Biology B5 Communicable Diseases

Good/Balanced Diet: Essential for overall health; an unhealthy diet can lead to diseases like diabetes.
Exercise and Stress: Both physical activity and stress management are important for maintaining health.
Life Situations: Access to medicines can significantly influence health outcomes.
Fitness: Refers to the condition of being physically healthy.
Disease: Conditions that cause ill health, influenced by lifestyle factors or unrelated factors.

Definition: Diseases that can spread from person to person or between animals and people.
Causes: Include pathogens such as:
- Viruses: e.g., common cold, COVID-19.
- Bacteria: e.g., cholera, salmonella.
- Parasites: e.g., malaria.
- Fungi: e.g., athlete's foot.

Definition: Diseases that are not spread between people.
Examples: Asthma, coronary heart disease, cancer, diabetes (typically chronic, starting slowly and lasting long).
Interactions: Some diseases can influence each other, e.g., individuals with immune system problems may struggle to combat communicable diseases.
Cancer Example: Certain cancers can be triggered by viral infections, such as HPV leading to cervical cancer.
Immune Reactions: Pathogen interactions can trigger allergic reactions or worsen existing conditions like asthma.

Correlation: A link or association between two factors.
Causal Mechanism: Explains how one factor affects another, such as lifestyle leading to health conditions.

Pathogens: Micro-organisms responsible for diseases. They can be found in both plants and animals.
Modes of Transmission:
- Airborne: Pathogens can be inhaled through droplets from coughing, sneezing, and talking (e.g., influenza, tuberculosis).
- Waterborne: Contaminated water sources can spread diseases (e.g., cholera).
- Direct Contact: Pathogens transferred through touch (e.g., athlete's foot).

Key Prevention Methods:
- Hygiene: Regular hand washing to prevent the spread of pathogens.
- Vaccination: Immunization to establish immunity against specific pathogens.
- Isolation/Quarantine: Separating infected individuals to prevent disease transmission.

Bacteria:
- Prokaryotic cells that cause illness by producing toxins.
- Typically very small (3/100th the size of eukaryotic cells) and replicate through binary fission.
Viruses:
- Not classified as cells; reproduce by invading host cells, using the host cell's machinery for replication.
- Cause damage to host cells, leading to illness.
Fungi:
- Some fungi are unicellular and others are multicellular, composed of filamentous , structures (hyphae).
- Can infect both plants and humans (e.g., athlete's foot).
Protists:
- Eukaryotic, single-celled organisms. Some are parasites that depend on host organisms (e.g., malaria).

Ignaz Semmelweis: 18th-century doctor who noted that handwashing before delivering babies significantly reduced childbed fever death rates.
Louis Pasteur: Discovered microorganisms cause disease, and developed methods to kill bacteria:
- Increasing Temperature: Boiling can kill bacteria.
- Disinfectants: Chemicals used on surfaces to kill pathogens.
- Antiseptics: Safe for bodily use to kill bacteria.
- Antibiotics: Target harmful bacteria inside the body.
Sterilization: Important in preparing hygienic conditions (e.g., for surgical procedures).

Viruses: Non-cellular and not living as they can only reproduce within host cells.

Measles: Spread by airborne droplets; causes fever and rash. Can lead to serious complications like pneumonia.
- Vaccination is common at a young age.
HIV (Human Immunodeficiency Virus): Spreads through sexual contact or blood exchange.
- Initial flu-like symptoms followed by an asymptomatic period; can lead to AIDS.
Tobacco Mosaic Virus (TMV): Affects various plant species, causes mottled leaf patterns, preventing effective photosynthesis.
- Spread through direct contact and insects; no current treatment available.

Bacteria: Single-celled prokaryotes without a nucleus; can reproduce independently.

Salmonella: Causes food poisoning through contaminated food.
- Symptoms include fever, cramps, and diarrhea. Hydration is essential for recovery.
- Vaccination is used in poultry in the UK to control spread.
Gonorrhea: A sexually transmitted disease spread through unprotected sex.
- Symptoms include painful urination and discharge; treatment is complicated by antibiotic resistance.

Rose Black Spot: A fungus that causes leaf discoloration and loss.
- Spread through wind and water, treated with fungicides.
- Common human fungal diseases include athlete's foot and ringworm.

Malaria: Caused by protozoan parasites, transmitted through mosquito vectors.
- Symptoms include recurring fever; prevention involves insecticides and antimalarial drugs.

External Defenses: Non-specific barriers to pathogens include skin, mucus in respiratory passages, and stomach acid.
Immune System:
- White Blood Cells: Key players in identifying and eradicating pathogens through various mechanisms:
1. Phagocytosis: Engulfing and digesting foreign cells.
2. Antitoxin Production: Counteracting harmful toxins from bacteria.
3. Antibody Production: Specific proteins produced to target unique antigens on pathogens.
  - Antibodies can enhance the ability of white blood cells to find and destroy pathogens more efficiently.

Plants: Can suffer from diseases caused by viral, bacterial, and fungal pathogens, as well as pest infestations.
- Symptoms: Stunted growth, leaf spots, discoloured leaves, and decay indicate plant health issues.

Mineral Ions: Essential for plant health:
- Nitrates: Required for protein synthesis and growth; deficiency leads to stunted growth.
- Magnesium Ions: Necessary for chlorophyll production; deficiency leads to chlorosis (yellowing of leaves).

Physical Defenses:
- Waxy cuticle and cellulose cell walls act as barriers.
- Dead cell layers in stems prevent pathogen entry.
Chemical Defenses:
- Production of antibacterial substances and poisons deters herbivores.
Mechanical Defenses:
- Features like thorns and sensitive leaves that resist predation and injury.