Question
6. Differention the lifewing term (2) Marks) in Indertion and disease (1) markin immunity (3) Marks) 1. is Sure any three couses of food spoilage (1) Marlin to Differentiate the two compress of food pointming (2) Marks 8. List any four emptions of food pointing (4) Marks) SECTION B. ANSWER ANY TWO QUESTIONS (30 MARKS) production processes (15Marks) 10. in Discuss the minitial populations present in nimila (4) Marks) to their role in only (4) Marks) C. entronmental factors affecting merubial ahundance in soil (4) Marks) ( ) An example of becterial, fungsi and wind and home diseases of humans and plants (3) Marks) 11. Discuss five physical control methods of microorganisms (15Marks)
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**6. Differentiate the following terms:****(a) Infection and Disease (2 Marks)*** **Infection:** The invasion and multiplication of pathogenic microorganisms (bacteria, viruses, fungi, parasites) within a host organism. Infection doesn't always lead to disease. Someone can be infected but asymptomatic.* **Disease:** A noticeable impairment of health, characterized by specific signs and symptoms. Disease results when the infection causes damage or disruption to the host's tissues and organs. It represents a change from a state of health.**(b) Immunity (3 Marks)**Immunity is the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells. There are various types of immunity, including:* **Innate Immunity:** Present from birth, providing non-specific defense mechanisms against a wide range of pathogens.* **Adaptive Immunity:** Develops throughout life as the body encounters and responds to specific pathogens. This type of immunity is characterized by immunological memory, leading to a more rapid and effective response upon subsequent exposure to the same pathogen.**7.****(a) State any three causes of food spoilage (3 Marks)*** **Microorganisms:** Bacteria, yeasts, and molds are primary causes of food spoilage. They consume the food, producing waste products that alter the flavor, texture, and appearance.* **Enzymes:** Naturally present in food, enzymes can cause undesirable changes like browning or softening.* **Oxidation:** Exposure to air can cause fats to become rancid and other components to degrade, leading to off-flavors and discoloration.**(b) Differentiate the two concepts of food poisoning (2 Marks)*** **Food Infection:** Illness caused by the *growth* of microorganisms *after* they are ingested with contaminated food. Symptoms typically appear after a longer incubation period.* **Food Intoxication:** Illness caused by ingesting food containing *pre-formed toxins* produced by microorganisms. Symptoms generally appear more quickly.**(c) List any four symptoms of food poisoning (4 Marks)*** Nausea* Vomiting* Diarrhea* Abdominal cramps**SECTION B. ANSWER ANY TWO QUESTIONS (30 MARKS)****10. (a) Discuss the microbial populations present in the soil (4 Marks)**Soil is a complex ecosystem containing a vast diversity of microorganisms, including bacteria, fungi, actinomycetes, algae, protozoa, and viruses. These populations vary in abundance and distribution depending on factors like nutrient availability, moisture content, and temperature.**(b) Explain their role in soil (4 Marks)**Soil microorganisms play crucial roles in nutrient cycling, decomposition of organic matter, nitrogen fixation, soil aggregation, and suppression of plant pathogens. They are essential for maintaining soil fertility and plant health.**(c) Environmental factors affecting microbial abundance in soil (4 Marks)*** **Temperature:** Microbial activity generally increases with temperature up to an optimum level, after which it declines.* **Moisture:** Adequate moisture is essential for microbial growth and activity.* **pH:** Different microorganisms thrive at different pH levels.* **Nutrient availability:** The availability of carbon, nitrogen, phosphorus, and other nutrients influences microbial growth and activity.**(d) An example of bacterial, fungal, and viral diseases of humans and plants (3 Marks)*** **Bacterial:** Humans: Tuberculosis (caused by *Mycobacterium tuberculosis*); Plants: Fire blight (caused by *Erwinia amylovora*)* **Fungal:** Humans: Athlete's foot (caused by various dermatophytes); Plants: Rust (caused by various rust fungi)* **Viral:** Humans: Influenza (caused by influenza viruses); Plants: Tobacco mosaic virus (TMV)**11. Discuss five physical control methods of microorganisms (15 Marks)*** **Heat:** High temperatures, such as those used in sterilization (autoclaving, dry heat) and pasteurization, denature proteins and kill microorganisms.* **Filtration:** Physical removal of microorganisms from liquids or gases using filters with pore sizes small enough to trap them. HEPA filters are an example.* **Radiation:** Ultraviolet (UV) radiation damages microbial DNA, preventing replication. Ionizing radiation (gamma rays, X-rays) is also used for sterilization.* **Desiccation (Drying):** Reduces the water activity, inhibiting microbial growth. Many food preservation methods rely on this principle.* **Low Temperature:** Refrigeration and freezing slow down or stop microbial growth but don't necessarily kill all microorganisms.