentbond:​ when two atoms have the same electronegativity so there isn’t one pulling the other more .. They are at a stand-off ​ Example:Two kids of the same weight and strength pulling at one end of a rope (there isn’t much movement one way or the other) ○ PolarCovalentbond:​ when an atom is bonded to a more electronegative atom ​ Example:Bodybuilder versus a small 110 pound man tugging at a rope (It will tend to favor the body builder pulling towards himself) IonicBonds: ● When 2 atoms are so unequal in their attraction that the more electronegative atom completely takes away an electron from the lesser electronegative atom ○ Ion: ​an atom/ molecule with a net electric charge due to the loss or gain of an ○ Cation:​ positively charged ion ( can think of a cat that has PAWS-itviely) ○ Anion​: negatively charged ion ○ Cations and anions attract each other, attraction is called an ionic bond WeakChemicalBonds: ● Covalent bonds are the strongest ● When 2 molecules in the cell make contact they can temporarily favor weak bonds ○ This can be an advantage because they temporarily interact and then separate ○ HydrogenBond:​​attraction between a hydrogen and an electronegative atom ○ VanderWaalsInteraction:​sometimes nonpolar covalent bonds can have both MolecularShape&Function: ● Molecule has a characteristic size and shape important to its function ● Shapes of molecules are determined by the position of the atoms’ orbital ○ Methane molecule is the shape of a completed tetrahedron because all 4 orbitals ○ Molecular shape determines how biological molecules recognize and respond to ● ChemicalReactions:​ making and breaking of chemical bonds ○ Reactants:​starting materials in a reaction ○ Products:​ end result of a chemical reaction ○ Chemicalequilibrium​:​ point at which the reactions offset one another ○ All chemical reactions have to have the same number of atoms on each side


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