Biology Unit 1


Diet and Metabolic Rate

Balanced diet:

  • You must provide the energy you need, but no more
  • You need the right ballance of foods
    • enough carbohydrates to release energy
    • fats to keep warm and release energy
    • protein for growth, cell repair and cell replacement 
    • fibre to keep everything running smoothly through the digestive system
    • tiny amounts of minerals and vitimans to keep skin, blood and bones healthy

Energy needs vary - who they are

  • Energy need to fuel reactions, which are called your metabolism - the speed of which this happens is called your metabollic rate
  • People have different resting metabollic rates
  • Mussle needs more energy than fatty tissue, so people with a higher mussle to fat ration have a higher metabollic rate
  • The bigger you are need a higher metabollic rate as you have more cells
  • Men tend to have a higher rate
  • Regular exercise can boost resting rate as it builds mussle
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Diet and Metabolic Rate (2)

Energy needs vary - what they do

  • Need more energy during exercise so metabollic rate goes up
  • Some people have more active jobs so need more energy on a daily basis
  • Activity levels affect the amount of energy your diet should contain
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Factors Affecting Health

Unbalanced diet:

  • People who have a bad diet are malnourished
  • Malnourished people can be fat or fin
  • Obeisty
    • excess carbs or fat can lead to obesity
    • obesity is common in developed countries
    • hormonal problems can lead to obesity
    • health problems can be caused by obesity
      • artihitus
      • type 2 diabetes
      • high blood pressure
      • heart disease
      • risk of cancer
  • Other health prblems
    • too much saturated fat can increase your blood cholestrol
    • too much salt can cause high blood pressure and heart problems
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Factors Affecting Health (2)

  • Eating to little
    • people suffer of lack of food particulary in poor countries
    • malnurition can vary
      • slow growth (in children)
      • fatigue
      • poor resistance to infection
      • irregular periods in women
    • deficiency diseases are caused by lack of vitimans or minerals
      • lack of vitiman c can cause scurvey
      • problems with skin, joints and gums

Not enough exercise:

  • People who exercise regularly are generally healthier
  • exercise increases amount of energy used and decreases the amount of stored fat
  • Builds mussle which increases metabolic rate
  • People who excercise less are more likely to suffer from health problems
  • People can be fit but not healthy
    • you can be physically fit and slim, but malnourished because your diet isn't ballanced
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Factors Affecting Health (3)

Inherited factors:

  • Metabolic rate can be inherited
  • Can affect blood cholestral level
  • Cholestral is essentiall but not too much as it can cause heart disease
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Evaluating Food, Lifestyle and Diet

Slimming claims that arent proven:

  • Lots of products claim they help lose weight
  • Look out for:
    • is the report a scientific study
    • was it written by a qualified person
    • was the sample tested on large enough to be reliable
    • have other studies found similar results
  • The only way to lose weight is to take in less energy than you use, so sliming pills only work if:
    • you eat less fat and carbs
    • you do more exercise
  • Some claims may be true but misleading
    • low fat bars might be low in fat but you still need to change your diet because you will still be taking in too much energy
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Fighting Disease

There are two main types of pathogens:

  • Bacteria
    • small living cells
    • reproduce rapidly
    • make you feel ill by doing two things
      • damaging cells
      • producing toxins
  • Viruses 
    • not cells, 1\100th size of a bacterium
    • replicate themselves by invading your celss and using the cells' machinery to produce many copies of themselves
    • the cell will usually then burst, releasing the new viruses
    • the cell damage is what makes you feel ill
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Fighting Disease (2)

Bodys defence system:

  • Skin, hair and mucus stops lots of nasties getting in
  • Platelets helps blood clot quickly to seal wounds
  • If something does make it in your immune system (WHITE BLOOD CELLS) kicks in
    • Consuming them
      • White blood cells can engulf foreign cells and digest them
    • Producing antibodies
      • every invading cell has unique molecule (ANTIGENS) on its surface
      • when white blood cell comes across foreign antigen, start to produce proteins called antibodies
      • these lock onto antigen and kill the cell
      • they are specific to each antigen so will not lock onto anything else
      • they are rapidly produced and taken around the body to kill similar cells
      • if person gets infected by the same pathogen, antibodies are rapidly produced so person doesnt get ill, they are immune
    • Producing antitoxins
      • counteract toxins produced by bacteria
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It protects from future infections:

  • When infected by new mcroorginism it takes white blood cells a few days to deal with it, so you get ill
  • Vaccinaions involve injecting dead or inactive microoginisms which still have their antigens, so body can produce the antibodies to kill them - body then remebers the correst antibodies for that pathogen if it ever comes across it
  • Vaccinations can wear off so booster injections might need to be given


  • They have controlled that were common disease in UK - no more smallpox, pollio down by 99%
  • Epidemics can be prevented if a large percentage is vaccinated - people arent vaccinated are less likley to get it as there is less to get it from


  • Dont always work and can give you a bad reaction
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Drugs to Fight Disease

Some drugs relieve symptoms, others cure the problem:

  • Painkillers (asprin) relieve pain
  • Others do simillar things
    • for example "cold remedies" don't actually cure colds
  • Antibiotics (penicillin) actually kill the bacteria without causing damage to your body, different antibiotics kill different bacterias
  • antibiotics don't kill viruses, viruses reproduce using your body cells which makes it difficult to develop drugs which dont kill your body cells

Bacteria can become Resistant:

  • Bacteria can mutate - makes them resistant
  • Bacteria could be resistance, so when your innfected only non-resistant strains will be killed
  • Resistance strain will survive and reproduce and become serious as nothing can treat it
    • MSRA is resistant to the powerfull antibiotic
  • To slow down the development of resistant strains doctors must not over-perscribe
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Past and Future of Fighting Diseases

Semmelweis cut deaths by using antiseptics:

  • Ignaz Semmelweis worked in Vienna Generall Hospital in 1840
  • He noticed a large amount af women died after childberth from diseases
  • Doctors spread diseases by not washing their hands, doctors washed hands with antiseptic soloution and death rates fell from 12% to 2%
  • It killed the bacteria but this was not known for another 20 years - he could not prove why and rates went up again after he left
  • Basic hygine is essentiall, although not found in some modern hospitals which causes the spread of MRSA

Antibiotic Resistance is more Common

  • Death rate of bacterial infections fallen dramatically
  • Resistance evolves - MRSA are resistant to certain antibiotics
  • Harder to get rid of bacteria and easier to pass on
  • Companies encouraged to develop new antibiotics
  • Bacteria that is resisant are known as superbugs are becoming more common
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Past and Future of Fighting Diseases (2)


  • Bacteria can mutate to produce new strains
  • Current treatments can no longer clear infections of antibiotic-resistant strains
  • No-one is immune to new strains
  • It can spread quickly with no cure and cause an epidemic


  • Often mutate, which makes it harder to develop vaccines as the antigens can change
  • If a virus mutates quickly it could become a serious problem
  • Take time to mass produce vaccines
  • Worst case flu pandemic could kill billions around the world
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The Nervous System

Sense organs detect stimuli

  • A stimulus is a change in your environment which you may need to 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 into electrical impulses
  • A stimulus can be light, sound, touch, pressure, chemical or a change in temp. or position

Central Nervous System

  • The CNS is where all the information from the sense organs is sent and where reflexes and actions are coordinated. The CNS consists of the brain and spinal cord only
  • Neurones (nerve cells) transmit the information very quickly to and from the CNS
  • 'Instructions' from the CNS are sent to the effectors (muscles and glands) which respond accordingly 
    • The eye is a sense organ. It contains light receptors
    • The ear is a sense organ. It contains sound receptors

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The Nervous System (2)

The Five Sense Organs and the receptors that each contains:

  • Eyes-Light receptors-sensitive to light. Cells contain nucleus, cytoplasm, cell membrane
  • Ears-Sound receptors-sensitive to sound-sensitive to changes in position
  • Nose-Smell receptors-sensitive to chemical stimuli
  • Tongue-Taste receptors-sensitive to bitter,salt,sweet,sour and chemical stimuli
  • Skin-Sensitive to touch, pressure, pain and temperature change

Sensory Neurones- The nerve cells that carry signals as 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 CNS to the effector (muscles or glands)

Effectors- Muscles and glands-they respond in different ways- Muscles contract in response to a nervous impulse whereas glands secrete hormones

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Synapses Reflexes

Synapses connect Neurones

  • The connection between two neurones is called a synapse
  • The nerve signal is transferred by chemicals which diffuse across the gap
  • These chemicals then set off a new electrical signal in the next neurone

Reflexes help prevent injury

  • Reflexes are automatic responses to certain stimuli- they can reduce chance of injury e.g. if someone gets a bright light in their eyes your pupils automatically get smaller so that less light gets into the eye- this stops it getting damaged
  • The passage of information in a reflex (from receptor to effector) is called a reflex arc


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Synapses and Reflexes 2

The Reflex Arc goes through the Central Nervous System

  • When a stimulus (e.g. a bee sting) is detected by receptors, impulses are sent along a sensory neurone to the CNS
  • When the impulses reach a synapse between the sensory neurone and a relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone
  • When the impulses reach a synapse between the relay neutrone and motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone
  • The impulses then travel along the motor neurone to the effector (e.g. muscle)
  • The muscle then contracts and moves your hand away from the bee

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

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Hormones are chemical messengers sent in the blood

  • Hormones are chemicals released directly into the blood. They are carried in the blood plasmas to other parts of the body, nut only affect target cells in particular places
  • Hormones control things in organs and cells that need constant adjustment
  • Hormones are produced and secreted by various glands. They travel in your body at the speed of the blood
  • Hormones tend to have relatively long lasting effects

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

The Pituitary Gland

  • They produce many important hormones such as FSH and LH which are involved in the menstrual cycle


  • Produce oestrogen which is involved in the menstrual cycle
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Hormones (2)

Hormones and Nerves do similar jobs but there are differences

  • Nerves
    • very fast action
    • act for a very short time
    • act on a very precise area
  • Hormones
    • slower action
    • act for a long time
    • act in a more general way
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The Menstrual Cycle

The Menstrual Cycle has four stages

  • Stage 1
    • day 1 is when the bleeding starts. The uterus lining breaks down for about 4 days
  • Stage 2
    • the lining of the uterus builds up again, from day 4 to 14, into a thick spongy layer full 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, then the spongy lining starts to break down again and the whole cycle starts again


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The Menstrual Cycle (2)

Hormones control the different stages

  • Three main hormones involved
  • 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
  • Oestrogen
    • Produced in the ovaries
    • Causes pituitary to produce LH
    • Inhibits the further release of FSH
  • LH (Luteinising Hormone)
    • Produced by the pituitary gland
    • Stimulates the release of an egg at around the middle of the menstrual cycle
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Controlling Fertility

Hormones can be used to reduce fertility

  • Oestrogen can be used to prevent the release of an egg
  • If oestrogen is taken everyday to keep the level of it permanently high it inhibits the production of FSH and after a while egg development and production stop
  • Progesterone (produced in the ovaries-menstual cycle) stimulates the production of thick cervical mucus which prevents any sperm getting through and reaching an egg
  • The pill-the first version was made in the 1950s and contained oestrogen and progesterone
  • There were concerns about the link between oestrogen in the pill and side effects e.g. blood clots. The pill now contains lower doses of oestrogen and has fewer side effects
    • Pros
    • The pill is 99% effective at preventing pregnancies
    • It reduces the risk of getting some types of cancer
    • Cons
    • Its not 100% effective-still a slight chance of getting pregnant
    • Can cause side effects like headaches, nausea, irregular menstrual bleeding
    • It doesn't protect against STD's
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Contolling Fertility (2)

Hormones can be used to increase fertility

  • 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 the women to stimulate egg release in their ovaries
    • Pros
    • It helps a lot of women to get pregnant when previously they couldn't
    • Cons
    • It doesn't always work-some women may have to do it many times, which can be expensive
    • Too many eggs could be stimulated, resulting in unexpected multiple pregnancies
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Controlling Fertility (3)


  • In Vitro Fertilisation involves collecting eggs from the woman's ovaries and fertilising them in a lab using the man's sperm. These 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
    • Pro
      • Fertility treatment can give an infertile couple a child
    • Cons
      • Some women have a strong reaction to the hormones e.g. abdominal pain, vomiting
      • Some reports of an increased risk of cancer due to the hormonal treatment
      • Multiple births can happen if more than one embryo grows into a baby- this is risky for the mother and babies- higher risk of miscarriage or stillbirth
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Plant Hormones

Auxin is a growth hormone

  • Controlls growth near the tips of shoots and roots
  • Its in response to light (phototropism), gravity (gravitropism or geotropism) and moisture
  • Auxin is in the tips and moves backwards to stimulate the cell elongation in the cells behind the tips
  • If tip is removed no more auxin so might be no more growth
  • Auxin promotes growth in shoot but inhibits it in the root - does not roduce the desired result

How it works:

  • Shoots grow towards light
    • Shoots exposed to light, auxim accumlates in shade
    • Makes cell grow faster on shaded side - bends towards light
  • Shoots grow away form gravity
    • When shoot is sideways auxin is produced on bottom half
    • Lower grows faster so bends towards light
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