Cell Theory Handout PDF

09/09/2023 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. 1 ...

09/09/2023 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. 1  09/09/2023 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. Robert Hooke’s Compound Boxes in the thin Micrographia Microscope slices of Cork 2  09/09/2023 He is a Dutch Naturalist. Made over microscopes With his microscopes, he observed what he called “ANIMALCULES” – known today as protozoa and bacteria He was the first biologist to discover the following: Bacteria Protozoa Nematodes Rotifers 3  09/09/2023 He was the first biologist to discover the following: Spermatozoa of both Insects and Other insects and humans Microorganisms 4  09/09/2023 He is a Scottish Botanist. He successfully discovered the center of a cell. He referred such structure as nucleus He is a German Botanist. Co-founder with Theodor Schwann of the Cell Theory He studied microscopic plant structures and observed different parts of the plant are composed of cells. 5  09/09/2023 He is a German Physiologist. Founded modern histology by defining cell as the basic unit of animal structure. He is a German Pathologist. He pioneered the modern concept of pathological processes by his application of the cell theory. He accepted the idea that the origin of cells was the division of pre-existing cells. 6  09/09/2023 a biologist who was credited for helping with the discovery of cell membrane in according to her, the cell membrane is a physical biological membrane, not an interface between two different liquids. an American biologist who revolutionized the endosymbiotic theory which states that modern-day mitochondria and chloroplasts are descendants of ancient bacteria-like organisms that lived inside prokaryotic cells during two billion years ago when Earth was still hot and mostly barren. 7  09/09/2023 Historic scientific theory that is universally accepted. It is comprised of three principles. But recently, parts of modern cell theory have been included. 8 09/09/2023 9 09/09/2023 10 09/09/2023 11  09/09/2023 Present in all organisms including plants. Controls both the entry and exit of both solute and solvent between the cell and the environment. Can be semi-permeable, impermeable, permeable, and selectively permeable in nature. The main functions of the plasma membrane or cell membrane include: 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. The cell membrane also plays an important role in cell signaling and communication. It acts as a selectively permeable membrane by allowing the entry of only selected substances into the cell. 12  09/09/2023 Are small cell organelles that are present in cells. Small, membrane-enclosed sacs that store and transport substances to and from one cell to another and from one part of a cell to another. Separated from the rest of the cytoplasm by at least one phospholipid bilayer. The membrane that encloses the vesicle is similar to the plasma membrane. Vesicles can fuse with the plasma membrane when they want to release their contents outside the boundaries of the cell. Peroxisomes are small organelles found in the cells of various organs and tissues throughout the body. They play a crucial role in several metabolic processes, including the breakdown of certain fatty acids and the detoxification of harmful substances, such as alcohol. The liver is the organ that contains a significant concentration of peroxisomes, and it is primarily responsible for the breakdown of alcohol (ethanol) in the body. Involved in the breakdown of long-chain fatty acids and the synthesis of specific phospholipids that are essential for the structure of cell membranes. 13  09/09/2023 Functions as a factory in which proteins received from the ER are further processed and sorted for transport to their eventual destinations: lysosomes, the plasma membrane, or secretion. In addition, as noted earlier, glycolipids and sphingomyelin are synthesized within the Golgi. In plant cells, the Golgi apparatus further serves as the site at which the complex polysaccharides of the cell wall are synthesized. The Golgi apparatus is thus involved in processing the broad range of cellular constituents that travel along the secretory pathway. The rough endoplasmic reticulum (rough ER) is a part of the endomembrane system of the cell and a subset of the endoplasmic reticulum (ER). The primarily concerned with the synthesis, folding, and modification of proteins, especially those that need to be delivered to different organelles within the cell, or secreted from the cell. The rough ER is also involved in the response of the cell to unfolded proteins and plays a role in the induction of apoptosis, due to its close interaction with mitochondria. The rough ER is characterized by the presence of membrane-bound ribosomes that give it a distinctive appearance under the microscope. 14  09/09/2023 Smooth ER is more tubular than rough ER and forms an interconnecting network sub-compartment of ER. It is not studded with ribosomes hence ‘smooth’ ER. Smooth ER is devoted almost exclusively to the manufacture of lipids and in some cases to the metabolism of them and associated products. In liver cells for example smooth ER enables glycogen that is stored as granules on the external surface of smooth ER to be broken down to glucose. Smooth ER is also involved in the production of steroid hormones in the adrenal cortex and endocrine glands. The nucleus is responsible for regulating almost all forms of cellular activities. Mostly, every type of cell that exists is categorized on the basis of the absence or presence of the nucleus within its cell (categorized either as a prokaryotic or eukaryotic cell.) 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 15  09/09/2023 A spherical structure found in the cell’s nucleus whose primary function is to produce and assemble the cell’s ribosomes. It is separate from the rest of the nucleus because of its specialized function. It does not contain chromosomes and is able to shuttle ribosomes and ribosomal RNAs out of the nucleus and into the cytoplasm where protein synthesis occurs. The nucleolus is considered as the brain of the nucleus, covering nearly 25% volume of the nucleus. synthesis of proteins and the production of ribosomes in eukaryotic cells. Fibrillar Centers: It is the place where the ribosomal proteins are formed. A ribosome is a complex molecular machine found inside the living cells that produces proteins from amino acids during a process called protein synthesis or translation. Ribosomes are specialized cell organelles and are found in both prokaryotic and eukaryotic cells. Every living cell requires ribosomes for the production of proteins. A ribosome is a complex of RNA and protein and is, therefore, known as a ribonucleoprotein. It is composed of two subunits – smaller and larger. It can be free floating in the Cytoplasm or attached to the Rough Endoplasmic Reticulum 16  09/09/2023 The POWERHOUSE of the CELL Mitochondria are membrane-bound cell organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell's biochemical reactions. Mitochondria contain their own small chromosomes. Generally, mitochondria, and therefore mitochondrial DNA, are inherited only from the mother. Generate large quantities of energy in the form of adenosine triphosphate (ATP). Its size ranges from 0.5 to 1.0 micrometer in diameter. The structure comprises an outer membrane, an inner membrane, and a gel-like material called the matrix. They are green-colored plastids, which comprise green-colored pigments within the plant cell and are called chlorophyll. Found in all green plants and algae. They are the food producers of plants. The size of the chloroplast usually varies between 4- 6 µm in diameter and 1-3 µm in thickness. They are double-membrane organelles with the presence of outer, inner, and intermembrane space. The most important function of the chloroplast is to synthesize food by the process of photosynthesis. Absorbs light energy and converts it into chemical energy. 17  09/09/2023 The cell wall is present only in plants, fungi and bacteria. The cell wall is the outermost covering of plant cells. It is present outside the cell membrane and is tough, flexible, and sometimes rigid in its texture. It is mainly composed of cellulose, long fibers of carbohydrates including hemicellulose, lignin and pectin. The main functions of the cell wall are: Protecting the cell against physical damage and invading pathogens. Controls and regulates the direction of cell growth. Providing the strength, structural support and maintaining the shape of the cell. Functions as a storage unit by storing carbohydrates for use in plant growth, especially in seeds. Membrane-bound organelles present in the cytoplasm and filled with a watery fluid containing various substances. They help in the storage and disposal of various substances. They can store food or other nutrients required by a cell to survive. They also store waste products and prevent the entire cell from contamination. The plant vacuoles occupy more than 80% of the volume of the cell. The vacuoles may be one or more in number. The vacuoles are completely filled with water and exert force on the cell wall. This is known as turgor pressure. It provides shape to the cell and helps it to withstand extreme conditions. 18  09/09/2023 19 09/09/2023 20 09/09/2023 21 09/09/2023 22  09/09/2023 Hairlike structure that acts primarily for locomotion in the cells of many living organisms 23  09/09/2023 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 macromolecules attached to a cell membrane. This layer functions as a barrier between a cell and its surroundings. Most glycocalyx-associated proteins are transmembranes that can be linked to the cytoskeleton. Present in cells that lack cell wall. 24  09/09/2023 Prokaryotic cells produce glycocalyx coatings, such as capsules and slime layers, that aid in attachment to surfaces and/or evasion of the host immune system. Every cell in the human body – endothelial cells, immune cells, muscle cells, blood cells, neurons, and all the others – exhibits a glycocalyx. 25 09/09/2023 26  09/09/2023 Prokaryotic plasma membrane generally lacks sterols In Eukaryotic plasma membrane, Sterols and carbohydrates are present and serves as receptor. 27  09/09/2023 the gelatinous liquid that fills the inside of a cell. It is composed of water, salts, and various organic molecules. No cytoskeleton and no cytoplasmic streaming Cytoskeleton is present; cytoplasmic streaming occur 28  09/09/2023 Chromosomes are threadlike structures of nucleic acids and proteins found in living cells, carrying genetic information in the form of genes. An organism duplicates its genetic Mitosis is a process where a single cell material, or deoxyribonucleic acid divides into two identical daughter cells. (DNA), and then divides into two parts During mitosis, one cell divides once to (cytokinesis), with each new organism form two identical cells. receiving one copy of DNA. 29  09/09/2023 Bacterial conjugation is a process A type of cell division in sexually of genetic transfer between reproducing organisms that reduces bacterial that requires direct the number of chromosomes in 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 30  09/09/2023 Typically smaller, Generally larger, ranging from 10 to 30 ranging from 10 to 100 micrometers (µm) in micrometers (µm) in diameter. diameter. The size is primarily due to the presence of a large vacuole, and cell wall. 31  09/09/2023 Because animal cells don't The defining feature of a plant have a rigid cell wall, they cell's shape is its rectangular have the flexibility to adopt or box-like appearance. This different shapes, So, depending shape is largely attributed to on where they are in the body the presence of a rigid and and what they're meant to do, thick cell wall that surrounds the cell membrane. The cell animal cells can look round, wall provides structural squiggly, stretched out, or even support and prevents the cell take on a shape similar to an from collapsing, giving the cell amoeba. This adaptability its distinct shape. helps them carry out their specific roles effectively within the complex world of our bodies.. Animals primarily store energy Plants store energy primarily in the form of glycogen, a in the form of starch, a complex carbohydrate, which complex carbohydrate, which is mainly found in the liver and is stored in various plant muscles. Glycogen serves as a tissues, including roots, stems, readily accessible energy and seeds. Starch serves as a long-term energy reserve, reserve that can be quickly providing plants with the converted into glucose to ability to store excess energy provide energy during periods produced through of increased demand, such as photosynthesis during periods physical activity or fasting. of abundant sunlight. Additionally, animals also store Additionally, plants can store energy in the form of adipose energy in the form of oils and tissue (body fat), which stores fats, particularly in seeds, excess energy from dietary which can be used as an sources and can be broken energy source during down to release energy when germination and early needed. growth. 32  09/09/2023 Among the 20 amino acids Plants are remarkable in their required for protein synthesis, capacity to synthesize all 20 animal cells have the inherent amino acids required for their capacity to synthesize only 10 biological functions. This of them through their own ability is a testament to their biochemical processes. These 10 sophisticated metabolic pathways and adaptation to amino acids are termed non- diverse environmental essential because animals can conditions. Amino acid produce them internally. synthesis is a crucial aspect of However, the remaining 10 plant biology, allowing plants amino acids are categorized as to thrive and contribute to the essential amino acids because broader ecosystem by serving they cannot be synthesized as a source of essential within animal cells and must be nutrients for herbivores and obtained from the diet. humans. In animal cells, the ability to Most plant cell types retain differentiate into various the ability to differentiate specialized cell types is a into various specialized cell defining characteristic of stem types throughout their life cells. Stem cells possess the cycle. This capacity for unique capability to differentiation is driven by the presence of totipotent transform into different cell or pluripotent cells, which types through a process can give rise to diverse cell called differentiation. This lineages, including root process allows stem cells to cells, leaf cells, and vascular give rise to specific cell tissue, contributing to the lineages, such as muscle cells, plant's growth and nerve cells, or blood cells, adaptability. depending on the signals and cues they receive from their microenvironment.. 33  09/09/2023 Animal cells typically do not Plant cells primarily increase increase in size primarily by in size by expanding their increasing in cell numbers. Instead, individual cell volumes, and a they grow by accumulating more key mechanism for this organelles, cytoplasm, and other expansion is the uptake of cellular components within the water into the central vacuole. As water enters the existing cell structure. This process, vacuole, it creates turgor known as cell growth, allows the pressure, which pushes the cell to increase in size and is cell membrane against the regulated by factors like nutrient rigid cell wall, causing the cell availability and growth signals. to swell and enlarge. While cell division can increase cell numbers, it is distinct from cell growth and occurs after a cell has reached a size threshold. Animal cells are characterized by Plant cells possess both a cell the absence of a rigid cell wall, wall made of cellulose and a which is a key structural feature cell membrane. The cell wall, that distinguishes them from plant primarily composed of cells. Instead, animal cells are cellulose, provides structural encased in a flexible cell support and shape to plant cells, serving as a protective membrane or plasma membrane outer layer. The cell that surrounds the cell's cytoplasm membrane is a lipid bilayer and organelles. This cell that surrounds the cell's membrane serves as a selectively cytoplasm and regulates the permeable barrier, regulating the passage of substances in and passage of substances in and out out of the cell, playing of the cell and playing a crucial essential roles in nutrient role in maintaining cell shape and transport, waste removal, and integrity. cellular communication.. 34  09/09/2023 Animal cells possess centrioles, Plant cells typically lack which are cylindrical structures centrioles, which are crucial for organizing microtubule cylindrical structures found in assembly during cell division. animal cells. Unlike animal Centrioles are located in a region cells, plant cells do not rely on called the centrosome and play a centrioles for microtubule organization during cell pivotal role in orchestrating the division. Instead, plant cells formation of the mitotic spindle, a use a different mechanism structure essential for separating involving microtubule- chromosomes during mitosis and organizing centers (MTOCs) ensuring accurate cell division. that are not structured like This organized microtubule centrioles but serve a similar arrangement, facilitated by purpose in coordinating the centrioles, enables animal cells to formation of the mitotic undergo proper cell division and spindle and ensuring proper maintain genomic stability. chromosome segregation during cell division. Cilia, flagella, and pseudopodia are specialized structures used by animal cells for locomotion. Cilia are short, numerous hair-like protrusions found on the cell Plant cells do not typically surface. Flagella, on the other possess specialized structures hand, are longer, whip-like for locomotion in the same structures that propel cells way that animal cells do. forward, such as in sperm cells' Plant cells are stationary and movement. Pseudopodia are form the structural basis of temporary, finger-like extensions plant tissues and organs. formed by the dynamic rearrangement of the cell's cytoskeleton, allowing cells like amoebas to "crawl" and extend and retract these projections for directional movement. 35  09/09/2023 Cytokinesis, the division of the In plant cell cytokinesis, plant cytoplasm during cell division, is a cells construct a specialized crucial step in animal cell structure called a "cell plate." replication. In animal cells, The cell plate is formed from cytokinesis typically occurs when vesicles derived from the a contractile ring of actin filaments Golgi apparatus, which coalesce at the center of the forms just beneath the cell dividing cell. These vesicles membrane. As this ring contracts, gradually fuse together, it creates a cleavage furrow that creating a membranous gradually pinches the cell partition that ultimately membrane inward, ultimately divides the cell into two dividing the cell into two daughter daughter cells. The cell plate is cells. This process ensures that then reinforced with each daughter cell receives a additional cell wall material, portion of the organelles and resulting in the formation of cytoplasm required for two distinct plant cells. independent functioning, completing the cell division cycle. Glyoxysomes are specialized organelles primarily found in Animal cells lack Glyoxysomes, as plant cells, particularly in their energy metabolism and lipid germinating seeds, and some utilization processes differ from microorganisms like certain those of plants and certain bacteria and fungi. These microorganisms. Animal cells organelles play a crucial role primarily rely on mitochondria for in lipid metabolism, particularly the conversion of energy production, where the stored lipids into breakdown of lipids occurs carbohydrates for energy through beta-oxidation, distinct during early seedling growth. from the glyoxysomal pathway found in plant cells. 36  09/09/2023 Lysosomes are membrane- Plant cells typically contain bound organelles found in few, if any, lysosomes, as animal cells, and they serve as their primary organelle for the cell's recycling centers. handling molecule Inside lysosomes, a variety of degradation is the central hydrolytic enzymes are present vacuole. The central vacuole functions similarly to the that can break down cellular lysosomal function in animal macromolecules such as cells. This distinction reflects proteins, lipids, carbohydrates, the unique adaptations and and nucleic acids. This specialized organelles that degradation process is plant cells have evolved to essential for the cell's meet their specific metabolic maintenance, as it allows for and structural needs. the recycling of materials and the disposal of waste products, contributing to overall cellular health and function. Animal cells typically do not Plant cells contain plastids, contain plastids; instead, they including chloroplasts, which rely on mitochondria for are essential for the process energy production and various of photosynthesis. other organelles for specific Chloroplasts are specialized cellular functions. This absence organelles that contain pigments like chlorophyll, of plastids in animal cells enabling plants to capture highlights one of the many sunlight and convert it into structural and functional chemical energy in the form differences between plant and of glucose and other organic animal cells molecules. This unique capability allows plants to produce their own food and energy, making chloroplasts a defining feature of plant cells and a key contributor to the Earth's oxygen and carbon dioxide balance. 37  09/09/2023 Plant cells are interconnected through plasmodesmata, which are microscopic channels that traverse the cell Animal cells do not possess walls of adjacent plant cells. plasmodesmata. Instead, These channels facilitate the animal cells are separated by exchange of various extracellular matrix and molecules, including water, connective tissues ions, nutrients, and signaling molecules, allowing for coordinated responses and resource sharing among plant cells. Plasmodesmata are crucial for plant growth, development, and responses to environmental cues, serving as conduits for intercellular communication and nutrient transport. Animal cells typically contain Plant cells typically contain a smaller and fewer vacuoles large central vacuole that is a compared to plant cells. While defining feature of their some animal cells may possess structure. This vacuole can small vacuoles, their function occupy a significant portion of and prevalence vary widely the cell's volume, often up to among different cell types. In 90%. The central vacuole plays animal cells, vacuoles often several crucial roles, including serve specialized roles, such as storing water, maintaining storing specific molecules or turgor pressure to support the assisting in processes like cell's shape, storing nutrients phagocytosis (cellular and waste products, and engulfment) and exocytosis participating in various (cellular secretion), rather than cellular processes, such as pH regulation and detoxification. functioning primarily for water and nutrient storage, as in plant cells. 38  09/09/2023 The overall function of an animal The overall function of a plant cell cell is to contribute to the structure is to support the growth, and function of animal tissues and development, and functioning of organs within multicellular the entire plant organism. Plant organisms. Animal cells perform cells perform photosynthesis, a various vital roles, including energy critical process where they capture sunlight and convert it production through processes like into chemical energy, producing glycolysis and oxidative glucose and oxygen. Additionally, phosphorylation, carrying out they store nutrients, water, and cellular respiration to generate ATP. other essential compounds, They also participate in complex contribute to structural support physiological functions such as cell through the cell wall, and engage signaling, immune responses, in various metabolic processes sensory perception, and tissue that sustain the plant's life cycle, repair, collectively enabling the ultimately allowing it to thrive organism's growth, development, and reproduce. and survival. 39