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Questions and Answers
Who discovered cells, and how?
Who discovered cells, and how?
Robert Hooke discovered cells in 1665 by observing them in a cork slice with the help of a primitive microscope.
Why is the cell called the structural and functional unit of life?
Why is the cell called the structural and functional unit of life?
The cell is called the structural and functional unit of life because all living organisms are composed of cells, and cells perform various functions that are characteristic of all living forms.
What is the structural organisation of a cell?
What is the structural organisation of a cell?
A cell has components called organelles, which are specialized structures inside the cell.
What is the name of the movement of water molecules through a selectively permeable membrane?
What is the name of the movement of water molecules through a selectively permeable membrane?
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Living cells, not dead cells, are able to absorb water by osmosis. True or False?
Living cells, not dead cells, are able to absorb water by osmosis. True or False?
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What is the name of the outer covering outside the plasma membrane in plant cells?
What is the name of the outer covering outside the plasma membrane in plant cells?
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What is the function of the nucleus in a cell?
What is the function of the nucleus in a cell?
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Prokaryotic cells are generally ____________ in size.
Prokaryotic cells are generally ____________ in size.
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In prokaryotic cells, the nuclear region is ____________ and ____________.
In prokaryotic cells, the nuclear region is ____________ and ____________.
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Prokaryotic cells have ____________ chromosome.
Prokaryotic cells have ____________ chromosome.
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Prokaryotic cells lack ____________ cell organelles.
Prokaryotic cells lack ____________ cell organelles.
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What is the function of the endoplasmic reticulum (ER)?
What is the function of the endoplasmic reticulum (ER)?
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What is the function of the Golgi apparatus?
What is the function of the Golgi apparatus?
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What is the function of lysosomes?
What is the function of lysosomes?
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What is the difference between prokaryotic and eukaryotic cells?
What is the difference between prokaryotic and eukaryotic cells?
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Name the two organelles we have studied that contain their own genetic material.
Name the two organelles we have studied that contain their own genetic material.
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Why are lysosomes known as suicide bags?
Why are lysosomes known as suicide bags?
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Where are proteins synthesized inside the cell?
Where are proteins synthesized inside the cell?
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What organelle is known as the powerhouse of the cell and why?
What organelle is known as the powerhouse of the cell and why?
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Where do lipids and proteins constituting the cell membrane get synthesized?
Where do lipids and proteins constituting the cell membrane get synthesized?
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What is osmosis?
What is osmosis?
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Which type of cell division is required for growth and repair of the body, and which type is involved in the formation of gametes?
Which type of cell division is required for growth and repair of the body, and which type is involved in the formation of gametes?
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Study Notes
The Fundamental Unit of Life
Discovery of Cells
- Robert Hooke discovered cells in 1665 while examining a thin slice of cork
- He observed that the cork resembled a honeycomb structure with many little compartments
- He called these boxes "cells," which is Latin for "a little room"
Cell Structure
- Cells are the basic building units of all living organisms
- Cells have three main features: plasma membrane, nucleus, and cytoplasm
- Each cell organelle performs a special function, such as making new material, clearing waste, and more
Plasma Membrane
- The plasma membrane is the outermost covering of the cell
- It separates the cell's contents from the external environment
- It is selectively permeable, allowing certain substances to pass through while keeping others out
- The plasma membrane allows for the exchange of gases and water through diffusion and osmosis
Cell Wall
- Plant cells have an additional rigid outer covering called the cell wall
- The cell wall lies outside the plasma membrane and is composed mainly of cellulose
- Cellulose provides structural strength to plants
- Cell walls allow plant cells to withstand changes in the surrounding medium without bursting
Nucleus
- The nucleus is a key component of the cell
- It was discovered by Robert Brown in 1831
- The nucleus is responsible for controlling the cell's activities and functions
Cell Division
- Cells divide to produce new cells of their own kind
- All cells come from pre-existing cells
- This process is essential for the growth and development of living organisms
Osmosis
- Osmosis is the movement of water across a selectively permeable membrane
- It occurs when there is a difference in concentration of water or solute between the cell and its environment
- Osmosis can cause cells to swell or shrink depending on the concentration of the surrounding solution
- It is an important process for the exchange of water and nutrients between cells and their environment
Importance of Diffusion
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Diffusion is the movement of substances from a region of high concentration to a region of low concentration
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It is an important process for the exchange of gases and water between cells and their environment
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Diffusion plays a crucial role in the life of a cell, enabling the exchange of essential nutrients and waste products### Cellular Structure and Function
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A cell can lose water through osmosis, leading to shrinkage or contraction of the cell contents away from the cell wall, a phenomenon known as plasmolysis.
Cellular Components
- The nucleus is a central part of a cell, containing chromosomes, which are made up of DNA and protein.
- Chromosomes contain genetic information necessary for constructing and organizing cells.
- The nuclear membrane has pores that allow the transfer of material between the nucleus and the cytoplasm.
Eukaryotic and Prokaryotic Cells
- Prokaryotic cells (e.g., bacteria) lack a nuclear membrane, while eukaryotic cells (e.g., plants and animals) have a defined nuclear region.
- Prokaryotic cells are generally smaller than eukaryotic cells.
- Eukaryotic cells have more complex organelles and a true nucleus.
Cell Membrane and Cytoplasm
- The cell membrane is a selective barrier that separates the cell from its environment.
- The cytoplasm is the fluid content inside the cell membrane, containing many specialized organelles.
- The cytoplasm plays a crucial role in maintaining cellular functions.
Cell Organelles
- Endoplasmic Reticulum (ER):
- A network of membrane-bound tubes and sheets.
- RER has ribosomes attached to its surface, involved in protein synthesis.
- SER is involved in lipid synthesis and detoxification.
- Golgi Apparatus:
- A system of membrane-bound vesicles, involved in protein modification and packaging.
- Functions include storage, modification, and packaging of products.
- Lysosomes:
- Membrane-bound sacs containing digestive enzymes.
- Involved in cellular digestion and waste removal.
- Also known as "suicide bags" because they can digest their own cell components.
- Mitochondria:
- Known as the powerhouses of the cell.
- Generate ATP through cellular respiration.
- Have their own DNA and ribosomes.
- Plastids:
- Present only in plant cells.
- Types include chromoplasts (colored) and leucoplasts (white or colorless).
- Chloroplasts contain chlorophyll and are involved in photosynthesis.
- Vacuoles:
- Membrane-bound sacs involved in storage and digestion.
- In plant cells, vacuoles are filled with cell sap and provide turgidity and rigidity.
Cell Division
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New cells are formed in organisms for growth, replacement, and reproduction.
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Cell division is a fundamental process of life.### Cell Division
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Cell division is the process by which new cells are made, and it has two main types: mitosis and meiosis.
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Mitosis is the process of cell division that results in two identical daughter cells, each with the same number of chromosomes as the mother cell.
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Mitosis is responsible for growth and repair of tissues in organisms.
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Meiosis is a different process of cell division that involves two consecutive divisions, resulting in four new cells with half the number of chromosomes as the mother cell.
Cell Structure
- The cell is the fundamental organisational unit of life.
- Cells are enclosed by a plasma membrane composed of lipids and proteins.
- The cell membrane is an active part of the cell, regulating the movement of materials between the cell and the outer environment.
- In plant cells, a cell wall composed mainly of cellulose is located outside the cell membrane.
- The cell wall enables cells to exist in hypotonic media without bursting.
- The nucleus in eukaryotes is separated from the cytoplasm by a double-layered membrane and directs the life processes of the cell.
- The ER functions as a passageway for intracellular transport and as a manufacturing surface.
- The Golgi apparatus consists of stacks of membrane-bound vesicles that function in the storage, modification, and packaging of substances manufactured in the cell.
- Plant cells have large membranous organelles called plastids, which are of two types: chromoplasts and leucoplasts.
- Chromoplasts contain chlorophyll and perform photosynthesis, while leucoplasts function in storage.
- Most mature plant cells have a large central vacuole that helps maintain the turgidity of the cell and stores important substances, including wastes.
Cell Types
- Prokaryotic cells have no membrane-bound organelles, their chromosomes are composed of only nucleic acid, and they have only very small ribosomes as organelles.
- Eukaryotic cells have membrane-bound organelles and chromosomes composed of nucleic acid and proteins.
Cellular Functions
- Cells in organisms divide for growth, replacement of dead cells, and formation of gametes for reproduction.
- The plasma membrane is necessary for the survival of the cell, and if it ruptures or breaks down, the cell will die.
- The Golgi apparatus is essential for the storage, modification, and packaging of substances manufactured in the cell.
- The mitochondria is known as the powerhouse of the cell because it generates energy for the cell through cellular respiration.
- Lipids and proteins constituting the cell membrane are synthesized in the ER.
- Amoeba obtains its food through a process called phagocytosis.
- Osmosis is the movement of water molecules from a high concentration to a low concentration through a selectively permeable membrane.
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Description
Explore the basics of life sciences, including the discovery of cells and their structures, as observed by Robert Hooke in a cork slice.
