Biology 1 AQA

• Your diet must provide the energy you need but not more.
• The different food groups have different uses in the body so you need to have the right balance of foods.
• Carbohydrates release energy.
• Fats keep you warm and release energy.
• Protein is needed for growth, cell repair and cell replacement.
• Fibre keeps everything moving through your digestive system.
• Tiny amounts of various vitamins and mineral ions keep your skin, bones, blood and everything else generally healthy.

• Energy fuels the chemical reactions in the body that keep you alive. These reactions are called your metabolism, and the speed at which they occur is your metabolic rate.
• There are slight variations in the resting metabolic rate of different people. For example, muscle needs more energy than fatty tissue, which means people with a higher proportion of muscle to fat in their bodies will have a high metabolic rat.
• Physically bigger people are likely to have a high mentabollic rate than smaller people. The bigger you are the more energy your body needs to be supplied with (because you have more cells).
• Men tend to have a slightly higher rate than women; they are slightly bigger and have a larger proportion of muscle.
• Other genetic factors may also have some effect.
• Regular exercise can boost your resting metabolic rate because it builds muscle.

• When you exercise you need more energy, so your metabolic rate goes up during exercise and it stays high for some time after you finish.
• People who have more active jobs need more energy on a daily basis, for example builders need for energy per day than office workers.
• Your activity level affects the amount of energy your diet should contain. If you do little exercise you are going to need less energy, so less fat and carbohydrate in your diet.

• People whose diet is badly out of balance are said to be malnourished. Malnourished people can be fat, thin or unhealthy in other ways.
• Excess carbohydrate or fat in the diet can lead to obesity. (Being 20% or more over maximum recomended body mass.)
• Hormonal problems can lead to obesity, though the usual cause is a bad diet , overeating and a lack of exercise.
• Health problems that can arise as a result of obesity include: arthritis (inflammation of the joints), type 2 diabetes (inability to control blood sugar level), high blood pressure and heart disease. It's also a risk factor for some kinds of cancer.
  Too much saturated fat in your diet can increase your blood cholesterol. Eating too much salt can cause high blood pressure and heart problems.
• Some people suffer from lack of food, particularly in developing countries.
  The effects of malnutrition vary depending on what foods are missing from the diet. Problems commonly include slow growth (in children), fatigue, poor resistance to infection and irregular periods in women.
• Definciency diseases are caused by a lack of vitamins or minerals. For example a lack of vitamin C can cause scurvy, a deficiency disease that causes problems with the skin, joints and gums.

• People who exercise regularly are usually healthier than those who don't.
• Exercise increases the amount of energy used by the body and decreases the amount stored as fat. It also builds muscle so it helps to boost your metabolic rate.
• Sometimes pwople can be fit but not healthy. For example you can be physically fit and slim but malnourished at the same time because your diet isn't balanced.

• Microorganisms that enter the body and cause disease are called pathogens. Pathogens cause infectious diseases (can easily spread).
• There are two main types of pathogen: Bacteria and Viruses.

• Bacteria are very small living cells (about 1/100th the size of your body cells), which can reproduce rapidly inside your body.
• They make you feel ill by doing two things. They damage your cells and they produce toxins (poisons).

• Viruses are not cells; they're much smaller. They're about 1/100th the size of a bacterium.
• They replicate themselves by invading your cells and using the cells' machinery to produce many copies of themselves. The cell will usually then burst, releasing all the new viruses.
• The cell damage is what makes you feel ill.

• Your skin, plus hair and mucus in your respiratory tract, stop a lot of nasties getting inside your body.
• To try and prevent microorganisms getting into the body through cuts, small fragments of cells (called platelets) help blood clot quickly to seal wounds. If the blood contains low numbers of platelets it will clot more slowly.
• If something does make it through, your immune system will kick in. The most important part is the white blood cells. They travel around your body, looking for microbes. When they come across an invading microbe they have three lines of attack.

1) White blood cells can engulf foreign cells and digest them.

2) Every invading cell has unique molecules (called antigens) on its surface. When your white blood cells come across a foreign antigen, they will start to produce proteins called antibodies to lock onto and kill the invading cells. The antibodies produced are specific to that type of antigen. Antibodies are then produced rapidly and carried around the body to kill all similar bacteria or viruses. If the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it -the person is naturally immune to that pathogen and won't get ill again.

3) The white blood cells can produce antitoxins to counteract toxins produced by the invading bacteria.

• It takes a few days for your white blood cells to learn how to deal with an infection caused by a new microorganism.
• Vaccinations involve injecting small amount of dead or inactive microorganisms. These carry antigens, which cause your body to produce antibodies to attack them - even though the microorganism is harmless.
• If live microorganisms of the same type appear after that, the White blood cells can rapidly mass-produce antibodies to kill off the pathogen.
• Some vaccines wear off over time. booster injections may need to be given to increase levels of antibodies again.

PROs
1) Vaccines have helped control lots of infectious diseases that were once common in the UK (e.g. Polio, Measles, Whooping Cough, Rubella, Mumps, Tetnus...). Small Pox no longer occurs at all and Polio infections have fallen by 99%.

2) Big outbreaks of disease - called epidemics - can be prevented if a large percentage of the population is vaccinated.

CONs
1) Vaccines don't always work - sometimes they don't give you immunity.

2) You can sometimes have a bad reaction to a vaccine, but this is rare.

• Painkillers (e.g. aspirin) are drugs that relive pain. They don't tackle the cause of the disease, they just help to reduce symptoms.
• "Cold remedies" do a similar thing. They don't actually cure colds.
• Antibiotics (e.g. penicillin) work differently - they actually kill (or prevent growth of) the bacterial causing the problem without killing your own body cells. Different antibiotics kill different types of bacteria, so it's important to be treated with the right one.
• Antibiotics don't destroy viruses (e.g. flu or cold viruses). Viruses reproduce using your own body cells, which makes it very difficult to develop drugs that destroy just the virus without killing the body cells.

• Bacteria can mutate - sometimes the mutations cause them to be resistant to an antibiotic.
• If you have an infection, some of the bacteria might be resistant to antibiotics.
• When you treat the infection, only the non-rsistant strains of bacteria will be killed.
• The individual resistant bacteria will survive and reproduce, and the population of the resistant strain will increase. This is an example of natural selection.
• This resistant strain could cause a serious infection that can't be treated by antibiotics.
• To slow down the rate of development of resistant strains, it's important for doctors to avoid over-prescribing antibiotics.

• You can test the action of antibiotics or disinfectants b growing cultures of microorganisms.
  1) Microorganisms are grown in a "culture medium". This is usually agar jelly containing the carbohydrates, minerals, proteins and vitamins they need to grow.
  2) Hot agar jelly is poured into Petri Dishes.
  3) When the jelly is cooled and set, inoculating loops (wire loops) are used to transfer microorganisms to the culture medium. The microorganisms then multiply.
  4) Paper discs are soaked in different types of antibiotics and placed on the jelly. Antibiotic-resistant bacteria will continue to grow around them but non resistant strains will die.
• The Petri dishes, culture medium and inoculating loops must be sterilised before use, e.g. the inoculating loops are passed through a flame. If equipment isn't sterilised, unwanted microorganisms in the culture medium will grown and affect the results. The Petri dish must have a lid that is taped on to stop any microorganisms in the air contaminating the culture. In the lab at school, cultures of microorganisms are kept at about 25 degrees because harmful pathogens aren't likely to grow at this temperature. In industrial conditions, cultures are incubated at higher temperatures so that they can grow a lot faster.

• While Ignaz Semmelweis was working in Vienna General Hospital in the 1840s, he saw that women were dying in huge numbers after childbirth from a disease called puerperal fever.
• He believed that doctors were spreading the disease on their unwashed hands. By telling doctors entering his ward to wash their hands in an antiseptic solution, he cut the death rate from 12% to 2%.
• The antiseptic solution killed bacteria on doctors hands but this wasn't discovered for another 20 years. So when Semmelweis couldn't prove why his idea worked, his methods were dropped when he left the hospital and death rates increased again.
• Nowadays we know that basic hygiene is essential in controlling disease.

• Bacteria evolve antibiotic resistance and overuse of antibiotics has made the issuer of resistance worse. The likelihood of people being infected by antibiotic-resistant strains is increasing.
• People who become infected with these bacteria can't easily get rid of them and may pass them on to others.
• antibiotic resistance is a big problem and its encouraged drug companies to work on developing new antibiotics that are effective against these resistant strains.
• Bacteria that are resistant to most known antibiotics ('superbugs') are becoming more common.

BACTERIA
1) Bacteria can mutate to produce new strains.
2) A new strain could be antibiotic-resistant, so current treatments would no longer clear an infection.
3) A new strain could be one that we've not encountered before, so no-one would be immune to it.
4) This means a new strain of bacteria could spread rapidly in a population of people and could even cause an epidemic.

VIRUSES
1) Viruses also tend to mutate often. This makes it hard to develop vaccines against them because the changes to their DNA can lead to them having different antigens.
2) They'd be real problems if a virus evolved so that it was both deadly and very infectious.
3) If this happened precautions could be taken to stop the virus spreading in the first place. Vaccines and antiviral drugs could be developed (though these take time to mass produce).
4) Worst case scenario: a flu pandemic could kill billions of people all over the world.

• A stimulus is a change in your environment that you may react to.
• You have five different sense organs - eyes, ears, nose, tongue and skin.
• They all contain different receptors. Receptors are groups of cells which are sensitive to a stimulus. They change stimulus energy (e.g. light energy) into electrical impulses.
• A stimulus can be light, sound, touch, pressure, pain, chemical or a change in position or temperature.

Sense organs and Receptors:
The eye is a sense organ - it contains light receptors.
The ear is a sense organ - it contains sound receptors.

EYES: Light receptors - sensitive to light. These cells have a nucleus, cytoplasm and cell membrane (just like most animal cells).

EARS: Sound receptors - sensitive to sound. Also, "balance" receptors - sensitive to changes in position.

NOSE: Smell receptors - sensitive to chemical stimuli.

TONGUE: Taste receptors - sensitive to bitter, salt, sweet and sour, plus the taste of savoury things like monos odium glutamate (MSG) - chemical stimuli.

SKIN: Sensitive to touch, pressure, pain and temperature changes.

• The central nervous system is where all the information from the sense organs is sent, and where reflexes and actions are coordinated. The central nervous system consists of the brain and spinal chord only.
• Neurones (nerve cells) transmit the information (as electrical impulses) ver quickly to and from the CNS.
• "Instructions" from the CNS are sent to the effectors (muscles and glands), which respond accordingly.

Sensory Neurones:
The nerve cells that carry signals and electrical impulses from the receptors in the sense organs to the central nervous system.

Relay Neurones:
The nerve cells that carry signals from sensory neurones to motor neurones.

Motor Neurones:
The nerve cells that carry signals from the central nervous system to the effector muscles or glands.

Effectors:
Muscles and glands are known as effectors - they respon in different ways. Muscles contract in response to a nerve impulse, whereas glands secrete hormones.

Neurones transmit information very quickly to and from the brain, and your brain decided how to respond to a stimulus. But reflexes are even quicker...

Synapses connect neurones.
1) The connection between two neurones is called a synapse.
2) The nerve signal is transferred by chemicals which diffuse across the gap.
3) These chemicals then set off a new electrical signal in the next neurone.

Reflexes help prevent injury.
1) Reflexes are automatic response to certain stimuli- they can reduce the chances of being injured.
2) For example, if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye - this stops it getting damaged.
3) Or if you get a shock, your body releases a hormone adrenaline automatically - it doesn't wait for you to decide if you are shocked.
4) The passage of information in a reflex (from receptor to effector) is called a reflex arc.

1) The neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain.
2) when a stimulus (e.g. a painful bee sting) is detected by receptors, impulses are sent along a sensory neurones to the CNS.
3) When the impulses reach a synapse between the sensory neurones and a relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone.
4) When the impulses reach a synapse between the relay neurone and a motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone.
5) The impulses then travel along the motor neurone to the effector.
6) Because you don't have time to think about the response it's quicker than normal responses.

• The other way to send information around the body (apart from along the nerve) is by using hormones.
• Hormones are chemicals released directly into the blood. They are carried in the blood plasma to other parts of the body, but only affect particular cells (called target cells) in particular places. Hormones control things in organs and cells that need constant adjustment.
  Hormones are produced in (and secreted by) various glands. They travel through your body at "the speed of blood".
• Hormones tend to have relatively long-lasting effects.

LEARN:
Hormones are chemical messages which travel in the blood to activate target cells.

Pituitary Gland:
This produces many important hormones including FSH and LH, which are involved in the menstrual cycle.
Ovaries: (females only)
Produce oestrogen, which is involved in the menstrual cycle.

They do similar jobs but there are differences.

NERVES:
1) Very fast action
2) Act for a short time
3) Act on a very precise area

HORMONES:
1) Slower action
2) Act for a long time
3) Act in a more general way

If the response is really quick, it's probably nervous. (Pain etc.)
If a response lasts for a long time, it's probably hormonal. (Adrenaline)

Stage 1:
Day 1 is when the bleeding starts. The uterus lining breaks down for about four days.

Stage 2:
The lining of the uterus builds up again, from day 4 to 14, into a thick spongy layer of blood vessels, ready to receive a fertilised egg.

Stage 3:
An egg is released from the ovary at day 14.

Stage 4:
The wall is then maintained for about 14 days, until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts again.

There are three main hormones involved:

1) FSH (follicle-stimulating hormone)

• Produced by the pituitary gland.
• Causes an egg to mature in one of the ovaries.
• Stimulates the ovaries to produce oestrogen.

2) Oestrogen

• Produced in the ovaries.
• Causes pituitary to produce LH.
• Inhibits the further release of FSH.

3) LH (luteinising hormone)

• Produced by the pituitary gland.
• Stimulates the release of an egg at around the middle of the menstrual cycle.

Progesterone is another hormone involved in the menstrual cycle - it's produced by the ovaries.

• Oestrogen can be used to prevent the release of an egg - so it can be used as a method of contraception. This is strange since naturally oestrogen helps stimulate the release of eggs, but if oestrogen is taken every day to keep the level of it permanently hig, it inhibits the production of FSH, and after a while egg development and production stop and stay stopped.
• Progesterone also reduces fertility e.g. by stimulating the production of thick cervical mucus which prevents any sperm getting through and reaching an egg.
• The pill is an oral contraceptive. The first version was made in the 1950s and contained high levels of oestrogen and progesterone (known as the combined oral contraceptive pill). There were concerns about a link between oestrogen in the pill and side effects like blood clots. The pill now contains lower doses of oestrogen so has fewer side effects.
• There's also a progesterone-only pill - it has fewer side effects than the pill (but it's not as effective).

PROs:

1) The pill is over 99% effective at preventing pregnancy.
2) It reduces the risk of getting some types of cancer.

CONs:

1) It isn't 100% effective - there still a very slight chance of getting pregnant.
2) It can cause side effects like headaches, nausea, irregular menstural bleeding and fluid retention.
3) It doesn't protect against STDs.

• Some women have levels of FSH that are too low to cause their eggs to mature. This means that no eggs are released and the women can't get pregnant.
• The hormones FSH and LH can be injected by these women to stimulate egg release in their ovaries.

PROs:

1) It helps a lot of women get pregnant when previously they couldn't.

CONs:

1) It doesn't always work - some women may have to do it many times, which can be expensive.
2) Too many eggs could be stimulated, resulting in unexpected multiple pregnancies.

1) IVF ("in vitro fertilisation") involves collecting eggs from the women's ovaries and fertilising them in a lab using the man's sperm. These are grown into embryos.
2) Once the embryos are tiny balls of cells, one or two of them are transferred to the woman's uterus to improve the chance of pregnancy.
3) FSH and LH are given before egg collection to stimulate egg production (so more than one egg can be collected).

PRO:

• Fertility treatment can give an infertile couple a child.

CONs:

• Some women have a strong reaction to the hormones - e.g. abdominal pain, vommitting, dehydration.
• There have been reports of increased risk of cancer due to hormone treatment.
• Multiple births can happen if more than one embryo grows into a baby.

1) Auxin is a plant hormone that controls growth near the tips of shoots and roots.

2) It controls the growth of a plant in response to light (phototropism), Gravity (gravitropism or geotropism) and moisture.

3) Auxin is produced in the tips and moves backwards to stimulate the cell elongation (enlargment) process which occurs in the cells just behind the tips.

4) If the tip of a shoot is removed, no auxin is available and the shoot may stop growing.

5) Extra auxin promotes the growth in the shoot but inhibits growth in the root - producing the desired result...

Shoots grow towards light
1) When a shoot tip is exposed to light, more auxin accumulates on the side that's in the shade than the side that's in the light.
2) This makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light.
Shoots grow away from gravity
1) When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side.
2) This causes the lower side to grow faster, bending the shoot upwards.
Roots grow towards gravity
1) A root growing sideways will also have more auxin on its lower side.
2) But in a root the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards.
Roots grow towards moisture
1) An uneven amount of moisture either side of a root produces more auxin on the side with more moisture.
2) This inhibits growth on that side, causing the root to bend in that direction, towards the moisture.

• Plant hormones can be extracted and used by people, or artificial versions can be made.

1) Most weeds in crop fields are broad-leaved, unlike grasses and cereals which have very narrow leaves. Selective weed killers are made of plant growth hormones - they only affect the broad-leaved plants. They disrupt their normal growth patterns, which soon kills them, but leaves the crops untouched.

2) Plant cuttings won't always grow in soil. If you add rooting powder, which contains the plant hormone auxin, they'll produce roots rapidly and start growing as new plants,
This helps to produce lots of clones of a really good plant really quickly.

It means all the functions of your body which try to maintain a "constant internal environment".

To keep all of your cells working properly, certain things must be kept at the right level.
Bodily levels that need to be controlled include:

• Ion content
• Water content
• Sugar content
• Temperature

Ion content is regulated by the kidneys.

1) Ions (e.g. sodium, Na+) are taken into the body in food, then absorbed into the blood.

2) If the food contains too much of any kind of ion then the excess ions need to be removed. E.g. a salty meal with contain far too much Na+.

3) Some ions are lost in sweat (which tastes salty).

4) The kidneys will remove excess from the blood - this is then got rid of in urine.

The body needs to constantly balance the water coming in against the water going out. Water is taken into the body in food and drink and lost from the body in these ways:

• through the skin as sweat
• via the lungs in breath
• via the kidneys as urine.

The balance between sweat and urine can depend on what you are doing, or what the weathers like.

The enzymes within the body work best at 37 degrees centigrade and so this is the temperature your body tries to maintain.

A part of your brain acts as your own personal thermometer. It's sensitive to the blood temperature in the brain, and it receives messages from the skin that provide information about skin temperature.

Eating food that contain carbohydrates puts glucose into the gut.

Normal metabolism of cells removes glucose from the blood.

Vigorous exercise removes much more glucose.

A hormone called insulin helps to maintain the right level of glucose in your blood, so your cells get a constant supply of energy.

• Some of the chemical changes caused by drugs can lead to the body becoming addicted. If the drug isn't taken, the addict can suffer physical withdrawal symptoms.
• Medicinal drugs are medically useful, like antibiotics. For some of these drugs you don't need a prescription (paracetamol) but for other you do (morphine) because they can be dangerous if misused.
• Recreational drugs are used for fun. They can be illegal or legal.
• Performance-enhancing drugs can improve a person's performance in sport.

• Anabolic steroids increase muscle size, Stimulents increase heart rate.
• These drugs can have negative health effects e.g. steroids can cause high blood pressure.
• Some of these drugs are banned by law, others are prescription-only. All are banned by sporting bodies.

Ethical problems with taking these drugs:

AGAINST
1) It's unfair if people gain an advantage by taking drugs, not just through training.
2) Athletes may not be fully informed of the serious health risks of the drugs they take.
FOR
1) Athletes have the right to make their own decision whether taking drugs is worth the risk or not.
2) Drug-free sport isn't really fair anyway - different athletes have access to different training facilities, coaches, equipment etc.

Claims about the effects of drugs need to be looked at critically.

Statins:

• These are prescribed drugs used to lower the risk of heart and circulatory diseases.
• There is evidence that statins lower blood cholesterol and heart disease.
• The original research was done by government scientists with no connection to the manufacturer. The sample was large - 6000 patients.
• It compared two groups of patients - those who had taken statins and those who hadn't. Other studies have since backed up the findings.

Cannabis:

• This is an illegal drug. Scientist have investigated whether the chemicals in cannabis smoke cause mental health problems. The results vary and are open to different interpretations.
• Until definite scientific evidence is found, no one can be sure.

There are three main stages to drug testing:

1) Drugs are tested on human cells and tissues in a lab. You cannot use human cells to test drugs that affect the whole or multiple body systems.

2) Test the drug on live animals. This is to test whether the drug works, to find out about toxicity and the best dosage. The law in Britain states that any new drug must be tested on two different live mammals. Some people think this is cruel, but others believe it's the safest way.

3) If the drug passes the tests on animals, it is tested on human volunteers in a clinical trial. First it is tested on healthy volunteers with a low dosage to check for harmful side effects. If the results are good, the drug is tested on people with the illness. The optimum dose is found - most effective, fewest side effects. To test how well it works, patients are split into two groups. One is given the new drug and the other is given a placebo. This is so the doctors can see the actual difference the drug makes. Clinical trials are blind - neither the doctor nor the patients know who has the placebo until afterwards to prevent subconsciously influencing the results.

Developed in the 1950s.

• Thalidomide was tested as a sleeping pill but later it was found to be effective in relieving morning sickness.
• The drug wasn't tested for morning sickness. It was unknown that the drug could pass through the placenta and affect the fetus, causing abnormal limb development. In some cases some babies were born with no arms or legs.
• About 10000 babies were affected and only about half of them survived.
• The drug was banned and more rigorous testing procedures were introduced.
• More recently thalidomide has been used in the treatment of leprosy and other diseases, e.g. some cancers.

Illegal drugs are divided into the classes soft and hard. Hard drugs are usually thought to be more addictive and generally more harmful. The term is vague, you can have issues with soft drugs. Heroine and ecstasy are examples of hard drugs and cannabis is a soft drug. They can all cause heart and circulatory system problems.

Why people use cannabis:
For real patios, enjoyment or stress relief. To get stoned or for inspiration.
Although personal lives often influence people into choosing to use drugs.

All most all hard drug users have tried cannabis first. The link isn't clear, but three common opinions are: the effects of cannabis create a desire to try harder drugs, cannabis users bring people into contact with drug dealers, certain people are more likely to take drugs and so cannabis users will also try other drugs.

Smoking:

• Causes disease of the heart, blood vessels and lungs.
• Also causes cancer.
• Nicotine is the drug found in cigarettes and is very addictive, so it's hard to stop smoking.

Alcohol:

• Effects the nervous system and slows down body relations.
• Too much alcohol leads to impaired judgement, poor coordination and unconsciousness.
• Can cause liver disease and brain damage.
• Addictive

Tabacco and alcohol have a bigger impact in the UK than illegal drugs, because so many people take them. The financial costs of alcohol and tobacco cause sorrow and anguish to the people affected by them, either directly or indirectly