Class 11 Biology - KARNATAKA
Cell: The Unit of Life
The chapter 'Cell: The Unit of Life' forms the foundation of all biological sciences in the Class 11 Karnataka KSEEB syllabus. It introduces students to the basic structural and functional unit of living organisms. You will learn about cell theory, the detailed differences between prokaryotic and eukaryotic cells, and the ultra-structure of plant and animal cells. Key organelles such as the nucleus, mitochondria, chloroplasts, and ribosomes are explored in depth regarding their structure and functions. Understanding this chapter is crucial because it bridges microscopic biology with physiology and genetics, frequently appearing in board exams as both short and long-answer questions.
Start Learning FreeKey Concepts
Cell Theory
Proposed by Schleiden, Schwann, and later modified by Rudolf Virchow, it states that all living organisms are composed of cells and products of cells, and all cells arise from pre-existing cells.
Prokaryotic vs Eukaryotic Cells
Prokaryotic cells lack a membrane-bound nucleus and true organelles (e.g., bacteria), whereas eukaryotic cells possess a distinct, membrane-bound nucleus and various membrane-bound organelles (e.g., plant and animal cells).
Plasma Membrane Structure
Described by the Fluid Mosaic Model proposed by Singer and Nicolson, the cell membrane is made of a phospholipid bilayer with embedded proteins that provide fluidity and selective permeability.
Endomembrane System
A coordinated group of membranous organelles including the Endoplasmic Reticulum (ER), Golgi apparatus, lysosomes, and vacuoles that work together to modify, package, and transport lipids and proteins.
Mitochondria and Plastids
Mitochondria are the 'powerhouses of the cell' responsible for ATP production via aerobic respiration, while plastids (like chloroplasts) are found in plant cells and handle photosynthesis.
Important Formulas
Board Exam Info
In the Karnataka (KSEEB) Class 11 Biology board examinations, this chapter typically carries around 6 to 8 marks. Questions usually include 1-mark multiple-choice or fill-in-the-blank questions, 2 or 3-mark short answer questions (such as differences between plant and animal cells or prokaryotes and eukaryotes), and occasional 5-mark long-answer questions requiring a well-labeled diagram of a plant/animal cell or the fluid mosaic model of the plasma membrane.
Frequently Asked Questions
70S ribosomes are smaller and found in prokaryotic cells, as well as inside mitochondria and chloroplasts of eukaryotes. They consist of 50S and 30S subunits. 80S ribosomes are larger, found in the cytoplasm of eukaryotic cells, and consist of 60S and 40S subunits.
Why are mitochondria called the powerhouses of the cell?
Mitochondria are the sites of aerobic respiration where cellular energy is generated in the form of ATP (Adenosine Triphosphate) through the Krebs cycle and electron transport chain, which is then used for various metabolic activities.
Do plant and animal cells have the same organelles?
Most organelles like the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus are common to both. However, plant cells have a rigid cell wall, large central vacuoles, and plastids (like chloroplasts), which are typically absent in animal cells. Animal cells instead possess centrioles.
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