Following statements are regarding to multiple signaling pathways in vertebrate cells that regulate outer mitochondrial membrane permeability and apoptosis.

A. In healthy cells, the anti-apoptotic protein Bcl-2, or its homolog Bcl-xL, binds to Bak or Bax pro-apoptotic proteins, blocking the ability of Bak or Bax to oligomerize and form pores in the outer mitochondrial membrane.

B. The presence of specific trophic factors (e.g., NGF) leads to activation of their cognate receptor tyrosine kinases (e.g., TrkA) and inactivation of the PI-3 kinase–PKB (protein kinase B) pathway.

C. PKB phosphorylates Bad, and phosphorylated Bad forms a complex with a cytosolic 14-3-3 protein. This sequestered Bad is unable to bind to Bcl-2.

D. In the absence of trophic factors, nonphosphorylated Bad binds to Bcl-2, releasing Bax and Bak and allowing them to form oligomeric membrane pores and holes.

E. DNA damage or ultraviolet irradiation leads to induction of synthesis of the BH3-only Puma protein. Puma binds to Bak and Bax as well as to Bcl-2, allowing Bak and Bax to form oligomeric pores.

F. Removal of a cell from its substratum disrupts integrin signaling, leading to release of the BH3-only Bim protein from the cytoskeleton. Bim also binds to Bak and Bax to promote pore formation.

Which of the following is incorrect?

#Question id: 2524

#Unit 2. Cellular Organization

Which cytoplasmic fibrils are most like the nuclear lamins?

#Question id: 2525

#Unit 2. Cellular Organization

What kind of molecules must pass between the nucleus and the cytoplasm?

#Question id: 2526

#Unit 2. Cellular Organization

cell walls essential and are important features of plant cells that perform a number of essential functions. Which of the following is not the characteristics of cell wall?

#Question id: 2527

#Unit 2. Cellular Organization

Transpirational water flow in the xylem requires a mechanically strong wall that resists from,

#Question id: 2528

#Unit 2. Cellular Organization

Cell walls of prokaryotes, fungi, algae, and plants differ from each other in chemical composition and molecular structure, yet they all serve three common functions:

a) regulating cell volume

b) determining cell shape

c) mechanically protecting the delicate protoplast against biochemical and physical assaults

d) used to make synthetic fibers

Which of the following common functions is correct?

#Question id: 2529

#Unit 2. Cellular Organization

Cell walls commonly are classified into two major types. This classification is based not on structural or biochemical differences;

A) primary walls and

B) secondary walls

i) walls formed during cell growth

ii) walls that are formed after cell enlargement stops

iii) multilayered walls that are strengthened and waterproofed by lignin

iv) Usually they are thin and simple, but some times may be thick and multilayered, such as those found in collenchyma or in the epidermis

v) highly specialized in structure and composition, reflecting the differentiated state of the cell

Which of the following is the correctly represents features of primary and secondary walls?