Biology: Topic-wise Test- 1 - NEET MCQ

The anther is the part of the stamen (male reproductive organ of a flower) responsible for producing pollen grains. Pollen grains contain the male gametes necessary for the fertilization of the ovules.

Line in NCERT: "Each anther is usually bilobed and each lobe has two chambers, the pollen-sacs. The pollen grains are produced in pollen-sacs."

Size and shape of the cells vary with the functions they perform. In unicellular organism a single cell constitutes the entire organism. The components in all eukaryotic cells are more/less the same. Centrioles are present in animal cells but absent in plant cells.

Plasma membrane is a selectively permeable membrane and allows only those particles that protect the cell. Movement of air and water takes place through diffusion and osmosis respectively. Osmosis and diffusion are examples of passive transport. Active transport takes place through use of energy.

Topic in NCERT: Transport Mechanisms in Cells

Line in NCERT: Many molecules can move briefly across the membrane without any requirement of energy and this is called the passive transport. Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient, i.e., from higher concentration to the lower. Water may also move across this membrane from higher to lower concentration. Movement of water by diffusion is called osmosis.

Plasma membrane is made of lipids and proteins. Lipids with hydrophobic and hydrophilic end are called amphipathic lipids. The plasma membrane is a lipid bilayer membrane. Integral proteins are not just present on the surface of the membrane but span along the entire width of the membrane.

Line in NCERT: "Depending on the ease of extraction, membrane proteins can be classified as integral and peripheral. Peripheral proteins lie on the surface of membrane while the integral proteins are partially or totally buried in the membrane."

Mitochondria and chloroplast contain theirown genetic material. Genetic material is mainly present in nucleus of the cell but these two cell organelles also contain own genetic material.

Topic in NCERT: CYTOKINESIS

Line in NCERT: "At the time of cytoplasmic division, organelles like mitochondria and plastids get distributed between the two daughter cells."

Pleuro Pneumonia Like Organisms (PPLOs) also called mycoplasma are considered as smallest free living organism. It do not contain cell membrane or cell wall and present as fluid. It causes disease in plants.

Topic in NCERT: CELL: THE UNIT OF LIFE

Line in NCERT: "The smallest cells, mycoplasmas, are only 0.3 µm in length while bacteria could be 3 to 5 µm."

Cell cycle involves duplication of the genome, division of the parent cell into two daughter cells, synthesis of cell organelles for the daughter cells, but centrosomes are not degenerated.

Line in NCERT: "Cell cycle is divided into two phases called (i) Interphase – a period of preparation for cell division, and (ii) Mitosis (M phase) – the actual period of cell division."

Parietal:

• This type of placentation is found in the unilocular syncarpous ovary. In it, the ovule develops on the inner wall of the ovary or on the peripheral part.
• Ovary becomes bi or multilocular due to the formation a false septum.
• For example, Cucurbita, Argemone and Cruciferae family (Mustard). 

Axile:

• It is found in multicarpellary syncarpous gynoecium. The fusion margin of carpels grows inward and meets in the centre of the ovary.
• Thus, an axis forms in the centre of the ovary and the ovary becomes multi-chambered. The ovules are borne at the central axis.
• A number of these chambers are equal to the number of the carpel.
• For example,  Potato, China rose, Onion, Lemon, Orange, Tomato.

Some roots, called adventitious roots, arise from an organ other than the root—usually a stem, sometimes a leaf. They are especially numerous on underground stems, such as rhizomes, corms, and tubers, and make it possible to vegetatively propagate many plants from stem or leaf cuttings.

Line in NCERT: "In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots."

All cells are surrounded by a plasma membrane. The membrane is composed of a phospholipid bilayer arranged back-to-back. The membrane is also covered in places with cholesterol molecules and proteins. The plasma membrane is selectively permeable and regulates which molecules are allowed to enter and exit the cell.

Line in NCERT: "Phospholipids contain, in addition, a phosphorylated nitrogenous compound."

Desmosomes (macula adherens) consists of intercellular thrckening matedals, disc-shaped intracellular thickening adjacent to each membrane with tonofibrils. These act as intercellular cementing material, adhere cells together at places like spot welding.

Morphological and biochemical studies indicate that plasma membranes (PM) are derived from nuclear membranes (NM) or endoplasmic reticulum (ER) via the Golgi apparatus (GA) by a process of membrane flow and differentiation.According to this concept, membranes are transferred and transformed along a chain of cell components in a subcellular developmental pathway.

Line in NCERT: "The golgi apparatus principally performs the function of packaging materials, to be delivered either to the intra-cellular targets or secreted outside the cell."

• The endoplasmic reticulum (smooth and rough) is an interconnected network of flattened, membrane-enclosed sacs or tube-like structure which are evenly distributed throughout the cytoplasm.
• It forms a continuous membrane system with the nuclear membrane which are the extensions of the infolded plasma membrane.

Line in NCERT: "The endomembrane system include endoplasmic reticulum (ER), golgi complex, lysosomes and vacuoles."

The Golgi apparatus plays a crucial role in the packaging and modification of proteins. Proteins synthesized in the rough endoplasmic reticulum are transported to the Golgi apparatus, where they are modified, sorted, and packaged into vesicles for transport to their destination within or outside the cell.

Line in NCERT: "The golgi apparatus principally performs the function of packaging materials, to be delivered either to the intra-cellular targets or secreted outside the cell."

The synaptonemal complex (SC) is a protein structure that forms between homologous chromosomes (two pairs of sister chromatids) during meiosis and is thought to mediate chromosome pairing, synapsis, and recombination.

Topic in NCERT: Prophase I

Line in NCERT: "Electron micrographs of this stage indicate that chromosome synapsis is accompanied by the formation of complex structure called synaptonemal complex."

Telophase I, is followed by an interphase, called interkinesis, similar to the mitoticinter phase. During interkinesis the chromatin is partially uncoiled; however, there is no replication of the genetic material, because each chromosome already consists of two chromatids.

Line in NCERT: "The stage between the two meiotic divisions is called interkinesis and is generally short lived."

The two homologous chromosomes do not completely separate but remain attached together at one or more points as indicated by X arrangements known as Chiasmata.The displacement of Chiasmata is termed as terminalization.Terminalization is completed in Diakinesis stage.

Line in NCERT: "The final stage of meiotic prophase I is diakinesis. This is marked by terminalisation of chiasmata."

Because during metaphase, all the chromosomes lined up on the metaphase plate and further proceeding anaphase. So it is easy to count them at that stage by counting the number of functional centromere. Because the number of chromosomes = count the number of functional centromere.

Line in NCERT: "The complete disintegration of the nuclear envelope marks the start of the second phase of mitosis, hence the chromosomes are spread through the cytoplasm of the cell. By this stage, condensation of chromosomes is completed and they can be observed clearly under the microscope. This then, is the stage at which morphology of chromosomes is most easily studied."

Prophase I is divided into five sub-phases: leptotene, zygotene, pachytene, diplotene and diakinesis. Another sub-phase called preleptonema is sometimes recognized prior to leptonema.

Line in NCERT: "Prophase I: Prophase of the first meiotic division is typically longer and more complex when compared to prophase of mitosis. It has been further subdivided into the following five phases based on chromosomal behaviour, i.e., Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis."

The structure for hemoglobin is very similar to myoglobin except that it has a quaternary structure due to the presence of four protein chain subunits.Each protein chain subunit contains a heme group with the iron attached. Each hemoglobin molecule can bind to a total of four oxygen molecules.

Topic in NCERT: quaternary structure of proteins

Line in NCERT: "Some proteins are an assembly of more than one polypeptide or subunits. The manner in which these individual folded polypeptides or subunits are arranged with respect to each other ... is the architecture of a protein otherwise called the quaternary structure of a protein.Adult human haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits of α type and two subunits of β type together constitute the human haemoglobin (Hb).

The protienous part of an enzyme is known as apoenzyme.

Line in NCERT: "Enzymes are composed of one or several polypeptide chains. However, there are a number of cases in which non-protein constituents called co-factors are bound to the enzyme to make the enzyme catalytically active. In these instances, the protein portion of the enzymes is called the apoenzyme."

A small Km indicates that the enzyme requires only a small amount of substrate to become saturated. Hence, the maximum velocity is reached at relatively low substrate concentrations. A large Km indicates the need for high substrate concentrations to achieve maximum reaction velocity.

Line in NCERT: "With the increase in substrate concentration, the velocity of the enzymatic reaction rises at first. The reaction ultimately reaches a maximum velocity (Vmax) which is not exceeded by any further rise in concentration of the substrate."

Aestivation is the term used for the mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl. It describes how the floral parts are folded or overlapped in the bud stage, which can be valvate, twisted, imbricate, or vexillary.

Line in NCERT: "Aestivation: The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation."

In the floral formula, "G(2)" represents a bicarpellary, syncarpous gynoecium, indicating that the flower has two carpels that are fused together. This part of the formula provides information about the structure and organization of the female reproductive part of the flower.

Topic in NCERT: Gynoecium

Line in NCERT: The floral formula is represented by some symbols. In the floral formula, Br stands for bracteate K stands for calyx , C for corolla, P for perianth, A for androecium and G for Gynoecium, G for superior ovary and G for inferior ovary, for male, for female, for bisexual plants, ⊕ for actinomorphic and for zygomorphic nature of flower. Fusion is indicated by enclosing the figure within bracket and adhesion by a line drawn above the symbols of the floral parts. A floral diagram provides information about the number of parts of a flower, their arrangement and the relation they have with one another . The position of the mother axis with respect to the flower is represented by a dot on the top of the floral diagram

First heart sound is LUBB, produced at the beginning of ventricular systole due to closing of tricuspid and bicuspid valve and it is a dull sound for long period while second heart sound is DUPP produced at the beginning of ventricular diastole due to closing of semilunar valves and it is sharp sound for short period

Line in NCERT: "The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves."

The assertion is true as in monocotyledonous plants, the primary root is indeed short-lived and is replaced by a fibrous root system originating from the base of the stem. The reason is also true and correctly explains the assertion because the fibrous root system provides a more extensive network for efficient water and nutrient absorption from the soil.

Line in NCERT: "In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots. These roots originate from the base of the stem and constitute the fibrous root system."

Ribosomes play a critical role in protein synthesis. They are the sites where genetic information encoded in messenger RNA (mRNA) is translated into proteins. Ribosomes can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum, forming the rough ER.

Line in NCERT: "Ribosomes are the site of protein synthesis."

The assertion is true as roots in some plants are indeed modified to perform additional functions beyond their primary roles of absorption and conduction. The reason accurately explains the assertion by listing examples of such modifications, including storage of food (e.g., in carrots), providing support (e.g., prop roots in banyan trees), and aiding in respiration (e.g., pneumatophores in mangroves).

Line in NCERT: "The roots in some plants get modified for storage of food, mechanical support and respiration."

Hormones act as intercellular messengers. They are produced by endocrine glands and regulate various physiological processes by carrying messages from one part of the body to another, ensuring proper functioning and coordination among organs.

Line in NCERT: "Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts."

The pituitary gland is often referred to as the "master endocrine gland" because it secretes hormones that regulate the functions of other endocrine glands, thereby playing a crucial role in the endocrine system.

Line in NCERT: "The pituitary gland is often called the 'master endocrine gland' because it regulates the functions of other endocrine glands."