Bio Mod 7

• Disease

  Any condition which interferes with normal functioning of the body
• Pathogen

  A disease causing agent or organism such as bacteria, viruses, fungus, protozoa, prions and macro parasites
• Types of pathogens

  • Prion
  • Virus
  • Bacteria
  • Protozoa
  • Fungi
  • Macro-parasites
• Prion

  • Abnormally folded proteins made by DNA
  • Can make other proteins abnormal
  • Small and difficult to sterilise
  • Both infectious and hereditary
• Virus

  • Package of DNA/RNA surrounded by proteins
  • Extremely small
  • Non-cellular and therefore non-living + can't grow or reproduce
  • Invades host cells → injects its genetic material into host cell → cell metabolises new viruses
  • Can only survive in live cells
  • Vaccines are effective in getting rid of viruses
• Bacteria

  • Tiny prokaryotic single cellular
  • Single strand of DNA
  • Reproduce through binary fission
  • Invade cells and form colonies that disrupt normal cell function
  • Can survive outside a host cell and in reservoirs through spores, therefore are hard to eliminate and therefore is hard to eradicated
• Protozoa

  • Single celled eukaryotic organisms
  • Free living heterotrophs (absorb nutrients from their host)
  • Form colonies that disrupt normal cell function
  • Classified by their method of locomotion: flagellates, pseudopods, ciliates, sporozoa
• Fungi

  • Simple organism that are eukaryotic - multicellular or unicellular
  • Reproduce asexually using spores
  • Similar to plants but without chlorophyll
  • Can grow on skin and mucous membrane in body
  • Contain cell walls and membrane
• Macro-parasites

  • Multicellular parasites that obtain nutrients from their host and can cause disease and weight loss
  • Act as a vector for other pathogens
  • Has cell wall and membrane
• Epidemic

  Sudden spike in the prevalence of an infectious disease in a region / community
• Pandemic

  Sudden spike in a disease across the entire world
• Enzootic

  Endemic amongst animals in a particular region
• Ebola Virus

  • Severe and fatal disease that affects humans causing severe bleeding, organ failure and can lead to death. The rapid spread was due to lack of public health services and the socioeconomic status of the country = poor hygiene practices, infrastructure and lack of research.
• Bacterial colonies

  Normally shiny with a round uniform shape
• Fungal colonies

  Normally fuzzy/fluffy or powdery in a splat like shape
• Modes of transmission of infectious diseases

  • Direct: touching, sexual contact, kissing, contact with nasal or oral secretions, biting, direct contact with any blood or other body fluids, direct contact with wounds, prenatal or perinatal transmission
  • Indirect: airborne transmission — coughing or sneezing (droplets can travel up to 8 metres through the air), touching an infected surface, contaminated food or water, infected surgical instruments
  • Vector: Ticks, fleas, mosquitoes, tapeworms
• Attenuate


  To weaken
• Lyme Disease in Cattle

  • Cattle are infected with Borrelia bacterium through transmission of bites from infected ticks
  • Cattle may develop fever, stiffness, swollen joints, lameness, and decreased milk production
  • Outbreaks have been identified in high density livestock facilities aiding transmission of infected ticks through direct contact
• Myrtle Rust disease

  Fungal disease that causes deformed leaves, defoliation, reduced fertility, stunted growth and plant death in bottlebrushes, tea trees and eucalyptus
• Myrtle Rust Fungus infection

  1. Spores land on plant stem

  2. Spores send out germ tube to find opening

  3. Fungus penetrates plant tissue to access nutrients

  4. Fungus uses nutrients to grow more fungi
• Plant response to Myrtle Rust Fungus

  1. Fungus releases effector proteins into plant cell

  2. Plant detects fungus receptors and releases defence proteins

  3. Plant kills surrounding cells to cut off nutrient supply to fungus

  4. Plant produces chitin to break fungus cell wall
• Banana Bunch Disease

  Viral disease that prevents plant producing fruit and reduces growth with emerging leaves becoming choked and bunched
• Transmission of Banana Bunch Disease

  1. Infected aphids and other insects that tap into phloem act as vectors

  2. Leaf munching insects create wound sites for virus entry

  3. Virus invades plant cells to replicate
• Skin as a physical barrier

  • Epidermis, dermis and hypodermis
  • Well supplied by blood
  • Waterproof
  • Acidic environment
  • Epidermis exfoliates
• Mucous membranes

  • Cell junctions anchor epithelial cells
  • Lined with cilia to remove particles
  • Constantly growing and moving to replace surface cells
  • Secrete protective substances like mucus, lysozyme and antibodies
• Mucus

  Produced by goblet cells, protects linings by trapping foreign substances
• Sphincters

  Help seal off compartments to reduce likelihood of pathogen invasion
• Urine

  • Contains antimicrobial peptides
  • Flushing action during urination helps kill and hinder microbes
  • Acidic pH discourages microbial growth
• Sebum and sweat

  • Waterproof and lubricate skin, hindering bacterial growth
  • Contain lysozyme that lyses bacterial cell walls
• Saliva

  • Has flushing action and contains antimicrobial molecules like IgA and AMPs
• Tears

  • Contain lysozyme, lactoferrin, lipocalin, AMPs, complement, IgA, and mucins which have antimicrobial properties
• Gastric secretions

  Stomach wall secretes highly acidic hydrochloric acid, discouraging microbial growth and survival
• Antigens

  A substance that induces the formation of antibodies, therefore stimulating an immune system response. Antigens are proteins on the surface of pathogens and are how the immune system recognises threats.
• Antibodies

  Proteins which are produced in response to the presence of an antigen in the body. Y shaped with two binding sites. Antibodies develop structures that recognise and bind to specific antigens. Can be found on the surface of Plasma B-cells or in bodily fluid. Produced from plasma B-cells when they are activated (come into contact with antigen). The formation of the antigen-antibody complex causes the deactivation of the antigen.
• Lymph

  Fluid that leaks out of capillaries into spaces between cells; circulates in the vessels of the lymphatic system.
• Lymph node

  Small structures located on lymphatic vessels where pathogens are filtered from lymph and destroyed by lymphocytes.
• Lymphatic system

  System of the body consisting of organs, vessels, nodes, and lymph that produces lymphocytes (in the bone marrow) and filters pathogens from body fluids.
• Innate immune system

  1. Physical and chemical barriers to pathogens

  2. Inflammatory response and phagocytosis by WBCs
• Inflammation

  Cell invaded by pathogen → release chemical signals (Histamines, Prostaglandins, Endogenous pyrogens) → Capillaries dilate, increase blood flow, increase permeability → Allows WBCs to move from tissue to blood (enact phagocytosis) → Increase in temperature slows pathogen reproduction
• Phagocytosis

  Defence mechanism whereby phagocytes modify their shape to engulf or enclose a non-specific antigen. The phagocyte combines with a lysosome containing digestive enzymes to break down the microbe or antigen. Phagocytes then release the decomposed matter, which is no longer toxic.