Practice Exam 4

1.Inositol triphosphate (IP3) stimulates Ca2+ entry into the cytoplasm from

  1. Extra cellular fluid
  2. Endoplasmic reticulum
  3. Mitochondria
  4. Nucleus
  5. None of the above

2. A phosphorylation cascade is

A. a sequence of second messenger production.

B. a sequence of kinase reactions.

C. a sequence of ligand-gated ion channel receptor activations

D. a sequence of G protein-linked receptor activations.

E. a sequence of tyrosine kinase-linked receptor activations.

3. Which of the following is NOT a second messenger?

A. cAMP

B. H+

C. cGMP

D. IP3

E. Ca2+

4. Which of the following is NOT contrasting actions of auxin and cytokinins?

A. root formation-shoot formation

B. apical dominance-axillary bud growth

C. cell elongation-cell division

D. apical meristem synthesis-root synthesis

E. cell growth-programmed cell death

5. What is NOT mediated by phytochromes?

A. phototropism

D. shade tolerance

B. de-etiolation

C. seed germination

E. flowering photoperiod

6.What is NOT a part of G protein-linked receptor signal transduction?

A. seven transmembrane segment receptor

B. exchange of GTP for GDP bound to G protein

C. hydrolysis of GTP to GDP

D. effect on second messenger production

E. phosphorylation of membrane effector enzyme

7.What is NOT an allosteric modulation during signal transduction?

A. ligand binding

B. tyrosine kinase-linked receptor dimerization

C. phosphorylation of tyrosine residue

D. adenylyl cyclase production of cAMP

E. GTP exchange for bound GDP of G protein

8.What is a typical steroid hormone receptor?

A. G protein-linked receptor

B. tyrosine kinase-linked receptor

C. ion channel-linked receptor

D. intracellular receptor

E. second messenger effector enzyme

9.Why is transautophosphorylation necessary during tyrosine kinase-linked receptor-dependent signal transduction?

A. to satisfy the 2nd law of thermodynamics

B. to delay the speed of signaling

C. to produce ATP in a later payoff phase

D. to attract cytoplasmic relay proteins

E. to change the receptor from membrane bound to cytoplasmic

10.In an ethylene over producing mutant, plant shoots would

  1. Never experience triple response
  2. Continually undergo triple response
  3. Exhibit thin, straight, fast-growing stems
  4. Exhibit thick, curved, slow-growing stems
  5. A & C
  6. B & D

11.What is true about G proteins?

A. contain intrinsic GTPase activity

B. are activated when GDP bound

C. are inactivated when GTP bound

D. can phosphorylate GDP to GTP when stimulated by a ligand-receptor complex

E. directly initiate the phosphorylation cascade

12.Indeterminate growth in plants depends on presence of

A. pith.

B. meristem.

C. cortex.

D. xylem.

E. phloem.

13.Which does NOT contribute to positive pressure of phloem flow?

A. Cotransport of sugar into sieve tube members.

B. Osmosis into the sieve tube members at a sugar source.

C. Water vapor loss through stomata.

D. Cotransport of sugar from phloem sap into a sugar sink cell.

E. Osmosis into the xylem flow at a sugar sink.

14.Regulation of mineral content of xylem sap occurs due to

A. apoplastic transport.

B. aquaporin exchange.

C. plasmodesmata selectivity

D. Casparian strip

E. all of the above

15.Signal transduction pathways result in cell-specific responses because

  1. Ligands are unique for every cell type
  2. Plasma membrane receptors are cell-type specific
  3. Each cell type contains unique genetic material
  4. Each cell type expresses a different set of target proteins
  5. B & D

16.An increase of in Pr conformation phytochromes may be associated with

  1. Plants experiencing indirect light
  2. Plants experiencing direct light
  3. Increase in plant height
  4. Axillary growth and branching
  5. A & C
  6. B & D