Types of Microorganisms

Ever wondered what makes plants different from animals, or why bread rises? It all comes down to how different organisms are built and behave. Eukaryotic organisms (plants, animals, fungi, and protoctists) have their genetic material stored in a nucleus, whilst prokaryotic organisms (bacteria) don't.

Plants are the only organisms with chloroplasts for photosynthesis and cell walls made of cellulose. They store energy as starch and can reproduce both sexually and asexually through runners, tubers, and bulbs. Animals lack cell walls and chloroplasts, store energy as glycogen, and rely on their nervous system for coordination.

Fungi have cell walls made of chitin (not cellulose) and get their nutrition by breaking down dead material - this is called saprotrophic nutrition. They reproduce through budding and form thread-like structures called hyphae. Bacteria are single-celled prokaryotes that reproduce incredibly quickly through binary fission - some can double their population every 20 minutes!

Key Point: Viruses aren't actually living organisms - they're just protein coats containing DNA or RNA that can only reproduce inside other living cells.

Biotechnology and Food Production

Your favourite foods rely heavily on microorganisms working behind the scenes. Yeast is particularly important because it can switch between different types of respiration depending on oxygen availability.

During anaerobic respiration (fermentation), yeast converts glucose into ethanol and carbon dioxide whilst producing energy (ATP). This process makes bread rise - the CO₂ creates bubbles in the dough, whilst the ethanol evaporates during baking. You can investigate fermentation rates by measuring how quickly CO₂ turns hydrogen carbonate indicator yellow.

Yoghurt production involves several careful steps. First, milk undergoes pasteurisation $heating to 85-95°C$ to kill harmful bacteria, then homogenisation breaks down fat droplets. Lactic acid bacteria like lactobacillus are added at 40-45°C, where they ferment lactose and produce lactic acid, dropping the pH to 4.4 and causing the milk to solidify.

Key Point: Biotechnology uses living organisms to create useful products - from the bread you eat to the medicines that keep you healthy.

Immune Response and Industrial Applications

Your body has an amazing defence system that remembers every pathogen $disease-causing microorganism$ it encounters. When harmful bacteria, viruses, fungi, or protoctists invade, your immune system springs into action with a coordinated response.

Lymphocytes are your body's special forces - they produce antibodies specific to each pathogen's antigens (surface proteins). These antibodies stick pathogens together and mark them for destruction, whilst antitoxins neutralise any toxins produced. Phagocytes then engulf and digest the invaders through phagocytosis, changing shape to surround pathogens in vacuoles.

Vaccines contain weakened or dead pathogens that trigger your immune system to produce antibodies and memory cells without making you ill. This creates immunity - if you encounter the real pathogen later, your secondary immune response is much faster than the primary response.

Industrial fermenters use controlled conditions to grow useful microorganisms on a massive scale. Stirring paddles keep everything mixed, whilst temperature and pH probes maintain optimal conditions for maximum productivity.

Key Point: Your immune system's memory cells are why you rarely get the same illness twice - they remember how to fight specific pathogens.