Intext Questions

Q.1     Who discovered cells and how?
Sol.     It was Robert Hooke who discovered cells. He observed the cells in thin slices of cork. They appeared like small compartments when viewed through the microscope.

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Q.2     Why is the cell called structural and functional unit of life?
Sol.     A cell is capable of carrying out all the life functions; such as nutrition, excretion, respiration, etc. Hence a cell is called the functional unit of life. Additionally, the cell is the smallest unit of life and all the living beings are made up of cells. Hence a cell is called the structural unit of life.

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Q.1     How do substances like CO₂ and water move in and out of the cell? Discuss.
Sol.     Substances move in and out of the cell because of diffusion. Diffusion is the random movement of particles in order to attain concentration equilibrium. The movement of water through a semi-permeable membrane is called osmosis. It is important to note that plasma membrane is a semi-permeable membrane. Water always moves from high water concentration to low water concentration.

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Q.2     Why is the plasma membrane called a selectively permeable membrane?
Sol.     Plasma membrane allows passage to some selected substances. Hence it is called a selectively permeable or semi-permeable membrane.

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Q.1     Can you name the two organelles we have studied that contain their own genetic material?
Sol.     Mitochondria and Chloroplast contain their own genetic material.

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Q.2     If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
Sol.     Various parts of a cell are responsible for various functions. They work in tandem to continue life in the cell. In case, the organization of a cell is destroyed due to some physical or chemical influence, the cell will die.

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Q.3     Why are lysosomes known as suicide bags?
Sol.      Lysosomes contain digestive enzymes. In case of a rupture in lysosome, the enzymes are released in the cytoplasm and end up digesting the contents of the cell. This results in cell death. Due to this, lysosome is also known as suicide bags of cells.

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Q.4     Where are proteins synthesized inside the cell?
Sol.     Proteins are synthesized in ribosome.

 

Exercise

Q.1     Make a comparison and write down ways in which plant cells are different from animal cells.
Sol.

Plant cell	Animal cell
Cell wall present	Cell wall absent
Plastids present	Plastids absent
Vacuole is usually very large and single	Vacuoles are much smaller and may be absent

Q.2     How is a prokaryotic cell different from a eukaryotic cell?
Sol.

Prokaryotic cell	Eukaryotic cell
Size : generally small (1 – 10µ) 1µ (micron) = 10–6m	Size : generally large (5– 100µ)
Nuclear region is now defined and nuclear membrane is absent	Nuclear region is well defined and surrounded by  a nuclear membrane.
Single chromosome	More than one chromosome
Membrane bound cell organelles absent	Membrane bound cell organelles present

Q.3     What would happen if the plasma membrane ruptures or breaks down?
Sol.     Plasma membrane provides a container for the cell organelles and cytoplasm. Moreover, plasma membrane also protects the contents of a cell from external environment. In case the plasma membrane ruptures or breaks down, the cell contents would be exposed to the external environment. This would prove lethal for the cell and the cell would cease to exist.

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Q.4     What would happen to the life of a cell if there was no Golgi apparatus?
Sol.     Golgi apparatus plays the important role of packaging various substances for further use or for storage. If there was no Golgi apparatus, various substances would not be in a position to be transformed in proper forms for further use. Certain substances; like protein and lipid are important for the formation of plasma membrane and hence absence of Golgi apparatus will hamper the formation of new cells during cell division.

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Q.5     Which organelle is known as the powerhouse of the cell? Why?
Sol.     Mitochondrion is known as the powerhouse of the cell. The reason for this is the fact that cellular respiration takes place in mitochondria and the energy released after that gets stored in mitochondria; in the form of ATP. These ATP molecules are utilized on an SOS basis.

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Q.6     Where do the lipids and proteins constituting the cell membrane get synthesised?
Sol.      Lipids are synthesized in the endoplasmic reticulum. Protein is synthesized in ribosomes which are usually present on the rough ER.

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Q.7     How does an Amoeba obtain its food?
Sol.     Amoeba obtains its food through a process called phagocytosis. The cell membrane of amoeba is projected into numerous finger-like outgrowths; called pseudopodia. Amoeba surrounds a food particle by pseudopodia and makes a food vacuole; after engulfing the food.

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Q.8     What is osmosis?
Sol.      The movement of water from high concentration to low concentration through a semi-permeable membrane is called osmosis.

Exemplar

Multiple Choice Questions

Q.1 Which of the following can be made into crystal?

(a) A Bacterium

(b) An Amoeba

(c) A Virus

(d) A Sperm

Sol. (c)

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Q.2 A cell will swell up if

(a) The concentration of water molecules in the cell is higher than the concentration of water molecules in surrounding medium

(b) The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell

(c) The concentration of water molecules is same in the cell and in the surrounding medium

(d) Concentration of water molecules does not matter

Sol. (b)

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Q.3 Chromosomes are made up of

(a) DNA

(b) protein

(c) DNA and protein

(d) RNA

Sol. (c)

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Q.4 Which of these options are not a function of Ribosomes?

(i) It helps in manufacture of protein molecules

(ii) It helps in manufacture of enzymes

(iii) It helps in manufacture of hormones

(iv) It helps in manufacture of starch molecules

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (iv) and (i)

Sol. (c)

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Q.5 Which of these is not related to endoplasmic reticulum?

(a) It behaves as transport channel for proteins between nucleus and cytoplasm

(b) It transports materials between various regions in cytoplasm

(c) It can be the site of energy generation

(d) It can be the site for some biochemical activities of the cell

Sol. (c)

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Q.6 Following are a few definitions of osmosis.

Read carefully and select the correct definition

(a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane

(b) Movement of solvent molecules from its higher concentration to lower concentration

(c) Movement of solvent molecules from higher concentration to lower concentration of solution through a permeable membrane

(d) Movement of solute molecules from lower concentration to higher concentration of solution through a semipermeable membrane

Sol. (a)

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Q.7 Plasmolysis in a plant cell is defined as

(a) break down (lysis ) of plasma membrane in hypotonic medium

(b) shrinkage of cytoplasm in hypertonic medium

(c) shrinkage of nucleoplasm

(d) none of them

Sol. (b)

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Q.8 Which of the following are covered by a single membrane?

(a) Mitochondria

(b) Vacuole

(c) Lysosome

(d) Plastid

Sol. (b), (c)

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Q.9 Find out the false sentences

(a) Golgi apparatus is involved with the formation of lysosomes

(b) Nucleus, mitochondria and plastid have DNA; hence they are able to make their own structural proteins

(c) Mitochondria is said to be the power house of the cell as ATP is generated in them.

(d) Cytoplasm is called as protoplasm

Sol. (a)

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Q.10 Find out the correct sentence

(a) Enzymes packed in Lysosomes are made through RER (rough endoplasmic reticulum)

(b) Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein respectively

(c) Endoplasmic reticulum is related with the destruction of plasma membrane

(d) Nucleoid is present inside the nucleoplasm of eukaryotic nucleus

Sol. (a)

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Q.11 Which cell organelle plays a crucial role in detoxifying many poisons and drugs in a cell?

(a) Golgi apparatus

(b) Lysosomes

(c) Smooth endoplasmic reticulum

(d) Vacuoles

Sol. (c)

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Q.12 The proteins and lipids, essential for building the cell membrane, are manufactured by

(a) rough endoplasmic reticulum

(b) golgi apparatus

(c) plasma membrane

(d) mitochondria

Sol. (a)

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Q.13 The undefined nuclear region of prokaryotes are also known as

(a) nucleus

(b) nucleolus

(c) nucleic acid

(d) nucleoid

Sol. (d)

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Q.14 The cell organelle involved in forming complex sugars from simple sugars are

(a) endoplasmic reticulum

(b) ribosomes

(c) plastids

(d) golgi apparatus

Sol. (d)

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Q.15 Which out of the following is not a function of vacuole?

(a) Storage

(b) Providing turgidity and rigidity to the cell

(c) Waste excretion

(d) Locomotion

Sol. (d)

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Q.16 Amoeba acquires its food through a process, termed

(a) exocytosis

(b) endocytosis

(c) plasmolysis

(d) exocytosis and endocytosis both

Sol. (b)

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Q.17 Cell wall of which one of these is not made up of cellulose?

(a) Bacteria

(b) Hydrilla

(c) Mango tree

(d) Cactus

Sol. (a)

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Q.18 Silver nitrate solution is used to study

(a) endoplasmic reticulum

(b) golgi apparatus

(c) nucleus

(d) mitochondria

Sol. (b)

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Q.19 Organelle other than nucleus, containing DNA is

(a) endoplasmic reticulum

(b) golgi apparatus

(c) mitochondria

(d) lysosome

Sol. (c)

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Q.20 Kitchen of the cell is

(a) mitochondria

(b) endoplasmic reticulum

(c) chloroplast

(d) golgi apparatus

Sol. (c)

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Q.21 Lipid molecules in the cell are sythesized by

(a) smooth endoplasmic reticulum

(b) rough endoplasmic reticulum

(c) golgi apparatus

(d) plastids

Sol. (a)

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Q.22 Cell arises from pre-existing cell was stated by

(a) Haeckel

(b) Virchow

(c) Hooke

(d) Schleiden

Sol. (b)

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Q.23 Cell theory was given by

(a) Schleiden and Schwann

(b) Virchow

(c) Hooke

(d) Haeckel

Sol. (a)

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Q.24 The only cell organelle seen in prokaryotic cell is

(a) mitochondria

(b) ribosomes

(c) plastids

(d) lysosomes

Sol. (b)

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Q.25 Organelle without a cell membrane is

(a) ribosome

(b) golgi apparatus

(c) chloroplast

(d) nucleus

Sol. (a)

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Q.26 1 μm is

(a) 10^–6 m

(b) 10^–9 m

(c) 10^–10 m

(d) 10^–3 m

Sol. (a)

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Q.27 Lysosome arises from

(a) endoplasmic reticulum

(b) golgi apparatus

(c) nucleus

(d) mitochondria

Sol. (b)

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Q.28 Living cells were discovered by

(a) Robert Hooke

(b) Purkinje

(c) Leeuwenhoek

(d) Robert Brown

Sol. (c)

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Q.29 Select the odd one out

(a) The movement of water across a semi permeable membrane is affected by the amount of substances dissolved in it.

(b) Membranes are made of organic molecules like proteins and lipids

(c) Molecules soluble in organic solvents can easily pass through the membrane.

(d) Plasma membranes contain chitin sugar in plants

Sol. (d)