micro mod. 2
Distinguish between illustrations of Gram-positive and Gram-negative cell walls.
+ has huge peptidoglycan cell wall - looks much more layered and complex.
Identify the four structures common to all cells.
All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell's interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like cytosol within the cell in which other cellular components are found; 3) DNA, the genetic material of the cell; and 4) ribosomes, which synthesize proteins.
Identify key differences in the cell structure of the two groups of prokaryotes: archaea and bacteria.
Bacteria lack histones. different membrane lipid comps. Bacterial cell walls are either made of peptidoglycan or they dont have one while archaea can be made of many things like Pseudopeptidoglycan, or Glycopeptide, or Polysaccharide, or Protein (S-layer), or None
Explain how prokaryotic ribosomes are similar to and different from eukaryotic ribosomes
Prokaryotic ribosomes are found in the cytoplasm. They are called 70S ribosomes because they have a size of 70S, whereas eukaryotic cytoplasmic ribosomes have a size of 80S. Although they are the same size, bacterial and archaeal ribosomes have different proteins and rRNA molecules, and the archaeal versions are more similar to their eukaryotic counterparts than to those found in bacteria.
Explain how the prokaryotic cell wall protects against changes in osmotic pressure.
cells that possess a cell wall undergo plasmolysis rather than crenation. In plasmolysis, the plasma membrane contracts and detaches from the cell wall, and there is a decrease in interior volume, but the cell wall remains intact, thus allowing the cell to maintain some shape and integrity for a period of time
Identify membrane transport mechanisms that are unique to eukaryotes.
endomembrane system is a series of membranous tubules, sacs, and flattened disks that synthesize many cell components and move materials around within the cell, endocytosis- the uptake of matter through plasma membrane invagination and vacuole/vesicle formation, cilia.
Define phototaxis and chemotaxis.
environmental signals, including light (phototaxis), and, most commonly, chemical gradients (chemotaxis).
Identify the major groups of microbes as either prokaryotic or eukaryotic. (This was also covered in chapter 1.3.)
pro: Bacteria, archaea, pathogens Euk: Protists, algae, protozoa, fungi, helmiths, viruses
nucleoid
region of the cell that contains primary DNA material, which includes several proteins and enzymes that transcribe DNA and RNA and assist with cell growth and development. Nucleoids are components of unicellular organisms classified as prokaryotes
Describe the bacterial endospore and its function. (You don't need to memorize the actual steps of sporulation.)
structures that essentially protect the bacterial genome in a dormant state when environmental conditions are unfavorable. allow some bacterial cells to survive long periods without food or water, as well as exposure to chemicals, extreme temperatures, and even radiation.
Explain the basic function of inclusions
the ability to store excess nutrients within cytoplasmic structures
Explain the difference between the two types of prokaryotic glycocalyx: capsules and slime layers.
A capsule is an organized layer located outside of the cell wall and usually composed of polysaccharides or proteins. A slime layer is a less tightly organized layer that is only loosely attached to the cell wall and can be more easily washed off. Slime layers may be composed of polysaccharides, glycoproteins, or glycolipids.
prokaryotic cell
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.
Identify two common bacterial species that produce endospores.
B. anthracis, the causative agent of anthrax & C. tetani which causes tetanus
Describe the following extracellular prokaryotic structures. Explain how bacteria use flagella as a means to respond to different stimuli in the environment.
Bacteria can move in response to a variety of environmental signals, including light (phototaxis), magnetic fields (magnetotaxis) using magnetosomes, and, most commonly, chemical gradients (chemotaxis). Purposeful movement toward a chemical attractant, like a food source, or away from a repellent, like a poisonous chemical, is achieved by increasing the length of runs and decreasing the length of tumbles. Bacteria achieve directional movement by changing the rotation of their flagella. In a cell with peritrichous flagella, the flagella bundle when they rotate in a counterclockwise direction, resulting in a run. However, when the flagella rotate in a clockwise direction, the flagella are no longer bundled, resulting in tumbles.
Recognize images of the different cellular shapes and cellular arrangements of prokaryotic cells.
Common shapes include spherical (coccus), rod-shaped (bacillus), or curved (spirillum, spirochete, or vibrio).
Eukaryotic cells
Contain a nucleus and other organelles that are bound by membranes.
The Gram stain is a common differential stain. Describe the structural differences between the cell walls of Gram-negative and Gram-positive bacteria. Include the following in your description: outer membrane, LPS, lipid A, teichoic acid, periplasm
Gram-positive cells- many layers of peptidoglycan totaling 30-100 nm in thickness. thickness. These peptidoglycan layers are commonly embedded with teichoic acids (TAs), carbohydrate chains that extend through and beyond the peptidoglycan layer.19 TA is thought to stabilize peptidoglycan by increasing its rigidity. TA also plays a role in the ability of pathogenic gram-positive bacteria such as Streptococcus to bind to certain proteins on the surface of host cells, enhancing their ability to cause infection. gram-negative cells, a gel-like matrix occupies the periplasmic space between the cell wall and the plasma membrane, and there is a second lipid bilayer called the outer membrane. This outer membrane is attached to the peptidoglycan by murein lipoprotein. The outer leaflet of the outer membrane contains the molecule lipopolysaccharide (LPS), which functions as an endotoxin in infections involving gram-negative bacteria, contributing to symptoms such as fever, hemorrhaging, and septic shock. Each LPS molecule is composed of Lipid A, a core polysaccharide, and an O side chain that is composed of sugar-like molecules that comprise the external face of the LPS
Explain why plasmids are often beneficial to an organism.
Plasmids often carry genes that confer advantageous traits such as antibiotic resistance;
Explain how plasmids differ from chromosomal DNA.
Prokaryotic cells may also contain extrachromosomal DNA, or DNA that is not part of the chromosome, extrachromosomal DNA is found in plasmids, which are small, circular, double-stranded DNA molecules.
Substances must be moved back and forth across the plasma membrane. Distinguish between simple diffusion, facilitated diffusion, and active transport across membranes.
Simple diffusion down a concentration gradient directly across the phospholipid bilayer. Facilitated: need the help of carriers or channels in the membrane. These structures ferry molecules across the membrane Active transport against a concentration gradient via a membrane pump that requires energy.
Explain how the presence of a capsule can help a microbe cause disease in its host.
The ability to produce a capsule can contribute to a microbe's pathogenicity (ability to cause disease) because the capsule can make it more difficult for phagocytic cells (such as white blood cells) to engulf and kill the microorganism.
Explain how the cell wall of acid-fast bacteria is unique and identify a species of acid-fast bacteria of medical importance.
The acid-fast staining protocol detects the presence of cell walls that are rich in mycolic acid. Mycobacterium tuberculosis
Contrast the functions of the prokaryotic cell membrane and cell wall.
The primary function of the cell wall is to protect the cell from harsh conditions in the outside environment. the cell membrane exhibits selective permeability, allowing some molecules to enter or leave the cell while restricting the passage of others.
Describe the basic structure of peptidoglycan.
alternating subunits of NAM and NAG with crosslinking peptides
Describe the structure and function of the prokaryotic plasma membrane (also called the cytoplasmic or cell membrane).
exhibits selective permeability, allowing some molecules to enter or leave the cell while restricting the passage of others. The plasma membrane structure of most bacterial and eukaryotic cell types is a bilayer composed mainly of phospholipids formed with ester linkages and proteins. These phospholipids and proteins have the ability to move laterally within the plane of the membranes as well as between the two phospholipid layers.
Distinguish between the function of bacterial flagella, fimbriae, and pili.
fimbriae commonly refers to short bristle-like proteins projecting from the cell surface by the hundreds. Fimbriae enable a cell to attach to surfaces and to other cells. pili commonly refers to longer, less numerous protein appendages that aid in attachment to surfaces Flagella are structures used by cells to move in aqueous environments. Bacterial flagella act like propellers.
Identify and describe the function of the major eukaryotic organelles shown in figure 3.35.
nucleus, which is surrounded by a complex nuclear membrane that houses the DNA genome nucleolus is a dense region within the nucleus where ribosomal RNA (rRNA) biosynthesis occurs. free ribosomes and membrane-bound ribosomes. Free ribosomes are found in the cytoplasm and serve to synthesize water-soluble proteins; membrane-bound ribosomes are found attached to the rough endoplasmic reticulum and make proteins for insertion into the cell membrane or proteins destined for export from the cell. endomembrane system, unique to eukaryotic cells, is a series of membranous tubules, sacs, and flattened disks that synthesize many cell components and move materials around within the cell SER does not have ribosomes and, therefore, appears "smooth." It is involved in biosynthesis of lipids, carbohydrate metabolism, and detoxification of toxic compounds within the cell. RER is studded with ribosomes bound on the cytoplasmic side of the membrane. These ribosomes make proteins destined for the plasma membrane The Golgi apparatus modifies lipids and proteins, producing glycolipids and glycoproteins, respectively, which are commonly inserted into the plasma membrane. lysosomes, membrane-bound organelles of the endomembrane system that contain digestive enzymes. peroxisomes play a role in lipid biosynthesis and breaking down various molecules. They may also have other specialized functions depending on the cell type. cytoskeleton made of microfilaments, intermediate filaments, and microtubules. This matrix of fibers and tubes provides structural support as well as a network over which materials can be transported within the cell and on which organelles can be anchored The large, complex organelles in which aerobic cellular respiration occurs in eukaryotic cells are called mitochondria chloroplasts, the organelles in which photosynthesis occurs cell walls provide structural stability for the cell and protection from environmental stresses The eukaryotic plasma membrane is composed of a lipid bilayer with many embedded or associated proteins. It contains cholesterol for the maintenance of membrane, as well as glycoproteins and glycolipids that are important in the recognition other cells or pathogens. Cells of animals and some protozoans do not have cell walls to help maintain shape and provide structural stability. Instead, these types of eukaryotic cells produce an extracellular matrix for this purpose. They secrete a sticky mass of carbohydrates and proteins into the spaces between adjacent cells
