Glossary of Important Words
- Cell
The basic structural and functional unit of all living organisms. - Unicellular Organism
An organism made up of a single cell, e.g., Amoeba, Bacteria. - Multicellular Organism
An organism composed of many cells, e.g., Humans, Trees. - Protoplasm
The living substance inside a cell, consisting of cytoplasm and nucleus. - Cell Membrane (Plasma Membrane)
A thin, flexible outer layer of a cell that controls the movement of substances in and out. - Cell Wall
A rigid outer covering found in plant cells that provides structure and protection. - Cytoplasm
The jelly-like fluid inside the cell where organelles are suspended and cell activities occur. - Nucleus
A membrane-bound structure within the cell that controls all cell activities and contains genetic material (DNA). - Nucleoplasm
The fluid content inside the nucleus. - Chromatin
A network of thread-like structures in the nucleus, made of DNA and protein. - Chromosomes
Condensed form of chromatin that appears during cell division and carries hereditary information. - Cell Organelles
Specialized structures within the cytoplasm that perform specific functions in the cell. - Mitochondria
Rod-shaped organelles known as the powerhouse of the cell; they produce energy through respiration. - Plastids
Organelles found in plant cells that contain pigments or store food.
- Chloroplast: Green plastids that carry out photosynthesis.
- Chromoplast: Provide colors other than green to fruits and flowers.
- Leucoplast: Colorless plastids that store food.
- Endoplasmic Reticulum (ER)
A network of membranes in the cytoplasm.
- Rough ER: With ribosomes; synthesizes proteins.
- Smooth ER: Without ribosomes; synthesizes fats.
- Golgi Complex (Golgi Body)
Organelles involved in modifying, sorting, and packaging materials within the cell. - Vacuole
A storage sac in cells. It is large in plant cells and used for storing water and waste products. - Ribosomes
Small organelles that help in the synthesis of proteins. - Cilia and Flagella
Hair-like or tail-like structures that help in movement and food collection in some unicellular organisms. - Tissue
A group of similar cells that perform a specific function. - Organ
A group of tissues working together to perform a particular function. - Organ System
A group of organs that work together to carry out major body functions. - Organism
A complete living being that can carry out all basic life processes. - Microscope
An optical instrument used to observe cells and other small objects not visible to the naked eye. - Robert Hooke
The scientist who discovered cells in 1665 by observing a thin slice of cork under a microscope. - Red Blood Cell (RBC)
A type of blood cell that carries oxygen throughout the body. - White Blood Cell (WBC)
A type of blood cell that helps in fighting infections.
Something To Know
A. Fill in the blanks:
- All living organisms are made up of cells.
- The cell wall provides rigidity and protection to the plant cell.
- All cellular activities are controlled by the nucleus.
- The mitochondrion is known as the powerhouse of the cell.
- Tissue is a group of cells performing a specific function.
- It was Robert Hooke who observed cells for the first time.
B. Match the following:
- Golgi Complex — (d) packaging centre
- Ribosomes — (e) protein synthesis
- Chromosomes — (a) genes
- Dead cells — (b) cork
- Photosynthesis — (c) chloroplasts
C. Tick (✅) the correct option.
- The cell organelle, which acts as a storage bag for a cell, is known as the—
Chloroplast
Chromoplast
Mitochondria
Vacuole
Answer – vacuole
- Hen’s egg is—
a cell organelle
a single cell
a tissue
an organ
Answer – a single cell
- The nucleus is separated from the cytoplasm by the—
cytoplasm
cell membrane
nuclear membrane
protoplasm
Answer – nuclear membrane
- Which of the following will not be found in an egg cell, human liver cells and an Amoeba7
ribosomes
mitochondria
cell membrane
cell wall
Answer – cell wall
- Which of the following represents the correct sequence?
tissue —> cell —> organ —> organ system
organ —> tissue —> organ system —> cell
cell —> organ —> tissue —> organ system
Cell —> tissue —> organ —> organ system
Answer – cell —> tissue —> organ —> organ system
- Which, amongst the following pairs, can be found only in a plant cell but not in an animal cell?
cell wall and plastids
cell wall and cell membrane
plastids and cilia
plastids and mitochondria
Answer – cell wall and plastids
D. Answer the following questions in brief:
- List the (main) factors that determine the shape of a cell.
Answer – The shape of a cell is mainly determined by:
(i) Its function, and
(ii) Its location in the body of organisms.
- Distinguish between unicellular and multicellular organisms. Give two examples of each.
Answer –
Unicellular Organisms | Multicellular Organisms |
Made up of a single cell. | Made up of many cells. |
Examples: Amoeba, Paramecium | Examples: Human, Earthworm |
- Give reasons for the following:
(a) The cell is called the structural and functional unit of life.
Answer – Because all living organisms are made up of cells and all vital functions like nutrition, respiration and reproduction takes place within the cell.
(b) Plant cells are more rigid than the animal cells.
Answer – Because plant cells have a cell wall that provides rigidity and structural support, which animal cells do not have.
- Which cell organelle is known as the ‘Powerhouse of the cell’? Why is it so called?
Answer – Mitochondria is known as the powerhouse of the cell because it generates energy through the process of cellular respiration.
- Name the cell organelles responsible for imparting colour to the leaves and fruits of a plant.
Answer – Plastids.
Chloroplasts give green colour to leaves.
Chromoplasts provide colour to fruits and flowers.
Leucoplasts store food materials.
- What are cilia and flagella? Write one similarity and one dissimilarity between these two.
Answer – Cilia and flagella are hair-like extensions on the surface of some cells that help in movement and food gathering.
Similarity:
- Both help in locomotion and movement of substances as well as food gathering.
Dissimilarity:
- Cilia are short and numerous, while flagella are long and usually few in number.
- If onion peel cells and cheek cells are observed through a microscope, state the two major differences that the observer is likely to find.
Answer –
Onion Peel Cells (Plant Cells) | Cheek Cells (Animal Cells) |
Have a cell wall. | Do not have a cell wall. |
Have rectangular shape. | Have irregular shape. |
- Classify the following into cells, tissue and organ:
Answer – Cells: fat cell, RBC (Red Blood Cell)
Tissue: blood, muscle
Organ: skin, ear
E. Answer the following questions.
- “All cells in an organism do not have the same shape.”
Justify the above statement by drawing at least three different cell types found in human beings.
Answer – Justification:
Cells in different organs and tissues of an organism have distinct shapes to perform specific functions. For example:
Red Blood Cell (RBC): Biconcave shape to increase surface area for oxygen absorption and transport.
Nerve Cell (Neuron): Long, thread-like structure to transmit nerve impulses over long distances.
Muscle Cell: Elongated and cylindrical shape to allow contraction and movement.
[Diagram Representation]
You can draw the shapes of the three cells:
- Red Blood Cell (Biconcave shape)
- Nerve Cell (Thread-like structure)
- Muscle Cell (Cylindrical or spindle shape)
- Where and how are chromosomes formed? State their significance.
Answer – Where:
Chromosomes are formed in the nucleus of the cell.
How:
Chromosomes are made up of chromatin fibers, which condense into thicker, thread-like structures during cell division (mitosis or meiosis). These fibers consist of DNA and proteins.
Significance:
Chromosomes carry the genetic material (genes), which determines the inherited characteristics of an organism. They play a critical role in cell division, ensuring that genetic information is accurately passed on to the daughter cells.
- With the help of well-labelled diagrams, highlight three differences between a plant cell and an animal cell.
Answer –
Differences:
Feature | Plant Cell | Animal Cell |
Shape | Generally rectangular | Generally irregular |
Cell Wall | Present (rigid outer structure) | Absent |
Plastids | Present (contains chloroplasts for photosynthesis) | Absent |
[Diagram Representation]
You can draw both a plant cell (with cell wall, chloroplasts, and large central vacuole) and an animal cell (with cell membrane and small vacuoles).
- Write the functions performed by the following cell organelles.
(a) Endoplasmic Reticulum (ER):
Answer – Function:
The rough ER is involved in protein synthesis (due to ribosomes attached to it).
The smooth ER is responsible for lipid synthesis and detoxification.
(b) Golgi Complex:
Answer – Function:
The Golgi complex processes, packages and distributes the proteins and lipids synthesized in the cell.
(c) Nucleus:
Answer – Function:
The nucleus controls all cell activities including growth, reproduction and metabolism. It contains chromosomes, which carry genetic information.
(d) Chromoplasts:
Answer – Function:
Chromoplasts contain pigments that give colour to fruits, flowers, and other parts of the plant. They are involved in attracting pollinators.
(e) Vacuoles:
Answer – Function:
Vacuoles store water, waste products and nutrients. In plant cells, large vacuoles help in maintaining turgor pressure.
(f) Mitochondria:
Answer – Function:
Mitochondria are the powerhouses of the cell, responsible for cellular respiration, which generates ATP (energy) for the cell.
- The cell membrane is a very important component of a cell. How is damage to the cell membrane likely to impact the functions of the cell?
Answer – The cell membrane controls the entry and exit of materials into and out of the cell. If damaged, it can lead to:
Loss of control over substances like nutrients, ions and waste products, which can disrupt normal cellular functions.
Leakage of cell contents, which can lead to cell death.
Inability to maintain cell shape and proper osmotic balance.
- Define the term ‘cell’ for plants/animals. Name the different organelles that make a cell. Explain why none of these is called the structural and functional unit of life.
Answer – Definition of Cell:
A cell is the basic structural and functional unit of life in all living organisms. It is the smallest unit that can carry out all the life processes, such as metabolism, growth, reproduction and response to stimuli.
Organelles in an eukaryotic Cell:
The major organelles present in a cell include:
Cell Membrane
Nucleus
Cytoplasm
Mitochondria
Endoplasmic Reticulum (rough and smooth)
Golgi Complex
Ribosomes
Vacuoles
Plastids (in plant cells)
Explanation:
None of these organelles is called the structural and functional unit of life because the entire cell is considered the structural and functional unit, as all organelles work together to perform the essential functions of life. The organelles perform specific tasks, but they depend on each other to keep the cell functioning as a whole.
Value Based Question
The biology teacher started her lesson on the structure and functions of the animal/ plant cells by talking about a cricket team. She told her students that a team wins its matches only when all its members ‘work as a team’ and do their assigned roles in an efficient, sincere and responsible way. She then went on to say that the animal/plant cells also work properly as their different parts work as a ‘team’ and do their specific functions. She advised her students to imbibe the ‘team spirit’ and do their specific functions as responsible members of any ‘team’ they may be a part of. 1. Name two of the values that the teacher spoke of in her class. 2. Have a group discussion in which students suggest how, ‘working as a team’ can improve the ‘overall working’ of a home or a school. 3. Have a ‘play’ in the class in which a group of students give themselves names corresponding to the different cell organelles of a plant/animal cell. Each ‘name’ has to then explain her/his role in the working of the cell.
- Name two of the values that the teacher spoke of in her class.
Answer – The two values that the teacher spoke of are:
Teamwork: Working together efficiently and sincerely to achieve a common goal.
Responsibility: Each member of the team must fulfill their specific role in a dedicated and responsible manner.
- Have a group discussion in which students suggest how, ‘working as a team’ can improve the ‘overall working’ of a home or a school.
Answer – Group Discussion Ideas:
In a Home:
When all family members work together, it makes the house run smoothly. For instance:
Parents can take responsibility for financial planning and decision-making, while children can help with household chores.
Everyone in the family can contribute to maintaining a clean environment, sharing tasks like cooking, cleaning, and managing schedules.
Communication within the family improves, leading to fewer misunderstandings and a healthier atmosphere at home.
In a School:
A school functions better when teachers, students, and staff work together as a team. For example:
Teachers focus on delivering lessons while students actively participate and respect classroom rules, leading to better learning outcomes.
The school administration supports both students and teachers, organizing events, managing resources, and providing a conducive learning environment.
Teamwork among students (group projects, class discussions) fosters collaboration and creativity, leading to a stronger sense of community and shared success.
- Have a ‘play’ in the class in which a group of students give themselves names corresponding to the different cell organelles of a plant/animal cell. Each ‘name’ has to then explain her/his role in the working of the cell.
Answer – Example of the ‘play’:
- The Nucleus (Student A):
“I am the Nucleus! I am the brain of the cell and I control all activities inside the cell. I ensure everything works according to plan, much like a team captain guiding the players on the field.” - Mitochondria (Student B):
“I am the powerhouse of the cell. I generate energy for all the activities that happen within the cell. Without me, there wouldn’t be enough power to carry out important tasks, just like a team needs energy to perform well in a match.” - Ribosomes (Student C):
“I am responsible for protein synthesis! I work with the endoplasmic reticulum to make sure the cell has the proteins it needs to grow and repair itself. Think of me as the coach of the team who helps to make sure everyone has the right equipment.” - Endoplasmic Reticulum (ER) (Student D):
“I am the transport system of the cell. I carry proteins and other materials where they are needed. In a team, I’m like the transport manager who makes sure all resources reach the players on time.” - Golgi Apparatus (Student E):
“I am the packaging and shipping department of the cell. I modify, sort and package proteins and lipids for delivery to other parts of the cell or outside it. Just like a team’s logistics team ensures everything is delivered where it needs to be.” - Cell Membrane (Student F):
“I am the guard of the cell. I control what enters and exits the cell, just like a team’s security ensures no unwanted individuals or materials come in.” - Vacuoles (Student G):
“I store water, nutrients and waste products. In a team, I am like the storage room where supplies are kept until needed.” - Chloroplasts (Student H – Only for plant cell):
“I help the plant cell perform photosynthesis, converting sunlight into energy. I am the energy source for the cell, just like a fuel supply for a team’s performance.”
Something To Do
- Hydrilla is an aquatic plant that can be seen in lakes and ponds. It has small, thin leaves. Take a Hydrilla leaf and place it on a glass slide. Observe it under a microscope. Note your observations.
Answer – Observations of Hydrilla Leaf under the microscope:
When a Hydrilla leaf is placed on a glass slide and observed under a microscope, it typically shows the following features:
Structure: The leaf has a simple, thin, elongated shape. The cells are organized in layers, with small, rectangular-shaped cells visible in the leaf tissue.
Cell Arrangement: The cells are tightly packed together and you might see chloroplasts in some cells, which are responsible for photosynthesis. This helps the plants produce energy from sunlight.
Cell Walls: The outline of each cell is clearly visible due to the cell wall that gives structure and protection to the plant cells.
Chloroplasts: Small, green structures within the cells that are crucial for photosynthesis, which converts light energy into chemical energy.
- Divide the class into four groups of students. Each group will prepare a short report on the topics/questions given below. Two students from each group may then present the report to the whole class. Microscopic view of Hydrilla leaf
(a) When were cells discovered? Were they discovered before or after the invention of the compound microscope?
Answer – Discovery of Cells:
Cells were first discovered in 1665 by Robert Hooke when he observed thin slices of cork under a microscope. He noticed tiny compartments that he called “cells.”
Invention of Compound Microscope:
The compound microscope was invented by Zacharias Janssen and his father, Hans Janssen, around 1590, but it was refined later. So, cells were discovered after the invention of the compound microscope. The discovery of cells was one of the important uses of the microscope.
(b) Does the size and number of cells depend upon the size of the organism?
Answer – Size and Number of Cells:
The size and number of cells can depend on the size and complexity of the organism, but not in a direct one-to-one manner:
Smaller organisms may have smaller cells, but they are often numerous to perform the necessary functions.
Larger organisms like humans or elephants have larger bodies and thus require a greater number of cells, but their cells may not necessarily be much larger. Instead, the number of cells increases to provide the necessary structure and function.
Some cells, such as those in the human body, can be very large (like muscle cells), while others (like red blood cells) are relatively small.
Therefore, the size and number of cells do not depend solely on the size of the organism but also on the organism’s specific requirements for different functions.
(c) List the functions of cell organelles and also mention the organ/organ system that the organelle is similar to in the human body.
Answer – Nucleus:
Function: The nucleus controls cell activities and houses the DNA (genetic material).
Human Body Comparison: Similar to the brain, as it controls and directs activities.
Mitochondria:
Function: Mitochondria produce energy through cellular respiration.
Human Body Comparison: Similar to the digestive system, as it converts food (glucose) into usable energy.
Endoplasmic Reticulum (ER):
Function: The ER is involved in protein synthesis, lipid synthesis, and transport.
Human Body Comparison: Similar to the circulatory system, as it helps transport materials around the cell.
Golgi Apparatus:
Function: The Golgi apparatus packages and distributes proteins and lipids.
Human Body Comparison: Similar to the post office or logistics system, as it packages and delivers substances to the appropriate locations.
Ribosomes:
Function: Ribosomes are responsible for protein synthesis.
Human Body Comparison: Similar to the muscles, as they help in building proteins (muscles build strength).
Lysosomes:
Function: Lysosomes break down waste materials and cellular debris.
Human Body Comparison: Similar to the digestive system, as it helps break down waste in the body.
Cell Membrane:
Function: The cell membrane regulates what enters and exits the cell, maintaining homeostasis.
Human Body Comparison: Similar to skin, as it acts as a barrier protecting the internal environment.
(d) List the advantages of having a cell wall as the outermost boundary in cells.
Answer – Advantages of Cell Wall:
Protection: The cell wall provides structural protection to the cell against physical damage and harmful microorganisms.
Shape and Structure: It helps maintain the shape and rigidity of the cell, preventing it from collapsing under pressure.
Support for Growth: It allows the plant to grow taller and withstand internal pressure without bursting.
Prevents Water Loss: In some cases, the cell wall helps prevent excessive water loss by acting as a barrier.
Communication: The cell wall plays a role in cell-to-cell communication and transport of materials, particularly in plants.
- Complete the crossword puzzle given below.
Across
3. Vacuoles (storage structures of a cell)
5. Cell Membrane (regulates the entry and exit of materials in and out of the cell)
7. Chromoplasts (impart colour to flowers and fruits)
8. Cell Wall (provides shape and rigidity to a plant cell)
10. Mitochondria (powerhouse of the cell)
Down
- Cilia (help Paramecium in locomotion)
- Ribosomes (structure that helps in protein synthesis)
- Chloroplasts (help plant cells in converting solar energy into usable form)
- Nucleus (control centre of the cell)
- Chromosomes (responsible for transferring traits from one generation to the next)
Additional Questions
- What is the function of lysosomes in animal cells?
Answer: Lysosomes are responsible for digesting excess or worn-out organelles, food particles and engulfed viruses or bacteria. They contain digestive enzymes that break down these materials.
- Explain the difference between eukaryotic and prokaryotic cells.
Answer: Eukaryotic cells have a well-defined nucleus enclosed by a membrane and contain membrane-bound organelles, such as the mitochondria, Golgi apparatus, and endoplasmic reticulum. Prokaryotic cells, on the other hand, lack a defined nucleus and membrane-bound organelles. Their genetic material is located in a region called the nucleoid.
- Why is the cell membrane described as selectively permeable?
Answer: The cell membrane is described as selectively permeable because it allows only certain molecules or ions to pass through it while blocking others. This selective permeability helps maintain the internal environment of the cell by regulating the entry and exit of substances.
- What is the role of the nucleolus in the nucleus?
Answer: The nucleolus is the region within the nucleus responsible for the production of ribosomal RNA (rRNA) and the assembly of ribosomes. Ribosomes are essential for protein synthesis in the cell.
- What is the main difference between the rough and smooth endoplasmic reticulum (ER)?
Answer: The rough endoplasmic reticulum (RER) is studded with ribosomes on its surface, which makes it involved in protein synthesis and processing. The smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in lipid synthesis, detoxification and metabolism of carbohydrates.
- How do plant cells differ from animal cells in terms of energy production?
Answer: Plant cells have chloroplasts that enable them to perform photosynthesis, converting light energy into chemical energy. Animal cells, however, rely on mitochondria to produce energy through cellular respiration.
- Why do plant cells have a large central vacuole?
Answer: The large central vacuole in plant cells is responsible for storing water, nutrients, and waste products. It also helps maintain turgor pressure within the cell, which keeps the plant cell rigid and supports the plant’s structure.
- What is the significance of mitosis in multicellular organisms?
Answer: Mitosis is important for growth, repair and asexual reproduction in multicellular organisms. It ensures that the daughter cells are genetically identical to the parent cell, maintaining the organism’s stability and function.
- What is the function of the Golgi apparatus in a cell?
Answer: The Golgi apparatus modifies, sorts and packages proteins and lipids that are synthesized in the endoplasmic reticulum. These molecules are then transported to their final destinations inside or outside the cell.
- What is the function of the cytoskeleton in a cell?
Answer: The cytoskeleton provides structural support to the cell, helping maintain its shape. It also facilitates cell movement and transport of materials within the cell. The cytoskeleton is made of microtubules, microfilaments, and intermediate filaments.