Cell: The Unit of Life 11 Biology — Revision Notes
The cell is the basic unit of life and all living organisms are composed of one or more cells. Understanding cell structure and function is fundamental to
TL;DR: The cell is the basic unit of life and all living organisms are composed of one or more cells. Understanding cell structure and function is fundamenta…
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The cell is the basic unit of life and all living organisms are composed of one or more cells. Understanding cell structure and function is fundamental to
Cell Theory
- All living organisms are composed of cells
- Cell is the basic unit of life
- All cells arise from pre-existing cells through cell division
- Established by scientists like Schleiden, Schwann, and Virchow
- Theory explains how life originates and propagates
Prokaryotic Cells
- Lack membrane-bound nucleus; genetic material in nucleoid region
- Smaller than eukaryotic cells, typically 0.5 to 5 micrometers
- Include bacteria and archaea
- Have cell membrane but lack membrane-bound organelles
- Ribosomes are 70S type and smaller than eukaryotic ribosomes
Eukaryotic Cell Structure
- Nucleus contains genetic material and controls cell functions
- Mitochondria produces energy through aerobic respiration
- Endoplasmic reticulum synthesizes proteins and lipids
- Golgi apparatus modifies and packages proteins
- Lysosomes contain enzymes for breaking down waste
Cell Membrane Structure and Function
- Selectively permeable barrier controlling substance movement
- Phospholipid bilayer provides basic structure
- Proteins embedded in membrane perform various functions
- Allows nutrient entry and waste removal
- Maintains ion concentrations and cell homeostasis
Cell Division Processes
- Mitosis produces two identical daughter cells for growth and repair
- Meiosis produces four haploid gametes for sexual reproduction
- Binary fission in prokaryotes produces two identical cells
- Cell cycle has G1, S, G2, and M phases
- Checkpoints control progression through cell cycle
Key Terms
- Cell: Basic unit of life and smallest living entity
- Mitochondria: Organelle that produces energy through cellular respiration
- Nucleus: Membrane-bound organelle containing genetic material
- Enzyme: Protein that catalyzes biochemical reactions in cells
Frequently Asked Questions
Why are mitochondria called the powerhouse of the cell?
Mitochondria produce ATP through aerobic respiration, which is the primary energy currency of cells. ATP powers nearly all cellular activities.
What is the main difference between mitosis and meiosis?
Mitosis produces two identical diploid daughter cells for body growth. Meiosis produces four non-identical haploid cells for sexual reproduction.
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