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Bios 1700 Chapter 2 Notes

by: Shannan Dillen

Bios 1700 Chapter 2 Notes BIOS 1700

Marketplace > Ohio University > Biology > BIOS 1700 > Bios 1700 Chapter 2 Notes
Shannan Dillen
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These notes cover the basics of chemistry and how it relates to biology. It covers the periodic table, chemical bonds, carbohydrates, lipids, etc.
Biological Sciences I: Molecules and Cells
Soichi Tanda
Class Notes
Biology, BIOS




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This 6 page Class Notes was uploaded by Shannan Dillen on Monday October 10, 2016. The Class Notes belongs to BIOS 1700 at Ohio University taught by Soichi Tanda in Fall 2016. Since its upload, it has received 18 views. For similar materials see Biological Sciences I: Molecules and Cells in Biology at Ohio University.


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Date Created: 10/10/16
Chapter 2: The Molecules of Life Atomic Number – number of protons; defines the element Most atoms (except hydrogen):  Number of protons = number of neutrons  Number of protons + number of neutrons = atomic mass Isotopes – atoms of the same element with a different number of neutrons Ex: carbon-14 (6 protons + 8 neutrons) Ions – atoms which are charged; have lost or gained an electron How are electrons organized in the atom? Shells or energy levels – various distances away from the nucleus -shells further from nucleus are at higher energy level Within shells electrons occupy… Orbitals – areas where electrons are found most of the time - -each orbital can hold 2 electrons (e ) -shells beyond first have more than one orbital *atoms most stable at lowest energy level The Periodic Table Tell us about valence electrons - e in outer shell - determine activity (how it forms bonds with other atoms) Elements in rows - same number of orbitals - e fill outer shell as you go across the row left to right Elements in a column (group) - - same number of e Chemical Bonds Covalent bonds – atoms share electrons *most stable molecules -fill outermost shell with e - Ex: H – there is only one shell, only two e needed Molecular orbital – merged orbital of 2 atoms sharing electrons - Atoms larger than helium have more than one outer shell, 8 e needed to complete outer shell Polar covalent bonds – e not shared equally -e spend more time ear one end of atom than the other H O 2 - Oxygen is more electronegative than hydrogen - e spend more time with oxygen Electronegativity – strength with which atom attracts e - Hydrogen bonds – interaction between a hydrogen atom, covalently bound to an electronegative atom, and an electronegative atom of another molecule Water is polar molecule (2 ends are different, one hydrophobic, one hydrophilic) -forms H bonds between oxygen atoms and hydrogen atoms of neighboring atoms H bonds – weaker than covalent bonds BUT important for: - biological function of water - structure of DNA, RNA, and proteins H bonds make water cohesive (surface tension) - contribute to water movement in plants Temperature affects hydrogen bonding in water - The lower the temp., the more H bonds form (water molecules are moving less) As water is heated, energy is used to break H bonds. - Water resists changes in temp. Ionic bonds – one atom “steals” electrons from another - Like an extreme polar covalent bond One atom more electronegative than the other - More electronegative – negative ion - Less electronegative – positive ion Opposite charges attract – form ionic bond When ionic compounds are added to water… - Polarity of H2O molecules allows them to interact with charged ions – so things like salt dissolve - Water’s polarity makes it good solvent for ionic compounds and polar molecules Water is the Solvent of Life - Most of a cell is water (aqueous environment) - Hydrophilic – water loving o Polar molecules (ex: sugars) + 2+ o Charged molecules (ex: Na , Ca ) - Partial charges on water interact with charges on solutes to dissolve - Hydrophobic – water fearing o Nonpolar molecules (ex: lipids) o Doesn’t dissolve in water o No partial charges – e shared equally pH – important characteristic of water -measure of acidity Very small % of water molecules exist dissociated: H (hydrogen ion) and OH (hydroxide ion) pH = -log[H ] -7 + So in pure water… 10 M H means pH = 7 Change of 1 pH unit = 10 fold change in H +  pH 7 = 10 M H +  pH 6 = 10 M H + 1 pH = * 10 + Acids – release H - pH decreases (more acidic) + Bases – accept H - pH increases (more basic) Organisms need to regulate pH Human blood – physiological pH = 7.4 Why is pH important? -Biological process function correctly at specific pH Carbon – Backbone of Life Forms many diverse compounds with many other elements Each C atom can form 4 covalent bonds Molecular orbitals form tetrahedral shape – allows rotation around each bond Can form change or ring structures Carbon can also form double bonds - shares 2 pairs of electrons - Because 2 pairs of e are shared, only 3 atoms are bound o Total electrons shared per C atom is still 4 - Rotation does not occur around a double bond Isomers – same chemical formula but different structure Even with same type and number of atoms, C can form different compounds 4 Types Organic (carbon-based) Macromolecules  Proteins o Perform many diverse functions in cells o Most enzymes  Nucleic Acids o Encode info (DNA and RNA) o Translate coded info into functional proteins  Carbohydrates o Energy metabolism  Lipids o Form membranes – biological barriers *Proteins – chain of small molecules called amino acids Perform most jobs in cells, including: - Catalyzing chemical reactions (enzymes) - Communication between cells - Cell structure Cells use 20 different amino acids to make proteins - R group is different in each one Cells have thousands of different proteins - Each type of protein has specific order, or sequence, of amino acids, based on R groups - Sequence determines: o Structure – shape protein folds into o Function – what job the protein does Peptide bonds – link amino acids together *Nucleic Acids – chains of nucleotides 2 types: - DNA – deoxyribonucleic acid - RNA – ribonucleic acid Base of nucleotide is what makes it different 5 nucleotides used in DNA and RNA DNA: Thymine (T), Cytosine (C), Adenine (A), Guanine (G) RNA: Uracil (U), Cytosine (C), Adenine (A), Guanine (G) Phosphodiester bonds – link nucleotides together DNA Structure Double helix – two strands coiled around each other Base pairs: Adenine (A) :: Thymine (T) Guanine (G) :: Cytosine (C) *Carbohydrates – chains of sugars  5 or 6 carbons with oxygen and hydrogen  6 carbon sugars have same chemical formula (C H O 6 12t6different configurations  Can be linear or cyclic (more common) Linked by glycosidic bonds  Used for storage of energy  Attached to some proteins (glycoproteins) and lipids (glycolipids) to change function *Lipids – hydrophobic – based on hydrocarbon chain – string of C and H atoms Fatty acid – simplest lipid -hydrocarbon chain with carboxylic acid Saturated – no double bonds Unsaturated – contains double bonds Fats - Glycerol molecule with 3 fatty acids attached - Energy storage - Triacylglycerol (fat) Lipid interactions – van der Waals forces and lipid packing -due to hydrophobicity water is excluded and lipids pack tightly together  Constant motion of e causes temporary small charges that affect neighboring molecules – van der Waals forces (weak)  Unsaturated fatty acids are not straight o Less tight packing and weaker interaction  Melting point decreases  Saturated fats (ex: butter) – solid @ room temp.  Unsaturated fats (ex: fish oils) – liquid @ room temp. Cholesterol – a lipid with ring structures -found in membranes


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