Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen Answer : (b)

The glycocalyx is a carbohydrate-enriched coating that covers the outside of many eukaryotic cells and prokaryotic cells, particularly bacteria .The cell membrane also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma Answer : (a)

Cilia are slender, microscopic, hair-like structures or organelles that extend from the surface of nearly all mammalian cells. The length of a single cilium is 1-10 micrometres and width is less than 1 micrometre. Motile' (or moving) cilia are found in the lungs, respiratory tract and middle ear. These cilia have a rhythmic waving or beating motion. They work, for instance, to keep the airways clear of mucus and dirt, allowing us to breathe easily and without irritation. They also help propel sperm. Answer : (d)

The middle lamella is a calcium pectate layer which cements the cell walls of two adjoining plant cells together. It consists of pectins and other non-cellulose polysaccharides. Answer : (d)

An endosymbiont or endobiont is any organism that lives within the body or cells of another organism in a mutualistic relationship with the host body or cell, often but not always to mutual benefit. Mitochondria and chloroplasts are self-dividing; they contain their own DNA and protein-synthesizing machinery, similar to that of prokaryotes. Option "b" correct. Chloroplasts produce ATP and trap photons by mechanisms that are complex and yet similar to those of certain prokaryotes. The endosymbiotic theory deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics. Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria, specifically alpha-proteobacteria and cyanobacteria, respectively Option "c" correct De novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to their being recycled after partial degradation. Option "a" correct Therefore all options are correct. Answer : (d)

Both 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. Dynein "arms" attached to the microtubules serve as the molecular motors. Answer : (c)

Desmosomes are intercellular junctions that provide strong adhesion between cells, found only in animal cells are desmosomes Because they also link intracellularly to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues. Plasmodesmata a narrow thread of cytoplasm that passes through the cell walls (plant cell) of adjacent plant cells and allows communication between them. Answer : (c)

Polytene chromosomes were originally observed in the larval salivary glands of Chironomus midges by Édouard-Gérard Balbiani in 1881. Answer : (a)

Mitochondria and Chloroplast is considered as autonomous cell organelle due to the following counts : Mitochondria have their own DNA which can replicate independently. The mitochondrial DNA produces its own mRNA, tRNA and rRNA. The organelles posses their own ribosomes, called mitoribosomes. mitochondria is not a self sustaining entity. The proteins produced by mitochondria are part of oxidative phosphorylation complexes. It requires another (at least 200) nuclear genes for mitochondrial genome replication, transcription, maintenance and regulation. Even the mitochondrial translation machinery is incomplete; i.e. while rRNA and tRNA required for translation of mitochondrial protein making genes are produced by mitochondria itself, the proteins required for mitochondrial translation complex are encoded by nuclear genes. - This explains your "semi" part. Answer : (c)

Answer : (c)

Teichoic acids are in the cell wall of most Gram-positive bacteria by nature. These include species ilike Staphylococcus, Corynebacterium, Bacillus, Streptococcus, Clostridium, and Listeria. These acids extend to the surface of the peptidoglycan layer. Answer : (b)

Cell wall possesses minute cytoplasmic bridges between adjacent cells which are called plasmodesmata. Plasmodesmata have been shown to be sensitive to various levels of calcium, pH, and light, demonstrating that the mechanisms of plasmodesmata transport are more complex than previously thought. Plasmodesmata tend to close when there is a significant pressure differential between adjacent cells, again speaking to a role of plasmodesmata in a wound response upon a loss of turgor pressure. Answer : (d)

Endoplasmic reticulum (ER), a continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells and serves multiple functions, being important particularly in the synthesis, folding, modification, and transport of proteins . Answer : (d)

Cells maintain pools of free nucleotides for a variety of purposes. Adenosine derivatives are the most common free nucleotides, because ATP is used in the largest number of reactions. ATP is a nucleotide consisting of an adenine base attached to a ribose sugar, which is attached to three phosphate groups. These three phosphate groups are linked to one another by two high-energy bonds called phosphoanhydride bonds Answer : (d)

The nucleosome core particle consists of fourteen turns of B-form DNA around an octamer of histone proteins. The octamer contains two copies each of four different proteins: H2A, H2B, H3, and H4. Answer : (a)

An idioblast is an isolated plant cell that differs from neighboring tissues. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin, tannin or pigments etc Inclusions are stored nutrients, secretory products, and pigment granules. Examples of inclusions are glycogen granules in the liver and muscle cells, lipid droplets in fat cells, pigment granules in certain cells of skin and hair, water-containing vacuoles, and crystals of various types. Answer : (d)

Shape of Chromosomes: Chromosomes are classified into four types by their shape in metaphase or in anaphase, which, in turn, is determined by the position of the centromere: i) Telocentric chromosomes: Rod-like and have a centromere situated on the prox1mal end. ii) Acrocentric chromosomes: Rod-like and have a small, or even imperceptible, arm. iii) Submetacentric chromosomes: Chromosomes having unequal arms are thus ‘L’ shaped. iv) Metacentric chromosomes: Having equal or almost equal arms and thus are ‘V’-shaped. Answer : (b)

A prokaryote is a unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle. Prokaryotic cell structure Flagellum (only in some types of prokaryotes) Long, whip-like protrusion that aids cellular locomotion used by both gram positive and gram negative organisms. Cell membrane Surrounds the cell's cytoplasm and regulates the flow of substances in and out of the cell. Cell wall (except genera Mycoplasma and Thermoplasma) Outer covering of most cells that protects the bacterial cell and gives it shape. Cytoplasm A gel-like substance composed mainly of water that also contains enzymes, salts, cell components, and various organic molecules. Ribosome Cell structures responsible for protein production. Nucleoid Area of the cytoplasm that contains the prokaryote's single DNA molecule. Glycocalyx (only in some types of prokaryotes) A glycoprotein-polysaccharide covering that surrounds the cell membranes. Inclusions It contains the inclusion bodies like ribosomes and larger masses scattered in the cytoplasmic matrix. Answer : (b)

Cell theory was eventually formulated in 1839. This is usually credited to Matthias Schleiden and Theodor Schwann. However, many other scientists like Rudolf Virchow contributed to the theory The three statements or tenets of the cell theory are: All living beings are made up of cells. Cell is the most basic unit of life. All cells must come from pre-existing cells. Answer : (a)

Cytoplasm contains many different shapes and sizes of particles in it and holds them in place in the cell. Cytoplasm contains proteins that are 20 to 25 percent soluble, and this includes enzymes. Carbohydrates, lipids and inorganic salts are particles in cytoplasm. The outermost layer of cytoplasm, the plasmogel, can absorb water or remove it, and it is based on the cells need for liquid. The chemical composition of cytoplasm is 80 percent water and 20 percent of organic and inorganic compounds that vary in proportions. Answer : (b)

option "d" Because lysosome is polymorphic (primary, secondary, tertiary, autophagic) and polyfunctional cell organelle. Answer : (d)

Answer:(c)

The Krebs cycle ( also known as citric acid cycle) occurs in the mitochondrial matrix and generates a pool of chemical energy (ATP, NADH, and FADH2) from the oxidation of pyruvate, the end product of glycolysis. Pyruvate is transported into the mitochondria and loses carbon dioxide to form acetyl-CoA, a 2-carbon molecule. Calvin cycle take place in the stroma (the inner space of chloroplasts). The reactions of the Calvin cycle add carbon (from carbon dioxide in the atmosphere) to a simple five-carbon molecule called RuBP. These reactions use chemical energy from NADPH and ATP that were produced in the light reactions. The final product of the Calvin cycle is glucose. The Hill Reaction the light dependent reactions of photosynthesis which take place in the thylakoid membranes of chloroplasts. The Hill reaction of photosynthesis was discovered by Robin Hill (1937). He found that isolated chloroplasts from plants can release oxygen when they are illuminated by sunlight in the presence of a suitable electron acceptor such as ferricyanide. Glycolysis happens in the cytoplasm of cells and does not require the presence of oxygen. It is said to be anaerobic. It is the first step used by cells to extract energy from glucose in the form of ATP Answer : (b)

Cells produce waste like all living things. The lysosomes are the garbage disposals of the cell. When a part of the cell becomes damaged or obsolete, it is moved to the outer edge of the lysosome. The membrane of the lysosome opens and the molecule is moved into the lysosome. Once inside, the digestive enzymes produced by the lysosome break down the molecule. After it is has been completely broken down, the lysosome opens to release the remains back into the cell in the form of a vesicle that the cell can expel through its membrane. The final remains are much more compact and easier for the cell to manage than the original molecule. This process is also the same for invaders of the cell, such as bacteria and other foreign matter. Answer : (b)

Ribosomes are not organelles. They are not membrane-enclosed, instead they are macromolecules made of both RNA and proteins. ribosomes found in bacteria even though bacteria do not contain organelles Answer : (c)

A sister chromatid refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined together by a common centromere. Answer : (c)

Acetabularia used in Hammerling's nucleocytoplasmic experiment is unicellular uninucleate green algae. Hammerling's experiment of Acetabularia involved exchanging rhizoid and stalk. Presence of hereditary information in the nucleous was proved by the work of Hammerling on single called alga Acetabularia. Answer : (c)

Amyloplasts are non-pigmented organelles found in some plant cells. They are responsible for the synthesis and storage of starch granules, through the polymerization of glucose. Amyloplasts also convert this starch back into sugar when the plant needs energy. The main function of elaioplasts are synthesis and storage of fatty acids, terpenes, and other lipids, and they can be found in the embryonic leaves of oilseeds, citrus fruits, as well as the anthers of many flowering plants. Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. Chloroplasts absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant. Chromoplasts synthesize and store pigments such as orange carotene, yellow xanthophylls, and various other red pigments. As such, their color varies depending on what pigment they contain. Answer : (a)

Nucleosome can be said when the DNA is wrapped around the histone protein, so this structure is called nucleosome and it has 200 base pairs of the DNA helix. Answer : (b)

Difference between Prokaryotes and eukaryotes on Nuclear Material Basics The differences between the nuclear material of prokaryotic cells and that of eukaryotic cells are evident at a glance on microscopic examination. Eukaryotes have nuclei separated from the cytoplasm by a double membrane and containing both chromosomes and a nucleolus, whereas prokaryotes have no true nucleus, with their nuclear material distributed diffusely throughout the interior of the cell. The nuclear material of eukaryotes is arranged into multiple chromosomes bound to the protein histone, while prokaryotes contain a single circular strand of DNA and have no histones. Answer : (c)

If the endoplasmic reticulum (ER) has ribosomes attached to it, it is called rough ER; if it does not, then it is called smooth ER.It usually has ribosomes attached and is involved in protein and lipid synthesis The proteins made by the rough endoplasmic reticulum are for use outside of the cell. Functions of the smooth endoplasmic reticulum include synthesis of carbohydrates, lipids, and steroid hormones; detoxification of medications and poisons; and storage of calcium ions. (a) - (v) Sphaerosomes or Oleosomes are small cell organelles bounded by single membrane which take part in storage and synthesis of lipid. (b) - (iii) Dictyosomes are stacks of flat, membrane-bound cavities (cisternae) that together comprise the Golgi apparatus (c) - (i) The most prominent role of peroxisomes in photosynthetic plant tissues is their participation in photorespiration, a process also known as the oxidative C2 cycle or the oxidative photosynthetic carbon cycle. (d) - (iv) Elaioplasts are a type of leucoplast that is specialized for the storage of lipids in plants. Elaioplasts house oil body deposits as rounded plastoglobuli, which are essentially fat droplets.. (e) - (ii) Answer : (a)

The cell as a basic unit of structure of living things was discovered by Schleiden and Schwann Answer : (a)

Lysosomes contains hydrolytic enzymes which can devour anything present in the cell (except the membrane of lysosome). So if a lysosome burst open the enzymes will eventually kill the cell by eating organelles of the cell Answer : (a)

Typically mitochondria is sausage-shaped or cylindrical having a diameter of 0.2-1.0µm (average 0.5μm) and length 1.0-4.1µm. Answer : (c)

Chloroplasts are a type of plastid—a round, oval, or disk-shaped body that is involved in the synthesis and storage of foodstuffs. Structure of Chloroplasts Chloroplasts found in higher plants are generally biconvex or planoconvex (shaped like a disc) shaped. In higher plants, the average size of chloroplast is 4-6 µ in diameter and 1-3 µ in thickness. Chloroplasts can be found in the cells of the mesophyll in plant leaves. In different plants chloroplasts have different shapes, they vary from spheroid, filamentous saucer-shaped, discoid or ovoid shaped. They are vesicular and have a colorless center. Some chloroplasts are in shape of club, they have a thin middle zone and the ends are filled with chlorophyll. In algae a single huge chloroplast is seen that appears as a network, a spiral band or a stellate plate. The size of the chloroplast also varies from species to species and it is constant for a given cell type. Answer : (a)

In mammals, a single Golgi apparatus is usually located near the cell nucleus, close to the centrosome. he perinuclear region is the cytoplasmic region just around the nucleus. Answer : (c)

The smallest DNA bundle is called a nucleosome and it is made of DNA and protein. The protein portion is made of small units called histones. The core particle is made of four types of histones (H2A, H2B, H3, and H4). DNA wraps around the core particle Answer : (c)

Protein glycosylation is an enzyme-directed chemical reaction that takes place in the ER(Endoplasmic Reticulum) and in the Golgi Apparatus body of the cell. General glycosylation within the ER helps with folding, and glycosylation in the Golgi body tells a protein where to go. glycosylation mainly refers in particular to the enzymatic process that attaches glycans to proteins, or other organic molecules. The Golgi apparatus gathers simple molecules and combines them to make molecules that are more complex. It then takes those big molecules, packages them in vesicles, and either stores them for later use or sends them out of the cell. It is also the organelle that builds lysosomes (cell digestion machines) Answer : (a)

The process is called oxidative phosphorylation and it happens inside mitochondria. Mitochondria, using oxygen available within the cell convert chemical energy from food in the cell to energy in a form usable to the host cell. The process is called oxidative phosphorylation and it happens inside mitochondria. In the matrix of mitochondria the reactions known as the citric acid or Krebs cycle produce a chemical called NADH. NADH is then used by enzymes embedded in the mitochondrial inner membrane to generate adenosine triphosphate (ATP). In ATP the energy is stored in the form of chemical bonds. Answer : (c)

Nuclear protein import is a selective process. Proteins destined for the nucleus contain NLSs. These short stretches of amino acids interact with proteins located in the cytoplasm, on the nuclear envelope, and/or at the nuclear pore complex. Answer : (a)

Strasburger coined the terms cytoplasm and nucleoplasm. Cytoplasm occurs around the nucleus and inside the plasma membrane containing various organelles. Answer : (d)

The kinetochore is a protein complex assembled on the centromeric region of DNA. A kinetochore is a protein structure that forms on a chromatid during cell division and allows it to attach to a spindle fiber on a chromosome. Answer : (b)

In cilia and flagella, the filaments are the doublet microtubules, all of which are arranged with their (+) end at the outer tip of the axoneme. Answer : (b)

The cell was first discovered and named by Robert Hooke in 1665. Answer : (a)

Osmoregulation refers to the physiological processes that maintain a fixed concentration of cell membrane-impermeable molecules and ions in the fluid that surrounds cells Membrane, in biology, the thin layer that forms the outer boundary of a living cell or of an internal cell compartment. The outer boundary is the plasma membrane, and the compartments enclosed by internal membranes are called organelles. Biological membranes have three primary functions: (1) they keep toxic substances out of the cell; (2) they contain receptors and channels that allow specific molecules, such as ions, nutrients, wastes, and metabolic products, that mediate cellular and extracellular activities to pass between organelles and between the cell and the outside environment; and (3) they separate vital but incompatible metabolic processes conducted within organelles. Answer : (b)

Oxysomes are the structures which are present on the surface of the folded Inner Membrane of the Mitochondria. The matrix side of the inner membrane and cristae bear numerous tennis racket like particles present called oxysomes. They are also known as elementary particles, Parson’s particle, Fernandez-Moran particle, F0F1-particles, F0F1-ATPase, H+ – ATPase, ATP synthetase or ATP synthase. A mitochondrion contains about 104 -105 oxysomes regularly placed at the intervals of l0 nm. Oxysomes comprise about 15% of the total inner membrane protein. Each oxysome is a multi-polypeptide complex consists of 3 parts: (i) Head piece or F1 particle or soluble ATPase. (ii) Base or F0 subunit. (iii) A stalk that connects F1 subunit with the F0 subunit. microsomes are heterogenous vesicle-like artifacts (~20-200 nm diameter) re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells. Myeloid bodies are believed to be differentiated areas of smooth endoplasmic reticulum membranes, and they are found within the retinal pigment epithelium in a number of lower vertebrates Informosomes and polyribosome-associated proteins in eukaryotes Answer : (b)

The plasma membrane is composed of a phospholipid bilayer, which is two layers of phospholipids back-to-back. Phospholipids are lipids with a phosphate group attached to them. The phospholipids have one head and two tails. The head is polar and hydrophilic, or water-loving. Answer : (c)

Plasmodesmata are microscopic channels which traverse the cell walls of plant cells and some algal cells, enabling transport and communication between them Answer : (d)

Metacentric chromosomes have the centromere in the center, such that both sections are of equal length. Human chromosome 1 and 3 are metacentric. Submetacentric chromosomes have the centromere slightly offset from the center leading to a slight asymmetry in the length of the two sections. Human chromosomes 4 through 12 are submetacentric. Acrocentric chromosomes have a centromere which is severely offset from the center leading to one very long and one very short section. Human chromosomes 13,15, 21, and 22 are acrocentric. Telocentric chromosomes have the centromere at the very end of the chromosome. Humans do not possess telocentric chromosomes but they are found in other species such as mice Answer : (c)

The Golgi complex, where protein glycosylation takes place, has been regarded as a single functional unit, consisting of cis-, medial-, and transcisternae in mammalian cells Cisternae pack and modify proteins and polysaccharides. Biosynthetic cargo proteins travel through cisternae and undergo glycan remodeling and other modifications. Cisternae package the proteins and then send them to transport carriers. They also package polysaccharides that are synthesized in the Golgi apparatus. Answer : (d)