Multiple Choice Questions
1. Which of the following can be made into crystal?
(a) A Bacterium
(b) An Amoeba
(c) A Virus
(d) A Sperm
ANS:(c) A Virus can be made into a crystal. Viruses are microscopic infectious agents that consist of genetic material (DNA or RNA) enclosed in a protein coat called a capsid. Under certain conditions, viruses can be crystallized, which involves arranging the viral particles in an ordered, repeating pattern.
2. A cell will swell up if
(a) The concentration of water molecules in the cell is higher than the
the concentration of water molecules in the surrounding medium
(b) The concentration of water molecules in the 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
ANS: (b) The concentration of water molecules in the surrounding medium is higher than the water molecule concentration in the cell. When the concentration of water molecules is higher outside the cell compared to inside, water will move into the cell through a process called osmosis. This influx of water causes the cell to swell up.
3. Chromosomes are made up of
(a) DNA
(b) protein
(c) DNA and protein
(d) RNA
ANS: (c) Chromosomes are made up of both DNA and protein. DNA carries the genetic information, while proteins help in organizing and compacting the DNA strands into a condensed structure. The combination of DNA and proteins forms the chromatin, which further condenses to form chromosomes during cell division.
4. Which of these options is not a function of Ribosomes?
(i) It helps in the manufacture of protein molecules
(ii) It helps in the manufacture of enzymes
(iii) It helps in the manufacture of hormones
(iv) It helps in the manufacture of starch molecules
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (iv) and (i)
ANS: (d) (iv) and (i) - Ribosomes are involved in the manufacture of protein molecules, enzymes, and hormones. However, they are not involved in the manufacture of starch molecules. Starch synthesis occurs in the chloroplasts of plant cells.
5. Which of these is not related to endoplasmic reticulum?
(a) It behaves as a transport channel for proteins between the nucleus and cytoplasm
(b) It transports materials between various regions in the cytoplasm
(c) It can be the site of energy generation
(d) It can be the site for some biochemical activities of the cell
ANS: (c) It can be the site of energy generation. The endoplasmic reticulum (ER) is primarily involved in protein synthesis, folding, and transport. It is not directly involved in energy generation. Energy generation typically occurs in organelles such as mitochondria.
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
ANS: (c) Movement of solvent molecules from higher concentration to lower concentration of solution through a permeable membrane. Osmosis refers to the movement of solvent molecules (usually water) across a selectively permeable membrane from an area of higher solvent concentration to an area of lower solvent concentration.
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
ANS: (b) Plasmolysis in a plant cell is defined as the shrinkage of cytoplasm in a hypertonic medium. Plasmolysis occurs when a plant cell is placed in a hypertonic solution, causing water to move out of the cell, resulting in the shrinkage of the cytoplasm.
8. Which of the following are covered by a single membrane?
(a) Mitochondria
(b) Vacuole
(c) Lysosome
(d) Plastid
ANS: (c) Lysosome. Lysosomes are membrane-bound organelles that contain digestive enzymes and are covered by a single membrane. Mitochondria, vacuoles, and plastids are covered by a double membrane.
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 protoplasm
ANS: (d) Cytoplasm is called protoplasm. The false sentence is (d). Cytoplasm refers to the entire contents of a cell, including the cytosol and organelles. Protoplasm refers specifically to the living material present within a cell, which includes the cytoplasm and the nucleus.
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
ANS: (b) Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein respectively. The correct sentence is (b). Rough endoplasmic reticulum (RER) is involved in the synthesis of proteins, while smooth endoplasmic reticulum (SER) is involved in lipid synthesis. Enzymes packed in lysosomes are primarily synthesized in the RER, but not all lysosomal enzymes are synthesized in the RER. The endoplasmic reticulum is not directly related to the destruction of the plasma membrane. Nucleoid refers to the region in prokaryotic cells where the genetic material (DNA) is located, not the nucleoplasm of eukaryotic nuclei.
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
ANS: (c) Smooth endoplasmic reticulum plays a crucial role in detoxifying many poisons and drugs in a cell. The smooth ER is involved in the metabolism and detoxification of various substances, including drugs and toxins.
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
ANS: (a) Rough endoplasmic reticulum manufactures the proteins and lipids essential for building the cell membrane. The rough ER is studded with ribosomes, which synthesize proteins that are then processed and modified within the ER.
13. The undefined nuclear region of prokaryotes are also known as
(a) nucleus
(b) nucleolus
(c) nucleic acid
(d) nucleoid
ANS: (d) The undefined nuclear region of prokaryotes is known as the nucleoid. Unlike eukaryotic cells, prokaryotes do not have a true nucleus. Instead, the genetic material, usually in the form of a circular DNA molecule, is concentrated in the nucleoid region.
14. The cell organelle involved in forming complex sugars from simple sugars are
(a) endoplasmic reticulum
(b) ribosomes
(c) plastids
(d) golgi apparatus
ANS: (d) Golgi apparatus is the cell organelle involved in forming complex sugars from simple sugars. The Golgi apparatus processes, modifies, and packages various molecules, including proteins and lipids, for transport to their specific destinations.
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
ANS: (d) Locomotion is not a function of vacuoles. Vacuoles have various functions, including storage of water, nutrients, and waste materials, providing turgidity and rigidity to the cell, and participating in intracellular digestion and excretion. They are not directly involved in locomotion.
16. Amoeba acquires its food through a process, termed
(a) exocytosis
(b) endocytosis
(c) plasmolysis
(d) exocytosis and endocytosis both
ANS: (b) Amoeba acquires its food through endocytosis. Endocytosis is the process by which a cell engulfs external particles or substances by forming a membrane-bound vesicle around them. Amoebas extend pseudopodia to surround and engulf their food particles.
17. Cell wall of which one of these is not made up of cellulose?
(a) Bacteria
(b) Hydrilla
(c) Mango tree
(d) Cactus
ANS: (a) Bacteria have cell walls that are not made up of cellulose. The cell walls of bacteria are primarily composed of peptidoglycan, which is a complex polysaccharide. Cellulose is a structural polysaccharide found in the cell walls of plants and some algae, such as Hydrilla and the cell wall of the mango tree. Cactus also has a unique cell wall composition that includes other compounds like lignin and pectin, but not cellulose.
18. Silver nitrate solution is used to study
(a) endoplasmic reticulum
(b) golgi apparatus
(c) nucleus
(d) mitochondria
ANS: (c) Nucleus. Silver nitrate solution is commonly used to study the nucleolus, which is a substructure within the nucleus involved in ribosome biogenesis.
19. Organelle other than nucleus, containing DNA is
(a) endoplasmic reticulum
(b) golgi apparatus
(c) mitochondria
(d) lysosome
ANS: (c) Mitochondria. Mitochondria are organelles other than the nucleus that contain DNA. They have their own genetic material and are involved in cellular respiration.
20. Kitchen of the cell is
(a) mitochondria
(b) endoplasmic reticulum
(c) chloroplast
(d) Golgi apparatus
ANS: (a) Mitochondria. Mitochondria are often referred to as the "kitchen of the cell" because they are the primary site of cellular respiration and energy production.
21. Lipid molecules in the cell are synthesized by
(a) smooth endoplasmic reticulum
(b) rough endoplasmic reticulum
(c) Golgi apparatus
(d) plastids
ANS: (a) Smooth endoplasmic reticulum. Lipid molecules in the cell are synthesized primarily by the smooth endoplasmic reticulum (SER). The SER is involved in lipid metabolism, including synthesis, modification, and detoxification of lipids.
22. Cell arises from the pre-existing cell was stated by
(a) Haeckel
(b) Virchow
(c) Hooke
(d) Schleiden
ANS: (b) Virchow. The concept that "cell arises from pre-existing cell" was stated by Rudolf Virchow as part of the cell theory.
23. Cell theory was given by
(a) Schleiden and Schwann
(b) Virchow
(c) Hooke
(d) Haeckel
ANS: (a) Schleiden and Schwann. The cell theory was formulated by Matthias Schleiden and Theodor Schwann. Schleiden proposed that plants are made up of cells, while Schwann extended the theory to animals, stating that cells are the fundamental units of both plants and animals.
24. The only cell organelle seen in prokaryotic cell is
(a) mitochondria
(b) ribosomes
(c) plastids
(d) lysosomes
ANS: (b) Ribosomes. Ribosomes are the only cell organelles seen in prokaryotic cells. They are responsible for protein synthesis.
25. Organelle without a cell membrane is
(a) ribosome
(b) golgi apparatus
(c) chloroplast
(d) nucleus
ANS: (b) Ribosomes. Ribosomes are the only cell organelles seen in prokaryotic cells. They are responsible for protein synthesis.
26. 1 µm is
(a) 10–6 m
(b) 10–9 m
(c) 10–10 m
(d) 10–3 m
ANS: (a) 10^-6 m. 1 µm (micrometer) is equal to 10^-6 meters.
27. Lysosome arises from
(a) endoplasmic reticulum
(b) Golgi apparatus
(c) nucleus
(d) mitochondria
ANS: (b) Golgi apparatus. Lysosomes arise from the Golgi apparatus. The Golgi apparatus is responsible for modifying, sorting, and packaging various molecules, including lysosomal enzymes.
28. Living cells were discovered by
(a) Robert Hooke
(b) Purkinje
(c) Leeuwenhoek
(d) Robert Brown
ANS: (c) Leeuwenhoek. Living cells were first discovered by Antonie van Leeuwenhoek, who observed and described microorganisms using a microscope.
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
ANS: (d) Plasma membranes contain chitin sugar in plants. This statement is incorrect. Chitin is a structural polysaccharide found in the cell walls of fungi and the exoskeletons of arthropods. Plant cell walls, on the other hand, contain cellulose as the primary structural component.
Short Answer Questions
30. Why are lysosomes known as ‘suicide bags’ of a cell?
ANS: Lysosomes are known as 'suicide-bags' of a cell because they contain digestive enzymes capable of breaking down various molecules, including proteins, lipids, carbohydrates, and even cellular components. If the cell is damaged, dysfunctional, or undergoing programmed cell death (apoptosis), lysosomes can release their enzymes and cause the breakdown of cellular materials, leading to the destruction of the cell.
31. Do you agree that “A cell is a building unit of an organism”. If yes, explain why?
ANS: Yes, a cell is considered the building unit of an organism. All living organisms are composed of cells, which are the basic structural and functional units. Cells perform various functions necessary for the survival and functioning of the organism. They carry out essential processes such as metabolism, growth, reproduction, and response to stimuli. Additionally, cells can differentiate and specialize into different types, forming tissues, organs, and organ systems in multicellular organisms.
32. Why does the skin of your finger shrink when you wash clothes for a long time?
ANS: The skin of the finger shrinks when you wash clothes for a long time because prolonged exposure to water can lead to osmosis. Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration across a semipermeable membrane. When the skin of the finger is in contact with water for an extended period, the water concentration on the outer surface of the skin becomes higher than the water concentration inside the skin cells. As a result, water moves out of the skin cells, causing them to shrink or wrinkle temporarily.
33. Why is endocytosis found in animals only?
ANS: Endocytosis is found in animals because animals have specialized cell structures, such as plasma membranes, that are capable of invagination and forming vesicles. Endocytosis is a process by which cells engulf external substances or particles by forming vesicles from the plasma membrane. These vesicles transport the engulfed materials into the cell. Since animals have complex cell structures and specialized membrane dynamics, they are capable of performing endocytosis. In contrast, prokaryotic cells, such as bacteria, lack the complex membrane dynamics required for endocytosis.
34. A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.
ANS: The phenomenon responsible for the person vomiting after taking a concentrated solution of salt is osmosis. When a concentrated solution of salt is consumed, it increases the solute concentration outside the cells. As a result, water molecules move out of the cells through osmosis, trying to balance the concentration. This can lead to dehydration of the cells and disrupt the normal functioning of tissues. In response, the body triggers vomiting as a protective mechanism to expel the excessive salt and restore the balance of solute concentration.
35. Name any cell organelle which is non membranous.
ANS: Ribosomes are an example of a non-membranous cell organelle. Ribosomes are small, dense structures composed of RNA and proteins. They are involved in protein synthesis and can be found in both prokaryotic and eukaryotic cells. Unlike organelles such as mitochondria, chloroplasts, or lysosomes, ribosomes do not have a surrounding membrane.
36. We eat food composed of all the nutrients like carbohydrates, proteins, fats, vitamins, minerals and water. After digestion, these are absorbed in the form of glucose, aminoacids, fatty acids, glycerol etc. What mechanisms are involved in absorption of digested food and water?
ANS: The mechanisms involved in the absorption of digested food and water are as follows:
- Diffusion: Small molecules such as water, glucose, and ions can passively diffuse across the cell membranes of the digestive system into the bloodstream or surrounding tissues. This occurs down their concentration gradient, from an area of higher concentration to an area of lower concentration.
- Facilitated Diffusion: Some larger molecules, such as certain vitamins and ions, require specialized transport proteins to facilitate their movement across the cell membranes. These transport proteins assist in the facilitated diffusion of specific molecules across the membrane.
- Active Transport: Certain nutrients, such as amino acids and glucose, require active transport mechanisms for absorption. Active transport involves the use of carrier proteins in the cell membranes that actively pump these molecules against their concentration gradient. This process requires the expenditure of energy in the form of ATP.
- Endocytosis: In certain cases, larger molecules or clusters of molecules are absorbed through endocytosis. Endocytosis is a process in which the cell membrane invaginates, forming a vesicle that engulfs the desired substances. The vesicle then enters the cell, allowing for the internalization of the absorbed material.
37. If you are provided with some vegetables to cook. You generally add salt
to the vegetables during the cooking process. After adding salt, vegetables
release water. What mechanism is responsible for this?
ANS: The mechanism responsible for the release of water from vegetables after adding salt during the cooking process is osmosis. When salt is added to vegetables, it increases the concentration of solutes outside the vegetable cells. As a result, water molecules move out of the vegetable cells through osmosis, flowing from an area of higher water concentration (inside the cells) to an area of lower water concentration (outside the cells). This causes the vegetables to release water and become more tender during cooking.
38. If cells of onion peel and RBC are separately kept in hypotonic solution,
what among the following will take place? Explain the reason for your
answer.
(a) Both the cells will swell.
(b) RBC will burst easily while cells of onion peel will resist the bursting to
some extent.
(c) a and b both are correct.
(d) RBC and onion peel cells will behave similarly.
ANS: (b) RBC will burst easily while cells of onion peel will resist the bursting to some extent.
When both onion peel cells and red blood cells (RBCs) are separately placed in a hypotonic solution, which has a lower solute concentration compared to the cells, osmosis occurs. In this case, the hypotonic solution has a higher water concentration than the cells.
RBCs lack a rigid cell wall, and as a result, water enters the cells rapidly through osmosis, causing them to swell and eventually burst (hemolysis) due to the high internal pressure.
On the other hand, onion peel cells have a cell wall surrounding them, which provides structural support and prevents excessive water intake. While these cells will still absorb some water and undergo swelling, their cell walls help them resist bursting to some extent.
39. Bacteria do not have chloroplast but some bacteria are photoautorophic
in nature and perform photosynthesis. Which part of bacterial cell performs
this?
ANS: Bacterial cells do not possess chloroplasts like plant cells do. However, some bacteria are photosynthetic and perform photosynthesis. In these bacteria, the photosynthetic process takes place in specialized structures called "chlorosomes." Chlorosomes are unique to photosynthetic bacteria and are responsible for capturing light energy and carrying out photosynthesis. They contain pigments that absorb light and convert it into chemical energy, allowing the bacteria to produce organic molecules through photosynthesis.
40. Match the following A and B
ANS: (a) Smooth endoplasmic reticulum (iv) Detoxification
(b) Lysosome (v) Suicidal bag
(c) Nucleoid (iii) Bacteria
(d) Food vacuoles (i) Amoeba
(e) chromatin material and nucleolus (ii) nucleus
41. Write the name of different plant parts in which chromoplast, chloroplast
and leucoplast is present.
ANS: Chromoplasts are present in flower petals, fruits, and some roots.
Chloroplasts are present in green leaves and stems.
Leucoplasts are present in underground storage organs like tubers and bulbs.
42. Name the organelles which show the analogy written as under
(a) Transporting channels of the cell——
(b) Power house of the cell——
(c) Packaging and dispatching unit of the cell——
(d) Digestive bag of the cell——
(e) Storage sacs of the cell——
(f) Kitchen of the cell——
(g) Control room of the cell——
ANS: (a) Transporting channels of the cell - Endoplasmic reticulum
(b) Powerhouse of the cell - Mitochondria
(c) Packaging and dispatching unit of the cell - Golgi apparatus
(d) Digestive bag of the cell - Lysosome
(e) Storage sacs of the cell - Vacuoles
(f) Kitchen of the cell - Chloroplasts
(g) Control room of the cell - Nucleus
43. How is a bacterial cell different from an onion peel cell?
ANS: Bacterial Cell vs. Onion Peel Cell:
Bacterial Cell: It is prokaryotic, lacks a nucleus and membrane-bound organelles, has a cell wall, and contains a single circular DNA molecule in the nucleoid region.
Onion Peel Cell: It is a plant cell, eukaryotic, contains a nucleus and membrane-bound organelles, has a cell wall made of cellulose, and contains multiple linear DNA molecules organized in the nucleus
44. How do substances like carbon dioxide (CO2) and water (H2O) move in and
out of the cell?
ANS: Substances like carbon dioxide (CO2) and water (H2O) move in and out of the cell through various mechanisms:
Diffusion: Small molecules like CO2 can passively diffuse across the cell membrane from an area of higher concentration to lower concentration.
Osmosis: Water molecules can move across the cell membrane through osmosis, which is the diffusion of water from an area of higher water concentration to lower water concentration.
Active Transport: In some cases, special transport proteins and cellular energy (ATP) are used to actively pump substances like ions across the cell membrane against their concentration gradient.
45. How does an amoeba obtain its food?
ANS: Amoeba obtains its food through a process called endocytosis. It extends its pseudopodia (temporary projections of the cell membrane) around the food particle, enclosing it within a small portion of the cell membrane. This forms a food vacuole. The amoeba then secretes enzymes into the food vacuole to digest the food. The digested nutrients are absorbed into the cytoplasm of the amoeba, and the undigested waste is expelled from the cell.
46. Name the two organelles in a plant cell that contain their own genetic material and ribosomes.
ANS: The two organelles in a plant cell that contain their own genetic material (DNA) and ribosomes are:
Nucleus: The nucleus contains the main genetic material (DNA) of the cell and is responsible for controlling cellular activities.
Mitochondria: Mitochondria have their own DNA and ribosomes. They are involved in energy production through cellular respiration and have a role in protein synthesis.
47. Why are lysosomes also known as “scavengers of the cells”?
ANS: Lysosomes are known as "scavengers of the cells" because they contain digestive enzymes that break down waste materials, cellular debris, and foreign substances within the cell. They help in recycling cellular components and maintaining cell cleanliness by degrading unwanted substances.
48. Which cell organelle controls most of the activities of the cell?
ANS: The nucleus controls most of the activities of the cell. It contains the cell's genetic material (DNA) and is responsible for regulating gene expression, DNA replication, and the synthesis of RNA. The nucleus also controls the cell's growth, division, and overall cellular functions.
49. Which kind of plastid is more common in
(a) roots of the plant
(b) leaves of the plant
(c) flowers and fruits
ANS: (a) Leucoplasts are more common in the roots of the plant. These plastids are involved in storing nutrients such as starch and oils.
(b) Chloroplasts are more common in the leaves of the plant. These plastids contain chlorophyll and are responsible for photosynthesis.
(c) Chromoplasts are more common in flowers and fruits of the plant. These plastids are involved in the synthesis and accumulation of pigments, giving vibrant colors to flowers and fruits.
50. Why do plant cells possess large sized vacuole?
ANS: Plant cells possess a large-sized vacuole for several reasons:
Storage: The vacuole acts as a storage compartment for water, nutrients, ions, and various organic compounds in the cell.
Turgor Pressure: The vacuole helps maintain turgor pressure, which provides structural support to plant cells and allows them to maintain rigidity.
Waste Management: The vacuole functions in the storage and breakdown of waste materials, helping to detoxify the cell.
Regulation of Cell Volume: By controlling the water content within the vacuole, plant cells can regulate their overall cell volume and maintain optimal cellular conditions.
51. How are chromatin, chromatid and chromosomes related to each other?
ANS: Chromatin, chromatid, and chromosomes are related as follows:
Chromatin: Chromatin refers to the complex of DNA, RNA, and proteins (histones) that make up the genetic material within the nucleus of a cell. It exists in a less condensed form during interphase, allowing for gene expression and DNA replication.
Chromatid: A chromatid is one of the two identical copies of a replicated chromosome. During cell division, each chromatid is separated and distributed to daughter cells.
Chromosomes: Chromosomes are structures formed by the condensation and coiling of chromatids. They are visible under a microscope and contain the genetic information in the form of DNA. Chromosomes are replicated during the cell cycle and are responsible for the transmission of genetic material to the next generation.
52. What are the consequences of the following conditions?
(a) A cell containing higher water concentration than the surrounding
medium
(b) A cell having low water concentration than the surrounding medium.
(c) A cell having equal water concentration to its surrounding medium
ANS: The consequences of the following conditions are:
(a) A cell containing a higher water concentration than the surrounding medium:
- In a hypotonic environment, water will enter the cell through osmosis, causing the cell to swell or potentially burst (cytolysis) if the cell wall is absent or weak.
(b) A cell having a lower water concentration than the surrounding medium:
- In a hypertonic environment, water will leave the cell through osmosis, causing the cell to shrink and undergo plasmolysis.
(c) A cell having an equal water concentration to its surrounding medium:
- In an isotonic environment, there is no net movement of water across the cell membrane. The cell will maintain its normal shape and volume.
Long Answer Questions
53. Draw a plant cell and label the parts which
(a) determines the function and development of the cell
(b) packages materials coming from the endoplasmic reticulum
(c) provides resistance to microbes to withstand hypotonic external media
without bursting
(d) is site for many biochemical reactions necessary to sustain life.
(e) is a fluid contained inside the nucleus
ANS: (a) Nucleus: The nucleus determines the function and development of the cell as it contains the cell's genetic material (DNA). It controls the activities of the cell and is involved in cell division, gene expression, and regulation.
(b) Golgi Apparatus: The Golgi apparatus packages materials coming from the endoplasmic reticulum. It modifies, sorts, and packages proteins and lipids into vesicles for transport to their specific destinations within or outside the cell.
(c) Cell Wall: The cell wall provides resistance to microbes and helps plant cells withstand hypotonic external media without bursting. It provides structural support and protection to the cell.
(d) Cytoplasm: The cytoplasm is the site for many biochemical reactions necessary to sustain life. It contains various organelles, enzymes, and other molecules involved in cellular metabolism and processes such as protein synthesis, energy production, and nutrient storage.
(e) Nucleoplasm: The nucleoplasm is the fluid contained inside the nucleus. It contains the chromatin (DNA, RNA, and proteins) and various nucleoplasmic proteins involved in gene expression and regulation.
54. Illustrate only a plant cell as seen under electron microscope. How is it
different from animal cell?
ANS: In a plant cell, under an electron microscope, you would observe additional structures compared to an animal cell. These structures include:
Cell Wall: The plant cell has a rigid cell wall made of cellulose outside the cell membrane, providing shape, support, and protection.
Chloroplasts: Plant cells contain chloroplasts responsible for photosynthesis, which are not present in animal cells.
Large Central Vacuole: Plant cells typically have a large central vacuole that occupies a significant portion of the cell's volume. Animal cells may have smaller vacuoles, but they are not as prominent as in plant cells.
In contrast, animal cells lack a cell wall, chloroplasts, and a large central vacuole. Instead, animal cells may have specialized structures like centrioles, cilia, or flagella that are not typically found in plant cells.
55. Draw a neat labelled diagram of an animal cell.
56. Draw a well labelled diagram of an eukaryotic nucleus. How is it different
from nucleoid?
ANS: The eukaryotic nucleus is enclosed by a nuclear envelope, which consists of two membranes and nuclear pores. Inside the nucleus, there is the nucleolus, which is involved in ribosome synthesis. The chromatin material, composed of DNA and proteins, is also present in the nucleus.
The eukaryotic nucleus is different from the nucleoid found in prokaryotic cells. The nucleoid is not membrane-bound and does not have a defined nucleus. It contains the genetic material (DNA) of the prokaryotic cell, but it lacks the distinct organization and structures present in a eukaryotic nucleus.
57. Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis?
58. In brief state what happens when
(a) dry apricots are left for sometime in pure water and later transferred to
sugar solution?
(b) a Red Blood Cell is kept in concentrated saline solution?
(c) the Plasma-membrane of a cell breaks down?
(d) rheo leaves are boiled in water first and then a drop of sugar syrup is
put on it?
(e) golgi apparatus is removed from the cell?
ANS: (a) When dry apricots are left in pure water for some time, they undergo a process called osmosis. Osmosis is the movement of water molecules from an area of lower solute concentration (in this case, water) to an area of higher solute concentration (inside the apricot cells) through a semipermeable membrane. As a result, water enters the cells of the apricots, causing them to swell and become rehydrated. When the rehydrated apricots are transferred to a sugar solution, the process of osmosis continues, but in the opposite direction. The higher concentration of solutes in the sugar solution causes water to move out of the apricot cells, leading to shrinkage and the loss of plumpness.
(b) When a red blood cell (RBC) is placed in a concentrated saline solution, which has a higher salt concentration than the cytoplasm of the RBC, it will experience a process called crenation. In crenation, water moves out of the RBC through osmosis, following the concentration gradient. As a result, the RBC shrinks and becomes distorted due to the loss of water. The high salt concentration in the saline solution dehydrates the RBC and alters its shape.
(c) The plasma membrane is a vital component of a cell that separates the cell's internal environment from the external environment. If the plasma membrane breaks down, the cell loses its integrity and its contents can leak out. The breakdown of the plasma membrane can result from physical damage, chemical disruption, or certain pathological conditions. When the plasma membrane breaks down, the cell's internal components, such as organelles and cytoplasmic contents, may disperse or mix with the surrounding environment. This can lead to the loss of cell function and ultimately cell death.
(d) When rheo leaves are boiled in water, heat is applied, causing the cells' membranes to rupture and release the cell contents into the boiling water. The boiling water disrupts the structural integrity of the plant cells, resulting in the breakdown of cell membranes and the release of various substances contained within the cells. When a drop of sugar syrup is added to the boiled leaves, the syrup can diffuse into the disrupted cells, potentially causing changes in taste, texture, or other chemical reactions.
(e) The Golgi apparatus is an organelle involved in the processing, packaging, and sorting of proteins and lipids for transport within the cell or secretion outside the cell. If the Golgi apparatus is removed from the cell, it will significantly impair the cell's ability to modify and package these molecules. This can result in the disruption of intracellular transport, impaired secretion of proteins, and overall dysfunction of cellular processes that rely on the proper sorting and delivery of molecules.
59. Draw a neat diagram of plant cell and label any three parts which
differentiate it from animal cell
ANS: Cell Wall: Plant cells have a rigid cell wall surrounding the plasma membrane. The cell wall is made up of cellulose fibers and provides structural support and protection to the cell. Animal cells lack a cell wall.
Chloroplasts: Plant cells contain chloroplasts, which are responsible for photosynthesis. Chloroplasts contain chlorophyll, a pigment that captures sunlight and converts it into chemical energy. Animal cells do not have chloroplasts.
Large Central Vacuole: Plant cells typically have a large central vacuole that occupies a significant portion of the cell's volume. The vacuole stores water, nutrients, and waste products, and helps maintain the turgidity and rigidity of the cell. Animal cells may have smaller vacuoles, but they are not as prominent as in plant cells
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