3-Functional Anatomy of Prokaryotic and Eukaryotic Cells Study Guide PDF

3_FUNCTIONAL ANATOMY OF PROKARYOTIC AND EUKARYOTIC CELLS (1 - 34) Key Terms Centrosome The centrosome is an organelle located near the nucleus of animal cells, consisting of a pair of centrioles and pericentriolar material, which plays a crucial role in cell division. Centrosomes help organize...

3_FUNCTIONAL ANATOMY OF PROKARYOTIC AND EUKARYOTIC CELLS (1 - 34) Key Terms Centrosome The centrosome is an organelle located near the nucleus of animal cells, consisting of a pair of centrioles and pericentriolar material, which plays a crucial role in cell division. Centrosomes help organize microtubules during cell division, aiding in the formation of the mitotic spindle. They are involved in determining cell polarity and positioning of the nucleus within the cell. Abnormalities in centrosome function can lead to cellular defects and are associated with diseases like cancer. Centrosomes are essential for proper segregation of chromosomes during mitosis and meiosis. Chloroplasts Chloroplasts are organelles found in plant cells that are responsible for photosynthesis, converting light energy into chemical energy. Chloroplasts contain the pigment chlorophyll, which gives plants their green color and aids in capturing sunlight for photosynthesis. The structure of chloroplasts includes an outer membrane, inner membrane, thylakoids, and stroma, where different stages of photosynthesis occur. Chloroplasts have their own DNA and ribosomes, enabling them to synthesize proteins necessary for photosynthesis. In addition to photosynthesis, chloroplasts also have functions like lipid metabolism, hormone biosynthesis, and amino acid synthesis. Cilia Cilia are hair-like structures found on the surface of certain cells that are responsible for movement and sensory functions. Cilia are found in the respiratory tract and help in moving mucus and trapping foreign particles. They are also present in the female reproductive system to aid in moving the egg through the fallopian tubes. Cilia can be found in the inner ear, where they help convert sound vibrations into electrical signals for the brain to interpret.  In some unicellular organisms, cilia enable locomotion and feeding by creating a current of water to bring in food. cytoplasm Cytoplasm is a thick, jelly-like substance that fills the interior of a cell and holds various cellular components. Cytoplasm contains organelles, such as mitochondria and ribosomes, which are responsible for important cellular functions. Proteins and other molecules that are necessary for cell growth and metabolism are synthesized in the cytoplasm. Cytoplasm plays a crucial role in cell movement and transportation of materials within the cell. It also protects the cell's genetic material and provides a stable environment for chemical reactions to occur. Endoplasmic reticulum The endoplasmic reticulum is a membranous network of tubules and flattened sacs involved in the synthesis, folding, modification, and transport of proteins and lipids. There are two types of endoplasmic reticulum: rough ER, which has ribosomes attached to it and is involved in protein synthesis, and smooth ER, which lacks ribosomes and is involved in lipid metabolism. The endoplasmic reticulum plays a vital role in maintaining cellular homeostasis by regulating calcium levels and detoxifying harmful substances. The rough ER acts as a scaffold for the assembly of ribosomes, which are responsible for protein synthesis. The smooth ER is involved in the synthesis of lipids, including phospholipids for cell membranes and steroids. The endoplasmic reticulum forms a continuous network throughout the cytoplasm, connecting various organelles and providing a pathway for molecule transport. Endospores Endospores are specialized structures formed by certain bacteria to protect themselves from unfavorable conditions by entering a dormant state. Endospores are highly resistant structures that can survive harsh environments like extreme temperatures, lack of nutrients, and exposure to chemicals. Endospores can remain dormant for extended periods and are resistant to usual disinfectants and antibiotics. Endospores are difficult to kill and can only be eliminated by physical sterilization methods such as autoclaving. The formation of endospores is a survival strategy used by bacteria like Bacillus and  Clostridium. Endotoxin Endotoxin is a toxic component found in the outer membrane of certain gram-negative bacteria, released upon bacterial cell death or lysis. Endotoxins can cause fever, inflammation, and in severe cases, septic shock. They are lipopolysaccharides (LPS) and can trigger an immune response. Endotoxins are not actively secreted by bacteria but are part of their structure. Detection of endotoxins is crucial in pharmaceutical and healthcare settings to ensure product safety. Eukaryotes Eukaryotes are organisms made up of cells that have a true nucleus enclosed by a nuclear membrane and other membrane-bound organelles. Eukaryotes include protists, fungi, plants, and animals. Their cells are generally larger and more complex compared to prokaryotes. Eukaryotes can reproduce through sexual or asexual means. They can be single-celled, colonial, or multicellular organisms. Eukaryotic Cell Wall The Eukaryotic Cell Wall is a rigid outer covering found in cells of eukaryotic organisms, providing structural support and protection. Eukaryotic cell walls are primarily composed of cellulose, chitin, or glucans. The cell wall is located outside the cell membrane and acts as a barrier to protect the cell. Fungi, plants, and some protists have eukaryotic cell walls. Unlike prokaryotic cell walls, eukaryotic cell walls are more complex in structure and composition. Flagella Flagella are whip-like appendages found on the surface of some bacteria and protozoa that help with locomotion. Flagella are made up of protein subunits called flagellin. Flagella rotate like propellers, allowing the microorganisms to move in response to various stimuli. Some bacteria have a single flagellum, while others have multiple flagella arranged in different patterns.  Flagella can be important for pathogens, as they allow bacteria to move towards or away from specific host cells. Flagella can also play a role in biofilm formation, a complex process where bacteria attach to surfaces and form communities. Glycocalyx Glycocalyx is a sticky layer of polysaccharides or proteins surrounding bacterial cells, aiding in protection, adherence to surfaces, and evasion of host immune responses. Glycocalyx can exist in two forms - capsule (well-organized) or slime layer (loosely attached). It helps bacteria adhere to surfaces, forming biofilms, which can be problematic in medical settings. Glycocalyx can contribute to bacterial virulence by avoiding phagocytosis by immune cells. The composition and thickness of the glycocalyx layer vary among bacterial species and strains. Golgi complex The Golgi complex is an organelle involved in processing, packaging, and modifying proteins within the cell before they are sent to their destination. The Golgi complex consists of flattened, membrane-bound sacs called cisternae. It plays a crucial role in the synthesis of cell wall components in plant cells. The Golgi complex also functions in sorting and directing proteins to their appropriate organelles or out of the cell. It works in coordination with the endoplasmic reticulum to ensure proper protein transport and secretion. Lipopolysaccharides (LPS) Lipopolysaccharides (LPS) are large molecules found in the outer membrane of Gram-negative bacteria, consisting of lipid A, core polysaccharide, and O antigen. LPS is a potent endotoxin and can trigger strong immune responses in the host. It plays a crucial role in the pathogenicity of Gram-negative bacteria. LPS structure can vary among different bacterial species, contributing to antigenic diversity. Recognition of LPS by host immune cells can lead to the production of inflammatory mediators. Lysosomes Lysosomes are membrane-bound organelles responsible for the digestion of cellular waste and toxins.  Lysosomes contain digestive enzymes called hydrolases that break down macromolecules into smaller components. They help remove damaged or excess organelles within the cell through a process called autophagy. Lysosomes also play a vital role in phagocytosis, where they fuse with phagosomes to break down ingested pathogens. Deficiencies in lysosomal enzymes can lead to lysosomal storage diseases, such as Tay- Sachs disease. Lysozyme Lysozyme is an enzyme that destroys bacteria by breaking down the cell wall, specifically the peptidoglycan layer. Lysozyme is found in bodily fluids like tears, saliva, and mucus. It is a natural defense mechanism against bacterial infections. Lysozyme is often used in food preservation to inhibit bacterial growth. Some bacteria have developed resistance to lysozyme. mitochondria Mitochondria are organelles found in most eukaryotic cells. They are responsible for producing the majority of the cell's energy in the form of adenosine triphosphate (ATP). Mitochondria have their own DNA and can replicate independently within the cell. The number of mitochondria in a cell can vary depending on the energy requirements of the cell. Mitochondria are involved in many important cellular processes, including cell signaling and apoptosis (programmed cell death). Mitochondrial dysfunction has been linked to various diseases, including neurodegenerative disorders and cardiovascular diseases. Nucleus The nucleus is a membrane-bound organelle found in eukaryotic cells, containing DNA and serving as the control center for cellular activities. The nucleus is the site of DNA replication, transcription, and RNA processing. It contains the nucleolus, responsible for the production of ribosomes. The nuclear envelope regulates the movement of molecules between the nucleus and the cytoplasm. Nucleoplasm is the liquid inside the nucleus, supporting the organelle's structure and containing various components like chromatin and nucleosomes. Peptidoglycan Peptidoglycan is a unique molecule found in the cell walls of bacteria, providing structural support and protection. It consists of glycan chains cross-linked by peptide bridges. Peptidoglycan is responsible for the ability of bacteria to maintain their shape and resist changes in osmotic pressure. The cross-linking of peptidoglycan by peptide bridges adds strength and rigidity to the cell wall. Peptidoglycan can be targeted by antibiotics, such as penicillin, which disrupt its synthesis and weaken the bacterial cell wall. The thickness and composition of peptidoglycan can vary among different bacterial species, leading to differences in antibiotic susceptibility. Peroxisomes Peroxisomes are membrane-bound organelles found in eukaryotic cells that play a crucial role in lipid metabolism and the detoxification of harmful substances. Peroxisomes contain enzymes called peroxidases, which break down hydrogen peroxide into water and oxygen. Peroxisomes are involved in the beta-oxidation of fatty acids, converting them into energy- rich molecules. Peroxisomes also participate in the synthesis of certain types of lipids, such as plasmalogens. Defects in peroxisome function can lead to severe human genetic disorders known as peroxisome biogenesis disorders (PBDs). Plasma Membrane The plasma membrane is a semi-permeable barrier that surrounds the cell and controls the movement of substances in and out of the cell. The plasma membrane is composed of a phospholipid bilayer embedded with proteins. It plays a crucial role in maintaining the cell's integrity and regulating its internal environment. The plasma membrane allows selective transport of molecules through diffusion, osmosis, and active transport. It also contains various receptors and enzymes involved in cell signaling and communication. Prokaryotes Prokaryotes are single-celled organisms without a distinct nucleus or membrane-bound organelles. They can be classified as bacteria or archaea.  Prokaryotes are found in a wide range of habitats including soil, water, and the human body. They play important roles in various ecological processes such as nitrogen fixation and decomposition. Prokaryotes exhibit diverse shapes including spheres, rods, and spirals. Some prokaryotes are pathogenic and can cause diseases such as tuberculosis and cholera. Prokaryotic Cell Wall The prokaryotic cell wall is a rigid structure found outside the cell membrane, providing support and shape to the cell. It consists of peptidoglycan in bacteria, which maintains osmotic pressure. Some prokaryotes have cell walls containing various substances like lipids and proteins. The cell wall helps protect the cell from external stresses and invaders. Gram staining is a technique used to differentiate between different types of prokaryotic cell walls. Protoplast Protoplasts are bacterial or plant cells with their cell walls removed, making them susceptible to osmotic lysis. They are important for genetic transformation studies. Protoplasts can be generated by enzymatic digestion of cell walls. They lack cell walls but retain cell membranes. They are used in fusion experiments to create hybrid organisms. Protoplast regeneration involves providing appropriate nutrients and conditions. Ribosomes Ribosomes are cellular structures responsible for protein synthesis by translating the genetic information found in mRNA molecules into a sequence of amino acids. Ribosomes are composed of two subunits, a large subunit and a small subunit. They can be found in both prokaryotic and eukaryotic cells. Ribosomes can be free-floating in the cytoplasm or attached to the endoplasmic reticulum in eukaryotic cells. The process of translation occurs at the ribosomes, where tRNA molecules bring amino acids to the ribosome to be added to growing polypeptide chains. Spheroplast A spheroplast is a bacterial cell that has lost its cell wall, resulting in a spherical shape and increased susceptibility to osmotic lysis.  Spheroplasts are formed by treating bacterial cells with lysozyme or penicillin, which weaken the cell wall. Spheroplasts can be used in genetic studies to introduce foreign DNA into bacterial cells. The absence of a cell wall in spheroplasts makes them more permeable to certain molecules. Spheroplast formation is reversible by providing the necessary components for cell wall synthesis. Teichoic Acids Teichoic acids are cell wall components found in certain bacteria that help maintain cell structure and integrity. Teichoic acids can be classified as either wall teichoic acids (WTAs) or lipoteichoic acids (LTAs). They are negatively charged due to the presence of phosphate groups, which can influence bacterial interactions with their environment. Teichoic acids can modulate the permeability of the cell wall to certain molecules. WTAs are covalently linked to peptidoglycan, while LTAs are anchored to the cytoplasmic membrane. Vacuoles Vacuoles are membrane-bound organelles found in the cytoplasm of eukaryotic cells that store various substances such as water, nutrients, and waste products. Vacuoles help maintain the turgor pressure in plant cells, enabling them to maintain their shape. Some vacuoles in plants are filled with pigments that give flowers and fruits their bright colors. In animal cells, vacuoles are smaller in size and are involved in various functions such as storage, excretion, and osmoregulation. Contractile vacuoles are found in some protists and pump out excess water to help maintain the organism's osmotic balance.