SB5g-h, j-l, SB3a-ci Flashcards
What are the physical barriers for plants?
- Cuticle (thick waxy waterproof layer that covers surface of leaves)
- Thick layer of bark
What are 2 ways pathogens can overcome a plant’s physical barrier?
- Using enzymes to hydrolyse the walls of the plant to enter
- Finding other parts of the plant with weaker cell walls
What are the chemical barriers for plants?
- Poisons
- Insect repellents
How do plants use their chemical barriers?
They produce chemical substances that are toxic to pests so once the pest bites the plant they get poisoned.
What is another use for plants?
Used in production of medicine to treat diseases.
What is the medicine and source of medicine for malaria?
Artemisinin - found in Wormwood trees
What is the medicine and source of medicine for pain/fever?
Salicylic acid (aspirin) - found in Willow trees and Meadowsweet trees
How are medicines made free from contamination in labs?
Usage of aseptic techniques ensures the destruction of any pathogens that can contaminate the medicines.
How are medicines sterilised in labs?
Autoclave.
How do farmers check for diseased crops?
Drones.
How do plants get infected?
- Fungal disease spread by spores
- Pests and pathogens in the soil
What are some problems that plants could have?
- Lack of water/ too much water
- Lack of nutrients in the soil
- Pests
- Diseases
What are some symptoms of plant diseases?
- Changes in growth
- Changes in colour of leaves
- Blotching in leaves
- Lesions on stem and leaves
What are 2 ways of identifying problems in plants?
- Distribution analysis - checking the environment of crops (flooding, droughts, lack of nutrients, pests, pathogens)
- Diagnosis - soil and plant samples are sent to labs to test and determine cause of problem
How is plant diagnosis done?
- Pathogens are taken from the plant and grown in agars to check their DNA and identify them
- They check the soil for lack of nutrients and toxins
What are the 2 types of white blood cells involved in fighting off pathogens and treating infections?
- Macrophages/phagocytes
- Lymphocytes
What is the job of macrophages/phagocytes?
- Ingest any pathogen and try to destroy it by phagocytosis
- Release hydrolytic enzymes which digest the pathogen
What is the job of lymphocytes?
- Secrete antibodies to fight off the pathogens
- Destroy the pathogens
What are antigens and what do they do?
Antigens are proteins found on pathogens.
The immune system recognises the antigen and tries to destroy the pathogen. If a body cell gets infected by a pathogen it attaches the antigen on its surface to be seen by the immune system.
What are antibodies and what do they do?
Antibodies are proteins secreted by lymphocytes to destroy pathogens.
It binds on the antigen in order to destroy the pathogen. They are specific.
How does the body fight off pathogens?
- The pathogen invades the body
- The antigen on the pathogen is recognised by the immune system
- The white blood cells that recognise the antigen of the pathogen will send a signal to the specific lymphocyte that produces the specific antibodies for the specific antigen
- The antibody binds on the antigen and destroys the pathogen
- The specific lymphocyte will multiply by mitosis and produce memory cells
What are the 2 types of immune responses?
- Primary immune response
- Secondary immune response
What happens during the primary immune response?
- A pathogen invades the body for the 1st time
- The immune system needs time to recognise the pathogen using its antigen and the correct lymphocyte to produce the correct antibody
- So antibodies are produced after a few days
- The lymphocytes divide by mitosis and also produce memory cells
- Once the pathogens are killed, most of the antibodies break down, but some remain in the blood together with the memory cells
What happens during the secondary immune response?
- Occurs when the same pathogen invades the body for the 2nd time
- The number of antibodies increase rapidly and a lot more antibodies are produced because of the memory cells
- The pathogens are killed before they have the chance to cause the disease and the symptoms
What is immunisation?
When your immune system is triggered to fight off a pathogen artificially using a vaccine.
What do vaccines normally contain?
- Dead pathogen
- Weak pathogen
- Inactive pathogen
- Toxins of the pathogen
- Antigens of the pathogen
What is herd immunity?
It is when most people are immunised against a specific disease. Non-immunised people are protected since they are less likely to come in contact with the pathogen.
What are antibiotics?
Chemical substances that kill bacteria or stop them from multiplying by asexual reproduction. They do not destroy viruses.
What would happen if antibiotics are not used correctly?
The bacteria can easily develop resistance against the antibiotics if not used correctly.
Why can antibiotics not destroy viruses?
They kill by attacking the peptidoglycan cell wall of the bacteria and viruses do not have a cell wall, therefore cannot affect them.
What are clinical trials?
Several stages of testing new antibiotics before releasing them in the market, in order to be safe for humans.
What are the 5 stages of clinical trials?
- Pre-clinical trials
- Tested on animals
- Clinical trial Phase I
- Clinical trial Phase II
- Clinical trial Phase III
What happens in the pre-clinical trial stage?
The antibiotic is tested on cells and tissues to see if the bacteria are destroyed.
What happens in the animal testing stage?
The antibiotic is tested on full body organism such as an animal to see how the drug interacts with the whole organism.
What happens during the clinical trial Phase I stage?
The drug is tested on small number of healthy individuals and inserted at a low concentration to monitor any toxic effects. Checks safety.
What happens during the clinical trial Phase II stage?
The drug is tested on small number of patients. Effectiveness of treatment is monitored.
What happens during the clinical trial Phase III stage?
Double-blind trials occur. Drug is tested on large number of patients. This stage is to find the correct dose and check any side effects.
What are double-blind trials?
Some people take the actual drug, while others take a placebo (sugar-coated pill with no effect). Doctors and patients do not know who is taking the drug and who isn’t, to reduce bias and see if drug works and is better than an old one.
What are monoclonal antibodies?
Identical antibodies that recognise a specific antigen.
How are monoclonal antibodies made?
- Antigen is injected into mice to activate the desired lymphocyte that produces the antibodies for the specific antigen.
- At the same time cancer cells are grown onto a medium.
- The lymphocytes are harvested from the mice.
- The cancer cells and lymphocytes are fused together to produce a hybridoma cell.
- These hybridoma cells divide and make antibodies against that specific antigen, known as monoclonal antibodies.
What are 2 uses of monoclonal antibodies?
- They can detect and bind onto: platelets, cancer cells, hormones, enzymes and antigens.
- They can detect and treat cancer.
How can monoclonal antibodies treat cancer?
Radioactive monoclonal antibodies can bind onto cancer cells in the body using a PET scan to detect the location of cancer cells. They can also destroy cancer cells by recognising the antigens, binding onto them and then killing the cancer cells.
What is asexual reproduction? (6 points)
- Done by some animals such as invertebrates (insects) and some plants.
- Does not involve gametes, only 1 parent.
- Offspring inherits characteristic from one parent.
- No variation since offspring is genetically identical to parent (clone).
- Involves only mitosis.
- Much faster than sexual reproduction.
What is sexual reproduction? (6 points)
- Done by most animals and plants.
- Involves gametes (egg cells, sperm cells, pollen grains).
- Offspring inherits characteristics from both parents.
- Leads to variation, meaning organisms have different characteristics and allows them to survive in different/new conditions.
- Involves meiosis and mitosis.
- Slower than asexual reproduction.
How is a zygote created?
When the sperm cell fertilizes the egg cell.
How does a zygote become an embryo?
It undergoes mitosis.
What is a genome?
The DNA of an organism.
What is carried by the DNA?
Instructions for all the proteins the body needs to make.
What is the polymer of proteins?
Amino acids.
What happens during the first stages of meiosis?
Prophase I: Chromosomes condense and coil to become visible, then pair up to form homologous pairs. The pairs cross over, exchanging genetic material.
Metaphase I: Spindle fibres form and attach on the centromere and chromosomes line up as homologous pairs in the middle of the cell.
Anaphase I: Spindle fibres contract separating the pairs and each chromosome moves to opposite sides of the cell.
Telophase I: Nuclear membrane reforms and chromosomes un-condense and uncoil.
Cytokinesis: Cell divides forming two cells.
What happens during the second stages of meiosis?
Prophase II: Chromosomes condense and coil to become visible.
Metaphase II: Spindle fibres form and attach on the centromere and chromosomes line up in the middle of the cell.
Anaphase II: Spindle fibres contract pulling the sister chromatids apart, breaking the centromere and chromatids move to opposite sides of the cell.
Telophase II: Nuclear membrane reforms and chromosomes un-condense and uncoil.
Cytokinesis: Cell divides and forms 4 haploid, non-identical daughter cells.
What is in the nucleus of a cell?
Chromosomes that carry genes.
What is genetic code?
The instructions that tell the cell what to do, given by the DNA.
What does the DNA do?
It is responsible for the making of the cell and tells the cell to make particular proteins.
What is the DNA backbone made of?
Sugar (deoxyribose) and phosphate groups.
How are the bases in pairs connected?
Weak hydrogen bonds - A=T C≡G
