| What are Prokaryote & Eukaryote Cells? | Prokaryote - single celled organisms (bacteria cells)
Eukaryote - organisms made up of eukaryotic cells (animal, plant cells) |
| What are the 5 Animal cell Sub-cellular structures? | 1) Nucleus - contains genetic material that controls cells activities
2) Mitochondria - where most reactions for aerobic respiration happens
3) Cytoplasm - gel-like substance where most chemical reactions happen contains enzymes (that control chemical reactions)
4) Cell membrane - Holds cell together, controls what goes in and out
5) Ribosomes - where proteins are made |
| What are the 3 (Additional) Plant Cell sub-cellular structures? | 1) Rigid Cell wall - Made of cellulose, supports & strengthens the cell
2) Chloroplasts - Where photosynthesis happens, contain (green) chlorophyll which absorb light
3) Permanent Vacuole - Contains cell sap, weak solution of sugar & salts |
| What are the 5 Bacteria Cell sub-cellular structures? | 1)Cell membrane
2)Cell wall
3) Cytoplasm
4)Circular DNA strand
5)Plasmid |
| Whats the Microscopy Equation? | Microscopy = image size ÷ real size |
| PRACTICAL: (Microscopy) Plant / Animal Cell | 1) Add a drop of water to clean slide
2) Peel off epidermal tissue from this layer / Remove cells from inside cheek with cotton bud
3) Use tweezers - place epidermal tissue into water on slide / Smear cotton bud onto slide
4) Add drop of iodine solution / Methylene blue (it's a stain & will make cell parts more obvious)
5) Place cover slip gently with forceps, avoid air bubbles (they'll obstruct view of your specimen) |
| PRACTICAL: Microscopy | 1) Clip slide onto stage
2) Select lowest power objective lens
3) Use coarse adjustment knob (to move stage just below objective lens)
4) Look down eye piece, use coarse adjustment knob to lower stage until image's in rough focus
5)Adjust focus w/ fine adjustment knob to get a clear image of whats on slide
6) If you need a greater magnification, swap to a higher objective lens and refocus |
| Define Differentiation | The process by which a cell changes to become specialised for its job |
| Whats the 2 Main Uses of Differentiation? | Repairing and replacing cells (skin or blood cells). Cells differentiate to develop features that enable them to fulfil specific roles |
| 1- Function and Features: Sperm Cells | FUNCTION: get male DNA to Female DNA
- long tail and streamlined head to help it swim
- Lots of mitochondria to provide energy
- Enzymes in its head, help it digest into egg cell membrane |
| 2- Function and Features: Nerve Cells | FUNCTION: carry electrical signals from one part of the body to another
- Are long, to carry more distance
-Have branched connections at their ends to connect to other nerve cells |
| 3- Function and Features: Muscle Cells | FUNCTION: contract quickly
- Are long, so have space to contract
- contain lots of mitochondria, to provide energy needed to contract |
| 4- Function and Features: Root Hair Cells | FUNCTION: absorb water and mineral ions
- Are long, giving plant big surface area to absorb water and mineral ions from soil |
| 5- Function and Features: Phloem & Xylem Cells | FUNCTION: transport substances like food and water around the plant
- Are long and joined end to end to form tubes
- Xylem are hollow in centre, so water can flow through
- Phloem have few sub-cellular structures, so food can flow through |
| What are Stem Cells? | A cell which has not undergone differentiation |
| Embryonic and Adult Stem cells | EMBRYONIC STEM CELLS:
1) An embryo develops from a fertilised egg (at the early stage of development the cells in the embryo are stem cells)
2) Cells are then removed from the embryo - Embryonic stem cells (they'll differentiate into any type of cell
3) Difficult to obtain and raise ethical challenges
ADULT STEM CELLS:
1) Found in: brain, eyes, blood, heart, liver, bone marrow, skin and muscle
2) Can only differentiate into related cell types (e.g. bone marrow cells can differentiate into blood cells and cells of the immune system)
(3) Use patients own stem cells, therefore they're genetically identical and less likely to get rejected |
| Plant Stem cells | 1) Found in the meristem region if the plant (mainly near the shoot tip and the root tip)
2) Can differentiate into any cell at anytime during the plants life
3) In a growing shoot new cells are being produced near the tip but as they become older and further away from the tip they become differentiated - and enlarge and develop vacuoles |
| Specialised Cells in Animals | View Image: |
| Specialised Cells in Plants | View image: |
| How does cloning in plants happen? | 1)Meristematic cells are removed and grown in tissue culture - the culture medium contains: agar to provide support and water for growing cells, nutrients and plant hormones to stimulate growth and cell division |
| Human Stem Cell Uses | 1) Adult/Embryonic Stem Cells: can be used to replace damaged or destroyed cells:
- in type 1 diabetes
- in cases of multiple sclerosis (which can lead to paralysis)
- in cases of spinal cord or brain injury (that have lead to paralysis)
3) Adult Stem cells: Differentiate in to a narrower range of cell types
- E.g. Bone marrow transplants are carried out: in case of blood cell cancer (like leukaemia and lymphoma) or when blood cells have been destroyed by cancer treatment |
| Therapeutic Cloning | View Image: |
| Benefits of Stem Cells in Medicine | Stem cells have great potential, in treating patients with currently untreatable conditions, growing organs for transplants, and research |
| CLINICAL ISSUES of Stem Cells in Medicine | - Difficult to find suitable donors
- Difficult to obtain & store
- Cultured stem cells could be contaminated with viruses |
| ETHICAL ISSUES of Stem Cells in Medicine | - Is it right to create embryos for therapy, and destroy them?
- Embryos can be viewed as commodities, and not as an embryo that could develop into a person
- At what stage of its development should an embryo be regarded as, and treated as a person |
| SOCIAL ISSUES of Stem Cells in Medicine | - Educating the public about what stem cells can, and can't do, is important
- Whether the benefits of stem cell use outweigh the objections
- Patients could be exploited by paying for expensive treatments and being given false hope of a cure as stem cell therapies are only in their developmental stages |
| Describe the Digestive Enzymes (involved in Chemical Digestion) | Enzymes are Biological Catalysts. They break down nutrients into small, soluble molecules that can be absorbed. |
| Where are the Digestive Enzymes Found? | 1) Proteases catalyse the breakdown of proteins into amino acids in the stomach and small intestine
2) Lipases catalyse the breakdown of fats and oils into fatty acids and glycerol in the small intestine
3) Amylase catalyses the breakdown of starch into maltose in the mouth and small intestine
4) Maltase catalyses the breakdown of maltose into glucose in the small intestine |
| What Factors effect Enzymes | - PH, different enzymes work best at different pH values
- Temperature (work best at 37°C) |
| What happens when a cell becomes cancerous? | When a cell becomes cancerous, it begins to grow and divide uncontrollably. New cells are produced – even if the body does not need them
- A group of cancerous cells produces a growth called a tumour.
- Cancer cells are undifferentiated – they do not carry out their normal function |
| 2 Types of Tumours | View image: |
| Describe how Secondary Tumours form | 1) Tumour secretes chemicals
2) The chemicals stimulate the blood vessels to grow (the blood vessels grows around the tumour)
3) Cancer cells detach from the tumour and are transported in the blood
4) A malignant cell squeezes through a blood capillary wall
5) The cell divides - a secondary tumour starts to grow |
| State 3 Life Style Factors that may cause Cancer | 1) viruses linked with cancer, such as the human papilloma virus (HPV), being spread from person to person through sexual intercourse
2) the chemical carcinogens in cigarette smoke increasing the risk of lung cancer
3) alcohol intake is linked with certain cancers
4) exposure to ultraviolet radiation, part of which is ionising, during sunbathing or outdoor activities, leading to the development of skin cancers
5) diet, including fat and salt intake, increases the risk of cancer |
| State an Industrial and environmental factor at work that may cause Cancer | 1) exposure to ionising radiation increases the risk factor
2) exposure to chemical carcinogens |
| What are Carcinogens? | Chemical and other agents that can cause cancer
- Carcinogens cause cancer by damaging DNA.
- Carcinogens cause mutations to occur. A single mutation will not cause cancer – several are required. For this reason, we are more likely to develop cancer as we get older |
| How was Penicillin Found? | Sir Alexander Fleming discovered penicillin from the Penicillium mould. |
| Plant Extracts of Drugs | ASPIRIN:
Ancient Greeks used willow bark to cure fevers and pains
- It was later discovered that the active ingredient was salicylic acid
- Salicylic acid was later modified into aspirin which is less irritating to the stomach
DIGITALIS:
- Heart drug
- Extracted from foxgloves |
| Thalidomide (Discovery of Drugs) | HISTORICALLY:
- Thalidomide was developed as a sleeping pill and was also thought to be useful for easing morning sickness in pregnant women
- Caused unexpected serious damage to unborn babies in 1950-60's (especially if it had been taken in the first 4-8 weeks of pregnancy). More than 10,000 babies were affected around the world. Also caused babies legs/arms to be very short.
- As a result of this disaster, thalidomide was banned & drug testing was also made more rigorous than before
TODAY:
-Thalidomide is now used as a treatment for leprosy and bone cancer
- Its use is heavily regulated to prevent a repeat of the problems it caused in the last century |
| Why are New Medical Drugs Tested? | To ensure that they work, and are safe, before they can be prescribed. They are tested for:
1) Safety - This is important as some drugs are toxic, and have other side effects that might be harmful to people
2) Effectiveness - This is also known as efficacy, and checks how well the drug cures the disease, or improves symptoms
3) Dosage - This varies, and has to be closely controlled, as too high a concentration might be toxic |
| What are the 3 main Stages of Drug Testing? | 1) STAGE 1: Drugs are tested in Laboratories using computer models and skin cells grown using human stem cells. Tests: efficacy and possible side effects. Many substances fail this first test of a preclinical drug trial because they damage cells or do not seem to work
2) STAGE 2: New medicines tested on animals (In UK), illegal to test cosmetics and tobacco products on animals. Typically involves giving a known amount of substance and monitoring carefully for any side-effects
3) STAGE 3: Human clinical trials. Tested on healthy volunteers to check that they are safe, then tested on people with the illness to ensure that they are safe and that they work. Low doses of the drug are used initially, and if this is safe the dosage increases until the optimum dosage is identified |
| What are Monoclonal antibodies, Antibodies & Antigens? | 1) Monoclonal antibodies - are identical copies of one type of antibody
2) Antibodies - are proteins produced by a type of white blood called lymphocytes
3) Antigens - are proteins found on the surfaces of pathogens |
| How does the body Respond to Pathogens? | 1) Lymphocytes recognise these antigens as foreign and attack them by producing antibodies
2) Antibodies bind to specific antigens on pathogens and are merged tightly together - this makes them easier to identify and deal with
NOTE: Scientists discovered that we could make antibodies to bind to antigens on other substances, and not just those on pathogens |
| How are Monoclonal Antibodies Formed | 1) An antigen is injected into a mouse
2) The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen
3) Spleen cells which produce the lymphocytes are removed during a small operation
4) The spleen cells are fused with human cancerous white blood cells called myeloma cells to form hybridoma cells which divide indefinitely
5) These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen |
| 3 Other Uses of Monoclonal Antibodies | PREGNANCY TESTS:
1) Monoclonal antibody designed to bind with a hormone called HCG (found only in the urine of pregnant women) are attached to the end of the stick which woman urinates on.
2) If pregnant, HCG will bind to the monoclonal antibodies on the test stick, and a change in colour or pattern on the stick will indicate pregnancy
CANCER IDENTIFICATION:
1) Cancerous cells have antigens. Monoclonal antibodies can be designed to bind specifically with these antigens
2) When injected into a person's body, the monoclonal antibodies will bind with these cancer cells and clump them together making it easier to identify a cancerous tumour. The MA's can: carry drugs that have been attached to them, to the tumour OR encourage your immune system to attack the cancer cells directly
OTHER DIAGNOSTIC USES:
Monoclonal antibodies are also used in a similar way to identify and diagnose infections, such as HIV and AIDS, herpes and chlamydia. Some monoclonal antibodies have been attached to dyes that will glow fluorescent under UV light. This can make disease identification much easier |
| What is the definition of osmosis? | Osmosis is the diffusion of water molecules, from a region where the water molecules are in higher concentration, to a region where they are in lower concentration, through a partially permeable membrane |
| Osmosis across living cells | - Cells contain dilute solutions of ions, sugars and amino acids.
- The cell membrane is partially permeable.
- Water will move into and out of cells by osmosis. |
| Osmosis in: Plant Cells | - Root hair cells, if the soil is wet or moist, will also take up water by osmosis
- Leaf cells of land plants, unless it is raining or the humidity is high, will have a tendency to lose water
- Plant cells have a strong cellulose cell wall which is fully permeable and supports the cell, stopping it from bursting as it gains water
- Aquatic, freshwater plants placed in the sea, or a seaweed in a rock pool where the water evaporated in the Sun, would also lose water by osmosis |
| Osmosis in: Animal Cells | 1) Animal cells also take in and lose water by osmosis. They do not have a cell wall, so will change size and shape when put into solutions that are at a different concentration to the cell contents. Red Blood cells can:
- lose water and shrink
- gain water, swell and burst in a more dilute solution
2) In animals, the concentration of body fluids – blood plasma and tissue fluid – must be kept within strict limits, if cells lose or gain too much water by osmosis, they do not function efficiently |
| PRACTICAL: Osmosis | 1) Prepare a range of sucrose (sugar) solutions - could be sodium chloride (salt). Measured in 'mol dm-3'. E.g. 0.2 mol dm-3 to 1.0 mol dm-3.
2) Set up a series of boiling tubes with each of these solutions. 1 will contain distilled water (0.0 mol dm-3 of sucrose) - it'll act as the control in the experiment. Make sure each tubes concentration is labelled
3) Prepare blank results table. Make sure potatoes mass' are not mixed up when recording them. Each cylinder will have a different mass before and after investigation
4) For each sucrose concentration, repeat the investigation for several potato cylinders - makes experiment repeatable as not all potatoes behave in the same way, also means anomalies can be identified and ignored when calculating mean |
| Things to consider (Osmosis Practical) | RISKS:
- Make sure that the potato is placed on a ceramic tile when using the cork borer – do not cut the potato cylinders towards your hand.
- Care must be taken when using the scalpel.
- Wear eye protection when using chemical solutions.
This experiment shows the effect of osmosis on plant tissue. The cylinders will decrease or increase in mass if they lose or gain water by osmosis. Effects on plant tissues at a cellular level can be observed using a microscope. May be done on different plants: onions, beetroot - It is easy to see the process of plasmolysis in beetroot because the cell sap is red |
