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NATS TEST #1 review.docx

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York University
Natural Science
NATS 1675
Barbara Czaban

NATS TEST #1 notes in random  The second most common form of the water molecule on our planet is ice.  Most animals and plants contain more than 60% water by volume.  Atomic structure of water o H side = (+) o Other side = (-)  Powerful solvent due to molecular polarity o And strong surface tension  When the water molecule makes a physical phase change its molecules arrange themselves in distinctly different patterns. o Ordered = frozen o Semi ordered = liquid o Random = vapour o  Unique Physical Properties of H2O 1. High specific heat 2. Pure state = neutral pH a. Neither acid/basic 3. Conducts heat easily 4. Liquid form a. >100c = frozen b. < 100c = gas 5. Universal solvent 6. High surface tension a. Adhesive b. Elastic 7. Only substance that exists in solid liquid and gas  H2O = 70% body weight  Used to dissolve molecules chem rx occur  Organism moved to land = carried H2O  The physical & chemical properties of liquid water make life possible 1. 1. The capacity to dissolve or repel substances 2. Cohesiveness 3. Temperature-stabilizing effects
 4. Always in flux – transports materials 5. In a liquid form over range of temperature from 0-100°C  COVALENT BONDS o Non-polar = sharing e equally  H gas (H-H)  Methane (CH ) 4 - o Polar= do NOT share e  Water  O2 = (-) charge  H = (+) charge  HYDROGEN BOND o Weakest bond o H(+) attracted to polar covalent (-) molecule  IONIC BOND o Atom loses an e = (+) ion o Atom loses an e = (-) ion  Water is clingy due to polarity + H bonding  “spheres of hydration” solvent  cohesive water = due to H bonding  water protects organism from rapid change temps  water in blood to distribute heat  evaporation carries away heat  H2O  H+ + OH-  H+ = proton  ACIDS o Donate  H+ o Increase H+ concentraition  BASES o Accept  H+ o Decreases H+ concentration  pH SCALE o measures conc. Oh H+ o acid / base  BUFFERS o Help keep pH normal  Add H(+) if needed  Take away H(+) if needed  Carbonic acid – bicarbonate buffering system o Keep pH of blood = 7.4 o If H+ levels in blood decrease  Dissociate to release H+ o If levels in blood increase  Combine bicarbonate ions to form carbonic acid  Which in turn o Dissociate into CO2 + H2O  H+ exhaled out o Atoms  elementsmolecules  About 92 naturally-occurring elements  90% of body is composed of HONC o H hydrogen o O oxygen o N nitrogen o C carbon  Atoms o nucleus = proton + neutron o shells  (-) electrons orbit it  cloud of electron o ATOMIC #  # of (+) o ATOMIC WEIGHT  (+) + (=) o octet rule o 1 shell = 2 e- o <1 shell = 2>8 e- o outershell = valence shell o stable = all shells filled  ISOTOPES o Same # (+) o Different # (=) o UNSTABLE ISOTOPES  Radioactive isotopes  Unstable nucleus spontaneously decomposes o Emitting rays of energy  Can be used as tracer o Ex/ C14 dating / medical imaging  REACTANTS  PRODUCTS  6CO 2 + 6H O --2 C H 6 12 6 O + 6O 
 2 6 carbon dioxide + 6 water --> 1 glucose + 6 oxygen (Reactants) (Products)  atoms react o unfilled valence shells  basic structural components of living entities o atoms / molecules o chemical rx  metabolism o metabolism  sum of processes that build maintain + destroy body  cells = smallest unit of life  cell properties o highly complex o genes o reproduce o acquire+use energy o carry out chem rx o enggne in mechanical activities o respond to stimuli o capable to self-regulate o evolve  THEORIES ON THE ORIGIN OF LIFE 1. Created by God(s) 2. Originated from non living matter 3. Came from somewhere in the universe  Credible hypothesis – CHEM EVOLUTION o Life evolved from chemicals  4 STAGES in the FORMATION OF LIFE 1. abiotic synthesis 2. joining small molecules a. monomer  polymer  macromolecules 3. genetic material – self replication 4. protobiont a. evolutionary precursor b. primitive cells  ABIOTIC SYNTHESIS OF ORGANIC MOLECULE o 1953 Stanley Miller and Harold Urey  after sparking the condensed atmosphere they simulated rain by condensing the gas through cold water which recreated water they sampled the water and it contained amino acids that were part of the nucleotides that make up dna and rna  CONCLUSION: organic molecules can be synthesized abiotically o Life from space  Earth was bombarded by comets providing supplies for organic molecules  JOINING SMALL MOLECULES INTO POLYMERS o Abiotic origin hypothesis  Predicts monomers link to form polymers  Dripping solution of monomers onto hot sand clay rock o Catalyst  Similar conditions likely on early earth o Spontaneous assembly of molecules  chemical interactions  Start of metabolic pathways  Molecular structures of new molecules – how they interact with others  ORIGIN OF SELF-REPLICATING MOLECULES o RNA world hypothesis  RNA st  1 genetic material with self replication  DNA after o DNA replication  Structure serves as templates  Replicates from 5’-3’  A-T / C-G o RNA replication  Strand acts as template  “blueprint” with info for how ribonucleotides will arrange  A
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