Introduction to cell

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some key points about animal cells:

• Animal cells are eukaryotic cells, meaning they have a nucleus and organelles bounded by membranes. The complex internal structure of animal cells allows them to carry out specialized functions.
• The nucleus contains DNA and controls the cell's activities. It is the information center of the cell. The nucleus is enveloped by a nuclear membrane with nuclear pores that regulate the transfer of materials.
• Mitochondria are the powerhouses of the cell. They produce energy for the cell through cellular respiration. Mitochondria have their own DNA and reproduce independently within cells.
• The endoplasmic reticulum (ER) helps in transport, protein synthesis, and lipid synthesis. There are two types:
1. Rough ER: Has ribosomes attached to its surface. It synthesizes proteins and transports them.
2. Smooth ER: Lacks ribosomes. It synthesizes lipids, metabolizes carbohydrates, and stores calcium.
• The Golgi apparatus packages and modifies proteins from the ER and secretes them out of the cell. It is associated with the production of lysosomes.
• Lysosomes contain digestive enzymes that break down waste materials, foreign particles, and cellular debris. They are involved in cellular nutrition and removing unwanted cells.
• Ribosomes bind with mRNA to synthesize proteins based on the genetic instructions. They can be found freely floating in the cytoplasm or attached to the rough ER.
• Cytoskeleton provides structure and shape to the cell. It is made up of microtubules and actin filaments which enable cell movement, division, and intracellular transport.
• Vesicles and vacuoles store and transport materials within the cell. They are involved in endocytosis, exocytosis, waste removal, and more.
• Centrosomes organize microtubules during animal cell division and contain two centrioles.
• Cell membrane is the outer boundary that regulates the transport of materials in and out of the cell. It is made of a phospholipid bilayer with embedded proteins.
• Various animal cells have specialized structures based on their function. For example, nerve cells have dendrites and axons, muscle cells have contractile fibers, etc.

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• The cell is the basic structural and functional unit of all living organisms. Cells are microscopic and typically range from 1 to 100 micrometers in size.
• The cell theory states that:
1. All living things are composed of cells.
2. Cells are the basic units of structure and function in living things.
3. New cells are produced from existing cells.
• The cell consists of various components, including:
• Nucleus: Contains DNA and controls cell activity. Present in eukaryotic cells only.
• Cytoplasm: Gel-like substance that contains all the cell components. Made up of 80% water.
• Organelles: Membrane-bound compartments that carry out functions like energy production, protein synthesis, and transport. Examples are mitochondria, endoplasmic reticulum, golgi apparatus, etc.
• Proteins: Essential macromolecules for structure, signaling, growth, differentiation, and all cell functions.
• Other components: Include carbohydrates, lipids, RNA, ribosomes, vesicles, cytoskeleton, etc.
• Based on complexity, cells are classified into prokaryotic and eukaryotic cells:
• Prokaryotic cells: Have no nucleus or membrane-bound organelles. Bacteria and archaea have prokaryotic cells.
• Eukaryotic cells: Have a nucleus and organelles. All multicellular organisms have eukaryotic cells.
• Some important functions of cells include:
• Growth and division: Cells grow and divide to produce new cells. This allows growth, maintenance, and asexual reproduction.
• Energy production: Cells harvest energy from nutrients through cellular respiration and metabolism.
• Transport of molecules: Movement of molecules between the cell and its environment and within the cell.
• Synthesis of new molecules: Cells synthesize proteins, lipids, carbohydrates, and nucleic acids for growth, structure, signaling, and storage.
• Response to environment: Cells can detect signals from the external and internal environment and respond appropriately.
• Differentiation: Stem cells differentiate into specialized cells with specific structures and functions.
• Apoptosis: Programmed cell death which is essential for controlling cell number and removing damaged or infected cells.

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Transcript:-
The cell is a structural and functional unit of life, bounded by the living outer boundary called the cell membrane, plasma lema, or plasma membrane. The cell contains a nucleus, which acts as the controlling center of the cellular factory. The protoplasm found between the plasma membrane and the nuclear membrane is called the cytoplasm.

The cytoplasm contains many organelles such as endoplasmic retic. Ribosomes cents, GOGI complex mitochondria, micro bodies, lysosomes, et cetera. Which take part in carrying out the life functions of the cell, thus a cell as a sort of chemical factory has its own controlling center, communicating systems, transport systems, manufacturing centers, powerhouses, et cetera. The cell is bound by the living outer boundary called the plasma membrane. The major chemical constituents of the plasma membrane are proteins, lipids, and carbohydrates. According to the unit membrane model of Robertson, the plasma membrane consists of two layers of molecules, each about 20 angstroms thick.

Were the central layer of about 35 angstroms forming a total thickness of 75 Angstrom. According to the fluid mosaic model of Singer and Nicholson, there is a double layer of lipid molecules phospholipids with GLO protein molecules and steroids, which are arranged differently in different parts of the plasma membrane.

The plasma membrane is selectively permeable and regulates the flow of materials in and out of the cell. The vital functions of the plasma membrane are protection and. Passive and active transport of molecules, phagocytosis, or cell eating and pinocytosis cell drinking

cell membranes essentially consist of lipoproteins, which are special, non bonded combinations of lipids with proteins. Cell membrane proteins are grouped as structural proteins and carrier proteins. Structural proteins form the backbone of the cell membrane with little catalytic activity and lipophilic nature.

Structural proteins fall into two main categories, intrinsic or integral proteins, an extrinsic or peripheral protein. Carrier proteins or permease transport substances across the membrane against the concentration gradient. The protoplasm found between the plasma membrane and the nuclear membrane is called cytoplasm.

Cytoplasm contains many characteristic structures called organelles, which take part in carrying out functions of the. The outer part of the cytoplasm without granules is called ectoplasm, and the inner part with granules is called endo Plasm. The endo plasm contains organelles and non-living materials called astic particles.

The major cell organelles are the nucleus mitochondria, endoplasmic reticulum, ribosomes, gogi, complex centrosomes with centrioles, microtubules, and micro fila. The cell matrix in the cytoplasm is composed of cytoskeleton, which is made up of microtubules and micro filaments. The endoplasmic reticulum er, or agata plasm is constituted by a network of double membranes distributed throughout the cytoplasm, extending from the nucleus to the margins of the.

The double membranes enclosed spaces, which constitute the vacu system for the movement of materials, the ER is found to exist in three forms, namely, sys, lam, vesicles, and tubules. Two types of ER are recognized based on the nature of the surface of the er, namely granular er and a granular. The granular ER or rough surfaced ER has particles called ribosomes or ribo nucleoprotein particles, r n P on the surface, while the A granular ER smooth surfaced ER is without R nps, the major functions of the ER include transport of synthetic products of the cell, providing mechanical support to the matrix of the cell, intracellular transmission of impulse.

Synthesis of lipids, cholesterol, and steroid hormones, and reconstitution of the nuclear membrane. During teleph phase of mitosis, ribosomes occur in association with the membrane, a system of the er. These are often called protein factories of the cell. They are asymmetrical particles with a sedimentation rate of ats s equals berg.

Which in turn is composed of a large 60 s subunit and a small 40 s subunit. The a s ribosomes also form clusters called polyribosomes or polysome during protein biosynthesis. Ribosomes are composed of about 60% proteins and 40% RNA and contain enzymes necessary for protein synthes. GGI Complex appears to have been derived from elements of ER because of the similarity between the two.

GGI complex is composed of three structural components, namely the flattened sax or cyst E, small vesicles and vacuoles. The flattened sacks or cyst are double membrane of sax or lammie arranged in bundles. The small vesicles are found in groups close to cyst, and the large vacuoles are formed from flattened sacks.

The GGI bodies are mainly responsible for storage and processing of proteins and enzymes synthesized in the er.

These proteins are further transported to their destinations, such as the plasma membrane via the transport vesicles.

The goji body also contributes to the formation of acrosome in the mature sperm, which enclose enzymes to facilitate fertilization. Mitochondria are the powerhouse of the cellular factory, which produce energy-rich. A T P molecules mitochondria are generally granular or filamentous in shape measuring three to four microns in length and 0.5 to one micron in diameter.

Each mitochondrion is surrounded by a double membrane envelope. The inner membrane is provided with a series of unfoldings called Christ. Which penetrate the matrix of mitochondrion. The inner surface of the inner membrane and Christi are provided with small particles called elementary particles or F1 particles, which are functionally associated with the enzymes of electron transport system e t s and oxidative phosphorylation.

The matrix is granular and contains a number of enzymes and co enzyme. The final respiratory pathways taking place in mitochondria include Kreb cycle or TCA cycle, or citric acid cycle electron transport system E T S and oxidative phosphorylation

A T P molecules are formed in mitochondria as a result of oxidative phosphoryl. Lysosomes are small particles present in the cytoplasm and range from 0.4 to 0.8 microns in diameter. Lysosomes are usually spherical in shape, but may be irregular in some cells. They are covered by a single membrane of lipoprotein molecules and exhibit polymorphism existing in four types.

Name. Primary lysosomes, secondary lysosomes, or digestive vacuoles, autophagic, vacuoles, or auto fgo, lysosomes, and residual bodies. Lysosomes contain a number of hydrolyzing enzymes with autolytic properties. These hydrolytic enzymes bring about intracellular digestion by pinocytosis cell drinking and phagocytosis cell eating, and are thus called the suicide squads of the cellular factory.

The centrosome is the organelle located near the nucleus in the cytoplasm. The centrosome contains 2 cents, which are cylindrical bodies and lie at right angles to each. Each cylindrical or barrel like centri is about 3000 to 5,000 angstroms in diameter, surrounded by a dense wall composed of nine triplets of microtubules, where each triplet is composed of three microtubules.

The cental is composed of RNA traces of d n a and glycoproteins. The cents duplicate at the end of the phase of mit. And these two pairs of cents establish the cell centers or cell poles surrounded by astral rays cents as a part of the centrosome play. A significant role in cellular organization, especially in organizing the microtubules in the cytoplasm and the special arrangement of the cell.

The position of the nucleus is also determined by the position of the centri. During Spermiogenesis, the distal centri gives rise to the axial filament of the mature sperm. Microtubules are hollow cylinders of protein, several microns long and about 200 to 250 angstroms in diameter, bounded by a wall around 60 angstroms thick with 13 subunits of the protein assembled around the.

Microtubules are composed of a heterodimer protein called tubulin, ranging from 110,000 to 120,000. Daltons tubulin is composed of two different monomers tubulin alpha and tubulin beta cytoplasmic microtubules, forming the spindle fibers a uniform in size and generally disappear when treated with conine.

Microtubules perform several functions. The mitotic spindle, which is composed of bundles of microtubules, plays an important role in the pole ward movement of chromosomes in dividing cells. Microtubules also function as a micro circulatory system, transporting molecules, granules, and vesicles within the.

Micro bodies are membrane bound, vesicles found in the cytoplasm 0.2 to 1.2 microns in diameter. These are bounded by a typical trilaminar unit membrane, which is six to eight nanometers in thickness. Micro bodies are of two types, namely peroxisomes and Gly. Oxys. Peroxisomes play an important role in hydrogen peroxide metabolism.

And Gly Oxys contain enzymes for fatty acid metabolism. Micro filaments or microfibers appear as thread like aggregates of protein molecules measuring 40 to 70 angstroms in diameter in the cytoplasm of the cell. A microfilament is a single strand of identical globular proteins, which are very similar to the actin of muscle.

Nerve cells possess micro filaments called neuro filaments, which have a diameter of about 100 angstroms and travel along the length of most accents. Micro filaments are involved in movements associated with thorough formation in cell division, smooth muscle contraction and cell migration during embryonic develop.

Cytoplasm contains vacuoles, which are fluid filled spaces enclosed by a membrane called Toop plast. In human cells, vacuoles are small or may be absent. The vacuoles contain water, inorganic salts, and various organic materials. These help in the transport of substances, in and out of the. The nucleus is the controlling and coordinating center of the cellular factory.

This usually occupies about one-tenth of the volume of the cell. The nucleus of the cell, which is not undergoing cell division, is called interface nucleus. The nucleus is enveloped by the porous nucl membrane and the fluid substance present in the nucleus is called Caro lymph or nucleoplasm. The nucleus encloses a spherical body called nucleolus.

Inside the interface nucleus is a thread like network called chromatin, which form chromosomes during the cell division. The chromatin mainly consists of D N A deoxyribonucleic acid. The hereditary material, the nuclear membrane, is a double membrane structure with pores or openings at interval. Each membrane is 90 angstroms thick, and the space between the two membranes is called the perle space, 100 to 300 angstroms wide.

Each nuclear pore or opening is about 200 to 400 angstroms in diameter. The nuclear membrane is connected with the membranes of ER at many places. So the space between inner and outer nuclear membranes is directly connected with the lumen of endoplasmic reticulum. The nuclear membrane acts as a barrier that separates the contents of the nucleus from the cytoplasm, as well as allowing the passage of materials between the nucleus and the cytoplasm.

The NCLs is a spherical body found within the nucleus, and it contains proteins and rna. The NCLs is comprised of four components, particulate component, fibrillar component, amorphous part, and chromatin part. The particulate component or the granular part, is constituted of rib bone. Nucleo protein particles are nps, which are 150 to 200 angstroms in diameter.

The fibrillar part is composed of fibrils, which are 50 to 150 angstroms in diameter. The particulate and fibrillar components together constitute the ncl Anema. The amorphous part is rich in proteins and may be composed of closely packed fis and granules. The chromatin part is composed of the network of chromatin, which contains abundant d n A.

The NCLs plays a vital role in protein synthesis by producing r n. This NCL RNA is a precursor for the formation of ribosomal rna. The NCLs disappears at the end of pro phase and reappears at the end of Teleph phase of cell division. Chromatin appears as a network of thread like material in the interface nucleus, which condenses into chromosomes during cell division.

Chromatin exhibiting, differential thickening or hetero hypnosis during certain stages of the cell cycle is called heterochromatin, while the remaining, which does not show hetero hypnosis is called U chromatin. The heterochromatin is generally associated with canto core or centra, the nucle organizer and telomeres or chromosomal end.

The uc chromatin accounts for the bulk of the chromosome, which shows normal chromosomal coiling, isop Posis chromosomes are nuclear components which appear as rods with two longitudinal functional subunits termed chromatins chromosomes in condensed metaphase and antiphase stages. Stages appear as being composed of chromatins, chromo, mater, kto cor constrictions, and satellite bodies.

Chromosomes of somatic cells occur in pairs called homologous chromosomes, which exhibit characteristic behavior during myosis. A pair of chromosomes associated with the determination of sex is called sex chromosomes or alisos, and the rest of the chromosomes unknown as autosomes. For example, in humans, two n equals 46.

Equals 44 autosomes plus Twosomes X, Y in male and x, X in female. The major chemical components of the metaphysic chromosomes are dna, n, rna, and proteins. Chromosomes play an important role in variation, heredity mutation, and evolution. They are hence considered the principle vehicles of hereditary transmission.

DNA is the primary hereditary material found in almost all living systems. It mainly occurs in chromosomes, but traces of DNA N are also found in mitochondria and cents. D n is a macro molecule made up of a chain of nucleotides. A nucleotide is a fundamental unit of DNA and is composed of a nitrogenous base.

The Pento sugar and the phos. The nitrogenous bases of DNA N are adenine, a, guanine G, purine bases and thymine T and cytosine C. The pyrimidine bases. The pento sugar in d n A is the deoxy ribos type. The double helical model of DNA N was proposed by Watson and Crick and is built like a spiral staircase with the phosphate and sugar constituting the twisted frame of the stair.

And the nitrogenous base is forming the steps. The base pairs of the double helixes are joined by weak hydrogen bonds. Adenine pairs with thymine by two hydrogen bonds while guanine pairs with cytosine by three hydrogen bonds. RNA is another genetic material found in all living systems, its main function being directing protein Synthes.

RNA is also the primary hereditary material in some viruses. RNA is a macromolecule made up of a chain of nucleotides similar to dna, composed of nitrogenous bases, A G C and UIL U instead of thymine T pento. Sugar of the ribos type and phosphate RNAs are generally single standard. Exception being in a few viruses.

There are three types of RNA involved in protein synthesis, messenger, RNA or M RNA transfer, RNA or T RNA and ribosomal RNA or R rna. The M R N A carries the genetic information for the sequence of amino acids present in protein. T RNA functions by identifying and transporting the required amino acids to the ribosomes.

R RNA represents the catalytic part of ribosomes essential for the formation of the amino acid chain. Celia and Flagella are extensions of the cell surface. There is no definite morphological or physiological distinction between Celia and F Flagella. Although Celia are generally shorter and more numerous than flagella, the number of Celia varies from 300 to 14,000.

While the number of flagella may be one, two, or a few, the length of the cilium ranges from five to 10 microns outwards from the cell body compared to fledge el, which may be up to 150 micron. Each cilium or fle Elum arising from a basal granule is composed of a bundle of filaments that comprises of nine peripheral fibers and two central fibers, which together constitute the AEM or axial complex.

There are two types of Celia Motile cia, which beat constantly in a single direction, and the non-motor Celia, which typically serve as sensory organal. The motel Celia lining the trachea, the windpipe sweep away mucus and dirt from the respiratory passages. In females. The beating of Celia in the fallopian tube moves the ovum from the ovary to the uterus.

Ciliary defects and lack of functional Celia can cause chronic disorders such as polycystic kidney disorders, P K D, congenital heart disease, ectopic pregnancy, et cetera. Microvilli are tiny hair-like structures on the plasma membrane of epithelial cells, primarily involved in absorption and secretion.

Microvilli are about north point nor eight of a micron in diameter, and these tiny protrusions increase the surface area of the cell by about 600 fold in human, small intestinal cells. Thousands of microvilli former structure called the brush border that is found on the apical surface of epithelial cells and facilitate absorption and secretion.

For example, on the small intestinal enterocytes and the kidney proximal tubal microvilli also occur on sensory cells of the inner ear as stereocilia on the cells of taste buds and on olfactory receptor cells. The destruction of microvilli can lead to mal absorption of nutrients and persistent osmotic diarrhea, often accompanied by fever.

The cell cycle is an important process for growth, reproduction, and repair of damaged cells. A eukaryotic cell cycle is divided into three major phases, interface, mitosis and cytokinesis. The interface being the longest. During the interface, the cell prepares for cell division. The three phases of interface are G one or gap.

One phase where the cells synthesize cellular contents, excluding the genetic material, preparing the cell for division, the S or synthesis phase where the DNA replicates an G2 or GAP two. Where the cytoplasmic contents assemble to start the cell division during mitosis, the duplicated genetic material is equally distributed to the two daughter cells formed from the dividing cell.

The entire process of mitosis is divided into four stages, pro phase metaphase and teleph. The process of mitosis is followed by cytokinesis or division of the cytoplasm. Myosis is another form of cell division observed in eukaryotic cells,

particularly the gum eats myosis results in aloed cell, forming four haploid cells, and involves two successive nuclear division. Myosis one and Myosis two. Both the nuclear divisions have four stages. Prophase, metaphase, anaphase, and tele phase, followed by sat essis. Cells are the fundamental unit of life.

The organelles of cells, their detailed structure and functions, including endoplasmic, reticulum, mitochondria, gogi, complex genetic material, and the cell cycle revealed through breathtaking graphics enable the understanding of these basic units and increased knowledge of the complex organization of the human body.