Lecture Notes on Viruses and Bacteria

Introduction

• Discussion on copper in the periodic table: Cu.
• Mention of copper as a conductor in electrical wires.

Viruses

Myths About Viruses and Bacteria

• Viruses vs. Bacteria:
  • Bacteria are living organisms.
  • Viruses are not living; they cannot be classified into a kingdom.
  • Viruses are categorized by shape, size, and the host they infect.

Characteristics of Viruses

• Extremely small, visible only with an electron microscope.
• Active only inside a living cell; ceases activities outside.
• Can be crystallized and stored indefinitely but retain infection ability.

Structure of Viruses

• Viruses consist of DNA/RNA surrounded by a protein coat (capsid).
• Capsid shape must match host cell receptors for virus entry.

Reproduction of Viruses

• Viruses reproduce by hijacking host cells to produce viral parts.
• The reproductive cycle ends with cell destruction, releasing new viruses.

Viral Diseases

• Limited options for curing viral infections; antibiotics are ineffective.
• New drugs slow down viral reproduction but do not cure.
• Vaccines train the immune system to recognize pathogens.

Bacteria

Overview of Bacteria

• Bacteria are single-celled prokaryotes, lack a true nucleus.
• Two domains of bacteria: Archaea and Eubacteria.

Types of Archaea

1. Methanogens: Convert hydrogen and carbon dioxide into methane, thrive in anaerobic environments (e.g., cow digestive tracts).
2. Halophiles: Salt-loving, live in high salt concentrations.
3. Thermoacidophiles: Thrive in high temperatures and acidic environments.

Eubacteria

• True bacteria with diverse habitats and classifications.
• Identified by shape, cell wall composition, movement, and energy acquisition methods.

Shapes of Bacteria

1. Cocci: Spherical.
2. Bacilli: Rod-shaped.
3. Spirilla: Spiral-shaped.

Bacterial Movement

• Some bacteria are motile (use flagella), others do not move at all.
• Movement methods include lashing, snaking, or gliding.

Metabolic Diversity

• Most bacteria are heterotrophs (cannot produce their own food).
• Some bacteria are autotrophs (can produce their own food).
  • Photoautotrophs: Use light energy.
  • Chemoautotrophs: Use inorganic reactions.

Importance of Bacteria

1. Decomposers: Recycle essential elements from dead organisms.
2. Human Uses: Produce food (sour cream, yogurt, cheese) and clean up oil spills.
3. Pathogens: Cause diseases by damaging tissues or releasing toxins.

Antibiotics

• Antibiotics target bacterial cells, disrupting their functions (e.g., rupturing cell walls).
• Ineffective against viruses, leading to antibiotic resistance.

Conclusion

• Overview of content covered on viruses and bacteria.
• Reminder of upcoming quizzes and lab sessions.
• Importance of understanding the differences between viruses and bacteria for health and science.