CHAPTER 3-4 STUDY GUIDE.pdf

1. Describe the cell theory and relationship of surface area to volume ratio relative to cell size. Cell Theory: o All living organisms are composed of one or more cells. o The cell is the basic unit of life. o All cells arise from pre-existing c...

1. Describe the cell theory and relationship of surface area to volume ratio relative to cell size. Cell Theory: o All living organisms are composed of one or more cells. o The cell is the basic unit of life. o All cells arise from pre-existing cells. The cell theory emphasizes that cells are the fundamental building blocks of all life. This concept is essential to understanding that every function in an organism is carried out by cells. Surface Area to Volume Ratio: o As cells increase in size, their volume increases much faster than their surface area. This limits the size of cells because a larger volume requires more nutrients and produces more waste, but a relatively smaller surface area makes it harder to efficiently exchange materials (nutrients, gases, waste) with the environment. o Smaller cells have a higher surface area-to-volume ratio, allowing for more efficient nutrient absorption, transporting water, and waste removal, which is why cells are typically small. 2. Describe the basic differences between prokaryotic and eukaryotic cells, including cell wall differences. Prokaryotic Cells: o Lack of a nucleus; DNA is free-floating in the cytoplasm. o No membrane-bound organelles. o Usually smaller and simpler. o Cell walls in bacteria are made of peptidoglycan; archaea have different cell wall compositions (pseudomurein). Eukaryotic Cells: o Have a true nucleus enclosed by a membrane. o Contain membrane-bound organelles (mitochondria, ER, Golgi apparatus, etc.). o Larger and more complex. o Cell walls (if present) are made of cellulose (in plants) or chitin (in fungi). 3. Describe the evolution of the 5 kingdoms of life. The five kingdoms of life classify organisms based on their cellular structure, mode of nutrition, and evolutionary relationships: 1) Monera (Prokaryote): Includes all prokaryotes (bacteria and archaea). These are single- celled organisms without a nucleus. 2) Protista: Eukaryotic, mostly single-celled organisms, such as protozoa and algae. These organisms are highly diverse, with some being autotrophic (photosynthetic) and others heterotrophic. 3) Fungi: Eukaryotic, mostly multicellular organisms (though yeasts are unicellular), such as molds, mushrooms, and yeasts. Fungi absorb nutrients through external digestion. 4) Plantae are eukaryotic, multicellular organisms that are autotrophic (perform photosynthesis) and have cell walls made of cellulose. This group includes trees, flowers, and grasses. 5) Animalia: Eukaryotic, multicellular organisms that are heterotrophic and lack cell walls. Includes humans, animals, and insects. 4. Describe the basic structure and function of the plasma membrane, cell wall, flagella, axial filament, fimbriae, pili, capsule, endospore, and chromosome of prokaryotes.  Plasma membrane: o Composed of a phospholipid bilayer with embedded proteins. It controls the movement of substances in and out of the cell and serves as a barrier to protect the cell from its environment. ▪ It is composed of: - Phospholipid bilayer: double layer of phospholipids each containing hydrophilic head and two hydrophobic tails. - Proteins help transport substances across the membrane, assist in cell signaling, maintain cell shape, and attach the cell to other cells. - Carbohydrates play a role in forming glycocalyx, a protective and functional layer on the cell surface. It serves as a barrier for the cell and facilitates cell adhesion. Cell wall: o Provides structure which is a sequence of NAG, NAM, and protection (osmotic pressure). In bacteria, it is made of peptidoglycan. Gram-positive bacteria have thick cell walls, while Gram-negative bacteria have thinner walls with an outer membrane. Flagella: o Long, whip-like structures aid in movement (motility) by rotating like a propeller 360 degrees and demonstrating 'run and tumble,' a type of motility that enables bacteria to navigate their environment. This movement is often in response to chemical signals known as chemotaxis. Axial filament: o Found in spirochetes, axial filaments are bundles of fibers located between the cell wall and the outer sheath. These filaments wrap around the cell and facilitate a corkscrew motion for movement. They contain internal flagella known as endoflagella. Fimbriae: o Short, hair-like projections that help the bacteria adhere to surfaces and other cells and twitching motility. They play a key role in attachment and colonization. Pili: o Longer than fimbriae, pili are used for the transfer of DNA between bacteria during a process called conjugation. Capsule o A gelatinous outer layer (sugary polysaccharides) found in some bacteria helps protect the cell from desiccation, phagocytosis, and adhesion. It is neatly organized and can enhance a bacterium’s ability to cause disease by hiding it from the immune system. Slime layer: o A type of glycocalyx that is loosely attached. It helps bacteria to adhere to surfaces and it is important in the formation of biofilms. Endospore: o A tough, resistant structure formed by certain bacteria (e.g., Bacillus and Clostridium) in harsh environmental conditions. Endospores can withstand extreme heat, desiccation, and radiation, germinating into active bacteria when conditions improve. They can contribute to the bacteria’s ability to cause disease. Chromosome: o A single, circular DNA molecule in prokaryotes contains all the genetic information required for the cell’s functions. Unlike eukaryotes, prokaryotes lack a nucleus, so the chromosome floats freely in the cytoplasm. 5. Describe the four flagella arrangements. 1) Monotrichous: A single flagellum located at one end (pole) of the cell. 2) Lophotrichous: A tuft of flagella at one or both (more than two) ends of the cell. 3) Amphitrichous: A single flagellum or cluster of flagella at both ends (one or two) of the cell. 4) Peritrichous: Flagella is distributed all around the surface of the cell. 6. Describe the four components of the plasma membrane. 1) Phospholipids: Form the basic bilayer structure, with hydrophobic tails facing inward and hydrophilic heads facing outward. 2) Proteins: Embedded within the bilayer or attached to the surface, these proteins perform functions such as transport, signal transduction, and acting as enzymes. 3) Cholesterol: Found in eukaryotic plasma membranes, it helps maintain the fluidity and stability of the membrane. 4) Carbohydrates: Often attached to proteins (glycoproteins) or lipids (glycolipids), they play a role in cell recognition and communication. 7. Describe the four types of movement across plasma membranes. Simple Diffusion: Movement of molecules from an area of high concentration to an area of low concentration. It does not require energy, and it often allows small molecules such as gas and oxygen to pass through easily. Facilitated diffusion is similar to diffusion but requires a transport protein to help large molecules, such as glucose, pass through the membrane. Osmosis: The movement of water across a semi-permeable membrane from an area of low solute concentration to high solute concentration (water follows high solute). o Water movement across the semipermeable membrane through osmosis: - Isotonic: the cell remains in normal or a state of equilibrium. - Hypertonic: water leaves the cell; the cell shrinks and undergoes plasmolysis (in plant cells) or crenation (in animal cells). - Hypotonic: Water enters the cell. The cell swells and may eventually burst (lyse) in the case of animal cells. It swells but doesn’t burst in animal cells and becomes turgid (firm) in plant cells. Active transport: The movement of molecules against their concentration gradient, from low to high concentration, using energy (ATP) and transport proteins. 8. Describe the cell wall of bacteria and archaea; bacterial cell wall composition, structure, and function; Gram-negative vs. Gram-positive cell walls. Bacterial cell wall: o Composed mainly of peptidoglycan, a mesh-like structure that gives the cell its shape and protects it from bursting in hypotonic environments. Archaeal cell wall: Does not contain peptidoglycan. Instead, archaea have cell walls made of pseudomurein proteins or other polymers, which help them survive in extreme conditions. Gram-positive cell wall: o A thick peptidoglycan layer retains the crystal violet dye during Gram staining, resulting in a purple color. o These bacteria have teichoic acids in their cell walls. o About 40-60 layers. o It doesn’t have an outer membrane. Gram-negative cell wall: o Thin peptidoglycan layer o It has an outer membrane containing lipopolysaccharides (LPS).  o It has proteins found in the outer membrane called Porins. These are water-filled channels that allow the passive diffusion of small molecules to cross the outer membrane. o The periplasmic space is located between the cytoplasmic membrane and the outer membrane, filled with a gel-like substance known as periplasm. o These bacteria do not retain the crystal violet dye but instead take up the counterstain (safranin), appearing pink. The outer membrane also serves as a barrier to certain antibiotics (resistant). 9. Describe the components, steps, and outcome of the Gram stain. Components: a) Crystal violet: The primary stain. Stains all bacteria purple. b) Iodine: A mordant that helps crystal stain sticks the crystal violet to the cell wall. c) Alcohol or acetone: Decolorizing agent. It washes out the stain in gram-negative bacteria. d) Safranin: Counterstains gram-negative bacteria red/pink. 10. Cell shapes and arrangements of bacteria: Shapes o Cocci – round/spherical bacteria o Bacilli – rod-shaped bacteria o Spirilla – spiral-shaped bacteria. Arrangements o Diplo – pairs o Strep – chains o Tetra – in four o Staph – clusters Arrangement is bacilli bacteria o Single – individual rod-shaped o Diplobacilli – two rod-shaped joined together o Streptobacilli – several rod-shaped linked together in a chain