Cell Biology Test - 6

• Inclusion bodies, sometimes called elementary bodies, are nuclear or cytoplasmic aggregates of stable substances, usually proteins.
• They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins.
• The metachromatic granules are the type of inclusion bodies present in bacteria. They appear red when stained with a blue dye.
• They are present in certain bacteria, yeasts, yeastlike fungi and protozoa.
• They are composed of complex polyphosphates, lipids and nucleoprotein molecules. They serve as an intracellular phosphate reserve.
• Metaphase is the third phase of mitosis, the process that separates duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells.
• Metamorphosis, the transformation of the larva into an adult.
• Chromatophores are pigment-containing and light-reflecting cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. 

• Eukaryotic cells usually have multiple chromosomes, composed of DNA and protein.
• Some eukaryotic species have just a few chromosomes, others have close to 100 or more. 
• These chromosomes are protected within the nucleus. In addition to a nucleus, eukaryotic cells include other membrane-bound structures called organelles. 
• Organelles allow eukaryotic cells to be more specialized than prokaryotic cells.
• Prokaryotic cells are usually smaller and simpler than eukaryotic cells.
• They do not have a nucleus or other membrane-bound organelles.
• In prokaryotic cells, the DNA, or genetic material, forms a single large circle that coils up on itself.
• Therefore, Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

• Lysosomes are an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane.
• Lysosomes contain a wide variety of hydrolytic enzymes (acid hydrolases) that break down macromolecules such as nucleic acids, proteins, and polysaccharides.
• A phagolysosome, or endolysosome, is a cytoplasmic body formed by the fusion of a phagosome with a lysosome in a process that occurs during phagocytosis.
• Formation of phagolysosomes is essential for the intracellular destruction of microorganisms and pathogens.
• A phagosome is a vesicle that forms by invagination of the plasma membrane with its associated lipids and proteins during phagocytosis of microbes or microbial proteins.
• Any phagosome containing material exogenous to the cell. Fusion with a lysosome leads to the formation of a heterolysosome.
• Digestive vacuoles are intracellular vacuole into which lysosomal enzymes are discharged and digestion of the contents occurs.
• Therefore, both Assertion and Reason are true and Reason is not the correct explanation of Assertion.

• Fluid mosaic model of the plasma membrane was given by Singer and Nicholson in the year 1972.
• The cell membrane is considered as a two-dimensional liquid that restricts the lateral diffusion of membrane components.
• The plasma membrane is considered to be a fluid combination of phospholipids, cholesterol and proteins.
• The biological membrane is considered to be a qualified structure in which the lipids and integral proteins are arranged in a mosaic manner.
• Gorter and Grendal measured the lipid content of haemolysed erythrocytes and concluded that cell membrane is chiefly formed of phospholipids arranged to form a bimolecular lipid sheet.
• The cell was first discovered and named by Robert Hooke in 1665.
• Roberston gave the Unit Membrane model for the biological membrane.

• Ribosomes are composed of rRNA and proteins and are not surrounded by any membrane.
• Ribosomes are the sites of protein synthesis and free ribosomes synthesize non-secretory proteins while Endoplasmic reticulum bound ribosomes to synthesize secretory proteins.
• 80 S ribosomes are made up of ribonucleoproteins in the ratio of 40:60 (RNA: Protein). 80 S ribosomes consist of-

• 40 S smaller subunit- with 33 protein molecules and a single 18 S-rRNA.
• 60 S larger subunit- about 40 protein molecules and three types of rRNAs which are 28S, 5.8S and 5S.

Archaebacteria are the most primitive and ancient bacteria species that consist of a protein homologous to eukaryotic core histones. 
The key characteristic features are: 

• They lack peptidoglycan in the cell wall, instead, pseudomurein is present.
• Lipids found in the cell membrane have a different structure than in all other organisms.
• They don’t possess membrane-bound organelles.

The sub-metacentric chromosomes have the centromere slightly offset from the center leading to a slight asymmetry in the length of the two sections.