Questions and Answers
What is the study of structure and composition of a cell called?
Who first observed a cell in a dead cork slice?
What is the physical basis of life?
What is an example of a unicellular organism?
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What is the characteristic of prokaryotic cells?
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What is an example of a multicellular organism?
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What is the Greek word that the term 'cell' is derived from?
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Who discovered the first living cell?
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What is the main function of the plasma membrane?
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What is the primary component of the cell wall?
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Who discovered the nucleus?
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What is the function of the nuclear membrane?
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What is the main function of the cytoplasm?
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What is the characteristic of the cell wall?
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What is the function of chromosomes or chromatin material?
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What is absent in animal cells?
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What is the main function of the endoplasmic reticulum?
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Which type of endoplasmic reticulum is involved in protein synthesis?
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What is the function of the Golgi apparatus in lipid synthesis?
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Which organelle is absent in prokaryotes and mammalian RBCs?
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What is the function of smooth endoplasmic reticulum?
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What is the main function of the Golgi apparatus?
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Which scientist discovered the endoplasmic reticulum?
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What is the function of the Golgi apparatus in melanin synthesis?
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Where do light reactions of photosynthesis take place?
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What is the function of vacuoles in plant cells?
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Who discovered lysosomes?
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What is the main function of lysosomes?
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What is the primary function of peroxisomes in plant cells?
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Where are glyoxysomes found?
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What is the process by which fat is converted into carbohydrates in glyoxysomes?
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What is the common feature of lysosomes and peroxisomes?
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What is the main characteristic of totipotent stem cells?
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What is the main function of glyoxysomes?
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What is the main difference between plant and animal cells in terms of vacuoles?
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What is the term for the ability of stem cells to differentiate into different cell types?
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What is an example of a potential application of stem cells in medicine?
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What is the main difference between embryonic stem cells and adult stem cells?
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What is the term for stem cells that can develop into many cell types, but not all cell types?
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What is the purpose of induced pluripotent stem cells?
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Study Notes
Cell Structure and Functions
- A cell is the basic structural and functional unit of all life forms.
- Study of cell structure and composition is called Cytology.
- Cell was first observed by Robert Hooke in 1665 and the word "cell" was derived from the Greek word "Cellulae" meaning small room.
Types of Cells and Organisms
- Organisms can be categorized into unicellular and multicellular organisms based on the number of cells.
- Unicellular organisms: made up of single cell only, e.g. Amoeba.
- Multicellular organisms: made up of numerous cells, e.g. Plants and animals.
- Cells can also be categorized into prokaryotic and eukaryotic cells based on the type of organization.
- Prokaryotic cells: primitive and incomplete cells, e.g. Bacteria.
- Eukaryotic cells: well-developed cells, e.g. Plants and animals.
Plasma Membrane
- The fluid mosaic model of plasma membrane consists of a protein layer sandwiched between two layers of lipids.
- Functions of plasma membrane:
- Regulates the movement of molecules inside and outside the cell.
- Helps in maintaining the distinct composition of the cell.
- Transportation of molecules across the plasma membrane.
Cell Wall
- The outermost covering of plant cells, absent in animal cells.
- Made up of cellulose and hemicelluloses.
- Functions of cell wall:
- Provides definite shape to the cell.
- Provides strength to the cell.
- Allows entry of molecules of different sizes.
- Antigen specific.
- Has the characteristics of repair and regeneration.
Nucleus
- The most important cell organelle that directs and controls all cellular activities.
- Called the "Headquarter of the cell".
- Discovered by Robert Brown in 1831.
- In eukaryotes, a well-defined nucleus is present, while in prokaryotes, a well-defined nucleus is absent.
- Nuclear membrane has pores that regulate the movement of materials in and out of the cell.
- Nucleus also contains nucleolus and chromatin material.
- Function of the nucleus:
- Controls all metabolic activities of the cell and regulates the cell cycle.
- Helps in transmission of hereditary characters from parents to offsprings.
Cytoplasm
- Discovered by Kolliker in 1862.
- The site of both biosynthetic and catabolic pathways.
- Can be divided into two parts:
- Cytosol: aqueous soluble part containing various fibrous proteins forming cytoskeleton.
- Cell organelles: living part of the cells having definite shape, structure, and function bounded by plasma membrane.
Endoplasmic Reticulum (ER)
- Network of membranes present in the cytoplasm.
- Discovered by Porter, Claude, and Fullam.
- Present in all cells except prokaryotes and mammalian erythrocytes.
- Made up of three components:
- Cistemae: long, flattened, parallelly arranged, unbranched tubules.
- Types: Smooth ER and Rough ER.
- Function of ER:
- Transport of materials between various regions of cytoplasm and between cytoplasm and nucleus.
- Functions as a cytoplasmic framework for biochemical activities.
- Forms endoskeleton of cell.
- Helps in synthesis of fats, steroids, cholesterol, etc.
- Contains secretory proteins.
- SER plays a crucial role in detoxification of drugs and poisonous substances.
Golgi Apparatus
- Consists of single membrane-bound vesicles arranged parallel to each other in stacks called cisternae along with some large and spherical vacuoles.
- Discovered by Camilo Golgi.
- Absent in prokaryotes, mammalian RBCs, and sieve cells.
- Functions:
- Helps in formation of lipids.
- Helps in formation of middle lamellae.
- Secretary in nature.
- Helps in melanin synthesis.
- Lipids and proteins synthesized in endoplasmic reticulum are packed at Golgi complex.
Vacuoles
- Membrane-bound regions in the cytoplasm containing water and other substances.
- Bounded by a single membrane called Tonoplast.
- Functions:
- Helps in maintaining osmotic pressure in a cell.
- Stores toxic metabolic products of plant cells.
- Contains various colored pigments like anthocyanins.
Lysosomes
- Discovered by Christian de Duve.
- Tiny sac-like granules containing enzymes of intracellular digestion.
- Single membrane-bound organelles present only in animal cells.
- Functions:
- Phagy = digestion.
- Kind of waste disposal system.
- Help in digesting foreign materials and worn-out cells.
Peroxisomes
- Ovoid or granular structures, limited by a single membrane.
- Carry out photorespiration in plant cells.
- Carry out lipid metabolism in animal cells.
- Contain important enzymes as oxidases, peroxidases, and catalases.
Glyoxysomes
- Single membrane-bound organelles.
- Found in plant cells, particularly in germinating fatty seeds, e.g. Ricinus (castor) and groundnut.
- Contain important enzymes, isocitrate, lyase, maltase.
- Fat is converted into carbohydrates by a process called glyoxylate cycle.
Difference between Plant and Animal Cells
- Cell wall: present in plant cells, absent in animal cells.
- Plastids: present in plant cells, absent in animal cells.
- Vacuoles: large in plant cells, small, numerous, and absent in animal cells.
- Centrioles: absent in plant cells, present in animal cells.
- Position of nucleus: periphery in plant cells, centre in animal cells.
- Nutrition: autotrophic in plant cells, heterotrophic in animal cells.
Stem Cells and their Applications
- Undifferentiated cells that can be converted into other cell types and can divide to form similar cells.
- Types of stem cells:
- Embryonic stem cells (ESCs).
- Adult stem cells (somatic stem cells).
- Induced pluripotent stem cells.
- Property of stem cells to differentiate into different cell types is called Potency.
- Totipotent stem cells: single cell can be converted into any cell type.
- Pluripotent stem cells: single cell can be converted into many cell types.
- Multipotent stem cells: single cell can be converted into more than one cell type.
- Oligopotency: single cell can be converted into few cell types.
- Applications of stem cells:
- Whole organ manufacture.
- Injecting cells into the site of degeneration.
- Personalized medicines.
- Regenerative medicine.
- Organ transplantations.
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Quiz on the basics of cell structure and functions, including the discovery of cells and their composition. Learn about the role of cells in living organisms and their importance in cytology.
