The WHOLE of Edexcel GCSE Biology HEALTH and DISEASE
Health and Disease in EDXL GCC Biology
Understanding Health
- Health is defined as the complete social, physical, and mental well-being of a person, not merely the absence of illness.
Types of Diseases
- Diseases are categorized into two types: communicable and non-communicable. Communicable diseases can be transmitted from person to person, while non-communicable diseases cannot.
Communicable Diseases
- Cholera: Caused by bacteria, primarily spread through contaminated water.
- Tuberculosis: An airborne bacterial disease.
- Chlora Diet Ashbach: A fungal disease affecting plants, spread through air.
- Malaria: Caused by a protist and transmitted via vectors like mosquitoes.
- HIV: A viral infection spread through bodily fluids; chlamydia is another bacterial infection mainly spread through sexual contact.
Viruses as Pathogens
Structure and Replication
- Viruses consist of genetic material (DNA or RNA) encased in a protein coat called a capsid; they lack cellular structures necessary for self-replication and must hijack living cells to reproduce.
Lytic vs Lysogenic Pathways
- Lytic Pathway:
- The virus inserts its genetic material into the host cell, using the cell's machinery to produce new viruses until the cell bursts (lysis), releasing them to infect other cells.
- Lysogenic Pathway:
- The virus integrates its genetic material into the host's DNA, replicating with it during cell division until triggered to enter the lytic cycle later on. This allows for prolonged dormancy within the host's genome before active replication begins again.
Body Defenses Against Pathogens
Physical Barriers
- The skin serves as the primary barrier against pathogens; cuts can allow entry.
- Mucus traps pathogens in respiratory passages.
- Cilia help move trapped pathogens out of the body effectively.
Chemical Barriers
- Stomach Acid: Destroys pathogens ingested with food due to its low pH level.
- Lysozyme: An enzyme found in tears that breaks down pathogen structures, aiding in defense against infections.
Immune System Overview
White Blood Cells
- Phagocytes:
- Engulf and digest pathogens directly by swallowing them whole.
- Lymphocytes:
- Produce antibodies that specifically target antigens present on pathogens; these antibodies bind to antigens marking them for destruction by other immune cells or neutralizing their effects directly.
- Vaccination introduces weakened or dead forms of pathogens to stimulate an immune response without causing disease symptoms initially, preparing lymphocytes for future encounters with actual infections.( t = 272 s)
Monoclonal Antibodies
- Created by fusing lymphocytes with tumor cells (hybridoma), allowing for rapid division while producing specific antibodies efficiently.
Applications
- Commonly used in pregnancy tests where antibodies detect hormones associated with pregnancy; if present, they trigger a color change indicating a positive result.( t = 360 s)
Tumor Detection and Drug Development
Tumor Detection Using Monoclonal Antibodies
- Monoclonal antibodies can be used to locate tumors in the body by attaching radioactive elements to them.
- As these antibodies bind to tumors, scanners can detect the radioactive signals, allowing for tumor identification without invasive procedures.
Drug Development Process
- Before a new drug is approved for use, it undergoes several trial phases starting with pre-clinical trials on human tissue to assess efficacy.
- The next step involves testing on two different species of live animals as mandated by UK law before moving to human trials.
- Clinical trials begin with healthy humans in small groups to monitor severe side effects, followed by larger groups of ill patients if initial tests are successful.
- The goal during drug development is to maximize efficacy while minimizing toxicity, ensuring that the drug helps patients without causing additional harm.
Lifestyle Choices Impacting Health
- Non-communicable diseases often stem from lifestyle choices or genetics; obesity is highlighted as a significant risk factor linked to various health issues.
- Body Mass Index (BMI) and waist-to-hip ratio are common measures used to assess obesity levels and associated health risks.
Effects of Smoking on Cardiovascular Health
- Smoking leads to fatty buildup in arteries, which restricts blood flow and increases strain on the heart, potentially resulting in cardiovascular disease (CVD).
- Treatments for CVD may include stents to open arteries or medications like statins that lower cholesterol levels.
Plant Defenses Against Diseases
- Plants also face diseases and have developed defenses such as a waxy cuticle that protects leaves from pathogens.
- Additionally, plant cells possess cell walls providing extra protection against illness.