Biology Topic 3

Created by

Anugrah Ajay

Cards (88)

What are pathogens?
microorganisms that cause communicable diseases e.g. bacteria, viruses, protists and fungi are all types of pathogen
Features of bacteria:
-small prokaryotic cells that can infect animals and plants
-reproduce rapidly in optimum conditions
-releases toxins that damage cells and tissues and makes the infected organism suffer symptoms
-not always harmful
-can be useful e.g. it is found in large intestine of some animals where they digest cellulose so the products can be absorbed into the blood and used around the body
Features of viruses:
-not classified as cells or even living organisms
-rely on host cells(cells that are invaded)to survive and reproduce
-they insert genetic material into cells of infected organism so that they can reproduce rapidly which causes the cells to burst and release more viruses which cause further inflections in the body
Features of protists:
-unicellular
-can be parasitic meaning they live on or in a host organism
-often transferred between hosts by organisms that don't get the disease itself called vectors
Features of fungi:
-can either grow on living tissue or be unicellular or have a body of hyphae
-hyphae penetrate living tissues which causes infections and produces spores which spreads infections to other organism
-fungal infections are the most common in plants
Ways that pathogens are spread:
-air e.g. coughs and sneezes
-water e.g. cholera
-direct contact e.g. skin and contaminated surfaces
-vectors which are organism that carry the pathogen without carrying the disease
Ways to prevent spread of diseases
-keeping good hygiene e.g. washing your hands
-isolation
-insecticides
-vaccinations
Features of measles
-highly contagious viral disease
-mainly spread through coughing and sneezing droplets
-symptoms e.g. red skin rash and high temperature
-can cause complications like pneumonia or brain inflammation
-no treatment available
-vaccinated against it at early ages
Features of HIV:
-Viral disease which leads to AIDS
-Spread through sexual contact, exchanging body fluids and from mother to baby
-first appears as flu-like symptoms then travel to lymph nodes to destroy cells involved in immune response
-can stay hidden until immune system is so damaged that it cannot cope with other infections
-can be treated with antiretroviral drugs which slow the virus down by preventing it from attacking immune cells
Features of TMV(Tobacco Mosaic Virus) 
-plant virus which affects multiple different species
-distinct mosaic pattern visible on leaves
-discolouration of leaf limits photosynthesis
-stunts growth
Features of salmonella
-bacteria that causes food poisoning by releasing toxins
-symptoms : fever, abdominal cramps, vomiting and diarrhoea
-may have been acquired by the animal before it was killed for food or when the food was being prepared (if conditions were unhygienic)
-poultry are vaccinated against salmonella
Features of gonorrhoea:
-bacterial infection spread by sexual contact as it is an STD
-symptoms: thick yellow/green discharge from vagina or penis and pain while urinating
-used to be treated with penicillin until strains of bacteria became resistant
-antibiotics and protective methods e.g. condoms are used to prevent the spread
Features of rose black spot:
-fungal disease which affects rose plants
-black or purple dots visible on leaves causing them to turn yellow and eventually drop off
-stunted growth due to less occurrence of photosynthesis
-spread through water and wind
-fungicides used to treat plant
Features of malaria
-caused by a protist that gets transported between animals by mosquitoes which act as a vector
-protists picked up by mosquitoes when they feed on infected animals which allow them to complete part of their life cycle in mosquito vector before being transferred
-symptoms: repeating fever episodes which can be fatal
-prevented by reduction in the amount of mosquitoes breeding and protecting people with mosquito nets and insecticides
How does the skin act as a defence system?
It covers the majority of the body and acts as a physical barrier to prevent pathogens from getting in.
What happens when a person's skin is wounded?
Platelets gather at the site of the wound and a scab forms to maintain the physical barrier
How does the nose acts as a defence system?
It has hairs and mucus that acts as a physical barrier and trap any pathogens that try to enter from the air
How are pathogens removed from the body via the nose
when a person sneezes or blows their nose
How do the trachea and bronchi acts as a defence system?
they have goblet cells which produce mucus which traps pathogens
What are cilia and what do they do?
they are tiny hairs which waft the mucus and pathogen upwards to the throat so it can be swallowed and sent to the stomach
How does the stomach acts as a defence system?
it contains hydrochloric acid that acts as a chemical barrier as it kills all pathogens that enter the stomach through food or mucus
What do phagocytes do?
they engulf and destroy pathogens or foreign particles in the body.
What is phagocytosis? 
a non-specific process by which phagocytes engulf and digest pathogens and is sometimes aided by lymphocytes
What do lymphocytes do?
they produce antibodies with specific shapes which enable them to bind to the antigens on the pathogen which cause the pathogens to clump together making them easier to engulf
What are memory cells
lymphocytes that remain in the blood after an infection to provide a quicker response to future infections of the same disease/infection to prevent further cell damage
What else do lymphocytes produce and why?
antitoxins which neutralise toxic substances produced by the pathogen to prevent cell and tissue damage
Advantages of vaccines
reduced the occurrence of some diseases and completely eradicated others
can create herd immunity to prevent epidemics if vaccines are given to enough people
Disadvantages of vaccines
not always 100% effective at providing immunity
can have side effects of different severities from rashes to fevers
What do painkillers do?
they treat symptoms e.g. headaches and sore throats but they don't cure the disease itself so the body's immune response must step in and destroy the pathogen
What do antibiotics do?
slow/stop the growth of harmful or infectious bacteria, curing the person of the disease
Is there one antibiotic which cures all infections? 
No, specific antibiotics are used to treat specfic bacterial infections
What type of cell do antibiotics only work on?
Bacteria
Why can antibiotics not kill viruses?
they reproduce inside host cells so it is extremely difficult to destroy it without also destroying the host cells
Antibodies bind to the surface proteins of the pathogens and mark them as foreign bodies to be destroyed by phagocytes
What has the discovery and development of certain antibiotics done?
it has reduced the amount of deaths from bacterial diseases
What has the excess usage of antibiotics resulted in?
some strains of bacteria have become resistant to antibiotics
When does antibiotic resistance evolve?
randomly
How does a bacterial cell become resistant to a certain type of antibiotic?
A random mutation happens in the genetic material of a bacterial cell that makes it resistant to a certain type of antibiotic
How does antibiotics slowly become more and more resistant to the body?
The bacterial cells which are antibiotic resistant to that specific antibiotic will survive all treatments and reproduce in the body causing an increase in the number of resistant bacterial strain
How can the rate of development of resistant bacterial strains be slowed down?
limiting the use of antibiotics to more serious infections