Deck 5: Protein Function

Question 1

When oxygen is bound to the heme group of myoglobin, it is coordinated between _____ and _____.

A) F8 His; Fe³⁺ of heme
B) E7 His; Fe³⁺ of heme
C) F8 His; Fe²⁺ of heme
D) E7 His; Fe²⁺ of heme
E) none of the above

Answer 1

E7 His; Fe²⁺ of heme

Question 2

What is the prominent type of secondary structure observed in myoglobin?

A) $\beta$ -helices
B) $\alpha$ -bends
C) parallel $\beta$ -sheets
D) antiparallel $\beta$ -sheets
E) $\alpha$ -helices

Answer 2

$\alpha$ -helices

Question 3

While the composition of hemoglobin in adult humans is $\alpha$ ₂ $\beta$ ₂, in the developing fetus, _____ is observed

A) _{2 2}
B) $\alpha$ ₂ 11ee7c0f_0126_1306_ae82_71a7bb4c3276_TBW1044_11 ₂
C) $\alpha$ ₂ 11ee7c0f_33c4_72c7_ae82_97e5349a473f_TBW1044_11 ₂
D) $\alpha$ _{2 2}
E) $\alpha$ ₂ $\gamma$ ₂

Answer 3

$\alpha$ ₂ $\gamma$ ₂

Question 4

Which of the following occurs in hemoglobin upon oxygen binding?

A) the heme Fe²⁺ is pulled out of the plane of the heme group
B) the His coordinated to the heme Fe²⁺ is pushed away from the heme group
C) the central cavity between the four subunits is decreased in size
D) hemoglobin changes from the R state to the T state
E) all of the above occur

Question 5

Which of the following explains the conversion of hemoglobin subunits from deoxy to oxy state?

A) all four subunits switch simultaneously
B) each subunit switches only upon oxygen binding to the particular subunit
C) both $\alpha$ subunits simultaneously switch first followed by both $\beta$ subunits
D) both $\beta$ subunits simultaneously switch first followed by both $\alpha$
subunits
E) none of the above

Question 6

Which of the following fibers is correctly paired with the protein that forms the fiber?

A) microfilaments: actin
B) microtubule: tubulin
C) extracellular support fibers: collagen
D) intermediate filaments: keratin
E) all of the above

Question 7

During the formation of microfilaments, which of the following occurs?

A) ATP binds to F-actin
B) F-actin polymerizes, becoming G-actin
C) ATP hydrolysis is catalyzed by F-actin
D) polymerization proceeds quickly at first, then slows after about ten actin monomers have polymerized
E) none of the above

Question 8

When a cell moves along a surface, actin _____ occurs at the leading edge while _____ occurs at the trailing edge

A) polymerization; depolymerization
B) depolymerization; polymerization
C) denaturation; renaturation
D) renaturation; denaturation
E) none of the above

Question 9

Which of the following details the nucleotide-binding site when tubulin dimers assemble into microtubules?

A) both $\alpha$ and $\beta$ sites are bound to GTP
B) the $\alpha$ site is bound to GTP; the $\beta$ site is bound to GDP
C) the $\alpha$ site is bound to GDP; the $\beta$ site is bound to GTP
D) both $\alpha$ and $\beta$ sites are bound to GDP
E) the $\alpha$ site is bound to GTP; the $\beta$ site is unoccupied following GTP hydrolysis and release of GDP

Question 10

Which of the following explains how cell division is blocked by drugs that prevent proper microtubule function?

A) the condensation of chromatin requires a microtubule skeleton
B) production of new membranes for organelles and nucleus requires microtubules
C) chromosomes separate along a microtubule spindle
D) division of organelles between daughter cells requires organelle movement along microtubules
E) none of the above

Question 11

What is the most prevalent secondary structure observed in the proteins of intermediate filaments?

A) $\alpha$ -helices
B) $\beta$ -helices
C) $\alpha$ -sheets
D) $\beta$ -sheets
E) both $\alpha$ -helices and $\beta$ -helices are observed

Question 12

Which amino acid is critical for crosslinking of keratin fibers?

A) Ser
B) Lys
C) His
D) Cys
E) Gln

Question 13

Ascorbic acid is required for the production of _____ in collagen.

A) hydroxylysine
B) $\gamma$ -carboxyglutamic acid
C) desmosine
D) aspartate $\beta$ -semialdehyde
E) hydroxyproline

Question 14

The helical structure of collagen contains _____.

A) three right-handed helices wound around each other in a right-handed triple helix
B) three right-handed helices wound around each other in a left-handed triple helix
C) three left-handed helices wound around each other in a left-handed triple helix
D) three left-handed helices wound around each other in a right-handed triple helix
E) none of the above

Question 15

Which amino acid is critical for crosslinking of collagen trimers?

A) Ser
B) Lys
C) His
D) Cys
E) Gln

Question 16

Bone and tendons contain _____ while hair and nails contain _____.

A) collagen; keratin
B) actin; keratin
C) tubulin; collagen
D) collagen; actin
E) tubulin; keratin

Question 17

In a muscle cell, what is the name for the bundles of myosin tails?

A) cytoskeleton
B) thick filaments
C) intermediate filaments
D) thin filaments
E) none of the above

Question 18

Each myosin head contains a binding site for _____ and a binding site for _____.

A) tubulin; GTP
B) another myosin molecule; ATP
C) kinesin; GTP
D) actin; ATP
E) none of the above

Question 19

Which of the following correctly describes the sequence of events in the myosin-actin cycle?

A) myosin release from actin, ATP binds to myosin, myosin binds to another actin subunit, release of P_i and ADP, stretched myosin returns to original conformation
B) myosin release from actin, ATP binds to myosin, myosin binds to another actin subunit, stretched myosin returns to original conformation, release of P_i and ADP
C) ATP binds to myosin, myosin release from actin, myosin binds to another actin subunit, release of P_i and ADP, stretched myosin returns to original conformation
D) ATP binds to myosin, myosin release from actin, myosin binds to another actin subunit, stretched myosin returns to original conformation, release of P_i and ADP
E) myosin release from actin, myosin binds to another actin subunit, ATP binds to myosin, stretched myosin returns to original conformation, release of P_i and ADP

Question 20

Each kinesin head contains a binding site for _____ and a binding site for _____.

A) tubulin; GTP
B) another kinesin molecule; GTP
C) myosin; ATP
D) actin; ATP
E) tubulin; ATP

Question 21

The heads of kinesin bind to _____; the light chains of kinesin bind to _____.

A) tubulin; proteins in the membrane of a vesicle
B) proteins in the membrane of an organelle; tubulin
C) proteins in the membrane of a vesicle; actin
D) collagen fibers; proteins in the cell membrane
E) none of the above

Question 22

Which of the following correctly describes the sequence of events in the kinesin reaction cycle? For simplicity, the two heads are referred to as head 1 and head 2. Head 1 starts as the leading head.

A) head 1 releases tubulin, ATP binds to head 1, head 2 swings forward, head 2 binds to tubulin, ADP release from head 2, ATP hydrolysis in head 1
B) ATP binds to head 1, head 2 swings forward, ADP release from head 2, ATP hydrolysis in head 1, head 2 binds to tubulin, head 1 releases tubulin
C) ATP binds to head 1, head 2 swings forward, head 2 binds to tubulin, ATP hydrolysis in head 1, ADP release from head 2, head 1 releases tubulin
D) ATP binds to head 1, head 2 swings forward, head 2 binds to tubulin, ADP release from head 2, ATP hydrolysis in head 1, head 1 releases tubulin
E) none of the above

Question 23

Which of the following represents the longest distance traveled by a kinesin-vesicle complex?

A) movement of a mitochondria in a cardiac cell
B) movement of a neurotransmitter vesicle down the axon of a nerve cell
C) movement of a glucose filled vesicle to the membrane of a liver cell
D) movement of a lipid-filled vesicle within an intestinal cell
E) none of the above

Question 24

The best-known hemoglobin variant is _____.

Question 25

In Hb S, a ___ residue is replaced by a ___ residue.

Question 26

In Hb S, a valine residue binds to a(n) ___ patch causing ___ of the hemoglobin.