Cell Biology and Structure

Certain neurons or nerve cells may almost equal the length of body itself. The axon of a motor neuron in the spinal cord, that innervates a muscle in the foot can be about 1 meter (3 feet) in length.

The endoplasmic reticulum functions as a cytoplasmic framework providing a surface for some of the biochemical activities of the for some of the biochemical activities of the cell. In the liver cells of vertegrates, smooth endoplasmic reticulum (SEF) plsys a crucial role in detoxifying many poisons and drugs.

Casparian strips occur in radial walls of endodermis. The Casparian strip is a band of cell wall material deposited on the radial and transverse walls of the endodermis, and is chemically different from the rest of the cell wall - the cell wall being made of lignin and without suberin - whereas, the Casparian strip is made of suberin and sometimes lignin. It blocks the passive flow of materials such as water and solutes into the stele of a plant.
Thus, the correct answer is option A.

In the vesicle of mesosomes, the respiratory enzymes and the components of electron transport such as ATPase, dehydrogenase, cytochrome are present in low amount. So, they were considered anologous to mitochondria for their respiratory function. 

The Gram-negative cell wall is characterized by presence of outer membrane, a thinner peptidoglycan layer and extensive periplasmic space surrounding the peptidoglycan. The uppermost layer of the outer membrane has lipopolysaccharide, while the innermost layer is a typical lipid layer. Presence of membrane channels formed by porin proteins in outer membrane impart make them less penetrable as compared to Gram positive cells. Gram positive cells are characterized by presence of single thick layer of cell wall which is made up of peptidogycan, teichoic acid and lipoteichoic acid. They lack outer membrane and porin and have narrow periplasmic space. Plasma membrane is the unit membrane in both, Gram positive and Gram negative bacteria, present beneath cell wall with primarily phospholipids (making up about 30–40% of the membrane mass) and proteins (60–70%). The dense gelatinous solution surrounded by plasma membrane is cytoplasm which has same composition in both, Gram positive and Gram negative cells. Cilia are the eukaryotic structures which are absent in bacteria as they are prokaryotic. 

• Cell recognition and adhesion occur due to biochemicals of cell membranes name glycoproteins and glycolipids.
  
• Glycocalyx or pericellular matrix is a carbohydrate-enriched coating of glycoprotein and a glycolipid that covers the cell membranes of few bacteria, epithelial cells and other cells. 
  
• It is mainly used in the recognition of the cell (distinguish between healthy and diseased cells) and also regulates the endothelial vascular tissues.
• So, the correct answer is 'Glycoproteins and glycolipids'.

Gram-positive organisms have two of these basal body rings, one in the peptidoglycan layer and one in the plasma membrane.

• Glycocalyx or pericellular matrix is a carbohydrate-enriched coating of glycoprotein and a glycolipid that covers the cell membranes of few bacteria, epithelial cells and other cells. 
  
• It is mainly used in the recognition of the cell (distinguish between healthy and diseased cells) and also regulates the endothelial vascular tissues.
  
• So, the correct answer is 'Plasmalemma'.

The glycocalyx is a glycoprotein-polysaccharide covering that surrounds the cell membranes of some bacteria, epithelia and other cells. The glycocalyx is a type of identifier that the body uses to distinguish between its own healthy cells and transplanted tissues, diseased cells, or invading organisms. 
Thus, the correct answer is option C.

Gram staining differentiates bacteria by the chemical and physical properties of their cell walls by detecting peptidoglycan, which is present in a thick layer in gram-positive bacteria. In a gram stain test, gram-positive bacteria retain the crystal violet dye, while a counterstain (safranin or fuchsine) added after the crystal violet gives all gram-negative bacteria a red or pink colouring.

The large, bubble-shaped epidermal cells that occur on the upper surface of the leaves of monocots are called as bulliform cells. They are also called as motor cells. They help in the unfolding of developing leaves. It involves in the rolling and unrolling of mature leaves in response to alternating wet and dry periods.

• Guard cells are specialized epidermal cells present on the surface of leaves and stems of plants that control the gaseous exchange in plants.
• The guard cells form stomatal pores through which gaseous exchange and transpiration take place.
• In monocots, the guard cells are dumbbell shape.
• In dicots, they are kidney or bean shaped.
• So, the correct answer is 'Beans'.

Palisade tissues are present just beneath the epidermis and are composed of elongated cells arranged parallel to each other in one to three layers. These cells are marked by the presence of abundant chloroplast and thus provide the site for photosynthesis. Loosely arranged irregular cells with large intercellular spaces make the spongy parenchyma, which is present just beneath the palisade tissue. They contain less chloroplast as compared to that of palisade tissue. Thus, the correct answer is option A.