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IVC Bio 15 Ch 4 Prokaryotic and Eukaryotic Cells Study Guide Key Terms: Binary fission a type of asexual reproduction where a cell divides into two identical daughter cells. It's a common method of reproduction for prokaryotic organisms like bacteria and archaea. Spiral a common feature in biology, from the shape of bacteria to the growth patterns of plants. Spiral-shaped bacteria Spirillum: A rigid, thick spiral-shaped bacterium that can move in a corkscrew motion Vibrio: A curved or comma-shaped bacterium that is a type of spirillum Spirochete: A thin, flexible spiral-shaped bacterium Movement: Spiral-shaped bacteria use flagella to move in a corkscrew pattern, which helps them move through viscous fluids like mucus Survival: The spiral shape of these bacteria helps them survive in environments with low nutrient concentrations Disease: Spiral-shaped bacteria can cause disease in humans and animals by invading host tissues Cocci spherical or round-shaped bacteria. Bacteria are of several shapes, and based on their morphology, they can be classified into – Cocci – They are typically spherical or oval-shaped. Bacilli – They are rod-shaped. Spirochaetes – They are slender and coiled. Bacilli a class of rod-shaped bacteria that are gram-positive, aerobic, and spore-forming. They are found in soil, water, and air, and are important in food microbiology. diplococcic tetrads a structure formed during prophase I of meiosis where two homologous chromosomes pair up, creating a group of four chromatids, which allows for genetic recombination through the process of crossing over; essentially, it's a set of four chromatids arising from the pairing of homologous chromosomes during meiosis, crucial for genetic diversity in offspring streptococci a genus of bacteria that are gram-positive and spherical in shape staphylococci pathogenic bacteria responsible for a broad spectrum of diseases with varying degrees of severity. They are one of the main causes of nosocomial infections (hospital- acquired infections) but can also be acquired outside hospitals. streptobacilli a genus of rod-shaped bacteria that are gram-negative and nonmotile. They are often arranged in chains. Spirilla a type of bacteria that have a rigid, spiral shape. They are long, thick, and move using flagella. highly motile. gram-negative vibrio a group of bacteria that live in aquatic environments and can cause disease in humans. They are rod-shaped, Gram-negative bacteria that prefer warm, brackish water. Spirochete a group of bacteria that have a spiral shape and flagella that allow them to move. They are found in soil, water, and the digestive tracts of animals. Some species of spirochetes are pathogenic and can cause diseases in humans and animals. Peptidoglycan a polymer that forms the cell wall of most bacteria. It's made of sugars and amino acids, and is also known as murein.
Pleomorphic occurring in different forms, or having variation in the size, shape, or texture of cells or nuclei. It can also refer to the ability of some microorganisms to change their shape or other characteristics in response to their environment. Glycocalyx a carbohydrate-rich coating that covers the outer surface of a cell membrane, composed of a network of glycoproteins and glycolipids, which acts as a protective barrier, facilitating cell-cell recognition, and playing a vital role in various cellular processes like adhesion and signal transduction; essentially, it's a "sugar coat" surrounding the cell. The glycocalyx is made up of complex sugar molecules (glycans) attached to proteins (glycoproteins) and lipids (glycolipids) on the cell membrane, creating a gel-like layer. capsule a protective layer around a cell or membrane. Capsules can be found in bacteria and fungi. slime layer a loose, unorganized layer of extracellular material, primarily composed of polysaccharides, that surrounds a bacterial cell and can be easily removed; it is considered a part of the glycocalyx and functions to protect bacteria, help them adhere to surfaces, and trap nutrients. Flagella hair-like appendages that help organisms move. They are found in many microorganisms, including bacteria, plant and animal sperm cells, and fungal spores. Chemotaxis the directed movement of a cell or organism towards or away from a chemical stimulus, essentially meaning it moves in response to a concentration gradient of a specific chemical in its environment, allowing it to navigate towards beneficial substances or away from harmful ones; this behavior is commonly observed in bacteria and immune cells like neutrophils. H antigen carbohydrate found on red blood cells and other cells in the body. It's a key part of the ABO blood group system and is a precursor to the A and B antigens.
from an area of low solute concentration to an area of high solute concentration. It's a vital process for transporting water and solutes across biological membranes. In hypotonic (solutions (lower concentration of solutes), water flows into cells and makes them swell When a cell is placed in a hypotonic solution (lower concentration of solutes/dissolved substances), water moves into the cell due to the concentration gradient, causing it to swell. In hypertonic solutions (higher concentration of solutes), water flows out of cells, which shrivels them up In isotonic solutions, cell volumes stay the same osmotic lysis the bursting of a cell due to an excessive influx of water caused by an osmotic imbalance, typically when a cell is placed in a hypotonic solution, leading to swelling and eventual rupture of the cell membrane, releasing its contents; essentially, the cell "explodes" from internal pressure built up by water moving into it via osmosis. glycoprotein glycolipids hypertonic a solution that has a higher concentration of solutes compared to the solution inside a cell, causing water to move out of the cell through osmosis, resulting in the cell shrinking or shriveling up; essentially, a hypertonic solution has more dissolved substances than the cell, drawing water away from it. hypotonic a solution has a lower concentration of solutes (dissolved substances) than the cell's contents. This causes water to move into the cell through osmosis, which can make the cell swell or even burst. Isotonic a solution that has the same solute concentration as the fluid inside a cell Lysosomes organelles in animal cells that break down and recycle cell parts, food waste, and unwanted debris. They are often called the cell's digestive system or recycling center. Lysozyme an enzyme that kills bacteria by breaking down the cell walls of certain bacteria. It's a key part of the body's innate immune system and is found in many bodily secretions, including tears, saliva, mucus, and sweat. Mitochondria membrane-bound cell organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell's biochemical. A mitochondrion is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate, which is used throughout the cell as a source of chemical energy. ribosome a cellular structure, composed of RNA and protein, that acts as the site for protein synthesis within a cell; it translates the genetic code from messenger RNA (mRNA) into a sequence of amino acids, which then form proteins. Exotoxin proteins secreted by bacteria that can damage the host cell by disrupting its metabolism or destroying it. They are highly potent and can cause severe symptoms, even in small quantities.
Endotoxin a complex molecule found in the outer membrane of Gram-negative bacteria. It's also known as lipopolysaccharide (LPS). Endotoxins are responsible for toxic effects like fever, septic shock, and multi-organ failure. teichoic acid a type of anionic polymer found exclusively in the cell walls of Gram-positive bacteria, where it is covalently linked to the peptidoglycan layer, contributing to the cell wall's structure and function; it is categorized into two types: wall teichoic acid (WTA) attached directly to the peptidoglycan and lipoteichoic acid (LTA) anchored in the cytoplasmic membrane, both playing roles in cell division, morphology, and interaction with the host immune system. =======================================================================
- Compare and contrast the overall cell structure of prokaryotes and eukaryotes. Be able to explain at least three similarities and three differences. Key differences: Nucleus: Prokaryotes lack a nucleus, meaning their DNA is free-floating in the cytoplasm, whereas eukaryotes have a well-defined nucleus enclosed by a nuclear membrane where DNA is stored. Organelles: Prokaryotic cells lack membrane-bound organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes, while eukaryotes have these specialized structures performing distinct functions. Cell size: Prokaryotic cells are generally much smaller than eukaryotic cells. Complexity: Due to the lack of organelles, prokaryotic cells have a simpler internal structure compared to the more complex compartmentalized organization of eukaryotic cells. Similarities: Basic components: Both prokaryotic and eukaryotic cells have a plasma membrane, cytoplasm, ribosomes, and genetic material (DNA). Cellular functions: Both types of cells perform essential life functions like metabolism, protein synthesis, and reproduction, although the mechanisms may differ.
Bacterial capsules are medically significant because they act as a key virulence factor, allowing pathogenic bacteria to evade the host immune system by preventing phagocytosis (engulfment by white blood cells), which significantly increases the bacteria's ability to cause disease; essentially, the capsule acts as a protective shield against the body's immune response. Protection from phagocytosis: The primary function of a bacterial capsule is to prevent white blood cells from recognizing and engulfing the bacteria, allowing them to survive and proliferate within the host. e. Explain the basic methods bacteria can use to move towards a stimulus or away from a stimulus. a process called "taxis", by using flagella, which are hair-like appendages that rotate to propel the cell, with the direction of rotation being controlled by the cell's perception of the stimulus, allowing it to move towards attractants (positive taxis) or away from repellents (negative taxis); this process is most commonly observed as "chemotaxis" when the stimulus is a chemical gradient, and "phototaxis" when the stimulus is light. f. Identify the function and composition ribosomes In a prokaryotic cell, ribosomes function as the site of protein synthesis, translating genetic information from mRNA into amino acid chains to build proteins; they are composed of two subunits, a smaller 30S subunit and a larger 50S subunit, both made up of ribosomal RNA (rRNA) and ribosomal proteins, collectively known as a 70S ribosome. g. Where is the DNA located in a prokaryotic cell? How is it packaged? In a prokaryotic cell, DNA is located in a central region called the "nucleoid," which is not enclosed by a nuclear membrane; the DNA is typically a single, circular chromosome that is condensed and packaged within the nucleoid through DNA supercoiling and interactions with specific proteins, allowing it to fit into the relatively small cell space.
- Compare and contrast the cell walls of gram-positive bacteria, gram-negative bacteria, acid-fast bacteria in terms of chemical composition and structure. Gram-positive bacteria have a thick layer of peptidoglycan as their primary cell wall component, lacking an outer membrane, while gram-negative bacteria have a thin peptidoglycan layer sandwiched between an inner and outer membrane, with the outer membrane containing lipopolysaccharides; acid-fast bacteria, considered a type of gram-positive bacteria, have a thick cell wall with
a high content of mycolic acids, a type of glycolipid, which gives them their unique acid-fast staining characteristic; making them resistant to many stains due to the lipid-rich layer. Key Differences: Gram-Positive: o Main component: Thick layer of peptidoglycan o Other components: Teichoic acids o Outer membrane: Absent Gram-Negative: o Teichoic acids: Absent Acid-Fast: o Distinguishing feature: High lipid content causing resistance to gram staining Explanation: Gram Staining: The difference in cell wall structure between gram-positive and gram-negative bacteria is the basis for the Gram staining technique. Gram-positive bacteria retain the crystal violet stain due to their thick peptidoglycan layer, appearing purple, while gram-negative bacteria lose the stain and appear pink. Mycolic Acids in Acid-Fast Bacteria: The presence of mycolic acids in acid-fast bacteria like Mycobacterium tuberculosis creates a waxy, hydrophobic layer that prevents most stains from penetrating, requiring a specialized acid-fast staining procedure.
- Be able to explain why drugs that target the cell wall are useful to kill the bacterial cell but typically do not harm human cells. Drugs that target the bacterial cell wall are effective against bacteria because they disrupt a vital structural component that human cells lack - the cell wall; since human cells do not have a cell wall, these drugs can kill bacteria without harming human tissue. Bacterial cell wall composition: Bacterial cell walls are primarily composed of a polymer called peptidoglycan, which is essential for their shape and protection. Human cell structure: Human cells only have a cell membrane, lacking the peptidoglycan-based cell wall that bacteria possess. Mechanism of action:
membrane surface, and integral proteins that extend partially through the membrane. Biochemical Composition: Phospholipids: The major lipid component, composed of a glycerol backbone, a phosphate group (hydrophilic head), and two fatty acid chains (hydrophobic tails). Membrane proteins: Diverse proteins with various functions including transport proteins (channels, pumps), receptors, enzymes, and structural proteins. Carbohydrates: May be attached to lipids (glycolipids) or proteins (glycoproteins) on the cell surface, contributing to cell recognition. Key Functions: Selective permeability: Regulates the movement of molecules across the membrane, allowing certain substances to enter or exit the cell while restricting others. Nutrient uptake: Facilitates the transport of essential nutrients into the cell through specific transport proteins. Waste excretion: Enables the removal of waste products from the cell. Maintaining cell shape: Provides structural support to the cell. Signal transduction: Receives and responds to external signals by interacting with specific receptors on the cell membrane.
- How are eukaryotic and prokaryotic cell membranes similar, how are they different? Both eukaryotic and prokaryotic cell membranes are composed of a phospholipid bilayer with embedded proteins, essentially acting as a barrier to control what enters and exits the cell; however, the key difference lies in the complexity of the eukaryotic cell membrane due to the presence of membrane- bound organelles within the eukaryotic cell, which are absent in prokaryotic cells, leading to a more intricate membrane composition in eukaryotes. Similarities: Basic structure: Both membranes are composed of a phospholipid bilayer with embedded proteins, acting as a selectively permeable barrier to regulate the movement of substances in and out of the cell. Function:
Both types of membranes perform similar functions like maintaining cell shape, regulating transport of molecules, and separating the cell from its environment. Differences: Organelle complexity: Eukaryotic cells have a variety of membrane-bound organelles like the nucleus, mitochondria, and endoplasmic reticulum, which are absent in prokaryotic cells. This means the eukaryotic cell membrane is involved in interactions with these organelles, leading to a more complex composition. Lipid composition: While both membranes contain phospholipids, the specific types of phospholipids can differ between eukaryotes and prokaryotes, potentially influencing membrane fluidity and function. Protein diversity: Eukaryotic membranes often have a wider variety of proteins compared to prokaryotic membranes due to the diverse functions of different organelles.
- Be able to explain simple diffusion , facilitated diffusion , osmosis , active transport. Simple diffusion: The passive movement of small, non-polar molecules directly through a cell membrane from an area of high concentration to an area of low concentration, without the need for any transport protein; essentially, molecules just "slip" through the membrane based on their concentration gradient. Facilitated diffusion: The passive movement of larger or polar molecules across a cell membrane with the help of a specific transport protein (channel or carrier protein) which allows them to move down their concentration gradient; this process still doesn't require energy input. Osmosis: A specific type of diffusion where only water molecules move across a semipermeable membrane from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration). Active transport: The movement of molecules across a cell membrane against their concentration gradient, requiring energy (usually in the form of ATP) and the involvement of specific transport proteins; this allows cells to accumulate molecules needed inside even if they are already present in higher concentrations outside. a. How are simple diffusion and facilitated diffusion similar? How are they different? Simple diffusion and facilitated diffusion are both considered passive transport mechanisms, meaning they don't require energy and move
concentration), while others do not require energy because they move molecules down their concentration gradient (from high to low concentration); this distinction is called "active transport" (requires energy) and "passive transport" (does not require energy) respectively.
- Be able to explain the fluid mosaic model of the plasma membrane The "fluid mosaic model" describes the structure of a cell membrane as a flexible, fluid bilayer composed primarily of phospholipids, with various proteins embedded within it, creating a mosaic-like appearance where components can move freely within the membrane plane; essentially, the membrane acts like a fluid with different molecules dispersed throughout, allowing for dynamic interactions and functions within the cell. Key points about the fluid mosaic model: Phospholipid bilayer: The foundation of the membrane is a double layer of phospholipid molecules, with their hydrophilic (water-loving) heads facing outwards towards the aqueous environment and their hydrophobic (water-hating) tails facing inwards. Protein integration: Proteins are embedded within the phospholipid bilayer, either partially (peripheral proteins) or completely spanning the membrane (integral proteins). Fluidity: The phospholipids in the bilayer are not static, they can move laterally within the plane of the membrane, giving it a fluid-like quality. Mosaic aspect: The diverse arrangement of different types of proteins and lipids embedded within the membrane creates a mosaic-like pattern. Cholesterol role: Cholesterol molecules are also present within the membrane, helping to maintain fluidity by preventing phospholipids from packing too tightly together at low temperatures. Important aspects of the fluid mosaic model: Selective permeability: The structure of the membrane allows certain molecules to pass through while restricting others based on their size, charge, and polarity. Cell signaling:
Receptor proteins on the membrane surface can bind to signaling molecules from other cells, initiating cellular responses. Transport functions: Membrane proteins facilitate the movement of molecules across the membrane through channels, pumps, and carriers. 11.Be able to explain a basic difference between eukaryotic and prokaryotic ribosomes. (*hint, it’s not size) Why might these differences be medically important? The key difference between eukaryotic and prokaryotic ribosomes, beyond size, is their protein composition, meaning the specific types of proteins that make up the ribosome subunits are distinct between the two cell types; this difference is medically important because it allows for the development of antibiotics that selectively target prokaryotic ribosomes, leaving eukaryotic cells unharmed. Key points about the differences: Protein composition: Eukaryotic ribosomes contain a more complex set of ribosomal proteins compared to prokaryotic ribosomes, providing a target for selective drug development. Antibiotic action: Many antibiotics, like streptomycin and erythromycin, work by binding to specific proteins on prokaryotic ribosomes, disrupting their function and preventing bacterial protein synthesis. 12.What are endospores? Why/when do they form? Why are they medically important? Endospores are dormant, tough structures that some bacteria produce to survive in harsh conditions. They are different from spores in plants and fungi, which are meant for reproduction. Endospores form when bacteria, primarily Gram-positive bacteria like Bacillus and Clostridium, experience unfavorable environmental conditions , most commonly when nutrients become scarce, leading to a lack of carbon or nitrogen, triggering a survival mechanism to create a dormant, highly resistant spore that can endure harsh conditions until better conditions arise for germination and reproduction; essentially, it's a way for the bacteria to survive extreme stress like high temperatures, desiccation, and chemical damage by encapsulating their genetic material in a protective shell.
Early eukaryotic cells engulfed bacteria capable of aerobic respiration, which evolved into mitochondria, providing the host cell with energy production capabilities. Origin of chloroplasts: In plant cells, photosynthetic bacteria were engulfed, leading to the development of chloroplasts that enable photosynthesis. Evidence supporting the theory: Mitochondria and chloroplasts have their own DNA, similar to bacterial DNA, and replicate independently within the cell, further supporting their prokaryotic ancestry. Review 2-5, 7, 8, MC 1-7, 9, 10 Analysis 5, CA 1
