NCERT Exemplar MCQs

Hint

(d) The common characteristic feature of plant sieve tubes and mammalian erythrocytes is the absence of nucleus. Sieve tubes are the component of phloem and do not contain nucleus. Similarly, erythrocytes in the mammalian cells also do not posses nucleus. Erythrocytes are the RBCs that help in gaseous exchange.

Mitochondria is absent in sieve tube cells. Pigment haemoglobin is present in mammalian erythrocytes but not in sieve tube cells. The cell wall is made of cellulose and is present in all plant cells, and thus absent in erythrocytes.

Hint

(d) They are capable of forming polyribosomes during which many ribosomes are attached to \(m R N A\). The purpose of ribosomes moving on \(m R N A\) is to synthesise proteins i.e. translation. Indeed, ribosomes have a very direct role in protein synthesis.

Hint

(b) Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, unlike prokaryotes, which have no membrane-bound organelles. Anabaena is a genus of filamentous cyanobacteria that exist as plankton. They are known for nitrogen-fixing abilities and are prokaryotes.
Euglena is a genus of single-cell flagellate eukaryotes.
Spirogyra is a filamentous chlorophyte green algae, which is also a eukaryote. Agaricus is a genus of mushrooms containing both edible and poisonous species, and are eukaryotes.

Hint

(a) The smallest cell is Mycoplasma (0.1-0.5μm).
The bacterial cell measures \(3-5 \mu \mathrm{m}\) in length.
Erythrocytes (RBCs) are 6-8 \(\mu \mathrm{m}\) in diameter.
The largest cell is the egg of an ostrich.
So, the correct answer is option “(i) \(\rightarrow\) (iv) \(\rightarrow\) (iii) \(\rightarrow\) (ii)”.

Hint

(b) Cell wall is found in bacteria (prokaryotes), fungi, algae, and plants (eukaryotes). Bacterial cell walls are made up of peptidoglycan (murein). Algal cell walls are made up of glycoproteins and polysaccharides. The cell walls of fungi are composed of chitin. Plant cell walls consist of a variety of polysaccharides, lipids, proteins, etc. Prokaryotes lack nuclear membrane and membrane-bound subcellular organelles. Genetic material is naked and is called the nucleoid.

Hint

(c) Singer and Nicolson (1972) proposed the structure of cell membrane that was widely accepted and called as fluid mosaic model which states that fluid, a native of lipids helps in the movement of protein within the membrane.

Schleiden and Schwann (1839) Observed thin outer layer in cells called plasma membrane and proposed cell theory.
Camillo Golgi (1898) discovered the Golgi apparatus.
Robert Brown (1831) discovered the nucleus in the cell which was later termed chromatin by Flemming.

Hint

(b) Rough Endoplasmic Reticulum (RER) is observed in the cells that are actively involved in the protein synthesis and secretin.
Other options are incorrect as
Golgi apparatus is present in secretary cells.
The Secretary cell has both SER and RER. SER is the major site for the synthesis of lipids.
No secretary granules are found in the nucleus.

Hint

(c) Tonoplast is a single membrane that bounds the vacuoles and separates it from the cytoplasm. In plants, tonoplasts facilitate uphill transport of many ions and other materials, making their concentration higher in vacuole than in cytoplasm

Hint

(a) A cell wall made up of peptidoglycan is found in bacteria and not in eukaryotes. Eukaryotic cell wall is made up of cellulose hemicellulose, pectin chitin, etc. Thus, is not true for the eukaryotic cell.

In eukaryotes ribosomes present in the cytoplasm is of \(80 S\) type but the ribosome in mitochondria is of \(70 S\) type, which represents the type present in prokaryotic cell.

In eukaryotes, cell organelles are highly complex and membrane-bound and the mitochondria in eukaryotes bear a separate circular DNA.

Hint

(d) Statement is false.
Carbohydrates are never found in the plasma membrane is not true. The biochemical investigation done on the cell membrane clearly demonstrate that the cell membrane possess protein and carbohydrates as biochemical components.
The other options stand true for plasma membrane
The plasma membrane is present in both plant and animal cells. Lipid is present as a bilayer and the lipid component is made of phosphoglycerides (fluid mosaic model by Singer and Nicolson).

Proteins are present integrated as well as loosely associated with the lipid bilayer. The ratio of protein and lipid varies considerably in different cell types.

Hint

(c) Presence of thylakoids, the structural elements of chloroplast, differs then (plastids) from mitochondria. Thylakoids are flattened sacs stocked one above the other to form grana. They help in photosynthesis

Rest of the features- the presence of two layers of membrane, ribosome, and presence of DNA are common to both plastids and mitochondria.

Hint

(a) A cytoskeleton is the frame that gives shape to a cell. And also it offers support, and facilitates movement through three main components:
microfilaments, intermediate filaments, and microtubules.
The cytoskeleton helps the cell move in its environment and controls the movement of all of the cell’s interior workings.