Suppose that multiple newly created amino acids interact to build a small protein molecule. The primary structure of that protein is formed when:
- primary structure of polypeptide is the order in which amino acids are connected to one another
- peptide bonds occur when the lone pair of electrons on one amino-acid terminus attack the carbonyl carbon of another amino acid’s carboxy terminus
A: the amino terminus of one amino acids attacks the carboxyl terminus of another
Experimenters isolate a biological sample believed to be composed entirely of glycine. In order to confirm their belief, they can hydrolyze the peptide and then:
A: use polarized light in order to determine whether or not the sample is optically active
-glycine is the only amino acid with no chiral center, therefore a sample of pure glycine will not be optically active
Atomic oxygen is extremely reactive and not found in any significant quantity on Earth’s surface because:
A: it is a free radical
Atomic Oxygen has 8 electrons, 2 inner and 6 valence
1s^2 2s^2 2p^4
- there are unpaired valence electrons in the p orbital, these are known as free radicals
-free radicals are extremely chemically reactive
What does an electrophile do
Donates protons and accepts electrons
Lewis acid
What does a nucleophile do
accepts protons and donates electrons
Lewis base
Which of the following will increase the yield of carboxylic acid from a nitrile group-containing compound, using a mechanism similar to the Strecker synthesis?
A: attach an electron withdrawing group to the carbon of the nitrile group
- if we attach another electron-withdrawing group to the carbon, that carbon will be even more electron deficient and act as a better electrophile, increasing the yield of carboxylic acid
The index of refraction of vitreous humor is greater than the index of refraction of aqueous humor, which is greater than the index of refraction of air. How does the speed of light in each of these media compare?
A: fastest in air, slower in aqueous humor, slowest in vitreous humor
- material with the LOWEST index of refraction will enable light to travel through it at the fastest speed
- increasing indices of refraction = decreasing order of speed of light in the media
What is true of the image formed by the retina
- it is real: the image is real if the object is placed outside the focal length
- it is reduced in size: the retina is about the size of a postage stamp, so if you are able to view an object larger than a postage stamp, the image must be reduced
- it is inverted: any real image formed by a converging lens is inverted
Which of the following accurately describes the difference between alpha-D-glucose and beta-D-glucose?
A: the hemiacetal carbons of alpha-D-glucose and beta-D-glucose have opposite absolute configurations
- they are a pair of two anomers
- anoers differ only in the absolute configuration at the anomeric carbon
- anomeric carbon is the carbon at the center of a hemiacetal group whose configuration will determine whether the -OH is axial or equatorial
When blood is donated, it is important that no active active antibodies are transferred along with the red blood cells. IN order to accomplish this, a reducing agent, which breaks the disulfide bonds that maintain the quaternary structure of antibodies, is added to donate blood. This is effective because:
A: when cystine accepts electrons, it separates into two cysteine groups that are located on separate polypeptides
- disulfide bonds maintain quaternary structure of antibodies
- disulfide bonds are covalent bonds between two thiol groups (R-SH)
- reducing agent will break disulfide bonds
- in proteins, disulfide bonds occur between two cysteine amino acids to form a single unit
- reducing means GAINING ELECTRONS
When an acyl halide reacts with a primary alcohol, which of the following will form?
A: an ester
- carbon of the acyl acts as an electrophile (accepts electrons) from the alcohol since it has lone pairs of electrons
- electrons reform a double bond kicking off the halide
- oxygen from the alcohol group loses its proton (and positive charge) and we are left with an ester
what complex carbohydrates contains multiple 5 or 6-carbon rings?
polysaccharides
nulceotides
what complex carbohydrates contain alcohol functional groups?
all polysaccharides and more
both nucleotides
and most polypeptides (ones with -OH containing R-groups)
what complex carbohydrates contain branched chains?
polysaccharides CAN contain branched chains, but not necessary
how are disaccharides formed
the attack of the anomeric carbon’s OH group on one cyclic monosaccharide by an alcohol from another monosaccharide will lead to a glycosidic bond
where will glycosidic linkage form with disaccharides?
- most commonly b/w C-1 (anomeric carbon) of the first sugar and C-4 of the second sugar
- called 1-4 glycosidic linkage
How do you transfer from the fischer diagram to the haworth projections? How do you know what points up and what points down?
Downright
Uplefting!
D sugar - points up
pyranose
6 membered carbohydrate rings
maltose
made of 2 pyranoses (6 membered ring)
- made of 2 glucose rings
- reducing sugar (along with lactose) because they have a hemiacetal that can be reduced to an acetal
sucrose
1 six membered ring (glucose)
1 five membered ring (fructose)
linked together by their anomeric carbons
-non reducing sugar because it already has an acetal
polysaccharides
can be made from reducing sugars
ex: cellulose (made of repeating glucose connected by beta 1,4-glycosidic linkages
ex: starch (repeating glucose connected by alpha 1,4-glycosidic linkages)
what makes up the atomic mass
protons + neutrons
How do we find the number of protons?
look at the atomic number!
What does a catalyst do?
- accelerates a reaction by lowering one or more of the activation energies of the reaction
- does NOT change the deltaH of the reaction (state function)
