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Chapter 2

BIO206 Lecture 2 Chapter 2 5.pdf

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University of Toronto Mississauga
George S Espie

Lecture 2/ Chapter 2/ 5 September-14-13 12:42 PM Life - Based on organic chemistry/ reactions on watery, aqueous solution/ complex/ collectionsof polymericmolecules (formed from chains of chemical subunits/ tightly regulated Cells are made of relatively few types of atoms Atom - center positive nucleus surrounded by negative electrons - Nucleus = protons and neutrons - Element can exist in isotope - Protons= atomicnumber Atomic weight/ molecular weight - protons + neutrons Avogadro's number = 6 x 10^23molecules The outermostelectronsdetermine how atoms interact - The distribution of elements in Earth's crush differs radically from that in the tissues of an animal - Covalent bond - electrons are shared, H2 ○ Characterized by particular geometries ○ Vary in strength - in kcal/ mol or kJ/ mol ○ Types: single bond(rotatearound bond axis), double bond (stronger, shorter) - Ionic bond - electrons are transferred ○ A type of electrostaticattraction - occurs b/w oppositely charged atoms ○ Ex. NaCl - Polar covalent - unequal sharing of electrons(negative and positive poles) Electrostaticattractions help bring moleculestogether in cells H2O is held together by H bonds - Hydrophilic - Hydrophobic Some polar moleculesform acids and bases in water - H3O+ hydronium ion - acid - pH<7 acidic, pH>7 basic, pH=7 neutral - Strong acids - lose protons easily - Buffers - keep everything neutral inside the cell Cell is formed of carbon compounds - organic molecules - Other moleculesare inorganic (ex: water) Cells contain four major families of small organic molecules - Monomersform polymericmacromolecules - 4 major families: sugars, fatty acids, amino acids, nucleotides - Large units: polysaccharides, (fats, lipids, membranes),proteins, nucleic acids Sugars are energy sources for cells and subunits of polysaccharides - Sugars - monosaccharides(CH2O)n - Isomers - same formula but different structure - Optical isomers - isomers that are mirror image (D- and L-forms ) - Linked by covalent bonds known as glycosidic bond - Condensation reaction - water is expelled as bond forms - Hydrolysis - water is consumed - Polysaccharides(glycogen in animals and starch in plants) Fatty acid - componentsof cell membranes - Amphipathic - both hydrophilic(carboxyl)and hydrophobic(hydrocarbonchain) regions - Ex: Palmiticacid - Tail is saturated - max # of H, no C-C double bonds - Ex: oleic acid - unsaturated tails (one or moredouble bonds) - Ex: oleic acid - unsaturated tails (one or moredouble bonds) - In cytoplasm,fatty acids are stored in the form of triacylglycerol Amino acids - subunits of proteins - Peptide bond - linkage b/w two adjace
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