11 — infectious disease Flashcards
disease
A disease is a condition that causes the body to function less effectively. Diseases produce specific signs or symptoms.
Signs vs symptoms of diseases
Signs of diseases can be qualitative/quantitative and observed or measured. symptoms can be described or felt.(eg. headaches, fatigue, nausea)
Pathogens
Pathogens r disease-causing organisms. They include bacteria n viruses.
Spread of infectious diseases
- Through droplets in air
- Respiratory droplets contain respiratory tract secretions that may hv pathogens n infect others
- By direct contact
- Exchanging body fluids during sexual intercourse → Sexually transmitted infections (STIs) eg Human Immunodeficiency Virus (HIV)
- Blood from infected person contacts mucous membranes n bloodstream of non-infected
- By contaminated food n water
- Pathogens such as cholera, salmonella can contaminate food n water sources
- Methods to prevent n control spread of water & food-borne diseases:
- Practicing hygienic food preparation n storage
- Hving good personal hygiene
- Maintaining clean water supply
- Ensuring proper sewage treatment
- Vaccination
The virus attaches to the host cell via its specific antigens and injects its viral DNA/ genetic material into the host cell. Using the host cell’s reproduction mechanism, the virus reproduces and multiplies. These viruses multiply and spread to other cells to continue the cycle
Structure of a virus
- Has a protein coat with specific antigens on its surface for attachments, enclosing genetic material, either RNA or DNA
- Antigens are identifiable surface features such as proteins
of pathogens that white blood cells learn to recognise. [1]
The lymphocytes will produce complementary antibodies
[1] to target those antigens to facilitate agglutination and
neutralization [1] of the pathogens.
- Antigens are identifiable surface features such as proteins
- No cellular structures such as cell membrane, cytoplasm or organelles
- Does not grow, move, feed, respire or excrete
- Requires a living host cell to obtain necessary materials for reproduction
Structure of a typical bacteria cell
- has a cell wall, cell membrane flagella, cytoplasm and ribosomes
- Contains DNA (single, circular DNA strand)
- No membrane bound nucleus
- Some r pathogenic, some r non-pathogenic
Influenza/flu
- A disease that attacks respiratory system
- Cause: influenza virus
- Transmission:
- Thru droplets in air
- Contaminated surfaces
- Direct contact with mucous membranes
Methods to reduce transmission of virus n bacteria
- Vaccination of __
- Avoid close contact with ppl who hv flu
- Wear masks
- Wash ur hands w soap n water or rub w disinfectant
- Avid touching eyes, nose or mouth aft
- Take antiviral drugs (for viruses)
- Take antibiotics prescribed by doc (for bacteria’s)
Pneumococcal disease
- Caused by pneumococcus bacteria
- Transmission: mainly thru respiratory droplets
- Signs n symptoms: fever, headache, vomiting, cough, chest pain, rapid breathing
Vaccines
Vaccine contains an agent that resembles a pathogen and stimulates wbc to quickly produce antibodies when pathogen invades.
Why do we need vaccines even after infection:
- improving level of protection of antibodies from prev infection
- Can still get infected again
- Body can respond appropriately n reduce risk of infection
- Prevent severe symptoms
How to make vaccines
- Weakened live virus, X reproduce & cause illness
- Viruses made inactive using chemical
- Extract parts of virus
- Toxins taken from bacteria rendered inactive
- Bacteria’s coating linked w harmless protein to form conjugate vaccine
Antibiotics
drugs used to treat bacterial infections, made by microorganisms, by inhibiting the growth of or kill bacteria.
Why antibiotics are ineffective against viruses
Antibiotics
- Act on bacterial cell walls but viruses do not hv cell walls
- Break up cell membranes but viruses do not hv cm
- Act on ribosomes, inhibiting protein synthesis n growth but viruses do not hv ribosomes n do not grow
- since viruses do not hv [all 3], antibiotics would not be effective against viruses.
Functions of antibiotics
-
Inhibits the synthesis of bacterial cell walls
- Some antibiotics eg penicillin prevent synthesis of cell walls
- Cell walls weakened, water enters cell via osmosis, cell expands, bursts, dies
-
Inhibits cell membrane function
- Bacterial cell no longer protected from env n substances can move into bacterial cell
-
Inhibits protein synthesis in ribosome
- Antibiotics bind to bacterial ribosomes, preventing them from taking part in protein synthesis, inhibiting growth
-
Inhibits enzyme action in cytoplasm
- Inhibits enzyme needed for synthesis of folic acid that aids in growth of bacteria
Antibiotic resistance and how to minimise
Overuse of antibiotics naturally select for mutated bacteria to be resistant to antibiotic → bacteria w resistant to antibiotics survives → multiply n pass on resistant genes → spread of bacteria w resistant → pathogens survive → antibiotics r ineffective
Can be reduced by
- Not misusing or overusing antibiotics
- Completing full course of antibiotics prescribed by docs so all bacteria r killed
- Using antibiotics only when necessary
State and explain how sneezing can result in disease transmission. [2]
expelled air contains pathogen / bacteria / viruses [1] which can be breathed in by another person / lands on another person [1] accept come in contact
Explain the different ways in which vaccines and antibiotics are used. [5]
Vaccines can be taken orally or administered through an injection. They are used to decrease the risk of a viral infection. The vaccine injected stimulates the white blood cells to produce antibodies against the pathogens to prevent a person from getting the disease. [1] When the pathogen enters the body, the antibodies will kill the pathogens, hence reducing the chances of the person being infected with the disease. [1]
The white blood cells that recognise the pathogens may also divide and increase in numbers to produce more antibodies and remain in the bloodstream as memory cells to recognise, neutralise and kill the pathogens in the future. [1]
Antibiotics are used to treat the person infected with the disease. Drugs used to treat bacterial infections are made by microorganisms which is used to kill or inhibit the growth of bacteria by preventing the synthesis of cell walls. When cell walls are weakened, water enters the cell by osmosis and the bacteria cell then expands, bursts and dies. [1] Antibiotics also inhibit cell membrane function. Antibiotics also interferes with the growth and metabolic activities of the pathogens as they inhibit the enzyme needed for the synthesis of folic acid, hence inhibiting the growth of bacteria. Antibiotics also bind to bacterial ribosomes, preventing the
ribosomes from taking part in protein synthesis, inhibiting growth. [1]
Action of virus
The virus attaches to the host cell via its specific antigens and injects its viral DNA/ genetic material into the host cell. Using the host cell’s reproduction mechanism, the virus reproduces and multiplies. These viruses multiply and spread to other cells to continue the cycle
