Health, disease and the development of medicines revision notes

Lifestyle Changes

Lifestyle changes include improving diet by reducing saturated fats, salt, and sugar, exercising regularly, maintaining a healthy weight, quitting smoking, and reducing alcohol. These changes are non-invasive and have benefits beyond heart health. They are often recommended first, especially for early or mild CVD, but can require ongoing commitment and it may take time before improvements are seen.

Medications and Surgical Procedures

Medications like statins (to lower cholesterol), antihypertensives (to manage blood pressure), and antiplatelets (to reduce clot risk) can be effective for long-term risk reduction. Some patients need them for life and side effects are possible. Surgical treatments, such as angioplasty with stent or coronary artery bypass grafting (CABG), can rapidly restore blood flow in severe cases but carry risks such as infection or bleeding and require hospital recovery. They may still need medication afterwards.

Selective Action of Antibiotics

Antibiotics are powerful medicines used to treat bacterial infections. Their key feature is selective toxicity: they work by targeting specific processes and structures found in bacteria but not in human host cells. This distinction allows antibiotics to kill or inhibit the growth of bacteria without causing significant harm to the infected individual's own body cells.

Mechanisms of Antibiotic Action

Common targets for antibiotics include bacterial cell wall synthesis, unique enzymes involved in bacterial DNA replication, and bacterial-specific ribosomes for protein synthesis. For instance, penicillin inhibits an enzyme necessary for building the bacterial cell wall, leading to cell lysis. Human cells do not have cell walls, so they are unaffected. This selective targeting is why antibiotics are ineffective against viral infections, as viruses use host cell machinery and lack their own cell walls, ribosomes, or unique metabolic pathways that antibiotics could disrupt.

Why Antibiotics Don't Treat Viral Infections

It is essential to understand that antibiotics are only effective against bacteria. They do not work on viruses. This is because viruses are fundamentally different from bacteria; they are not living cells and rely entirely on the host's cellular machinery to reproduce. Since viruses lack the specific bacterial structures and metabolic pathways that antibiotics target, the drugs have no way to disrupt viral replication or destroy them. Using antibiotics for viral infections is ineffective and contributes to antibiotic resistance.

Field Investigation Steps

Start with careful observation for disease symptoms such as discoloured leaves or wilting. Systematically check for and rule out environmental causes including drought, nutrient deficiency, and physical injury. Analyse how symptoms are distributed – uniform across all plants suggests an abiotic cause, while patchy or clustered symptoms point to a potential infectious pathogen.

Laboratory Confirmation

After field analysis, collect samples from affected plants. In the lab, techniques like microscopy are used to detect structures like fungal spores or bacteria. Culturing allows growth and identification of specific microorganisms, while DNA-based tests help rapidly pinpoint the pathogen. These lab approaches provide the evidence to identify the disease agent.

Variables, Controls, and Safe Method

The independent variable is the antimicrobial agent (type or concentration); the dependent variable is the diameter of the inhibition zone. Control variables include strain of bacteria, agar thickness, incubation temperature (never above 25°C), disc size, and exposure time. Use aseptic technique: disinfect surfaces, wear gloves and goggles, sterilise tools, only open plates in brief supervised periods. During setup, inoculate the plate evenly, place the discs using sterilised forceps, and include a control disc. Seal with tape and label. After incubation, DO NOT open the plate; measure inhibition zones through the closed lid. Always work under supervision.

Graphical Analysis, Results and Microbiology Safety

After incubation, measure inhibition-zone diameters through the closed lid in millimetres. Repeat measurements and calculate average values for reliability. Suitable graphs: bar graphs (for different agents/types) or line graphs (for increasing concentrations), plotting type/concentration on the x-axis and mean diameter on the y-axis. State uncertainty (e.g., ±1 mm ruler accuracy) and calculate percentage error as (uncertainty / mean measured value) x 100%. All used plates and materials must be sterilised and safely disposed of after use according to school/lab protocols. Never open plates after incubation or incubate at body temperature.