Crammed science study

Lytic cycle

Virus attaches to host cell, injects genetic material, takes over cell machinery, new viruses are assembled, the cell undergoes lysis and releases viruses, killing the host cell

Lysogenic cycle

Virus injects genetic material which inserts into the host chromosome, remains dormant, is copied during cell division, and may later enter the lytic cycle

Difference between lytic and lysogenic cycles

The lytic cycle kills the host cell quickly, while the lysogenic cycle remains dormant and does not immediately destroy the cell

Physical defences

Skin acts as a barrier, mucus traps pathogens, cilia move mucus out of airways, and blood clotting prevents pathogens entering wounds

Chemical defences

Stomach acid kills pathogens, enzymes in tears and saliva destroy bacteria, and antibacterial chemicals are produced by the skin

Role of white blood cells

They defend the body against pathogens by engulfing them or producing antibodies

Lymphocytes

White blood cells that recognise antigens and produce specific antibodies

Antibodies

Proteins that bind to specific antigens on pathogens, causing them to clump and be destroyed

Memory lymphocytes

White blood cells that remain after infection and allow a faster, stronger secondary immune response

Primary immune response

Slow response on first exposure to a pathogen producing few antibodies

Secondary immune response

Faster and stronger response due to memory lymphocytes

Immunity

The ability of the body to resist infection due to antibodies or memory cells

Vaccination

Vaccines contain dead or inactive pathogens which stimulate an immune response and produce memory lymphocytes

Advantages of vaccination

Prevents disease, reduces spread, and protects vulnerable people through herd immunity

Disadvantages of vaccination

Side effects, does not work for everyone, and pathogens can mutate

Antibiotics

Drugs that kill bacteria or stop them reproducing but do not work against viruses

Antibiotic resistance

When bacteria mutate, survive antibiotic treatment, reproduce, and antibiotics become ineffective

Testing antibiotics

Bacteria are grown on agar plates, antibiotic discs are added, and the zone of inhibition is measured

Zone of inhibition

The clear area around an antibiotic disc where bacteria have been killed

Calculating area of clear zone

Measure the radius and use the formula area equals pi times radius squared

Aseptic technique

Methods used to prevent contamination, including sterilising equipment and keeping Petri dishes closed

Drug discovery

Scientists identify substances that may be effective medicines

Pre-clinical testing

Drugs are tested on cells, tissues, and animals to check toxicity and dosage

Clinical trials

Drugs are tested on humans in small groups then large groups to test effectiveness and side effects

Placebo

A fake treatment used for comparison in clinical trials

Double blind trial

Neither the patient nor doctor knows who receives the real drug, reducing bias

Monoclonal antibodies

Identical antibodies produced from one clone of cells that bind to a specific antigen

Uses of monoclonal antibodies

Targeting cancer cells, pregnancy tests, diagnosing disease, and delivering drugs

Advantages of monoclonal antibodies

Highly specific and targeted to particular cells

Disadvantages of monoclonal antibodies

Side effects, expensive to produce, and can trigger immune reactions

Communicable disease

A disease caused by pathogens that can be spread between organisms

Non-communicable disease

A disease that is not infectious and cannot be spread between people

Risk factors for non-communicable disease

Smoking, alcohol, poor diet, lack of exercise, and genetic factors

Cardiovascular disease

A disease of the heart and blood vessels often caused by blocked arteries

Cause of blocked arteries

Fatty deposits and cholesterol build up, reducing blood flow

Lifestyle treatments for CVD

Exercise, healthy diet, stopping smoking, and reducing alcohol intake

Surgical treatments for CVD

Stents, coronary bypass surgery, and heart transplants

Drug treatments for CVD

Statins reduce cholesterol, beta blockers reduce heart rate, and diuretics reduce blood volume

Kwashiorkor

Lack of protein causing swollen belly and muscle wasting

Scurvy

Lack of vitamin C causing bleeding gums and weakness

Rickets

Lack of vitamin D causing soft bones and bowed legs

Anaemia

Lack of iron causing tiredness and pale skin