microbiology

Question 1

define virus

Answer 1

A virus is a tiny infectious agent that can only replicate inside the living cells of an organism. It’s essentially a piece of genetic material (DNA or RNA) surrounded by a protective protein coat.

Question 2

define bacteria

Answer 2

Prokaryotic: They lack a nucleus and other membrane-bound organelles.
Unicellular: Each bacterium is usually a single cell.
Diverse: They come in various shapes (spherical, rod-shaped, spiral) and can have different metabolic abilities.
Beneficial and harmful: Many bacteria are essential for life, while others can cause diseases.

Question 3

define fungi

Answer 3

Fungi are a kingdom of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.

Eukaryotic: They have cells with a nucleus.
size: 2-12 um.
Heterotrophic: They obtain nutrients by absorbing organic matter from their environment.
Cell wall: They have a cell wall, but it’s composed of glucan and chitin, not cellulose like plants.
Reproduction: They reproduce through motosis or meiosis. they can be haploid or diploid.
Diverse: Fungi come in various forms, from single-celled yeasts to multicellular mushrooms.

Question 4

define parasites

Answer 4

A parasite is an organism that lives on or in another organism (the host) and benefits by getting nutrients at the host’s expense. This relationship often harms the host, but not always fatally.

size: 10-12 um
Dependence on host: They rely on the host for survival.
Harm to host: While some parasites cause minimal harm, others can cause severe illness.
Diverse group: Parasites can be animals, plants, fungi, or even bacteria.

Question 5

define virulence

Question 6

what is the size of bacteria?

Answer 6

0.1-10 um

Question 7

what uniqe polymer does bacteria have? where?

Answer 7

peptidoglycan - in the cell wall

Question 8

define peptidoglycan

Answer 8

Peptidoglycan is a complex molecule composed of sugars (NAG and NAM) and amino acids. forms a layer surrounding the bacterial cytoplasmic membrane. It is a key component of the bacterial cell wall and provides structural support and protection (from osmotic pressure and external threats).

Many antibiotics, such as penicillin, target peptidoglycan synthesis, disrupting cell wall formation and leading to bacterial death.

Question 9

does bacteria have organle?

Answer 9

no, just ribosomes

Question 10

describe the DNA of a bacteria

Answer 10

Circular: Double stranded circular DNA, forming a closed loop.

Single chromosome: Bacteria typically have a single, large chromosome containing most of their genetic information.

Plasmids: In addition to the main chromosome, many bacteria also contain smaller, circular DNA molecules called plasmids. These carry extra genes that can provide advantages like antibiotic resistance or the ability to produce toxins.

Question 11

define binary fission

Answer 11

Binary fission is a type of asexual reproduction where a single-celled organism divides into two identical daughter cells. This is the primary method of reproduction for prokaryotes, such as bacteria, and some single-celled eukaryotes.

Key steps in binary fission:
DNA Replication: The organism’s single circular DNA molecule replicates.
Cell Growth: The cell increases in size.
Division: The cell splits into two identical daughter cells, each containing a complete copy of the original DNA.

Question 12

define archaebacteria - and where can be found?

Answer 12

Archaea (formerly known as archaebacteria) are a domain of single-celled microorganisms. While they were initially classified as bacteria due to their similar appearance under a microscope, they have since been recognized as distinct from bacteria and eukaryotes.

Prokaryotic: Like bacteria, they lack a nucleus.
Extremophiles: Many archaea thrive in extreme environments, such as hot springs, acidic conditions, and highly saline waters.
Unique biochemistry: Their cell walls, membranes, and genetic makeup differ significantly from bacteria.

Question 13

why can’t viruses replicate by themselves?

Answer 13

They lack the necessary cellular machinery to replicate independently.

No ribosomes: Ribosomes are cellular structures responsible for protein synthesis. Viruses do not have their own ribosomes.
No metabolic capabilities: Viruses cannot generate energy or produce the building blocks needed to create new viral particles.
Simple structure: Unlike cells, viruses consist of only genetic material (DNA or RNA) surrounded by a protein coat.

Question 14

how does bacteria reproduce?

Answer 14

by asexual reproduction

Question 15

what are the major forms of bacteria?

Answer 15

Bacteria are primarily classified based on their shape.

Cocci: Spherical shaped bacteria.
Examples: Streptococcus (causes strep throat), Staphylococcus (causes skin infections)

Bacilli: Rod-shaped bacteria.
Examples: E. coli, Bacillus subtilis (found in soil)

Spirilla: Spiral or helical shaped bacteria.
Examples: Campylobacter (causes food poisoning), Treponema pallidum (causes syphilis)

Vibrio: Comma-shaped bacteria.
Examples: Vibrio cholerae (causes cholera)

Coccobacilli: intermediate in shape between cocci (spherical) and bacilli (rod-shaped).
Examples: Bordetella pertussis (causes whooping cough) and Haemophilus influenzae (causes pneumonia and meningitis).

Fusiform: are spindle-shaped, meaning they are elongated with pointed ends.
Examples: Fusobacterium species, which are commonly found in the human mouth and can contribute to dental infections.

Question 16

how can bacteria be arranged?

Answer 16

Bacteria can be arranged in various ways, even though they have a basic shape (cocci, bacilli, spirilla). These arrangements are primarily determined by the plane(s) in which the bacteria divide and how they stick togther.

Arrangements of Cocci:
Single: Individual coccus.
Diplococci: Pairs of cocci.
Streptococci: Chains of cocci.
Tetrad: Groups of four cocci in a square arrangement.
Sarcinae: Cube-like arrangement of eight cocci.
Staphylococci: Irregular clusters of cocci.

Arrangements of Bacilli:
Single: Individual bacillus.
Diplobacilli: Pairs of bacilli.
Streptobacilli: Chains of bacilli.
Palisades: Bacilli arranged side by side like matchsticks.

Question 17

how the fact that bacteria is very small can help it?

Answer 17

Rapid Reproduction: Due to their small size, bacteria can reproduce very quickly through binary fission. This allows them to adapt to changing environments rapidly and outcompete other organisms for resources.

Efficient Nutrient Uptake: A large surface area-to-volume ratio enables bacteria to absorb nutrients efficiently, promoting rapid growth.

Easy Dispersion: Their small size allows bacteria to be easily dispersed by wind, water, and other means, enabling them to colonize new environments.

Evading Immune System: Many bacteria are small enough to evade detection by the immune system, allowing them to establish infections.

Habitat Diversity: Bacteria can inhabit a wide range of environments, from deep-sea hydrothermal vents to the human gut, due to their ability to survive in small spaces with limited resources.

Question 18

what is the bacterial composition?

Answer 18

envelope - capsule, cell wall, cell membrane.
appendages - pili, flagella.
core - cytosol, nucleoid, ribosoms, plasmids, inclusions (nutrient storage).

Question 19

why is the bacteria’s envelope important?

Answer 19

Protection
Barrier against external threats: The envelope acts as a shield, protecting the bacterium from harmful substances, antibiotics, and the host’s immune system.
Maintains cell shape: It provides structural rigidity, giving the bacterium its characteristic shape.
Osmotic protection: Prevents the cell from bursting or collapsing due to changes in osmotic pressure.

Cellular Functions
Selective permeability: Controls the movement of substances in and out of the cell, ensuring the right balance of nutrients and waste products.
Anchoring point: Provides attachment sites for pili, flagella, and other surface structures involved in motility, adhesion, and conjugation.
Cell division: Plays a role in cell division by providing a framework for the formation of new cell walls.

Virulence Factors
Adhesion: Some components of the envelope, like pili and capsules, help bacteria adhere to surfaces and host tissues, facilitating colonization.
Toxin production: The envelope can be involved in the production and secretion of toxins that harm the host.
Immune evasion: The envelope can help bacteria evade the host’s immune system by preventing phagocytosis or by masking the bacterium’s surface antigens.

Question 20

describe the capsule of bacteria

Answer 20

The bacterial capsule is a gel-like protective outer layer that surrounds the cell wall of many bacteria. It is composed primarily of polysaccharides.

Functions of the Capsule:
Protection: Protects the bacteria from desiccation, harmful chemicals, and antibiotics.
Virulence: Helps bacteria evade the host’s immune system by preventing phagocytosis (engulfment by white blood cells).
Adhesion: Enables bacteria to attach to surfaces, including host tissues, and form biofilms.

Question 21

describe the cell wall of bacteria

Answer 21

The bacterial cell wall is a rigid layer that surrounds the cell membrane and provides the cell with its shape. The primary component of the bacterial cell wall is peptidoglycan.

Functions of the cell wall:
Shape: Determines the shape of the bacterium (cocci, bacilli, spirilla).
Protection: Protects the cell from osmotic lysis and other environmental stresses.
Anchoring point: Provides attachment sites for pili, flagella, and other surface structures.
Target for antibiotics: Many antibiotics target the cell wall, disrupting its synthesis and leading to bacterial cell death.

Question 22

can peptidoglycan be found not in bacteria? where?

Answer 22

no, only in bacteria.

Question 23

define transpeptidases

Answer 23

Transpeptidases are enzymes that play a crucial role in bacterial cell wall synthesis. They are responsible for cross-linking the peptidoglycan chains, which gives the cell wall its strength and rigidity.
Essentially, they catalyze the formation of peptide bonds between amino acid residues in adjacent peptidoglycan strands.

Question 24

how does penicililin kill bacteria?

Answer 24

target the transpeptidases and inhibit their activity and prevent cell wall synthesis. Without functional transpeptidases, bacteria cannot maintain their cell shape and will eventually lyse (burst).

Question 25

define gram stain (positive and negative)

Answer 25

The Gram stain is a laboratory technique used to differentiate bacteria into two broad categories based on the structure of their cell wall: Gram-positive and Gram-negative.

Gram-positive bacteria: These bacteria have a thick layer of peptidoglycan outside the cell membrane. They also contain teichoi acids, which contribute to the cell wall’s structure and function.
Appearance: Stain purple or blue

Gram-negative bacteria: These bacteria have a thinner layer of peptidoglycan surrounded by an outer membrane. The outer membrane contains lipopolysaccharides, which contribute to the bacterium’s virulence.
Appearance: Stain pink or red

Question 26

define teichoic acids

Answer 26

Teichoic acids are polymers found in the cell wall of most Gram-positive bacteria. They are composed of glycerol phosphate or ribitol phosphate linked together by phosphodiester bonds.

Function:
Provide structural support to the cell wall.
Contribute to the negative charge of the cell surface.
Play a role in cell division.
Can be involved in bacterial virulence by acting as adhesins or by being antigens that stimulate an immune response.

Question 27

Define lipoprotein

Answer 27

lipoprotein is a complex particle composed of both lipids (fats) and proteins.

Gram-negative bacteria: Lipoproteins are primarily found in the outer membrane.
Gram-positive bacteria: Lipoproteins are less abundant but play essential roles in cell wall structure and function.

Bacterial lipoproteins have various functions, including:
Cell wall biogenesis
Outer membrane assembly
Protein secretion
Virulence factor
Adhesion
Signal transduction

Question 28

what layer is uniqe to gram negative bacteria?

Answer 28

The outer membrane is the layer unique to Gram-negative bacteria. It lies outside the thin peptidoglycan layer.
It is made of lipids and many enzymes like lysozymes.

This structure is crucial for the survival and virulence of these bacteria. It also contains lipopolysaccharides (LPS), which contribute to the bacterium’s ability to cause disease.

Question 29

define lipopolysaccharides (LPS)

Answer 29

Lipopolysaccharides (LPS), also known as endotoxins, are complex molecules that form a major component of the outer membrane in Gram-negative bacteria.

Functions of LPS:

Barrier: Protects the bacteria from antibiotics, bile salts, and other harmful substances.

Structural integrity: Maintains the stability and rigidity of the outer membrane.

Endotoxin activity: have toxic properties of LPS, triggering a strong immune response in the host, which can lead to septic shock if released in large quantities.

Question 30

define lysozyme

Answer 30

Lysozyme is an enzyme that acts as a natural antibacterial agent. It’s found in various bodily fluids such as tears, saliva, mucus, and egg white.
Lysozyme attacks the cell wall of bacteria, specifically targeting the peptidoglycan component. By breaking down peptidoglycan, lysozyme causes the bacterial cell to rupture and die.

Question 31

describe the cell membrane of a bacteria

Answer 31

It’s a thin, flexible barrier that separates the cell’s internal environment from its external surroundings.

Structure:
Phospholipid bilayer: The primary component is a double layer of phospholipids, similar to other cell types.
Lack cholesterol, which is found in eukaryotic cell membranes.
Proteins: Embedded within the phospholipid bilayer are various proteins that perform specific functions, such as transport, energy generation, and signaling. (up to 70% of its weight)

Functions:
Permeability barrier: Controls the passage of molecules into and out of the cell.
Segregation: of daugther chromosomes during cell division.
Energy production: Site of important metabolic processes, including electron transport and ATP synthesis.
Protein synthesis: Contains enzymes involved in protein synthesis.
Cell wall anchoring: In Gram-negative bacteria, lipoproteins anchor the outer membrane to the peptidoglycan layer.

Question 32

define flagella in bacteria

Answer 32

Flagella are long, helical structures made of protein flagellin that extend from the cell body of many bacteria. They are primarily used for locomotion, enabling bacteria to move through liquid environments.

Question 33

define taxis and chemotaxis

Answer 33

taxis = motility
Chemotaxis is a specific type of taxis where the movement of an organism is directed by a chemical stimulus.
Organisms can move towards (positive chemotaxis) or away from (negative chemotaxis) a chemical substance.
Bacteria often utilize chemotaxis to find nutrients or to avoid harmful substances.

Question 34

define flagellin

Answer 34

Flagellin is a protein that is the primary building block of the filament, which is the long, helical part of a bacterial flagellum. It forms a hollow cylinder by arranging itself in helical chains around the core of the filament.

Question 35

what are the differences between eukaryotic and prokaryotic flagella?

Answer 35

Movement
Prokaryotic flagella:
Rotate like a propeller, providing a spinning motion.
Eukaryotic flagella:
Undulate in a wave-like motion.

Composition
Prokaryotic flagella:
Primarily made of protein (flagellin).
Eukaryotic flagella:
Composed of microtubules (proteins) and associated proteins. 9+2.

Energy source
Prokaryotic flagella:
Obtain energy from the proton motive force across the cell membrane.
Eukaryotic flagella:
Require ATP for movement.

Question 36

define pili in bacteria

Answer 36

Pili are hair-like appendages found on the surface of many bacteria.
Pili are composed primarily of a protein called pilin.

Functions:
Adhesion: Pili help bacteria attach to surfaces, including host cells, allowing them to colonize and infect.
Conjugation: Conjugation pili facilitate the transfer of genetic material between bacteria.
Motility: In some cases, pili can contribute to bacterial movement, though this is less common than flagella-mediated motility.

Question 37

define adhesins

Answer 37

Adhesins are proteins or glycoproteins located on the surface of bacteria that enable them to adhere to other cells or surfaces. They are essential for bacterial colonization and infection.

Question 38

what are the 2 classes of pili in bacteria?

Answer 38

common pili - cover the surface of the bacteria and consist of adhesins (that promote attachment) and thus modulate bacterial colonization on surfaces and cells.

sex pillus - a specialized structure that facilitates the attchment of donor to recipient cells during the process of bacterial connjaction. promotes the exchange of DNA between gram-negative bacteria.

Question 39

whay does the cytosol in bacteria seem to be granular?

Answer 39

it is densely packed with ribosoms.

Question 40

why does bacteria have a higher growth rate? what reflect that?

Answer 40

Bacteria have high growth rates due to their simple structure, rapid reproduction through binary fission, and efficient metabolism.

Question 41

what’s the ribosomes size in prokaryotes?

Answer 41

70s

Question 42

do mitochondrias have ribosomes? what size?

Answer 42

yes they might have 70s ribosomes

Question 43

define inclusion bodies

Answer 43

Inclusion bodies are intracellular structures that are distinct from other cellular components.

No membrane: Unlike organelles, inclusion bodies are not enclosed by a membrane.
Storage function: Many serve as storage depots for nutrients (strach, glycogen, lipids, sulfur, polyphosphate) or waste products.
Other functions: Some inclusion bodies are involved in viral replication or are byproducts of cellular processes.

Question 44

is bacteria haploid or diploid ?

Answer 44

haploid

Question 45

define plasmids

Answer 45

Plasmids are small, extrachromosomal DNA molecules found in bacteria and some other microorganisms. They are physically separate from the chromosomal DNA and can replicate independently.

Circular DNA: Most plasmids are circular, double-stranded DNA molecules.
Independent replication: They can replicate autonomously within the host cell.
Gene carriage: Plasmids often carry genes that provide bacteria with genetic advantages, such as antibiotic resistance, the ability to produce toxins, or the ability to metabolize unusual substances.
Transferability: Plasmids can be transferred between bacteria, contributing to the spread of genetic information.

Question 46

define endospores

Answer 46

Endospores are dormant, tough, and non-reproductive structures produced by certain bacteria, the formation is triggered by adverse conditions like lack of nutrients. They are essentially the bacterium’s survival mechanism under harsh conditions (heat, desiccation, chemicals, and radiation).
they are do not capable of reproduction.
They can remain dormant for extended periods, even centuries.

Question 47

define sporulation

Answer 47

Sporulation is the process by which certain bacteria form endospores. It’s a complex series of developmental changes that occur within a vegetative cell in response to adverse environmental conditions. This process results in the formation of a highly resistant endospore.

Question 48

define germination

Answer 48

germination refers to the process by which an endospore returns to its vegetative state.

Question 49

what are the processes that bacteria growth requires?

Answer 49

1. metabolism- which produces complex material from the nutrients present in the environment.
2. regulation - coordinates the progression of hundreds of biochemical processes into an orderly and efficient synthesis of cell components and structures.
3. cell division - the creation of 2 independent living units from one.

Question 50

what are the differences between metabolic processes in bacteria versus human cells?

Answer 50

Energy Metabolism:
Bacteria: Diverse metabolic strategies, including aerobic respiration, anaerobic respiration, and fermentation. Many bacteria can switch between these modes depending on environmental conditions.
Humans: Primarily rely on aerobic respiration in mitochondria for energy production, with limited anaerobic capabilities in muscle cells.

Nutrient Acquisition:
Bacteria: Can utilize a wide range of organic and inorganic compounds as nutrients, including some that humans cannot digest. They often possess specialized transport systems for nutrient uptake.
Humans: Require complex organic molecules (proteins, carbohydrates, lipids) for energy and building blocks, and rely on digestive systems for breakdown and absorption.

time:
bacterial Metabolism typically processeds 10 to 100 times fater than in human cells. it can synthesizes macromolecules much more efficiently than human cells.

Question 51

classify bacteria based on how they obtain energy

Answer 51

Phototrophs: Utilize light as their primary energy source.

Chemotrophs:Obtain energy from the oxidation of chemical compounds.

Autotrophs: Use CO2 as their sole carbon source. Can be either photoautotrophs or chemoautotrophs.

Heterotrophs: Obtain carbon from organic compounds. Can be either photoheterotrophs or chemoheterotrophs.

Question 52

classify bacteria based on how they response and use oxygen

Answer 52

Obligate Aerobes
Require oxygen for growth and survival.
Utilize oxygen as a terminal electron acceptor in aerobic respiration.

Obligate Anaerobes
Cannot tolerate oxygen and die in its presence.
Utilize anaerobic respiration or fermentation for energy production.

Facultative Anaerobes
Can grow in both the presence and absence of oxygen.
Prefer oxygen for aerobic respiration but can switch to fermentation or anaerobic respiration.

Aerotolerant Anaerobes
Do not use oxygen for growth but can tolerate its presence.
Possess enzymes to detoxify reactive oxygen species.

Question 53

define biofilms

Answer 53

A biofilm is a community of microorganisms, primarily bacteria, embedded in a matrix of extracellular polymeric substances (EPS) that they produce. This slimy matrix adheres to surfaces, protecting the bacteria within from environmental stresses and allowing them to communicate and cooperate.

Examples of biofilms:
Dental plaque
Slime on rocks in rivers

Question 54

what are the fectors affecting growth of a bacteria?

Answer 54

Temperature: Different bacteria have optimal, minimum, and maximum growth temperatures.
Psychrophiles: Cold-loving
Mesophiles: Moderate-temperature loving (most human pathogens)
Thermophiles: Heat-loving
Hyperthermophiles: Extremely heat-loving

pH: Most bacteria prefer neutral pH (7.2-7.6), but some thrive in acidic or alkaline environments.
Acidophiles: Acid-loving
Alkaliphiles: Alkaline-loving

Osmotic pressure: Salt concentration affects water movement into and out of the cell.
Halophiles: Salt-loving

Oxygen requirements:
Obligate aerobes: Require oxygen
Obligate anaerobes: Cannot tolerate oxygen
Facultative anaerobes: Can grow with or without oxygen
Aerotolerant anaerobes: Tolerate oxygen but don’t use it

CO2:
some bacteria require higher levels of carbon dioxide.

Question 55

what are the minimum requirements for bacterial growth?

Answer 55

Water: Essential for all cellular functions.
Carbon: Essential for building cell structures.
Nitrogen: Needed for protein synthesis, DNA, RNA, ATP synthesis.
sulfur: for the synthesis of specific amino acids and vitamins.
Phosphorus: for the synthesis of nucleic acids, ATP, phospholipids.
inorganic ions- to facilitate enzymatic catalysts and to maintain chemical gradient.

Question 56

what are the phases in bacterial growth?

Answer 56

1. Lag Phase:
   Bacteria adapt to their new environment and not yet divided.
   Synthesize enzymes and molecules needed for growth.
   No significant increase in cell number.
   minutes to hours.
2. Log (Exponential) Phase:
   Rapid cell division and growth.
   Population doubles at regular intervals.
   Optimal conditions for growth.
   most antibiotics have an impact on this phase.
3. Stationary Phase:
   Growth rate slows down as nutrients deplete and waste accumulates.
   Number of dividing cells equals the number of dying cells.
   Population stabilizes.
4. Death Phase:
   Nutrient depletion and toxic waste buildup lead to cell death.
   more die than replaced.
   Population declines rapidly.

Question 57

what are the 3 mechanisms via which DNA can be exchange in a bacteria?

Answer 57

Transformation: Bacteria acquire DNA from the environment.
Transduction: DNA is transferred via a bacteriophage (virus).
Conjugation: DNA is directly transferred between bacteria.

Question 58

define exogenote

Answer 58

Exogenote is a piece of donor DNA involved in the mating of prokaryotic organisms.

Question 59

define endogenote

Answer 59

Endogenote is the original, complete genome of a bacterium before the addition of new genetic material (exogenote).

Question 60

define conjugation

Answer 60

Conjugation is a process of gene transfer from a donor to a recipien bacterial cell. genetic material is directly transferred from one bacterium to another through a physical connection called a pilus. This process often involves the transfer of plasmids and no chromosomal DNA.

Question 61

define conjugative plasmids

Answer 61

Conjugative plasmids are extrachromosomal DNA elements that carry genes necessary for their own transfer from one bacterial cell to another.
thay are usually large and found at 1-3 copies per cell.
They are also called F plasmids. These plasmids encode proteins that form a pilus, a structure that allows bacteria to connect and transfer single strand from of the F plasmid (with genetic material). the process is completed with the synthesis of complementary strands in both donor and recipient.
they can carry genes for antibiotic resistance, virulence factors, and other traits.

Question 62

define F+ cells and F- cells

Answer 62

F+ cells: These bacterial cells possess a fertility (F) plasmid, which is a circular extrachromosomal DNA molecule. The F plasmid carries genes necessary for the formation of a pilus, a structure used for conjugation. F+ cells can act as donors of genetic material during conjugation.

F- cells: These bacterial cells lack the F plasmid. They are recipients of genetic material during conjugation from F+ cells. After successful conjugation, an F- cell can become an F+ cell.

Question 63

define non conjugative plasmids (R plasmids)

Answer 63

Non-conjugative plasmids are extrachromosomal DNA elements that lack the necessary genes to initiate conjugation. They cannot independently transfer themselves from one bacterial cell to another. These plasmids often rely on conjugative plasmids to be mobilized and transferred during conjugation.
they are small and present in many (10-60) copies per cell.
they carry genes that encode common pili, adhesins, toxins or antimicrobial resistance.

Question 64

define transduction in bacteria

Answer 64

Transduction is a process of gene transfer where genetic material (DNA) is transferred from one bacterium to another by a bacteriophage (a virus that infects bacteria). This occurs when a bacteriophage packages bacterial DNA instead of its own genetic material and then transfers it to another bacterial cell during infection.

Question 65

define bacteriophage

Answer 65

A bacteriophage, often shortened to phage, is a virus that infects bacteria. The term literally means “bacteria eater,” reflecting their ability to destroy bacterial cells. They are extremely common and diverse, found wherever bacteria exist.

Question 66

define transformation in bacteria

Answer 66

Transformation is a process where bacteria take up free DNA (fragment or entire plasmid) from their surroundings and incorporate it into their own genome. This DNA can come from other bacteria that have lysed (broken open) or from the environment.
it is critical survival mechanism. fragments od DNA may act as a “danger sign”.

Question 67

compare between Transformation(1), Transduction (2) and Conjugation (3) in bacteria

Answer 67

Definition
1. Uptake of naked DNA from environment
2. Transfer of DNA by a bacteriophage
3. Transfer of DNA through cell-to-cell contact

Mediated by
1. No intermediary
2. Bacteriophage
3.Pilus

type of DNA transferred
1. any type
2.Any type
3. Plasmid or chromosomal DNA

Cell-to-cell contact
1.No
2.No
3.Yes

Efficiency
1.Low
2.Low to moderate
3.High

type of cell involved
1.prokaryotic or eukaryotic
2. Prokaryotic
3. Prokaryotic

Question 68

what is the size of viruses?

Answer 68

20-300 nm

Question 69

what is the genom of a virus?

Answer 69

can be RNA or DNA

Question 70

define capsid

Answer 70

A capsid is the protein shell that surrounds and protects a virus’s genetic material. It’s composed of protein subunits called capsomeres. The shape of the capsid can be helical, icosahedral, or complex, depending on the virus.

Question 71

define enveloped virus

Answer 71

An enveloped virus is a virus that has an outer lipid layer, called an envelope, surrounding its protein capsid. This envelope is derived from the host cell’s membrane and contains viral proteins embedded in it. Enveloped viruses are generally more fragile and susceptible to environmental factors like heat, drying, and detergents.

Question 72

defune naked virus

Answer 72

A naked virus lacks an envelope and is composed solely of a protein capsid surrounding its genetic material.

Question 73

define obligate intracelluar parasites

Answer 73

Obligate intracellular parasites are organisms that absolutely require a host cell to survive and reproduce. They cannot independently carry out these functions outside of a living cell.
Viruses are the most well-known examples of obligate intracellular parasites.

Question 74

define virion

Answer 74

A virion is a complete, fully formed virus particle, consisting of the viral genome surrounded by a protein coat called a capsid, and sometimes an outer envelope. It is the extracellular, infectious form of a virus.

Question 75

what are the components of a virus?

Answer 75

Nucleic acid: This is the genetic material of the virus, which can be either DNA or RNA. It carries the information needed for the virus to replicate.

Capsid: A protein coat that surrounds and protects the nucleic acid. It is made up of subunits called capsomeres.

Some viruses also have an Envelope: A lipid-based outer layer acquired from the host cell during the virus’s release. This envelope contains viral proteins embedded in it.

Question 76

are the nucleic acids single stranded or double stranded? circular ot linear?

Answer 76

both and both! Viruses can have a variety of nucleic acid structures:

Strandedness:
Single-stranded (ss): Only one strand of nucleic acid is present.
Double-stranded (ds): Two complementary strands of nucleic acid are present.

Shape:
Linear: The nucleic acid molecule is a straight chain.
Circular: The nucleic acid molecule is closed into a loop.

Question 77

define positive ssRNA

Answer 77

Positive-sense single-stranded RNA (ssRNA) viruses have a genome that can directly act as messenger RNA (mRNA) upon infection of a host cell. This means the viral RNA can be immediately translated into viral proteins without the need for further processing.
Thus infectious without additional modifications.

Question 78

define positive ssRNA

Answer 78

Positive-sense single-stranded RNA (ssRNA) viruses have a genome that can directly act as messenger RNA (mRNA) upon infection of a host cell. This means the viral RNA can be immediately translated into viral proteins without the need for further processing.
Thus infectious without additional modifications.

Question 79

define negatice ssRNA

Answer 79

Negative-sense single-stranded RNA (ssRNA) viruses have a genome that is complementary to the mRNA. This means the viral RNA cannot be directly translated into proteins. Instead, the virus must first produce a positive-sense RNA copy (which acts as mRNA) using an enzyme called RNA-dependent RNA polymerase (RdRp). Only then can viral proteins be synthesized.

Question 80

define capsomers

Answer 80

Capsomeres are the individual protein subunits that make up the capsid.

Question 81

define self - assembly

Answer 81

Self-assembly is a process where components spontaneously organize themselves into a structured pattern without external direction.

Question 82

what are the shapes of capsids?

Answer 82

Helical

Icosahedral

Complex: Some viruses have more intricate structures that don’t fit into the helical or icosahedral categories. Bacteriophages, for example, often have complex structures with a head (icosahedral) and a tail (helical).

Question 83

where does the envelope of a virus come from?

Answer 83

previous host

Question 84

define spikes

Answer 84

spikes refer to protein structures protruding from the surface of a virus. They are often glycoproteins, meaning they have carbohydrate molecules attached.

These spikes serve several crucial functions:
Attachment: They bind to specific receptors on host cells, initiating the infection process.
Fusion: In some viruses, they facilitate the merging of the viral envelope with the host cell membrane.
Antigenicity: They are often the targets of the host immune system, stimulating the production of antibodies.

Question 85

how is the enveloped virus better than naked?

Answer 85

Stealth: The envelope can help the virus evade the host immune system by mimicking the host cell’s membrane.
Fusion: The envelope often contains proteins that facilitate fusion with the host cell membrane, aiding in viral entry.

Question 86

what is the difference between infection with virulent and temperate phages?

Answer 86

Virulent Phages
Lytic cycle only: These phages follow a reproductive cycle that always ends in the lysis (bursting) of the host bacterial cell, releasing new phage particles.
Rapid replication: They quickly replicate their genetic material and produce new phage components, leading to the destruction of the host cell.
No integration: Virulent phages do not integrate their genetic material into the host bacterial chromosome.

Temperate Phages
Lytic and lysogenic cycles: They can follow either a lytic cycle (like virulent phages) or a lysogenic cycle.
Lysogeny: In the lysogenic cycle, the phage’s genetic material integrates into the host bacterial chromosome, becoming a prophage. The bacterium carrying the prophage is called a lysogen.
Prophage: The integrated phage DNA is replicated along with the bacterial chromosome and passed on to daughter cells.
Induction: Under certain conditions, the prophage can be excised from the bacterial chromosome and enter the lytic cycle, leading to the production of new phage particles and lysis of the host cell.

Question 87

define proghape

Answer 87

A prophage is the genetic material of a bacteriophage (virus that infects bacteria) integrated into the host bacterium’s genome. In this state, the phage DNA is replicated along with the bacterial DNA during cell division, without causing cell lysis (bursting).

Question 88

define dormant form

Answer 88

Dormant means inactive or temporarily at rest. It implies a state of suspended activity or growth, but with the potential to resume normal functions under suitable conditions.
In this phase, the virus is not actively replicating and producing new virus particles.

Question 89

define lytic replication. what are the steps in lytic replication?

Answer 89

The lytic cycle is a viral replication process that culminates in the destruction of the host cell.

It consists of the following steps:
-Attachment: The virus binds (chemical interaction - weak bonds) to specific receptors on the surface of the host cell wall (complementary to a specific tail fibers of the virus)
-Penetration: The virus injecting its genetic material. lysozyme helps to weaken the cell wall. the capsid stays outside.
-Biosynthesis: The virus takes over the host cell’s machinery to replicate its genetic material and produce viral proteins. the host’s proteins and nucleic acids synthesis is switched off. the host is supplying everything.
-Maturation: New mature viral particles are assembled within the host cell.
Lysis: The host cell bursts, releasing new virus particles that can infect other cells.

Question 90

define eclipse period

Answer 90

eclipse period refers to the time interval between the entry of the virus into a host cell and the appearance of new, infectious virus particles within that cell.
it’s the phase where the virus is undergoing internal processes like replication, assembly, and maturation without producing any new, fully formed virus particles.

Question 91

define lysogenic replication. whar are its steps?

Answer 91

Lysogenic replication is a type of viral replication cycle where the viral genome integrates into the host cell’s genome and remains dormant for a period of time. This integrated viral genome is called a prophage.
Lysogenic replication allows viruses to establish a persistent infection without immediately killing the host cell.

Integration: The viral genome becomes part of the host cell’s DNA.
Dormancy: The virus remains inactive (prophage) for an extended period.
Replication: The prophage is replicated along with the host cell’s DNA during cell division.
Induction: Under certain conditions, the prophage can be excised from the host genome and enter the lytic cycle, leading to the production of new virus particles and the destruction of the host cell.

Question 92

do all viruses can infect any cell? why?

Answer 92

no!
the attachment involves specific receptors on the host cell surface.

Question 93

describe the replication of animal viruses

Answer 93

1.Attachment:
The virus binds to specific receptors on the host cell’s surface (spikes). they may even overcome the host’s defense. This specificity determines the host range of the virus.
2. Penetration:
The virus enters the host cell through either:
Endocytosis/recceptor Mediated: The entire virus is engulfed by the host cell.
Fusion: The viral envelope merges with the host cell membrane.
3. Genome Replication:
The viral genome is replicated using the host cell’s machinery.
The number of copies produced depends on the virus type.
4. Assembly:
Viral components (nucleic acid, capsid proteins, and envelope proteins if present) assemble to form new virions.
5. Release:
New virions are released from the host cell through:
Lysis: The host cell bursts, releasing the virus.
Budding: The virus acquires an envelope from the host cell membrane as it exits.

Question 94

define budding

Answer 94

the release of enveloped viruses from a host cell.
Unlike naked viruses which are released by cell lysis (bursting), enveloped viruses acquire their lipid envelope from the host cell membrane during their exit process.

Question 95

define latency

Answer 95

In microbiology, latency refers to the period when a virus exists in a dormant state within a host cell. This means the virus is not actively replicating or producing new virus particles.
latency allows a virus to persist within a host without causing immediate harm, while maintaining the potential to reactivate and cause disease under certain conditions.

Question 96

define HIV

Answer 96

HIV stands for Human Immunodeficiency Virus. It is a retrovirus that gradually destroys the immune system, leading to Acquired Immunodeficiency Syndrome (AIDS).
it’s RNA virus, retrovirus, +ssRNA, enveloped.
Its genome encodes the enzyme reverse transcriptase.

Question 97

define reverse transcriptase

Answer 97

Reverse transcriptase is an enzyme that catalyzes the process of reverse transcription, which is the conversion of RNA into DNA. This is the opposite of the usual DNA to RNA transcription process.
Reverse transcriptase is found in retroviruses like HIV and is crucial for their replication cycle.

Question 98

define retrovirus

Answer 98

A retrovirus is a type of virus that uses RNA as its genetic material instead of DNA.
What sets retroviruses apart is their unique replication process. They use an enzyme called reverse transcriptase to convert their RNA genome into DNA, which is then integrated into the host cell’s DNA. This allows the virus to replicate and produce new virus particles.

Question 99

define provirus

Answer 99

A provirus is the integrated form of a viral genome into the host cell’s DNA. This means the viral genetic material has become a stable part of the host’s genetic makeup.

Key characteristic: A provirus is dormant, meaning it is not actively producing new virus particles.
Replication: The provirus is replicated along with the host cell’s DNA during cell division.
Reactivation: Under certain conditions, the provirus can be excised from the host genome and enter the lytic cycle, leading to the production of new virus particles.

Question 100

define provirus

Answer 100

A provirus is the integrated form of a viral genome into the host cell’s DNA. This means the viral genetic material has become a stable part of the host’s genetic makeup.

Key characteristic: A provirus is dormant, meaning it is not actively producing new virus particles.
Replication: The provirus is replicated along with the host cell’s DNA during cell division.
Reactivation: Under certain conditions, the provirus can be excised from the host genome and enter the lytic cycle, leading to the production of new virus particles.

Question 101

how does HIV work?

Answer 101

Infection: HIV primarily targets and infects CD4+ T cells, which are crucial for immune function.

Replication: Once inside the CD4+ T cell, HIV replicates and produces new virus particles.

Immune system damage: The increasing number of infected and destroyed CD4+ T cells weakens the immune system.

Opportunistic infections: With a compromised immune system, individuals become susceptible to various opportunistic infections.

Question 102

what’s the HIV structure?

Answer 102

1.Viral Genome:
diploid. Two identical copies of single-stranded RNA: These carry the genetic information for the virus.
the 3 major genes are gag(capsid), pol (reverse transcriptase) and env (spikes) that encode retrovirus proteins. also encodes for six regulatory genes.

2.nucleocaspid:
surround the viral genome.
Matrix: A protein layer located beneath the envelope.
Capsid: A conical protein shell surrounding the viral core.
Core: Contains the viral RNA genome, enzymes (reverse transcriptase, integrase, and protease), and other proteins.

3. Envelope: Derived from the host cell membrane, containing lipoproteins.containing viral proteins embedded in it, like spikes that bind to the CD4 receptor on host cells, and pedicles that enolved in fusion of the viral envelope with the host cell membrane.

Question 103

define integrase

Answer 103

an enzyme produced by retroviruses, such as HIV, that is responsible for integrating the viral DNA into the host cell’s genome.
integrase acts like molecular scissors and glue, cutting open the host DNA and inserting the viral DNA into it.

Question 104

define protease

Answer 104

A protease is an enzyme that breaks down proteins into smaller polypeptides or amino acids. It does this by cleaving the peptide bonds between amino acids.

Some viruses, like HIV, produce proteases that are essential for processing viral proteins into their final functional forms. These proteases are targets for antiviral drugs.

Question 105

define cDNA

Answer 105

cDNA stands for complementary DNA. It is a DNA molecule that is synthesized from a messenger RNA (mRNA) template through the process of reverse transcription.

Question 106

what are the WBC (CD4+ T) levels of HIV patient?

Answer 106

Early infection: CD4+ T cell count may drop rapidly but often remains within the normal range initially.

Progression: As HIV continues to replicate, CD4+ T cell count steadily declines.

AIDS: CD4+ T cell count drops below 200 cells per microliter. This level significantly compromises the immune system, making individuals susceptible to opportunistic infections.