Biology Unit 1

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A Healthy Diet

A healthy diet needs to include the right amounts and proportions of nutrients and energy that the body needs to stay healthy.

Food contains:

>carbohydrates, fats and proteins                                              >mineral ions and vitamins

  Used in the body to:                                                                Needed in small amounts

  • release energy                                                                      so cells can work properly
  • provide nutrients to build cells                                                       

A person who doesnt eat a balanced diet will become malnourished. Possible effects on malnutrition include:

  • being overweight or underweight
  • deficiency diseases caused by a lack of a nutrient
  • conditions such as type 2 diabetes.              
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Controlling Mass

Metabolic Rate

Is the rate at which chemical reactions take place in the body, they are affected by many factors:

  • how much muscle you have 
  • how much exercise you do
  • some inherited factors in your genes.

The body gains energy from food and energy is expended (used) during exercise. The balance between energy taken in and expended affects your mass.

Body loses mass:                                                                 

  • more energy expended in exercise than gained in food

 Body gains mass:

  • more energy gained in food than expended in exercise
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Lifestyle Is the way we live, including what we eat and do, which affects how active we are. These factors can harm health and lead to disease.

Exercise: a person who exercises regularly is more likely to stay healthy than a person who doesn't. 

Benefits of exercise include: 

  • better weight control
  • better health

Inherited Factors

These are not lifestyle factors, but they can affect health. For example, some people inherit genes that give them a higher blood cholesterol level than other people even if they eat the same diet.

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  • Microorganisms are organisms that can only be seen under a microscope, they are to small to be seen by the naked eye.
  • Fungi, bacteria and viruses are all types of microorganisms.
  • Many microorganisms can be useful, eg. bacteria can be used to make yoghurt and the fungus 'yeast' can be used to produce bread.
  • Some microorganisms can be harmful. They ones that cause disease are called pathogens.

Fungi > Bacteria > Viruses       


  • Ignaz Semmelweis was a doctor in the mid-1800s who wondered why many women died of infection soon after childbirth.
  • He realised doctors might be transferring infection between patients on their hands. He told them to wash their hands between seeing patients. Resulted in a decrease in the amount of child bed fever. No one took his research seriously.
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Microorganism Structure

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Microorganisms Reproducing - Viruses


1) They take over a body cell

2) In the warm enviroment, they use the cell to reproduce

3) They inject the cell with their own DNA which tells it what to do

4) When enough viruses have been made, they burst out of the cell

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Microorganisms Reproducing - Bacteria


1) To reproduce, the bacteria copies its own DNA loop

2) When two identical loops have been made, the bacteria splits in two.

3) They both contain the same DNA and can repeat the process.

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The Immune System - Ingesting Microbes

White blood cells

1) Ingesting microbes 

  • The white blood cell changes shape to engulf the pathogen
  • It the ingests the pathogen
  • The WBC produces enzymes that destroy it
  • Any products that are left are absorbed by the WBC
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The Immune System - Producing Antibodies

2) Producing Antibodies

  • Pathogens have antigens on their surface
  • Each pathogen has differently shaped antigens
  • The WBC produced antibodies to fit onto the antigens
  • The antibodies attach onto the antigens and the pathogen is destroyed
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The Immune System - Producing Antitoxins

3) Producing Antitoxins

  • Bacteria produces toxins that can cause illness.
  • The WBC produces antitoxins specifically shaped to fit the toxins
  • The antitoxins attach to the toxins and the pathogen is destroyed.
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Structure of an Animal Cell

1) The nucleus contains the cell's DNA, the instructions for life

2) The mitochondria, respiration happens here

3) The cell membrane allows substances to get in and out of the cell

4) The ribosomes, they are like robots that build proteins

5) The cytoplasm, where chemical reactions take place.

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Analgesics and Antibiotics

  • Analgesics like aspirin kill pain
  • Antibiotics like penicillin kill bacteria
  • Antibiotics only kill bacteria, they have no effect on viruses

Working with Bacteria : Aseptic technique

  • Prevent contamination of working area
  • prevent contamination of results
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Antibiotic Resistance

Anitbiotic resistance is a mutation, a random, accidental change in DNA.

The 'mutant' resistance is only at an advantage when we use antibiotics.

  • Mutations of pathogens produce new DNA strains
  • Antibodies may no longer be effective against a new resistant strain of the pathogen
  • To prevent further resistance arising, it is importnat to avoid over-use of antibiotics
  • People who were vaccinated against the old strain are not immune to the new strain
  • The new strain may spread rapidly causing an epidemic or pandemic disease
  • Causes problems for hospitals as patients who suffer from a weak immune system wll be easily infected and doctors will be unable to use antibiotics to treat them.
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Artificial Immunity


A vaccination involves introducing dead or weakend pathogens into the body.

  • We inject the vaccine into a person who has never had the disease
  • After a while, WBCs detect the weakend microorganisms 
  • WBCs make antibodies to fit the microorganisms
  • The microorganisms are destroyed
  • The person becomes infected with the harmful form of the disease
  • The harmful microorganisms are detected immediatly and antibodies are made
  • Antibodies destroy the harmful microorganisms before they make you ill

MMR is a vaccine used to defend the body against MeaslesMumps and Rubella (german measles)

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The Nervous System

The nervous system enables animals to detect changes in their surroundings and coordinate an appropriate response.


Nervous impulse: The eletrical signal that travels through the nervous system, they are the means by which infomation travels - along nerve cells and neurones.

Effector: A muscle or gland that acts in response to a stimulous

Receptor: A group of specialised cells, they can detect changes (stimuli) and generate eletrical impulses

Motor Neurone: They carry signals from the CNS to the effectors

Sensory Neurone: Carry signals from receptors to the spinal chord and brain

Co-Ordinator: The brain co-ordinates responses to the signals

Connector Neurone: Forms connection between the other neurones - they are located in the co-ordinators

Stimulous: Change in the surroundings

Response: Reply to the signals, the final action.

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The Nervous Impulse Pathway








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Animals have receptors in their sense organs which detect stimuli

A sense organ contains lots of receptor cells

  • Eye - light
  • Ear - position of the head and sound
  • Nose - chemicals in the air (smell)
  • Tongue - chemicals in solids/liquids (taste)
  • Skin - touch/pressure/pain/temperature
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A Synapse

1) Nerve impulse arrives at the end of the neurone

2) Vesicles (sacs of chemicals) move towards the membrane of the nerve cell and then they fuse with the membrane

3) The chemicals are released into the synapse and diffuse across the gap

4) The chemicals are detected by receptors in the next cells membrane

5) A new impulse is generated and it travels on

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Reflex Actions

A reflex action is extremly quick, there are only three different neurones involved.


1) A receptor detects a stimulus 

2) Sensory neurone transmits the impulse the the CNS 

3) Relay neurone passes the impulse on 

4) A motor neurone is stimulated

5) Impulse passes to the effector (muscle or gland)

6) Action is taken - a response

This sequence is a reflex arc

The impulse will travel to the closest co-ordinator, so it could be the brain or the spine.

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