Biology 1A Revision

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Diet and Metabolic Rate

To be healthy, your diet must provide the energy you need by having the right balance of different food groups that do different things. You need:

  • Carbohydrates: To release energy
  • Fats: To keep warm and release energy
  • Protein: For growth, cell repair/replacement
  • Fibre: For a healthy digestive system
  • Vitamins and Minerals: Tiny amounts to keep skin, bones, blood, and everything healthy

Energy is needed to fuel chemical reactions that keep the body alive. Reactions are called metabolism. Speed of this is metabolic rate. Different people have different resting metabolic rates.                                                                                                                                      Muscle=needs more energy than fatty tissue. Higher metabolic rate. Physically bigger people have a higher metabolic rate than normally small people. Bigger=more energy needed due to more cells. Men have slightly higher rate than women as bigger and more muscle. Regular exercise boosts resting metabolic rate up. When you exercise it goes up. Stays high for a while. Active jobs need for exercise. Activity level affects amount of energy diet needs.

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Factors Affecting Health

Health can be affected by an unbalanced diet. Malnourished is when a person's diet is badly out of balance. They can be fat or thin!                                                                                     

Excess carbohydrates or fat can lead to obesity. It's a common disorder. It can be caused by hormonal problems but the main causes are bad diet, overeating and lack of exercise. You could get arthritis, type 2 diabetes, high blood pressure and heart disease.                                     

Lack of food can cause serious malnutrition. The effects depend on what is missing from the diet. The common problems are slow growth, fatigue, poor resistance to infection and irregular periods in women. Deficiency diseases caused by lack of vitamins and minerals. Lack of vitamin c=scurvy.                                                                                                                                    

People who exercise more are healthier. Exercise increases amount of energy used and decreases amount stored as fat. Fit people may not be healthy due to diet.                                  

Health can depend on inherited factors. The factors can affect their metabolic rate or blood chlorestrerol level.

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Evaluating Food, Lifestyle and Diet

I need to be able to evaluate information about how food effects health. Also how lifestyle affects health (what you eat and do)

When analysing slimming products, we need to consider:

  • Is the report a scientific study, published in a respectable journal?
  • Was it written by a qualified person?
  • Was the sample of people asked/tested large enough to get reliable results?
  • Have there been other studies that found similar results?

Effectiveness in one person (e.g celebrity) doesn;t mean a lot- everyone's bodies are different. Some claims are true but very misleading.

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Fighting Disease

Microorganisms that enter the body and cause disease are called pathogens. The two main types of pathogen: Bacteria and viruses.

Bacteria are very small living cells which reproduce rapidly inside your cells. They make you feel ill by damaging your cells and producing toxins (poisons).

Viruses are not cells but are very tiny. They replicate themselves by invading your cells and using their machinery to produce many copies of themselves. This cell damage is what makes you feel ill.

Skin, hairs and mucus in the respiratory tract stop bugs getting in. Small fragments of cells called platelets help blood clot quickly to seal cut wounds. This stops bugs getting in. The immune system has white blood cells which constantly look for microbes. They either:

  • Consume them: By engulfing the foreign cells and digest them
  • Produce antibodies: They produce proteins called antibodies to lock and kill the cells which have foreign antigens on. Particular antibodies match to only that specific disease each.
  • Produce antitoxins: They counteract toxins produced by the invading bacteria.
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Fighting Disease: Vaccination

This is how we fight disease. It can prevent them from occuring. When you're infected with a new microorganism, it takes white blood cells a few days to solve it. Vaccinations put small amounts of dead or inactive microorganisms. They carry antigens, which cause antibodies to produced to attack them. MMR= Measles, mumps, rubella

If live micororganisms of the same type appear, white blood cells can rapidly mass produce antibodies to kill off the pathogen. Some vaccinations wear off over time so boosters are given.

Pros

  • They have helped control lots of infectious diseases that were once common. Smallpox no longer occurs, polio has fallen by 99%.
  • Big outbreaks of diseases called epidemics can be prevented if a large precentage of the population is vaccinated, so even if some are not are unlikely to catch it as they cannot pass it on to a lot of people. If a lot aren't, the disease can spread quickly

Cons

  • They do not always work- sometimes they do not give immunity
  • You can sometimes have a bad reaction to a vaccine. This is very rare
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Fighting Disease: Drugs

Painkillers are drugs that relive pain. but they don't cure it, just reduce symptoms. Many drugs do the same-reduce symptoms without tackling the cause.

Antibiotics work differently. They kill or prevent the growth of the bacteria causing the problem without harming your own body cells. Different antibiotics kill different types of bacteria. However, they don't destroy viruses (e.g cold/flu). They reproduce using your own body cells, which makes it difficult to develop drugs that just destroy the virus and not body cells. Bacteria can mutate, sometimes this causes them to be resistant to (not killed by) antibiotics. If you have an infection it can be the sae, so when you treat it, only non-resistant strains of bacteria will be killed. The resistant strains will still then reproduce (natural selection). The resistant strain can also cause a serious infection that cannot be treated (e.g MRSA). To slow down the rate of infcetion, doctors cannot over prescribe antibiotics.

You can test the action of antibiotics or disinfectants by growing cultures of microbes using agar jelly in a petri dish. This is called a culture medium. The jelly contains carbs, vits &mins and proteins. Wire loops (inoculating loops) are used to trnsfer microbes to the culture medium. The microbes multiply. Everything must be sterilised before being used. It must also have a lid taped to it to stop microbes in the air entering it. School it is kept 25c to prevent harmful pathogens from growing but in proper labs it is kept much higher.

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Fighting Disease: Past and Future

Ignaz Semmelweis saw that women were dying in huge number after childbirth from puerperal fever. he thought doctors were spreading disease on their unwashed hands. By telling doctors entering his ward to wash their hands in an antiseptic solution, he cut death rate 12%-2%. The solution killed the bacteria. Ignaz couldn't prove it so methods dropped when he left the hosital and death rates rose again.

In the last few decades we have dealt with bacterial infections using antibiotics. The death rate from these has fallen rapidly (e.g pnuemonia) as bacteria evolves antibiotic resistance. Overuse of antibiotics has made this worse. People may pass on bacterial infections to others and aren't easy to get rid of. Drug companies are having to create new antibiotics as bacteria resistance is becoming more common.

Bacteria: Can mutate to produce new strains, a new strain could be antibiotic resistant, so it would no longer be clear, a new strain could be one that no-one has encountered before and it ould spread rapidly and cause an epidemic (outbreak of disease).

Viruses: Tend to mutate often so hard to develop vaccines as they could have different antigens, a virus could evolve and become deadly and very infectious, precautions could be taken to stop the virus from spreading,but a flu pandemic could kill millions.

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The Nervous System

A stimulus is a change in your environment which you may need to react to.

Everyone hs five sense organs- eyes, ears, nose, tongue and skin. They all contain different receptors (groups of cells which are sensitive to stimulus).

  • Eyes- Light receptors, sensitive to light
  • Ears- Sound receptors, also balance receptors, sensitive to changes in position
  • Nose- Smell receptors, sensitive to chemical stimuli
  • Tongue- Taste receptors, chemical stimuli
  • Skin- Sensitive to touch, pressure, pain and temperature change
  • Sensory neurones- Nerve cells that carry signals as electrical impulses from receptors in the sense organs to the central nervous system
  • Relay neurones- Nerve cells that carry signals from sensory neurons to motor neurones
  • Motor neurones- Nerve cells that carry signals from the central nervous system to the effector muscles or glands
  • Effectors- Muscles or glands are known as these. They respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones
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The Nervous System- Part 2

The central nervous system is where all the info from the sense organs and where reflexes and actions are coordinated. It consists of the brain and spinal cord only. Neurones (nerve cells) transmit the inforamation (as electrical impulses) very quickly to and from it. 'Instructions' are sent to the effectors which respond accordingly.

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Synapses and Reflexes

Neurones transmit information very quickly to and from the brain, and your brain quickly decides how to respond to the stimulus.

The connecetion between two neurones is called a synapse. The nerve signal is transferred by chemicals which diffuse (move) across the gap. These chemicals then set off a new electrical signal in the next neurone. Reflexes are the automatic reponses to certain stimuli-they can reduce the chances of being injured. For example, if the light gets brighter, your pupils get smaller to prevent damage. The passge of information in a relfex (from receptor to effector) is called a reflex arc. The neurones in these go through the spinal cord or though an unconscious part of the brain. When a stimulus is detected by the receptors, impulses are sent long a sensory neurone to the central nervous system. When the impulses reach the synapse between the sensory and relay neurone, they trigger chemicals to be released to be sent along the relay neurone. When the impulses reach a synapse between the relay and motor neurone, the same thing happens, except the impulses are now sent along the motor neurone. The impulses then travel along the motor neurone to the effector (e.g muscle). The effector (in this case a muscle) then contracts and moves your hand away from the stimuli for example. As you don't have to think about it, it is quicker than normal responses.

Stimulus - receptor - sensory neurone - relay neurone- motor neurone - effector - response

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Hormones

Hormones can also send information around the body. 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) i particular places. They control things in organs and cells that need constant adjustment.  They are produced in (and secreted by) various glands (see below). They travel through your body at the 'speed of blood' and tend to have long lasting effects.

'Hormones are chemical messengers which travel in the blood to activate target cells'.

The 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

Hormones and nerves do similar jobs but there are differences. Nerves have very fast action, act for a very short time and work on a very precise area, whereas hormones have a slower action, act for a long times and act in a more general way. If a reponse is really quick it is probably nervous and some information needs to be passed to effectors really quickly. But if a reposnse lasts for a long time, it is probably hormonal e.g adrenaline causing a fight or flight response and even though it is quick, you feel a bit wobbly for a while afterwards.

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The Menstrual Cycle

Is the monthly release of an egg from a women's ovaries, and the build up and breakdown of the protective lining in the uterus (womb).

  • Stage 1: Day 1 is when the bleeding starts. The uterus ling breaks down for about 4 days.
  • Stage 2: The lining of the uterus builds up again, from day 4 to day 14, into a thick spongey layer full of blood vessels, ready to recieve a fertilised egg.
  • Stage 3: An egg is relased from the ovary at day 14.
  • Stage 4: The wall is amintained for about 14 days, until day 28. If no fertilised egg has landed on the uterus wall by then the spongey lining starts to break down again and whole cycle restarts.

Hormones control the different stages, and there are three main ones involved:

  • FSH (Follicle Stimulating Hormone) Produced by the pituitary gland and causes egg to mature in one of the ovaries. it stimulates the ovaries to produce oestrogen.
  • Oestrogen: Produced in ovaries, causes pituitary to produce LH. Inhabits the further release of FSH.
  • LH (Luteinising Hormone) Produced pituitary gland, stimulates the release of an egg at around the middle of the cycle.
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Controlling Fertility

The hormones FSH, Oestrogen and LH can be used to control a women's fertility. Oestrogen can be used to prevent the release of an egg, so it can be used as a method of contraception. If it is taken every day to keep the level permanantly high, it inhibits the production of FSH, so after a while egg development and production stop completely and stay stopped. Progesterone also reduces fertility by stimulating the production of thick cervical mucus which prevents any sperm getting through and reaching an egg. There is also a pill for this though not very effective.

The pill is an oral contraceptive made in 1950s and contained levels of oestrogen and progestrone. There were concerns about side effcts such as blood clots, so now the pill has lower levels of oestrogen to prevent this. The pill is over 99% effective at preventing pregnancy. It reduces the risk of getting some types of cancer too. However, it isn't 100% effective so there is still a slight chance of getting pregnant. it can cause side effects such as headaches, nausea, irregular menstrual bleeding and fluid retention and it doesn't prevent STD's.

Some women have low levels of FSH that are too low to cause their eggs to mature, so they are not released and women cannot get pregnant. Levels of FSH and LH can be injected to stimulate egg release. It helps a lot of women pregnant, but it doesn't always work so it can be expensive doing it again and again. Multiple pregancies can also happen by multiple egg being stimulated.

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Controlling Fertility- Part 2

IVF involves collecting eggs from a women's ovaries and fertilising them in a lab using the man's sper. They are then grown into embryos. Once the embryos are tiny balls of cells, one or two of them are transferred to the women's uterus to improve the chance of pregnancy. FSH and LH are given before egg collection to stimulate egg production. It can give an infertile couple a child, but some women have a strong reaction to the hormones (e.g abdominal pain, vomiting, dehydration). There have been reports of increased cancer due to the hormonal treatment . Multiple births can happen too if more than one embryo grows into a baby- this is risky for mother and babies as there is a higher risk of miscarriage and stillbirths.

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Plant Hormones

Hormones make sure that plants grow towards light.
Auxin is a plant growth hormone that controls growth near the tips of shoots and roots.
It controls the growth of the plant in repsonse to light (phototropism), gravity (gravitropism or geotropism) and moisture.
It is produced in the tips and moves backwards to stimulate the cell elongation (enlargement process). This happens in the cells just behind the tips.
If the tip of the shoot is removed, no auxin is available and the shoot may stop growing. Extra auxin promotes growth in the shot but inhibits the growth in the root.

Plant hormones have been extracted and used by people, or artificial versions can been made. This means that selective products such as weed killer are made of plant growth hormones that only affect broad leaved plants. They disrupt their normal growth patterns, which kils them but leaves the rest of crop field untouched.
Plant cuttings won't always grow in soil, so if rooting powder is added (containing auxin) they will produce roots rapidly and start growing as new plants, therefore a good plant can be reproduced.

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Plant Hormones: Part 2

Shoots grow towards light, so when a shoot tip is exposed to it, more auxin accumulates on the side that's in the shade than the side that's in the light. The cells grow faster on the shaded side so the shoot bends towards the light.
Shoots grow away from gravity, when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side, which causes the lower side to grow faster, bending the shoot upwards.
Roots grow towards gravity, a root growing sideways will also have more auxin on it's lower side,but in a root the extra auxin inhibits growth, so the cells on top elongate faster and the root bends down
Roots grow towards the moisture, an uneven amount of moisture either side of the root produces more auxin on the side with more moisture, this inhibits growth on that side causing the root to bend in that direction, towards the moisture.

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Homeostatis

This means all the functions of your body which try to maintain a constant internal environment'.
To keep cells working properly, certain things need to be kept at the right level. Bodily levels controlled include ion, water and sugar content and temperature.
Ion content regulated by the kidneys. They are taken into the body from food, then absorbed into the blood. If a food has too much of it then the excess ions need to be removed. Some ions are lost in sweat.  The kidneys remove the excess from the blood, then it is gotten rid of by urine. Water has to be constantly balanced in the body. It is taken into the body via food and drink and is lost in a few different ways: through the skin as sweat, via the lungs in breath, via the kidneys as urine. The balance between sweat and urine depends on the weather or what you are doing.        All enzymes work best at a certain temperature 37c, so your body tries to maintain this temperature. A part of the brain acts as your own thermostat. It is senssitive to blood temperature in the brain, and it recieves messages from the skin that provide information about skin temperature. Blood sugar level is maintained by eating foods containing carbohydrates to put glucose into the blood from the gut. The normal metabolism from cells rmoves this glucose from the blood, but the more exercise you do, the more is removed. A hormone called insulin helps maintain the right level of glucose in your blood so your cells get a constant supply of energy.

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Drugs

Drugs alter what goes on in your body and the reactions that take part. Some chemical changes caused by drugs can lead to the body becoming addicted to drugs. If the drug isn't taken, the addict can suffer withdrawal symptoms.
Medicinal drugs are medically useful, like antibiotics. For some you don't need a prescription, but for others you do as they can be dangerous if misused. Recreational drugs are for fun, and can be legal or illegal. Performance enhancing drugs can improve a person's performance in sport. Some atheletes take performance enhancing drugs to make them better at sport. There are different types such as anabolic steriods (increase muscle size) and stimulants ( that increase heart rate). The drugs can have bad effects, eg steriods can cause high blood pressure. Some are also banned by law, some are prescription only but all are banned by sporting bodies. It's unfair if people gain advantage by taking drugs not just through training. Athletes miay not know of the serious health risks that are involved. Atheletes have the right to make their own decision about whether taking drugs is worth the risk or not. Drug free sport isn't fair either, as different athletes have access to different training equipment.
Statins are prescribed used to lower he risk of heart and circulatory disease. Evidence was backed up. Cannabis is an illegal drug. Scientists have investigated whether the chemicals in cannabis smoke cause mental health problems. The results vary, but this proves that claims about drugs need to be carefully looked at.

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Testing Medicinal Drugs

New drugs are always being developed, but they have to be put through a testing procedure.

Drugs are tested on human cells and tissues in a lab- the cells must be appropriate to the test such as whole or multiple body systems.

They then test the drug on live animals to see if the drug works, find out its toxicity (how harmful it is), and the best dosage. The law in Britain states any new drug must be tested on two different live animals. Some think it is cruel to do this, but others believe it is the best option to see if it is ok. If the drug passes the animal test, then it is tested on human volunteers in a clinical trial. It is tested on healthy humans first to make sure it doesn't have any side effects. A low dose is given and gradually increased. If these results are good, then the drug is tested on the people suffering the illness. The optimum dose is found (the dose that is most effective has the least side effects). The patients are put into two groups, one is given the new drug, another given the placebo (a substance that's like the new drug being tested). This is so the doctor can see the actual difference the drug makes. The trials are blind, no-one knows whether they have the placebo or the actual drug, often the patient or the doctor don't know which one it is until the results have been gathered. This is so that the results are persuaded. This can go wrong such as Thalidomide in the 1950s, intended to be a sleeping pill but eventually became a morning sickness pill that caused abnormal development in babies

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Recreational Drugs

These drugs are used just for fun. Illegal drugs are often put into two classes- soft and hard, usually thought of as being seriously addictive and generally more harmful. All of these drugs can cause heart and circulatory problems though.

People know about the side effects, but continue to use them because of the enjoyment, relaxation and stress relief. Some also say for inspiration. Some factors in a person's life or background may aso influence them to take them.

Almost all of the 'hard' drug users say they tried Cannabis (soft drug) first. Some say it is a stepping stone- the effects of it mke people want to use harder drugs, others say it is a gateway drug that brings people into contact with drug dealers. Some just want to try other drugs anyway. Some legal drugs make more of an impact than illegal drugs, such as tobacco and alcohol are both legal and recreational but can change society. Smoking causes diseases of the heart, blood vessels and lungs. It can also cause cancer and the nicotine in it is addictive. Alcohol affects the nervous system and slows down body reactions and leads to impaired judgement, poor coordination and unconsciousness. I can lead to brain damage and is also addictive. The National Health Service spends a lot of time treating people with lung disease caused by smoking. The same goes for alcohol. In addition to finacial costs, they both cause a lot of sorrow and anguish for people around them too.

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