All Free Biology MCQs with Answers

• A. Only gymnosperm cells
• B. All plant cells
• C. All eukaryotic cells
• D. Only bacterial cells

Explanation: Totipotency is the ability of a living somatic plant cell to develop into a complete plant. It was first demonstrated by Steward et. al (1964) using phloem cells of carrot. This technique is now used for multiplying rare and endangered plants through micropropagations. This technique is widely used for multiplying plants e.g., Chrysanthemum, Dioscorea floribunda, Coleus, Crotons, carnation plants, etc.

• A. Nucleolus
• B. Cytoplasm
• C. Mitochondria
• D. Golgi body.

Explanation: Nucleolus synthesizes and stores RNA. The ribosomal proteins are synthesized in the cytoplasm and shift to the nucleolus for the formation of ribosomal subunits by complexing with rRNA.

• A. Ca
• B. Zn
• C. K
• D. Cu.

Explanation: The middle lamella is the first formed layer present between two adjacent cells. It is situated outside the primary cell wall and is made up of calcium and magnesium pectate.

• A. Phytochrome
• B. Chlorophyll
• C. Anthocyanin
• D. Carotenoids

Explanation: Phytochrome is a plant pigment that can detect the presence or absence of light and is involved in regulating many processes that are linked to day length (photoperiod), such as seed germination and initiation of flowering. It consists of a light­-detecting portion, called a chromophore, linked to a small protein and exists in two interconvertible forms with different physical properties, particularly in the ability to bind to membranes.

• A. Mitochondria
• B. Spherosomes
• C. Nucleus
• D. Cell wall

Explanation: The spherosomes are spherical bodies, about 0.5­-1um wide and enclosed by a single unit membrane. They contain granular contents rich in lipids but also have some proteins. They occur in most plant cells but are abundant in the endosperm cells of oil seeds. Spherosomes arise from the endoplasmic reticulum.

• A. Centrioles
• B. Spindle fibres
• C. Cell plates
• D. Centromeres

Explanation: The centrioles occur in nearly all animal cells and in motile plant cells, such as zoospores of algae, sperm cells of ferns, and motile algae. They are absent is amoebae, prokaryotic cells, higher gymnosperms, and all angiosperms. An interphase (undividing) cell has a pair of centrioles (diplosome) usually near the nucleus. They lie in a small mass of specialized, distinctly staining cytoplasm that lacks other cell organelles. The centrioles and the centrosphere are together referred to as centrosome. Before cell division, the centrioles duplicate so that a dividing cell has a pair of centrioles at each pole of the spindle. Spindle fibers, cell plates and centromeres are present in all plant cells.

• A. Helically arranged protein molecules
• B. "9 + 2" membrane enclosed structure
• C. Unit membrane enclosed fibre
• D. Protein membrane enclosed fibre

Explanation: Prokaryotic flagellum is not surrounded by any membrane. It consists of a single thread. The thread is made of numerous identical spherical protein sub­-units called, flagellin. Each subunit is about 40 Å in diameter. The flagellin sub­units are arranged in helical spirals and form a hollow cylinder. Each flagellum is about 120­-150 Å thick.

• A. Cell division
• B. Cell adherence
• C. Cytolysis
• D. Cellular excretion

Explanation: In desmosomes, circular patches of cell membranes are held together by interaction of proteins that extend through each membrane into the space between cells. The cell membrane has a dense plate of proteins for mechanical support on the inner side and bears fine filaments, the tonofibrils, radiating into the cell. The desmosomes act as "spot welds" and keep the cells firmly together.

• A. Ribosomes
• B. Polysomes
• C. Plastids
• D. Lysosomes

Explanation: A lysosome is a tiny sac bounded by a single unit membrane of lipoprotein. It contains a dense, finely granular fluid. The latter consists of glycoprotein hydrolytic (digestive) enzymes called acid hydrolases. These include proteases, lipases, nucleases, glycosidases, sulphatases, acid phosphatases, etc.

• A. Protein synthesis
• B. Phosphorylation of flavoproteins
• C. Breakdown of macromolecules
• D. Oxidation-­reduction reactions.

Explanation: Respiratory chain is located in the inner membrane (cristae) of mitochondria. It consists of a series of proteins containing oxidation­reduction groups. Chemical treatment of the mitochondrial membrane results in the isolation of five complexes which have been designated as complexes I, II, III, IV, and V.