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week 1 - chp 2.docx

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Health Sciences
HSCI 100
Nienke Van Houten

Chapter 2 – chemistry comes to life Matter – anything that has weight/takes up space (solid,liq,gas) Molecules – atoms bonded together (can be made of same/diff atoms) ATOMS - Atoms – smallest units of an element that retain elements physical/chemical properties - Center = protons + neutrons - Electrons spin in shells around nucleus (2,8,8,18) - Electron mass = negligible ELEMENTS - Elements – basic building blocks of matter that cannot be broken down by chemical means o 92 naturally occurring elements o 90% of human body – carbon, nitrogen, oxygen, hydrogen o Trace elements (iron) - Atomic weight = mass of protons + neutrons + electrons of most stable isotope - Atomic number = number of protons (&neutrons if neutral) Isotope – same number of protons, diff # neutrons Compound: 2+ elements combined - Held together by ionic/covalent bonds - Gain/lose/share electrons Covalent bonds: (e.g. CH4) - Strongest - 2+ atoms share electrons in outer shell - Triple>double>single bond (strongest) - MOLECULE – chem structure held together by covalent bonds Ionic bonds: (e.g. NaCl) - Ion – atom/group of atoms with +/- electrical charge - Weaker than covalent - Attraction of oppositely charged ions (not sharing electrons) Hydrogen bonds: - Electrons of covalent bond shared unequally = POLAR BOND o Weakest bond o Different ends of molecules = different charges - Hydrogen bond = attraction between slightly positively charged H & slightly negatively charged atom near by - Weak bonds that form water molecules or between nucleotide bases of 2 strands of DNA CHARACTERISTICS OF WATER - Liquid @ room temp - Liquid water doesn’t change temp quickly - High heat of vaporization (boiling point) - Frozen water less dense than liquid - Surface tension + capillary action (hydrogen bonding) - Solvent for polar molecules Which property of water provides the cooling effect of sweating? High heat of vaporization - Takes a lot of energy to cause water to evaporate - Water molecules that evaporate carry away a lot of heat, cooling the surface Structure of a polymer including formation through dehydration synthesis * breakdown through hydrolysis - Polymer (macromolecules) – long molecules of many identical/similar building blocks strung together o Individual units = monomers (e.g. amino acids) - Dehydration synthesis – makes polymers. Removes water - Hydrolysis – add water to break covalent bond MACROMOLECULES CARBOHYDRATE (aka sugars/starches) - Subunits (monosaccharides) - Made of C,H,O (H&O are 2:1 ratio) - Function: o Immediate energy and long term energy storage o Structural molecules - Simple: monosaccharide (1 carbon ring, glucose) o Oligosaccharides – chains of few monosaccharides  disaccharide (2 carbon rings, maltose) - Complex: polysaccharide (many carbon rings) glycogen, starch, cellulose - We cant eat grass because enzymes in digestive tract cannot break down linkages in cellulose LIPIDS - Molecules do not dissolve in water (non-polar) - Energy molecules found in cell membranes - Function: log term energy storage, membrane - 1.
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