BSCI 105 Week 1 Notes
BSCI 105 Week 1 Notes BSCI 105 - 5666
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This 4 page Class Notes was uploaded by Natania Lipp on Wednesday February 3, 2016. The Class Notes belongs to BSCI 105 - 5666 at University of Maryland - College Park taught by Dr. Michael Keller in Winter 2016. Since its upload, it has received 110 views. For similar materials see Principles of Biology I in Biology at University of Maryland - College Park.
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Date Created: 02/03/16
29 January 2016 Friday BSCI 105 Molecules of Life: The Chemistry The fundamentals: - Elements and atoms - Compounds and molecules Understanding molecules = understanding interactions between elements - In order to understand how molecules work, you have to understand how elements combine to form molecules. Elements: substances that cannot be broken down to other substances by chemical reaction. • All organisms are made up of matter, and all matter is made up of elements. • There are 92 natural elements. • 25 of those elements are in living organisms. • 96% of the elements that living organisms mainly just use are hydrogen, nitrogen, carbon, and oxygen. Atoms: the smallest units of matter that still retains the properties of an element. • Chemical reactions are determined by characteristics of atoms. • Atoms are made up of: - Protons - Electrons - Neutrons Periodic table of elements • Shows how big each element is • Organized left-top to right-bottom by size • Number of electrons is equal to number of protons in each element • The behavior and distribution of electrons in atoms is the basis for chemistry • Shells are the atoms’ layers that hold electrons. - The ﬁrst shell holds 2 electrons - The other shells hold 8 electrons - Atoms that don’t have a full outer shell — meaning that their outermost shell does not have its maximum capacity of electrons — are “unhappy”, or “unpaired” • Electrons occupy orbitals within shells. • Each orbital can hold 2 electrons • The ﬁrst shell has 1 orbital, and the other shells have 4 orbitals. • Each orbital takes one electron ﬁrst, then another one after all of the orbitals have gotten their ﬁrst one. • The entire process of atoms interacting and forming molecules depends on the unpaired electrons. • Valence electrons: electrons in the outermost shell of an atom. Compounds: made up of 2 or more interacting atoms. • Valence electrons form bonds. • Compounds vs. Molecules: compounds are smaller, molecules are bigger. Molecular bonds: - Covalent - Ionic - Hydrogen • There are different bonds because atoms differ in electronegativity. • Electronegativity: how good an atom is at attracting electrons. • The protons’ ability to attract electrons is decreased by shells’ insulation, so the more shells an atom has, the less electronegative it is. • Nitrogen, oxygen, and ﬂuorine have the most electronegativity. - Look for nitrogen and oxygen especially; they give the molecule potential to have uneven sharing electrons. • Nonpolar covalent bond: equal sharing of electrons • Polar covalent bond: uneven sharing of electrons • Polarity = an electron cloud that is uneven. • Ionic bond: giving or taking of electrons between atoms. • Hydrogen bond: electrostatic attraction between compounds having highly polar bonds in symmetric conﬁgurations. 1 February 2016 Monday BSCI 105 Water Properties of water: • Water molecules are polar. • Hydrogen bonds - Always the same length - Number of bonds varies because the bonds form or break as molecules move. - A bunch of hydrogen bonds bonded together cause water to act as one big mass, which gives water many interesting properties. - Cohesion: when water sticks to itself. - Adhesion: when water sticks to other things. - Surface tension: when water pushes back. - Heat capacity • Water is a polar solvent. • It has a high capacity for dissolved salt. • Anything that water can make a hydration shell around, it can dissolve. • It cannot dissolve non-polar molecules. • Hydrophobic molecules are nonionic and non polar substances that repel water, like oil. • These molecules are “pushed” out of the solution. pH = the measure of the amount of hydrogen concentration that ranges in value from 0 - 14. • Water forms a certain amount of H+ and OH- ions dynamically. • The more H+ in a liquid, the more acidic it is. Ice ﬂoats on water. • Molecules are always moving • When water freezes, molecules stop moving and the bonds stop changing • When frozen, water expands rather than increasing in density. • This process makes ice less dense than water. • Ice’s surface tension pushes back against water, and water pushes back against the ice. • The ice insulates water’s surface from freezing. 3 January 2016 Wednesday BSCI 105 The Molecules of Life: Organic Chemistry Carbon is useful because it can create so many different molecules. • It is the lightest element with 4 valence electrons — only has one shell. • Orbitals avoid each other. • Tetrahedral shapes vary, and create geometric variety. • Carbon is the reason for a lot of molecular diversity. It can vary in carbon backbone, and in functional side groups. Carbon backbone: the arrangement of atoms • Carbon can form more than one bond with the same element, which can allow double bonds or triple bonds. • Double bonds make the element unable to spin freely, so the placement of atoms in double bonds can change the structure of the molecule. • It can also create rings and attach back to itself. • Isomers have the same set of atoms, but are arranged differently. • Types of isomers: - Structural isomers: differ in covalent arrangements of their atoms. - Geometric isomers: a change in shape of molecules with the same atoms. - Enantiomers: the mirror image of a molecule — the same shape ﬂipped to mirror the original. Ex: Thalidomide was invented to prevent morning sickness, but when put into the blood if ﬂips and causes birth defects. Functional groups: the reactivity and chemical properties of organic molecules. • Hydroxyl group — Polar because of electronegative oxygen, forms hydrogen bond with water and helps dissolve compounds. • Carbonyl group — double bonds of carbon and oxygen are added to molecules. • Carboxyl group — it can donate a hydrogen molecule, because the covalent bond between oxygen and hydrogen is so polar. • Amino group — acts as a base and can pick up hydrogen from the surrounding solution • Sulfhydryl group — two sulﬁdes form a bond and create a different protein structure. • Phosphate group — glycerol phosphate bonds 4 oxygen molecules • Methyl group — an extra molecules is added, affecting the expression of genes when on DNA or on proteins bound to DNA.
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