General Principles Week 6 Flashcards
(76 cards)
Topic 1 – Prokaryotes (Bacteria)
TLO 1.1 Differences in cell structure between prokaryotic and eukaryotic cells
Prokaryotic and eukaryotic cells differ significantly in their structure
- Nucleus: Prokaryotes lack a membrane-bound nucleus, while eukaryotes have a distinct nucleus enclosed by a nuclear membrane.
- Organelles: Prokaryotes have no membrane-bound organelles, whereas eukaryotes possess various membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.
- DNA structure: Prokaryotic DNA is typically circular and located in the nucleoid region of the cytoplasm. Eukaryotic DNA is linear and contained within the nucleus.
- Size: Prokaryotic cells are generally smaller, ranging from 0.1 to 5.0 μm in diameter, while eukaryotic cells are typically 10-100 μm in diameter.
- Ribosomes: Prokaryotes have smaller 70S ribosomes, while eukaryotes have larger 80S ribosomes.
TLO 1.2 Structure and function of bacterial components
Bacterial cells consist of several key components:
- Cell Wall: Provides structural support and protection. It’s composed of peptidoglycan.
- Plasma Membrane: Controls what enters and exits the cell.
- Cytoplasm: Supports and protects cell organelles and contains nutrients.
- Nucleoid: Region where the bacterial chromosome (DNA) is located.
- Plasmid: Extra chromosomal DNA that can confer antibiotic resistance.
- Ribosomes: Responsible for protein synthesis.
- Inclusion/Storage Granules: Store nutrients like sugars and fats.
- Flagella: Aid in bacterial locomotion.
- Pili: Help bacteria attach to surfaces and other cells.
TLO 1.3 Difference between gram-positive and gram-negative bacteria
The main differences between gram-positive and gram-negative bacteria are:
- Cell Wall Structure: Gram-positive bacteria have a thick peptidoglycan layer, while gram-negative bacteria have a thin peptidoglycan layer with an outer membrane.
- Staining: Gram-positive bacteria retain crystal violet stain and appear purple, while gram-negative bacteria lose the stain and appear red.
- Antibiotic Resistance: Gram-negative bacteria are generally more resistant to antibodies due to their impenetrable cell wall.
- Toxin Production: Gram-positive bacteria typically produce exotoxins, while gram-negative bacteria produce endotoxins.
Feature Endotoxins Exotoxins
Origin Part of the outer membrane of Gram-negative bacteria Secreted by bacteria (both Gram-positive and Gram-negative)
Release Released when bacteria die Actively secreted by living bacteria
Potency Generally less potent Highly potent
Effects Can cause fever, inflammation, and septic shock Can damage specific tissues and organs
TLO 1.4 Bacterial growth and division
Bacteria grow and divide through a process called binary fission:
- DNA Replication: The bacterial chromosome is replicated.
- Chromosome Segregation: The replicated chromosomes are separated.
- Septum Formation: A cell wall forms between the two chromosomes, dividing the cell.
- Cell Separation: The two daughter cells split apart.
The time taken for a bacterial population to double is called the generation time, which varies among species but is typically around 20 minutes for many medically significant bacteria.
Topic 2 – Acellular Microbes (Viruses)
TLO 2.1 Structure of the virus
Viruses consist of:
- Genetic Material: Either DNA or RNA, but not both.
- Capsid: A protein coat that protects the genetic material.
- Envelope: Some viruses have an additional lipid membrane surrounding the capsid.
Viruses can have various shapes, including icosahedral, helical, or complex structures.
icosahedral - capsid (capsomere) + genome (cubic symmerty) Example herpesvirus
helical - capsid (capsomere) + genome (helical shape) Example Influenza/Rabies virus
complex structures - capsid (capsomere) + genome (helical shape) example bacteriophage - Poxvirus
Another example - - capsid (capsomere) + genome (circular shape + envelope (Lipid bilayer + gycoprotein)
TLO 2.2 Characteristics of viruses
Key characteristics of viruses include:
- Size: Extremely small, ranging from 20 to 300 nanometers.
- Acellular: Viruses are not cells and lack cellular organelles.
- Obligate Intracellular Parasites: They can only replicate inside host cells.
- Specific Host Range: Each virus can infect only specific types of cells or organisms.
- Genetic Material: Contains either DNA or RNA, but not both.
Feature Bacteria Viruses
Size Larger, usually 1-5 micrometers Smaller, typically 20-300 nanometers
Structure Single-celled organisms with a simple structure Consist of genetic material in a protein coat
Living Status Living organisms Not considered living, need a host to replicate
Reproduction Reproduce on their own through binary fission Require a host cell to replicate
Treatment Treated with antibiotics Treated with antiviral drugs or vaccines
TLO 2.3 Viral growth cycle and replication
The viral replication cycle consists of seven stages:
- Attachment: The virus binds to specific receptors on the host cell.
- Entry: The virus enters the host cell.
- Uncoating: The viral genetic material is released inside the host cell.
- Replication: The viral genome is replicated using host cell machinery.
- Assembly: New viral particles are assembled.
- Maturation: The newly formed viruses undergo final changes to become infectious.
- Release: The new viruses are released from the host cell.
Viruses can undergo either a lytic cycle (where the host cell is destroyed) or a lysogenic cycle (where the viral genome integrates into the host genome).
Stages
Attachment Virus attaches to the host cell surface
Entry Virus enters the host cell, often through endocytosis
Uncoating Viral genetic material is released inside the host cell
Replication Viral genetic material is replicated by the host cell
Assembly New viral particles are assembled from the replicated material
Maturation Viral particles undergo modifications to become fully infectious
Release New viruses are released from the host cell, often causing cell lysis
Topic 3 – Eukaryotic Pathogens (Fungi and Parasites)
TLO 3.1 Structure of eukaryotic microbes (fungi and parasites)
Eukaryotic microbes have a more complex structure compared to prokaryotes:
- Nucleus: Contains the genetic material enclosed by a nuclear membrane.
- Membrane-bound Organelles: Include mitochondria, endoplasmic reticulum, and Golgi apparatus.
- Cell Wall: Fungi have a cell wall made of chitin.
- Cytoskeleton: Provides structure and enables movement.
TLO 3.2 Growth and replication of eukaryotic pathogens
Eukaryotic pathogens grow and replicate through various methods:
- Fungi: Can reproduce sexually or asexually, often through spore formation.
- Parasites: May have complex life cycles involving multiple hosts and stages.
Fungi
- Absorb nutrients from the environment, often through decomposing organic matter
- Reproduce by spore formation (both sexual and asexual reproduction)
Parasites
- Live in or on a host organism, deriving nutrients from the host
- Reproduce through various methods, including binary fission, multiple fission, and sexual reproduction
TLO 3.3 How eukaryotic microbes cause disease and associated challenges
Eukaryotic microbes can cause disease through various mechanisms:
- Tissue Invasion: Direct damage to host tissues.
- Toxin Production: Release of harmful substances.
- Immune Evasion: Ability to avoid or suppress host immune responses.
TLO 4.1 Normal flora (microbiota) associated with body regions
Normal flora, or microbiota, are microorganisms that naturally inhabit various body regions.
They play crucial roles in maintaining health, including:
- Skin: Primarily bacteria that help prevent colonization by harmful microbes.
- Gastrointestinal Tract: Diverse community of bacteria that aid in digestion and immune function.
- Respiratory Tract: Bacteria that help prevent colonization by pathogens.
- Urogenital Tract: Bacteria that maintain pH and prevent infections.
Sometimes Germs Really Upstage
Skin: Staphylococcus epidermidis, Propionibacterium
Gastrointestinal Tract: Gut bacteria (Escherichia coli, Bacteroides)
Respiratory Tract: Respiratory bacteria (Streptococcus pneumoniae, Haemophilus influenzae)
Urogenital Tract: Urinary/Lactobacillus, Candida
Challenges in treating eukaryotic pathogens include:
- Similarity to Host Cells: Makes it difficult to target pathogens without harming host cells.
- Complex Life Cycles: Especially for parasites, making them hard to eliminate completely.
- Drug Resistance: Some fungi and parasites can develop resistance to treatments.
TLO 4.2 Types of symbiotic relationships and examples
Symbiotic relationships include:
- Mutualism: Both organisms benefit (e.g., gut bacteria aiding in digestion).
- Commensalism: One organism benefits while the other is unaffected (e.g., some skin bacteria).
- Parasitism: One organism benefits at the expense of the other (e.g., intestinal worms).
Mutualism Both organisms benefit Gut bacteria and humans (digestive health)
Commensalism One organism benefits, the other is unaffected Staphylococcus on the skin
Parasitism One organism benefits, the other is harmed Malaria parasite in humans
TLO 4.3 Process of infection (bacterial, viral, fungal, helminthic, parasitic)
The process of infection varies slightly depending on the type of pathogen, but generally follows these steps:
- Entry
- Adherence
- Invasion
- Multiplication
- Spread
- Tissue Damage
- Shedding:
Entry All Insects Must Scatter To Survive
TLO 4.3 Process of infection (bacterial, viral, fungal, helminthic, parasitic)
The process of infection varies slightly depending on the type of pathogen, but generally follows these steps:
- Entry: Pathogens enter the host through various routes:
* Bacterial: Through breaks in skin, mucous membranes, or ingestion
* Viral: Similar to bacterial, often through respiratory or mucosal routes
* Fungal: Often through inhalation of spores or skin contact
* Helminthic and Parasitic: Usually through ingestion or skin penetration - Adherence: Pathogens attach to host cells:
* Bacterial: Using pili or adhesins
* Viral: Via specific receptor binding
* Fungal: Through adhesins
* Helminthic and Parasitic: Using hooks, suckers, or other specialized structures - Invasion: Pathogens penetrate host tissues:
* Bacterial: Some remain extracellular, others enter cells
* Viral: Enter host cells for replication
* Fungal: Can invade tissues or remain superficial
* Helminthic and Parasitic: Often migrate through tissues to specific organs - Multiplication:
* Bacterial: Divide by binary fission
* Viral: Replicate using host cell machinery
* Fungal: Grow by extending hyphae or budding
* Helminthic and Parasitic: Often involve complex life cycles with multiple stages - Spread:
* Can occur locally or systemically through blood or lymph - Tissue Damage:
* Direct damage from pathogen activity
* Indirect damage from host immune response - Shedding:
* Release of pathogens from the host to potentially infect others
Topic 5 – Antibiotics
TLO 5.1 Difference between narrow and broad-spectrum antibiotics
- Narrow Spectrum Antibiotics:
- Target specific types of bacteria
- Examples: Penicillin G (effective against gram-positive bacteria), Vancomycin (targets gram-positive bacteria)
- Advantages: Less likely to cause antibiotic resistance, fewer side effects
- Disadvantages: Require accurate diagnosis before prescription
Topic 5 – Antibiotics
TLO 5.1 Difference between narrow and broad-spectrum antibiotics
- Broad Spectrum Antibiotics:
- Effective against a wide range of bacterial types
- Examples: Tetracyclines, Chloramphenicol
- Advantages: Can be used empirically before specific pathogen identification
- Disadvantages: Higher risk of antibiotic resistance, more likely to disrupt normal
Type of Antibiotic Description Examples Pros Cons
Narrow-Spectrum Effective against a specific group of bacteria Penicillin, Erythromycin - Targets specific bacteria effectively - Limited use against a wide range of infections
- Reduces risk of antibiotic resistance - May require precise identification of pathogen
Broad-Spectrum Effective against a wide range of bacteria Tetracycline, Ciprofloxacin - Can treat multiple types of infections - Higher risk of antibiotic resistance
- Useful in situations where the pathogen is unknown - Can disrupt normal flora, leading to side effects like diarrhea
TLO 5.2 Families of antibiotics and their modes of action
- Beta-lactams
- Aminoglycosides
- Tetracyclines
- Macrolides
- Fluoroquinolones
- Sulfonamides
- Glycopeptides
TLO 5.2 Families of antibiotics and their modes of action
- Beta-lactams (e.g., penicillins, cephalosporins):
* Mode of action: Inhibit cell wall synthesis
* Target: Peptidoglycan layer of bacterial cell wall - Aminoglycosides (e.g., streptomycin, gentamicin):
* Mode of action: Inhibit protein synthesis
* Target: 30S ribosomal subunit - Tetracyclines:
* Mode of action: Inhibit protein synthesis
* Target: 30S ribosomal subunit - Macrolides (e.g., erythromycin):
* Mode of action: Inhibit protein synthesis
* Target: 50S ribosomal subunit - Fluoroquinolones (e.g., ciprofloxacin):
* Mode of action: Inhibit DNA replication
* Target: DNA gyrase and topoisomerase IV - Sulfonamides:
* Mode of action: Inhibit folic acid synthesis
* Target: Enzyme involved in folic acid production - Glycopeptides (e.g., vancomycin):
* Mode of action: Inhibit cell wall synthesis
* Target: Peptidoglycan precursors
TLO 5.3 Significance of bacteria producing beta-lactamase
The production of beta-lactamase by bacteria is significant for several reasons:
- Antibiotic Resistance: Beta-lactamase enzymes can hydrolyze the beta-lactam ring of many commonly used antibiotics, rendering them ineffective.
- Treatment Failure: Infections caused by beta-lactamase-producing bacteria may not respond to first-line antibiotic treatments, leading to prolonged illness and increased healthcare costs.
- Spread of Resistance: Genes encoding beta-lactamase can be transferred between bacteria, potentially leading to widespread antibiotic resistance.
- Need for New Antibiotics: The prevalence of beta-lactamase-producing bacteria has driven the development of new antibiotics and beta-lactamase inhibitors.
- Clinical Implications: Healthcare providers must consider the possibility of beta-lactamase production when selecting antibiotics, often necessitating the use of broader-spectrum or combination therapies.
- Public Health Concern: The spread of beta-lactamase-producing bacteria, especially in healthcare settings, poses a significant challenge to infection control and patient safety.
TLO 5.3 Significance of bacteria producing beta-lactamase
The production of beta-lactamase by bacteria is significant for several reasons:
- Antibiotic Resistance
- Treatment Failure
- Spread of Resistance
- Need for New Antibiotics
- Clinical Implications
- Public Health Concern
Clostridium difficile is a gram-positive bacteria forming one of the large intestine microbiota. However,it can lead to a disease process after antibiotics use especially in elderly. This is mainly due to:
a. Exogenous infection
b. Antibiotics help Clostridia to grow and multiply
c. Mutualistic relationship between the antibiotics and Clostridia difficile bacteria
d. Antibiotic treatment affect the normal population of large intestinal microbiota except for Clostridia due to its ability to form endospores
Antibiotic treatment affect the normal population of large intestinal microbiota except for Clostridia due to its ability to form endospores
The proteins on the external surface of viruses serve several important functions. Regarding these proteins, which one of the following statements is most accurate?
a. They are the antigens against which neutralizing antibodies are formed.
b. They are the proteins that regulate viral transcription.
c. They are the polymerases that synthesize viral messenger RNA.
d. They are the proteases that degrade cellular proteins leading to cell death.
a.
They are the antigens against which neutralizing antibodies are formed.
Which of the following is a dimorphic fungi?
a. Microsporum
b. Blastomyces dermatitidis
c. Candida albicans
d. Trichophyton
b. Blastomyces dermatitidis
