⭐ Sabse Important Points · एक नज़र में
- SI Base Units: Seven fundamental units: metre (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), candela (luminous intensity).
- Prokaryotic vs Eukaryotic: Prokaryotes have no nucleus and 70S ribosomes; eukaryotes have a nucleus and 80S ribosomes (except mitochondria/chloroplasts have 70S).
- Dimensional Formula: Expresses a physical quantity in terms of base dimensions (M, L, T, A, K, mol, cd). Used to check homogeneity of equations.
- Mitochondria: Site of aerobic respiration and ATP production; has double membrane; inner membrane folded into cristae; contains its own DNA (mtDNA).
- Significant Figures: Indicate precision of a measurement. Rules: non-zero digits are significant; zeros between non-zero digits are significant; leading zeros are not; trailing zeros after decimal are significant.
- Plasma Membrane: Selectively permeable; composed of phospholipid bilayer with embedded proteins (fluid mosaic model).
Introduction · परिचय
General Science for BPSC covers fundamental concepts from Physics, Chemistry, and Biology, with emphasis on everyday applications and basic principles. This short revision note focuses on two high-yield areas: Units and Measurement (Physics) and Cell Biology (Biology), which frequently appear in BPSC Prelims.
Units and Measurement
Measurement in science requires standard units. The International System of Units (SI) is the modern form of the metric system and is used globally. It has seven base units from which all other units are derived. Understanding prefixes and dimensional analysis helps in solving numerical problems and checking equation correctness.
📐 Formula / Rule Box · सूत्र याद रखो
Dimensional formula of force
[M L T^-2]
Dimensional formula of work/energy
[M L^2 T^-2]
Dimensional formula of pressure
[M L^-1 T^-2]
Dimensional Formula
Expresses a physical quantity in terms of base dimensions (M, L, T, A, K, mol, cd). Used to check homogeneity of equations.
⭐ Key Points · याद रखने वाली बातें
- SI Base Units: Seven fundamental units: metre (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), candela (luminous intensity).
- Significant Figures: Indicate precision of a measurement. Rules: non-zero digits are significant; zeros between non-zero digits are significant; leading zeros are not; trailing zeros after decimal are significant.
✍️ Solved Example 1 · हल किया हुआ उदाहरण
❓ Question: Find the dimensional formula of force.
✅ Solution: [M L T^-2]
💡 Explanation: Force = mass × acceleration. Acceleration = velocity/time = (length/time)/time = L T^-2. Thus, force dimension = M × L T^-2 = [M L T^-2].
Cell Biology: Structure and Functions
The cell is the basic structural and functional unit of life. Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a true nucleus and organelles. Key organelles include mitochondria (powerhouse), ribosomes (protein synthesis), chloroplasts (photosynthesis in plants), and lysosomes (suicidal bags).
| Feature | Prokaryotic Cell | Eukaryotic Cell |
|---|---|---|
| Nucleus | Absent | Present |
| Ribosome | 70S | 80S (70S in organelles) |
| Membrane-bound organelles | Absent | Present |
| Cell size | 1-10 µm | 10-100 µm |
⭐ Key Points · याद रखने वाली बातें
- Prokaryotic vs Eukaryotic: Prokaryotes have no nucleus and 70S ribosomes; eukaryotes have a nucleus and 80S ribosomes (except mitochondria/chloroplasts have 70S).
- Mitochondria: Site of aerobic respiration and ATP production; has double membrane; inner membrane folded into cristae; contains its own DNA (mtDNA).
- Plasma Membrane: Selectively permeable; composed of phospholipid bilayer with embedded proteins (fluid mosaic model).
✍️ Solved Example 1 · हल किया हुआ उदाहरण
❓ Question: Which organelle is known as the 'suicidal bag' of the cell?
✅ Solution: Lysosome
💡 Explanation: Lysosomes contain hydrolytic enzymes that can digest the cell's own components if the membrane ruptures, hence called suicidal bags.
Practice Questions · खुद हल करके देखो
पहले खुद try karo, phir “Answer dekho” dabakar check karo. 👇
Q1Which of the following is not an SI base unit? (a) Kelvin (b) Mole (c) Newton (d) Candela
👀 Answer dekho
✅ Answer: (c) Newton
💡 Explanation: Newton is a derived unit of force (kg·m/s²). The seven SI base units are metre, kilogram, second, ampere, kelvin, mole, and candela.
Q2The dimensional formula of pressure is: (a) [M L T^-2] (b) [M L^-1 T^-2] (c) [M L^2 T^-2] (d) [M L^-2 T^-2]
👀 Answer dekho
✅ Answer: (b) [M L^-1 T^-2]
💡 Explanation: Pressure = Force/Area = [M L T^-2] / [L^2] = [M L^-1 T^-2].
Q3Which organelle contains its own DNA and ribosomes? (a) Lysosome (b) Mitochondrion (c) Golgi apparatus (d) Endoplasmic reticulum
👀 Answer dekho
✅ Answer: (b) Mitochondrion
💡 Explanation: Mitochondria are semi-autonomous organelles containing circular DNA and 70S ribosomes, enabling them to synthesize some proteins.
⚠️ Common Mistakes · ये गलतियाँ बिल्कुल मत करना
- Confusing mass and weight: Mass is a base quantity (kg), weight is a derived quantity (force, N). Avoid using 'weight' in kg in calculations.
- Forgetting that zeros between non-zero digits are significant (e.g., 1002 has 4 significant figures).
- Mixing up prokaryotic and eukaryotic ribosome sizes: Prokaryotes have 70S, eukaryotes have 80S (except organelles).
⚡ Quick Revision · Exam से पहले 2 मिनट में दोहराओ
- SI Base Units: Seven fundamental units: metre, kilogram, second, ampere, kelvin, mole, candela.
- Dimensional Analysis: Used to check equation correctness; force = [M L T^-2], energy = [M L^2 T^-2].
- Cell Organelles: Mitochondria = powerhouse; ribosome = protein factory; lysosome = suicidal bag; chloroplast = photosynthesis.