Lethre 2 Flashcards
Microorganism can be divided into dintonfour separate groups
Make them
Fungi
Bacteria
Viruses
Parasites
What two things make up the cell envelope ?
What is the function of the cell envelope?
What are the two main different groups of bacteria
• •
• •
External covering outside thecytoplasm
Composed of two basic layers:
- Cell wall and cell membrane
All bacteria have cell wall
Cell envelope Maintains cell integrity
Two different groups of bacteria demonstrated by
Gram stain
- Gram-positive bacteria:thick cellwall composed primarily of peptidoglycan and cell membrane
- Gram-negativebacteria: outer membrane,thin peptidoglycan layer, and cell membrane
Cell wall determines cell shape and prevents lysis due to changing osmotic pressures
True or false
The cell membrane is a phospholipid bi layer
Yes, the cell membrane, also known as the plasma membrane, is primarily composed of a phospholipid bilayer. This bilayer consists of two layers of phospholipids, with their hydrophobic (water-repelling) tails facing inward and their hydrophilic (water-attracting) heads facing outward. This arrangement creates a semi-permeable membrane that regulates the passage of substances in and out of the cell.
True
Which type of bacteria has teichoic acid and lipoteichoic acid in their cell wall? Gram pos or gram neg?
What is the function of these acids?
What is the periplasmic space
Gram pos
Function:
function in cell wall maintenance and
enlargement during cell division; move cations across the cell envelope; stimulate a specific immune response
Some cells have a periplasmic space between the cell wall and cell membrane
Where is the peptidoglycan layer found in gram negatives cell wall
What does the outer membrane of the gram negative cell wall contain?
Which part of the outer membrane becomes toxic?
What is the function of the lipopolysaccharides in the outer membrane of the gram negative cell wall
What is the function of porins proteins in the upper layer of lipopolysaccharide
Inner and outer membranes
and periplasmic space between them contains a
thin peptidoglycan layer. So the peptidoglycan layer is in the periplasmic space. This periplasmic space is between the inner and outer membranes for gram negatives
Outer membrane contains
lipopolysaccharides (LPS)
• Lpidi portion (endotoxin)
may become toxic when released during
infections
•May function as
receptors and blocking immune response
• Contain porin proteins in upper layer - regulate molecules entering and leaving cell
The porins also confer anti microbial resistance to the gram neg bacteria by pumping out the antibiotics to prevent them from having an effect . Porins contribute to resistance mainly by reducing drug entry, while efflux pumps increase drug removal from the bacterial cell.
Porins work by facilitated diffusion as protein channels while Efflux transporters work using active transport
Lipopolysaccharide (LPS) and lipid A polysaccharide are components of the outer membrane of Gram-negative bacteria and play different roles in the structure and function of the bacterial cell wall:
- Structure: LPS is a complex molecule consisting of three main parts: lipid A, a core oligosaccharide, and an O-antigen (O-side chain).
- Function: LPS is an important structural component of the outer membrane of Gram-negative bacteria. It contributes to the structural integrity of the bacteria and helps protect against harmful substances. It also acts as an endotoxin and can trigger strong immune responses in the host.
- Structure: Lipid A is the lipid portion of LPS and is embedded in the bacterial membrane. It consists of a fatty acid component attached to a disaccharide backbone.
- Function: Lipid A is responsible for the toxic effects of LPS, such as fever and shock, in the host. It is the primary component that interacts with the host’s immune system and is crucial for the endotoxin activity of LPS.
Summary: Lipopolysaccharide (LPS) is the complete molecule found in the outer membrane of Gram-negative bacteria, while lipid A is the lipid component of LPS that is primarily responsible for its toxic effects.
Which bacteria lack typical cell wall structure
State two bacteria that have no cell wall at all?
Since those bacteria don’t have cell wall, what stabilizes their cell structure?
Some bacterial groups lack typical cell wall
structure, i.e., Mycobacterium and Nocardia
- they have a Gram-positive cell wall structure with lipid mycolic acid (cord factor)
Pathogenicity and high degree of resistance to certain chemicals and dyes
Is the Basis for acid-fast stain used for diagnosis of infections caused by these microorganisms
• Some have no cell wall, i.e., Mycoplasma and Chlamydia
- Cell wall is stabilized by sterols so they are the only type of bacteria that have sterols. The rest don’t have
- this bacteria is Pleomorphic
Explain the fluid mosaic model (this model explains the structure of the cell membrane)of the cell membrane structure
State three functions of the cell membrane
Phospholipid bilayer with embedded proteins - fluid mosaic model
Proteins do not stay in one place in the cell membrane. It keeps moving laterally in the lipid bilayer. 1. Fluid Nature: The lipid bilayer behaves like a two-dimensional fluid where lipids and proteins can move laterally within the layer, providing flexibility to the membrane.
2. Mosaic: The membrane is a mosaic of various proteins that float in or on the fluid lipid bilayer like boats on a pond.
Integral proteins span the entire cell membrane and peripheral proteins attach to the surface of the membrane . The mosaic is how the proteins and lipids float in or on the fluid lipid bilayer while the fluidity is how they are able to move laterally in the lipid bilayer which is mainly composed of phospholipids and is fluid
These proteins vary in size, shape, and function, and can move laterally within the lipid bilayer
• Functions in:
- Providing site for energy reactions, nutrient processing, and synthesis. They don’t have mitochondria so they use their cell membrane for energy production but they have ribosomes
- Passage of nutrients into the cell and discharge of wastes
- Cell membrane is selectively permeable
What is the function of the cell cytoplasm?
What does the cell cytoplasm contain?
How much of it is water?
Which part of the bacteria cell does energy synthesis occur?
Which part do general metabolic reactions occur?
Dense gelatinous solution of sugars, amino acids, and salts
- 70-80% water(intracellular water is more than extracellular water)
• Serves as solvent for materials used in all cell functions. The cytoplasm acts as a solvent by dissolving ions, nutrients, and metabolic products, which facilitates biochemical reactions and enzyme activity. It provides an aqueous environment that enables the distribution and movement of cellular components, ensuring proper cellular function.
To clarify:
• The cytoplasm is where many metabolic pathways, such as glycolysis and other biosynthetic processes, occur. • The cell membrane is the site for energy synthesis processes like oxidative phosphorylation and the electron transport chain in bacteria, as they lack mitochondria.
Given this distinction, if the question specifically asks about the site for energy synthesis in bacteria, the correct answer would be the cell membrane. However, if the question is about the site of general metabolic reactions, the cytoplasm would be the more encompassing answer.
In bacterial cells, metabolic reactions primarily occur in the cytoplasm and on the cell membrane. The cytoplasm is where many metabolic pathways, such as glycolysis and the Calvin cycle, take place. The cell membrane is involved in processes like oxidative phosphorylation and other electron transport activities because bacteria lack mitochondria.
In eukaryotic cells, metabolic reactions occur in various locations:
• The cytoplasm is where glycolysis and the pentose phosphate pathway take place. • The mitochondria are the sites for the citric acid cycle (Krebs cycle), oxidative phosphorylation, and fatty acid oxidation. • The endoplasmic reticulum is involved in lipid and protein synthesis. • The cytosol is where glycolysis and other metabolic processes occur outside of organelles.
So, in eukaryotic cells, while the cytoplasm is involved in some metabolic reactions, the mitochondria and other organelles are crucial for many specific pathways.
What is a nucleoid?
What’s the difference between the chromosome in bacteria and that in eukaryotes
What is a plasmid?
What is the plasmid used for?
Where are plasmids located in the bacteria?
The nucleoid is an irregularly shaped region within the cell but it doesn’t have a membrane. This is where the chromosome carrying the DNA is concentrated. The plasmids are in the nucleoid region.
• Chromosome
- Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell but eukaryotes have a rod like or straight double stranded DNA
• Plasmids
-Plasmids have extra chromosomal DNA which are Free small circular, double-stranded DNA. They confer antibiotic resistance genes to the bacterium. The plasmids do not really contribute to the total processes of the bacteria so without it, nothing happens
— Not essential to bacterial growth and metabolism
- Used in genetic engineering - readily manipulated and transferred from cell to cell
What is the central dogma theory
Who brought about this theory?
What is reverse transcription
How is the central dogma theory different from the modified central dogma theory
The central dogma of molecular biology describes the flow of genetic information within a biological system. It was first articulated by Francis Crick in 1958 and outlines the process by which the information in genes flows into proteins: DNA → RNA → Protein. The key steps are:
- Replication: DNA makes a copy of itself.
- Transcription: DNA is transcribed into messenger RNA (mRNA). During this process, the enzyme RNA polymerase reads the DNA sequence of a gene and synthesizes a complementary RNA strand.
- Translation: mRNA is translated into a protein. Ribosomes read the mRNA sequence and assemble the corresponding amino acids into a polypeptide chain, which then folds into a functional protein.
The modified central dogma of molecular biology includes additional pathways that extend beyond the original concept, which states that genetic information flows from DNA to RNA to protein. The modifications reflect discoveries about how genetic information can be processed and utilized in various ways. Here’s a detailed overview:
- DNA → RNA → Protein
-
Reverse Transcription:
- Description: RNA is converted into DNA by reverse transcriptase.
- Examples: Retroviruses (e.g., HIV) and certain cellular processes in eukaryotes.
- Impact: Demonstrates that information flow can go from RNA to DNA, which was not accounted for in the original dogma.
-
RNA Replication:
- Description: RNA serves as a template for the synthesis of more RNA.
- Examples: RNA viruses (e.g., influenza, coronaviruses).
- Impact: Shows that RNA can replicate independently of DNA.
-
Non-coding RNAs:
- Description: RNAs that are not translated into proteins but have important regulatory functions.
- Examples: MicroRNAs (miRNAs), long non-coding RNAs (lncRNAs), and ribosomal RNA (rRNA).
- Impact: These RNAs play crucial roles in gene regulation and cellular processes without being converted into proteins.
-
Protein to Protein Interactions:
- Description: Proteins can influence the structure and function of other proteins without the involvement of nucleic acids.
- Examples: Prions, which are misfolded proteins that can induce other proteins to misfold.
- Impact: Illustrates that information transfer and disease mechanisms can occur through proteins alone.
What percentage of ribosomal RNA are bacterial ribosomes made up of ?
What about protein in the bacterial ribosomes?
What is the function of the ribosomes?
Ribosomes
- Made of 60% ribosomal
RNA and 40% protein
- Consist of two subunits: large and small. Drugs target either the large or small subunit
- Prokaryotic differ from eukaryotic ribosomes in size and number of proteins
- Site of protein synthesis
- Found in all cells
If you have to pick between the Golgi apparatus and the endoplasmic reticulum (ER) for the site primarily responsible for protein folding in an MCQ, the correct answer would be the endoplasmic reticulum (ER).
The ER is specifically involved in the initial stages of protein folding, especially the rough ER, which is studded with ribosomes. It is here that newly synthesized proteins are folded and undergo quality control before being transported to the Golgi apparatus for further processing and sorting.
The Golgi apparatus mainly functions in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other parts of the cell, but it is not primarily responsible for the initial folding of proteins.
What are the functions of inclusions and granules structures in the bacteria?
Which bacteria are these inclusions and granules usually found in?
• Inclusions and granules
- Intracellular storage bodies
- Vary in size, number, and content
- Bacterial cell can use them when environmental sources are depleted
So the bacteria can put carbs and amino acids in vesicles and make use of them when environmental sources are depleted.
These are usually in bacteria that are spore forming
Which of the following are functions of the cytoskeleton of the bacteria?
A. Cell division
B. Cell shape regulation
C.plasmid partitioning
D. All of the above
E. None of the above
What is the cytoskeleton of the bacteria made up of?
• Cytoskeleton
- Many bacteria possess an internal network of protein polymers that is closely associated with the cell wall
- Cell division, cell shape regulation, plasmid partition(structure where most of the cytoplasmic content are held in place and the cytoskeleton helps in even distribution of plasmids during cell division. Plasmid partitioning refers to the process by which plasmids, which are small, circular DNA molecules found in bacteria and some eukaryotic organisms, are evenly distributed to daughter cells during cell division)
What are endospores and name three bacteria that produce them.
Explain the 2 phase life cycle of endospores
What is sporulation?
Sporulation is a means of reproduction true or false
What is germination
What extreme conditions can endospores withstand?
Spore formers are usually gram positive
Endospores
- Inert, resting, cells produced by some G+ genera:
Clostridium, Bacillus, and Sporosarcina
• Have a 2-phase life cycle:
- Vegetative cell - here, it is metabolically active and growing
- Endospore - it becomes an endospores or forms an endospores when exposed to adverse environmental conditions; capable of high resistance and very long-term survival
- Sporulation - formation of endospores or formation of hard covering around the bacterium and usually occurs in gram positives
• Hardiest of all life forms
• Withstands extremes in heat(too cold or too hot temperatures), drying, freezing, radiation, and chemicals
• Not a means of reproduction
- Germination - return to vegetative growth or the process to becoming the vegetative cell
How many years survival are endospores capable of?
Endospores are Dehydrated, metabolically inactive
True or false
What temperature can kill endospores?
What pressure can kill endospores?
• endospores have a Thick coat
• Longevity verges on immortality, 250 million years
• Resistant to ordinary cleaning methods and boiling
• Pressurized steam at 120°C for 15-20minutes will destroy. So autoclave will destroy these spores. Autoclaves typically operate at temperatures ranging from 121°C to 134°C (250°F to 273°F). The most common temperature used in autoclaving is 121°C (250°F), which is maintained under high pressure
Sure, autoclaves typically operate at pressures around 100 kPa to 150 kPa (kilopascals), which is equivalent to approximately 1 to 1.5 atmospheres of pressure. This converts roughly to about 15 psi (pounds per square inch) or 1 bar (standard atmospheric pressure)
Autoclaves generally operate at a pressure of approximately 103 kPa (kilopascals), which is equivalent to 15 psi. For higher settings, such as 20 psi, the pressure would be around 138 kPa.
the three basic shapes of bacteria are cocci (spherical),bacilli(rod) and spirillum(helical,comma,twisted rod)
Vary in shape, size, and arrangement but typically described by one of three basic shapes:
1.Coccus - spherical
2. Bacillus - rod
• Coccobacillus - very short and plump
• Vibrio - gently curved
3.Spirillum - helical, comma, twisted rod,
• Spirochete - spring-like
Example is treponema pallidum which causes syphilis
there are five classification systems of prokaryotes
Which classification system focuses on colony appearance on growth medium or agar?
Which focuses on the bacteria producing catalase,those producing coagulase enzymes,etc ?
Which classification focuses on bacteria or prokaryote ability to break down RBCS
Which focuses on the cell shape and arrangement of prokaryotes
1.Microscopic morphology-the cell shape and arrangement
2. Macroscopic morphology - colony appearance on growth medium or agar. Proteus has a swarming appearance.
3. Bacterial physiology-those producing catalase,those producing coagulase enzymes,etc
4. Serological analysis-ability to break down RBCS
5. Genetic and molecular analysis
What is Bergey’s manual of determinative bacteriology?
What does it propose the classification of prokaryotes is based on?
State the two domains according to the book
Bacterial Taxonomy Based on
Bergey’s Manual
• Bergey’s Manual of Determinative
Bacteriology - five volume resource covering all known prokaryotes
- Classification based on genetic information - phylogenetic(looking at characteristics that bacteria share with a certain ancestry. Phylogenetics studies evolutionary relationships through phylogenetic trees, revealing common ancestry and divergence among organisms based on genetic or morphological traits. It’s crucial for understanding biodiversity, evolutionary history, and species relationships in biology.)
- Two domains: Archaea and Bacteria
- Five major subgroups with 25 different phyla
Which microbes are the most abundant on earth?
What type of parasites are viruses?
There is no universal agreement on how and when viruses originated
• Viruses are considered the most abundant microbes on earth
• Viruses played a role in the evolution of Bacteria, Archaea, and Eukarya
• Viruses are obligate intracellular parasites-Obligate intracellular parasites are organisms that can only reproduce inside the cells of a host organism. They rely entirely on the host cell’s machinery for their replication and survival because they lack the necessary components to live independently.
