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Questions and Answers
What is the primary function of lysosomes in a cell?
What is the primary function of lysosomes in a cell?
What is the main function of the mitochondria?
What is the main function of the mitochondria?
What is the name of the membrane surrounding a vacuole?
What is the name of the membrane surrounding a vacuole?
What is the role of chromoplasts?
What is the role of chromoplasts?
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Which organelle is responsible for protein synthesis?
Which organelle is responsible for protein synthesis?
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What is the function of leucoplasts?
What is the function of leucoplasts?
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Which of the following is NOT a function of ribosomes?
Which of the following is NOT a function of ribosomes?
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What is the term used to describe lysosomes?
What is the term used to describe lysosomes?
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Which organelle is exclusive to plant cells?
Which organelle is exclusive to plant cells?
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What is the function of the cristae in mitochondria?
What is the function of the cristae in mitochondria?
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Study Notes
Introduction to Cell
- Cells are the structural, functional, and biological units of all living beings.
- Cells are the building blocks of life and can replicate themselves independently.
- The entire functioning of living organisms begins from the basic unit called a cell.
Discoveries related to Cell
- Robert Hooke discovered and named the cell in 1665.
- Anton Van Leuwenhoek discovered protozoa and bacteria in 1674.
- Robert Brown discovered the cell nucleus in 1831.
- Schleiden and Schwann proposed the cell theory in 1838 and 1839.
- Purkinje discovered protoplasm in 1839.
Cell Theory
- All living organisms are composed of cells.
- Living organisms can be made up of one or more cells.
- New cells arise from pre-existing cells through the process of cell division.
Cell - different shape, size, and number
- Unicellular organisms are made up of a single cell (e.g., bacteria, protozoa).
- Multicellular organisms are made up of more than one cell (e.g., humans, animals).
- Cells come in different shapes, such as spherical, spindle, and branched and elongated.
- The smallest cell is Mycoplasma (bacteria), and the largest cell is an ostrich egg.
Cell Structure
- The cell consists of components such as the plasma membrane, cell wall, nucleus, cytoplasm, and cell organelles.
- The plasma membrane is the outermost covering of the cell and is selectively permeable.
- The cell wall provides structural strength and lies outside the plasma membrane in plant cells.
Cell Membrane
- The plasma membrane separates the cell contents from the external environment.
- It is selectively permeable, allowing certain materials to enter and exit the cell.
- The plasma membrane regulates the movement of substances in and out of the cell.
Transport Across Cell Membrane
- Passive transport involves the movement of substances from higher to lower concentration without energy.
- Active transport involves the movement of substances from lower to higher concentration with the help of energy in the form of ATP molecules.
- Osmosis is the passage of water molecules across a semi-permeable membrane from a solution with high concentration to a solution with low concentration.
- Types of osmosis include endosmosis (water enters the cell) and exosmosis (water leaves the cell).
- Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration.
Endocytosis & Exocytosis
- Endocytosis is the process of taking in substances through the cell membrane.
- Exocytosis is the process of releasing substances outside the cell through the cell membrane.
Cell Wall
- The cell wall is a non-living, rigid outer covering of plant cells composed mainly of cellulose.
- It provides structural strength and lies outside the plasma membrane.
- Plasmolysis occurs when plant cells lose water through osmosis, resulting in shrinkage of cell contents away from the cell wall.
Lysosomes
- Lysosomes are membrane-bound organelles that contain digestive enzymes.
- They digest foreign material and worn-out organelles to maintain cell cleanliness.
- Lysosomes break down complex substances into simpler ones using powerful enzymes.
- They are also known as "suicide bags" because they may burst during cellular disturbance, leading to self-digestion.
Mitochondria
- Mitochondria are the cell's powerhouses, generating energy in the form of ATP.
- They have two membranes: a porous outer membrane and a folded inner membrane.
- The inner membrane has cristae, which increase the surface area for ATP generation.
- Mitochondria possess their own DNA and ribosomes, enabling protein synthesis.
Plastids
- Plastids are exclusive to plant cells and exist in two varieties: chromoplasts and leucoplasts.
- Chromoplasts are colored plastids, such as chloroplasts, which contain chlorophyll and enable photosynthesis.
- Leucoplasts lack coloration and primarily function as storage sites for starch, oils, and protein granules.
Ribosomes
- Ribosomes are membrane-less cell organelles involved in protein synthesis.
- They are present in both prokaryotic and eukaryotic cells.
- Ribosomes help in the manufacture of protein molecules, enzymes, and hormones.
Vacuoles
- Vacuoles are storage sacs in cells, small in animals and large in plants.
- They are bound by a membrane called the tonoplast.
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Description
Learn about the fundamental unit of life, cell structure, cell division, and cell theory. Understand the importance of cells as the building blocks of life.
