| Prokaryotic Cell |
Eukaryotic Cell |
Lacks a membrane-bound nucleus. |
Has a true membrane-bound nucleus. |
Membrane-bound organelles are absent. |
Membrane-bound organelles (e.g., mitochondria) are present. |
4. Mention the functions of lysosome. [2]
Intracellular digestion of macromolecules.
Autophagy (digestion of old or damaged organelles).
Autolysis (self-destruction of the cell).
5. Mention important functions of peroxisome. [2]
Breakdown of fatty acids through beta-oxidation.
Detoxification of harmful substances (like alcohol) in the liver.
Conversion of hydrogen peroxide to water and oxygen by catalase.
6. Why is mitochondria called powerhouse of the cell? [2]
Mitochondria are called the powerhouse of the cell because they are the primary sites of ATP (Adenosine Triphosphate) production through cellular respiration
.
7. What are microtubules? [2]
Microtubules are hollow, microscopic cylinders made of tubulin protein that form part of the cytoskeleton and play key roles in maintaining cell shape and facilitating cell division
.
8. What are nucleosomes? [2]
A nucleosome is the basic structural unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a core of eight histone proteins
.
9. Define cell cycle. [2]
The cell cycle is an ordered series of events involving cell growth and DNA replication that produces two new daughter cells
.
10. What is pseudostratified epithelial tissue? [2]
It is a type of simple epithelium that appears layered (stratified) because the nuclei are at different levels, even though every cell is attached to the basement membrane
.
11. Differentiate between tendon and ligament. [2]
Tendon: Connects skeletal muscle to bone.
Ligament: Connects bone to bone.
12. What is Haversian system? [2]
The Haversian system (or osteon) is the fundamental functional unit of compact bone, consisting of concentric layers of bone tissue surrounding a central canal containing blood vessels and nerves
.
13. Enlist the locations of smooth muscle in human body. [2]
Walls of hollow organs (stomach, intestines).
Walls of blood vessels.
Urinary bladder and respiratory tracts.
14. What are glial cells? [2]
Glial cells (neuroglia) are non-neuronal cells in the nervous system that provide support, nutrition, and protection for neurons
.
15. What is neuromuscular junction? [2]
A neuromuscular junction is a chemical synapse formed by the contact between a motor neuron and a muscle fiber, allowing the transmission of nerve impulses to cause muscle contraction
.
SECTION-B
Answer any five of the following questions (All solved for full coverage):
16. Describe the fluid-mosaic model of plasma membrane with a suitable diagram. Add a note on its functions. [8+2=10]
The fluid-mosaic model, proposed by Singer and Nicolson, describes the plasma membrane as a fluid lipid bilayer with embedded "mosaic" proteins
.
Lipid Bilayer: Composed of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward.
Proteins: Integral proteins span the membrane, while peripheral proteins are attached to the surface.
Cholesterol: Regulates membrane fluidity.
Functions: Acts as a selective barrier, facilitates cell signaling, and provides structural support.
17. Discuss the structure and functions of tight junctions and gap junctions. [5+5=10]
Tight Junctions: Specialized connections where the membranes of adjacent cells are pressed tightly against each other, sealed by specific proteins (claudins and occludins)
. They prevent the leakage of extracellular fluid.
Gap Junctions: Channels (connexons) that connect the cytoplasm of adjacent cells, allowing the passage of ions and small molecules
. They facilitate rapid chemical and electrical communication between cells, such as in cardiac muscle.
18. Describe the structure and functions of endoplasmic reticulum (ER). [6+4=10]
The ER is a network of membranous tubules and sacs called cisternae
.
Rough ER (RER): Studded with ribosomes; functions in protein synthesis and modification.
Smooth ER (SER): Lacks ribosomes; functions in lipid synthesis, detoxification, and calcium storage.
19. Describe the structure and functions of nucleus. Add a note on the functions of nucleolus. [8+2=10]
The nucleus is the control center of the cell, enclosed by a double-membrane nuclear envelope containing nuclear pores
. It contains nucleoplasm and chromatin (genetic material).
Functions: Stores genetic information, controls gene expression, and regulates cell division
.
Functions of Nucleolus: The nucleolus is the site of ribosomal RNA (rRNA) synthesis and the assembly of ribosomal subunits
.
20. What is cytoskeleton? Describe the structure of a microfilament with suitable diagram and mention its functions. [2+6+2=10]
Cytoskeleton: A network of protein fibers (microtubules, microfilaments, and intermediate filaments) that provides structural support and facilitates cell motility
.
Microfilament Structure: Composed of two intertwined strands of the protein actin
.
Functions: Maintaining cell shape, muscle contraction (with myosin), and amoeboid movement
.
21. Explain the key events that occur in each phase of cell cycle. Add a note on G1 checkpoint. [7+3=10]
Interphase: Includes G1 (cell growth), S (DNA replication), and G2 (preparation for mitosis).
M Phase (Mitosis): Division of the nucleus (Prophase, Metaphase, Anaphase, Telophase).
Cytokinesis: Division of the cytoplasm.
G1 Checkpoint: The primary point at which the cell must choose whether or not to divide
. It checks for cell size, nutrients, growth factors, and DNA damage.
22. What is epithelial tissue? Explain the structure with diagram and functions of simple epithelial tissue. [2+8=10]
Epithelial Tissue: A tissue composed of closely packed cells that covers body surfaces and lines internal organs
.
Simple Epithelial Tissue: Consists of a single layer of cells
. Types include:
Simple Squamous: Flat cells; functions in diffusion.
Simple Cuboidal: Cube-shaped; functions in secretion and absorption.
Simple Columnar: Tall cells; found in digestive tract.
23. What are adipocytes? Describe the structure of three main types of cartilage. Add a note on the functions of cartilage. [2+6+2=10]
Adipocytes: Specialized fat cells that store energy as lipids
.
Three Types of Cartilage:
Hyaline Cartilage: Most common; has clear matrix; found in joints.
Elastic Cartilage: Contains elastic fibers; found in external ear.
Fibrocartilage: Contains thick collagen fibers; provides high strength; found in intervertebral discs.
Functions: Provides structural support, cushions joints, and acts as a precursor for bone formation
.
24. Describe the structure and functions of a myelinated neuron. Add a note on different types of neuron based on polarity. [7+3=10]
A myelinated neuron consists of a cell body, dendrites, and an axon covered by a fatty myelin sheath produced by Schwann cells
. The gaps in the sheath are called Nodes of Ranvier.
Functions: Saltatory conduction of nerve impulses (increases speed)
.
Types based on Polarity: Unipolar (one process), Bipolar (two processes), and Multipolar (multiple processes)
.
25. What is synapse? Differentiate between chemical synapse and electrical synapse. Describe the structure of different chemical synapses. [2+2+6=10]
Synapse: A junction between two neurons where information is transmitted
.
Differences:
Chemical Synapse: Uses neurotransmitters; slower; unidirectional.
Electrical Synapse: Uses gap junctions; faster; often bidirectional.
Chemical Synapse Structure: Consists of a presynaptic terminal (containing vesicles), a synaptic cleft, and a postsynaptic membrane (containing receptors)
.
Exam Focus Enhancements
Important Summary
Cell Theory: All living things are made of cells.
Mitochondria: Powerhouse (ATP).
Nucleus: Genetic control center.
Cartilage Types: Hyaline, Elastic, Fibrocartilage.
Exam Tips
- Always label diagrams clearly (e.g., Plasma Membrane, Nucleus).
- For 10-mark questions, use headings and bullet points for readability.
- Distinguish clearly between "Tendon" and "Ligament" as they are common confusion points.