Untitled Flashcard Set

🦠 Concept 1: Pathogen Structure and Reproduction

Pathogens (S&R)

📌 Overview of Pathogens

• Pathogens = disease-causing agents

• Includes: bacteria, viruses, fungi, and other microorganisms

• Only ~1% of bacteria are harmful (pathogenic)

🧫 Bacteria

🔬 Characteristics

• Prokaryotic and unicellular

• Structures:

  • Cell wall (made of peptidoglycan)

  • Cell membrane

  • Cytoplasm

  • Nucleoid region: circular DNA + plasmids

  • Ribosomes

  • Some have capsules

  • Flagella and pili for movement

🔁 Reproduction: Binary Fission

• Asexual

• Steps:

  1. DNA is copied

  2. Cell splits into 2 identical cells

• Genetic Variation comes from:

  • Mutation

  • Conjugation – DNA transfer between bacteria

  • Transformation – Uptake of DNA from surroundings

  • Transduction – Virus transfers DNA between bacteria

🔎 Classification

• By Shape:

  • Coccus (round): ex. Streptococcus

  • Bacillus (rod-shaped): ex. E. coli

  • Spiral: ex. Treponema pallidum

• By Gram Stain:

  • Gram-positive: thick peptidoglycan → purple

  • Gram-negative: thin peptidoglycan + outer polysaccharide → red

✅ Uses of Bacteria

• Food: yogurt, cheese, pickles

• Decomposers: break down matter

• Nitrogen cycle: essential for making nitrogen usable by plants

• In humans:

  • Skin bacteria prevent infection

  • Gut bacteria help digest food

• Biotech: making insulin, antibodies, HGH, vitamins, etc.

🧬 Viruses

📌 Characteristics

• NOT living (not made of cells, no metabolism)

• Called biological entities

• Need a host cell to reproduce

• Contains DNA or RNA

• A virus that infects bacteria = bacteriophage

🧱 Structure

• Capsid: protein coat

• Nucleic acid core: either DNA or RNA

• Vary in size and shape

🧪 Uses

• Research into cancer treatments, gene therapy, and antibiotic alternatives

🔁 Reproduction Cycles

🔴 Lytic Cycle

1. Attach to host

2. Inject DNA/RNA

3. Replication + protein synthesis

4. Cell bursts (lysis) → viruses spread

🟡 Lysogenic Cycle

• Viral DNA becomes part of host genome

• Copies with the host cell

• Virus stays dormant for years (e.g., chickenpox → shingles)

🧬 Concept 2: Disease

Disease (1)

🔄 Homeostasis and Disease

• Homeostasis = stable internal conditions

• Disruption of homeostasis = disease or death

• Threats include:

  • Viruses

  • Bacteria

  • Parasites

  • Fungi

🧫 Germ Theory of Disease

🔬 Definition:

• Germ Theory: diseases are caused by microorganisms

🧪 Key Scientists:

• Louis Pasteur:

  • Chemist

  • Discovered microorganisms cause decay

  • Invented pasteurization

• Robert Koch:

  • Microbiologist

  • Created method to link specific microbes to specific diseases

🧬 Causes of Disease

1. Pathogens (viruses, bacteria, fungi)

   • Note: viruses aren’t alive; they need a host

2. Hereditary factors (genetic diseases)

3. Environmental factors

   • Toxic substances

   • Poor nutrition

   • Unhealthy habits

   • Mutagen exposure

4. Gene mutations → uncontrolled cell growth = cancer

🧪 Why Bacteria and Viruses Are Dangerous

• Thrive in many environments

• Invisible to the naked eye

• Reproduce rapidly

  • Fast reproduction = fast evolution = hard to fight

🦠 Bacterial Diseases

• Mechanisms:

  1. Invade body

  2. Challenge immune system

  3. Use host cells for food (damaging tissues)

  4. Release toxins → spread via blood → damage distant tissues

🧫 Viral Diseases

• Target specific tissues

  • Influenza → respiratory tract

  • Hepatitis → liver

• Invade and hijack host cells

• Force cells to make viral proteins and replicate virus