General Q&A for Class 12 · Page 244
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
The composition of cell wall varies in different groups of living organisms. Comment.
Answer: Cell wall chemical composition varies across taxonomic groups: Organism Cell Wall Composition Characteristics Bacteria Peptidoglycan (murein): NAG + NAM + sh
- GeneralClass 12All
Explain the following: (a) Passive transport (b) Active transport
a) Passive Transport Definition: Movement of molecules across cell membrane without energy expenditure (no ATP) Characteristics: Along concentration gradient (high → low) Spontaneous process (thermodynamically favorable) Continues until equilibrium reached Membrane plays passive role </
- GeneralClass 12All
Mention five differences between plant and animal cell.
Answer: Feature Plant Cell Animal Cell 1. Cell Wall Present (cellulose, rigid) Absent (only plasma membrane) <td
- GeneralClass 12All
Define the following: (a) Polyribosome (b) Plasmids (c) Cristae
(a) Polyribosome (Polysome) Definition: A cluster of multiple ribosomes (often 5–10) attached to a single mRNA strand Occurrence: In both prokaryotes and eukaryotes Function: Simultaneous translation of mRNA by multiple ribosomes → rapid protein synthesis Significance: Increases translational eff
- GeneralClass 12All
Give differences between cis and trans face of Golgi Body.
Feature Cis Face (Forming Face) Trans Face (Maturing Face) Position Closer to nucleus and ER Closer to plasma membrane <t
- GeneralClass 12All
Draw a well-labelled diagram of a plant cell.
[Refer to diagram in original PDF showing all major organelles]: Cell wall, Plasma membrane, Cytoplasm Nucleus (with nucleolus, nuclear envelope) Chloroplasts, Mitochondria Rough ER, Smooth ER, Golgi apparatus Vacuole (large central sap vacuole) Ribosomes, Peroxisomes Plasmodesmata, Middle lamella Microtubules Distinctive plant cell features: Cell wall</
- GeneralClass 12All
Explain the cell wall, plasma membrane and cytoplasm of a prokaryotic cell.
Cell Wall and Plasma Membrane Cell Wall: Rigid structure providing shape and protection Composition: Peptidoglycan (NAG-NAM polymer cross-linked by peptides) Types: Gram-positive: Thick peptidoglycan (stains purple) Gram-negative: Thin peptidoglycan + outer lip
- GeneralClass 12All
What are the three basic structures of a cell? Explain.
All cells possess three fundamental components: 1. Plasma Membrane (Cell Membrane) Structure: Phospholipid bilayer with embedded proteins (fluid mosaic model) Function: Forms selective barrier between cell and environment Regulates transport of substances Cell recognition and signaling <l
- GeneralClass 12All
Write a contribution of the following scientists in the field of cytology.
Scientist Year Contribution (a) Anton van Leeuwenhoek 1674 First to observe and describe living cells (bacteria, protozoa) using simple microscope; called them "animalcules</
- GeneralClass 12All
Explain the structure found in nucleus which is responsible for rRNA synthesis.
Nucleolus (plural: nucleoli) Structure: Spherical, electron-dense body Located in nucleoplasm Not membrane-bound Larger and more numerous in cells with high protein synthesis activity Composition: Ribosomal DNA (rDNA) – genes encoding rRNA Proteins</str
- GeneralClass 12All
Draw a well-labelled diagram of chloroplast.
Refer to diagram in original PDF showing]: Outer membrane (smooth, permeable) Inner membrane (selective barrier) Stroma (fluid-filled matrix) Thylakoids (flattened membrane sacs) Grana (stacks of thylakoids) Stroma lamellae (intergranal connections) Additional notes: Thylak
- GeneralClass 12All
(a) What is the difference between two membranes of mitochondria? (b) What does mitochondrial matrix contain?
(a) Mitochondrial membranes: Feature Outer Membrane Inner Membrane Structure Smooth, continuous Highly folded into cristae <td wid
- GeneralClass 12All
Write a short note on lysosomes.
Lysosomes – "Suicidal bags" or "Cellular digestive system" Structure: Single membrane-bound spherical vesicles (0.2–0.8 µm) Evenly distributed in cytoplasm Budded from Golgi apparatus Composition: ~40 types of hydrolytic enzymes: Proteases (
- GeneralClass 12All
Give the differences between SER and RER.
Feature Smooth ER (SER) Rough ER (RER) Ribosomes Absent Present (attached to cytoplasmic surface) Appearance <td width="26
- GeneralClass 12All
Explain the secondary cell wall.
Secondary cell wall characteristics: Location: Deposited internal to the primary cell wall (between primary wall and plasma membrane) Timing: Forms after cell has stopped growing Composition: High cellulose content (organized in parallel microfibrils) Lignin (in woody tissues) – provides rigidity a
- GeneralClass 12All
Write a short note on facilitated diffusion.
Facilitated diffusion is a type of passive transport with these characteristics: Energy requirement: None (no ATP used) Direction: Along concentration gradient (high → low concentration) Mechanism: Requires carrier proteins (permeases) or channel proteins Specificity: Highly selective for spec
- GeneralClass 12All
Explain the types of proteins found in cell membrane. Who gave fluid mosaic model of plasma membrane?
Membrane proteins: Type Characteristics Functions Integral (Intrinsic) Embedded in lipid bilayer; amphipathic; may span entire membrane (transmembrane proteins) <td width="202"
- GeneralClass 12All
Explain the different components of bacterial flagellum.
The bacterial flagellum consists of three parts: Component Structure Function Filament Longest portion; helical protein (flagellin); extends outside cell Pro
- GeneralClass 12All
When will you suppose that the cell is dead?
A cell is considered dead when its protoplasm ceases to function. Protoplasm (cytoplasm + nucleoplasm) is termed the "physical basis of life" because: It is the site of all metabolic activities Contains enzymes, genetic material, and organelles Maintains homeostasis and energy production</li
- GeneralClass 12All
Explain the cell wall of bacteria.
Bacterial cell wall features: Location: Between glycocalyx (outermost) and plasma membrane (innermost) Composition: Peptidoglycan (murein/mucopeptide) Polymer of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) Cross-linked by short peptide chains Properties