life science notes

VIRUS REPRODUCTION

Two Types of Virus Reproduction

  • Lytic Cycle

    • Virus attaches to host cell.

    • Virus injects DNA/RNA into cell.

    • Host cell machinery produces virus components.

    • Host cell assembles viruses.

    • Virus bursts out of cell, causing host cell to die (lysis).

  • Lysogenic Cycle

    • Virus DNA merges into the cell's DNA to be stored.

    • Once favorable conditions return, virus will enter lytic cycle.

SPECIFIC IMMUNE RESPONSE

Stages of Immune Response to Viral Infection

  1. Viral Infection

    • Note: In bacterial infection, the same process would occur except no killer-T cells are released.

  2. Alerting Immune Cells

    • Alerts CD4 T-cells.

    • CD4 cells alert killer-T cells and B-lymphocytes.

  3. Killer-T Cells

    • Release to destroy infected cells, causing host cells to die (lysis).

  4. B-Lymphocytes

    • Plasma cells create antibodies.

    • Antibodies clump pathogens and destroy them.

    • Antibodies also used to "flag" to identify pathogens.

    • Creation of memory cells for faster immune response in future infections.

CHARACTERISTICS OF BACTERIA

Cell Structure of Bacteria

  • Glycocalyx

  • Ribosome

  • Flagellum

  • Pilus

  • Chromatin

  • Cell Wall

  • Cell Membrane

Types of Bacteria

  • Shape

    • Coccus (sphere)

    • Vibrio (comma)

    • Bacillus (rod)

    • Spirillum (spiral)

Characteristics

  • Prokaryotic

    • Does not have a nucleus or organelles

    • Unicellular

    • Reproduce via binary fission

    • Live everywhere in the biosphere

    • Some are pathogens.

    • Habitat: Found in soil, water, and inside organisms.

Importance of Bacteria

  • Decomposers: Break down organic compounds and return nutrients to the soil.

  • Nitrogen-fixing in plants.

Diseases caused by Bacteria

  • Tuberculosis (TB)

  • Tetanus

  • Meningitis

STRUCTURE OF VIRUSES

Virus Characteristics

  • Acellular

    • Does not carry out the 7 life functions.

    • No organelles, classified as non-living.

Classification of Viruses

  1. Shape

  2. Presence or absence of envelope

  3. Host type

  4. Mode of transmission

  5. Disease caused

  6. Type of nucleic acid (RNA or DNA)

  7. Reproduces via lytic (short) or lysogenic (long-term) cycle.

Importance of Viruses

  • Control populations via death from diseases.

  • Examples include HIV, flu, measles, and rubella.

PROTISTA: EUKARYOTIC ORGANISMS

Nutritional and Reproductive Mechanisms

  • Pseudopodia and Phagocytosis

    • Pseudopodia form when a protist changes the consistency of its cytoplasm between a gel and a liquid.

    • Liquid cytoplasm forms extensions to move or surround prey.

    • When surrounding prey from both sides, phagocytosis occurs whereby the pseudopodia engulf the food, creating a food vacuole for digestion.

Characteristics of Protista

  • Eukaryotic

    • True nucleus and organelles

    • Can be animal-like, plant-like, or fungi-like.

Importance of Protista

  • Fundamental link in the food chain.

  • Assist in cattle digestion.

Diseases caused by Protista

  • Malaria (caused by Plasmodium) which leads to bursting of red blood corpuscles.

NON-SPECIFIC IMMUNE RESPONSES

Two Lines of Defense

1st Line of Defense (Pathogen Has Not Broken Through Skin)

  • Skin

  • Mucous membranes

  • Antimicrobial proteins found in:

    1. Tears

    2. Sweat

    3. Saliva

2nd Line of Defense (Pathogen Has Broken Through Skin)

  • Inflammatory Response

    • Histamines released cause swelling and raised temperatures.

    • Phagocytes engulf pathogens.

  • Antimicrobial Proteins

    • Cause the cell wall or membrane of pathogens to burst.

Phagocytosis Process

  1. Phagocyte engulfs the pathogen.

  2. Lysosomes containing digestive enzymes destroy the pathogen.

  3. Waste materials are discharged via exocytosis.