B3 Topic One - Control Systems

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  • Created by: Bethfr
  • Created on: 19-02-13 15:43


Excretion organs. Perform 3 main roles of removal of urea (produced in liver from breakdown of excess amino acids), adjustment of ion levels and water content of blood. Done by filtration under high pressure, reabosrbing useful thing. End product - urine.

Nephrons are the filtration units.

Ultrafiltration: High pressure squeezes water, urea, ions and glucose out of blood into bowmans capsule. Glomerulus and bowmans capsule filter only small molecules, so proteins and blood cells remain in bloood.

Reabsorption: Liquid flows along the nephron. Glucose is selectively reabsorped back into blood against concentration gradient. Water is selectively reabsorbed by ADH level.

Release of wastes: urea and excess water continue out of nephron, into ureter down to bladder and released as urine through urethra.

Water content is controlled by negative feedback which keeps it at a norm just like hormones in the menstrual cycle. Brain monitors water content of blood and instructs pituitary gland on how much ADH to release.

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Alternatives to normal kidneys

Dialysis filters blood mechanically, but has to be done regularly to keep the substances at the right level, and remove necessary waste.

Dialysis fluid has the same amount of salt and glucose as blood plasma so they arent removed from the body. The barrier in the dialysis machine is partially permeable, allowing small molecules like water and ions, but not big ones like proteins and blood cells, just like the membranes in the kidneys.

Kideny transplants cure kidney disease and are only cure. However, the new kidney can be treated by the body as a foreign body and attacked by antibodies - rejected. This can be prevented by getting a closely matching tissue type donor. Or anti-rejection drugs which suppress the immune system so it wont attack.

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Reproductive cells

Eggs main role: to carry the female DNA and nourish the developing embryo in early stages:

- Contains nurtients in cytoplasm to feed the embryo

- Membrane changes structure straight after fertilisation to prevent any more sperm getting in so the offspring has the right amount of DNA

- Haploid nucles so the embryos cells will have the right number of chromosomes.

Sperms role: to transport the male DNA to the eggs so the DNA can combine

- Long tails (flagellum) for swimming

- Mitochondria in middle section to provide energy from respiration for distance of swim

- Acrosome at head which contains enzymes to digest way through egg membrane

- Haploid nucleus so embryo has right number of chromosomes

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The Menstrual Cycle

Stage 1 - Bleeding starts Day 1. Uterus lining breaks down and released (menstruation)

Stage 2 - Lining of uterus builds up again Day 4 - 14, into a thick spongy layer of blood vessels ready to recieve a fertilised egg

Stage 3 - Egg is released by ovulation from ovary, day 14.

Stage 4 - Lining maintained for 14 days until day 28. If no fertilised egg recieved then the process restarts. If fertilised egg recieved then level of progesterone stays high to maintain lining during pregnancy. Blood vessels - blood supply - let placenta develop.

Follicle Stimulating Hormone - causes a follicle (egg and surrounding cells) to mature in one ovary at a time. Stimulates oestrogen production.

Oestrogen - Causes uterus lining to thicken + grow. A high level stimulates LH surge.

Luteinising hormone - LH surge stimulates ovulation - follicle ruptures, egg released. Stimulates remains of follicle to become a corpus luteum, which secretes progesterone.

Progesterone - Maintains uterus lining. Inhibits LH ad FSH production e.g. during pregnancy. Levels fall - lining breaks down, FSH increase and process restarts.

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Fertility Treatments

- Hormone injection of FSH and LH to stimulate egg release if these hormones are too low.

However, doesnt always work, and repeats can be expensive. Too many eggs may be stimulated - multiple pregnancies.

- IVF - collected egg and sperm, implanting back when embryos. FSH and LH given beforehand to stimulate egg production so more than one can be collected.

Some womens can have bad recation to hormones. More than one reimplanted embryo can grow into a baby - unwanted multiple pregnancy

- IVF with donated eggs

Can stop the passing on of genetic disordrs from mother YAY. But can be emotionally difficult knowing there is a different genetic mother.

- Surrogacy with either egg and sperm from couple or donor

Allows a woman to have a child if she cant become pregnant or pregnancy too risky. However, surrogate mother is legal mother until adopted - may decide to keep.

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23rd pair decides gender. Either XX (f) or XY (m).

Y chromosome causes male characteristics. XX combination causes female.

When making sperm, X and Y chromosomes in a body cell are drawn apart in first division of meiosis. 50% chance sperm gets X/Y. Same with eggs, but always X as XX.

gametes = sex cells. Either X or Y.

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Sex Linked Genetic Disorders

If an allele for a characteristic is located on the sex chromosome (X/Y) it is sex linked.

Y chromosome smaller than X, so carries less genes - most genes carried on X only.

Men are more likely to be sufferers of sex linked genetic disorders with recessive faulty alleles because as they only have one X chromosome, they only need the faulty allele to be present on the one X to be suffering.

Women need both X chromosomes to have the faulty recessive allele to be sufferers, but if they have it on one then they are carriers

Colour blindness is a sex linked genetic disorder caused by a faulty allele on X. It is recessive (obviously otherwise like everyone'd be colour blind). Women need 2 copies, men need 1 - more common in men. Haemophilia is the same - where blood wont clot properly when you cut yourself.

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Growth of Bacteria

Bacteria reproduce by splitting in two, doubling, at regular intervals - really fast. Infections can spread very quickly.

Til 19th century - diseases spontaneously generated. Then Louis Pasteur said microbes in air which cause disease + decay.

Experiment: 2 flasks, one curved neck - bacteria would settle in loop and not get through but air still could. Heated broth in both, left open - one stayed fresh (curved). Showed germs making it go off, not air.

He then invented pasteurisation - heating to 70ish degress and colling - kills of most germs.Now used to make milk safe - better than sterilising - severe heat - kills off everything, makes it taste funny. Reducing contamination by germs - aseptic technique.

Resazurin dye sensitive to oxygen. Microbes use up oxygen when they respire. More microbes - less oxygen around - greater colour change of resazurin dye.

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The Immune System

White blood cells travel in blood looking for infectious microorganisms - special type of white blood cells called B-lymphocytes:

Every pathogen hasunique molecules on the surface of its cells called antigens. B-lymphocytes produce proteins - antibodies - to bind and kill the invading pathogen. The produced antibodies are unique and work for that pathogen only. The antibody is then produced rapidly and flows all round the body to kill all simlar bacteria.

So obviously when a pathogen enters for the first time, the response is slow as only the B-lymphocytes can craft the cure - the antibody. Eventually they will produce enough antibodies to overcome the infection, but meanwhile the person will show the symptoms of the disease. After, a special B-lymphocyte is produced called memory lymphocytes which remain in the body for ages and remember the specific antibody. This means the person is now immune as they can respond quickly and more strongly to a second infection. This secondary response can often get rid of the pathogen before any symptoms are shown.

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Involves injection dead or inactive microorganisms into the body, which are antigenic (carry antigens) so the body makes antibodies to ttack them, which also triggers memory lymphocytes to be made.

Jenners experiment in 1796 triggered b-lymphocytes to produce antibodies against cowpox - cowpox has some of the same antigens as smallpox, so when so the response was much faster and better than it would have been when he was injected with smalllpox later.

Pros of immunisation: 

- epidemics can be prevented if large percent are immunised. Even non-immunised are less likely to get it as less people to pass it on.

- some diseases like smallpox have been virtually eradicated due to immunisation.

Cons of immunisation:

- Doesnt always give you immunity - doesnt always work

- People can have rare bad reaction to vaccine e.g. swelling or even fever/seizures

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Monoclonal Antibodies

Useful antibody - created by b-lymphocytes that dont divide very easily/quickly. Fuse it with a tumor cell (which divide lots) to make a hybridoma, which divide quickly to produce lots of identical antibodies - monoclonal antibodies. You can make them to bind to any antigen you want, so are really useful as will only work on your target.

Monoclonal antibodies are used in pregnancy tests, to identify the hormone found in urine when youre pregnant.

Where you wee has monoclonal antibodies to the hormone, with blue beads attached.

The test strip (bit that turns blue if preggo) has more antibodies to the hormone stuck down.

If youre pregnant: the hormone binds to the antibodies on the blue beads, and the beads and hormone are carried up the stick by the urine. The beads and hormone bind to the antibodies on the test strip, and get stuck, turning it blue.

If youre not pregnant: the urine travels up the stick along with the blue beads, but there is no hormone - nothing to stick the blue beads down with, so there is no colour change

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Monoclonal Antibodies cont.

Different cells have different antigens on their surface - you can make monoclonal antibodies that bind to specific cells. Cancer cells have unique antigens on their surface - called tumour markers. You can make monoclonal antibodies that bind to tumour markers.

Using monoclonal antibodies to diagnose cancer by...

Label antibody with a radioactive element. Give through drip into bloodstream. When the antibodies come into contact with cancer cells, they will bind to the tumor markers. Take a photo of the body with a camera that detects radioactivity. Cancer cells location = bright spot.Can see where, size, if its spreading.

Using monoclonal antibodies to target drugs to cancer cells by...

Attach an anti cancer drug to the antibody. Give through drip. Antibodies will only bind to tumour markers so will only target specific cells - kills cancer cells ONLY - leaving normal cells near tumour healthy - unlike some other drugs/radiotherapy. Less side effects :)

Blood clot - proteins in blood join together to make a solid mesh. Monoclonal antibodies developed to bind to this. Attach a radioactive element, give through drip. Photgraph using camera that picks up radiation - can get rid of potentially harmful blood clots.

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Drugs from plants and plant diseases

Plants produce chemicals to defend against pests + pathogens. Some of these chemicals can be use to cure or, relieve syptoms of, human disease. e.g.

Aspirin - treat pain and lower fever. Developed from chemical found in leaves and bark of willow tree.

Taxol - anti cancer drug. Bark of Pacific Yew Tree. Discovered when scientists were screening many plants looking for potential treatments.

Pests + pathogens can massively reduce crop yields

Insects e.g. fruit flies ruin fruit crop. Weeds nearby compete for nutrients in soil: plant doesnt grow as well so wont produce as much food (crop yield). Pathogens take energy from host plants, or energy is used to replace parts killed by pathogen - less energy on creating crop. 

Pests add to food production cost - pesticides, or disease/insect resistant crops. Also, if they dont produce enough crop, the demand is larger than amount, so price goes up.

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Daily Rhythms

Plants are photoperiodic - respond to changes in day length - amount of light and dark in a 24hr cycle. Plants only germinate, grow or flower with certain amount of light and dark, ensuring they grow or reproduce at the best time of year for them. 

Long day plants (spinach) flower when days at least a length so flower near midsummer. Short day plants (primroses) flower when the days less than a length so they flower in early spring/autumn. Others use incr. day length to tell its far enough from winter for to grow - not killed by frost immediately. Some only germinate with long days - warmest.

Circadian rhythms - biological processes that follow 24hr cycle - chemical patterns, patterns of behaviour, physiological patterns. Controlled internally but can be influenced by environmental factors.

In animals: Sleep patterns:master clocks gets info about light intensity from eyes, so then controls production of melatonin - sleepy. Regular sleep patterns good for health and makes you feel awake at the right times. Master clock then controls ADH production - increases at night so sleep isnt interrupted.

In plants: Flower opening: respond to light intensity so only open when creatures that pollinate them are active e.g. tobacco flowers - moths - night

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What exam board is this,

(Very good notes!)



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