Which structures perform the function of mitochondria in bacteria? 
The solid linear cytoskeletal elements having a diameter of 6 nm and made up of a single type of monomer are known as: 
The cytoskeleton is unique to eukaryotic cells. It is a dynamic three-dimensional structure that fills the cytoplasm. This structure acts as both muscle and skeleton, for movement and stability. The long fibers of the cytoskeleton are polymers of subunits. The primary types of fibers comprising the cytoskeleton are microfilaments, microtubules, and intermediate filaments.
Microfilaments are fine, thread-like protein fibers, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin.
Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein tubulin--these subunits are termed alpha and beta.
Intermediate filaments are about 10 nm diameter and provide tensile strength for the cell. Lamin is the protein present in intermediary filaments.
So, the correct answer is 'Microfilaments'.
The osmotic expansion of a cell kept in water is chiefly regulated by: 
The vacuole is bound by a single membrane called tonoplast. It also functions as semipermeable membrane. It segregates vacuolar contents from cytoplasm, allows osmotic entry or exit of water, concentration and storage of nutrients as well as wastes.
Match the following and select the correct answer: 
► Centriole: There are two main functions of centrioles
1. Cell division :The main function of the centriole is to help with cell division in animal cells. The centrioles help in the formation of the spindle fibers that separate the chromosomes during cell division (mitosis).
2. Celiogenesis :The second function of centrioles that we will focus on is celiogenesis. Celiogenesis is simply the formation of cilia and flagella on the surface of cells. Cilia and flagella help the cell move.
► Chlorophyll molecules are arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts.
► A crista is a fold in the inner membrane of a mitochondrion.
► Ribosomes comprise a complex macromolecular machine, found within all living cells, that serves as the site of biological protein synthesis (translation). Ribosomes link amino acids together in the order specified by messenger RNA(mRNA) molecules.
DNA is not present in : [2015 RS]
Ribosomes are composed of ribonucleic acid and proteins and are not surrounded by any membrane. These are site for protein synthesis.
Nuclear envelope is a derivative of : [2015 RS]
A nuclear membrane, also known as the nuclear envelope, nucleolemma or karyotheca, is the double lipid bilayer membrane which surrounds the genetic material and nucleolus in eukaryotic cells.
The nuclear membrane consists of two lipid bilayers - the inner nuclear membrane, and the outer nuclear membrane. The space between the membranes is called the perinuclear space, a region contiguous with the lumen (inside) of the endoplasmic reticulum.
The nuclear membrane has many small holes called nuclear pores that allow material to move in and out of the nucleus.
In late prophase, nuclear envelope disappears and reappears in late telophase from rough endoplasmic reticulum (RER).
Which one of the following is not an inclusion body found in prokaryotes ?
Prokaryotes are the primitive organism which lacks membrane-bounded organelles and nucleus. Prokaryotic cells have some microscopic structures in their cytoplasm. They serve specific purposes for the cell.
Inclusions are aggregates of specific chemical compounds and often serve as a reservoir of energy or carbon. Common inclusions are poly--hydroxyalkanoate, sulfur globules, cyanophycin globules, and polyphosphate.
Polyribosomes (or polysomes) also known as ergosomes are a cluster of ribosomes, bound to the mRNA molecule during translation process found in the eukaryotes.
Select the correct matching in the following pairs: [2015 RS]
Rough endoplasmic reticulum contains ribosomes found attached to it, therefore RER synthesise proteins. Smooth endoplasmic reticulum is the major site for synthesis of lipids. Phospholipids are different from simple lipids as simple lipids are esters of fatty acid with various alcohols while compound or conjugated lipids like phospholipids are esters of fatty acids with alcohol but contain some other substances also like phosphate group in phospholipid.
Which of the following are not membrane bound? [2015 RS]
Ribosomes are the protein factory of a cell. These are non-membranous organelle which attaches on endoplasmic reticulum by transcolon.
The function of the gap junction is to [2015 RS]
The function of the gap junction is to facilitate communication between adjoining cells by connecting the cytoplasm for rapid transfer of ions, small molecules and some large molecules.
The term cell was given by
In a 1665 publication called Micrographia, experimental scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens.
A protoplast is a cell : [2015 RS]
Protoplasts are cells with the plasma membrane, cytoplasm and nucleus which have their cell wall removed by the action of enzymes. Cellulase enzymes digest the cellulose in plant cell walls while Pectinase enzymes break down the pectin holding cells together. Once the cell wall has been removed , the resulting protoplast is spherical in shape.
Which of the following statements is true for a secretory cell?
RER is frequently observed in the cells actively involved in protein synthesis and secretion. RER is well developed in cells engaged in synthesis of secretory products.
Match the columns and identify the correct option.
(a) → (iii),
(b) → (iv),
(c) → (i),
(d) → (ii).
Cellular organelles with membranes are : [2015 RS]
Cellular organelles with membranes are Lysosomes, Golgi apparatus and mitochondria.
Lysosomes are single membrane-bound organelles which contain acid hydrolases or digestive enzymes that digest excess or worn out organelles, food particles, engulfed viruses or bacteria and macromolecules.
Golgi apparatus is a single membrane-bound organelle consists of folded and flattened membranes that are involved in secretion and helps in intracellular transport.
The mitochondria is a double-membraned cell organelle, known as the powerhouse of the cell which is present in all eukaryotic cells.
So, the correct answer is 'Lysosomes, Golgi apparatus and mitochondria'.
Satellite DNA is important because it : [2015 RS]
Cell wall is absent in : [2015 RS]
The cell wall is the hard protective covering of all plant, fungal and some bacterial cells. Mycoplasma is a genus of bacteria that lack a cell wall and surrounded by their cell membrane only.
Mitochondria and chloroplast are 
(a) Semi-autonomous organelles
(b) Formed by division of pre-existing organelles and they contain DNA but lack protein synthesizing machinery
Which one of the following options is correct ?
Mitochondria & chloroplast are semiautonomous cell organelle which are formed by division of pre-existing organelle & contain DNA but they also contain proteinsynthesizing machinery, thus (a) is true & (b) is false.
Microtubules are the constituents of 
The microtubules are found in the cytoplasmic matrix of all eukaryotic cells. They also occur in cilia, flagella, centrioles, basal bodies, and mitotic apparatus.
Spindle fibers form the protein structure which helps in mitosis and meiosis.
Centrioles are the two cylindrical structures of a cell organelle called centrosome.
Cilia and flagella are fine hair-like outgrowths of the membrane.
While peroxisomes are the microbodies.
So, the correct answer is 'Spindle fibers, centrioles, and cilia'.
Which one of the following cell organelles is enclosed by a single membrane ?
Lysosome is enclosed by a single membrane while Mitochondria, Chloroplasts and Nuclei are enclosed by double membrane.