HIR action spectrum for the inhibition of hypocotyl elongation of dark-grown lettuce seedlings. The peaks of activity for the inhibition of hypocotyl elongation occur in the UV-A, blue, and far-red regions of the spectrum.

TLS Online TPP Program

#Id: 8396

#Unit 2. Cellular Organization

Each sarcomere contains two major types of filaments: 

Thick filaments (myosin II)

Thin filaments (actin and associated proteins)

TLS Online TPP Program

#Id: 8397

#Unit 2. Cellular Organization

Z disk 

Thin actin filaments are assembled with their (+) ends embedded in a densely staining structure

TLS Online TPP Program

#Id: 8398

#Unit 2. Cellular Organization

In the presence of ATP and Ca+2 , the myosin heads extending from the thick

filaments walk toward the (+) ends of the thin filaments.

TLS Online TPP Program

#Id: 8399

#Unit 2. Cellular Organization

The structure of the sarcomere is maintained by a number of accessory proteins: 

1. CapZ 

2.Tropomodulin

3.Titin 

4.Nebulin

TLS Online TPP Program

#Id: 8400

#Unit 2. Cellular Organization

In skeletal muscle cells, 

a low cytosolic Ca+2 level is maintained by a unique Ca+2 ATPase that continually pumps Ca+2 ions from

the cytosol containing the myofibrils into the SR, establishes a reservoir of Ca+2 in the SR.

TLS Online TPP Program

#Id: 8402

#Unit 2. Cellular Organization

The arrival of a nerve impulse at a neuromuscular junction triggers an action potential in sarcolemma.