Unit 1 (Ch. 1-7) Flashcards
three concepts of biological science:
- life is made up of cells (cell theory)
- life evolves
- life processes information
what was the first evidence of cells?
came from the invention of microscopes (1600s)
two tenets to cell theory:
- all organisms are made up of cells
- all cells come from preexisting cells
what did louis pasteur do?
observed that cells come from preexisting cells, not from spontaneous generation, which supports one tenet of the cell theory.
why is the theory of evolution (life evolves) important to cell theory?
it explains where organisms come from and how they’re related, which therefore provides an explanation of where cells come from.
why was it important that pasteur used one flask with an open mouth and one flask with a sealed mouth in his experiment?
the sealed flask was a swan-neck flask, so nutrient broth settled in the neck. this prevented air flow and therefore growth in the flask.
what common characteristics do all cells share?
- use the same biochemical molecules
- plasma membrane made of phospholipids
- acquire and use ATP
- use nucleic acids for genetic material
examples of organisms’ ability to process information:
- the central dogma
- conversion of energy/ATP in response to changing information about their environment
cells are highly adapted to ________
fit specific niches. their environment and structure dictates their function
cells acquire and use energy in ________
response to changing information about their internal/external state (environment)
the most abundant elements found in organisms are:
Carbon, Hydrogen, Oxygen, and Nitrogen (CHON)
why are some elements so biochemically abundant?
all of these elements (CHON + a few others) have unpaired electrons ini their valence shells so they will readily bond with other elements to fill their valence shells. this makes them very reactive
carbon has a valence of ____ and likes to form ________
4; double bonds
hydrogen has a valence of ____
1
oxygen has a valence of ____
2
nitrogen has a valence of ____ and likes to form ________
3; triple bonds
biochemically important atoms readily form covelent bonds to _________
fill their valence shells and therefore achieve their most stable state
electronegativity:
the tendency of an atom to attract electrons
why is electronegativity important?
it dictates the type of bond formation based on the difference in electronegativity of 2 atoms
small EN difference
nonpolar covalent bond
medium EN difference
polar covalent bond
ex. ammonia, water
large EN difference
ionic bond
nonpolar covalent bond:
equal sharing of electron pairs between atoms
polar covalent bond:
unequal sharing of electron pairs between atoms due to electronegativity differences; partial charges exists but the total charge = 0
ionic bond:
unequal electron sharing; one atom “steals” electron pair(s) from another atoms. atoms have full charge
ex. NaCl
cation:
loss of electron(s), positive charge
anion:
gain of electron(s), negative charge
electronegativity scale for biological atoms:
O»_space; N > C ≈ H
covalent bond:
2 atoms share one or more pairs of electrons
bond type correlates to amount of ________ and ability for _________
potential energy; bonds to be broken
nonpolar covalent bond characteristics:
high potential energy, bond length is longer and strength is weaker —> easier to break apart (lower bond dissociation energy), high amount of energy released which can be used by cells.
why do most biological macromolecules have lots of nonpolar covalent bonds?
it allows for more energy/ATP to be acquired and used without lots of energy input to break the bonds
polar covalent bond characteristics:
low potential energy, bond length is shorter and strength is stronger —> harder to break apart (greater bond dissociation energy), low amount of energy released
gibb’s free energy
change in free energy associated with a chemical reaction
gibb’s free energy equation
∆G = ∆H - T∆S
if ∆G < 0 :
reaction is spontaneous and exergonic; can proceed without addition
if ∆G > 0 :
reaction is non-spontaneous and endergonic; needs addition of energy to occur
the spontaneity of a reaction is determined by _________ and _________
enthalpy; entropy
∆H
change in enthalpy; change in potential energy of the system
∆H is high
non polar bonds, high PE
∆H is low
polar bonds, low PE
∆S
change in entropy, change in disorder of the system
carbon is a ________ in all ________ molecules
crucial atom; biochemical
all biochemical molecules contain:
carbon-carbon bonds or a carbon backbone
what does the chemical evolution hypothesis propose?
complex organic molecules arose from simple organic molecules
issue with CO2 abundance
carbon in CO2 is not very reactive because of polar covalent bonds and needs to undergo a redox reaction to reduce carbon, making carbon more reactive
reduction
gain of electrons
oxidation
loss of electrons
what do redox reactions explain?
the possible interactions of carbon on early earth
what was the first step in chemical evolution?
reducing carbon. this allows for more complex organic molecules to form
what does reducing carbon do?
make it more reactive
two models for how chemical evolution occurred:
prebiotic soup model and surface metabolism model
what provided energy for carbon redox reactions to occur?
sunlight; it can break apart H2 and CO2 bonds and generate free radicals
pH:
measure of concentration of H+ ions in a solution
water has a pH of ____
7, neutral pH; concentration of H+ is 10^-7 M
acids
donate H+ ions during a chemical reaction, lower pH (pH < 7)
bases
take up H+ ions during a chemical reaction, higher pH (pH > 7)
H+ concentration increases/decreases by _________ every pH step
10-fold, pH scale is logarithmic
