Cell Theory PDF

22/08/2024 King Charles II of England in commissioned a...

22/08/2024 King Charles II of England in commissioned a microscopic investigation of the natural world, during that time the focus of the interest was on insect anatomy. Robert Hooke’s Compound Boxes in the thin Micrographia Microscope slices of Cork He is an English Botanist. He examined thin slices of cork from the bark of an oak tree with his compound microscope. He discovered boxes and called it cellulae 1  22/08/2024 He was the first biologist to discover the following: He is a Dutch Naturalist. Made over microscopes With his microscopes, he observed what he called “ANIMALCULES” – known today as protozoa (1674) and Bacteria Protozoa Nematodes Rotifers bacteria He was the first biologist to discover the following: Spermatozoa of both Insects and Other insects and humans Microorganisms 2  22/08/2024 He is a Scottish Botanist. He is a German Botanist. He successfully discovered the Co-founder with Theodor Schwann center of a cell in of the Cell Theory He referred such structure as nucleus He studied microscopic plant structures and observed different parts of the plant are composed of cells He is a German Physiologist. He is a German Pathologist. Founded modern histology by He pioneered the modern concept of defining cell as the basic unit of pathological processes by his animal structure application of the cell theory. He accepted the idea that the origin of cells was the division of pre-existing cells 3  22/08/2024 a biologist who was credited for helping an American biologist who with the discovery of cell membrane in revolutionized the endosymbiotic theory which states that modern-day mitochondria and chloroplasts are according to her, the cell membrane is a descendants of ancient bacteria-like physical biological membrane, not an organisms that lived inside prokaryotic interface between two different liquids. cells two billion years ago when Earth was still hot and mostly barren. Historic scientific theory that is universally accepted. It is comprised of three principles or postulates. 4 22/08/2024 5  22/08/2024 6 22/08/2024 7  22/08/2024 Hairlike structure that acts primarily as an organelle of locomotion in the cells of many living organisms Flagella is made of a globular Have a complex structure protein called flagellin that creates a consisting of microtubules and an rigid, hollow cylinder and uses the associated complex of motor and movement of hydrogen ions across connective proteins. the membrane Glycocalyx is a highly charged layer of membrane-bound biological Prokaryotic cells produce macromolecules attached to a cell glycocalyx coatings, such membrane. This layer functions as a as capsules and slime barrier between a cell and its surroundings. layers, that aid in attachment to surfaces Most glycocalyx-associated proteins and/or evasion of the host are transmembranes that can be immune system. linked to the cytoskeleton. Present in cells that lack cell walls. 8  22/08/2024 Every cell in the human body – endothelial cells, immune cells, muscle cells, blood cells, neurons, and all the others – exhibits a glycocalyx. 9  22/08/2024 the gelatinous liquid that fills the inside of a cell. It is composed of water, salts, and various organic molecules. Prokaryotic plasma membrane generally lacks sterols No cytoskeleton and no cytoplasmic streaming In Eukaryotic plasma membrane, Sterols and Cytoskeleton is present; cytoplasmic carbohydrates are streaming occur present and serves as receptor. Chromosomes are threadlike structures of nucleic acids and proteins found in living cells, carrying genetic information in the form of genes. 10  22/08/2024 An organism duplicates its genetic Mitosis is a process where a single cell material, or deoxyribonucleic acid divides into two identical daughter cells. Bacterial conjugation is a process A type of cell division in sexually (DNA), and then divides into two parts During mitosis, one cell divides once to of genetic transfer between reproducing organisms that reduces (cytokinesis), with each new organism form two identical cells. bacterial that requires direct the number of chromosomes in receiving one copy of DNA. contact in between cells gametes PROKARYOTIC EUKARYOTIC 0.1 – 5.0 MICROMETERS Size 10 – 100 MICROMETERS NO NUCLEUS (NUCLEOID) Nucleus HAS TRUE NUCLEUS NO MEMBRANE-BOUND ORGANELLES Organelles WITH MEMBRANE-BOUND ORGANELLES GLOBULAR PROTEIN (FLAGELLIN) Flagella MICROTUBULES & CONNECTIVE PROTEINS GENERALLY PRESENT Glycocalyx PRESENT IN CELLS WITHOUT CELL WALL CHEMICALLY COMPLEX (PEPTIDOGLYCAN) Cell Wall CHEMICALLY SIMPLE (CELLULOSE) NO STEROLS Plasma Membrane STEROLS FOR SUPPORT AND TRANSPORT NO CYTOSKELETON, NSTREAMING Cytoplasm WITH CYTOSKELETON AND STREAMING 70S Ribosomes 80S IN AREA CALLED NUCLEOID Chromosomes INSIDE NUCLEUS BINARY FISSION Division MITOSIS CONJUGATION Reproduction MEIOSIS 11  22/08/2024 Present in all organisms including plants. Controls both solute and solvent entry and exit between the cell and the environment. Can be semi-permeable, impermeable, permeable, and selectively permeable in nature. 12  22/08/2024 Protecting the integrity of the interior cell. Providing support and maintaining the shape of the cell. Helps in regulating cell growth through the balance of endocytosis and exocytosis. Plays an important role in cell signaling and communication. Selectively permeable membrane by allowing the entry of only selected substances into the cell. The main functions of the cell wall are: The cell wall is present only in plants, fungi and bacteria. Protecting the cell against physical damage and invading pathogens. The cell wall is the outermost covering of plant cells. Controls and regulates the direction of cell growth. It is present outside the cell membrane and is tough, flexible, and sometimes Providing the strength, structural rigid in its texture. support and maintaining the shape of the cell. (PLANTS) It is mainly composed of cellulose, long fibers of carbohydrates Functions as a storage unit by storing including hemicellulose, lignin, and carbohydrates for use in plant pectin. growth, especially in seeds. 13  22/08/2024 The nucleus is responsible for regulating almost all forms of cellular activities. A nucleus is a double-membraned eukaryotic cell organelle containing the genetic material. Considered as the central unit of a cell. The organelle responsible for controlling cellular activities like metabolism and division. 14  22/08/2024 15  22/08/2024 16  22/08/2024 17  22/08/2024 18  22/08/2024 Hierarchy of Biological Organization EPITHELIUM CONNECTIVE 1. Cuboidal Epithelium 1. Loose 2. Dense 3. Specialized 2.1 Dense 2. Simple Columnar 1.1 Areolar 3.1 Cartilage Regular 2.2 Dense 3. Simple Squamous 1.2. Adipose 3.2 Bone Irregular 2.3 Dense 4. Stratified Squamous 1.3. Reticular 3.3 Blood Elastic 5. Pseudostratified Columnar 19  22/08/2024 They are closely joined cells with tight junctions. It lines the outer surfaces of organs Tight junctions serve as barriers for pathogens Mechanical injuries, and blood vessels throughout the and fluid loss. body. It is also found in the inner surfaces of cavities in many internal organs. DISTINCT ARRANGEMENT OF EPITHELIAL TISSUE 1. CUBOIDAL An epithelial tissue comprised of cuboidal EPITHELIUM epithelial cells, and is involved in secretory, absorptive, or excretory functions The cell comprising the cuboidal epithelium is approximately as wide as it is tall. It is therefore cube-like (thus, the name). Cuboidal epithelia can be found lining the collecting ducts of the kidney, the pancreas, the salivary gland, the sweat glands, and the mammary glands. 20  22/08/2024 DISTINCT ARRANGEMENT OF EPITHELIAL TISSUE CUBOIDAL EPITHELIUM 2. SIMPLE For secretion and active absorption COLUMNAR Consist of a single layer of cells that are taller than they are wide Secretion of Glandular Products --------- Salivary Glands Synthesis and Packaging -------------------- Pancreas Ion and Fluid Regulation -------------------- Mammary Glands This type of epithelium lines the Barrier Function ---------------------------------- Lining of the Small Intestine small intestine and stomach where it Protection ------------------------------------------- Respiratory Tract absorbs nutrients from the lumen of Hormone Release ------------------------------- Thyroid Gland the intestine DISTINCT ARRANGEMENT OF EPITHELIAL TISSUE 3. SIMPLE Characterized by being flat, possessing SQUAMOUS an oblong nucleus, and having a scale- Absorption and Secretion like appearance. The cells are wider Protection than they are tall and appear somewhat hexagonal when viewed from above. Movement Secretion of Glandular Products Protection Against Chemicals Plate – like cells Selective Permeability For exchange of material through diffusion 21  22/08/2024 DISTINCT ARRANGEMENT OF EPITHELIAL TISSUE STRATIFIED SQUAMOUS STRATIFIED Stratified squamous epithelium is a type SQUAMOUS of tissue consisting of multiple layers of flat, scale-like cells. 1.Multiple Cell Layers The main role of stratified squamous epithelium is to provide protection 2.Keratinization against mechanical and chemical 3.Tight Cell Junctions stresses, as well as to minimize water 4.Rapid Cell Replacement loss. 5.Protection Against Chemicals It serves as a protective barrier in areas subjected to wear and tear DISTINCT ARRANGEMENT OF EPITHELIAL TISSUE CONNECTIVE TISSUES Appears stratified but is actually a single layer CONNECTS, SUPPORTS AND PSEUDOSTRATIFIED of cells of varying heights. This gives the false BINDS. COLUMNAR impression of multiple cell layers. Commonly found in the respiratory tract, Provide support, connect, and where it is ciliated to move mucus and trapped anchor different structures in the particles out of the airways, aiding in respiratory defense mechanisms. body. This includes supporting organs, connecting bones, and Functions to protect underlying tissues and even insulating body parts. secrete mucus, such as in the trachea and bronchi of the respiratory system. Separate other tissue or organs. 22  22/08/2024 THREE MAIN GROUPS OF CONNECTIVE TISSUES 1.1 AREOLAR CONNECTIVE TISSUE It is found surrounding blood 1. Loose (Areolar) 2. Dense Connective 3. Specialized vessels, nerve bundles, muscles, Connective Tissue Tissue Connective Tissue and organs. It fills the spaces between organs and connects the skin to the underlying muscle. Contains a network of blood vessels that facilitate the exchange of nutrients, gases, and waste products between the bloodstream and surrounding cells. 1.2 ADIPOSE TISSUE It is composed of adipocytes or “fat cells” It stores energy in the form of fat and provide cushions and insulates the body. It also plays a role in regulating body temperature 23  22/08/2024 1.3 RETICULAR TISSUE 2. DENSE CONNECTIVE TISSUE It is a type of connective tissue with fibers as its main matrix element. It is present in locations with Reticular Fibers high cellular content. Dense Regular Dense Dense Elastic Connective Tissue Irregular Connective Connective Tissue Tissue It has a branched and mesh- like pattern called reticulum. It provides structural support. 2.1 Dense Regular Connective Tissue 2.2 Dense Irregular Connective Tissue It is made up of type 1 collagen fibers. Collagen fibers are The fibers are not arranged in parallel bundles. densely packed together and arranged in parallel to each other. It is found in deep layer of the dermis and sclera in eye. It is found in areas of the body where large amount of tensile It provides strength and support to tissues and organs subjected to tension strength are required such as and stretching from multiple directions, ligaments, tendons and such as the dermis of the skin and the aponeurosis. capsules surrounding organs. 24  22/08/2024 2.3 DENSE ELASTIC TISSUE 3. SPECIALIZED CONNECTIVE TISSUE It is made up of a series of similar cells put together to perform a specific function. It provides tissues with elastic recoil and resilience. Cartilage Bone Blood/Vascular It is found throughout the body but most abundant in the reticular tissues of soft organs or organs that require stretching as it function. It is necessary for the proper structure and function of various systems. 3.1 CARTILAGE 3.2 BONE TISSUE MATRIX Has a firmly gelated A hard tissue that has a consistency that endows this honeycomb-like matrix internally tissue with unusual rigidity and which helps to give the bone resistance to compression. rigidity. Functions involve: It provides support, facilitation of Support / Flexible Support movement, protection of internal Shock Absorption organs, storage of minerals and Growth and Development fat, metabolic regulation, and hematopoiesis. CHONDROCYTES LACUNAE 25  22/08/2024 3.3 BLOOD primarily responsible for generating It is a connective tissue that has a mechanical force and facilitating movement. fluid matrix called plasma. characterized by its contractility, excitability, extensibility, and elasticity. Vital connective tissue that plays a central role in transporting classified into Smooth, Cardiac, and Skeletal substances, defending against Muscle cells (fibers) can be multinucleated infections, maintaining (skeletal), single-nucleated (smooth), or have homeostasis, and supporting one or two nuclei (cardiac), reflecting their various physiological processes structural diversity. throughout the body. An involuntary muscle that contracts slowly and automatically. Smooth muscle fibers or myocytes, have a distinctive elongated and tapered appearance. Each smooth muscle cell usually contains a single, NUCLEUS centrally located nucleus. Have the ability to contract spontaneously without external nerve stimulation. Smooth muscle is found in the walls of various internal organs and structures, including the digestive tract, blood vessels, respiratory airways, urinary tract, and reproductive organs. 26  22/08/2024 It is a specialized and organized type of tissue exist only in the heart. Intercalated discs in cardiac muscle are like communication bridges. They help heart muscle cells (cardiomyocytes) work together to pump blood effectively. It is responsible for heart pumping and blood circulation. NUCLEUS Cardiac muscle cell typically contains one or two centrally-located nuclei. Have a branched, striated appearance and are interconnected by intercalated discs Long, multinucleated, and exhibit a striated appearance It is responsible for the control of the body and With cells among the largest cells in the human the communication among its parts through body, with some reaching several centimeters in electrical signals. length. They are under voluntary control and are It consist of neurons and supporting cells called responsible for the voluntary movements of the neuroglia. body, including actions like walking, running, and lifting objects. Connected to bones by tendons, which are Nervous cells and tissues are distributed strong, fibrous connective tissues. throughout the human body to facilitate various functions, including sensory perception, motor Capable of rapid and forceful contractions, control, and regulation of bodily processes. making them well-suited for activities that require strength and speed. 27  22/08/2024 DENDRITES - branch-like structures that receive messages from other neurons and allow the transmission of messages MYELIN SHEATH serves as an insulating to the cell body. and accelerating structure that enhances the speed and efficiency of nerve impulse transmission along AXON is a tube-like structure that axons carries electrical impulse from the cell body to the axon terminals that pass the impulse to another neuron. AXON TERMINALS - send messages from one neuron to another or to a muscle or gland by releasing chemical CELL BODY - Contains Golgi body, messengers called neurotransmitters. endoplasmic reticulum, mitochondria and other components. non-neuronal cells that provide support and non-neuronal cells that provide support and protection to neurons. protection to neurons. ASTROCYTES - support the structural MICROGLIA - immune cells and metabolic needs of neurons. that protect against pathogens. OLIGODENDROCYTES - form the myelin sheath around axons in the central GLIAL CELL nervous system. GLIAL CELL EPENDYMAL CELLS - line the SCWANN CELLS - which form the myelin fluid-filled cavities in the brain sheath in the peripheral nervous and spinal cord. system. 28  11/09/2024 Events: During the G1 phase, the cell Series of events grows in size, carries out its It involves the from the time a normal functions, and distribution of cell is first formed prepares for DNA identical genetic replication. from a dividing material or DNA to parent cell until its two daughter cells Purpose: to ensure the cell is ready own division for DNA synthesis and subsequent cell division. Duration: 1  11/09/2024 Events: The cell continues to grow, synthesizes proteins, and Events: DNA replication takes place. prepares for cell division. It The cell's entire genome is also checks for DNA duplicated, resulting in the replication errors and formation of two complete monitors the cell's overall sets of chromosomes, readiness for division. Purpose: To accurately duplicate the Purpose: Serves as a checkpoint to genetic material to ensure ensure that DNA that both daughter cells replication has occurred receive identical copies correctly and that the cell is during cell division. in optimal condition for mitosis or meiosis. Duration: Duration: Events: The actual cell division phase. Some cells, after completing the G1 In mitosis, the cell division phase, may enter a non-dividing takes place in body cells. In state called the G0 phase. Cells in G0 meiosis, cell division happens are temporarily or permanently in germ cells. withdrawn from the cell cycle. Purpose: To distribute the duplicated Lack of essential nutrients or growth genetic material and cellular factors. organelles into daughter cells, ensuring their proper When subjected to stress or formation. damage, enter G0 temporarily until conditions become favorable for cell Duration: division again. 2  11/09/2024 G1 Interphase G2 M Phase Purpose: The G1 checkpoint verifies if the Purpose: The G2 checkpoint confirms that cell is ready for DNA synthesis (S DNA replication in the S phase phase) and subsequent division. has occurred accurately and that the cell is ready for mitosis or Events Checked: It assesses factors such as meiosis. cell size, nutrient availability, DNA Events Checked: It monitors DNA integrity damage, and growth and verifies if all DNA factor signals. has been replicated without errors. Outcome: If conditions are favorable and the cell is prepared, it proceeds Outcome: If the cell meets these criteria, it to the S phase; otherwise, it proceeds to M phase (mitosis or may enter G0 phase or undergo meiosis); otherwise, it may DNA repair. pause for repair or enter apoptosis (cell death). 3  11/09/2024 Purpose: The M checkpoint ensures that all chromosomes are correctly aligned on the spindle apparatus before cell division. Events Checked: It monitors the attachment The S phase is not considered a of spindle fibers to the checkpoint because its main job is centromeres of sister to duplicate the cell's DNA. While chromatids. it's a critical step in the cell cycle, its Outcome: If chromosomes are properly purpose is not to check or verify aligned, cell division proceeds; if whether the cell is ready for Spindle Fiber not, the checkpoint delays division, like the G1, G2, and M division until the issue is Centromere resolved to prevent unequal checkpoints do. distribution of genetic material. If a cell does not properly regulate its division and continues dividing without control, it can lead to a condition known as uncontrolled or excessive cell proliferation. CANCER TISSUE DAMAGE LOSS OF ORGAN GENETIC FUNCTION INSTABILITY 4  11/09/2024 A process of cell division in which a single cell divides into two genetically identical daughter cells, each with the same number of chromosomes as the parent cell. It is a nuclear division in which the nucleus divides to produce two nuclei. Occurs in body cells or somatic cells. Chromatin in Interphase Chromatin Condensation: During prophase, the long, thin strands of chromatin in the nucleus condense and coil into visible, compact structures Centriole called chromosomes. Nuclear Envelope Breakdown: The nuclear envelope, which surrounds the nucleus, begins to disintegrate in prophase. Formation of Spindle Fibers: Microtubules, known as spindle fibers, Spindle Chromosome Fiber begin to assemble as centrioles move to opposite sides of the cell. 5  11/09/2024 Chromosome Alignment: Chromosome Separation: The condensed chromosomes align at the cell's The sister chromatids, which are the two identical equatorial plane, known as the metaphase plate. copies of each chromosome held together at the centromere, are pulled apart towards opposite ends Spindle Fiber Attachment: of the cell. Microtubules of the spindle apparatus attach to the centromeres of each chromosome. These attachments, known as kinetochores, help to secure the Microtubule Shortening: chromosomes in their aligned position. Microtubules that make up the spindle apparatus actively shorten, which is facilitated by motor Checkpoint Control: proteins. The cell checks at this stage to ensure that all chromosomes are properly aligned at the metaphase Cytokinesis Initiation: plate and attached to spindle fibers before Anaphase marks the near completion of mitosis, and proceeding to the next stage, anaphase. it often overlaps with the initiation of cytokinesis, Chromatid De-condensation: Cleavage Furrow Formation: The separated sister chromatids begin to de- In animal cells, cytokinesis involves the formation condense. They revert to their less condensed of a cleavage furrow, which is a contractile ring chromatin state, making them less visible under composed of actin filaments. a microscope. Difference from Telophase: Nuclear Envelopes Reformation: Specifically concerned with the physical division The nuclear envelope, which had disintegrated of the cell into two distinct daughter cells. during prophase, starts to re-form around the separated chromatids in telophase. Completion of Cell Division: Cytokinesis represents the final stage of cell Cytokinesis Continues: division, ensuring that the genetic material and The cell undergoes final preparations for cellular components are distributed evenly dividing into two separate daughter cells, each between the daughter cells, with its own nucleus, as cytokinesis continues. 6  11/09/2024 Cell Growth and Repair: Genetic Stability: Mitosis is essential for the growth and Mitosis ensures the genetic stability of development of multicellular an organism by distributing a complete organisms. It allows an organism to and identical set of chromosomes to increase its cell number, which is crucial each daughter cell. for overall growth. Immune Response: Mitosis plays a role in the immune Embryonic Development: response. Certain immune cells, such as During embryonic development, mitosis lymphocytes, undergo mitosis to is responsible for the rapid cell division produce a larger population of that forms the early embryo. identical cells when responding to infections or other immune challenges. 7  11/09/2024 Nuclear envelope Chromosomes are Shortening of the Two identical disintegrates to being aligned in Nuclear envelope spindle fibers daughter cells allow later the mitotic plate as reforms and two allows Sister undergo G1 and attachment of spindle fibers nuclei are now chromatids to be will continue with spindle fibers to attach to the created. pulled away from the cell cycle. the NOW visible centromeres. each other. chromosomes Meiosis is a specialized cell division process that occurs in sexually reproducing organisms, forming haploid gametes (sperm and egg cells) from diploid parent cells. 8  11/09/2024 Aims to reduce the chromosome number by half, ensuring that offspring inherit a unique combination of genetic material from each parent and contributing to genetic variation within a population. Reductional Division: Meiosis I is often referred to as the "reductional division" because it results in the reduction of the chromosome number by half Homologous Chromosome Separation: Meiosis I separates homologous chromosome pairs, with one member of each pair ending up in each of the two daughter cells. 9  11/09/2024 Chromosome Condensation: Chromatin condenses into visible chromosomes, each consisting of two sister chromatids. Homologous Chromosome Pairing: Marked by the pairing of homologous chromosomes through a process called synapsis. Nuclear Envelope Breakdown and Formation of Spindle Fiber: The nuclear envelope begins to break down, allowing the attachment of the spindle fiber formed. A process during Prophase I of meiosis, where homologous chromosomes exchange genetic material. This occurs at specific points called chiasmata or chiasma, where the chromatids of homologous chromosomes physically overlap. Chromosome Alignment: Paired homologous chromosomes align During this process: along the metaphase plate. Non-sister chromatids break at corresponding points. These broken segments are then swapped between the chromatids. The exchanged segments reconnect, resulting in new combinations of Spindle Fiber Attachment: genes. Spindle fibers from opposite cell poles attach to the centromeres of the homologous chromosomes. 10  11/09/2024 The way the homologous pairs align is independent of how other pairs align. This means each pair's orientation is random, allowing different Homologous Chromosome Separation: Anaphase I is marked by the separation of combinations of maternal and paternal chromosomes homologous chromosome pairs. Each to be passed on to the daughter cells. member of the homologous pair is pulled toward opposite poles of the cell. Reduction in Chromosome Number: The chromosome number is halved. This reduction is a key feature of meiosis. Nuclear Envelopes Reform: Nuclear envelopes start to reassemble around the separated sets of chromosomes Haploid cells are formed. at the opposite poles of the cell. The cells are genetically nuclei are formed each containing half of different. the starting number of chromosomes. 11  11/09/2024 Chromosome Condensation: Sister Chromatid Separation: The chromosomes condense once Meiosis II is characterized by the separation again as the nuclear envelope of sister chromatids. breaks down. Four Haploid Daughter Cells: Meiosis II concludes with the formation of four haploid daughter cells, each containing Formation of Spindle Fibers: a unique combination of genetic material. The spindle apparatus re-forms in prophase II. Chromosome Alignment: Individual chromosomes align along the metaphase plate. Sister Chromatid Separation: Anaphase II of meiosis involves the Spindle Fiber Attachment: separation of sister chromatids, which Spindle fibers attach to the centromeres of were held together by centromeres in individual chromosomes in metaphase II. metaphase II. Chromatids are pulled towards Haploid Cell Formation: opposite poles of the cell. It ensures that the resulting daughter cells will be haploid, containing half the original chromosome number. 12  11/09/2024 Resulting in Four Haploid Daughter Cells: In meiosis II, cytokinesis occurs after the separation of sister chromatids. As a result, each initial haploid cell undergoing Nuclear Envelopes Reform: meiosis II divides into two, yielding a total of four haploid During telophase II of meiosis, daughter cells, each with a unique combination of genetic nuclear envelopes begin to material. reassemble around the separated sets of chromosomes at the opposite poles of the cell. 13 11/09/2024 14  11/09/2024 Events: During the G1 phase, the cell Series of events grows in size, carries out its It involves the from the time a normal functions, and distribution of cell is first formed prepares for DNA identical genetic replication. from a dividing material or DNA to parent cell until its two daughter cells Purpose: to ensure the cell is ready own division for DNA synthesis and subsequent cell division. Duration: 1  11/09/2024 Events: The cell continues to grow, synthesizes proteins, and Events: DNA replication takes place. prepares for cell division. It The cell's entire genome is also checks for DNA duplicated, resulting in the replication errors and formation of two complete monitors the cell's overall sets of chromosomes, readiness for division. Purpose: To accurately duplicate the Purpose: Serves as a checkpoint to genetic material to ensure ensure that DNA that both daughter cells replication has occurred receive identical copies correctly and that the cell is during cell division. in optimal condition for mitosis or meiosis. Duration: Duration: Events: The actual cell division phase. Some cells, after completing the G1 In mitosis, the cell division phase, may enter a non-dividing takes place in body cells. In state called the G0 phase. Cells in G0 meiosis, cell division happens are temporarily or permanently in germ cells. withdrawn from the cell cycle. Purpose: To distribute the duplicated Lack of essential nutrients or growth genetic material and cellular factors. organelles into daughter cells, ensuring their proper When subjected to stress or formation. damage, enter G0 temporarily until conditions become favorable for cell Duration: division again. 2  11/09/2024 G1 Interphase G2 M Phase Purpose: The G1 checkpoint verifies if the Purpose: The G2 checkpoint confirms that cell is ready for DNA synthesis (S DNA replication in the S phase phase) and subsequent division. has occurred accurately and that the cell is ready for mitosis or Events Checked: It assesses factors such as meiosis. cell size, nutrient availability, DNA Events Checked: It monitors DNA integrity damage, and growth and verifies if all DNA factor signals. has been replicated without errors. Outcome: If conditions are favorable and the cell is prepared, it proceeds Outcome: If the cell meets these criteria, it to the S phase; otherwise, it proceeds to M phase (mitosis or may enter G0 phase or undergo meiosis); otherwise, it may DNA repair. pause for repair or enter apoptosis (cell death). 3  11/09/2024 Purpose: The M checkpoint ensures that all chromosomes are correctly aligned on the spindle apparatus before cell division. Events Checked: It monitors the attachment The S phase is not considered a of spindle fibers to the checkpoint because its main job is centromeres of sister to duplicate the cell's DNA. While chromatids. it's a critical step in the cell cycle, its Outcome: If chromosomes are properly purpose is not to check or verify aligned, cell division proceeds; if whether the cell is ready for Spindle Fiber not, the checkpoint delays division, like the G1, G2, and M division until the issue is Centromere resolved to prevent unequal checkpoints do. distribution of genetic material. If a cell does not properly regulate its division and continues dividing without control, it can lead to a condition known as uncontrolled or excessive cell proliferation. CANCER TISSUE DAMAGE LOSS OF ORGAN GENETIC FUNCTION INSTABILITY 4  11/09/2024 A process of cell division in which a single cell divides into two genetically identical daughter cells, each with the same number of chromosomes as the parent cell. It is a nuclear division in which the nucleus divides to produce two nuclei. Occurs in body cells or somatic cells. Chromatin in Interphase Chromatin Condensation: During prophase, the long, thin strands of chromatin in the nucleus condense and coil into visible, compact structures Centriole called chromosomes. Nuclear Envelope Breakdown: The nuclear envelope, which surrounds the nucleus, begins to disintegrate in prophase. Formation of Spindle Fibers: Microtubules, known as spindle fibers, Spindle Chromosome Fiber begin to assemble as centrioles move to opposite sides of the cell. 5  11/09/2024 Chromosome Alignment: Chromosome Separation: The condensed chromosomes align at the cell's The sister chromatids, which are the two identical equatorial plane, known as the metaphase plate. copies of each chromosome held together at the centromere, are pulled apart towards opposite ends Spindle Fiber Attachment: of the cell. Microtubules of the spindle apparatus attach to the centromeres of each chromosome. These attachments, known as kinetochores, help to secure the Microtubule Shortening: chromosomes in their aligned position. Microtubules that make up the spindle apparatus actively shorten, which is facilitated by motor Checkpoint Control: proteins. The cell checks at this stage to ensure that all chromosomes are properly aligned at the metaphase Cytokinesis Initiation: plate and attached to spindle fibers before Anaphase marks the near completion of mitosis, and proceeding to the next stage, anaphase. it often overlaps with the initiation of cytokinesis, Chromatid De-condensation: Cleavage Furrow Formation: The separated sister chromatids begin to de- In animal cells, cytokinesis involves the formation condense. They revert to their less condensed of a cleavage furrow, which is a contractile ring chromatin state, making them less visible under composed of actin filaments. a microscope. Difference from Telophase: Nuclear Envelopes Reformation: Specifically concerned with the physical division The nuclear envelope, which had disintegrated of the cell into two distinct daughter cells. during prophase, starts to re-form around the separated chromatids in telophase. Completion of Cell Division: Cytokinesis represents the final stage of cell Cytokinesis Continues: division, ensuring that the genetic material and The cell undergoes final preparations for cellular components are distributed evenly dividing into two separate daughter cells, each between the daughter cells, with its own nucleus, as cytokinesis continues. 6  11/09/2024 Cell Growth and Repair: Genetic Stability: Mitosis is essential for the growth and Mitosis ensures the genetic stability of development of multicellular an organism by distributing a complete organisms. It allows an organism to and identical set of chromosomes to increase its cell number, which is crucial each daughter cell. for overall growth. Immune Response: Mitosis plays a role in the immune Embryonic Development: response. Certain immune cells, such as During embryonic development, mitosis lymphocytes, undergo mitosis to is responsible for the rapid cell division produce a larger population of that forms the early embryo. identical cells when responding to infections or other immune challenges. 7  11/09/2024 Nuclear envelope Chromosomes are Shortening of the Two identical disintegrates to being aligned in Nuclear envelope spindle fibers daughter cells allow later the mitotic plate as reforms and two allows Sister undergo G1 and attachment of spindle fibers nuclei are now chromatids to be will continue with spindle fibers to attach to the created. pulled away from the cell cycle. the NOW visible centromeres. each other. chromosomes Meiosis is a specialized cell division process that occurs in sexually reproducing organisms, forming haploid gametes (sperm and egg cells) from diploid parent cells. 8  11/09/2024 Aims to reduce the chromosome number by half, ensuring that offspring inherit a unique combination of genetic material from each parent and contributing to genetic variation within a population. Reductional Division: Meiosis I is often referred to as the "reductional division" because it results in the reduction of the chromosome number by half Homologous Chromosome Separation: Meiosis I separates homologous chromosome pairs, with one member of each pair ending up in each of the two daughter cells. 9  11/09/2024 Chromosome Condensation: Chromatin condenses into visible chromosomes, each consisting of two sister chromatids. Homologous Chromosome Pairing: Marked by the pairing of homologous chromosomes through a process called synapsis. Nuclear Envelope Breakdown and Formation of Spindle Fiber: The nuclear envelope begins to break down, allowing the attachment of the spindle fiber formed. A process during Prophase I of meiosis, where homologous chromosomes exchange genetic material. This occurs at specific points called chiasmata or chiasma, where the chromatids of homologous chromosomes physically overlap. Chromosome Alignment: Paired homologous chromosomes align During this process: along the metaphase plate. Non-sister chromatids break at corresponding points. These broken segments are then swapped between the chromatids. The exchanged segments reconnect, resulting in new combinations of Spindle Fiber Attachment: genes. Spindle fibers from opposite cell poles attach to the centromeres of the homologous chromosomes. 10  11/09/2024 The way the homologous pairs align is independent of how other pairs align. This means each pair's orientation is random, allowing different Homologous Chromosome Separation: Anaphase I is marked by the separation of combinations of maternal and paternal chromosomes homologous chromosome pairs. Each to be passed on to the daughter cells. member of the homologous pair is pulled toward opposite poles of the cell. Reduction in Chromosome Number: The chromosome number is halved. This reduction is a key feature of meiosis. Nuclear Envelopes Reform: Nuclear envelopes start to reassemble around the separated sets of chromosomes Haploid cells are formed. at the opposite poles of the cell. The cells are genetically nuclei are formed each containing half of different. the starting number of chromosomes. 11  11/09/2024 Chromosome Condensation: Sister Chromatid Separation: The chromosomes condense once Meiosis II is characterized by the separation again as the nuclear envelope of sister chromatids. breaks down. Four Haploid Daughter Cells: Meiosis II concludes with the formation of four haploid daughter cells, each containing Formation of Spindle Fibers: a unique combination of genetic material. The spindle apparatus re-forms in prophase II. Chromosome Alignment: Individual chromosomes align along the metaphase plate. Sister Chromatid Separation: Anaphase II of meiosis involves the Spindle Fiber Attachment: separation of sister chromatids, which Spindle fibers attach to the centromeres of were held together by centromeres in individual chromosomes in metaphase II. metaphase II. Chromatids are pulled towards Haploid Cell Formation: opposite poles of the cell. It ensures that the resulting daughter cells will be haploid, containing half the original chromosome number. 12  11/09/2024 Resulting in Four Haploid Daughter Cells: In meiosis II, cytokinesis occurs after the separation of sister chromatids. As a result, each initial haploid cell undergoing Nuclear Envelopes Reform: meiosis II divides into two, yielding a total of four haploid During telophase II of meiosis, daughter cells, each with a unique combination of genetic nuclear envelopes begin to material. reassemble around the separated sets of chromosomes at the opposite poles of the cell. 13 11/09/2024 14  High Concentration (Outside of Cell) Movement of molecules from an area of high concentration to an area of low concentration. Diffusion relies on the random motion of molecules and does not Low Concentration (Inside of Cell) require energy input from the cell. It is a critical process for the exchange of gases, nutrients, and waste products within cells and between cells and their environment.  High Concentration (Outside of Cell) In the cell, examples of molecules that can use simple diffusion to travel in and out of the cell membrane are: Water Oxygen Carbon dioxide Low Concentration (Inside of Cell) Ethanol Urea They pass directly through the cell membrane without energy along the concentration gradient. The diffusion of water molecules across the cell membrane. The movement of water molecules across a semipermeable cell membrane from an area of lower solute concentration to an area of higher solute concentration. It plays a crucial role in maintaining cell hydration and regulating osmotic pressure. The diffusion of water molecules across the cell membrane. The movement of water molecules across a semipermeable cell membrane from an area of lower solute concentration to an area of higher solute concentration. It plays a crucial role in maintaining cell hydration and regulating osmotic pressure. the capability of a solution to modify the volume of cells by altering their water content Process that involves the movement of specific molecules across the cell membrane with the assistance of transport proteins. It is used for the transport of larger molecules that cannot easily pass through the lipid bilayer of the cell membrane. Maintains the selective permeability of the cell membrane, allowing the controlled movement of specific molecules. Protein Channels facilitate Undergoing conformational rapid transport, and their changes to transport the selectivity is primarily based bound molecule to the on size. other side. Peter Agre won the 2003 Nobel Prize in Chemistry for his 1992 discovery of aquaporin proteins  Osmosis Peter Agre won the 2003 Nobel Prize in Chemistry for his 1992 discovery of aquaporin proteins Requires the expenditure of energy to move ions or molecules. Enabling cells to perform functions like nerve signaling, muscle contraction, and nutrient uptake. Involves specialized membrane proteins, such as pumps and transporters, which actively transport specific substances across the cell membrane.