exam 1 practice test

Which of the following statements is true? (a) Peptide bonds are the only covalent bonds that can link together two amino acids in proteins. (b) Each amino acid in a polypeptide is connected through phosphodiester bond. (c) Nonpolar amino acids tend to be found in the interior of proteins. (d) The sequence of the atoms in the polypeptide backbone varies between different proteins.

(c) Nonpolar amino acids tend to be found in the interior of proteins.

Which of the following amino acids can form a disulfide bond? (a) D (b) W (c) R (d) C (e) S

(d) C

Proteins that form a beta-barrel pore in the membrane have several beta-strands that span the membrane. The pore-facing side of each strand carries hydrophilic amino acid sided chains, whereas the bilayer-facing sides carry hydrophobic amino acid side chains. Which of the three 10-amino acid sequences listed below is the most likely candidates for a transmembrane beta-strand in a beta-barrel pore? (a) A D F K L S V E L T (b) A F L V L D K S E T (c) A F D K L V S E L T (d) K D R H E E S T R D

(a) A D F K L S V E L T

Which of the following affects the mobility of a protein in SDS-PAGE? (a) Number of total amino acids (b) Number of amino acids with charged side chain (c) Percentage of hydrophobic amino acids (d) Number of Glycine

(a) Number of total amino acids

Steady state is where the rate of ES breakdown is the same as the Rate of ES formation: k1 kcat E+S <-------> ES ---------> E+P k-1 Which of the following equations is correctly describing the rate of ES formation? (a) k1[E][S] (b) k1[ES] (c) k-1[ES] - kcat[ES] (d) k-1[ES] + kcat[ES]

(a) k1[E][S]

______ is the most abundant element on the earth's crust. (a) oxygen (b) potassium (c) hydrogen (d) carbon

(a) oxygen

Which of the following expressions accurately describes the calculation of pH? (a) pH=-log10[H+] (b) pH=log10[H+] (c) pH=-log2[H+] (d) pH= -log10[OH-]

(a) pH=-log10[H+]

Which of the following is a feature commonly observed in alpha-helices? (a) right-handedness (b) one helical turn every 7.2 amino acids (c) cone shape (d) amino acid side chains that point inwards

(a) right-handedness

Which of the following statements is false? (a) ATP is sometimes called the "universal currency" in the energy economy of cells. (b) ATP can be in corporate into DNA (c) ATP can be hydrolyzed to release energy to power hundreds of reactions in cells (d) ATP comprises a sugar, phosphate groups, and a nitrogenous base

(b) ATP can be in corporate into DNA

Which of the following amino acids has positively charred side chain under neutral pH? (a) P (b) W (c) E (d) A (e) M

(b) K

Which of the following amino acids has a hydrophobic side chain? (a) F (b) W (c) V (d) T (e) I

(b) W

Enzymes catalyze chemical reactions by lowering the _________, because they provide conditions favorable for the formation of a high-energy intermediate state. Once the reaction is completed, the enzyme releases the products of the reaction. (a) steady state (b) activation energy (c) Vmax (d) Km

(b) activation energy

Two monosaccharides can form a disaccharide by ______ reaction. (a) hydrolysis (b) condensation (c) esterification (d) polymerization

(b) condensation

You wish to explore how mutations in specific genes affecting sugar metabolism might alter tooth development. Which organism is likely to provide the best model system for your studies, and why? (a) horses (b) mice (c) E. coli (d) Arabidopsis

(b) mice

The ________, an organelle found in eukaryotic cells, confines the chromosomes, keeping them separated from other components of the cell. (a) lysosomes (b) nucleus (c) peroxisomes (d) ribosomes

(b) nucleus

The side chain of amino acid S is (a) negatively charged (b) polar (c) positively charged (d) ably to form disulfide bond

(b) polar

The phosphorylation of a protein is typically associated with a change in activity, the assembly of a protein complex, or the triggering of a downstream signaling cascade. The addition of ubiquitin, a small polypeptide, is another type of covalent modification that can affect the protein function. Ubiquitylation often results in _________. (a) membrane association (b) protein degradation (c) protein secretion (d) nuclear translocation

(b) protein degradation

Which of the following is a feature commonly observed in beta-helices? (a) antiparallel regions (b) coiled-coil patterns (c) extended polypeptide backbone (d) parallel regions

(bO coiled-coil patterns

Figure shown below is the initial rates of product formation at various substrate concentrations. What is the Km (microM)? (a) 0.5 (b) -1.0 (c) 1.0 (d) 2.0

(c) 1.0

Amino acid D has a pK of 4.7. What is the ratio of [D-]/[D] at pH 5.7? (a) 0.1 (b) 1 (c) 10 (d) 100

(c) 10

Which of the following amino acids has negatively charred side chain under neutral pH? (a) P (b) W (c) E (d) A (e) M

(c) E

________ is a signal for protein destruction. (a) Acetylation (b) Phosphorylation (c) Ubiquitination

(c) Ubiquitination

___________ is a covalent bond that is important in the folding and three-dimensional shape of an antibody. (a) A hydrogen bond (b) The van der Waals force (c) A disulfide bridge (d) The hydrophobic interaction (e) An ionic bond

(c) disulfide bridge

____ is the most abundant element in a human body. (a) oxygen (b) potassium (c) hydrogen (d) carbon

(c) hydrogen

If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B? (a) kon/koff = K (b) K = [A][B]/[AB] (c) K = [AB]/[A][B] (d) (a) and (c)

(d) (a) and (c)

Figure shown below is the initial rates of product formation at various substrate concentrations. What is the Vmax (micro mol/min)? (a) 0.5 (b) -1.0 (c) 1.0 (d) 2.0

(d) 2.0

The Ras protein is a GTPase that functions in many growth-factor signaling pathways. In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bounds, the signal is not transmitted. Mutations in the gene for Ras are found in many cancers. Of the choices below, which alteration of Ras activity is most likel to contribute to the uncontrolled growth of cancer cells? (a) A mutation that increases the affinity of Ras for GDP. (b) A mutation that decreases the affinity of Ras for GTP. (C) A mutation that decreases the affinity of Ras for its downstream targets. (d) A mutation that decreases the rate of hydrolysis of GTP by Ras.

(d) A mutation that decreases the rate of hydrolysis of GTP by Ras.

_________ is the organelle physically connected to the nucleus. (a) mitochondria (b) peroxisome (c) Golgi complex (d) Endoplasmic Reticulum

(d) Endoplasmic Reticulum

Which of the following amino acids has a polar side chain? (a) F (b) W (c) V (d) T (e) I

(d) T

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term "protein domain." (a) a small cluster of alpha-helices and beta-sheets (b) the tertiary structure of a substrate-binding pocket (c) a complex of more than one polypeptide chain (d) a part of a protein that folds independently

(d) a part of a protein that folds independently

The side chain of amino acid C is (a) negatively charged (b) polar (c) positively charged (d) ably to form disulfide bond

(d) ably to form disulfide bond

The side chain of amino acid Y is (a) negatively charged (b) polar (c) positively charged (d) ably to form disulfide bond

(d) ably to form disulfide bond

Steady state is where the rate of ES breakdown is the same as the Rate of ES formation: k1 kcat E+S <-------> ES ---------> E+P k-1 Which of the following equations is correctly describing the rate of ES breakdown? (a) k1[E][S] (b) k1[ES] (c) k-1[ES] - kcat[ES] (d) k-1[ES] + kcat[ES]

(d) k-1[ES] + kcat[ES]

The side chain of amino acid N is (a) negatively charged (b) hydrophobic (c) positively charged (d) polar

(d) polar

Cytoplasm is overwhelmingly __________ environment. (a) acidic (b) basic (c) oxidizing (d) reducing

(d) reducing

Src and All are two of the well characterized ________. (a) GEF (b) GAP (c) channel (d) tyrosine kinase

(d) tyrosine kinase

Which of the following bond (or interaction) displays solvent-independent, constant bond-strength? (a) H-bond (b) hydrophobic (c) ionic bond (d) van der Waals

(d) van der Waals

T/F: Disulfide bond is one of the covalent bonds between carbohydrates.

False

T/F: GTPases dephosphorylate phospho-tyrosine.

False

T/F: Hydrogen bind is one of the covalent bonds between proteins.

False

T/F: Kinases can phosphorylate a protein on the side chain of amino acid C.

False

T/F: Peptide bond is one of the non-covalent interactions (or bonds) between nucleic acids.

False

T/F: Post-translational modification is a process of generating mRNA.

False

T/F: Replication is a process of generating mRNA.

False

T/F GTPase dephosphorylate phospho-tyrosine

False, it hydrolyzes GTP

T/F: An unaided eye can see particles of 900 micrometers.

True