Exam 1 Flashcards
(36 cards)
Which pair of amino acids has two chiral centers?
Leu and lle
Ser and Thr
Gly and Pro
lle and Thr
Pro and Val
lle and Thr
Why is cellulose not a source of nutrients for humans?
Vertebrate enzymes are unable to hydrolyze (beta 1 –> 4) linked glucose monomers
Which of the following is true for DNA?
G-C pairs share 3 hydrogen bonds.
The ratio of A+T and G+C is constant for all naturally occurring DNA.
Deoxyribose units are connected by 3’,5’-phosphoanhydride bonds.
Phosphate groups project toward the middle of the double helix.
The 5’ ends of both strands are at the same end of double helix.
G-C pairs share 3 hydrogen bonds.
Mark all aromatic amino acids from the list below:
Cysteine.
Phenylalanine.
Tyrosine.
Threonine.
Serine.
Tryptophan.
Methionine.
Phenylalanine.
Tyrosine.
Tryptophan.
Which amino acids of the portion of the polypeptide AIGHTSM will be hydrogen-bonded to each other in the alpha helix?
A-T, I-S, G-M
Which of the following peptides will have a net charge 0 at neutral pH?
Arg-Ala-Arg.
Gly-Arg-Tyr.
Pro-Lys-Lys.
lle-Ala-Ala.
Ala-Glu-Glu.
lle-Ala-Ala.
Which group of amino acids would be MOST likely to be found in the core of protein that is folded into a 3-dimensional structure and soluble in water?
Asparagine, Tyrosine, Lysine.
Isoleucine, Alanine, Valine.
Phenylalanine, Tyrosine, Tryptophan.
Valine, Threonine, Arginine.
Methionine, Serine, Tyrosine.
Isoleucine, Alanine, Valine
How many hydrogen bonds exist between this DNA strand and its complementary strand?
5’-CTTAG-3’
12
The backbone of DNA and RNA consists of :
Alternating phosphate groups and nitrogenous bases.
Alternating phosphate groups and hexose residues.
Alternating pentose residues and nitrogenous bases.
Alternating phosphate groups and pentose residues.
Alternating pentose residues and cyclic nucleosides.
Alternating phosphate groups and pentose residues.
Angstrom equals:
10^-9 m.
10^-7 m.
10^-10 m.
10^-10 cm.
10^-3 m.
10^-10 m
Which deoxyoligonucleotide complements a DNA sequence (5’) AGACTGGTC (3’)?
(5’) GACCAGTCT (3’)
What is the correct description of starch?
Mixture of 2 polymers of alpha-glucose: unbranched amylose and branched amylopectin.
Palmitate has how many carbons in its chain?
16
Which carbon atoms are involved in the cycle formation of alpha-D-fructofuranose?
C-2 keto group and C-5 hydroxyl group.
What statement about hydrogen bonds is false?
Hydrogen bonds are covalent bonds between Hydrogen and Oxygen in a water molecule.
The hydrogen bond is an interaction always including a hydrogen atom bound to a more electronegative atom.
Hydrogen bonds are weaker than covalent bonds.
Hydrogen bonds stabilize secondary, tertiary, and quaternary structure of proteins.
Hydrogen bonds are covalent bonds between Hydrogen and Oxygen in a water molecule.
Which term best describes the polarity of triacylglycerols?
Nonpolar
Estimate the net-charge of the peptide at pH 2.0:
Ala-Glu-Pro-lle-Val-Asn-Pro-Met-Glu-Tyr-Gly-Arg
+2
An amino acid in a medium with a pH below its isoelectric point would have ____.
A net positive charge
What is the [A-]/[HA] ratio when the weak acid is in a solution one pH unit above its pKa?
10:1
The longer the fatty acid, the ____ fatty acid.
Higher the melting point of
Tyrosine has 3 ionizable groups with pKa(-COOH) = 2.2; pKa (-NH3+) = 9.11; and pKa (-R) = 10.07. In which pH ranges will this amino acid have the greatest buffering capacity?
At pH’s between 9 and 10
Of the elements below, 2 are more abundant in living organisms than in earth’s crust. What are these two elements?
Silicon
Iron
Calcium
Carbon
Nitrogen
Carbon and Nitrogen
Which of the following is true about the properties of aqueous solutions?
Hydrogen bonds form readily in aqueous solutions.
A pH change from 5.0 to 6.0 reflects an increase in the hydroxide ion concentration ([OH-]) of 20%.
A pH change from 8.0 to 6.0 reflects a decrease in the proton concentration ([H+]) by a factor of 100.
Charged molecules are generally insoluble in water.
The pH can be calculated by adding 7 to the value of the pOH.
Hydrogen bonds form readily in aqueous solutions.
The pH of a sample of blood is 7.4; the pH of a sample of gastric juice is 1.4. The blood sample has an [H+]:
a million times lower than that of the gastric juice
