Biology: Dna and Covalent Bonds Essay

Ch 1.
Be able to describe the steps in the scientific method and give example for each step: Observation Question Consult prior knowledge Hypothesis Must be testable & falsifiable In a form of an “If__, Then__” statement Cannot be proven May be rejected in the future by more sophisticated experiments or new tools Test hypothesis Collect data Analyze data Report findings If you accept hypothesis, publish If you reject hypothesis, revise

Be able to identify the shared characteristics of life: Are organized Regulate internal environment Respond to environment Process energy Reproduce Grow & develop Adapted to environment

Be able to generally explain organization of living:
Life is UNIFIED (shared in characteristics) but also very DIVERSE (differences in structure & function) and can be explained by evolution.

Difference between a theory and a hypothesis:
Theory – has been studied & tested Hypothesis – a suggested explanation for an observable phenomenon

Ch. 2
How are elements organized in the periodic table.

Atomic structure including charge relationships: protons (+) found in nucleus neutrons (0/neutral) found in nucleus electrons (-) found in the electron cloud

Atomic number (protons) vs. Atomic mass (protons + neutrons) and radioactive isotopes
(differ in number of neutrons, ex. Carbon 14) CARBON-12 CARBON-13 CARBON-14
PROTONS 6 6 6
NEUTRONS 6 7 8
ELECTRONS 6 6 6
ATOMIC MASS 12 13 14

Energy shells: valence shell. Chemical reactivity.

Electronegativity of elements Atoms attraction for shared electrons

Ionic vs. covalent bonds. (Na+Cl-) and (C2H6) Ionic bonds – opposite charges attract Ionic bonds between ions create compounds

Covalent bonds – sharing of electrons Covalent bonds between atoms create molecules

Polar vs. non-polar covalent bonds
Polar – unequal sharing of electrons

Nonpolar – equal sharing of electrons

Hydrogen bonding and characteristics of water; cohesion, Large heat capacity, Lower density as a solid, and good solvent. Hydrogen bonds hold polar molecules together

Cohesion – water molecules stick together Ex: water spots in the water bottle Large heat capacity – water takes a lot of energy to be broken Ex: keeps us cool Low density as a solid – ice has more volume; ice is less dense than liquid, ice floats Ex: polar bears habitat Good solvent – water allows polar molecules to dissolve Solute – what is being dissolved (salt) Solution – liquid consisting of substances (salt water) Acid (protons donor) and base (proton acceptor), pH – measure of H ion concentration
Buffer solutions and their role Acid – has more protons Base – less protons Buffer – minimize changes in pH, absorbs or release H+ to keep pH neutral

Structure and importance of: carbohydrates lipids (long chain hydrocarbons) nucleic acids (nitrogenous base + sugar + phosphate group) proteins (alpha carbon + amino group on one side and carboxylic acid group on other side + a unique R group) Carbohydrates: monosaccharide, disaccharide and polysaccharide Monomers – monosaccharide
Sugars
Hydrophilic (water)
Polymers – polysaccharides (multiple sugars) lng chain of glucose
Starch (found in wheat)
Glycogen (found in humans: liver/muscle)
Cellulose (found in plants)
Polysaccharides – many simple sugars linked together with covalent bonds
Store energy (glycogen/starch)
Provide structure (chiton/cellulose)

Lipids:
Triglycerides
Composed of a glycerol head & 3 fatty acids Fats/oils
Unsaturated
Missing hydrogens, cannot pack together

Double bond Olive oil
Saturated
Can be packed together

Solid
Sterols
Regulate growth & development (hormones) Cholesterol is an important part of cell membranes Are all based on a structure featuring four fused carbon rings

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