EXAM #3 Review

Question 1

A signal molecule that binds to a plasma-membrane protein is a:

Answer 1

Ligand

Question 2

The three stages of cell signaling are:

Answer 2

Reception, transduction, and response

Question 3

True/False
The addition and removal of phosphate groups on proteins are mediated by two different enzymes, phosphatases, which bind ATP and transfer a phosphate group to the target protein, and kinases, which remove phosphate groups from proteins.

Answer 3

False

Question 4

What determines if a signaling molecule binds to a receptor on the surface or enters the cell?

Answer 4

size, hydrophobicity, and ability to cross the plasma membrane

Question 5

Adenylyl cyclase is used in a GPCR signal transduction pathway to
A. Form ATP from cAMP
B. Remove a phosphate from cAMP
C. Hydrolyze GTP to GDP
D.  Bind a ligand
E. None of the above

Answer 5

E. None of the above

Question 6

Identify the description of signal amplification
A. One receptor protein binds to many different primary messenger molecules
B. One messenger molecule activates many second messengers
C. One intracellular enzyme modifies one protein within the cell
D. A primary messenger activates transcription by binding to many different promoters

Answer 6

B. One messenger molecule activates many second messengers

Question 7

Which of the following mutations would NOT result in constitutive activation of the associated signaling protein?

A. A mutation in Ras that prevents its hydrolysis of bound GTP to GDP

B. A mutation in MAP kinase that prevents its association with MAPKK

C. A mutation in MAPKKK that prevents its translocation to the nucleus

D. A and B

E. A and C

Answer 7

A. A mutation in Ras that prevents its hydrolysis of bound GTP to GDP

Question 8

True/False
While a GPCR pathway controls the synthesis and degradation of glycogen, insulin signaling is controlled by a receptor tyrosine kinase pathway.

Answer 8

True

Question 9

Name the four essential structural components of a receptor tyrosine kinase molecule

Answer 9

1. Extracellular ligand binding domain
2. Single membrane spanning alpha helix
3. Cytosolic region with weak protein tyrosine kinase activity
4. C-terminal domain containin tyrosine residues

Question 10

Which of the following a NOT a characteristic of microfilaments 
A. Composed of tubulin subunits
B.  Function in muscle contraction
C. Dynamically grow and shrink
D.  Have a cable-like structure

Answer 10

A. Composed of tubulin subunits

Question 11

What cellular filament is found in the flagella of eukaryotic cells?

Answer 11

Microtubules

Question 12

What cytoskeletal component is comprised of G-actin subunits organized into polymers
A. F-actin
B. Microtubules
C. Microfilaments
D. Myosin

Answer 12

C. Microfilaments

Question 13

True/False

Cilia and flagella are composed of microtubules arranged in a 9+4 formation

Answer 13

False

Question 14

Name the cytoskeletal structure essential for mitosis.

Answer 14

Centrosomes (microtubules)

Question 15

During what stage do condensed chromosomes consisting of two sister chromatids begin to appear?
A. Anaphase
B. Telophase
C. Prophase
D. Interphase

Answer 15

C. Prophase

Question 16

What types of motor proteins are associated with movement of chromosomes during mitosis?

Answer 16

Kinesin and dynein motors

Question 17

What is the function of centrioles in the transmission of genetic information

Answer 17

Formation of the mitotic spindle

Question 18

kangaroo has 16 total chromosomes in a diploid cell. How many kinetochores are present in a kangaroo cell at mitosis?

Answer 18

32

Question 19

Interphase is the longest stage of the cell cycle. What three sub-phases occur during interphase?

Answer 19

G1, S, G2

Question 20

What cyclin molecule interacts with two different cyclin dependent kinase molecules to mediate the cell cycle?

Answer 20

Cyclin A

Question 21

If DNA damage is detected after DNA replication has been completed, protein kinases phosphorylate ________, which prevents dephosphorylation of _________, inhibiting activation of the mitosis promoting factor (MPF).

Answer 21

CDC25, CDK1

Question 22

True/False
Crossing over and the exchange of genetic information between homologous chromosomes occurs during prophase II of meiosis

Answer 22

False,

occurs during Prophase I of meiosis

Question 23

True or False
Due to both their extreme size and hydrophilicity, steroid hormones cannot be transported through the plasma membrane and must instead rely on signal transduction pathways to impact cellular function

Answer 23

False

Question 24

What of the following is NOT an example of a secondary messenger
A. Calcium
B. cAMP
C. Phosphokinase A
D. cGMP

Answer 24

C. Phosphokinase A

Question 25

Glycogen synthesis is controlled using a GPCR signal transduction pathway in response to glucogon or epinephrine. Which statement regarding this pathway is NOT correct A. Phosphorylation of glycogen synthase by activated phosphokinase A leads to glycogen degradation to glucose B. High cAMP levels inactivate phosphokinase A, allowing for phosphorylation of both glycogen synthase and glycogen phosphorylase C. Activated phosphokinase A inactivates glycogen synthase via phosphorylation, preventing synthesis of glycogen molecules D. A and B E. A and C F. B and D

Answer 25

D: A and B

Question 26

Which of the following is NOT a step in rod phototransduction by rhodopsin? A. Activation of rhodopsin by photons B. Conversion of cGMP to GMP by phosphodiesterase C. Opening of cGMP-dependent ion channels and hyperpolarization of the membrane D. Activation of phosphodiesterase by light-activated rhodopsin through Gαt

Answer 26

C. Opening of cGMP-dependent ion channels and hyperpolarization of the membrane

Question 27

True or False Receptor tyrosine kinases (RTKs) are another type of signal transduction receptor molecule. Instead of using a heterotrimeric G protein complex to transduce the signal, RTKs are able to activate Ras GTPase, which then activates an effector molecule.

Answer 27

True

Question 28

Which of the following statements about myofibrils is correct? A. Myofibrils are composed of filaments of actin and keratin B. Myofibrils are cylindrical bundles of actin and myosin found in the cytoplasm of muscle fibers C. Myofibrils are organized into chains called sarcomeres that are involved in muscle contraction D. A and B E. A and C F. B and C

Answer 28

F: B and C

Question 29

What is the answer to the extra credit question on the exam?

Answer 29

Happy Holidays!

Question 30

True/False | Free energy from the hydrolysis of GTP drives the polymerization of actin monomers

Answer 30

False (actin polymerization utilizes ATP)

Question 31

Unlike microfilaments and microtubules, intermediate filaments are a diverse group of proteins that share structural features and cellular roles. Which of the following statements regarding intermediate filaments is NOT correct? A. All intermediate filaments consist of a central α-helical rod domain with variable amino and carboxy terminal regions B. Are not found in yeast of plant cells C. Formed by protofilaments of antiparallel tetramers D. Are highly dynamic and show (+)/(-) polarity based on the sequence of their amino termini

Answer 31

D. Are highly dynamic and show (+)/(-) polarity based on the sequence of their amino termini

Question 32

Which of the following in the sliding filament model of muscle contraction does not occur A. Ca+ is released from the sarcoplasmic reticulum and bind to troponin B. Myosin releases actin C. Power stroke D. ATP binds to actin

Answer 32

D. ATP binds to actin

Question 33

``` The G1 checkpoint in budding yeast is called what? A. The point of no return B. The turning point C. The START point D. The restriction point ```

Answer 33

C. The START point

Question 34

``` You discover a mutant kidney cell that continues to undergo mitosis even though it has not reached adequate size. A protein analysis of the cell shows high levels of cyclin E throughout the cell cycle; however, sequencing of the cyclin E gene reveals no mutations. What other genes would you then analyze to explain this phenotype? A. Cyclin A B. Wee1 C. Rb D. CDC25 ```

Answer 34

C. Rb

Question 35

``` Mitosis promoting factor or maturation promoting factor (MPF) is a dimer that controls entry and exit from mitosis. It is composed of what cyclin/CDK pair A. Cyclin A/CDK1 B. Cyclin B/CDK1 C. Cyclin D/CDK4/6 D. Cyclin B/CDK2 ```

Answer 35

B. Cyclin B/CDK1

Question 36

``` What two protein kinases recognize DNA damage in the form of double or single-stranded breaks to halt progression through the cell cycle A. CDC25; Wee1 B. PKA; PKC C. Rb; E2F D. ATR; ATM ```

Answer 36

D. ATR; ATM

Question 37

A pre-replication complex consisting of origin recognition proteins and an inactive helicase complex associates with origins of replication prior to the initiation of S phase. What processes are responsible for activation of the pre-replication complex A. Phosphorylation of helicase by cyclin E/CDK2 and DDK B. Dephosphorylation of helicase by cyclin E/CDK2 and DDK C. Upregulation of DNA polymerase production by phosphorylation of Rb D. Activation of helicase after DNA cleavage by topoisomerases+

Answer 37

A. Phosphorylation of helicase by cyclin E/CDK2 and DDK