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THE FUNDAMENTAL UNIT OF LIFE in 1 Shot | FULL Chapter Coverage (THEORY+PYQs) | Class-9th Biology

Physics Wallah Foundation・105 minutes read

All living organisms have bodies made up of cells, which are the fundamental unit of life and were discovered by Robert Hook in 1665. Different organs in the human body are composed of tissues made up of cells, and understanding the structure and function of cells is essential for comprehending the workings of different organs and organ systems.

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Cells, discovered by Robert Hook in 1665, are the fundamental unit of life and form the basis of all living organisms, including humans, by composing tissues that make up organs and organ systems.
The understanding of cell structure, including the nucleus, plasma membrane, and cytoplasm, is crucial for comprehending the functions of different organs and organ systems in the body.
The plasma membrane, a living and flexible structure composed of lipids and proteins, controls the entry and exit of substances into the cell through selective permeability, with active transport requiring energy and passive transport not.
Different types of cells, such as nerve cells and muscle cells, exhibit unique shapes and sizes, with variations in size and shape across bacteria, plant, and animal cells, emphasizing the diversity of cellular structures and functions.

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What is the fundamental unit of life?
Cells

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Summary

00:00

"Cells: Building Blocks of Life and Body"

Living organisms have a body structure made up of cells that perform various functions.
Cells are the fundamental unit of life, discovered by Robert Hook in 1665.
Different organs in the human body, such as the brain, heart, kidney, lungs, and pancreas, are made up of tissues composed of cells.
Tissues are groups of cells, and when different tissues come together, they form organs.
Organs working together form organ systems like the respiratory, digestive, circulatory, reproductive, nervous, muscular, and skeletal systems.
The discovery of cells led to the understanding that all living organisms, including humans, are made up of cells.
Robert Hook discovered dead cells, while Antony Van Leeuwenhoek discovered living cells in 1674.
Robert Brown discovered the nucleus inside cells in 1831, revealing a crucial internal structure.
Understanding the structure and function of cells is essential for comprehending the workings of different organs and organ systems in the body.
Cells are the building blocks of life, enabling various bodily functions and processes to occur.

15:08

Cell Biology Essentials: Protoplasm, Nucleus, Membrane

Protoplasmic term was introduced by Pakin ji to describe the living content of a cell, which includes the plasma membrane, cytoplasm, and nucleus.
The living parts of a cell collectively form the protoplasmic content, with the plasma membrane, cytoplasm, and nucleus being essential components.
In 1839, scientists Mathia Sliding and Thodaram extended the cell theory, emphasizing that all plants and animals are made up of cells.
Rudolph Virtue further expanded the cell theory by introducing the concept that new cells are formed when existing cells divide.
Cells can vary in shape, size, and number, with unicellular organisms having a single cell and multicellular organisms having multiple cells.
Different types of cells, such as nerve cells and muscle cells, exhibit distinct shapes and sizes within the human body.
The smallest known cell is Mycoplasma, while the largest living cell is the egg of an ostrich.
Cells can differ in size and shape, with bacteria, plant cells, and animal cells displaying a wide range of variations.
Understanding the basic components of a cell, including the nucleus, plasma membrane, and cytoplasm, is crucial for comprehending cell structure and function.
A flowchart detailing the components of a cell is a valuable tool for revision and understanding the fundamental elements of cell biology.

32:01

Cell Biology Basics for Children: Essential Concepts

Flowcharts and tables are essential for understanding basic concepts in biology, especially for children who may find them intimidating at first.
The structural and functional unit of life is the cell, which is the basic component of all living organisms.
The outer boundary of a cell is called the plasma membrane, which protects the components inside the cell.
The cell wall, present in plants, bacteria, and fungi, acts as an additional protective layer outside the plasma membrane.
The cell wall of plants is made of cellulose, while bacteria have a cell wall made of peptidoglycan, and fungi have a cell wall made of chitin.
The plasma membrane is a living and flexible structure made of lipids and proteins, with phospholipids being a key component.
Phospholipids are responsible for the structure of the plasma membrane, with Singer and Nicholson proposing the fluid mosaic model for its composition.
The nucleus is the control center of the cell, containing DNA and controlling the cell's functions.
Cytoplasm is a jelly-like substance inside the cell, filled with fluids and known as protoplasm, the living part of the cell.
Different cell organelles perform specialized functions within the cell, such as mitochondria generating energy and Golgi apparatus packaging proteins.

46:59

Plasma Membrane: Structure, Permeability, Transport, Osmosis

The Fluid Mosaic Model of the plasma membrane explains its complete structure, composed of specific lipids.
The plasma membrane is selectively permeable, allowing only specific substances to pass through.
The plasma membrane controls the entry and exit of substances, managing what goes in and out of the cell.
Two types of transportation across the plasma membrane are passive transport and active transport.
In passive transport, substances move from higher to lower concentration without the use of energy.
Active transport involves the movement of substances from lower to higher concentration, requiring the cell to spend energy.
Diffusion and osmosis are two types of passive transport, with diffusion involving the movement of substances from higher to lower concentration.
Osmosis specifically refers to the movement of water molecules from higher to lower concentration across a selectively permeable membrane.
Osmosis can be classified as endosmosis, where water moves into the cell, or exosmosis, where water moves out of the cell.
Understanding the processes of diffusion and osmosis is crucial for comprehending the movement of substances across the plasma membrane.

01:03:13

Cellular Osmosis and Transport Mechanisms Explained

Water is poured into a balloon, causing it to swell due to endosmosis occurring inside the cell.
Cells swell when water molecules move outwards.
Exosmosis removes water from a cell, causing it to shrink.
Hypertonic solutions have more solute and less solvent compared to cells, leading to cell shrinkage.
Hypotonic solutions have less solute and more solvent, causing cells to swell.
Isotonic solutions have equal solute concentrations inside and outside cells, resulting in no net movement of water molecules.
Cells shrink in hypertonic solutions and swell in hypotonic solutions.
A trick to remember the effects of hypertonic and hypotonic solutions: "Hyper has R and Shrink has R."
Active transport involves substances moving from lower to higher concentrations, requiring energy in the form of ATP.
Endocytosis involves substances being taken into cells through vesicles formed by the bending of the plasma membrane.

01:18:29

"Cell Processes: Endocytosis, Plasmolysis, Nucleus, DNA"

Amoeba acquires food through the process of endocytosis.
Endocytosis is the process by which amoeba acquires food.
Amoeba slowly destroys living cells by eating them.
Plasmolysis is observed in plant cells when placed in a hypertonic solution.
Plasmolysis results in the shrinking of the living content of the cell.
The cell wall does not shrink during plasmolysis as it is dead.
The nucleus is the control center of the cell and has a nuclear envelope with two membranes.
Nucleoplasm and DNA are found inside the nucleus, with DNA containing all genetic information.
DNA is a double-stranded thread-like structure, while RNA is single-stranded.
Chromosomes are formed when DNA coils and condenses during cell division.

01:34:10

Cell Structures and Functions in Biology

Ribosomes are cell structures responsible for making proteins and are found in both prokaryotic and eukaryotic cells.
Bacteria have thread-like structures called flagella that aid in movement.
Eukaryotic cells have a nucleus and are found in both plant and animal cells.
Plant cells have organelles like mitochondria, Golgi apparatus, lysosomes, and endoplasmic reticulum.
Bacteria cells have cytoplasm, plasma membrane, and a cell wall.
A common question in exams is to draw and label a diagram of a bacterial cell.
Eukaryotic cells have a nucleus and are categorized based on its presence.
Cell organelles have unique shapes and functions.
Endoplasmic reticulum (ER) has rough and smooth types, with ribosomes attached to the rough ER.
Golgi apparatus modifies, stores, and transports proteins and lipids within the cell.

01:50:02

Cell Organelles and Their Functions

Plastids are responsible for providing color inside the cell, with different types such as chromoplasts, leucoplasts, and chloroplasts.
Chromoplasts give colors other than green, such as red, pink, blue, and yellow, due to the pigment they contain.
Chloroplasts contain chlorophyll, the green pigment essential for photosynthesis, making them the site of photosynthesis in plant cells.
Leucoplasts are colorless plastids that store starch, fats, and proteins, performing different functions within the cell.
Ribosomes, without a membrane, act as protein factories in both prokaryotic and eukaryotic cells, aiding in protein synthesis.
Cell division results in the formation of new cells similar to the parent cell, a process known as mitosis or meiosis.
In mitosis, chromosome numbers remain the same, while in meiosis, they are halved, resulting in four daughter cells with half the chromosomes.
Mitosis is crucial for tissue repair, growth, and regeneration, while meiosis is involved in the formation of specialized cells like sperm and egg cells.
The tonoplast is the membrane of the vacuole, while lysosomes are formed from the Golgi apparatus and play a role in detoxification.
Prokaryotic cells lack defined nuclear regions and contain ribosomes, while eukaryotic cells have a nucleus and various cell organelles.

02:07:08

Cell Organelles and Their Functions

Digestive enzymes are found in lysosomes, which act as storage sacs in cells.
Photosynthesis occurs in chloroplasts, while the nucleus controls the entire cell.
Large vacuoles in plant cells store food and water, as plants cannot move to search for nutrients, unlike animals.

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