Lecture Study Guide For Ch. 3 & 4 PDF

 Classify bacteria by shapes and arrangement. Shapes: Bacteria come in various shapes o Cocci – spherical shape. o Bacilli – rod-shaped. o Spirilla – spiral-shaped. o Vibrios – comma-shaped. o Spirochetes – corkscrew-shaped. Arrangement: Bac...

 Classify bacteria by shapes and arrangement. Shapes: Bacteria come in various shapes o Cocci – spherical shape. o Bacilli – rod-shaped. o Spirilla – spiral-shaped. o Vibrios – comma-shaped. o Spirochetes – corkscrew-shaped. Arrangement: Bacteria can also be classified based on their arrangements o Diplo – pairs. o Strepto – chains. o Staphylo – clusters. o Tetrads – group of four. o Sarcina – cube-like groups of eight.  Describe the structure and function of internal and external bacterial features. Features: Internal features of prokaryotes o Nucleoid – a region where the cell’s circular DNA is located and contains the genetic material of the cell. o Plasmids – small circular DNA molecules separate from the chromosomal DNA that carries genes that provide advantages such as antibiotics. o Ribosomes – smaller than eukaryotic ribosomes are the site of protein synthesis. o Cytoplasm – a gel-like substance filling the cell that contains all internal components and supports metabolic activities. External features of prokaryotes o Cell wall – made of peptidoglycan (bacteria) or pseudopeptidoglycan (archaea). It provides structure and protection against mechanical stress and osmotic pressure. o Plasma membrane – phospholipid bilayer with embedded proteins. It controls the entry and exit of substances and participates in metabolic processes. o Flagella – long whip-like appendages. Used for motility, allowing the cell to move towards or away from stimuli. o Pili/Fimbriae – hair-like structures on the cell surface that help in attachment to surfaces and in conjugation. o Capsule – a sticky gelatinous outer layer. Protects against desiccation, helps in adherence to surfaces, and evades the host immune system. Internal features of eukaryotes o Nucleus – membrane-bound organelle containing the cell’s DNA. It controls gene expression and mediates the replication of DN during the cell cycle.  o Endoplasmic reticulum (ER) Rough ER – a network of membranous tubules with ribosomes attached. It synthesizes and processes proteins. Smooth ER – lacks ribosomes. Synthesizes lipids, detoxifies chemicals, and stores calcium ions. o Golgi apparatus – a stack of membrane-bound vesicles and folded membranes. It modifies, sorts, and packages proteins and lipids for secretion or delivery to the organelles. o Mitochondria – double-membraned organelles with their DNA. It produces ATP through cellular respiration, the powerhouse of the cell. o Ribosomes – larger than prokaryotic ribosomes and it’s the sites of protein synthesis. o Cytoskeleton – a network of protein filaments (microfilaments, intermediate filaments, and microtubules). It provides structural support, aids in cell division, and facilitates cell movement. External features of eukaryotes o Plasma membrane – phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. It controls the entry and exit of substances involved in cell signaling and cell adhesion o Cell wall (in plants, fungi, and some protists) – composed of cellulose (in plants), chitin (fungi), or other materials. It provides structural support and protection and regulates turgor pressure. o Cilia and flagella – microtubule-based structures. Cilia move fluid or cells over their surface, flagella provide motility.  Describe the different types of bacterial motility and the structures associated with each. Filamento Flagellar motility – most common type of bacterial movement and involves the use of flagella. nook The use of long, whip-like appendages that extend from the bacterial cell rotate like a propeller and Fumble/rotate 3600 Basal Body to propel the bacterium through its environment. Run o Twitching motility – characterized by short, jerky movements across the surface. It uses a short hair-like structure (Pili/fimbriae) that contracts, pulling the bacterium forward. o Gliding motility – a slower, smooth form of movement typically observed in bacteria that lack flagella. Some gliding bacteria secrete a layer of slime which helps them slide. o Swarming motility – a coordinated group of movement of bacteria across a solid surface often observed as a rapid wave-like movement. This motility is usually required to produce surfactant to reduce surface tension. o Spirochete motility – a corkscrew-like motion that allows the bacteria to move through viscous environments like mucus. The axial filament wraps around the cell body and rotates causing the entire bacterium to rotate in a corkscrew fashion.  Relate the structure of the bacterial plasma membrane with its function. o The membrane is made up of two layers of phospholipids with hydrophilic heads on the outside and hydrophobic tails on the inside. o Various proteins are embedded in or attached to the membrane helping with different tasks. o Selective permeability – the phospholipid bilayer controls what enters and leaves the cell  o Transport substances through  Simple diffusion – small molecules pass through the membrane directly.  Facilitated diffusion – proteins help larger molecules pass through  Active transport – proteins use energy to move molecules against their concentration gradient.  Explain how substances can go through the bacterial plasma membrane, including the processes of simple diffusion, facilitated diffusion, active transport, and osmosis. o Simple diffusion – small, nonpolar molecules like oxygen or carbon dioxide can pass through the phospholipid bilayer without the need for any help. This doesn’t require energy. o Facilitated diffusion – larger or polar molecules like glucose or ions cannot easily pass through the lipid layer. Instead, they move through specific proteins (channels or carriers) in the membrane. This process doesn’t require energy. o Active transport – needs energy (ATP) because it moves substances against their concentration gradient. Membrane proteins known as pumps are involved in this process such as sodium- potassium pumps that move ions in and out of the cell. o Osmosis – water moves through the membrane sometimes via special proteins called aquaporins to balance the concentration of solutes (like salts or sugars) inside and outside the cell. This process doesn’t require energy.  Describe the detailed structure of Gram-positive and Gram-negative bacterial cell walls o Gram-positive bacterial cell wall:  Thick peptidoglycan layer which can be up to 40 layers. It provides the strength and shape of cells.  Teichoic acids are molecules embedded in the peptidoglycan layer. They help stabilize the cell wall and play a role in cell division.  Gram-positive bacteria do not have an outer membrane making them more sensitive to certain antibiotics.  Periplasmic space is the space between the cell membrane and the cell wall that is very small or absent in Gram-positive bacteria.  Gram-positive bacteria stain purple because their thick peptidoglycan layer retains the crystal violet dye even after the decolorization step. o Gram-negative bacterial cell wall  Thin peptidoglycan, only 1-2 layers thick. It is found in the periplasmic space between the inner and outer membranes.  Gram-negative bacteria have an outer membrane made of a lipid bilayer. The outer part of this membrane contains lipopolysaccharides (LPS). It provides extra protection and makes these bacteria more resistant to antibiotics.  Porins are protein channels in the outer membrane. They allow small molecules to pass into the cell.  The periplasmic space between the inner and outer membranes is more pronounced in Gram-negative bacteria. Gram-negative bacteria don’t have teichoic acids.  Gram-negative bacteria stain red or pink because the crystal violet is washed out, and they take up the red or pink counterstain instead.  Relate the structure of Gram-positive and Gram-negative cell walls to their differing properties. o Gram-positive bacteria have a thick peptidoglycan layer makes them strong, able to retain the purple dye but more susceptible to certain antibiotics since they lack an outer membrane. o Gram-negative bacteria have a thin peptidoglycan layer and protective outer membrane making them more resistant to antibiotics and environmental threats, but they do not retain purple dye and instead stain pink or red.  Explain the function of peptidoglycan cell walls concerning osmosis and osmotic pressure. o Osmosis – is the movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. o Osmotic pressure – is the pressure exerted by the movement of water into the cell. When the inside of the cell has a higher concentration of solutes than the outside environment, water tends to move into the cell creating osmotic pressure. Function of Peptidoglycan cell wall o Providing structural support – the peptidoglycan cell wall is strong and rigid surrounding the cell membrane. It helps resist the osmotic pressure that builds up when water enters the cell, preventing the cell from bursting. o Maintains cell shape – the peptidoglycan wall keeps the bacterial cell in its proper shape. This helps the cell withstand changes in pressure from water entering or leaving the cell. o Preventing cell lysis (bursting) – the cell wall prevents cells from bursting when water flows in. it counteracts the pressure caused by water entering the cell.