unit 1 - biochemistry quiz

chem review, bond energy, water, acids/bases, pH

bond energy

a measure of stability of a covalent bond. it’s equivalent to the amount of energy required to break the bond.

Ebreakage = Eformation

potential / free energy

energy stored in bonds available to do work

exothermic

release heat (thermic thermal —> think of temperature)

- when reactants contain more stored energy than products

exergonic

release energy - when reactants contain more stored energy than products

endothermic

energy in - (requires) heat (ends in -mic)

• when reactants have less stored bond energy than the products

enderthermic

energy in - (requires) energy (ends in -gonic)

• when reactants have less stored bond energy than the products

what 4 elements compose most of the compounds found in living things?

carbon, hydrogen, oxygen, nitrogen

what are some other elements found in living things?

calcium, phosphorus, potassium, sulfur

what are trace elements

• chemical elements required by living organisms in very small amounts (less than 0.1% of an organism's total mass)

  • Vital for proper growth, development, and function

  • Iodine, iron, sodium, zinc

molecule

• group of two or more atoms bonded together

• molecules can consist of the same type of atom or different types

isotope

• same number of protons, different number of neutrons, and can have different masses

• different form of the same element
  

what are radioisotopes?

radioisotope: a radioactive isotope of an element

what is radioactivity?

when nuclei of isotopes become unstable and tend to break down/decay, giving off particles of matter

two ways that radiotopes can be useful

• Provide scientific evidence of age of organic materials

• Medical applications and uses

how is electron arrangement related to chemical properties?

• Because only electrons are usually directly involved in a chemical reaction

orbital

a region of space that is occupied by one or two electrons located around the nucleus of an atom

energy levels/shells

•  indicating electrons’ relative distance from the nucleus, each level can hold up to a maximum number of electrons

types of electron orbitals

• One 2s (spherical orbitals) = can hold 2 electrons

• Three 2p orbitals (balloon shaped, x, y, and z axes)

  • Each 2p orbitals can hold 2 electrons

define electronegativity

• A measure of the ability of an atom to attract electrons

• The more electronegative an atom is, the more strongly it attracts electrons

ionic bonds

• a bond that results from the attraction between two oppositely charged atoms or molecules (transfer electrons)

  • Metal + Non-metal

  • Larger ∆EN

covalent bonds

• a bond that results when two atoms share a pair of electrons (shares electrons) to have a stable/full valence shell

  • Non-metal + Non-metals 

  • Smaller ∆EN

bond polarity

• Nonpolar : ∆EN 0 - 0.49

• Polar: ∆EN 0.5 - 1.7

• Ionic: ∆EN 1.7+

(found on periodic table)

what is a polar covalent bond?

• The unequal sharing of electrons between two atoms with different electronegativity

how can a molecule be non-polar despite having polar bonds?

• The symmetry of the molecule can determine if it is non-polar or polar

• Polar molecules are asymmetrical

• Non polar molecules are symmetrical

intermolecular force

• the force of attraction between two molecules

  • Weaker attractions between molecules

intramolecular force

• strong attractions within a single molecule

  • Strong attraction, holding its atoms together through bonds like covalent or ionic bonds

what are van der Waals forces?

Very weak attractions between two molecules, or parts of molecules, when they are close together

define hydrogen bonding

a strong intermolecular force between a hydrogen atom, and a strong electronegative molecule (N, O, and F)

• crucial to function of cells, and cellular processes

4 major types of biochemical reactions

• Dehydration

• Hydrolysis

• Neutralization

• Redox

dehydration reaction

• chemical reaction in which subunits of a larger molecule are joined by the removal of water; also called a condensation reaction

• (water removed)

hydrolysis reaction

•  a chemical reaction in which water is used as a reactant to split a larger molecule into smaller subunits

• (water added)

neutralization reaction

• a reaction in which an acid and a base combine to create a salt and water

redox reaction

• an electron transfer reaction

distinguish between oxidizing and reducing agents

• Oxidizing agents are electron acceptors (oxidizing agent)

• Reducing agents are electron donors (reducing agent)

why is solid ice less dense than liquid water?

• The hydrogen bonding between water molecules lock them into a fixed hexagon crystal lattice structure

• The large space between the molecules increase volume compared to tight packed liquid water

• More volume results in lower density

what is specific heat?

•  the amount of thermal energy required to raise the temperature of a given quantity of a substance by 1 °C

  • high temperature are needed to break enough bonds in water for it to boil

distinguish between cohesion and adhesion

• Cohesion: The tendency of similar molecules sticking to one another

  • Example: water sticking to water

• Adhesion: The tendency of molecules of different substances to cling to one another

  • Example: water sticking to a glass window

what is an aqueous solution?

Water is the solvent and the molecules or ions of the other substance are the solute

distinguish between hydrophilic and hydrophobic molecules

• Hydrophilic molecules: polar or charged molecules that are strongly attracted to water

• Hydrophobic molecules: non-polar molecules that are not strongly attracted to water

what is the auto-ionization of water?

• Autoionization: the process in which a molecule spontaneously dissociates into ions

• When 2 water molecules react with each other to form a hydronium ion (H3O), and a hydroxide ion (OH-)

what does pH stand for?

potential of hydrogen

• each level in pH represents a 10x difference in acidity/basic

why can water act either as an acid or base?

because it is an amphiprotic substance, meaning it can donate a proton (acting as an acid) and accept a proton (acting as a base)