Topic 1 : The Cell NEET Style Questions - IBDP, MYP, AP, iGCSE, A-Level

Question

01 What will be the direction of flow of water when a plant cell is placed in a hypotonic solution? [NEET (Odisha) 2019]

(a) Water will flow in both directions

(b) Water will flow out of the cell

(d) No flow of water in any direction

Answer/Explanation

Ans. (c)

The behaviour of the plant cells with regard to water movement depends on the surrounding solution. When a plant cell is placed in hypotonic solution then the water will flow into the cell and the cell will swell.

Question

Which of the following organic compounds is the main constituent of lecithin? [NEET (Odisha) 2019]

(a) Arachidonic acid

(b) Phospholipid

(d) Phosphoprotein

Answer/Explanation

Ans. (b)
Phospholipids are main constituents of lecithin. These molecules are composed of choline and inositole. It is found in all living cells as a major component of cell membrane.

Question

The concept of ‘Omnis cellula-e-cellula regarding cell division was first proposed by [NEET (National) 2019]

(a) Theodor Schwann

(b) Schleiden

(d) Rudolf Virchow

Answer/Explanation

Ans. (d)

Rudolf Virchow proposed the concept of “omnis cellula-e-cellula”, i.e. all cells are derived from the pre-existing cells. Schleiden and Theodor Schwann jointly put forward the cell theory in 1839.

Question

Which one of the following elements is responsible for maintaining turgor in cells? [NEET 2018]

(a) Potassium

(b) Sodium

(d) Calcium

Answer/Explanation

Ans. (a)
Among the given elements, potassium $\left(\mathrm{K}^{+}\right)$is responsible for maintaining turgor pressure in cell because it regulates the proton pumps involved in opening and closing of stomata. Magnesium $\left(\mathrm{Mg}^{2+}\right)$ is a constituent of chlorophyll pigment which helps in photosynthesis in green plants. Calcium $\left(\mathrm{Ca}^{2+}\right)$ provides selective permeability to the cell membrane. All of these, i.e. $\mathrm{K}^{+}, \mathrm{Ca}^{2+}$ and $\mathrm{Mg}^{2+}$ are essential elements.
Sodium $\left(\mathrm{Na}^{+}\right)$is involved in membrane permeability. It is a non-essential element.

Question

Which among the following is not a prokaryote? [NEET 2018]

(a) Nostoc

(b) Mycobacterium

(d) Oscillatoria

Answer/Explanation

Ans. (c)
Among the given options, Saccharomyces is a fungus, i.e. it is a eukaryote. They possess a well defined nucleus and other cell organelles. Nostoc and Oscillatioria are cyanobacteria while Mycobacterium is a true bacterium. Cyanobacteria and bacteria both are prokaryotes as they lack a well-defined nucleus and other cell organelles.

Question

Which of the following components provides sticky character to the bacterial cell ? [NEET 2017]

(a) Cell wall

(b) Nuclear membrane

(d) Glycocalyx

Answer/Explanation

Ans. (d)

Glycocalyx is the outer most mucilage layer of the cell envelope. It gives sticky character to the bacterial cell.

Question

Select the wrong statement. [NEET 2016, Phase II]

(a) Bacterial cell wall is made up of peptidoglycan

(b) Pili and fimbriae are mainly involved in motility of bacterial cells

(d) Mycoplasma is a wall-less microorganism

Answer/Explanation

Ans. (b)

Fimbriae or pili are fine hair like appendages used by bacteria for attachment rather than motility. These are formed of protein called pilin. Pili are longer than fimbriae and are one or two per cells. Some special type of pili called sex pili are present in certain strains of bacteria which help the bacterium for forming conjugation canal during sexual reproduction by conjugation method. Fimbriae also help bacterium for cell to cell adhering and colonisation.

Question

The structures that help some bacteria to attach to rocks and/or host tissues are [CBSE AIPMT 2015]

(a) rhizoids

(b) fimbriae

(d) holdfast

Answer/Explanation

Ans. (b)
Fimbriae are small bristle like fibres sprouting out of the cell. In some bacteria, they are known to help is attachment to rocks in streams and also to the host tissues.

Question

Which of the following structure is not found in a prokaryotic cell? [CBSE AIPMT 2015]

(a) Nuclear envelope

(b) Ribosome

(d) Plasma membrane

Answer/Explanation

Ans. (a)

In a prokaryotic cell, nuclear envelope is not found. It means genetic material (DNA) is not enclosed by any envelope and lies in direct contact with the cytoplasm.

Question

A protoplast is a cell [CBSE AIPMT 2015]

(a) without plasma membrane

(b) without nucleus

(d) without cell wall

Answer/Explanation

Ans. (d)

A protoplast is a cell without cell wall. It is a plant, bacterial or fungal cell that had its cell wall completely or partially removed using either mechanical or enzymatic means.

Question

Select the correct statement from the following regarding cell membrane. [CBSE AIPMT 2012]

(a) $\mathrm{Na}^{+}$and $\mathrm{K}^{+}$ions move across cell membrane by passive transport

(b) Proteins make up 60 to $70 \%$ of the cell membrane

(d) Fluid mosaic model of cell membrane was proposed by Singer and Nicolson

Answer/Explanation

Ans. (d)

In 1972, Singer and Nicolson proposed fluid mosaic model for internal structure of plasma membrane. This is most widely accepted model for plasma membrane.
According to this model, a membrane consists of a continuous bilayer of phospholipids with their polar hydrophilic ends on the outer surfaces and two non-polar hydrohobic tails of each phospholipid molecule point inwards. The globular alpha proteins do not form continuous layer but are embedded randomly in the lipid bilayer or superficially attached.

Question

Which one of the following organisms is not an example of eukaryotic cells? [CBSE AIPMT 2011]

(a) Escherichia coli

(b) Euglena viridis

(d) Paramecium caudatum

Answer/Explanation

Ans. (a)

The bacterium E. coli is a prokaryote. It is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It is the most widely studied prokaryotic model organism.

Question

Which one of the following also acts as a catalyst in a bacterial cell? [CBSE AIPMT 2011]

(a) sn RNA

(b) hn RNA

(d) $5 \mathrm{~S} r \mathrm{RNA}$

Answer/Explanation

Ans. (c)
$23 S$ rRNA in bacteria is the enzyme ribozyme for the formation of peptide bond. $23 S$ rRNA is found in large sub-unit (70S) of ribosome of bacteria.

Question

Which one of the following structures between two adjacent cells is an effective transport pathway? [CBSE AIPMT 2010]

(a) Plasmodesmata

(b) Plastoquinones

(d) Plasmalemma

Answer/Explanation

Ans. (a)

The primary cell wall contains many small openings or pores situated in the primary pit fields. The cytoplasm of adjacent cells communicates by means of cytoplasmic bridges called plasmodesmata. The plasmodesmata permit translocation of fluid and passage of solutes between cells.

Question

The plasma membrane consists mainly of [CBSE AIPMT 2010]

(a) phospholipids embedded in a protein bilayer

(b) proteins embedded in a phospholipid bilayer

(d) proteins embedded in a carbohydrate bilayer

Answer/Explanation

Ans. (b)
According to fluid mosaic model given by Singer and Nicolson (1972), plasma membrane consists of a continuous bilayer of phospholipid molecules, in which globular proteins are embedded. This arrangement corresponds to icebergs (proteins) floating in a sea of phospholipids.
Proteins stay in the membrane because they have regions of hydrophobic amino acids which interact with fatty acid tails to exclude water. Rest of the molecule is hydrophilic, which faces into or outward, both of which are aqueous environment.

Question

Middle lamella is mainly composed of [CBSE AIPMT 2009]

(a) hemicellulose

(b) muramic acid

(d) phosphoglycerides

Answer/Explanation

Ans. (c)

The middle lamella is cementing layer between the cells. It is made up of $\mathrm{Ca}$ and Mg pectates. The basic chemical unit of pectin is galacturonic acid which have the capability of salt formation with calcium and magnesium (an acid base reaction).

Question

Plasmodesmata are [CBSE AIPMT 2009]

(a) lignified cemented layers between cells

(b) locomotory structures

(d) connections between adjacent cells

Answer/Explanation

Ans. (d)

The primary cell wall contains many small openings or pores situated in primary pit fields. The cytoplasm of adjacent cells communicates through the pores by means of cytoplasmic bridges called plasmodesmata. The plasmodesmata permit circulation of fluid and passage of solutes between cells.

Question

Keeping in view the “fluid mosaic model’ for the structure of cell membrane, which one of the following statements is correct with respect to the movement of lipids and proteins from one lipid monolayer to the other (described as flip-flop movement)? [CBSE AIPMT 2008]

(a) Both lipids and proteins can flip-flop

(b) While lipids can rarely flip-flop, proteins cannot

(d) Neither lipids, nor proteins can flip-flop

Answer/Explanation

Ans. (b)

Mobility of membrane proteins due to the fluid property of lipid bilayer was demonstrated by classical experiment of D Frye and M Edidin (1970). Lipid molecules very rarely migrate from one lipid monolayer to other monolayer of lipid bimolecular layer.
Such a type of movement is called flip-flop or transbilayer movement and occurs once a month for any individual lipid molecule. But protein can never perform flip-flop movement.

Question

A major breakthrough in the studies of cells came with the development of electron microscope. This is because [CBSE AIPMT 2006]

(a) the resolving power of the electron microscope is 200-350 nm as compared to 0.1-0.2 for the light. microscope

(b) electron beam can pass through thick materials, whereas light microscopy required thin sections

(c) the electron microscope is more powerful than the light microscope as it uses a beam of electrons which has wavelength much longer than that of photons

(d) the resolution power of the electron microscope is much higher than that of the light microscope

Answer/Explanation

Ans. (d)

The resolution power of the electron microscope is much higher than that of the light microscope.
As an average the resolving power of a light microscope is $0.25 \mu \mathrm{m}-0.3 \mu \mathrm{m}$ while that of electron microscope is 2-10Å though theoritically, it is $0.25 \AA$. The magnification range of light microscope is $2000-4000$ while of electron microscope is $100000-300000$.

Question

According to widely accepted ‘fluid mosaic model’, cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several respects. In this regard, which of the following statements is incorrect? [CBSE AIPMT 2005]

(a) Proteins in cell membranes can travel within the lipid bilayer

(b) Proteins can also undergo flip-flop movements in the lipid bilayer

(d) Many proteins remain completely embedded within the lipid bilayer

Answer/Explanation

Ans. (b)

Statement (b) is incorrect because flip-flop or transmembrane movement is due to the migration of lipid molecules from one lipid monolayer to other monolayer of lipid bilayer.

Question

A student wishes to study the cell structure under a light microscope having $10 X$ eyepiece and $45 X$ objective. He should illuminate the object by which one of the following colours of light so as to get the best possible resolution? [CBSE AIPMT 2005]

(a) Blue

(b) Green

(d) Red

Answer/Explanation

Ans. (a)

Resolving power or resolution is the ability of the lens to distinguish fine details and structure. Specifically, it refers to the ability of the lenses to distinguish between two points a specified distance apart. Resolving power depends on two factors :
(a) Wavelength of light used for illumination.
(b) Power of objective lenses.
Resolving power $=\frac{\text { Wavelength of light }}{2 \times \text { NA }}$
Since, the limit of resolving power a microscope is fixed by the structure of light, the shortest wavelength of visible light will give the maximum resolution. Among yellow, green, red and blue light colour. Blue $(500 \mathrm{~nm})$ have shortest wavelength so, it will give best resolution.

Question

The main difference in Gram (+)ve and Gram (-)ve bacteria resides in their [CBSE AIPMT 1990, 2001]

(a) cell wall

(b) cell membrane

(d) flagella

Answer/Explanation

Ans. (a)

Gram stain is a differential stain that differentiates bacteria into two groups – Gram +ve and Gram-ve. The basis of this differentiation lies in the composition (lipid contents) and thickness of cell wall of these bacteria. Bacteria are called Gram +ve, if they retain the crystal violet colour even after alcohol washing. Whereas, cell wall of Gram -ve bacteria is thin, rich in lipids and decolourise the crystal violet colour of Gram stain.

Question

In ‘fluid mosaic model’ of plasma membrane, [CBSE AIPMT 2002]

(a) upper layer is non-polar and hydrophilic

(b) upper layer is polar and hydrophobic

(d) proteins form a middle layer

Answer/Explanation

Ans. (c)

According to the fluid mosaic model, the cell membrane consists of a highly viscous fluid matrix of two layers of phospholipid molecules. Protein molecules (or their complexes) occur in membrane but not in continuous layer.

Question

DNA is mainly found in [CBSE AIPMT 1999]

(a) nucleus

(b) cytoplasm

(d) nucleolus

Answer/Explanation

Ans. (a)

Most of the amount of DNA is found in nucleus. Though some amount of DNA is found in chloroplast and mitochondria also.

Question

The eukaryotic genome differs from the prokaryotic genome because [CBSE AIPMT 1999]

(a) DNA is complexed with histones in prokaryotes

(b) repetitive sequences are present in eukaryotes

(d) DNA is circular and single stranded in prokaryotes

Answer/Explanation

Ans. (b)

A major component $(20-50 \%)$ of the eukaryotic genome consists of DNA which does not code for any protein. This portion consists of certain base sequences which are repeated many times (hence, called repetitive DNA). DNA of prokaryotes does not contain histones nor it is single stranded.

Question

Which is correct about cell theory in view of current status of our knowledge about cell structure? [CBSE AIPMT 1993]

(a) It needs modification due to discovery of subcellular structures like chloroplasts and mitochondria

(b) Modified cell theory means that all living beings are composed of cells capable of reproducing

(d) Cell theory means that all living objects consist of cells whether or not capable of reproducing

Answer/Explanation

Ans. (c)

Cell theory proposed by Schleiden and Schwann states that all living organisms whether animal or plants are made up of cells and have similar organisation. It is the basic unit of structure and function. Exception to cell theory are the viruses, mycoplasma, viroids, bacteria which are acellular organisms, i.e. lacks cellular organisations. Moreover, coenocytic forms like Paramecium, Rhizopus, have more than one nuclei and are exception to cell theory.

Question

Name of Schleiden and Schwann are associated with [CBSE AIPMT 1993]

(a) protoplasm as the physical basis of life

(b) cell theory

(d) nucleus functions as control center of cell

Answer/Explanation

Ans. (b)

Matthias J Schleiden(a German botanist, 1938). Theodor Schwann (1939), a German zoologist in 1939. jointly proposed the cell theory.

Question

Cell recognition and adhesion occur due to biochemicals of cell membranes named [CBSE AIPMT 1993]

(a) proteins

(b) lipids

(d) glycoproteins and glycolipids

Answer/Explanation

Ans. (d)

In the cell membrane, oligosaccharides do not occur freely but are attached to the external surface of phospholipids and proteins forming glycolipids and glycoproteins respectively. They form cell coat (glycocalyx) which acts as recognition centre, site for attachment and provides antigen specificity to cell membranes, blood grouping and matching of tissues in transplantation of organs.

Question

Genophore/bacterial genome or nucleoid is made of [CBSE AIPMT 1993]

(a) histones and non-histones

(b) RNA and histones

(d) a single stranded DNA

Answer/Explanation

Ans. (c)

Genophore refers to nucleoid or bacterial genome, made of single, double stranded DNA. It is supercoiled with the help of RNA and polyamines forming a circular genetic material complex.

Question

Balbiani rings (puffs) are sites of [CBSE AIPMT 1993]

(a) DNA replication

(b) RNA and protein synthesis

(d) synthesis of lipids

Answer/Explanation

Ans. (b)

In polytene chromosomes (salivary gland chromosomes). Large swellings are called puffs or Balbiani rings, named after their discoverer. In such rings,
DNA is active, uncoiled for rapid transcription of RNA or protein synthesis.

Question

Angstrom $(Å)$ is equal to [CBSE AIPMT 1992]

(a) $0.01 \mu \mathrm{m}$

(b) $0.001 \mu \mathrm{m}$

(d) $0.00001 \mu \mathrm{m}$

Answer/Explanation

Ans. (c)

Angstrom $(Å)=0.0001 \mu \mathrm{m}$
$1 Å=10^{-10} \mathrm{M}=10^{-8} \mathrm{~cm}=10^{-7} \mathrm{~mm}=10^{-4} \mu$.

Question

Addition of new cell wall particles amongst the existing ones is [CBSE AIPMT 1991]

(a) deposition

(b) apposition

(d) aggregation

Answer/Explanation

Ans. (b)

Apposition or accretion is defined as the addition of new cell wall particles amongst the existing one, such as deposition of secondary walls in layers from outside over the existing primary wall.
Intussusception can be demonstrated as the internal growth of the primary wall which occurs during the growth period of the cell resulting in the increase in volume of cell wall.
Deposition Molecules settling out of a solution.
Aggregation Direct mutual attraction between particles or Aggregation of soil granules to form soil structure.

Question

Resolution power is the ability to [CBSE AIPMT 1991]

(a) distinguish two trees

(b) distinguish two close objects

(d) magnify image

Answer/Explanation

Ans. (b)

Resolution power is the ability of a microscope to distinguish between two points that are closely situated, i.e. the smallest distance by which two objects lying closely can be separated. Higher resolution makes image clear.

Question

Cell wall shows [CBSE AIPMT 1991]

(a) complete permeability

(b) semi-permeability

(d) impermeability

Answer/Explanation

Ans. (a)

Cell wall is the structural, functional and heritable unit of living organisms. It is non-living, porous, permeable, inert, hydrophilic, inelastic, rigid, semi-transparent protective covering around the plasmalemma.

Question

Fluid mosaic model of cell membrane was put forward by [CBSE AIPMT 1991]

(a) Danielli and Davson

(b) Singer and Nicolson

(d) Watson and Crick

Answer/Explanation

Ans. (b)

Fluid mosaic model of plasma membrane was proposed by SJ Singer and GL Nicolson (1972).

Question

Magnification of compound microscope is not connected with [CBSE AIPMT 1990]

(a) numerical aperture

(b) focal length of objective

(d) tube length

Answer/Explanation

Ans. (a)

Magnification is the power of enlargement. It is the ratio of the size of an object seen under microscope to the actual size observed without microscope. Magnification depends on focal length of lenses and length of body tube.
It does not depend on numerical aperture of objective lens and the nature of light being used for illumination. The total magnification of a microscope is determined by multiplying the magnifying power of the objective lens by that of the eye piece.

Question

Electron microscope has a high resolution power. This is due to [CBSE AIPMT 1990, 92]

(a) electromagnetic lenses

(b) very low wavelength of electron beam

(d) high numerical aperture of glass lenses used

Answer/Explanation

Ans. (b)

Resolving power is defined as the ability of an optical system or objective lens to distinguish two closely placed points as two distinct separate points. It depends on wavelength of light and numerical aperture, as limit of resolution $\left(L_m\right)=\frac{0.61 \lambda}{\text { NA }}$. In electron microscope, higher resolution is provided by the low wavelength of electrons.

Question

Plasma membrane is made up of [CBSE AIPMT 1989]

(a) proteins and carbohydrates

(b) proteins and lipids

(d) proteins, some nucleic acid and lipids

Answer/Explanation

Ans. (c)

Plasma membrane is living, quasifluid, trilaminar membrane, usually consists of proteins $(44-76 \%)$, lipids $(20-53 \%)$. water $(20 \%)$ and carbohydrates (1-8\%).

Question

Nucleoproteins are synthesised in [CBSE AIPMT 1989]

(a) nucleoplasm

(b) nuclear envelope

(d) cytoplasm

Answer/Explanation

Ans. (d)
Nucleoproteins are the conjugated proteins. These include ribonucleoproteins and occur in ribosomes. Deoxyribonucleoproteins occur in chromosomes.

Question

According to fluid mosaic model, plasma membrane is composed of [CBSE AIPMT 1988]

(a) phospholipids and oligosaccharides

(b) phospholipids and hemicellulose

(d) phospholipids, extrinsic proteins and intrinsic proteins

Answer/Explanation

Ans. (d)

In fluid mosaic model lipid bilayer is composed of phospholipids with their polar hydrophilic ends on the outer surfaces and two non-polar hydrophobic tails of each phospholipid molecule point inwards. The globular alpha proteins do not form continuous layer but are embedded irregularly in the lipid bilayer (called integral or intrinsic proteins) or superficially attached (extrinsic or peripheral proteins).

Question

Element necessary for the middle lamella [CBSE AIPMT 2001]

(a) $\mathrm{Ca}$

(b) $\mathrm{Zn}$

(d) $\mathrm{Cu}$

Answer/Explanation

Ans. (a)

Presence of cell wall is the characteristic feature of all plant cells. Cell wall consisted of three layers, middle lamella or middle layer, primary layer and secondary layer. The position of middle lamella is between two primary walls of different cells and thus functions as cementing layer between these two cells. Main constituents of middle lamella are calcium and magnesium pectate.

Question

In plants, inulin and pectin are [CBSE AIPMT 2001]

(a) reserve materials

(b) wastes

(d)insect-attracting material

Answer/Explanation

Ans. (a)
Inulin a polymer of fructose, is used as a stored food, particularly in roots and tubers of family-Compositae. Pectin is a mucopolysaccharide which is found in cell wall of plants. During the time of fruit ripening, the pectin hydrolyses and gives rise to the constituents of sugar.

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