Studied by 101 people
How do atoms fill their valence shell?
ionic bonds and covalent bonds
What happens when an atom loses or gains an electron?
it will become positively charged (cation), negatively charged (anion), or have a full outer shell
96% of living matter is composed of which elements?
Hydrogen, Oxygen, Nitrogen, Carbon
How can you distinguish one element from another (why is a carbon atom different from a nitrogen atom)?
the atomic number (atoms with the same atomic number belong to the same element)
What are isotopes?
different forms of the same element (with the same number of protons but a different number of neutrons)
How do isotopes of carbon differ from each other?
the amount of neutrons they contain (6, 7, or 8 neutrons)
What is a covalent bond?
2 atoms sharing an electron to fill both valence shells
What is a polar covalent bond?
a partial positive end and a partial negative end of a compound (electrons are shared unevenly)
What are electronegative elements?
elements with a negative charge
How do electronegative elements contribute to the formation of polar covalent bonds?
polar bonds are entirely formed through elements being electronegative; this causes electrons to be shared unequally
How do two atoms share a pair of electrons?
covalent bonds
What effect does two atoms sharing a pair of electrons have on their valence shells?
both valence shells are filled
How many electrons does it take to fill the valence shells of C, H, O and N?
C -- 4
H -- 7
O --2
N --3
Why are hydrogen bonds important for biological molecules? Can you give an example of a biological molecule that contains hydrogen bonds?
they hold elements together, examples are DNA and water
What does mass conservation law state?
all atoms present in the reactants are still present in the products
What does it mean when a reaction is “reversible”?
a reaction that can take place forward and backwards
Why is water a polar molecule?
Hydrogens are the positive end and the oxygen is slightly negative
What type of bonds do water molecules form with each other?
Hydrogen bonds
What are the properties of water?
Cohesion
High specific heat
High heat of vaporization
Low density of ice
Solubility
Hydrophobic exclusion
surface tension
What is cohesion?
(water) sticking together
What is surface tension?
measure of how hard it is to stretch/break the surface of a liquid
What is high specific heat?
amount of energy required to change 1g of a substance by 1 degree Celsius
What is heat of vaporization?
the amount of energy required to change 1g of a substance from a liquid to a gas
What is the density of water at various temperatures?
most dense in a liquid (4 degrees Celsius)
medium dense as a solid (ice)
least dense as a gas (hot)
Why does ice float?
the ice is lighter/less dense than the water
How do hydrophilic and hydrophobic compounds interact with water?
Hydrophilic compounds are attracted to water (polar)
Hydrophobic compounds resist water (non-polar)
What is concentration?
how much solute is present per volume of a solvent
What is a solute?
the substance that is dissolved
What is a solvent?
the dissolving agent of a solution
Why is water a good solvent?
its polarity allows it to be attracted to many molecules (positively or negatively charged)
What types of solutes dissolve in water (hydrophobic or hydrophilic)?
Hydrophilic
What pH range does an acidic, basic, or neutral solution have?
acidic -- less than 7
neutral -- 7
basic -- more than 7
What does pH have to do with H+ (hydrogen ion) concentration?
the greater the H+ the more acidic the solution
What is the formula used to calculate pH?
pH = −log ([H+])
What is the pH of pure water?
7
How many H+ are in pure water?
7
What is an organic molecule?
a chemical compound containing carbon
What are the advantages to using carbon as a building block for organic molecules?
carbon is tetravalent (needs 4 electrons to fill the valence shell) so it is capable of making 4 bonds (large, complex, diverse molecules)
Give examples of variations in the carbon skeleton
length; branching; double-bonds; ring structures
What is the difference between 1-butene and 2-butene?
1 & 2-butene vary in where the double bonds are (between carbons 1-2 and 2-3)
What is the difference between butane and isobutane?
same atomic composition but different structures and properties
What are the functional properties of side groups?
they change what each molecule can do
Which side groups can function as an acid or a base? Why?
The sulfonic, phosphoric, and carboxylic acid groups are the strongest acids. A functional group is an acid if it can donate a proton to a base.
What is an isomer?
atoms with the same atomic composition but different structures and properties
What are examples of structural isomers, cis-trans isomers, and enantiomers?
isomer: butane & isobutane
cis isomer: cis-2-butene (two substituents are on the same side of the double bond)
trans isomer: trans-2-butene (two substituents are on opposite sides of the double bond)
enantiomer: R- & S+ (ibuprofen)
What is the role of a dehydration synthesis reaction in the formation of a polymer?
take 1 H2O molecule out of a molecule to bring 2 together
What does the hydrolysis reaction do to a polymer?
Add 1 H2O molecule to separate 1 into 2 molecules
Glucose forms a ring structure. What are the atoms that make up the ring?
CH2N
What do you call two sugar monomers that are linked together?
disaccharide
What are the functions of polysaccharides?
energy storage and structural support
What are lipids?
nonpolar hydrophobic organic molecules that are insoluble in water but dissolve easily in nonpolar organic solvents (fats, oils, waxes, steroids)
What characteristic defines a lipid?
soluble in organic solvents and insoluble in polar solvents such as water
What are the components of a triglyceride (fat)?
glycerol and 3 fatty acids
What are the components of a phospholipid?
hydrophilic head and 2 hydrophobic tails
Why do phospholipid molecules spontaneously form bilayers in water?
the fatty acid tails are poorly soluble in water
What are saturated and unsaturated fats?
saturated: lack double bonds between the individual carbon atoms
unsaturated: there is at least one double bond in the fatty acid chain
How can saturated and unsaturated fats be distinguished at room temperature?
saturated: solid at room temp
unsaturated: liquid at room temp
What is the chemical structure of an Amino Acid?
an amino group, a carboxyl group, an R group/side chain
The 20 essential amino acids are classified as being non-polar, polar, and electrically charged. What does that mean?
depending on the R group/side chain
What is a peptide bond?
bonds that link individual amino acids (via dehydration synthesis)
What is a dehydration synthesis reaction?
taking out one H2O to combine 2 molecules
What determines the shape of a protein?
the amino acid sequence
What is primary, secondary, tertiary and quaternary structure?
1: string of pearls
2: coil/folds
3: 3D structure
4: braiding
How is the 3-D shape of a protein stabilized?
hydrogen bonds, disulfide bridges, and ionic bonds
What are hydrogen bonds, disulfide bridges, and ionic bonds?
H: 2nd level
D: 3rd & 4th levels
I: 3rd level
What is protein denaturation (think about egg whites in a skillet)?
its normal shape gets deformed because some H bonds are broken
Is a denatured protein still functional? Why or why not?
No - it lost its shape
What are some examples of protein functions?
enzymes, antibodies, structural (collagen), contractile (make things contract), transport, cell communication
What are the components of a nucleotide?
sugar molecule, phosphate group, nitrogen-containing base
How are nucleotides arranged to form DNA or RNA?
A-T and C-G
Which part of the molecule is the “backbone”?
phosphates
What are the differences between DNA and RNA?
DNA directs synthesis of messenger RNA (mRNA) and through mRNA controls protein synthesis
What are deoxyribose and ribose?
with/out 1 oxygen molecule
What rules govern base pairing?
A pairs with T, C pairs with G
DNA strands are described as being “complementary” and “anti-parallel”. What does that mean?
complementary: balanced (AT + CG)
anti-parallel: same direction but counter to one another
What are the differences between prokaryotic and eukaryotic cells?
prokaryote: smaller, unicellular
eukaryote: larger, uni or multicellular, has organelles
Why are eukaryotic cells compartmentalized?
there are many specialized cell compartments
What is the advantage of compartmentalization?
increased division of labor
What is the structure of the nuclear envelope?
phospholipid bilayer surrounding the nucleus
What are nuclear pore complexes?
connects nucleus to cytoplasm and serves as a passage between the two
What is the function of ribosomes? Where are they located?
carry out protein synthesis; on the RER and freely in the cytosol
What is rough and smooth endoplasmic reticulum?
RER: studded with ribosomes - protein synthesis
SER: no ribosomes - manufacturing and detoxifying the cell
Which classes of molecules are synthesized in the rough and the smooth endoplasmic reticulum?
RER: proteins
SER: lipids and steroids
What is the structure and function of the Golgi apparatus?
stacks of flattened membrane sacs that modify proteins then tell them where to go
Where do proteins go from the Golgi apparatus?
plasma membrane, secretion (outside the cell), lysosomes/vacuoles
How are cell contents moved from one location to another (i.e. from ER to Golgi)?
transport vesicles
What is the function of lysosomes and vacuoles?
digest food particles & damaged organelles; sturdiness and storage of the plant
Why are lysosome contents separated from the cytoplasm?
so the lysosome contents don’t digest the whole cell and end up killing it
What is the endomembrane system in cells?
the system of interconnected membranes within the cell that tells things where to go & transports them
Which organelles are not part of the endomembrane system?
mitochondria, chloroplasts, peroxisomes
What is the structure and function of mitochondria?
smooth outer membrane with inner membrane folds/cristae, chemical energy conversion
What is the structure and function of chloroplasts?
thylakoid discs within a membrane, capture light energy to perform photosynthesis
What is the endosymbiont theory?
that all eukaryotic cells evolved from free living prokaryotes
What are the different types of cytoskeletal fibers and where are they found?
actin filaments, microtubules, intermediate filaments; found within the cytoskeleton
What are the functions of the various cytoskeletal fibers?
microtubule: support, transport, and mobility
intermediate filament: cell strength and support
actin filament: cell movement
What is the extracellular matrix in animal cells?
composed of 3 glycoproteins (collagen, elastin, fibronectin) that give cells strength and support
What is the cell wall in plant cells?
the rigid, outermost layer of plant cells, surrounds the cytoplasm
What are the various types of contact points between cells? How do they differ functionally?
plasmodesmata: openings in the cell wall that help with cell-cell communication
gap junctions: between adjacent animal cells, allows for the passage of materials between cells
tight junctions: watertight seal between two adjacent animal cells
desmosomes: anchoring junction that links adjacent cells by connecting their cytoskeletons
What is a non-polar covalent bond?
equal sharing of electrons so identical atoms exist
