Biology 3

The Kidneys

-The kidneys are exretion organs. They perform 3 main roles-

• Removal of urea from the blood. 
• Adjustment of ion levels in the blood.
• Adjustment of water content in the blood. 
• Filter things out of the blood under high pressure,and then reabsorb useful things End product = urine.

Nephrons are the filtration units in the kidneys

• Ultrafiltration-high pressure built up=squeezes water, urea ions+glucose out of blood, into bowmans capsule. Glomerulus and BC act like filters=big molecules (proteins+blood cells) not squeezed out. 
• Reabsorption-All glucose selectively reabsorbed. moved out of nephron+back into blood against concentration gradient. Sufficient water reabsorbed(level of ADH). process is called osmoregulation.
• Release of wastes-urea+excess water not reabsorbed.out nephron-ureter-bladder-urethra(urine)

Water controlled by negative feedback(NF) system.

Amount of water reabsorbed in kidney nephron is controlled by anti-diuretic hormone(ADH).

Brain monitors water content of blood-instructs pituitary gland to release ADH into blood. Whole process controlled by neg feedback(changes in environment trigger response that helps the changes). So internal environment tends to stay around a norm. if water content gets too high or low NF will bring back to normal:

Too much water-brain detects this-pituitary gland releases less ADH-little ADH means kidney reabsorbs less water

Too little water-brain detects this-pituitary gland releases more ADH-ADH makes kidney reabsorb more water. 

Dialysis filters the blood mechanically. 

Patients with kidney failure can't filter blood properly-so use dialysis machine. Dialysis is done regularly to keep dissolved substances at right concentrations, and to remove waste. 

Dialysis fluid has the same concentration of salts+glucose as blood plasma(so those aren't removed from blood). 

The barrier is permeable to things like ions and waste substances,but not big molecules like proteins. So, the waste substances(e.g urea) +excess ions+ water from the blood move across the membrane into the dialysis fluid.

Kidney transplants- only cure for kidney disease. Healthy kidney usually transplanted from someone who died suddenly (e.g car crash). 

Donor kidney can be rejected by patient's immune system, precautions are taken:

• donor with closely matching tissue is chosen
• patient treated with drugs that suppress immune system, so it won't attack the transplanted kidney.

Sperm cells and egg cells are specialised for reproduction.

Egg cell- The main functions of an egg cell are to carry female DNA and to nourish developing embryo in early stages. 

• The egg contains nutrients in the cytoplasm to feed the embryo.
• straight after fertilisation, the eggs membrane changes its structure to stop any more sperm getting in-offspring have right amount of DNA.
• The egg contains a haploid nucleus. So when egg is fertilised, the resulting cell will have the right number of chromosomes. 

Sperm cell- main function is to transport male DNA to the female's egg so DNA can combine. 

• Sperm are small and have long tails (to swim to egg)
• lot of mitochondria in middle section to provide energy needed to swim this distance.
• have acrasome at front of head, where they store the enzymes they need to digest their way through membrane of an egg cell. 
• Sperm contain haploid nucleus- only have one copy of each chromosome. 

Stage 1: Day 1 is when bleeding starts. Uterus lining breaks down and is released.                   Stage 2: Lining of uterus builds up again,(day 4-14) into think layer of blood vessels ready to recieve fertilised egg.                                                                                                           Stage 3: Egg released from ovary (ovulation) around day 14.                                                   Stage 4: lining maintained for 14 days(until day28). no fertilised egg=lining starts to break down again and cycle starts over.

Menstrual cycle controlled by 4 hormones:

1) FSH(follicle-stimulating hormone)- causes follicle to mature in one of ovaries. Stimulates oestrogen production.

2) Oestrogen- causes lining of uterus to thicken and grow. A high level stimulates an LH surge.

3) LH(luteinising hormone)- surge stimulates ovulation at day 14-follicle ruptures+egg is released. Stimulates remains of follicle to develop into a structure called a corpus leuteum-which stimulates progesterone

4) Progesterone-Maintains lining of uterus. Prevents production of FSH and LH. When level of progesterone falls, and low oestrogen level, uterus lining breaks down. Low progesterone level causes FSH to increase, and it begins again. 

If woman becomes pregnant, the level of progesterone remains high to maintain lining of uterus during pregnancy. Uterus lining has thick layer of blood vessels-blood supply allows placenta to develop. Placenta supplies baby with oxygen, glucose and nutrients it needs to grow, and removes waste products. 

Hormones can be used to increase fertility

-Some women have low levels of FSH, so their eggs can't mature. Means no eggs are released and woman can't get pregnant. FSH and LH can be injected by women to stimulate egg production in ovaries. 

PROS: helps a lot of women to get pregnant.CONS:doesn't always work. Expensive. Too many eggs stimulated-multiple pregnancies. 

IVF- collects eggs from a woman's ovaries and fertilises them in a lab with man's sperm. Grown into embryos. Once embryos have slightly matured,1/2 are transferred to woman's womb. FSH and LH given before to stimulate egg production. 

PROS:gives infertile couple a child. CONS:strong reaction to hormones, increased risk of cancer, multiple births.

Egg donation- women who don't produce eggs use eggs from a donor, then use IVF.

PROS:allows couple to have a child, prevent risk of passing on genetic disorder from mother     CONS:emotionally difficult for family (child has different genetic mother)

Surrogacy- carries baby for another couple. If a woman can't get pregnant she may ask another woman to carry a baby for her. Woman who carries baby=surrogate mother. 

IVF used to produce embryo-either use egg+sperm from couple or donor egg+sperm. Embryo implanted into surrogate mother's uterus. 

After birth, surrogate mother gives baby to couple.

PROS: allows couple to have a child if the mum has medical problems that mean she can't become pregnant or if its risky to give birth.

CONS: surrogate mother is legally mother of child until child is adopted by the intended couple. She has right to keep child-may decide she doesn't want to give it away. 

Gender- Chromosomes determine whether you're male or female. 22 matched pairs of chromosomes in every human body cell, the 23rd pair are labelled ** or XY. These decide a person's gender. 

All men have an X and a Y chromosome:XY. The Y chromosome causes male characteristics.  All women have 2 X chromosomes: **. combination allows female characteristics to develop. 

When making sperm, X&Y chromosomes are drawn apart in first division in meisosis. 50% chance each sperm cell gets an X-chromosome and a 50% chance it gets a Y-chromosome. 

Genetic diagrams-Show possible combinations of gametes.                                                                                          

Genetic characteristics- A characteristic is sex-linked if the allele that codes for it is located on a sex chromosome. Y chromosome is smaller than the X chromosome and carries fewer genes. So most genes are only carried on X chromosome. 

Men only have one X chromosome, so often only have one allele for sex-linked genes. This means the characteristic of this allele is shown even if it is recessive. Makes men more likely to show recessive characteristics for genes that are sex-linked.

Disorders caused by faulty alleles located on sex chromosomes are called sex-linked genetic disorders. Colour blindness and haemophilia are examples.

A genetic diagram shows how colour blindness is inherited. it is caused by a faulty allele carried on X chromosome. Women need 2 copies of recessive allele to be colour blind, while men only need one copy. So colour blindess rarer in women than men.

Woman with only one copy of recessive allele=carrier of colour blindness. Means she isn't actually colour blind, but could pass the allele on to offspring.  

Reproduce fast- they split in 2, so number doubles at regular intervals.Their growth is EXPONENTIAL-only a handful at first, and then soon there are millions of them. This means an infection can develop really fast.

Pasteur- argued that there are microbes in the air which cause disease and decomposition. Carried out experiments. Went on to invent process of pasteurisation-heating something to around 70 degrees C, and then cooling it. This kills off most harmful germs, so product shouldn't make a person ill.

Any process that reduces contamination by germs is called an aseptic technique.

Pasteurisation is used to treat raw milk, to kill harmful bacteria and make it safe to drink. 

You can use resazurin dye to investigate microorganism growth. 

The immune system deals with infectious microorganisms

White body cells travel in the blood, looking for microorganisms. Some of them are a special type called B-lymphocytes. When these come across an invading microorganism, they produce antibodies: 

-Every pathogen has unique molecules on the surface of its cells. These molecules are called antigens. 

-When B-lymphocytes come across a foreign antigen(like on surface of bacteria) they produce proteins called antibodies which bind to and kill the new invading cells. The antibodies produced are specific to the pathogen. 

-Antibodies are produced rapidly and flow around body to kill all similar bacteria/viruses. 

Memory lymphocites give immunity to later infection.

Pathogen enters blood for first time=response slow (aren't many B-lymphocytes to make the antibody needed to bind to antigen). infected person will show symptoms of disease. 

After being exposed to antigen, special type of B-lymphocyte is produced called a memory lymphocyte. these remain in the body for a long time, and 'remember' a specific antibody.

Person is now immune- immune system will respond quickly to second infection. Same pathogen enters body- immune system produces quicker, stronger immune response. will then often get rid of pathogen before symptoms show. 

Immunisation

Immunisation stops you getting infections

it involves injecting dead or inactive microorganisms into the body. these are antigenic (carry antigens), so even tho they're harmless your body makes antibodies to attack them.

the antigens trigger memory lymphocytes to be made. if live micro-organisms of the same type appear after that appear after, they'll be killed immediately by the antibodies which the body has developed against them. 

Jenner- used cowpox to safely immunise against smallpox

smallpox killed lots of people(1700s), left scars on people that survived. he knew that people who had cowpox didn't catch smallpox. 

1)1796-took scab from girl with cowpox. 2)put them into cut on a boy 3)boy bit unwell,but recovered. 4) Jenner exposed boy to smallpox. 5)boy didn't catch smallpox.

cowpox antigens triggered boys B-lymphocytes to produce antibodies. because smallpox has some of same antigens as cowpox,so when boy was infected with smallp,immune system produced antibodies to stop from getting diease

Positives of immunisation-

• big outbreaks of diseases (epidemics) can be prevented if a large percentage of population are immunised. people who aren't immunised are unlikely to catch the disease as fewer people are able to pass it on. if a lot of people aren't immunised, the disease can spread quickly. 
• some diseases (e.g smallpox) have been virtually wiped out by immunisation programmes. 

Negatives of immunisation-

• don't always work-sometimes doesn't give immunity.
• can sometimes cause a bad reaction. (e.g swelling,or something more serious like fever/seizures). bad reactions are rare.

  antibodies are produced by B-lymphocytes. useful antibodies-want to make identical copies of it.however B-lymphocytes don't divide easily. tumour cells however don't produce antibodies but divide a lot-so can be grown easily.you fuse a B-lymphocyte with a tumour cell to create a cell called a hybridoma. hybridoma cells divide quickly---->lots of identical antibodies(monoclonal antibodies) 

can make monoclonal antibodies that bind to anything you want. useful as they will only bind to this molecule. 

pregnancy tests

a hormone is found in the urine of women only when they are pregnant. pregnancy tests detect the hormone.

• bit of stick woman urinates on has some antibodies to the hormone, with blue beads attatched. 
• the test ***** (bit that turns blue if pregnant) has more antibodies to the hormone stuck onto it (so can't move)
• if you're pregnant and urinate on stick:
• hormone binds to antibodies on blue beads
• urine moves up the stick, carrying hormone and the beads
• beads and hormone bind to antibodies on *****
• so blue beads get stuck on the *****, turning it blue.
• if not pregnant and wee on stick, the urine still moves up the stick carrying the blue beads, but nothing to stick the blue beads onto the test *****, so doesn't go blue. 

can make monoclonal antibodies that stick to cancer cells

different cells in the body have different antigens on their cell surface. so can make monoclonal antibodies that will bind to specific cells in the body. cancer cells have antigens on their cell membranes that aren't found on normal body cells-tumour markers.

in the lab, you can make monoclonal antibodies that will bind to tumour markers-diagnose&treat cancer.

 used to diagnose cancer

• first,antibodies labelled with with a radioactive element. then the labelled antibodies are given to patient through a drip. they go into the blood+are carried around the body.
• when antibodies come into contact with the cancer cells,they bind to the tumour markers.
• A picture of the patient's body is taken using a camera that detects radioactivity. anywhere there are cancer cells will show up as a bright spot.
• doctors can see where the cancer is, what size and if it is spreading 

targeting drugs to cancer cells

• anti-cancer drug attached to monoclonal antibodies
• antibodies given to patient through a drip
• antibodies target specific cells(cancer cells) because only bind to tumour markers.
• drug kills the cancer cells but doesn't kill normal body cells near tumour.
• other cancer treatments can affect normal body cells as well as killing cancer cells
• so side effects of an antibody-based drug are lower than for other drugs/radiotherapy.

used to find blood clots

• when blood clots, proteins in the blood join together to form solid mesh. 
• monoclonal antibodies have been developed that bind to the proteins
• can attach a radioactive element to these antibodies.
• then, if you inject them into the body+take a picture using a camera that picks up the radiation, the picture will have a bright spot where there is a blood clot.
• useful as you can find a potentially harmful blood clot (and so get rid of it)