ACMB exam 1

Until the late nineteenth century, what was the name of the 'vital force' believed to distinguish living things from nonliving matter?

aminus

What are the four primary characteristics that distinguish the 'special' chemistry of life from standard inorganic chemistry?

1) must be carbon based

2) depends on aqueous reactions

3) is very complex

4) dominated by polymers

why are chemical reactions considered tightly regualted?

cells use complicated and diverse mechanisms to ensure reactions occur at the specified rate time and place

what physical feature of an atom determines its atomic number

the number of protons in its nucleus

what is the specific electrical relationship between a proton and an electron

they carry equal but opposite charges

why do we depict electrons in an atom as clouds rather than a distinct path?

the exact position of an electron cannot be predicted at any given moment

how are isotopes distinguished from one another

they carry equal protons but different amounts of neutrons

what particle is responsible for the structural stability of the nucleus over its chemical reactivity

neutrons

what is the defining mass of 1 dalton in relatio nto a carbon atom

it has 1/12 of the mass of a single carbon atom

why do electrons contribute so little to the total atomic mass

they are much lighter than protons and neutrons

what does avogadro’s number represent

the number of particles in one mole of a substance

if an atom has a mass of X daltons, what is the mass in g of one mole of that atom

X grams

what 4 elements constitute 96% of an organism’s total mass

carbon, hydrogen, nitrogen and oxygen

which shell in an atom can hold max two electrons

first shell, n=1

what is the maximum electron capacity in the second and third electron shells

8 electrons

what state of the outermost electron shell renders an atom chemically unreactive

completely full outer shell

with regards to electron behavior, how is a covalent bond distinguished from an ionic bond

covalent bonds share electrons, ionic bonds transfer them

how many covalent bonds can a carbon atom typically form?

four (8 electrons total)

what term is used to describe the specific distance between 2 nuclei where attractive and repulsive forces are precisely balanced in a covalent bond

bond length

why are double bonds less flexible compared to a single bond?

a double bond leads to rotation of one part of the molecule being restricted relative to the other around the bond axis

what 3 dimensional geometry is formed by the four covalent bonds of the carbon atom

a regular tetrahedron

what is electronegativity

the tendency of an atom to attract shared electrons in a chemical bond

why is a C-H bond nonpolar compared to an O-H bond

C and H have similar electronegativities, where O and H have more different ones

what standardized unit is used to measure how much energy is required to break a chemical bond?

kJ/mole or kcal/mole

what is the difference in strength between covalent bonds and molecular collisions in a cell?

covalent bonds are roughly 100 times stronger

is there a certain catalyst used to break covalent bonds in a controlled cell environment, and if so what is it?

enzymes

what is formed when a sodium atom donates an electron to a chlorine atom

an ionic bond, and two electrically charged ions, Na+ and Cl-

are ionic bonds stronger inside a cell or in a vaccum

vaccum

why are ionic bonds weaker inside a cell compared to in a vacuum?

water molecules present interfere with electrostatic attractions between ions

what physically occurs for a hydrogen bond to form between two water molecules

an electrical attraction between a partial + charge on a hydrogen atom and a partial - charge on an oxygen atom

how are substances that contain polar bonds classified?

hydrophillic

how are substances with non-polar bonds classified

why do hydrophobic molecules fail to dissolve in water

they are uncharged and cant form hydrogen bonds with the water molecules

what are van der waals forces?

a weak interaction between two atoms due to fluctuations in the distribution of electrons

how do hydrophobic forces contribute to the formation of cell membranes

it forces lipid tails/hydrophobic tails together, pushing them out of the water’s hydrogen-bonded network

what happens when a water molecule accepts a proton from an acid

hydronium (H3O+)

what is different in a strong and weak acid

strong acids completely dissociate in water, weak acids do not

what is the concentration of hydronium in pure water at a neutral pH

10^-7 M

how does adding a base to an aq soln increase the concentration of hydroxyl ions (OH-)

by removing a proton from a water molecule

what is a chemical base that is commonly found within a call in weak bases

an amino group (-NH2)

how does a buffer maintain a constant pH in a cell?

they contain weak acids or bases that can normalize pH by accepting or relasing protons into the cell

what is the general chemical formula for a monosaccharide?

(CH₂O)_n

what is the term for compounds that have the same formula but different shapes?

isomers

what is an optical isomer

pairs of molecules that are mirror images of each other

what is the term for a reaction that joins two monosaccharides and forms a disaccharide? and what does it expel?

condensation, water

what is the term for a reaction that breaks a polysaccharide into a monosaccharide and what does it consumer?

hydrolysis, water

what is glycogen and what does it serve as?

a glucose polysaccharide, long term energy storage

what is cellulose?

the most abundant organic molecule on earth, and the primary structural component of plant cell walls

what are glycoproteins and glycolipids?

small sugar polymers/lipids in the plasma membrane

what does it mean to describe a molecule as amphipathic

it possesses both a hydrophobic and hydrophilic region

what is different between saturated and unsaturated fatty acids, and how does this affect their functioning?

unsaturated fatty acids have a double bond which makes them kink. this causes the membrane to be less rigid, and increases membrane fluidity

what are triacylglycerols?

the storage form of fatty acids in the cytosol, which consist of three fatty acid chains joined to glycerol

what group replaces the third fatty acid chain found in triacylglycerols in a phospholipid

a hydrophilic phosphate group

what are the main components attached to the central alpha carbon of every amino acid?

an amino group (NH₂), a carboxyl group (COOH), and a side chain (R)

what does a peptide bond do?

it is a covalent bond that links amino acids together in a polypeptide chain

what direction is the sequence of a polypeptide chain read in?

from the N-terminus (amino end) to the C-terminus (carboxyl end)

how many different types of amino acids are commonly found in proteins

20

which optical isomer form of amino acids is exclusively used by cells to construct proteins

the L form

what three components make up nucleotides

nitrogen-containing base, five carbon sugar, phosphate group

what is the difference in the sugar in RNA and DNA

RNA contains ribose, DNA contains deoxyribose. deoxyribose lacks an -OH group at the 2’ positon

which nitrogenous bases are pyrimidines, and what makes them different?

Cytosine, thymine and uracil. they have a 6 membered ring

which nitrogenous bases are purines, and what makes them distinct?

guanine and adenine, they have a fused five and six membered ring structure

what is ATP classified as and what does it do in cells?

a ribonucleoside triphosphate, short term energy carrier

what type of bond links nucleotides together in a nucleic acid chain

phosphodiester bonds

what macromolecule class makes up the greatest amount of a cells dry mass?

protein

how does stepwise polymerization of monomers lead to the production of complex macromolecules?

it uses a single repetitive reaction catalyzed by a set of specific enzymes to build a large molecule

what forces decide the folding and final conformation of a protein macromolecule

weak noncovalent forces. electrostatic, hydrogen, van der Waals and hydrophobic forces

why is the specificity of macromolecule binding dependent on noncovalent interactions over covalent ones?

noncovalent bonds are more transient and reversible, and allow for specific multipoint contacts that require complementary surfaces

what did theodore sveldberg discover in 1926

he discovered that proteins like hemoglobin are discrete macromolecules or uniform size rather than random aggregates. he discovered this using an unltracentrifuge

what is the significance of 10^-14 (moles/liter)²?

it is the concentration of OH- and H+ of any aqueous solution

what type of amino acids are typically found on the surface of an enzyme and what do they assist with?

negatively charged amino acids, they help it attract a positively charged substrate

what is the primary role of DNA vs RNA

DNA serves as a long term archive of instructions, while RNA is more transient and serves as a go-between for DNA to protien

what is the relationship of bond energy and strength in a chemical bond?

it is the amount of energy that must be supplied to break the bond

what are the subunits of chitin, and where is it found?

N-acetylglucosamine, and it is a structural polysaccharide found in insect exoskeletons

how can the sequence of subunits in a macromolecule be described?

non-random

how can one mole of sodium ions and one mole of chloride ions have different masses?

they have a different numbers of protons, and thus different atomic masses

which radioactive isotope of carbon is typically used for dating organic materials?

¹⁴C

how many electrons are shared in a carbon-carbon double bond

four

what is a cation

a positively charged ion that is formed by losing one or more electrons

what is an anion?

a negatively charged ion that is formed by gaining one or more elctrons

how can a protein lose its biological activity?

it can be denatured/unfolded, which disrupts its noncovalent bonds

what is the backbone of a nucleic acid chain

alternating sugars and phosphate groups

what are the four characteristics shared by all living cells

organization, homeostasis, reproduction, growth/development

what is transcription

synthesis of RNA from a DNA template

what is translation

synthesis of protein from an RNA template

is RNA or DNA more stable

DNA

what is the theoretical resolution limit of a conventional light microscope

0.2μm (or 200nm)

why is the resolution of a light microscope limited to .2um

it is due to the wavelike nature of light

what are the three requirements for viewing a specimen under a light microscope

bright light source, transparent specimen, lenses

what lens in a light microscope is responsible for focusing light

condenser

how do phase and interference contrast systems exploit differences to visualize living cells?

they detect changes in how light travels through regions with differing refractive indices

what is fixation?

the process of chemically treating and slicing tissues

in fluorescence microscopy how is the emitted light wavelength different from the absorbed wavelength?

the emitted light has a longer wavelength

what is the purpose if the second set of filters in fluorescence microscopy

blocking the excitation light and passing only those wavelengths emitted by the dye

what is special about confocal fluorescence microscopy

it builds a 3d image by scanning the specimen with a laser beam using a pinhole aperture

what is the resolution limit for a transmission electron microscope

1 nm

what is used to stain specimens in TEM

electron dense heavy metals

what type of microscopy is used to create 3d images of the surface of a specimen

scanning electron microscopy

what is the resolution range for SEM

3nm and 20nm

what microscopy technique is required to see objects as small as .2nm

electron microscopy