biology

• chromosomes:

  -contain genetic information

  -these chromosomes carries a large number of our genes

  -23 pairs

  -46 in total
• growth and replication in cell cycle:

  -before it divides the cell needs to grow and increase the amount of sub cellular structures.

  -it then duplicates its DNA.

  -the DNA is copied and forms chromosomes.
• mitosis in the cell cycle:

  -when DNA has been copied the cells ready for mitosis

  -chromosomes line up in the centre of a cell and cell fibres pull them apart. the two arms of each chromosome go to opposite ends of the cell

  -membranes form around the chromosomes and become a nuclei

  -the nucleus has divided and the cytoplasm/cell membrane divide

  -the cell has now produced two new identical daughter cells
• osmosis:

  -is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
• osmosis practical:

  1. cut up a potato into identical cylinders and get some beakers with different sugar solutions. one should be pure water and the other should be a very concentrated sugar solution.
  2. measure the mass of the cylinders then leave one cylinder in each beaker.
  3. take them out, dry them with paper towel and measure the masses again
  4. if they have drawn water by osmosis, they'll have increased in mass.
• osmosis practical:

  dependent variable: chip mass

  independant variable: concentration of the sugar solution
• active transport:

  -is substances that are absorbed again a concentration gradient.

  -we have a lower concentration in our gut but have a higher concentration of nutrients in the blood

  -when there's a higher concentration of glucose and amino acids in the gut they diffuse naturally into the blood

  -can be transported to cells where its used for respiration
• Gas exchange the job of the lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it.

  to do this, the lungs contain millions of little air sacs called alveoli which is where gas exchange taxes place.
• alveoli's are specialised to maximise diffusion of oxygen and carbon dioxide by:

  -an enormous surface area

  -moist lining to dissolve gases

  -very thin walls

  -good blood supply
• in the underneath of the leaf is an exchange surface. ones called the stomata which carbon dioxide diffuses in, and oxygen/water vapour diffuse out through the stomata.
• stomata size is controlled by the guard cells. these close if the plant is losing more water faster than is being replaced by roots.
• digestive enzymes:

  -amylase breaks down starch (found in salivary glands, pancreas, small intestine)

  -proteases convert proteins into Amino Acids (found in stomach, pancreas, small intestine)

  -lipases convert lipids into glycerol and fatty acids (found in pancreas and small intestines)
• bile is produced in the liver and is stored in the gall bladder before its released into the small intestine.
• pH of enzymes:

  -if starch is present: iodine solution will change from browny/orange to blue/black
• 1)tongue: produce amylase enzyme in saliva.

  2) goes to stomach where it pummels food and produces protease. it produces hydrochloric acid to kill bacteria and to give the right pH for the protease.

  3)goes to the liver where bile is produces. this neutralised the stomach acid.

  4)its transferred to the gall bladder where bile is stopped before its released into small intenstine.

  5) after the gall bladder, the pancreas produces protease, amylase and lipase. it releases these into the small intestine.
• digestive system continued:

  6) small intestine produces enzymes to complete digestion. this is where digestive food is absorbed

  7) large intestine has excess water absorbed form food
• circulatory system:

  -right ventricle pumps deoxygenated blood to the lungs to take in oxygen. the blood then returns to the heart.

  -the left ventricle pumps oxygenated blood around all the other organs of the body. the blood gives up the oxygen at the body cells and deoxygenated blood returns to the heart.
• the heart:

  -the heart has valves to make sure that blood flows in the right direction (prevent backflow)

  -blood flows into the atria from the vena caca and pulmonary vein.

  -the atria contract pushing blood into ventricles.

  -ventricles contract forcing blood into pulmonary artery and aorta, and out of the heart

  -the blood then flows to organs through arteries and returns through veins.

  0cycle repeats.
• what do stents do?


  stents keep our arteries open. these are tubes that are inserted inside arteries in order to keep them open to make sure blood can pass through the hearts muscles.
• coronary heart disease is when the coronary arteries that supply blood to the muscles of the heart, gets blocked by layers of fatty materials that build u. this causes arteries to become narrow so blood flow is restricted and there's less oxygen.
• problems with stents:

  can have a risk of infection from surgeries.

  people an also develop blood clots near the stent
• what are statins?


  statins are a drug that can reduce the amount of bad chlorestrol present in the bloodstream. this can slow down the rate of fatty deposits forming.
• statins advantages?


  -can reduce strokes, coronary heart disease and heart attacks

  -increase the amount of beneficial cholesterol

  -can prevent other diseases
• statins disadvantages?


  -long term drug that needs to be taken regularly.

  -cause negative side effects such as kidney failures

  -effect isn't instant and can take time to kick in.
• artificial hearts:

  -is a mechanical device that pumps blood for a person whose own heart has failed. this can be given by a donor.

  -the main advantage is that they're less likely to be rejected by an individuals immune system.

  -made of metals or plastics so the body doesn't recognise them as an 'attack'
• artificial hearts disadvantage:

  -surgery can lead to bleeding and infections.

  -dont work as well as healthy natural hearts.

  -parts of the heart can wear out or electrical motor can fail

  -blood doesn't flow smoothly which can cause blood clots and strokes.
• communicable disease :

  is a disease that can spread from person to person or between animals and people. this can be caused by bacteria, viruses, parasites and fungi. these are often known as contagious or infectious diseases.
• non-communicable disease:

  are those that cannot spread between people or between animals. these genuinely last a long time and get worse slowly.
• CANCER:

  -is caused by uncontrolled cell growth and division, this is uncontrollable
• benign cancer: this is where the tumour grows until there's no available room. this tumour stays in one place rather than invading other tissues. this type isn't normally dangerous and it is not cancerous.
• malignant cancer: this is where the tumour grows and spreads to healthy tissues. cells can break off and spread to other parts of the body by travelling in the bloodstream. This can cause secondary tumours. these are dangerous and fatal.
• risk factors of cancer?


  -smoking (lung cancer)

  -obesity (liver/kidney cancer)

  -UV exposure (skin cancer)

  -viral infections (e.g. unprotected sex)
• plant cells tissues and organs:

  epidermal tissue- covers the whole plant

  palisade mesophyll tissue- part of the leaf where photosynthesis occurs

  spongy mesophyll tissue- in the leaf and contains big air spaces to allow gases to diffuse (in and out)

  xylem/phloem - transport water, minerals and food around the plant

  meristem tissue- in growing tips of shoots/roots and can differentiate into different types of plant cells.
• structures of the leaf and functions:

  -epidermal tissues have a waxy cuticle to reduce water loss

  -upper epidermis is transparent so light can pass through.

  -palisade layer, has lots of chloroplasts where they can get light

  -xylem/phloem deliver nutrients to the entire leaf and take away glucose

  -tissues are adapted for efficient gas exchange

  -lower epidermis has little holes (stomata) which lets CO2 diffuse.
• what is transpiration?


  is the loss of water from the plants... this is caused by evaporation and diffusion off water from a plants surface. this normally happens in the leaves. the evaporation creates a slight shortage of water in the leaf so more water is drawn up from the rest of the plant through xylem vessels..

  this in turn means more water is drawn up from the roots and so there's a constant transpiration stream of water through the plant
• phloem tubes transport food....

  -made of columns of elongated living cells with small pored in the end walls to allow cell sap to flow.

  -they transport food substances (mainly sugar) made in the leaves to the rest of the plant for immediate use or storage.

  -the transport goes both ways.

  THIS IS CALLED TRANSLOCATION
• xylem tubes carry water up....

  -made of dead cells joined end to end with no walls between them and a whole down the middle. these are strengthened by lignin.

  -they carry water/mineral ions from roots to the stem and leaves

  -the movement of water from the roots, through the xylem and out of the leaves.
• transpiration is affected by:

  -light intensity

  -temperature

  -air flow

  -humidity.
• pathogens:

  -are microorganisms that enter the body and cause disease.

  -they cause communicable diseases
• bacteria- are very small cells which reproduce rapidly inside your body. they can make you feel ill by producing toxins that damage cells and tissues.