Tissues, Organs and Systems - In most organisms, cells are arranged into tissue ( a tissue is a group of cells which have a similar structure snd function, they all work together to do a job e.g epithelial tissue covers organs)
Organs are a group of different tissues which work together to perform a specific job. Each organ may contain several tissues (e.g the stomach is an organ which contains; muscular tissue that contracts to churn the contents, glandular tissue to produce digestive juices and epithelial tissue to cover the outside and the inside of the stomach.
Organs are organised into organ systems (groups of organs working together to do a particular job) EG digestive system. - organ work together to digest and absorb food.
Lots of organ systems work together to make an organism

Specialised cells - As an organism develops, cells differentiate to form different types of cells (become specialised). Most types of of animal cells differentiate at an early stage whereas many plant cells can differentiate through their lifetime. As a cell differentiates it may change shape and different sub-cellular structures develop to let it carry out a specific function.

Specialised animal cells include: sperm, nerve and muscle cells.

A sperm cell: Tail - to propel the sperm to fertilise the egg Mitochondria - sperm have many of these cell components, which are the major site of respiration, to provide energy for their journey. Nucleus - Contains only one set of the genetic material. Acrosome - contains enzymes to allow the sperm to penetrate the outer layer of the egg.

A motor neurone: Axon, sheath, cell body, dendrites

A muscle cell: Protein fibres (that contract), nucleus and mitochondria (for energy)

In plants, root hair, xylem and phloem cells are all specialised cells.

Xylem: xylem cells are arranged end to end but the end walls break down to form hollow tubes. The cell wall of the cells is strengthened by a substance called lignin.

A root hair cell: Lots of mitochondria for active transport of minerals and have long projection to increase the surface area to absorb water and minerals.

Phloem: The end walls of the cells allow sugars through but support the tubes. Phloem cells are arranged end to end into tubes. They also have companion cells.

Enzymes - are biological catalysts (speed up chemical reactions in living organisms. Properties include: Have large number of proteins, Have a space within the protein molecule called the active site, each enzyme catalyses a specific reaction, they work best at optimum (a specific temperature and pH level) Th lock and key theory is a model used to explain how enzymes work; the 'Key' (the chemical that reacts - substrate) fits into the 'Lock' (the enzymes active site)
High temperatures and extremes of pH make enzymes change shape (this is called Denaturing) The enzyme cannot work once it has been denatured, as the substrate can no longer fit into the active site.

Risk Factors - Non-communicable diseases are caused by the interaction of many factors (risk factors). They can be: -aspects of a persons life - substances in the persons body or environment (eg chemicals from smoking). sometimes there is a clear link between risk factor and getting a disease (eg obesity and type 2 diabetes). This doesn't mean that the risk factor causes the disease. Scientists look for a causal mechanism to prove that the risk factors aren't involved.

Diseases of the Heart - In coronary heart disease layers of fatty material build up inside the coronary arteries and narrow them. Treatments include: stents - to keep coronary arteries open and statins - to reduce the blood cholesterol levels and slow down the rate at which fatty materials build up. Sometimes, heart valves may become faulty, developing a leak or preventing the valve from opening fully. Faulty valves can be replaced using biological or mechanical valves.
For cases of heart failure: - a donor heart, or heart and lungs can be transplanted - artificial hearts can be used to keep patients alive while waiting for a heart transplant or to allow the heart to recover. Drugs such as clot-busting enzymes or warfarin are sometimes used to treat recovering patients, while statins can be given to lower cholesterol levels.

Health and Disease - Good health - a state of physical and mental wellbeing. A disease is caused by part of the body not working properly (this can affect physical and/or mental wellbeing) there are 2 types of diseases - 1-Communicable and 2- Non-communicable diseases. Non-communicable diseases cannot be spread between organisms whereas communicable diseases can be. Interactions between diseases include: - Viruses infecting cells can be the trigger for cancers, such as cervical cancer - Diseases of the immune system mean that an individual is more likely to catch infectious diseases eg people with HIV are more likely to get tuberculosis - Immune reactions triggered by a pathogen can cause allergies, such as skin rashes and asthma - If a person is physically ill, this can lead to depression and mental illness - Poor diet, stress and difficult life situations can increase the likelihood of developing certain diseases. Non-communicable diseases, such as HIV and diabetes, can change a person's life and cost countries large sums of money. About 10% of the health budget in Britain is spent on people with diabetes.

Cancer - is a non-communicable disease. Risk factors for cancer include: smoking, obesity, common viruses and UV exposure. Genetic risk factors include: some genes make the carrier more susceptible to certain types of breast cancer. Cancer is caused by uncontrolled cell division, this can cause tumours. 2 main types of tumours: 1- Benign (tumours do not spread around the body) 2- Malignant (tumours spread, in the blood, to different parts of the body where they form secondary tumours).

Water transportation - Water enters through soil (by root hair cells) by osmosis. Root hair, xylem and phloem cells are specialised to transport water, minerals and sugars around the plant. This water contains dissolved minerals. These are transported up the xylem vessels. At the leaves, most of the water will evaporate and diffuse out of the stomata (small pores) The loss of water from the laves is called transpiration (this helps draw water up the xylem vessels from the roots)

Factors that can affect the rate of transpiration: - An increase in temperature will increase the rate of transpiration as energy is transferred to the water to allow it to evaporate - Faster air flow will increase the rate as it will blow away water vapour allowing more to evaporate - increased light intensity will increase the rate as it will cause the stomata to open and - an increase in humidity will decrease the rate as the air contains more water vapour so the concentration gradient for diffusion is lower.

The role of the guard Cells is to open and close the stomata. At night the stomata are closed (this is because carbon dioxide is not needed for photosynthesis so closing the stomata reduces water loss). When water is plentiful, guard cells take it up and bend (this causes the stomata to open so gases for photosynthesis are free to move in and out of the stomata along with water from transpiration) When water is scarce, losing water makes the stomata change shape and close(this stops the plant from losing more water through transpiration)

Translocation - Phloem tissue transports dissolved sugars from the leaves to the rest of the plant. This movement of food through phloem tissue is called translocation. Phloem cells are adapted for this function.

Plant tissue
Epidermis - Covers the outer surfaces of the plant for protection
Palisade mesophyll - the main site of photosynthesis in the leaf
Spongy mesophyll - Air spaces between the cell allow gases to diffuse through the leaf
Xylem vessels - transports water and minerals through the plant, from roots to leaves. Also supports the plant
Phloem vessels - Transports dissolved food materials through the plant
Meristem tissue - Found mainly at the tips of the roots and shoots, where it can produce new cells for growth

Plant tissues are gathered together to form organs. The leaf is a plant organ. The structures of tissues in the leaf are related to their functions.

Examples of Plant Diseases - Like animals, plants can suffer from non-communicable diseases. They can be infected by a wide range of viral, bacterial and fungal pathogens as well as by insects. Tobacco Mosaic Virus is a widespread plant pathogen: - infects tobacco plants and many other plants, including tomatoes. - It produces a mosaic pattern of discolouration on the leaves, which reduces chlorophyll content and affects photosynthesis - It affects the growth of the plant due to a lack of photosynthesis.
Rose black spot is a fungal disease. aphids are small insects often known as greenfly or blackfly. They feed on the phloem taking sugars out from the plant. Non-communicable diseases include a range of deficiency diseases: - stunted growth (caused by nitrate deficiency because nitrates are needed for protein synthesis) - Chlorosis (caused by magnesium deficiency as magnesium ions are needed to make chlorophyll)

Plant Defences - Physical defences: - cellulose cell walls - tough waxy cuticle on leaves - layers of dead cells around stems (bark on trees)which fall off and take pathogens with them.
Chemical defences: - antibacterial chemicals (made by plants such as mint and witch hazel) - Poison to deter herbivores (made by plants such as tobacco, foxgloves and deadly nightshade)
mechanical adaptations: - thorns and hairs - leaves that droop or curl when touched - mimicry to trick animals into not eating them or not laying eggs on the leaves (eg the white deadnettle does not sting, but looks very similar to a stinging nettle)

Detecting and Identifying Plant Disease - Signs include: - stunted growth - spots on leaves - areas of decay (rot) - growths - malformed (abnormal) stems or leaves - discolouration - the presence of pests.
To identify the disease: - Consulting a gardening manual or website - taking infected plants to a laboratory to identify the pathogen - using testing kits (which contain monoclonal antibodies)

Developing New Drugs - New painkillers are developed to treat the symptoms of disease but they do not kill the pathogens - Antiviral drugs are needed that will kill viruses without also damaging the body's tissue - New antibiotics are needed as resistant strains of bacteria develop.
Drugs were extracted from plants and microorganisms: - Digitalis is a heart drug (from Foxgloves) - Aspirin is a pain killer (from willow) - Penicillin from penicillin mould.
New drugs have to be tested and trialled before being used. If a drug is found to be safe it is then tested on humans to test if it works and to find out the optimum dose. Double-blind Trials - some patients are given a placebo which does not contain the drug, and some are given the drug. - patients are randomly allocated to the two groups. - neither the doctors nor the patients know the groups.
New painkillers are developed to treat the symptoms of disease - they do not kill pathogens. New antiviral drugs are needed that they will kill viruses without damaging the body's tissues. This is not easy to achieve.

Monoclonal Antibodies - are produced from a single cell that has divided to make many cloned copies of itself. These antibodies bind to only one type of antigen, so they can be used to target a specific chemical or specific cells in the body. They are produced by combining mouse cells and a tumour cell to make a cell called a hybridoma.
Monoclonal antibodies can be used in different ways: - In pregnancy tests (to bind the hormoneHCG found in urine . during early pregnancy) - in laboratories (to measure the levels of hormones and other chemicals in blood or to detect pathogens) - in research (to locate or identify specific molecules in a cell or tissue by binding them together with fluorescent dye) - to treat some diseases (eg in cancer they are used to deliver a radioactive substance that stops the cells from dividing)
Unfortunately, monoclonal antibodies have created more side effects than expected, so they are not yet widely used.

The Immune System - If a pathogen enters the body, the immune system tries to destroy it. White blood cells help to defend against pathogens through: -phagocytosis (which involves the pathogen being surrounded, engulfed and digested) - the production of special protein molecules called antibodies which attach to antigen molecules on the pathogen -the production of antitoxins (which are chemicals that neutralise the poisonous effects of the toxins)

Boosting Immunity - If the same pathogen re-enters the body, the white blood cells respond more quickly to produce the correct antibodies. This quicker response prevents the person from getting ill and is called immunity. When a person has a vaccination, small quantities of dead or inactive forms of the pathogen are injected into the body. Vaccination stimulates the white blood cells to produce antibodies and to develop immunity. If a large proportion of the population can be made immune to a pathogen, then the pathogen cannot spread very easily.

Preventing Entry Of Pathogens - The body has a number of non-specific defences against disease. These are defences that work against all pathogens, to try and stop them entering the body.
Goblet Cell* (mucus emerging - sheet of mucus traps particles and bacteria - Cilia create a wave motion, which sweeps mucus along) Enzymes in tears destroy microorganisms The Nose traps particles that may contain pathogens
Glands in stomach wall - glands produce hydrochloric acid which kills bacteria in food Skin** Sebaceous gland produces sebum, which kills bacteria and fungi.

Viral Pathogens - Viruses reproduce rapidly in the body cells, causing damage to the cells. Measles is a disease caused by a virus: - Symptoms are fever and red skin rash - the virus is spread by breathing in droplets from sneezes and coughs - it can be fatal.
HIV: - causes AIDS - Spread by sexual contact or exchange of body fluids - at first causes a flue like illness - if untreated it enters the lymph nodes and attacks the body's immune cells -taking antiviral drugs can delay this happening.
Viruses can also cause plant diseases eg tobacco mosaic virus.

Bacteria Diseases - Bacteria can damage cells directly or produce toxins (poisons) that damage tissues. Salmonella is a type of food poisoning caused by bacteria: - the bacteria are ingested in food which may not have been cooked properly or may not have been prepared in hygienic conditions - the bacteria secrete toxins which cause fever, abdominal cramps, vomiting and diarrhoea - chicken and eggs can contain the bacteria so chickens in the UK are vaccinated against salmonella to control the spread.
Gonorrhoea is a sexually transmitted disease caused by bacteria: - spread by sexual contact - Symptoms are thick, yellow or green discharge from the vagina or penis and pain when urinating - It used to be easily with penicillin, but many resistant strains have now appeared - the use of barrier methods of contraception can stop the bacteria being passed on.

Pathogens and Disease - Pathogens are microorganisms that cause infectious (communicable) diseases. They may infect plants or animals. Can be spread by direct contact, Water or Air or Vectors (organisms that carry and pass on the pathogen without getting the disease). The spread of infectious diseases can be reduced by: - simple hygiene measures - destroying vectors - isolating infected individuals and giving people at risk a vaccination.

Protists and Disease - They are single-celled organisms. However unlike bacteria they are eukaryotic. Malaria is caused by a protist: -they use a particular type of mosquito as a vector - it is passed on to a person when they are bitten by the mosquito - Malaria causes sever fever, which reoccurs and can be fatal - one of the main ways to stop the spread is by stopping people getting bitten (kill the mosquitos or use mosquito nets).

Fungal Diseases - Rose Black Spot: - It is spread when spores are carried from plant to plant by water or wind. - Purple or black spots develop on the leaves which often turn yellow and drop off early. - The loss of leaves will stunt the growth of the plant because photosynthesis is reduced. - It can be treated by using fungicides and removing and destroying the affected leaves.

Converting Glucose - is produced during photosynthesis may be used by the plant during respiration to provide energy. It may change into products such as:- insoluble starch (which is stored in the stem, leaves or roots) - fats or oils (which is stored in the stem, leaves or roots) - cellulose, to strengthen the cell walls - proteins (which are used for growth and for enzymes)
To produce proteins from glucose, plants also use nitrate ions, which are absorbed from the soil.

Photosynthesis - CO2 + H2O ---(light)--- C6H12O6 +O2
Carbon Dioxide + Water ---(light)--- Glucose + Oxygen
To produce glucose molecules, energy is required. Reaction is endothermic (takes heat in) Energy is sunlight. It is trapped by the chlorophyll which is found in chloroplasts.