Chapter 2: The Chemical Context in Life

essential elements

elements that are required for life (about 20-25% of the 92 natural elements)

what 4 elements make up 96% of living matter?

carbon, hydrogen, oxygen, and nitrogen

what 4 elements make up the other 4% of living matter? (approximately)

calcium, potassium, phosphorous and sulfur

trace elements

elements required by an organism in only minute quantities

True or False: dalton and amu are the same

True

decay

tendency of an atom to lose subatomic particles

radioactive isotope

unstable atom, which has a nucleus that decays spontaneously, giving off particles and energy

what happens when a radioactive isotope decays to the point where it loses a proton?

it transforms the atom into a different element

radioactive tracers

the use of radioactive isotopes as diagnostic tools in medicine

metabolism

chemical processes of an organism

radioactive atoms

cells can use ________ _____ just like non- radioactive isotopes of the same element

why are radioactive isotopes incorporated into biologically active molecules?

to track atoms during metabolism

True or False: tracers CANT be used with various imaging instruments, such as PET scans

False, they can be used

radiation, cellular molecules

although radioactive isotopes are useful in research + medicine, __________ from decaying isotopes is also a hazard to life by damaging _________ _________

radiometric dating

when scientists measure the ratio of different isotopes in fossils / rock and calculate how many half lives have passed since the fossil or rock was formed

energy

the capacity to cause change

potential energy

energy possessed by an object because of its location or structure

why do electrons have potential energy

because they are farther from the nucleus — takes energy to keep electrons far from the nucleus due to the +/- attraction

energy level

the potential energy of an electron is determined by its ______ ______

how can electrons move from one energy level to another?

they can absorb or release an amount of energy equal to the difference in potential energy between the new and old energy levels

distribution of electrons

the chemical behaviour of an atom is determined by the ____________ __ ________ in shells

orbital

3-dimensional space where an electron is found 90% of the time

True or False: matter tends to exist in the highest available state of potential energy

False. matter tends to exists in the LOWEST available state of potential energy

dry ionic compounds

the strongest type of bonds are covalent bonds and ionic bonds in ___ _____ _________.

single bond

sharing one pair of electrons

double bond

sharing two pairs of electrons

valence

an atom’s bonding capacity - usually same as # of unpaired electrons

electronegativity

an atom’s attraction for electrons in a covalent bond (more EN = stronger pull on electrons)

non-polar covalent bond

covalent bond where atoms share electrons equally

polar covalent bond

covalent bonds where atoms share electrons unequally due to the fact that one atom is more electronegative

dipoles

polar covalent bonds cause positive or negative _______ (partial charges) for each atom

ionic bonding

the transfer of an electron from one atom to another, allowing a bond to form between the two

True or False: the transfer of an electron automatically forms an ionic bond

False. the transfer of an electron is not, by itself, the formation of a bond, but instead ALLOWS a bond to form as it results in two ions of opposite charges

covalent bonds

most of the strongest bonds in organisms are ________ bonds forming cell’s molecules

why are weaker interactions crucial to life?

many large molecules need to use weak bonds to be functional as the reversibility of weak bonds allows two molecules to come together, affect one another, then separate again

why is the reversibility of weak bonds advantageous?

allows two molecules to come together, affect one another, then separate

3 types of crucial weak bonds

hydrogen bonds, Van der Waals forces (and LDF), ionic bonds in aqueous solutions

hydrogen bond

bond between a hydrogen atom in a molecule with a positive dipole to a highly electronegative atom in an adjacent molecule
- occurs with H, O, F, N (any other w hydrogen, would be a dipole-dipole force)

Van der Waals interactions

attractions between close molecules due to uneven electron distribution in the molecules, forming temporary and/or instantaneous dipoles

Can Van der Waals forces be strong?

individually they are weak, but collectively they can be strong (ex. Gecko’s toe hairs)

size and shape

a molecule’s ____ ___ _____ are key to it’s function

orbitals

a molecule’s shape is determined by the position of its _______

recognize and respond

molecule shape determine how biological molecules _________ ___ _______ to each other

photosynthesis equation

6 CO2 + 6 H2O —> C6H12O6 + 6 O2 + 36 ATP

dynamic equilibrium

when a reaction occurs in both directions, but concentrations of reactants and products are stabilized in a particular ratio

biology department

the study of life

matter

organisms are compose of ______

element

a substance that can’t be broken down to other substances by chemical reactions

compound

a substance consisting of two or more elements in a fixed ratio

atomic number

number of protons in an atom’s nucleus

mass number

the sum of protons and neutrons in an atom’s nucleus

atomic mass

atom’s total mass - can be approximated by the mass number

isotopes

two atoms of an element that differ in the number of neutrons

what can iodine be used to detect in medicine?

thyroid cancer because iodine in needed and used by the thyroid gland

FORM = FUNCTION

slight changes in form, changes function completely in biology

is cellulose polar or non-polar (extra question)

cellulose looks polar because its not symmetrical, but it’s actually non-polar because long chains of it becomes symmetrical

what bond angle does a water molecule have?

104.5º

what shape is a water molecule?

bent or angular

what do enzymes and catalysts do to bonds?

they put pressure on bonds to break them apart (for both weak and strong bonds)

ionic bond

an attraction between an anion and a cation

ionic compound structure

usually a crystalline lattice

chemical reactions

the making and breaking of chemical bonds

reversible

all chemical reactions are ________

what chemical is responsible for “runner’s high” feeling? (extra question)

endorphins