Unit 3 – Cell: Structure and Functions
Easy Line-by-Line Notes (NEET Level for Beginners)
1. “Biology is the study of living organisms.”
- Biology = science of life.
- It studies plants, animals, microbes, and humans.
2. “The detailed description of their form and appearance only brought out their diversity.”
- Living organisms look different from each other.
- Example: bacteria, plants, and humans all have different shapes and sizes.
3. “Cell theory emphasised the unity underlying this diversity of forms.”
- Even though organisms look different, all are made of cells.
- This common feature is explained by Cell Theory.
4. “The cellular organisation of all life forms.”
- Every living organism is made of one or more cells.
- Cell = basic structural and functional unit of life.
5. “A description of cell structure and cell growth by division...”
- Cells have different parts called organelles.
- Cells grow and reproduce by cell division.
6. “Cell theory also created a sense of mystery around living phenomena.”
- Scientists wondered how tiny cells perform life activities.
7. “Physiological and behavioural processes.”
- Physiological processes = digestion, respiration, excretion etc.
- Behavioural processes = response to environment, movement etc.
8. “Integrity of cellular organisation...”
- Proper arrangement of cell parts is necessary for life.
- If cells are damaged, body functions stop.
9. “One can take a physico-chemical approach...”
- Life processes can be studied using physics and chemistry.
- Example: enzymes, pH, diffusion.
10. “Use cell-free systems to investigate.”
- Scientists can study reactions outside the cell in laboratories.
11. “This approach enables us to describe processes in molecular terms.”
- Life activities happen because of molecules like proteins, DNA, enzymes, carbohydrates, etc.
12. “Analysis of living tissues for elements and compounds.”
- Scientists study tissues to know what chemicals are present.
- Main elements: carbon, hydrogen, oxygen, nitrogen.
13. “What types of organic compounds are present...”
- Cells contain biomolecules:
- Proteins
- Carbohydrates
- Lipids
- Nucleic acids
14. “What are these compounds doing inside a cell?”
- Biomolecules perform different functions:
- Proteins → enzymes, structure
- Carbohydrates → energy
- Lipids → membranes
- DNA/RNA → genetic control
15. “Gross physiological processes like digestion, excretion, memory...”
- Complex body functions are controlled by cellular and molecular activities.
16. “What is the molecular basis of physiological processes?”
- Molecular basis means:
- How molecules work together to perform life processes.
17. “It can also explain abnormal processes...”
- Studying cells helps understand diseases.
- Example:
- Cancer = uncontrolled cell division
- Diabetes = hormonal imbalance
18. “This physico-chemical approach is called Reductionist Biology.”
- Reductionist Biology = studying life by breaking it into smaller molecular parts.
19. “Concepts and techniques of physics and chemistry are applied...”
- Modern biology uses:
- Microscopes
- Centrifugation
- X-rays
- Chemical analysis
20. “A brief description of biomolecules is provided.”
- Biomolecules are chemicals found in living organisms.
- Important for NEET:
- Proteins
- Lipids
- Carbohydrates
- Nucleic acids
 |
| Class 11 Biology – Cell Structure and Functions simplified notes for CBSE and NEET students. |
CLASS 11 BIOLOGY – CBSE QUESTIONS & ANSWERS
UNIT 3: CELL – STRUCTURE AND FUNCTIONS
1. Multiple Choice Questions (MCQs)
Q1. The basic structural and functional unit of life is:
a) Tissue
b) Organ
c) Cell
d) Nucleus
Answer: c) Cell
Q2. Cell theory was proposed by:
a) Darwin and Lamarck
b) Schleiden and Schwann
c) Mendel and Morgan
d) Watson and Crick
Answer: b) Schleiden and Schwann
Q3. New cells arise from:
a) Air
b) Water
c) Pre-existing cells
d) Tissues
Answer: c) Pre-existing cells
Q4. Study of life at molecular level is called:
a) Ecology
b) Genetics
c) Reductionist Biology
d) Anatomy
Answer: c) Reductionist Biology
Q5. Which biomolecule stores genetic information?
a) Protein
b) Lipid
c) Nucleic acid
d) Carbohydrate
Answer: c) Nucleic acid
2. Very Short Answer Questions
Q1. Define cell.
Answer: Cell is the basic structural and functional unit of life.
Q2. Who gave the statement “Omnis cellula e cellula”?
Answer: Rudolf Virchow.
Q3. Name two biomolecules.
Answer: Proteins and carbohydrates.
Q4. What is physiology?
Answer: Study of functions of living organisms.
Q5. What is cell theory?
Answer: It states that all living organisms are made of cells and cells are the basic unit of life.
3. Short Answer Questions
Q1. Write any three points of cell theory.
Answer:
- All living organisms are made of cells.
- Cell is the basic structural and functional unit of life.
- New cells arise from pre-existing cells.
Q2. Why is the cell called the functional unit of life?
Answer:
All life activities like respiration, digestion, excretion, and growth occur inside cells. Therefore, cells perform all functions necessary for life.
Q3. What are biomolecules?
Answer:
Biomolecules are organic compounds present in living organisms such as proteins, carbohydrates, lipids, and nucleic acids.
Q4. Explain Reductionist Biology.
Answer:
Reductionist Biology studies living organisms at molecular and chemical levels using concepts of physics and chemistry.
4. Long Answer Questions
Q1. Explain the importance of cell theory.
Answer:
Cell theory is important because:
- It explains that all organisms are made of cells.
- It provides unity among living organisms despite differences.
- It states that the cell is the basic unit of structure and function.
- It explains growth and reproduction through cell division.
- It helps in understanding diseases and body functions.
Q2. Explain the role of biomolecules in living organisms.
Answer:
Biomolecules are essential compounds present in cells.
- Carbohydrates provide energy.
- Proteins help in body building and enzyme action.
- Lipids form cell membranes and store energy.
- Nucleic acids control heredity and genetic information.
They help in all physiological activities of the body.
5. Assertion and Reason Questions
Q1.
Assertion (A): Cell is the basic unit of life.
Reason (R): All life activities occur inside cells.
a) Both A and R are true and R is the correct explanation of A.
b) Both A and R are true but R is not the correct explanation.
c) A is true but R is false.
d) A is false but R is true.
Answer: a)
Q2.
Assertion (A): Biomolecules are absent in living organisms.
Reason (R): Biomolecules help in physiological processes.
Answer: Assertion is false but Reason is true.
6. Fill in the Blanks
-
The basic unit of life is the ________.
Answer: Cell -
New cells arise from ________ cells.
Answer: pre-existing -
Proteins, carbohydrates, and lipids are called ________.
Answer: biomolecules -
Study of body functions is called ________.
Answer: physiology -
Cell theory was proposed by ________ and ________.
Answer: Schleiden and Schwann
7. Match the Columns
| Column A | Column B |
|---|---|
| 1. Cell | a. Genetic material |
| 2. Protein | b. Basic unit of life |
| 3. DNA | c. Energy source |
| 4. Carbohydrate | d. Enzyme formation |
Answers:
1 → b
2 → d
3 → a
4 → c
8. Statement-Based Questions
Q1. Read the statement carefully:
“All living organisms are made up of cells.”
What does this statement represent?
Answer: It represents the Cell Theory.
Q2. “Biomolecules control physiological activities.”
Name any two physiological activities.
Answer: Digestion and respiration.
9. Case Study Questions
Case Study 1
A scientist studied tissues of living organisms and found the presence of proteins, carbohydrates, lipids, and nucleic acids. He concluded that these compounds control all life processes.
Questions:
Q1. What are these compounds called?
Answer: Biomolecules.
Q2. Which biomolecule stores genetic information?
Answer: Nucleic acids.
Q3. Which biomolecule provides energy?
Answer: Carbohydrates.
Q4. Which branch studies life at molecular level?
Answer: Reductionist Biology.
10. Important One-Word Questions
| Question | Answer |
|---|---|
| Functional unit of life | Cell |
| Scientist who added to cell theory | Virchow |
| Study of body functions | Physiology |
| Genetic material | DNA |
| Energy-giving biomolecule | Carbohydrate |
11. Extra Exam Practice Questions
Q1. Why are cells important?
Answer: Cells are important because they perform all life processes and form the body structure of organisms.
Q2. Name four biomolecules.
Answer: Proteins, carbohydrates, lipids, nucleic acids.
Q3. What is the molecular basis of life?
Answer: The functioning of biomolecules inside cells forms the molecular basis of life.
Important NEET Points to Remember
Cell Theory
- Proposed by:
- Schleiden → plants made of cells
- Schwann → animals made of cells
- Virchow added:
- “Omnis cellula e cellula”
- New cells arise from pre-existing cells.
Key Definitions
| Term | Meaning |
|---|---|
| Cell | Basic unit of life |
| Biomolecule | Chemical compound in living organisms |
| Physiology | Study of body functions |
| Reductionist Biology | Studying life at molecular level |
Quick Revision (One-Liners)
- All living organisms are made of cells.
- Cell is the structural and functional unit of life.
- Biomolecules control all life activities.
- Biology uses principles of chemistry and physics.
- Study of molecules helps understand diseases.
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