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CELL-THE UNIT OF LIFE in 1 Shot: FULL CHAPTER COVERAGE (Theory+PYQs) || Prachand NEET

YAKEEN・2 minutes read

Cells are fundamental units of life, explaining the structure and function using examples like bacteria and amoeba. Cell theory by Schleiden and Schwann solidifies the concept of all living organisms being composed of cells.

Insights

Cells are the basic structural and functional units of life, forming the foundation of all living organisms.
The study of cell biology, tracing back to scientists like Robert Hooke and Anton Van Leeuwenhoek, is crucial for understanding life processes.
The cell theory, proposed by Matthias Schleiden and Theodor Schwann, establishes that all living organisms are composed of cells.
Eukaryotic cells have a well-defined nucleus, cytoplasm, and membrane-bound organelles, distinguishing them from prokaryotic cells.
Cell membranes, primarily composed of proteins and lipids, play a vital role in stability, fluidity, and selective permeability.
Various cell shapes, sizes, and structures, such as those of RBCs, amoeba, and nerve cells, showcase the diversity and specialization within different cell types.

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What are cells considered in biology?
Cells are the basic units of life.

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Summary

00:00

The Essence of Cell Biology in Life

Dr. Vipan Kumar Sharma introduces a chapter on Cell, the Unit of Life, in a biology class.
The chapter delves into the structure and function of cells, essential for understanding biology.
Previous knowledge of topics like Living World, Biological Classification, and Plant Kingdom aids in comprehending cell biology.
Cells are the basic structural and functional units of life, crucial for the body's structure and functions.
The human body comprises trillions of cells, with over 200 different types contributing to various organs.
Cells are autonomous entities that can survive independently, forming the foundation of life.
Cellular organization is a defining feature of living organisms, with cells being the fundamental building blocks.
Organisms can be unicellular or multicellular, with examples like bacteria, amoeba, and yeast.
The study of cell biology traces back to scientists like Robert Hooke and Anton Van Leeuwenhoek, who observed cells' structures and functions.
Understanding cell biology is essential for grasping the intricacies of life processes and biological functions.

16:16

Discovery and Development of Cell Theory

Robert Hooke discovered the cell for the first time, observing cell walls and the nucleus in 1831.
Robert Brown identified the nucleus as a dense body within the cell, controlling its functions.
Anton Van Leeuwenhoek, known as the Father of Microbiology, observed live cells like protozoa and bacteria.
The development of electron microscopes between 1950 and 1960 allowed for detailed observations of cell structures like ribosomes and cell membranes.
The cell theory, proposed by Matthias Schleiden and Theodor Schwann, states that all living organisms are composed of cells.
Schleiden, a German botanist, discovered different types of cells in plants, leading to the understanding of plant tissues.
Schwann, a British zoologist, identified the plasma membrane in animal cells and the cell wall in plant cells.
The hypothesis that all living organisms are made up of cells was proven by Schleiden and Schwann through extensive research.
Rudolf Virchow finalized the cell theory by proposing that new cells arise from pre-existing cells, completing the explanation of cell formation.
The collaboration between Schleiden and Schwann solidified the cell theory, establishing the fundamental concept that all living organisms are composed of cells.

33:53

"Cell Theory: Expressing Biology's Serious Thoughts"

Rudolph Droco proposed a loving and sweet idea related to cell theory, emphasizing the importance of expressing serious thoughts in Biology.
The first proposal involves saying "kente jiam vyam Say fluidam" to convey deep thoughts, while the second involves saying "omni cell Lula he said cell e cellu" to signify the formation of new cells from old ones.
Slayton and Swann's statement that all organisms are made of cells contributed to the cell theory, which was further shaped by additional inputs.
The cell theory, also known as the cell line theory, asserts that new cells are formed from pre-existing cells, a concept explored in the cell cycle.
Exceptions to the cell theory include viruses, which do not follow the standard cell structure, unlike nucleated cells like RBCs.
Various cell shapes and properties are discussed, such as the disc shape of RBCs, irregular shapes of amoeba-like cells, and the columnar cell structure with a basal nucleus.
The nerve cell is highlighted for its length and branching, essential for transmitting signals effectively.
Different types of cells, like mesophyll cells with numerous chloroplasts, showcase the diversity in cell shapes and functions.
The largest cell, the ostrich egg, is compared to the longest cell, the nerve cell, emphasizing the difference between size and length.
Practical examples and comparisons, such as the size of bacteria and eukaryotic cells, highlight the unique characteristics and sizes of various cell types.

47:48

Cell Structure and Function in Brief

Bacteria size ranges from 3 to 5 micrometers, with rod-shaped, comma-shaped, spiral, and vibrio shapes.
Mycoplasma, a type of bacteria, is the smallest, with a length of 1 micron.
Ribosomes, the smallest cellular components, are around 15 to 20 nanometers in size.
Cytoplasm is the main arena for metabolic reactions in cells.
The cytoplasm in prokaryotic cells is fluid, while in eukaryotic cells, it is semi-fluid.
The nucleus, known as the brain of the cell, contains genetic material (DNA) packed into chromosomes.
Endoplasmic reticulum with ribosomes appears rough, while without ribosomes, it appears smooth.
Ribosomes are found in eukaryotic cells, mitochondria, and chloroplasts in plants.
Membrane-bound organelles are present in cells, distinguishing plant and animal cells.
Differences between plant and animal cells can be remembered using the four alphabets "ssss."

01:03:18

Plant and Animal Cell Structures and Functions

Cell wall is found in plants and is crucial for their structure and function.
Chloroplasts are essential for food production in plants and are absent in animal cells.
Central vacuoles in plant cells can occupy a significant volume, affecting cell size and structure.
Centrioles and centrosomes are absent in plant cells but present in animal cells, aiding in cell division.
Prokaryotic cells lack a well-defined nucleus and membrane-bound organelles, unlike eukaryotic cells.
Ribosomes are crucial for protein synthesis and are found in both prokaryotic and eukaryotic cells.
The presence of membrane-bound organelles is a key difference between prokaryotic and eukaryotic cells.
The cell is the fundamental unit of life, with cellular organization being a defining feature of living organisms.
Cell theory, formulated by Schleiden and Schwann, established that all organisms are composed of cells.
Eukaryotic cells have a well-defined nucleus, cytoplasm, and membrane-bound organelles, distinguishing them from prokaryotic cells.

01:19:24

"Cell Size and Structure in Bacteria"

Bacteria size ranges from 1 to 5 microns, with the largest being 1 to 2 microns.
Different cells have varying shapes and sizes, with nerve cells being the longest due to signal transmission.
Eukaryotic cells are typically 10 micrometers, while Mycoplasma is 3 micrometers.
Viruses are smaller than Mycoplasma, with some having lengths 15 times smaller.
Bacteria have a cell wall made of peptidoglycan, providing structure and shape.
Bacteria lack a nuclear envelope, with DNA lying naked in the nucleoid.
Plasmids in bacteria are circular DNA fragments that can replicate independently.
Plasmids can carry genes for antibiotic resistance, aiding in biotechnology.
Ribosomes in bacteria are associated with the plasma membrane, aiding in protein synthesis.
Bacteria lack membrane-bound organelles like the endoplasmic reticulum, relying on ribosomes for structure and function.

01:35:53

Plasma Membrane Folding and Cell Structures

Lamli Lamli refers to the folding of the plasma membrane in three ways.
The folding of the inner sides of the plasma membrane creates structures known as Mizo Som.
Mizo Som transforms into Hai Mijo Som, which is essential for correct folding and can lead to more foldings.
Bacteria with colorful pigments are found in these foldings, aiding in processes like photosynthesis.
Chromatophore is the term for the magnification of the membrane, containing colorful pigments.
Flexible membranes can extend and divide cells, while breaking the cell wall creates surface structures.
Motile bacteria can cause fruit burning, leading to the formation of metal cases.
The cell membrane's extension is known as a flange, crucial for eukaryotic and prokaryotic cells.
The eukaryotic flag is formed from microtubules, while prokaryotic cells rely on vesicles for secretion and endocytosis.
Inclusion bodies, such as gas vacuoles, are membrane-less organelles found in prokaryotic cells.

01:51:17

"Prokaryotic Cells: Essential Information and Functions"

Gas can evaporate, affecting the situation.
Sir Biasi provides a lot of information on blue-green and purple bacteria.
Prokaryotic cells contain blue-green algae and purple sulfur.
The NCRT contains essential information on prokaryotic cells.
Prokaryotic cells are smaller than eukaryotic cells, leading to faster division.
Shapes in biological classification include bacillus, diplococcus, and spirals.
Ribosomes are crucial organelles found in every cell.
Inclusion bodies in prokaryotic cells store phosphate, glycogen, and pigments.
The cell envelope in prokaryotes consists of three layers: plasma membrane, cell wall, and glycoconjugates.
The glyco calyx in prokaryotic cells acts as a protective coat against the immune system.

02:08:12

Cell Envelope and Ribosomes in Bacteria

Cell membrane is selectively permeable, interacting with the outside world.
The cell envelope has two modifications, including slime and capsule.
Slime protects bacteria from drying out, while the capsule provides protection.
Christian Gram introduced the gram staining technique based on cell envelope layers.
Gram-positive bacteria retain stains, appearing purple, while gram-negative bacteria do not retain stains.
Surface structures on bacteria include flagella, cell wall, filament, hook, and bezel body.
Small bridle-like structures on bacteria provide adhesion and attachment.
Prokaryotic ribosomes are universal organelles involved in protein synthesis.
Ribosomes consist of two subunits, with rRNA and proteins forming the main structure.
Ribosomes have different sizes, with odd numbers corresponding to 50S and even numbers to 30S, 60S, or 80S.

02:27:17

"Cell Structures and Functions in Biology"

The text discusses the concept of a test tube and a density gradient.
Gravity pulls heavier objects down more, leaving lighter objects on top.
When curd is strained, the lighter butter rises to the top.
Ribosomes of 40s and 60s units are discussed, with an unknown 8s unit.
The combination of ribosome units alters their density.
The concept of Svedberg units and sedimentation coefficients is explained.
Inclusion bodies in cells are discussed, representing reserve materials.
The differences between prokaryotic and eukaryotic cells are highlighted.
Cytoskeletal elements in eukaryotic cells provide structure and motion.
Microtubules, intermediate filaments, and microfilaments are key cytoskeletal elements.

02:43:58

Cell Membranes: Proteins, Lipids, and Cholesterol

The plasma membrane inside a cell is composed of proteins and lipids.
Cell membranes are mainly made of proteins and lipids, with variable compositions from cell to cell.
Red blood cells (RBCs) contain around 52% protein and 40% lipids, with no carbohydrates.
Cholesterol in cell membranes provides stability; its absence can lead to membrane issues.
Excessive intake of cholesterol or vitamins can lead to health problems.
Neurons are covered with myelin sheath, with varying lipid and protein content.
Proteins in cell membranes can be intrinsic (embedded in lipids) or extrinsic (partially embedded).
Phospholipids in cell membranes contain a polar head (hydrophilic) and non-polar tails (hydrophobic).
Carbohydrates associated with lipids are called glycolipids, while those with proteins are glycoproteins.
Cholesterol is only found in animal cells and plays a crucial role in membrane structure and stability.

03:02:08

Stabilizing Chair with Ballast Balls and Membrane Fluidity

To stabilize a destabilized chair, create ballast balls from paper and place them under the chair's feet.
The placement of the ballast balls is crucial for stabilizing the chair effectively.
Cholesterol acts as a membrane stabilizer, aiding in the fluidity and structural integrity of the lipid membrane.
Lateral movement within the lipid layer is possible due to the fluid nature of lipids.
Flip flop movement, where lipids jump from one layer to another, is rare but feasible.
Proteins within the membrane cannot perform flip flop movement due to structural constraints.
Neutral solutes, like water, can easily cross the membrane from high to low concentration.
Polar solutes face difficulty crossing the membrane due to the polar nature of the lipid layer.
Active transport requires energy to move substances against their concentration gradient.
The Fluid Mosaic Model of Plasma Membrane, proposed by Singer and Nicholson in 1972, describes the lipid as fluid and proteins as mosaic within the membrane structure.

03:18:40

Cell Wall Composition and Function in Cells

Osmosis is the diffusion of water.
Discrimination against animals is undesirable.
Polar substances cannot pass through non-polar membranes.
Facilitated diffusion requires carrier proteins.
Active transport involves pumps like the sodium-potassium pump.
Cell walls are found outside cell membranes.
Bacteria cell walls contain peptidoglycan.
Algae cell walls consist of cellulose, galactans, and minerals like calcium carbonate.
Higher plants have cellulose, hemicellulose, lactose, and pectin in their cell walls.
Cell walls provide shape, protection, and cell-to-cell interactions, with primary and secondary walls differing in flexibility and growth support.

03:36:09

"Cell Organelles: Functions and Interactions"

Endoplasmic reticulum is integral throughout the process, forming an endo membrane system.
Four organs are mentioned, including the nucleus, inner envelope, outer envelope, and endoplasmic reticulum.
The nucleus is created first, followed by the inner and outer envelopes.
Endoplasmic reticulum, specifically rough endoplasmic reticulum, contains ribosomes for protein synthesis.
Smooth endoplasmic reticulum is found at a distance from rough endoplasmic reticulum, involved in lipid synthesis.
Golgi apparatus, consisting of parallel sisters, undergoes forming and maturing phases.
Golgi apparatus tags and packages proteins and lipids, preparing them for secretion or storage.
Golgi apparatus is crucial for glycosylation, forming glycoproteins and glycolipids.
Lysosomes, formed from Golgi apparatus, contain hydrolytic enzymes for breaking down substances.
Vacuoles act as storage units, holding water, sugars, excretory materials, and pigments like anthocyanins.

03:53:05

Cell Organelles: Functions and Structures Explained

The Endoplasmic Reticulum (ER) consists of a luminal part and an extra luminal part, with the luminal part containing ribosomes forming the Rough ER (RE) responsible for protein synthesis, while the Smooth ER (SR) synthesizes lipids and steroids.
Golgi apparatus plays a crucial role in processing proteins and lipids, with proteins and lipids being made in the ER, then moving through the Golgi apparatus for packaging and modification before being sent to their respective destinations.
The central vacuole in plant cells, surrounded by a tonoplast membrane, serves as a storage organelle, maintaining up to 90% of the cell's volume, aiding in maintaining concentration gradients through active transport, and acting as a storage site for waste and nutrients.

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