Endoplasmic reticulum is a network of membranous tubules within the cytoplasm of a eukaryotic cell, continuous with the nuclear membrane. It usually has ribosomes attached and is involved in protein and lipid synthesis. Answer : (b)

Water is present both inside and outside cells. In the body of a mammal for example although it is about 70% water by weight, about 46% (approximately 2/3) is inside cells, and about 23% (approx. 1/3) is present outside cells in blood plasma and other body fluids. Answer : (c)

In most bacteria, the most numerous intracellular structure is the ribosome which is the site of protein synthesis in all living organisms. All prokaryotes have 70S (where S=Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol. Bacteria have 70S ribosomes, each consisting of a small (30S) and a large (50S) subunit. E. coli, for example, has a 16S RNA subunit (consisting of 1540 nucleotides) that is bound to 21 proteins. The large subunit is composed of a 5S RNA subunit (120 nucleotides), a 23S RNA subunit (2900 nucleotides) and 31 proteins.[15] Eukaryotes have 80S ribosomes located in their cytosol, each consisting of a small (40S) and large (60S) subunit. Their 40S subunit has an 18S RNA (1900 nucleotides) and 33 proteins. The large subunit is composed of a 5S RNA (120 nucleotides), 28S RNA (4700 nucleotides), a 5.8S RNA (160 nucleotides) subunits and 46 proteins Answer : (c)

The number of F1 particles present in each mitochondria ranges from 100 to 1000. an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membran The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans. Ribosomes are different from other organelles because they have no membrane around them that separates them from other organelles Chlorophyll a and chlorophyll b are present in the thylakoid membranes inside the 'chloroplast', an organelle found inside the cells of green tissue Answer : (d)

It is generally believed that the energy-converting organelles of eucaryotes evolved from procaryotes that were engulfed by primitive eucaryotic cells and developed a symbiotic relationship with them. This would explain why mitochondria and chloroplasts contain their own DNA, which codes for some of their proteins Answer : (a)

Names of Nucleotides. The five bases are adenine, guanine, cytosine, thymine, and uracil, which have the symbols A, G, C, T, and U, respectively. The bases combine with the sugar to make the nucleotides adenosine, guanosine, cytidine, thymidine, and uridine. Uridine monophosphate (UMP), also known as 5′-uridylic acid (conjugate base uridylate), is a nucleotide that is used as a monomer in RNA. Answer : (a)

The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy. Answer : (d)

The most common water soluble vacuolar pigments are anthocyanins (red, blue, purple) and anthoxanthins (ivory to deep yellow). Carotene, Chlorophyll are fat soluble and are not found in vacuoles Xanthophyll is equally soluble in both water and organic solvent. Answer : (a)

The secondary cell wall is a structure found in many plant cells, located between the primary cell wall and the plasma membrane. The cell starts producing the secondary cell wall after the primary cell wall is complete and the cell has stopped expanding Answer : (a)

Chromoplasts are formed either from chloroplast or from leucoplast. For e.g. green tomatoes and chillies turn red on ripening due to the formation of the red pigment called lycopin replacing the cholorophyll. Yellow pigment carotene is developed in the carrot by replacing leucoplast. Answer : (a)

Chromosomes a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. nucleic acids is a complex organic substance present in living cells, especially DNA or RNA, whose molecules consist of many nucleotides linked in a long chain. Answer : (d)

The synthesis of sugar takes place during photosynthesis in chloroplast of autotrophic eukaryotes. Answer : (a)

The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The electron transport chain in the cell is the site of oxidative phosphorylation in prokaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, releasing energy to power the ATP synthase. Many enzymes are found in mitochondrion such as NADH dehydrogenase, Pyruvate oxidase, Succinate dehydrogenase, Glucose dehydrogenase which are essential for electron transport system Answer : (b)

membranes are composed primarily of phospholipids and proteins and are typically described as phospholipid bi-layers. 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. According to fluid mosaic model, plasma membranes are quasifluidic structures with a viscous lipid bilayer made up of phospholipids having proteins at places distributed as mosaic both on the surface and inside. Singer and Nicolson have described cell membrane as protein icebergs floating in sea of lipids. External proteins are called extrinsic proteins or peripheral proteins while the internal proteins are named intrinsic or integral. Answer : (c)

The nucleolus makes ribosomal subunits from proteins and ribosomal RNA, also known as rRNA. It then sends the subunits out to the rest of the cell where they combine into complete ribosomes. Ribosomes make proteins; therefore, the nucleolus plays a vital role in making proteins in the cell. Answer : (c)

The position of the centromere affects the shape of the daughter chromosomes during anaphase. Metacentric chromosomes produce V-shaped daughter chromosomes, submetacentric appear J-shaped and acrocentric form I-shapes Answer : (b)

Cyclosis: These are movements of cytoplasm within a cell (also called protoplasmic streaming). These are of two types : Rotation : When the protoplasm moves around a single central vacuoles in either clockwise or anticlockwise direction e.g., leaf cells of Hydrilla, Vallisneria. Circulation: When the movement of protoplasm occurs around different vacuoles in different directions within the cell e.g., staminal hair of Tradescantia, shoot hairs of gourds. Answer : (b)

The cell was first discovered and named by Robert Hooke in 1665. He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells (cork) as it appeared under the microscope. Answer : (a)

A single phospholipid molecule has a phosphate group on one end, called the “head,” and two side-by-side chains of fatty acids that make up the lipid “tails. All of the lipid molecules in cell membranes are amphipathic (or amphiphilic)—that is, they have a hydrophilic (“water-loving”) or polar end and a hydrophobic (“water-fearing”) or nonpolar end. The most abundant membrane lipids are the phospholipids. These have a polar head group and two hydrophobic hydrocarbon tails. Answer : (c)

Telomeres function to protect the ends of chromosomes from sticking to each other. They also protect genetic information during cell division because a short piece of each chromosome is lost every time DNA is replicated. Cells use a special enzyme called telomerase to keep dividing, which lengthens their telomeres Answer : (c)

Thylakoids - Flattened membranous sacs forming grana Centrioles are a membranous hollow microcylinders occur in pair and play important role in cell division. Ribosomes in chloroplast are 70 s type while those of cytoplasm in eukaryotic cells are 80 S type. The enzymes of lysosome (called suicidal bag) function at acidic pH (i.e., 5). Answer : (a)

A flagellum (plural: flagella) is a long, whip-like structure that helps some single celled organisms move. It is composed of microtubules. Flagella are organelles defined by function rather than structure. Flagella vary greatly. Both prokaryotic and eukaryotic flagella can be used for swimming but they differ greatly in protein composition, structure, and mechanism of propulsion. The word flagellum in Latin means whip. Answer : (d)

endocytosis is the taking in of matter by a living cell by invagination of its membrane to form a vacuole. internalises is another term for endocytosis Answer : (c)

If we consider the surface area as the criteria then the smallest cell organelle is ribosome and the largest cell organelle is nucleus in animal cell & vacuole in plant cell. Answer : (d)

A mitoplast is a mitochondrion that has been stripped of its outer membrane leaving the inner membrane intact. Answer : (d)

The main job of mitochondria is to perform cellular respiration. This means it takes in nutrients from the cell, breaks it down, and turns it into energy. Answer : (d)

plasmodesmata is a narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells and allows communication between them. Symplast is a continuous network of interconnected plant cell protoplasts. Answer : (a)

Bacteria (prokaryotic) have 70S ribosomes, each consisting of a small (30S) and a large (50S) subunit. Answer : (c)

F1 particle is a part of the F0-F1 complex. It is the 'Fraction 1' of ATP synthase. There are 2 particles of mitochondria which is Fo and F1. They are part of inner cristae membranes of the mitochondria.They are globular structures and also called as Racker particles. Answer : (c)

Lysosomes break down macromolecules into their constituent parts, which are then recycled. not Golgi apparatus Answer : (a)

Like glucose, maltose is a reducing sugar, because the ring of one of the two glucose units can open to present a free aldehyde group; the other one cannot because of the nature of the glycosidic bond. Maltose can be broken down to glucose by the maltase enzyme, which catalyses the hydrolysis of the glycosidic bond, to produce two molecules of α-D-glucose Hydrolysis of sucrose yields glucose and fructose. Product of hydrolysis of lactose are glucose and galactose. Answer : (b)

Apparato reticulo interno was discovered in 1898 by Italian physician Camillo Golgi during an investigation of the nervous system. Answer : (a)

A biological membrane or biomembrane is an enclosing or separating membrane that acts as a selectively permeable barrier within living things The endoplasmic reticulum serves many general functions, including the folding of protein molecules in sacs called cisternae and the transport of synthesized proteins in vesicles to the Golgi apparatus. Answer : (c)

The ER has a central role in lipid and protein biosynthesis. Its membrane is the site of production of all the transmembrane proteins and lipids for most of the cell's organelles, including the ER itself, the Golgi apparatus, lysosomes, endosomes, secretory vesicles, and the plasma membrane. The ER membrane makes a major contribution to mitochondrial and peroxisomal membranes by producing most of their lipids. In addition, almost all of the proteins that will be secreted to the cell exterior—plus those destined for the lumen of the ER, Golgi apparatus, or lysosomes—are initially delivered to the ER lumen. Answer : (d)

Polyribosomes or ergasomes are formed by the combination of 6-8 ribosomes attached on a single-strand of mRNA. mRNA brings about polymerisation of a specific protein molecule, with the help of ribosomes, from amino acid molecules found in the cytosol. Answer : (d)

A ribosome is made from complexes of RNAs and proteins and is therefore a ribonucleoprotein. Answer : (c)

In the late 1950’s, the use of electron microscopy helped to discover that the membrane was composed of proteins and lipids and has a bilayer structure. Answer : (b)

Golgi apparatus was discovered in 1898 by Italian physician Camillo Golgi during an investigation of the nervous system. After first observing it under his microscope, he termed the structure as apparato reticolare interno ("internal reticular apparatus"). Answer : (a)

The cell nucleus was discovered by Antonie van Leeuwenhoek in the 18th century. He first observed its structure in a sample of salmon blood. However, its intricate details were furnished by Robert Brown in the year 1831 Answer : (a)

Mitochondria and Chloroplasts both have 70s Ribosome, since they are evolved from prokaryotic bacteria and developed a symbiotic relationship with the cell. in animal cell all the organelles possess 80s ribosomes except mitochondria and chloroplast they have 70s ribosomal unit. Answer : (b)

The nuclear membrane consists two concentric phospholipid membranes. Nuclei contains a region called the nucleolus, where ribosome assembly begins. Besides, the nuclear membrane contains nuclear pore complexes that allow for transport of material into and out of the nucleus. Answer : (a)

The helical structure of double-stranded DNA is destabilized by increasing temperature. Above a critical temperature (the melting temperature), the two strands in duplex DNA become fully separated. Answer : (a)

Centrioles occur as paired cylindrical organelles together with pericentriolar material (PCM) in the centrosome of an animal cell. Centrioles are found as single structures in cilia and flagella in animal cells and some lower plant cells. Statementr A iis false Ribosomes are a cell structure that makes protein. Statemnet B is correct The middle lamella is a pectin layer which cements the cell walls of two adjoining plant cells together. It is the first formed layer which is deposited at the time of cytokinesis. The cell plate that is formed during cell division itself develops into middle lamella or lamellum. Statement C is false Smooth E R (SER) is associated with the production and metabolism of fats and steroid hormones. Statement D is correct Answer : (c)

Mitochondrial respiration generates a proton gradient and superoxide radicals, suggesting a possible link between oxidative stress, mitochondrial integrity, and alkaline-induced cell death. Manganese superoxide dismutase removes superoxide radicals in mitochondria, and thus protects mitochondria from oxidative injury Answer : (b)

Glycine, the simplest amino acid, obtainable by hydrolysis of proteins. Sweet-tasting, it was among the earliest amino acids to be isolated from gelatin (1820). Especially rich sources include gelatin and silk fibroin. Glycine is one of several so-called nonessential amino acids for mammals; i.e., they can synthesize it from the amino acids serine and threonine and from other sources and do not require dietary sources. The chemical structure of glycine is Answer : (a)

Presence of enzyme inhibitors slows down the rate of active transport. Answer : (b)

Mammal red blood cells (erythrocytes) contain neither nucleus nor mitochondria. Answer : (c)

There are three main components of the cytoskeleton: microtubules, intermediate filaments (IF) and microfilaments, along with many other proteins that support those components. Answer : (a)

Prokaryotic cells do not have a true nucleus that contains their genetic material as eukaryotic cells do. Instead, prokaryotic cells have a nucleoid region, which is an irregularly-shaped region that contains the cell’s DNA and is not surrounded by a nuclear envelope. prokaryotes have no mitochondria Some other parts of prokaryotic cells are similar to those in eukaryotic cells, such as a cell wall surrounding the cell (which is also found in plant cells, although it has a different composition). Answer : (c)

Lysosomes contain a wide variety of hydrolytic enzymes (acid hydrolases) that break down macromolecules such as nucleic acids, proteins, and polysaccharides Answer : (d)