Cell: The Unit of Life

Name the following:

1. The kind of microscope that consists of a single biconvex lens.
2. The kind of mirror used for throwing light on the object in Hooke's microscope.

Answer

1. Simple microscope
2. Concave mirror

What is the maximum magnification that can usually be achieved by

1. A compound microscope
2. An electron microscope?

Answer

1. 2000 times
2. 200,000 times

Name the following:

1. Any two one-celled organisms.
2. The longest cells in animals.
3. Amoeboid cells in humans.
4. Shape of white blood cells.

Answer

1. Bacteria, Amoeba
2. Nerve cells
3. White blood cells
4. Amoeboid

A large surface area/volume ratio of the cells ensure a greater diffusion of certain substances into the cell. Name such substances.

Answer

Nutrients, metabolic wastes, respiratory gases.

Name the part of cell in which

1. Many chemical reactions occur with the help of enzymes.
2. A network of chromatin fibres occurs.
3. Cellulose forms the main component.

Answer

1. Cytoplasm
2. Nucleoplasm
3. Cell Wall

Differentiate between

1. An organ and an organelle
2. A plant cell and an animal cell pertaining to the presence of plastids.

Answer

1. Difference between an organ and an organelle:

2. A plant cell has plastids while an animal cell does not have plastids.

Name the cell organelles concerned with

1. Secretion of enzymes
2. Trapping of solar energy
3. Synthesis of proteins
4. Intracellular digestion
5. Production of ATP

Answer

1. Golgi complexes and Dictyosomes
2. Chloroplasts
3. Ribosomes
4. Lysosomes
5. Mitochondria

Name the cell organelle/component which is

1. Composed of cellulose
2. Formed of an irregular network of tubular double membranes
3. A clear space with water or other substances in solution
4. Visible only in cell division stages

Answer

1. Cell wall
2. Endoplasmic Reticulum
3. Vacuoles
4. Chromosomes

Mention if the following statements are true or false. If false, suggest the change in the information underlined.

1. Prokaryotic cells have larger ribosomes.
2. Eukaryotic cells have mitochondria.
3. Amoeba is an example of Prokaryotes.
4. Nuclear membrane is present in bacteria.

Answer

1. False
   Corrected Statement— Prokaryotic cells have smaller ribosomes.
2. True
3. False
   Corrected Statement— Amoeba is an example of Eukaryotes.
4. False
   Corrected Statement— Nuclear membrane is absent in bacteria.

Column I lists a few activities of living organisms and column II the activity of cells related to them. Match the items in the two columns.

Answer

Which cell organelle is the key to the life of the cell?

Answer

The Nucleus is the key to the life of the cell.

How do you say that a cell also has a life span and death like an organism? Give one example.

Answer

The cells behave like an organism. They carry out all the processes like an organism viz. respiration and elimination of wastes. They also have a life span like an organism. They grow, age, deteriorate and finally die. The dying cells are dissolved or destroyed by their own lysosomes. For example, Red blood cells of our body die after 120 days. These cells are continuously replaced by new cells in our body

All organisms excrete. Does an individual cell also do it? Give one example

Answer

Yes, an individual cell also excretes like an organism. Most of the waste substances are digested by the Lysosomes. Some cells may also release the waste product out through their cell membrane.

Every organism needs food. Does a cell also need it? Explain very briefly.

Answer

Yes, a cell also needs food for carrying out different processes. The food in the form of Glucose is broken down during respiration inside the mitochondria to release energy (ATP).

All life starts as-

1. an egg
2. a single cell
3. a gene
4. a chromosome

Answer

a single cell

Reason — A cell is smallest living entity. Therefore, All life starts as a single cell.

Which one of the following is found both in cells of a mango plant and a monkey?

1. chloroplasts
2. centrioles
3. cell wall
4. cell membrane

Answer

cell membrane

Reason — Cell membrane is found in both animal and plant cell. The plant cell also has a cell wall, additional to cell membrane.

Which one of the following cell organelles is correctly matched with its function?

1. Ribosomes — Synthesis of proteins
2. Mitochondria — Secretion of enzymes
3. Plasma Membrane — Freely permeable
4. Centrosome — Carries genes

Answer

Ribosomes — Synthesis of proteins

Reason — The function of the ribosomes is synthesis of proteins.

A plant cell can be identified from an animal cell by the:

1. Absence of centrosome
2. Presence of cell membrane
3. Presence of vacuoles
4. None of the above

Answer

Absence of centrosome

Reason — Centrosomes are only found in animal cells.

Plant cell has a cell wall made of-

1. Protein
2. Fructose
3. Cellulose
4. Fatty acids

Answer

Cellulose

Reason — The cell wall is made up of cellulose (a non living substance).

The cell organelle that helps in respiration of the cell is-

1. Mitochondria
2. Lysosome
3. Ribosome
4. Centrosome

Answer

Mitochondria

Reason — Mitochondria is the organelle responsible for breaking of glucose molecule to release energy.

Which of the following organelles is involved in the formation of the acrosome of a sperm?

1. Dictyosome
2. Centrosome
3. Lysosome
4. Golgi apparatus

Answer

Golgi apparatus

Reason — Golgi apparatus contains certain hydrolytic enzymes which helps to break the outer membrane of ovum.

Which part of the nucleus participates in protein synthesis?

1. Nuclear membrane
2. Nucleolus
3. Nuclear pore
4. Nucleoplasm

Answer

Nucleolus

Reason — Nucleolus helps in Ribosomal RNA formation after which protein synthesis is done by ribosomes.

The pigment which is not found in plastids is:

1. Xanthophyll
2. Carotene
3. Anthocyanin
4. Chlorophyll

Answer

Anthocyanin

Reason — Anthocyanin is not associated with plastids; instead they remain dissolved in the cell sap.

The tubules of Golgi Complexes are technically termed as:

1. Cisternae
2. Microtubules
3. Cristae
4. Vesicles

Answer

Cisternae

Reason — Hollow tubular structure of Golgi Complexes are known as Cisternae.

The invention of the microscope was a great boon for people to study smaller objects or micro-organisms. Scientists made different microscopes by using different types of lenses for magnification.
Gaurav made a table of two scientists and the kind of microscope they invented.

Identify P and Q

1. P — Simple microscope, Q — Compound microscope.
2. P — Electron microscope, Q — Simple microscope.
3. P — Compound microscope, Q — Electron microscope.
4. P — Compound microscope, Q — Simple microscope.

Answer

P — Compound microscope, Q — Simple microscope.

Reason — Compound microscope was invented by Robert Hooke and simple microscope was invented by Antony Van Leeuwenhoek.

Assertion (A): Ribosomes are considered as the 'delivery system of the cell'.

Reason (R): Delivery system is concerned with the secretions of the cell including enzymes, hormones, etc.

1. A is True and R is False.
2. A is False and R is True.
3. Both A and R are True.
4. Both A and R are False.

Answer

Both A and R are False.

Reason — Ribosomes are not the delivery system, they are the site of protein synthesis in the cell. Golgi apparatus is concerned with the secretions of the cell including enzymes, hormones, etc.

Assertion (A): Leukoplasts are colourless plastids as they have no pigments.

Reason (R): Leukoplasts are normally found in the non-photosynthetic parts of a plant.

1. A is True and R is False.
2. A is False and R is True.
3. Both A and R are True.
4. Both A and R are False.

Answer

Both A and R are True.

Reason — Leukoplasts are colourless plastids because they lack pigments. Their function is to store starch, oils, or proteins and they are not involved in photosynthesis.

Assertion (A): Cisternae are the finger-like projections arising from the inner walls of mitochondria.

Reason (R): These projections increase the surface area of the inner membrane and help in the production of ATP.

1. A is True and R is False.
2. A is False and R is True.
3. Both A and R are True.
4. Both A and R are False.

Answer

A is False and R is True.

Reason — The finger-like projections inside mitochondria are called cristae, not cisternae. Cristae increase the surface area of the inner mitochondrial membrane, which helps in ATP production.

Assertion (A): Euglena is an example of a prokaryotic cell as it is unicellular.

Reason (R): Prokaryotes are microscopic organisms with a well-defined nucleus.

1. A is True and R is False.
2. A is False and R is True.
3. Both A and R are True.
4. Both A and R are False.

Answer

Both A and R are False.

Reason — Euglena is a unicellular eukaryotic organism because it has a well-defined nucleus and membrane-bound organelles. Prokaryotes (like bacteria) do not have a well-defined nucleus.

Assertion (A): Chromosomes carry hereditary information from parents to offspring.

Reason (R): Chromosomes are suspended in the cytoplasm of each cell whether its a plant cell or an animal cell. Chromosomes are composed of RNA threads.

1. A is True and R is False.
2. A is False and R is True.
3. Both A and R are True.
4. Both A and R are False.

Answer

A is True and R is False.

Reason — Chromosomes carry hereditary information in the form of genes, which are passed from parents to offspring. Chromosomes are located in the nucleus, not suspended in the cytoplasm. They are made up of DNA and proteins not RNA.

Given below is the structure of nucleus of a cell. Read the information below the diagram and fill in the blanks:

Nucleus is the most important part of the cell. It is located in the central area in animal cells but pushed towards the periphery in plant cells due to the presence of a large vacuole in the centre. It regulates and coordinates various life processes of the cell and also plays an important role in cell division.

Nucleus has a delicate, protective surrounding layer (a) ............... which is filled with a relatively dense fluid (b) ............... . There are certain thread-like structures suspended in the fluid called (c) ............... . These thin thread-like fine structures become thick and ribbon-like during the time of cell division. These prominent ribbon-like structures are called (d) ............... .Nucleus contains a spherical, dense body inside it, called as (e) ............... which participates in protein synthesis.

Answer

Nucleus has a delicate, protective surrounding layer (a) Nuclear membrane which is filled with a relatively dense fluid (b) Nucleoplasm. There are certain thread-like structures suspended in the fluid called (c) Chromatin. These thin thread-like fine structures become thick and ribbon-like during the time of cell division. These prominent ribbon-like structures are called (d) Chromosomes. Nucleus contains a spherical, dense body inside it, called as (e) Nucleolus which participates in protein synthesis.

Given below is the structure of a plant cell. Match the structures marked (a) to (e) with the clues given for each: Example : (f) : Synthesis and secretion of enzymes,hormones, etc.

Answer

Name the part of the cell concerned with the following?

1. Liberation of energy
2. Synthesis of proteins
3. Transmission of heredity characters from parents to offspring
4. Initiation of cell division
5. Hydrolytic in function
6. Entry of only certain substances into and out of the cell.

Answer

1. Mitochondria
2. Ribosomes
3. Chromosomes
4. Centrosome
5. Lysosomes
6. Plasma membrane/cell membrane

State whether the following statements are true (T) or false (F):

(a) All animal cells contain a cell wall.

(b) The cell wall is made of protein.

(c) Centrosome occurs in animal cells.

(d) Plant cells contain large vacuoles.

(e) Protoplasm is the part of the cell which surrounds the nucleus.

(f) Genes are located in chromosomes.

(g) Anthocyanin are the pigments of flowers, which are dissolved in cell-sap.

Answer

(a) False
Corrected statement — All plant cells contain a cell wall.

(b) False
Corrected statement — The cell wall is made of cellulose.

(c) True

(d) True

(e) False
Corrected statement — Cytoplasm is the part of the cell which surrounds the nucleus.

(f) True

(g) False
Corrected statement — Anthocyanin are the pigments of fruits, which are dissolved in cell-sap.

How many chromosome pairs are found in human cells?

Answer

23 pairs of chromosome are found in human cells.

What is the name of the chemical substance which constitutes the genes?

Answer

The chemical substance constituting the genes is DNA. It stands for de-oxy ribonucleic acid.

Match the items in column ‘A’ with those in column ‘B’

Answer

Fill in the blanks

1. ............... consists of membranous sacs and secretes 40 types of digestive enzymes.
2. ............... is surrounded by microtubules, located near the nucleus.
3. Very thin flexible, living membrane which is differently permeable, is called ............... .
4. More than 1000 chromosomes are found in the nucleus of certain ...............
5. ............... are heredity units.
6. ............... is a plastid which stores starch.

Answer

1. Lysosomes consists of membranous sacs and secretes 40 types of digestive enzymes.
2. Centriole is surrounded by microtubules, located near the nucleus.
3. Very thin flexible, living membrane which is differently permeable, is called Plasma membrane.
4. More than 1000 chromosomes are found in the nucleus of certain Insects.
5. Genes are heredity units.
6. Leucoplast is a plastid which stores starch.

Write the full forms of the following abbreviations:

1. DNA
2. RNA
3. ATP
4. SER
5. RER

Answer

1. DNA — Deoxyribonucleic acid
2. RNA — Ribonucleic acid
3. ATP — Adenosine triphosphate
4. SER — Smooth endoplasmic reticulum
5. RER — Rough endoplasmic reticulum

Name the plastid and pigment likely to be found in the cells of

1. Petals of sunflower
2. Ripe tomato
3. Skin of green mango
4. Cells of potato

Answer

1. petals of sunflower — chromoplast
2. ripe tomato — anthocyanin
3. skin of green mango — chlorophyll
4. cells of potato — no pigment

Define the terms:

1. Cell organelles
2. Cell inclusions
3. Cytosol
4. Cell sap
5. Cytoplasm

Answer

1. The part of cell having a definite structure and a definite function is called Cell organelle.
2. Various non-living substances like nutrients or pigments present in the cell are called Cell inclusions.
3. The liquid found inside the cell in which various organelles are found, is called Cytosol.
4. The watery solution present in the vacuoles is called Cell sap.
5. The semi-liquid substance that fills most of the part of cell (except nucleus) within the cell membrane is called Cytoplasm.

Write the exact locations of each of the following:

1. Centrosome
2. Chromosome
3. Genes
4. Mesosome
5. Plasmid

Answer

1. Centrosome - near nucleus (only in animal cells)
2. Chromosome - in nucleus
3. Genes - on chromosomes
4. Mesosome - Plasma membrane of bacterial cells
5. Plasmid - Cytoplasm of bacterial cells

Mention three features found only in plant cells and one found only in animal cells.

Answer

Three features found only in plant cells are:

1. Presence of cell wall.
2. Presence of large vacuole.
3. Presence of plastids.

One feature only found in animal cell is presence of centrosome.

Why are the cells generally of a small size?

Answer

Cells are generally so little so that they can maximize their ratio of area to volume. They have to be ready to get the nutrients in and therefore the waste out quickly.The important point is that the area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a particular limit, not enough material is going to be ready to cross the membrane fast enough to accommodate the increased cellular volume. That's why cells are so small.

It is said that the protoplasm cannot be analysed chemically. Why?

Answer

The protoplasm cannot be analysed chemically because it has complex organic and living cell organelles which can disintegrate if chemicals are added to analyse. Also due to complexity of physical and chemical properties the ultimate chemical nature of protoplasm cannot be determined.

What is the difference between an organ and an organelle?

Answer

Do you think the cells of an elephant would be larger than the cells of a rat? Explain briefly.

Answer

Cell is the basic unit of life. Cells aggregates to form tissue, organ, organ system and ultimately organism. Elephant has more cells compared to rat. The cell size is independent of the size of the entity. The cell size of a rat and that of an elephant are the same. Within the entity, the cell size is the same, it does not differ. However, what varies is the number of cells. Number of cells in a large entity such as elephant is much more compared to a smaller entity such as a rat.

What is the cell theory? Who propounded it and when?

Answer

The Cell Theory states three major points -

1. The cell is the smallest unit of structure of all living thing
2. The cell is the unit of function of all living things
3. All cells arise from pre-existing cells.

The theory was propounded in 1839 by Schwann and Schleiden. Rudolf Virchow in 1858 made an addition to the cell theory by saying that all cells arise from pre-existing cells.

Differentiate between Protoplasm and cytoplasm.

Answer

Differentiate between Nucleolus and nucleus.

Answer

Differentiate between Centrosome and chromosome.

Answer

Differentiate between Cell wall and cell membrane.

Answer

Differentiate between Plant cell and animal cell.

Answer

Differentiate between Prokaryotes and eukaryotes.

Answer

State the major functions of the following-

1. Plasma membrane
2. Ribosome
3. Lysosome
4. Mitochondria
5. Golgi apparatus
6. Cytoplasm
7. Asters of centrosome
8. Chromosomes
9. Glycogen granule
10. Vacuoles

Answer

The major functions are as follows-

1. Plasma membrane —

   1. Separates contents of cell from its surroundings.
   2. Regulates the entry of certain solutes and ions.
   3. Maintains shape of the cell in animal cells.

2. Ribosome —

   1. Protein synthesis

3. Lysosome —

   1. Intracellular digestion.
   2. Destroy foreign substances.
   3. They are referred to as 'suicidal bags' as they destroy cell organelles when they turn old or are damaged.
   4. Digest cartilages during formation of bones.

4. Mitochondria —

   1. Controls the cell functions.
   2. Referred to as ‘power house of the cell’, as energy is stored in the form of ATP.
   3. Involved in cellular respiration to release energy.
   4. Bearers of genes.

5. Golgi apparatus(in animal cells) —

   1. Synthesis and secretion of enzymes, hormones,etc.
   2. Acrosomes of sperms are formed.

6. Cytoplasm —

   1. Contains organelles perform multitude of functions.
   2. Performs all metabolic activities.

7. Asters of centrosome —

   1. Cell division – regulation and initiation.
   2. Spindle fibre formation.

8. Chromosomes —

   1. Passes genetic characteristics from parents to offspring.

9. Glycogen granule —

   1. Food for cells.

10. Vacuoles —

    1. Stores food, water, pigments and waste products.
    2. Renders turgidity to the plant cell.

Mention the three differences between a living cell and a brick in a wall

Answer

Following are the differences between a living cell and a brick in a wall-

List any six features found both in plant and animal cells.

Answer

Given below are the following six features found both in plant and animal cells

1. Cell membrane is present.
2. Golgi body is present.
3. Liquid matrix known as cytoplasm is observed in the cell.
4. Mitochondria generates energy, is found in the cells.
5. Ribosomes are found. They are responsible for protein synthesis.
6. A prominent nucleus is observed.

Given below are the sketches of two types of cells A and B.

(a) Which one of these is a plant cell? Give reason in support of your answer.

(b) List the cell structures which are common to both the types.

(c) Name the structures found only in plant cells and those found only in animal cells.

Answer

(a) Figure B is a plant cell because in Figure B, the cell has a cell wall, a large vacuole and the vacuole is seen pushing the nucleus to the periphery.

(b) Cell structures common to both the types in the figure are:

1. Nucleus
2. Mitochondria
3. Ribosome
4. Cell membrane
5. Lysosome
6. Endoplasmic reticulum
7. Golgi body

(c) The structures found only in plant cells are Cell wall and Plastid. The structures found only in animal cells are Centrosome.

Gautam observed a plant cell and an animal cell under electron microscope and found one organelle that is present only in animal cells but not in plant cells. The figure of this organelle is shown alongside.

(a) What is this structure called ?

(b) It contains one or two dot-like dense bodies, surrounded by microtubules. Name them.

(c) Write one important role of the above mentioned structure.

Answer

(a) Centrosome

(b) Centriole

(c) It helps in cell division by forming the spindle fibers that separate chromosomes during mitosis and meiosis.