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Questions and Answers
What distinguishes the lytic cycle from the lysogenic cycle in viruses?
What distinguishes the lytic cycle from the lysogenic cycle in viruses?
Which of the following best characterizes a retrovirus like HIV?
Which of the following best characterizes a retrovirus like HIV?
What is a primary characteristic of the microbiome that impacts environmental health?
What is a primary characteristic of the microbiome that impacts environmental health?
Which of the following is NOT a method used by bacteria to obtain nutrients?
Which of the following is NOT a method used by bacteria to obtain nutrients?
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How do vaccines contribute to herd immunity?
How do vaccines contribute to herd immunity?
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Which type of bacterium can survive in harsh environments by forming endospores?
Which type of bacterium can survive in harsh environments by forming endospores?
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Which of the following best defines Koch's Postulates?
Which of the following best defines Koch's Postulates?
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What role do natural killer cells play in the body's defenses?
What role do natural killer cells play in the body's defenses?
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Flashcards
Virus Structure
Virus Structure
A virus is a non-living infectious agent that consists of genetic material (DNA or RNA) enclosed in a protein coat called a capsid. Some viruses may also have an envelope surrounding the capsid.
Lytic Cycle
Lytic Cycle
The Lytic cycle is a rapid viral replication process that results in the destruction of the host cell. The virus enters the cell, replicates its genetic material, assembles new viruses, and ultimately bursts the cell, releasing new viral particles.
Lysogenic Cycle
Lysogenic Cycle
The Lysogenic cycle involves the integration of the viral DNA into the host cell's DNA. This integrated viral DNA is called a prophage. It can remain dormant for a long time, replicating with the host cell. Eventually, it may enter the lytic cycle.
Retrovirus
Retrovirus
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HIV Infection
HIV Infection
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Innate Immunity
Innate Immunity
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Adaptive Immunity
Adaptive Immunity
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Vaccines and Immunity
Vaccines and Immunity
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Study Notes
Viral Characteristics and Structure
- Viruses are acellular infectious agents, meaning they are not composed of cells.
- They consist of a nucleic acid core (DNA or RNA) enclosed in a protein coat (capsid).
- Some viruses have an outer envelope derived from the host cell membrane.
- Viruses lack the cellular machinery to reproduce independently.
- They replicate by hijacking the host cell's machinery.
Bacteriophage Life Cycle
Lytic Cycle
- Virus infects host cell.
- Viral DNA enters the host cell.
- Viral DNA replicates.
- Viral components assemble into new viruses.
- Host cell lyses (breaks open), releasing new viruses.
- This cycle results in the destruction of the host cell.
Lysogenic Cycle
- Virus infects host cell.
- Viral DNA integrates into the host cell's DNA (prophage).
- Viral DNA replicates along with the host cell's DNA, without destroying the host.
- Under certain conditions, the prophage can excise and enter the lytic cycle.
Lytic vs Lysogenic Cycles Comparison
- The lytic cycle results in the immediate destruction of the host cell.
- The lysogenic cycle allows the virus to replicate stealthily without immediate destruction, but the possibility exists for future lytic cycle reactivation.
Examples of Plant and Animal Viruses
- Plant viruses often cause mosaic patterns on leaves.
- Animal viruses cause a wide range of diseases, ranging from the common cold to AIDS. Examples of animal viruses include influenza, measles, and herpes.
HIV Infection
- HIV is a retrovirus, meaning its RNA is converted to DNA within the host cell.
- The enzyme reverse transcriptase catalyzes this conversion.
- HIV infects helper T-cells (CD4+ lymphocytes), crucial immune system cells.
- HIV integration of viral DNA into host DNA makes it a provirus.
- Progression to AIDS occurs when helper T-cell numbers are severely reduced, leaving the host vulnerable to opportunistic infections.
- Anti-HIV drugs target different stages of the retroviral life cycle.
Emerging Viruses
- Emerging viruses are those that appear in a population for the first time or increase in prevalence.
- Examples include SARS-CoV-2 (COVID-19), HIV, West Nile virus, Ebola, and Avian influenza.
- These viruses have the potential to cause widespread illness and health crises.
Prokaryotic Diversity and Impact
- Prokaryotes (bacteria and archaea) are incredibly diverse and ubiquitous.
- Microbiome/microbiota refers to the collection of microbes living in specific environments (e.g., gut), which are important for health.
- Prokaryotes have significant roles in the environment, like chemical recycling of nutrients.
- Some are pathogenic (disease-causing) and can cause significant issues.
Prokaryotic Domains
- Bacteria
- Unicellular organisms
- Diverse shapes (cocci, bacilli, spirochetes).
- Diverse metabolic strategies
- Archaea
- Unicellular organisms
- Unique cell walls and membrane structures.
- Diverse metabolic strategies frequently found in extreme environments.
Prokaryotic Structure, Function, and Reproduction
- Cocci: spherical bacteria
- Bacilli: rod-shaped bacteria
- Spirochetes: spiral-shaped bacteria
- Endospores: dormant structures formed by some bacteria to survive harsh conditions.
- Binary fission is the primary method of prokaryotic reproduction.
Germ Theory and Koch's Postulates
- Koch's postulates are a set of criteria to determine the cause of an infectious disease.
- This research fundamentally changed how infectious diseases are understood and controlled in modern society.
Bacterial Nutrient Acquisition
- Photoautotrophs: use light energy to convert CO2 into organic molecules
- Chemoautotrophs: use chemical energy to convert CO2 into organic molecules
- Photoheterotrophs: use light energy to obtain energy but obtain carbon from organic molecules
- Chemoheterotrophs: obtain both energy and carbon from organic molecules.
Positive and Negative Impacts of Prokaryotes
- Positive impacts: nutrient cycling, bioremediation
- Negative impacts: disease-causing bacteria, antibiotic resistance.
Bacterial Growth and Interpretation
- Petri dishes and agar are used to culture bacteria.
- Sterilization procedures prevent contamination.
- Zone inhibition: areas around antibiotic disks where bacteria do not grow demonstrate sensitivity to the antibiotic.
- Bacterial colonies are visible clusters of bacteria on a petri dish.
- Bacterial broth liquid medium for bacterial growth.
Vaccines and Herd Immunity
- Vaccines stimulate the immune system to produce immunity to a particular virus.
- Herd immunity ensures protection to the entire community
Body's Nonspecific Defenses
- External Barriers (1st line): skin, mucus, cilia, saliva, tears, stomach acid
- Internal Defenses (2nd line): phagocytes (neutrophils, macrophages), interferons, complement proteins, natural killer cells. Inflammatory response: histamine, prostaglandins
- The Lymphatic System: Network that helps filter lymph and fight infections. Lymph nodes.
Body's Specific Defenses
- The immune system is responsible for recognizing and eliminating specific invaders (antigens)
- Immune reactions include antibody production and cell-mediated attacks.
- Antigens stimulate immune responses and activate antibody production by lymphocytes
- Lymphocytes include B and T cells (Helper T cells, Cytotoxic T cells
- Active Immunity involves developing antibodies in response to an infection or vaccine.
- Passive immunity involves receiving pre-formed antibodies from another source.
- Vaccination creates an active but less intense response than the natural disease infection and induces long-term memory cells.
- RNA vaccines: newer approach that uses mRNA to instruct cells to produce viral proteins thus eliciting an immune response
- Memory cells help with immunity if exposure to the same pathogen occurs again.
Immune System Malfunctions
- Allergies: Overreaction of the immune system to harmless substances (allergens). Anaphylactic shock is a severe, potentially life-threatening allergic reaction.
- Autoimmune Diseases: The immune system attacks the body's own tissues. Examples: diabetes (Type 1), multiple sclerosis, rheumatoid arthritis, lupus.
- Immunodeficiency Diseases: These conditions impair the ability of the immune system to function properly. Examples: SCID, HIV/AIDS.
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Description
Explore the fascinating world of viruses, including their unique characteristics and structure. Dive into the life cycles of bacteriophages, learning about both the lytic and lysogenic cycles. Test your understanding of how viruses interact with host cells and replicate.
