Cell The Unit of Life BIOLOGY - Cell The Unit of Life

The nucleolus is the site of formation of:

Which of the following features is common to prokaryotes and many eukaryotes?

Which of the following feature is not associated with centrosome?

Which of the following is not found in an eukaryotic nucleus:

Which of the following does not have cell wall?

New cells generate from:

1. Bacterial fermentation.
2. Regeneration of old cells.
3. pre-existing cells.
4. Abiotic materials.

Which of the following is not correct?

1. Robert Brown discovered the cell.
2. Schleiden and Schwann formulated the cell theory.
3. Virchow explained that cells are formed from pre-existing cells.
4. A unicellular organism carries out its life activities within a single cell.

Which of the following is correct:

1. Cells of all living organisms have a nucleus.
2. Both animal and plant cells have a well defined cell wall.
3. In prokaryotes, there are no membrane bound organelles.
4. Cells are formed de novo from abiotic materials.

What term is given to:

1. The centriole-like structure from which a cilium/ flagellum emerges?
2. The core of a cilium/ flagellum?

Which is the largest cell?

Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.

What is a mesosome in a prokaryotic cell? Mention the functions that it performs.

Multicellular organisms have division of labour. Explain.

What are nuclear pores? State their function.

Cell is the basic unit of life. Discuss in brief.

Match the following

	Column I		Column II
a.	Cristae	i.	Flat membranous sacs in stroma.
b.	Cisternae	ii.	Infoldings in mitochondria.
c.	Thylakoids	iii.	Disc-shaped sacs in Golgi apparatus.

Eukaryotic cells have organelles which may not be bound by a membrane. Group the various sub-cellular organelles into these categories.

Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).

Classify the plastids on the basis of the types of pigments found in them. State the function of each type.

Explain the association of carbohydrate to the plasma membrane and its significance.

Structures of the bacterial ribosome have provided a framework for understanding universal mechanisms of protein synthesis. However, the eukaryotic ribosome is much larger than it is in bacteria, and its activity is fundamentally different in many key ways. All ribosomes are composed of two subunits, both of which are built from RNA and protein. Bacterial ribosomes, for example of Escherichia coli, contain a small subunit (SSU) composed of one 16S ribosomal RNA (rRNA) and 21 ribosomal proteins (r-proteins) and a large subunit (LSU) containing 5S and 23S rRNAs and 33 rproteins. In contrast to their bacterial counterparts, eukaryotic ribosomes are much larger and more complex, containing additional rRNA in the form of so-called expansion segments (ES) as well as many additional r-proteins and r-protein extensions.

(1).Ribosomes are present in
(a) Eukaryotes only
(b) Eukaryotes and prokaryotes
(c) Prokaryotes only
(d) Eukaryotes, prokaryotes and viruses

(2) In 70S ribosomes, ‘S’ stands for
(a) SI unit (b) Solubility factor (c) Svedberg unit (d) all of these

(3) 80 S ribosomes occur in
(a) Eukaryotic cells of animals
(b) Eukaryotic cells of animals and plants
(c) Both Eukaryotic cells and prokaryotic cells
(d) all of these

(4) Ribosomes are made up of
(a) RNA only (b) RNA and proteins (c) RNA, DNA and proteins (d) Nucleic acids, proteins and lipids

(5) Polysomes are
(a) multiple units of ribosomes
(b) attachment of many ribosomes to a common mRNA
(c) attachment of many mRNA to a common ribosome
(d) lysosomal aggregations

Cell membrane, also called plasma membrane, thin membrane that surrounds every living cell, delimiting the cell from the environment around it. Enclosed by this cell membrane are the cell’s constituents, large, water-soluble, highly charged molecules such as proteins, nucleic acids, carbohydrates, and substances involved in cellular metabolism. Cell membranes are composed primarily of fatty-acid based lipids and proteins. Membrane lipids are principally of two types, phospholipids and sterols (generally cholesterol). Both types share the defining characteristic of lipids—they dissolve readily in organic solvents—but in addition they both have a region that is attracted to and soluble in water.

(1).Plasma membrane is made up of
(a) A protein, a lipid and a cellulose layer
(b) Bimolecular lipid layer surrounded by protein layers
(c) A protein layer between two lipid layers
(d) A lipid layer between two protein layers

(2) Fluid mosaic model of cell was put forward by –
(a) Danielli and Dawson
(b) Singer and Nicolson
(c) Garner and Allard
(d) Watson and Crick

(3) Which of the following statements best describes the chemical composition of
plasma-membrane?
(a) Plasma membrane is composed of two layers—one layer of phospholipids and one layer
of proteins.
(b) Plasma membrane is composed of equal numbers of phospholipids, proteins, and
carbohydrates.
(c) Plasma membrane is bilayers of proteins with associated lipids and carbohydrates.
(d) Plasma membrane is bilayers of phospholipids with associated proteins and
carbohydrates.

(4) Most abundant lipid in the cell membrane is
(a) phospholipids (b) cerebrosides (c) glycolipids (d) None of these

What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.

Describe the structure of the following with the help of labelled diagrams. Nucleus

Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.

Describe the structure of the following with the help of labelled diagrams. Centrosome

What are the characteristics of prokaryotic cells?

Assertion : Living organisms possess specific individuality with the definite shape and size. 
Reason : Both living and non living entities resemble each other at the lower level of organisation.