Biology GCSE (1)

Science A GCSE - Biology

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DIET AND EXERCISE

Balanced diet - carbonhydrates, proteins, fats, vitamins, minerals, fibre, water.

No balanced diet = malnourished.


Metabolic rate - the rate of the chemical reactions which take place in cells.

 

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PATHOGENS AND DISEASE

Infectious diseases are caused by microorganisms called pathogens, such as bacteria and viruses.

Bacteria and viruses reproduce rapidly inside your body. Bacteria can produce toxins which make you feel ill.

Viruses damage your cells as they reprodue. This can also make you feel ill.

Semmelweiss recognised the importance of hand washing to prevent the spread of infectious diseases in hospital. 

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DEFENCE MECHANISMS

PATHOGENS SPREAD BY:

  • Droplet infection - coughing, sneezing or talking passes pathogens onto someone else.
  • Direct contact - sexually transmitted diseases.
  • Contaminated food and drink - eating raw/uncooked food, drinking contaminated water, takes pathogens straight into your gut.
  • Through a break in your skin - pathogens can enter body through cuts and scratches and neddle puncutres. 

WHITE BLOOD CELLS:

  • Ingesting microorganisms - some ingest pathogens and destroy them.
  • Producing antibodies - some produce antibodies, the antibody attach to the antigen (on the bacterium) and kill it. Once the white blood cell has already produced that antibody once, it's quicker next time that pathogen enter the body.
  • Producing antitoxins - some produce antitoxins, these cancel out the toxins released by the pathogen by joining onto it.
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MEDICINES

Some medicines relieve the symptoms but don't kill the actual pathogen.

Antibiotics cure bacterial diseases by killing the bacteria inside your body.

Antibiotics do not destroy viruses because viruses reproduce inside the cells, you can't have a drug to destroy a virus without damaging your body cells. 

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IMMUNITY

You can be immunised against a disease by giving your body a small inactive amount of the pathogen.

Small amount of the pathogen is injected 

----->

White blood cells make antibodies to destroy the anigens

----->

You are immune because your body knows the correct antibody to produce if the pathogen enters your body again.

Vaccines protect against bacterial and viral pathogens.

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NERVOUS SYSTEM

Nervous system carries electrical signals called impulses.

A stimuli (change around you e.g. pin in finger) is picked up by cells called receptors (skins, eyes, ears etc.) 

Once the receptor picks up a stimuli it sends electrical impulses along neurons.

The neuron travels to the CNS (central nervous system) which is the brain and spinal cord.

Motor neurons carry this information from the CNS to the rest of the body.


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REFLEX ACTIONS

Nervous system: receptor --> sensory neuron --> coordinator (CNS) --> mortar neuron --> effector

Reflex arc: 

 ---  stimulus (touching a hot plate)

--> sensory receptor (pain on skin)

--> SENSORY NEURON --> RELAY

--> synapse

--> CNS (spinal cord)

--> MORTAR NEURON

--> muscle (bicep muscle contracts and pulls hand away).


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SYNAPSE

When an impulse arrives at the junction between two neurons they can't jump the gap....

---  Impulse arrives at the synapse

--> Vesicle with neurotransmitter

--> Neurotransmitter is released across the synaptic cleft

--> Neurotransmitter fits onto the receptors on the membrane of the second neuron.

--> Impulse triggered in the second neuron

--> Neurotransmitter are recycled and go back into the cycle.

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HORMONES MENSTRUAL CYCLE

1. FSH - released from the pituitary gland, transported in the blood and causes egg to mature in ovary.

2. FSH - stimulated ovary to release oestrogen.

3. Oestrogen released from ovary + transported in blood.

4. Oestrogen - prevents further release of FSH from pituitary.

5. Oestrogen - stimulates pituitary gland to release LH.

6. LH - released from the pituitary gland + transported in blood.

7. LH causes ovary to release egg.

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ARTIFICIAL CONTROL OF FERTILITY

Fertility drug: contains FSH to stimulate the egg and helps get pregnant.

IVF: produces test tube baby, helps the egg to fertilize and then put back in the womb to help get pregnant.

Oral contraceptive: to stop concieving, tablet containing oetrogen and progesteron

Homeostasis: is maintaining a constant internal environment, helped by the nervous and hormonal systems. 

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