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Biochemistry > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Which pair of amino acids has two chiral centers?
Leu and lle
Ser and Thr
Gly and Pro
lle and Thr
Pro and Val

A

lle and Thr

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2
Q

Why is cellulose not a source of nutrients for humans?

A

Vertebrate enzymes are unable to hydrolyze (beta 1 –> 4) linked glucose monomers

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3
Q

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.

A

G-C pairs share 3 hydrogen bonds.

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4
Q

Mark all aromatic amino acids from the list below:
Cysteine.
Phenylalanine.
Tyrosine.
Threonine.
Serine.
Tryptophan.
Methionine.

A

Phenylalanine.
Tyrosine.
Tryptophan.

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5
Q

Which amino acids of the portion of the polypeptide AIGHTSM will be hydrogen-bonded to each other in the alpha helix?

A

A-T, I-S, G-M

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6
Q

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.

A

lle-Ala-Ala.

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7
Q

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.

A

Isoleucine, Alanine, Valine

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8
Q

How many hydrogen bonds exist between this DNA strand and its complementary strand?
5’-CTTAG-3’

A

12

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9
Q

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.

A

Alternating phosphate groups and pentose residues.

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10
Q

Angstrom equals:
10^-9 m.
10^-7 m.
10^-10 m.
10^-10 cm.
10^-3 m.

A

10^-10 m

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11
Q

Which deoxyoligonucleotide complements a DNA sequence (5’) AGACTGGTC (3’)?

A

(5’) GACCAGTCT (3’)

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12
Q

What is the correct description of starch?

A

Mixture of 2 polymers of alpha-glucose: unbranched amylose and branched amylopectin.

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13
Q

Palmitate has how many carbons in its chain?

A

16

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14
Q

Which carbon atoms are involved in the cycle formation of alpha-D-fructofuranose?

A

C-2 keto group and C-5 hydroxyl group.

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15
Q

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.

A

Hydrogen bonds are covalent bonds between Hydrogen and Oxygen in a water molecule.

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16
Q

Which term best describes the polarity of triacylglycerols?

A

Nonpolar

17
Q

Estimate the net-charge of the peptide at pH 2.0:
Ala-Glu-Pro-lle-Val-Asn-Pro-Met-Glu-Tyr-Gly-Arg

A

+2

18
Q

An amino acid in a medium with a pH below its isoelectric point would have ____.

A

A net positive charge

19
Q

What is the [A-]/[HA] ratio when the weak acid is in a solution one pH unit above its pKa?

A

10:1

20
Q

The longer the fatty acid, the ____ fatty acid.

A

Higher the melting point of

21
Q

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?

A

At pH’s between 9 and 10

22
Q

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

A

Carbon and Nitrogen

23
Q

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.

A

Hydrogen bonds form readily in aqueous solutions.

24
Q

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

a million times lower than that of the gastric juice

25
Q

What functional groups of amino acids are linked in the primary sequence?

A

Alpha-amino group and alpha-carboxyl group.

26
Q

Citric acid has 3 carboxyl groups. The pKa value for each of them are 3.1, 4.8, and 6.4. What would be the charge on a citrate molecule in the solution with the pH 1.5?

A

0

27
Q

What amino acid does not have free alpha-amino group?
Histidine.
Isoleucine.
Tryptophan.
Glycine.
Proline.

A

Proline

28
Q

The compound that consists of deoxyribose bound by an beta-N-glycosidic bond to N-9 of adenine is ____.

A

Deoxyadenosine

29
Q

Calculate the pI of asparagine using the given values:
pKa (-COOH) = 2.02
pKa (-NH2) = 8.8

A

5.41

30
Q

A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro-Gly-. This sequence is most probably part of a(n) ____.

A

beta-turn

31
Q

Rank cell components from smallest to largest.
Proton
Amino acid
Ribosome
Water molecule
Cell nucleus
Mitochondrion
Protein

A
  1. Proton
  2. Water molecule
  3. Amino acid
  4. Protein
  5. Ribosome
  6. Mitochondrion
  7. Cell nucleus
32
Q

The pKa of acetic acid is 4.76. The pKa of trichloroacetic acid is 0.7. Acetic acid is a stronger acid.
True or false?

A

False.

33
Q

What is not true about prokaryotes?
Prokaryotes have cell wall.
Prokaryotes are usually less than 2 um in size.
Prokaryotes have DNA.
Prokaryotes have plasma membrane.
Prokaryotes contain mitochondria.

A

Prokaryotes contain mitochondria.

34
Q

Select a monosaccharide that is incorrectly paired with its class.
Dihydroxyacetone: triose ketose.
Fructose: hexose ketose.
Ribose: hexose aldose.
Glyceraldehyde: triose aldose.

A

Ribose: hexose aldose.

35
Q

Once formed, the alpha- and beta-forms of glucose are

A

Interconvertible only through a linear, noncyclic intermediate with which they are both in equilibrium.

36
Q

List the sizes of each object:
Ribosome
Bacterial cell (E. coli)
Cell nucleus
Skin cell
Glucose molecule in the ring form

A

Ribosome: 30 nm.
Bacterial cell (E. coli): 2 um.
Cell nucleus: 10 um.
Skin cell: 30 um.
Glucose molecule in the ring form: 1 nm.

Biochemistry (18 decks)

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