SC-100 Review -Quiz 4
Nucleus Characteristics
What happens in the nucleus has almost nothing to do with the atom’s chemistry and vice versa.
The amount of energy involved in changes in the nucleus are much greater than that from the electrons.
Proton: Positive electric charge of +1; About 2000 x the mass of an electron
Number of protons determines number of electrons in neutral atom and thus the chemical identity of the atom.
Neutron: No electric charge; About same mass as proton
Mass of the atom is mostly in the nucleus.; Size of atom comes from the electrons.
Number of Protons defined as the Atomic Number (also Proton Number, Z)
Atomic Number determines the Element.
No. of Neutrons (Neutron Number,N) plus No. of Protons defined as the Atomic Weight or Mass Number
Isotopes- Same Atomic Number with more than one Atomic Weight. ; Same Number of Protons, different numbers of neutrons.
The “Strong Force” Why don’t the protons repel each other?
Attractive force operating only over distances the size of the nucleus.
Must be much stronger than gravity or electromagnetism, hence the name “Strong Force”
Kinds of Radioactivity
Alpha Decay- Emits large particle of 2p + 2n (alpha particle) (He-4)
Beta Decay-Neutron becomes a proton, an electron and a neutrino. Proton remains in nucleus, other two travel out.
Gamma Radiation-Proton or neutron shifts energy level and emits high energy photon.
Half-Life Time required for half of batch of a radioactive isotope to decay.
1 1/2, 2 1/4, 3 1/8, 4 1/16,etc...
Radiometric Dating Carbon-14. Half-Live 5700 years. Dating of once-living things
While alive C-12 to C-14 ratio is same as atmosphere. Upon death ratio begins to change as C-14 decays. Bone, wood, cloth etc.
50,000 years is limit of measureable ages for C-14
Longer Time Spans K-40 half-life 1.25 billion years; U-238 4.5 byears Rb-87 49 byears
Used to date rocks and minerals
Energy from the Nucleus E = mass x (c squared) Fission U-235 Fusion Hydrogen
Ecology & Ecosystems
Ecology: Study of interactions among organisms and with their environment
Ecosystem: Interdependent collection of living things. The plants and animals in a given area together with their physical surroundings.
Characteristics of Ecosystems
1. Every Ecosystem consists of both Living and Nonliving Parts.
2. Energy flows through Ecosystems.
3. Matter is recycled by Ecosystems.
4. Every Organism occupies an Ecological Niche.
5. Stable Ecosystems achieve a balance among their Populations.
6. Ecosystems can be disrupted by changes in environment or species.
1. Every Ecosystem consists of both Living and Nonliving Parts.
Ecological Community
Chemical and Physical Environment: ground water, soil, atmosphere, average temperature, rainfall, winds, Sun exposure
Example of Living Parts: Forest- trees, shrubs, insects, birds, snakes, squirrels, fungi, bacteria
2. Energy flows through Ecosystems.
The Food Chain (Food Web) passes ENERGY and CHEMICAL COMPOUNDS
Insects eat plants. Birds eat insects. Bacteria and fungi decompose dead birds
Trophic Levels Ten Percent Rule
4. Every Organism occupies an Ecological Niche.
The mode of survival of the species, the way it obtains matter and energy.
Bats: warm-blooded, eat insects, nocturnal
Mushrooms: Grow in shaded wooded areas
Competition is usually among organisms that prefer the same ecological niche
5. Stable Ecosystems achieve a balance among their Populations.
Called “Homeostasis”; Limited resources must be shared among all the individual organisms in an ecosystem
Population levels vary with food availability but the relative mix of species is fairly constant.
6. Ecosystems can be disrupted by changes in environment or species.
“The Law of Unintended Consequences”:
It is virtually impossible to change one thing in a complex system without affecting other parts of the system, often in unpredictable ways. Lake Victoria-Nile Perch Rabbits in Australia
Global Ecosystem: Closed and Unpredictable; Waste Disposal Landfills don’t decompose
Ozone Layer; Acid rain ; The Greenhouse Effect
Ozone Layer: Ozone: Tri-atomic Oxygen O3; Ozone absorbs UV at 20 mile altitude.
Scientists believe before the Ozone layer formed life was restricted to oceans
The Ozone Hole: Seasonal variation over the South Pole.
Chloroflourocarbons (CFCs) : Sprays and Air Conditioning, Very stable, diffuses into stratosphere
Ozone Layer
UV light decomposes CFCs but the free chlorine now reacts with ozone to produce diatomic oxygen:
2O3 + Cl + sunlight --> 3O2 + Cl Solution: Ban on Manufacture of CFCs
ACID RAIN: Combustion By-products: Nitrogen Oxides; Sulfur Oxides; Hydrocarbons
Smog: NOx and HC exposed to sunlight
Acid Rain: NOx and SO2 produce nitric and sulfuric acids which fall in rain.
Solution: Reduce smokestack and auto emissions of these pollutants.
Raises many economic issues
Global Warming & the Greenhouse Effect
The Atmosphere is transparent to visible and UV light. (Incoming)
Surface temperatures on Earth re-emit at Infra-Red to which Atmosphere is somewhat opaque. (Outgoing)
Result: Without this Greenhouse Effect the global average temperature would be minus 20 C.
Gases which contribute: CO2, H2O, CH4, CFCs.
Concern: Increased human activity increases CO2 and leads to warmer temps.
Much debate over seriousness of problem. Global Models are too crude to trust 100%
“Fixes” may make problem worse.
Sensitivity: 0.5 C warming corresponds to moving 100 miles north. Two Degrees C would:
Washington --> like “Atlanta”; Minneapolis --> like “St. Louis”
Characteristics of Life: Use energy; Chemical reactions within cells; Reproduce; Regulate energy and respond to environment; Share genetic code; Descend from a common ancestor
Classifying Living Things Linnaean Scheme
Species (smallest)Genus;Family;Order;Class;Phylum;Kingdom (largest)
Species: Species is a population of similar organisms who produce fertile offspring.
How many species? Best guess: several million
Kingdoms
Monera: Single-celled organisms lacking a cell nucleus.
Protista: Single celled organisms with a cell nucleus.
Fungi: Multi-cellular organisms that dissolve dead organisms and absorb the nutrients
Plants: Multi-cellular organisms that get energy directly from Sun by photosynthesis
Animals: Multi-cellular organisms that get their energy and nutrients by eating other organisms.
Terms: “Prokaryote” cell: Has No Nucleus -- MoneraKingdom
“Eukaryote” cell: Has Nucleus -- All other Kingdoms
The Molecules of Life: Organic Molecules; Most molecules in living systems are CARBON-based.
Only a few elements comprise most of Life’s molecules: H,O,C,N = 99.4%, Ca, P = 0.4%
Most are “modular” built of smaller repeating units
Molecular Geometry controls Reactions
Amino Acids: Carboxyl + Amino = Amino Acid Uses H,O,C,N
“Condensation” (again): Take out H + OH from two amino acid molecules and get a “peptide”
Continue this peptide bonding and the result is a ”Protein”.
Proteins: Roles :Structural Connective tissue, hair, nails, tendons
Growth & Maintenance, Needed for growth and repairs, Enzymes, Control reactions
Regulate movement of material through cell walls
Proteins: Structure Amino Acids Only 20 different amino acids are found in living systems
Essential(8) vs Non-Essential (12)- We make the 12 We must get the “Essential” 8 in our diet
Protein in our diet that supplies Essential A. A. in same proportion that our bodies need them are “high quality”. Or eat a combination that does same. (Vegetarians especially need to watch proportions.)
Proteins: Levels of Structure Primary- (Amino Acid Sequence )Secondary Tertiary Quaternary
Carbohydrates: Roles: Source of energy, form solid structures
Structure Uses C, H, O Mono-saccharides - SUGARS Polysaccharides
Starch - Humans can digest starch, Cellulose (fiber) - Humans can’t digest cellulose
Lipids: Definition - Will not dissolve in water: Fats, waxes, oils, greases
Roles energy -very efficient in storing calories, cell membranes, hormones, chemical messengers,
insulation, cushioning :
Fatty acids: Saturated and Unsaturated fats; Hydrogenation (Saturating the Unsaturated)
Health Concerns: Saturated fats are needed to make cholesterol, but too much makes fatty deposits in arteries. When fat was not so easily available this was not a problem.
Phospholipids: Phosphate group (1P + 4 O) Negative charge makes this part attracted to water (“hydrophilic”) Form the walls (“membranes”) of cells by aligning in a double layer with hydrophilic ends on the outside and the “hydrophobic” on the outside.
RecapAmino: Acids form Proteins: Sugars form Carbohydrates; Lipids include FatsPhospholipids
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