GCSE OCR Gateway Science - B1 E-F

Drugs and You, Staying in Balance, Gene Control, Who am I?


OCR Gateway Science B1 - Drugs and You

Useful Drugs - help the body

  • Insulin - diabetics
  • Penicillin - kills bacteria
  • Aspirin - painkiller

Harmful Drugs

change how you behave and damage your body, you can become addicted.

After a long time of taking a drug, people find they need to take bigger doses to get the same effects - tolerance.

People rehabilitate when trying to give up taking a drug. They suffer withdrawal symptoms.

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OCR Gateway Science B1 - Drugs and You

Harmful Drugs

Depressants - slow down the workings of the brain - alcohol, solvents

Hallucinogens - change what a person sees or hears - cannabis, LSD

Painkillers - stop nerve impulses so no pain is felt - aspirin, heroin

Performance Enhancers - develop muscles - anabolic steroids

Stimulants - speed up the workings of the brain - caffeine, nicotine, ecstasy

Stimulants affect the nervous system by allowing more impulses pas through synapses.

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OCR Gateway Science B1 - Drugs and You

Drug Classification

CLASS A - 7 years in prison and fine for possession, life in prison for supplying

heroin, methadone, cocaine, ecstasy, LSD, magic mushrooms

CLASS B- 5 years in prison and fine for possession, 14 years in prison for supplying

amphetamines, barbiturates

CLASS C- 2 years in prison, 5 years for supplying

anabolic steroids, valium, temazepan, cannabis

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OCR Gateway Science B1 - Drugs and You

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OCR Gateway Science B1 - Drugs and You

Alcohol is measured in units.

Drinking too much alcohol over a long period of time can cause damage to the liver,(cirrhosis) brain and nervous systerm.

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OCR Gateway Science B1 - Staying in Balance

Homeostasis- the maintenance of a constant internal environment. It involves balancing daily inputs and outputs. It involves negative feedback mechanisms. Homeostatic mechanisms enable humans to live in almost every environment.

body cools down ^ too cold, vasoconstriction generates and conserves heat ^ body warms up ^ too hot, vasodilation loses heat ^ body cools down ...

Homeostasis also controls :

  • temperature
  • blood sugar levels
  • water levels
  • urea levels
  • CO2 and 02 balance

The body temperature should be maintained at 37C so that enzymes can work properly. Enzymes are damaged if the temperature is too high or ineffective if too low.

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OCR Gateway Science B1 - Staying in Balance

Secondary Sexual Characteristics

in the female :

  • breasts develop
  • hips widen
  • grow pubic hair
  • periods start

in the male :

  • become muscular
  • grow pubic and facial hair
  • voice breaks
  • testes produce sperm
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OCR Gateway Science B1 - Staying in Balance

The Menstrual Cycle - involves changes to the lining of the uterus and the ovaries. the lining breaks down on day one, the period. It then builds up ready to receive a fertilised egg.

Oestrogen rebuilds the lining of the womb. Oestrogen and progesterone control ovulation. Progesterone maintains the lining of the womb.

The contraceptive pill is made up mainly of progesterone, it stops eggs being released and fools the body into being pregnant.

Fertility hormones can cause the release of eggs.

Diabetes is caused when the body does not produce enough insulin. Insulin converts excess sugar in the blood into glycogen, which is stored in the liver. Some people need to to inject themselves with insulin to control their diabetes. The dose of insulin will depend on their diet and how active they are.

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OCR Gateway Science B1 - Gene Control


All human body cells except sex cells, gametes, have the same number of chromosomes. Cells have 46 chromosomes which make up 23 pairs. Different species have different overall numbers of chromosomes.

Chromosomes carry information in the form of genes. Chromosomes are long coiled molecules of DNA divided into regions called genes.

Each gene contains a different sequence of bases and this coded information is called the genetic code.

The genetic code controls cell activity and some of the characteristics of the organism. All genes are in every cell but only some of them are switched on in different cells, so they perform their specific function.

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OCR Gateway Science B1 - Gene Control

Facts about DNA

  • It is the code that makes a human being.
  • It can copy itself exactly so the code can be passed on to the next generation.
  • It is coiled into a double helix so that it is very small.
  • It is so small that it can be stored in the nucleus of every cell.
  • It controls how cells function by controlling protein production.
  • It is made of chemicals called bases.
  • There are four bases whose names are represented by A, T, C and G.


When gametes join together during fertilisation, the full number of chromosomes is restored to 46. A baby inherits half it DNA from its mother and half from its father, making it a unique individual. Identical twins have exactly the same DNA. Everyone else has different DNA and this leads to variation.

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OCR Gateway Science B1 - Who am I?

Variation occurs because we inherit different combinations of genes from our parents. Variation is also caused by random fertilisation. Any sperm can fertilise any egg, and both contain different combinations of genes.

Mutations - changes when DNA is damaged. A mutation is a :

  • change in the sequence of bases
  • removal of one or more bases
  • addition of one or more bases.

Mutations can be beneficial or harmful. Most are harmful. Mutations can be casued by radiation or chemicals or they can occur spontaneously.

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OCR Gateway Science B1 - Who am I?

If a mutation occurs in the production of a gamete, the mutation can be passed on to the next generation. These gene mutations are usually recessive and are masked by the correct gene from the other parent. Occasionally a baby gets a faulty gene from both parents, and then the baby will not be healthy. This is why a child may have cystic fibrosis.

Inheritance of sex - is controlled by whole chromosomes not individual gens. Humans have two sex chromosomes, X and Y. Males have one X chromsome and one Y chromosome whereas females have two X chromosomes. The punnet square shows how sex is inherited.


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OCR Gateway Science B1 - Who am I?


Cells in a baby contain two complete sets of instructions, one from the mother an done from the father. This means there are two versions of every gene, called alleles. The baby only uses one of each pair of alleles.

Dominant allele - these alleles are the code that is used

Recessive allele - these alleles are the code that is not used

Homozygous - two alleles are the same

Heterozygous - two alleles are different

The dominant allele is alsways represented by a capital letter. The recessive allele is represented by the same letter in lower case.

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Thanks these notes are really useful

Kamya Gopal


Thanks so much. Have a Biology mock in a week and these are really helpful... Thanks!!!

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