Biology 1a-Human Biology

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Diet and Metabolic Rate

Metabolic rate: the speed at which energy reacts with the chemicals in your body

There are variations in the resting metabolic rate of different people e.g. muscle needs more energy than fatty tissue so people with higher proportion of muscle to fat in their bodies will have a higher metabolic rate

Physically bigger people will have higher MR because the bigger you are the more energy your body needs

Men tend to have higher MR than women because they tend to be bigger and have larger muscle proportion

--Regular exercise boosts MR because it builds muscle--

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Factors Affecting Health

Eating too much can lead to obesity

  • Excess carbohydrates or fats  and hormonal problems can lead to it
  • It is a common disorder in developed countries--its defined as being 20+% over maximum recommended body mass
  • Health problems:
    • arthiritis, type 2 diabetes, high blood pressure, heart disease
  • Too much saturated fat can increase blood cholesterol level
  • Too much salt can cause high blood pressure and heart problems

Eating too little can cause health problems

  • The effects of malnutrition vary depending on which foods are missing from the diet
    • slow growth (in children), poor resistance to infection, irregular periods
  • Deficiency diseases are caused by lack of vitamins and minerals
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Factors Affecting Health 2

Not getting enough exercise can affect your health

  • Exercise increases the amount of energy used by the body and decreases the amount of stored fat. It also builds muscle which boosts MR
  • However, sometimes people can be fit but not healthy e.g. they can be physically fit and slim but malnourished at the same time because of their unbalanced diet

Inherited factors can affect your health

  • Some inherited factors can cause an underactive thyroid gland which can lower the MR and lead to obesity
  • Some can inherit factors that affect their blood cholesterol level.
  • Cholesterol is a fatty substance that is essential for good health- it's found in every cell of the body
  • Some inherited factors increase BCL which increases risk of heart disease


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Fighting Disease

There are two main types of pathogens--Bacteria and Viruses

  • Bacteria are very small living cells
    • They produce rapidly inside your body
    • They make you feel ill by damaging your cells and producinng toxins
  • Viruses are not cells
    • They replicate themselves by invading your cells and using its machinery to make copies. The cell will then burst releasing new viruses

The Bodies Defence System

  • Your skin, hair and mucus in the respiratory tract stop bad things getting into the body
  • To prevent microorganisms getting into the body through cuts, platelets help blood clot quickly to seal the wound. If blood contains low no. of platelets it'll clot more slowly
  • If something does get through the immune system 'kicks in'. The white blood cells travel round the body to check for microbes. When they come across them they have three lines of attack (next page)
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Fighting Disease 2

White Blood Cells three lines of attack

  • Consuming Them
    • White blood cells engulf foreign cells and digest them
  • Producing Antibodies
    • Every invading cell has unique molecules on its surface called antigens
    • When the WBC comes across a foreign antigen it'll start to produce proteins called antibodies to lock onto &kill the invading cell. The antibody is specific to the antigen
    • Antibodies are then produces rapidly and carried around the body to kill 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 it
  • Producing Antitoxins
    • These counteract toxins produced by the invading bacteria
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Fighting Disease-Vaccination

Vaccinations protect from future infections

  • Vaccinations involve injecting small amounts of dead or inactive microorganisms. These carry antigens which cause your body to produce antibodies to attack them
  • If live microorganisms of the same type appears after that the WBC can rapidly mass-produce antibodies to kill off the pathogens

Pros of vaccination

  • They have helped control lots of infectious diseases that were once common in the UK--small pox no longer occurs and polio infections have fallen by 99%
  • Big outbreaks of disease (epidemics) can be prevented if a large percentage of the population is vaccinated. Even if people aren't vaccinated they have little chance of catching the disease because there are fewer people able to pass it on

Cons of vaccination

  • They don't always work
  • Sometimes can have a bad reaction to the a vaccine (swelling, fever, seizure)
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Fighting Disease-Drugs

Some drugs just relieve symptoms, others cure the problem

  • Painkillers are drugs that relieve pain and help reduce symptoms (aspirin)
  • Antibiotics actually kill the bacteria causing the problem without killing the body cells
  • But, antibiotics don't destroy viruses. Viruses reproduce using the body cells so it is very hard to develop drugs that destroy the virus without killing the body's cells

Bacteria can become resistant to antibiotics

  • Bacteria can mutate- sometimes this causes them to be resistant to an antibiotic
  • This means when you treat the infection only the non-resistant strains can be killed
  • The resistant bacteria will survive and reproduce and the population of the resistant strain will increase (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
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Fighting Disease-Drugs 2

You can investigate antibiotics by growing microorganisms in the lab

  • Microorganisms are grown in a 'culture medium'. This is usually agar jelly containing the carbohydrates, minerals, proteins and vitamins they need to grow
  • Hot agar jelly is poured into a petri dish
  • When the jelly has cooled and set, inoculating loop (wire loops) are used to transfer microorganisms to the culture medium. They then multiply
  • Paper discs are soaked in different types of antibiotics and placed on the jelly. Antibiotic-resistant bacteria will continue to grow around them but the non-resistant strains will die
  • The petri dish, culture medium and inoculating loops must be sterilised before use (stops any unwanted microorganisms growing and affecting the results)
  • The petri dish must also have a lid to stop any microorganisms in the air contaminating the culture. The lid should be taped on
  • In school labs the microorganisms are kept at about 25*C because harmful pathogens aren't likely to grow at this temperature
  • In industrial conditions cultures are incubated at higher temperatures so they can grow a lot faster
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Fighting Disease-Past and Future

Semmelweis cut deaths by using antiseptics

  • While Ignaz Semmelweis was working in Vienna General Hospital in the 1840s, he saw that women were dying in huge numbers after childbirth froma disease called puerperal fever
  • He believed that doctors were spreading the disease on their unwashed hands. By telling the doctors who entered 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 the doctors' hands, though Semmelweis didn't know this so he couldn't prove why his idea worked and his methods were dropped when he left the hospital allowing the death rates to go back up

Antibiotic resistance is becoming more common

  • Bacterial infections have been easily treated with antibiotics. Death rate fallen a lot
  • Bacteria evolves antibiotic resistance and overuse of antibiotics has made it worse
  • People who become infected can't easily get rid of it and may pass it on to others
  • This encourages drug companies to work on developing new antibiotics that are effective against the resistant strains


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