part c: short answer (6 questions)
15. explain what homeostasis is and why it is important for living organisms.
16. describe one way bacteria cause disease in the human body.
17. explain how viruses differ from bacteria in the way they cause disease.
18. give an example of a hereditary factor that may lead to disease.
19. why are bacteria and viruses such a threat to human health? provide two reasons.

Question

Accepted Answer

### Question 15
# Brief Explanations:
Homeostasis is the ability of an organism to maintain a stable internal environment (e.g., stable temperature, pH, glucose levels) despite external changes. It is important because biochemical processes, enzyme function, and cell structure rely on specific conditions. Without homeostasis, cells would malfunction, and the organism could not survive (e.g., enzymes denature at extreme temperatures/pH, so homeostasis keeps these within optimal ranges for metabolism).
# Answer:
Homeostasis is the maintenance of a stable internal environment (e.g., temperature, pH, nutrient levels) in an organism. It is important because biological processes (like enzyme activity, cell function) require specific conditions; without it, cells malfunction, and the organism cannot survive (e.g., enzymes denature outside optimal pH/temperature, so homeostasis preserves these for metabolism).

### Question 16
# Brief Explanations:
One way bacteria cause disease is by producing toxins. Bacterial toxins (e.g., exotoxins or endotoxins) disrupt normal cell function. For example, Clostridium botulinum produces botulinum toxin, which blocks nerve signals, causing muscle paralysis (botulism). Alternatively, bacteria can invade and damage tissues (e.g., Streptococcus pyogenes invades throat tissue, causing strep throat, or Salmonella invades intestinal cells, causing diarrhea).
# Answer:
Bacteria cause disease by producing toxins (e.g., Clostridium botulinum’s botulinum toxin, which blocks nerve signals, causing paralysis) or invading/damaging tissues (e.g., Streptococcus pyogenes invades throat tissue, causing strep throat).

### Question 17
# Brief Explanations:
Viruses differ from bacteria in disease causation because viruses are non - living outside a host and must infect host cells to replicate. They hijack host cell machinery to make more viruses, damaging or killing the cell (e.g., influenza virus infects respiratory cells, causing cell lysis and flu symptoms). Bacteria are living, can reproduce independently (e.g., by binary fission), and cause disease by producing toxins, invading tissues, or competing with host cells for nutrients. Also, antibiotics kill bacteria but not viruses (since viruses lack bacterial structures like cell walls).
# Answer:
Viruses are non - living outside hosts and must infect host cells to replicate (hijacking cell machinery, damaging/killing cells, e.g., influenza). Bacteria are living, reproduce independently (e.g., binary fission), and cause disease via toxins, tissue invasion, or nutrient competition. Antibiotics kill bacteria but not viruses (viruses lack bacterial targets like cell walls).

### Question 18
# Brief Explanations:
An example of a hereditary factor causing disease is a mutation in the BRCA1/BRCA2 genes. Inherited mutations in these genes significantly increase the risk of breast and ovarian cancer. Another example is sickle - cell anemia, caused by an inherited mutation in the hemoglobin gene, leading to abnormal red blood cells that block blood vessels and cause pain, organ damage, etc. Huntington’s disease, caused by an inherited dominant allele, leads to progressive neurological decline.
# Answer:
An example is a BRCA1/BRCA2 gene mutation (increases breast/ovarian cancer risk) or sickle - cell anemia (inherited hemoglobin gene mutation causes abnormal red blood cells, pain/organ damage) or Huntington’s disease (inherited dominant allele causes neurological decline).

### Question 19
# Brief Explanations:
Bacteria and viruses threaten human health for two reasons: 1) They cause infections: Bacteria (e.g., tuberculosis - causing Mycobacterium tuberculosis) and viruses (e.g., COVID - 19 virus) infect cells/tissues, triggering illness (e.g., respiratory failure, organ damage). 2) They can evolve resistance or mutate: Bacteria develop antibiotic resistance (e.g., MRSA resists many antibiotics), making infections hard to treat. Viruses mutate (e.g., influenza’s antigenic drift) to evade immunity, requiring new vaccines. Also, they spread easily (e.g., via droplets, contact), causing epidemics/pandemics.
# Answer:
1. They cause infections: Bacteria (e.g., Mycobacterium tuberculosis causes tuberculosis) and viruses (e.g., SARS - CoV - 2 causes COVID - 19) infect cells/tissues, triggering illness (e.g., respiratory failure, organ damage). 2. They evolve resistance/mutate: Bacteria develop antibiotic resistance (e.g., MRSA), and viruses mutate (e.g., influenza’s antigenic drift) to evade immunity, making control/treatment hard.

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Question 15

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Question 16