Lysosomes originate by budding off from the membrane of the trans-Golgi network, a region of the Golgi complex responsible for sorting newly synthesized proteins, which may be designated for use in lysosomes, endosomes, or the plasma membrane. Answer : (d)

Answer : (b)

Answer : (d)

plastids are interchangeable in their form. Generally, three types of plastids arepresent in plant cells, i'.e., leucoplasts (storage), chromoplast (coloured) and chloroplasts(synthesis of food green pigment). Depending upon the circumstances, one type of plasmid may be converted into another type. e.g., (i) In Capsicum, the cells of ovary consist of leucoplasts. When ovary changes into fruit, leucoplasts are transformed into chloroplasts. When the fruit ripens chloroplast areconverted into chromoplast. (ii) The leucoplast in stem tubers of potato, on exposure to sunlight transform to chloroplasts. In some cases the chloroplasts gets converted during ripening of fruits, e.g., tomato chili when they change colour from green to red. In occurs because of chlorophyll and degeneration of lamella. Answer : (b)

Water has high specific heat and high heat of Vaporization ( Latent heat) This property ensures slow heating of water; maintain constant temperature of living organisms and environment. Answer : (b)

The glyoxysome is a plant peroxisome, especially found in germinating seeds, involved in the breakdown and conversion of fatty acids to acetyl-CoA for the glyoxylate bypass. Since it is also rich in catalase, the glyoxysome may be related to the microbodies or peroxisomes or derived from them. Structurally, plant and animal cells are very similar because they are both eukaryotic cells. They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes,ribosomes and peroxisome Answer : (a)

Mitochondria are shaped perfectly to maximize their productivity. They are made of two membranes. The outer membrane covers the organelle and contains it like a skin. The inner membrane folds over many times and creates layered structures called cristae. The fluid contained in the mitochondria is called the matrix. Answer : (c)

phosphorylation, chemical process in which a phosphate group is added to an organic molecule. In living cells phosphorylation is associated with respiration, which takes place in the cell's mitochondria, and photosynthesis, which takes place in the chloroplasts. Answer : (b)

Microtubules are the largest type of filament, with a diameter of about 25 nanometers (nm), and they are composed of a protein called tubulin. Actin filaments are the smallest type, with a diameter of only about 6 nm, and they are made of a protein called actin. Tubulin is the protein that polymerizes into long chains or filaments that form microtubules, hollow fibers which serve as a skeletal system for living cells. Microtubules have the ability to shift through various formations which is what enables a cell to undergo mitosis or to regulate intracellular transport. Defination of Microtubule Microtubules are microscopic hollow tubes made of the proteins alpha and beta tubulin that are part of a cell’s cytoskeleton, a network of protein filaments that extends throughout the cell, gives the cell shape, and keeps its organelles in place. Microtubules are the largest structures in the cytoskeleton at about 24 nanometers thick. They have roles in cell movement, cell division, and transporting materials within cells. Answer : (c)

The membrane surrounding the plant cell vacuole is called the tonoplast. This a very active, dynamic membrane. Plant cells use their vacuoles for transport and storing nutrients, metabolites, and waste products. The tonoplast is a lipid bilayer, typical of other cellular membranes. Recall that a lipid is part of the fats, oils, waxes, etc. group. A bilayer indicates that there are two layers, each with the hydrophillic (water loving) head facing out into the cellular cytosol and the vacuolar cytosol. Cytosol is a liquid component of a cell that surrounds organelles like the vacuole. The hydrophobic (water fearing) tails face inwards. The tonoplast is semi-permeable as well. This means that certain molecules and substrates can pass through it but others cannot. This allows the tonoplast to maintain a balance of ions inside and outside of the central vacuole. Answer : (a)

The nuclear membrane is a lipid bilayer, meaning that it consists of two layers of lipid molecules. The outer layer of lipids has ribosomes, structures that make proteins, on its surface. It is connected to the endoplasmic reticulum, a cell structure that packages and transports proteins. Answer : (c)

According to Huxley the protoplasm is the physical basis of life. Inside the cell wall of living cell the living substance is known as protoplasm. The protoplasm is a thick fluid or jelly like substance Answer : (d)

Protein synthesis occurs in three subcellular compartments, namely, cytoplasm, plastids( chloroplast is a type of organelle known as a plastid), and mitochondria Mitochondria and chloroplasts are similar in the following ways: 1. Both are thought to have originally been free-living organisms, like bacteria, that were, during the course of evolution, engulfed by a larger cell in which they survived as intracellular symbionts 2. Both mitochondria and chloroplasts have their own genomes and their own protein synthesis machinery. 3. Both mitochondria and chloroplasts are sites of production of ATP, the energy currency of the cell. Answer : (d)

Lampbrush chromosomes are a special form of chromosome found in the growing oocytes (immature eggs) of most animals, except mammals Lampbrush chromosomes have also been found in spermatocytes of several species, Answer : (b)

Chromatin is a complex of nucleic acids (e.g., DNA or RNA) and proteins (histones) and non-histone proteins. Answer : (a)

Answer : (d)

Organelles lacking any membrane: Ribosomes, Centrioles, Nucleolus. Centrosomes are made of from arrangement of two barrel-shaped clusters of microtubules, called centrioles and a complex of proteins that help additional microtubules to form. Centrosomes are also non-membrane bound Answer : (d)

Starch is a polysaccharide comprising glucose monomers joined in α 1,4 linkages. The simplest form of starch is the linear polymer amylose; amylopectin is the branched form. Answer : (b)

Hypothesis is a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation. In 1838 Schleiden defined the cell as the basic unit of plant structure, idea was a hypothesis based on the observation which had to be experimentally verified by other workers Answer : (d)

lysosome is surrounded by a membrane that maintains an acidic environment within the interior via a proton pump. Lysosomes contain a wide variety of hydrolytic enzymes (acid hydrolases) that break down macromolecules such as nucleic acids, proteins, and polysaccharides. Answer : (a)

heterophagosome. an intracytoplasmic vacuole formed by phagocytosis or pinocytosis, which becomes fused with a lysosome, subjecting its contents to enzymatic digestion. Answer : (d)

Cholesterol acts as a bidirectional regulator of membrane fluidity because at high temperatures, it stabilizes the membrane and raises its melting point, whereas at low temperatures it intercalates between the phospholipids and prevents them from clustering together and stiffening.Cholesterol acts as a buffer, increasing fluidity at low temperatures and decreasing fluidity at high temperatures. And the last are unsaturated fatty acids in our phospholipid. When we increase the amount of unsaturated fatty acids in our cell membrane, the fluidity also increases. Answer : (a)

Phospholipids are a class of lipids that are a major component of all cell membranes. They can form lipid bilayers because of their amphiphilic characteristic. Phospholipids are the primary molecules found in the plasma membrane. A phospholipid is unique in that it has a hydrophilic region called the head, and a hydrophobic region known as the tail. The interior of the cell is primarily made of water. Likewise, the exterior of the cell is usually surrounded by watery fluid. This means that the plasma membrane could not possibly consist of just one layer of phospholipids. This is because the hydrophobic (or water fearing) tail region would have to interact with one of the watery regions inside or outside of the cell. So instead, the cells have evolved to have two layers of phospholipids. Answer : (c)

a vacuole in the cytoplasm of a cell, containing a phagocytosed particle enclosed within a part of the cell membrane. Pinosome: A tiny fluid-filled vesicle (bubble) within a cell. Phagosomes, macropinosomes and autophagosomes mature in a manner similar to endosomes, and may require fusion with normal endosomes for their maturation. Answer : (d)

Non-membrane bound organelles are more solid structures that are not fluid-filled, so they have no need for a membrane. Examples of non-membrane bound organelles are ribosomes, the cell wall, and the cytoskeleton Answer : (d)

Prokaryotic Flagella- They are single stranded. A covering membraneous sheath is absent. The size is smaller. They are narrower. Each flagellum has three parts: basal body, hook and filament. Basal body bears rings. They are formed of protein flagellin. They perform rotatory movements. Eukaryotic Flagella- They are 11 stranded. Flagella are covered by sheath derived from plasmalemma. The size is larger. They are thicker. Each flagellum has two parts: basal body and shaft. Basal body bears rootlets. The strands are formed of protein tubulin. They perform lashing or undulatory movements. Answer : (d)

seive tube cells of vascular plants and RBCs are enucleated Answer : (b)

organelles are bounded by a single membrane. For example, vacuole, lysosome, Golgi Apparatus, Endoplasmic Reticulum, peroxisomes Double membrane bound cell organelles are bounded by two unit membranes- Mitochondria, Chloroplasts, Nucleus Non-membrane bound cell organelles are not bounded by membranes- Ribosomes (70S & 80S), Centrosomes, Cilia and flagella, Microtubules Answer : (a)

The average adult male is about 60% water. The average adult woman is about 55% water because women naturally have more fatty tissue than men Answer : (b)

Polytene chromosomes are infact formed by pairing of two somatic homologous chromosomes which undergo repeated endomitosis, forming a number of strands. These strands remain attached to a common large chromocentre of all polytene chromosomes and are rich in heterochromatin. Answer : (b)

The outer covering membrane made up of the lipid bilayer is absent over the nucleolus. The boundary of the nucleus is called the nuclear envelope.It consists of two phospholipid bilayers: an outer membrane and an inner membrane. Nucleolus is present as a dark spherical spot inside the nucleus. It helps in the formation of the ribosomes proteins which help in the translation proc Answer : (a)

The Golgi apparatus produces specialist vesicles or vessels for the transport of its products. Some of these have special wrappings or coatings that help identify the contents. Some vesicles are recyclable. Lysosomes are manufactured and budded into the cytoplasm by the Golgi apparatus with enzymes inside. Answer : (d)

Eukaryotic cells contain three types of filaments as microtubules, microfilaments and intermediate filaments which give definite shape to cell and also helps in directional movements Answer : (a)

Answer : (d)

Histone octamer. A histone octamer is the eight protein complex found at the center of a nucleosome core particle. It consists of two copies of each of the four core histone proteins (H2A, H2B, H3 and H4). The octamer assembles when a tetramer, containing two copies of both H3 and H4, complexes with two H2A/H2B dimers. Answer : (a)

Answer:(c)

Transverse diffusion or flip-flop involves the movement of a lipid or protein from one membrane surface to the other. Unlike lateral diffusion, transverse diffusion is a fairly slow process due to the fact that a relatively significant amount of energy is required for flip-flopping to occur. Most large proteins do not flip-flop due to their extensive polar regions, which are unfavorable in the hydrophobic core of a membrane bilayer. This allows the asymmetry of membranes to be retained for long periods, which is an important aspect of cell regulation. Also because hydrophilic parts lipid or protein molecules would have to cross the membrane's hydrophobic core, lipid or protein molecules rarely flip transversely (flip-flop) across the membrane Answer : (d)

Polytene chromosomes are found during the interphase stage of the cell division in the nuclei of the salivary gland cells of the larvae of Diptera (fruitfly or Drosophila melanogaster). Polytene chromosomes are formed due to endoduplication, duplication without separation and replication of DNA without cell division Answer : (a)

Depending on the position of the centromere, chromosomes are of the following types: Metacentric chromosome: The centromere is present right in the middle of the chromosome. It forms two equal arms of the chromosome. Submetacentric chromosome: The centromere is present a little away from the middle of the chromosome. It forms two unequal arms of the chromosome. Acrocentric chromosome: The centromere is present close to one of the ends of the chromosome. It forms one short and another quite long arm. Telocentric chromosome: A terminal centromere. There is only one arm of the chromosome with the centromere at the end. Answer : (b)

Permeability of cell membranes to sodium and potassium is regulated by internal calcium, which in turn is controlled by a calcium pump that utilizes ATP. Answer : (d)

Disintegration of tadpole tail requires digestion of tail tissue, which is achieved by very high lysosomal enzymatic activity. Explanation: Lysosomes are single membrane bound small vacuole shaped organelles. These are formed from Golgi bodies. Lysosome stores a lot of digestive and hydrolysing enzymes. Lysosomal enzymes help macrophagic cells to digest cell debris that they remove. The enzymes could also be released inside the cell to achieve cell lysis. Answer : (a)

Microfilaments are polymers of the protein actin and are 7 nm in diameter. Microtubules are composed of tubulin and are 25 nm in diameter. Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell Answer : (c)

Flagella and cilia have a 9 + 2 arrangement of microtubules. This arrangement refers to the 9 fused pairs of microtubules on the outside of a cylinder, and the 2 unfused microtubules in the center Answer : (a)

A prokaryote is a unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle Cyanobacteria classified as prokaryotic, derive their energy through photosynthesis, but lack a nucleus or membrane bound organelles, like chloroplasts. In cyanobacteria, there are other membranous extensions into the cytoplasm called chromatophores which contain pigments. Chromatophores are light sensitive organelles where certain photoreceptor pigments are present whereas Chloroplast is an organelles that houses as a site for photosynthesis Option "d" correct Answer : (d)

A circular DNA occurs as a bacterial DNA, chloroplast and mitochondria DNA. Which forms a closed loop or a circle with no ends and contains the entire genome Answer : (d)

Answer : (b)

Answer : (a)

Lysosomes are 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. Phagosome can be defined as the vesicle which is formed around the material engulfed by a phagocyte through phagocytosis. The fusion of a lysosome with a phagosome gives rise to secondary lysosomes Answer : (a)

The enzymatic reactions of cellular respiration begin in the cytoplasm, but most of the reactions occur in the mitochondria. Cellular respiration occurs in the double-membrane organelle called the mitochondrion. The folds in the inner membrane are called cristae. Answer : (b)

Lampbrush chromosome (immature eggs) of most animals, except mammals. Chromosomes transform into the lampbrush form during the diplotene stage of meiotic prophase I due to an active transcription of many genes. They are highly extended meiotic half-bivalents, each consisting of 2 sister chromatids. Answer : (d)