GCSE AQA Core Chemistry – Plant Oils – C1.6

Plant Oils

6.1 Extracting vegetable oil

Vegetable oils can be extracted from seeds, nuts and fruits by pressing or by distillation.
Vegetable oils provide nutrients and a lot of energy. They are important foods and can be used to make biofuels.
Unsaturated oils contain carbon-carbon double bonds (C=C) and so they decolourise bromine water.

Some oils are extracted from seeds, nuts and fruit by pressing them. Some oils are extracted by distilling the plant material mixed with water. This produces a mixture of oil and water from which the oil can be separated.
Vegetable oils release a lot of energy when they burn in air and so can be used as fuels. They are used to make biofuels such as biodiesel.
The molecules in vegetable oils have hydrocarbon chains. Those with carbon-carbon double bonds (C=C) are unsaturated. If there are several double bonds in each molecule, they are called polyunsaturated. Unsaturated oils react with bromine water, turning it from orange to colourless.

6.2 Cooking with vegetable oils

Vegetable oils are useful in cooking because of their high boiling points.
Cooking in oil increases the energy content of foods and changes the flavour, colour and texture of the food.
Vegetable oils can be hardened by reacting them with hydrogen at 60 degrees with a nickel catalyst. This makes them solids at room temperature that are suitable for spreading.

Unsaturated oils can be reacted with hydrogen so that some or all of the carbon-carbon double bonds become single bonds. This reaction is called hydrogenation and is done at about 60 degrees using a nickel catalyst. The hydrogenated oils have higher melting points because they are more saturated. The reaction is also called hardening because the hydrogenated oils are solids at room temperature. This means they can be used as spreads and to make pastries and cakes that require solid fats.

6.3 Everyday emulsions

Oils do not dissolve in water but oils and water can be used to produce emulsions. These have special properties.
Emulsions made from vegetable oils are used in many foods.
Emulsifiers stop oil and water from separating into layers.
Emulsifiers have molecules in which one part is hydrophobic and the other part is hydrophilic.

Oil and water do not mix and usually separate from each other, form in two layers. If we shake, stir or beat the liquids together, tiny droplets form that can be slow to separate. This type of mixture is called an emulsion.
Emulsions are opaque and thicker than the oil and water they are made from. This improves their texture, appearance and their ability to coat and stick to solids. Milk, cream, salad dressings and ice cream are examples of emulsions. Some water-based paints and many cosmetic creams are also emulsions.
Emulsifiers are substances that help stop the oil and water from separating into layers. Most emulsions contain emulsifiers to keep the emulsion stable.

Emulsifier molecules have a small hydrophilic part and a long hydrophobic part. The hydrophilic part or ‘head’ is attracted to water. The hydrophobic part or ‘tail’ is attracted to oil. The hydrophobic parts of many emulsifier molecules go into each oil droplet, and so the droplets become surrounded by the hydrophilic parts. This keeps the droplets apart in the water, preventing them from joining together and separating out.

6.4 Food issues

Vegetable oils are high in energy and provide nutrients.
Vegetable oils are believed to be better for health then saturated fats.
Emulsifiers improve the texture of foods enabling water and oil to mix. This makes fatty foods more palatable.

Vegetable oils contain unsaturated fats, that are believed to be better for you than saturated fats.
Animal fats and hydrogenated vegetable oils contain saturated fats and are used in many foods. Saturated fats have been linked to heart disease.
Emulsifiers stop oil and water spreading into layers. This makes foods smoother, creamier and more palatable. However, because they taste better and it is less obvious that they are high in fat, you may be tempted to eat more.


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GCSE AQACore Chemistry – Our Planet – C1.1

Our Changing Planet

1.1 Structure of the Earth
✤ The Earth is made of layers called the core, mantle and crust with the atmosphere around the outside.
✤ The Earth’s limited resources come from its crust, the oceans and the atmosphere.
✤ The Earth is almost spherical, its diameter is about 12,800 km. At the surface is the crust, a very thin layer, ranging from about 5km to 70km.
✤ The mantle is under the crust and is about 3000km thick. It goes to about halfway to the centre. It is mostly solid, but some parts can flow slowly.
✤ The core is about half the diameter of the Earth. It contains lots of iron and nickel. It has a liquid outer part and a solid inner part.
✤ The atmosphere surrounds the earths surface. Most of the air is within 10km of the surface and the whole atmosphere is 100km from the surface, further than that is space.

1.2 The Restless Earth
✤ The Earths crust and upper mantle is cracked into tectonic plates which are constantly moving.
✤ The tectonic plates move because of convection currents in the mantle that are caused by natural radioactive decay.
✤ Earthquakes and volcanoes are formed when tectonic plates meet , and it is difficult to accurately predict when earthquakes will happen.
✤ Wegener’s theory of continental drift was mainly correct, but was not accepted for many years.

✤ When plates meet, huge forces build up. Eventually rocks give way, changing shape or moving suddenly. This causes earthquakes, volcanoes and mountains to form.
✤ Scientists do not know exactly what exactly happens within the Earth, so it is not easy to predict earthquakes.
✤ In 1915 Alfred Wegener put forward his idea of continental drift, but scientists did not believe him at the time as he had little evidence. They believed that the Earth was shrinking as it cooled. In the 1960’s scientists found new evidence and the theory of plate tectonics was developed.

1.3 The Earth’s atmosphere in the past
✤ The Earth’s atmosphere was formed by volcanic activity.
✤ It probably consisted mainly of carbon dioxide. There may also have been water vapour together with traces of methane and ammonia.
✤ As plants spread over the Earth, the levels of oxygen in the atmosphere increased.
✤ Scientists think that the Earth was formed about 4.5 billion years ago. In the first billion years, the Earth was covered in volcanoes that released carbon dioxide, water vapour and nitrogen.
✤ The water vapour then condensed to form the oceans. Some scientists believe that there was possibly methane and ammonia.
✤ In the next two billion years, plants bacteria and algae evolved. This increased the amount of oxygen in the atmosphere.

1.4 Life on Earth
Note: One theory of life on earth states that the compounds needed came from reactions involving hydrocarbons and ammonia with lightning provided energy.

1.5 Gases in the atmosphere
✤ Most of the carbon dioxide in the early atmosphere became locked up in sedimentary rocks.
✤ About 80% of the atmosphere is nitrogen and about 20% is oxygen.
✤ The main gases in the air can be separated by fractional distillation. These gases are used in industry as raw materials.
✤ Plants took up lots of carbon dioxide from the atmosphere, and as animals ate the plants carbon ended up in sedimentary rock. Fossil fuels contain carbon and hydrogen from plants and animals.
✤ Carbon dioxide dissolves in the oceans and some probably formed insoluble carbonate compounds that were deposited on the seabed and became sedimentary rocks.
✤ By 200 million years ago, the proportion of gases in the air had stabilised and are similar to the proportions today.
✤ Separating gases in air – the gases in air have different boiling points so can be separated from liquid air by fractional distillation.
✤ The fractional distillation of liquid air – the air is cooled to below -200 degrees and fed into a fractional distillation column. Nitrogen is separated from oxygen and argon and further distillation is used to produce pure oxygen and argon.

1.6 Carbon dioxide in the atmosphere
✤ Carbon moves into and out of the atmosphere due to plants, animals, oceans and rocks.
✤ The amount of carbon dioxide in the Earths atmosphere has risen in the recent past largely due to the amount of fossil fuels we now burn.


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GCSE AQA Additional Biology – Tissues and Organs – B2.1 

Cells, Tissues and Organs 

Key Summary Points for your 2015 Exam 🙂 

  • Mitochondria where energy is released during aerobic respiration.
  • Ribosomes where protein synthesis takes place. 
  • Plant and Algal Cells also have a rigid cell wall for support, made of cellulose, chloroplasts for photosynthesis and a permanent vacuole containing cell sap.  

  • Bacterial Cells have a cell membrane, a cell wall and a cytoplasm. 
  • Bacteria does not have a nucleus so the genetic material is in the cytoplasm.  
  • Yeast is a single celled organism and they have a nucleus, cytoplasm, cell wall and a membrane.

  • Diffusion is the spreading out of particles of gas or a substance in a solution. 
  • The net movement in and out of cells depends on the concentration either side of the membrane. 
  • As the particles move randomly, there will be a net movement from a higher concentration to a lower concentration. This is the concentration gradient. 
  • Examples of diffusion include: oxygen into the bloodstream, carbon dioxide into plants and amino acids from the gut through cell membranes. 

Plant tissues include: epidermal tissue, which covers the plant and mesophyll, which can photosynthesise. 

GCSE AQA Core Biology – Adaption and Evolution – B1.6

Adaption and Evolution

6.1 Adapt and Survive

All organisms need a constant supply of materials to survive. They get these from other organisms and their surroundings.
Organisms adapt to their surroundings to survive.
Microorganisms have a wide range of adaptions that enable them to survive in extreme places.

Most organisms live in climates below 40°C.
Extremophiles live in conditions where other animals couldn’t (i.e. over 40°C).

6.2 Adaption in Animals

Most animals have adaptions suited for their surroundings, e.g. fur, camouflage.
Bigger animals have smaller surface areas compared to their volume. They can conserve energy but it is more difficult to cool down.
In hot, dry conditions, animals are adapted to conserve water and stop them getting too hot. They hunt at night so they can keep cool during the day.

6.3 Adaption in Plants

Plants need water, nutrients, light and space to grow.
Plants lose water vapour through their stomata. It can be conserved if the plat has small or waxy leaves. Some plants are swollen to hold more water and have extensive roots for extraction.
Plants in the desert become more adapted to conserve water.
Plants are eaten by herbivores, they develop throns, poisonous chemicals and have warning colours to perterb animals.

6.4 Competition in Animals

Animals compete for:
Food
Water
Space
Mates
Breeding sites/territory
Predators compete for their prey. Prey compete against each other to escape from predators and to find food.

6.5 Competition in Plants

Plants compete for: light, water and mineral ions.
Plants are adapted (longer roots, thicker stem, waxy/small leaves) to compete for these factors.
Plants are adapted to spread their seeds far:
Via fruits and seeds
Via other animals digestion
Via wind
Via mini-explosions
Via animals fur

6.6 Measuring Environmental Change

Changes in the environment affect animal and plant life.
Non-living factors include:
Temperature
Light
Oxygen levels
Rainfall
Living factors include:
The arrival of a new predator
A new disease
New plants which may provide new habitats or food
Lichens indicate the level of air pollution and sulphur dioxide. The more lichen, the cleaner the air. They are an indicator species.
Freshwater invertibrates indicate the level of water pollution. Especially the concentration of dissolved oxygen. The wider the range of species, the cleaner the water.
Equipment such as thermometers, rain gauges, oxygen and pH indicators monitor the environment.

6.7 Theories of Evolution

Jean-Baptiste Lamarck suggested the theory of ‘inheritance of acquired characteristics’. Where a trait developed over an organisms lifetime would be passed on to their offspring.
Charles Darwin suggested the theory of ‘natural selection’. Small changes in random mutations over time took place. The organisms with the advantageous characteristics would survive to breed. It would then be passed on and survive in the species.

6.8 Accepting Darwins Ideas

The theory of evolution challenged the idea that God made all plants and animals.
Many scientist disputed the evidence Darwin gave.
Scientists did not know about genetics, and Darwin could not explain inheritance.
Darwin used the example of the finches evolving to suit their surroundings, but could not explain it, in terms of genes, why the offspring inherited the characteristics.

6.9 Natural Selection & Classification

Natural selection works because the fittest organisms survive to breed. If a gene changes, the new characteristic may enable the organism to survive better.
Biologists use a natural classification system.
The largest groups are called kingdoms. The plant, animal and the Kingdom which contains microorganisms.
The smallest classification group is the species. These breed together to produce fertile offspring. Evolutionary trees can be drawn to show evolutionary relationships.


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GCSE AQA Core Biology – Variation – B1.5

Variation, Reproduction & New Technology

5.1 Inheritance

The nucleus of a cell contains chromosomes.
Chromosome threads carry genes.
In gametes, there is only a single set of chromosomes, so that the offspring contains a set of full genes, from the two sets.
In the body most chromosomes are in pairs, one set from the mother and one from the father.

5.2 Types of Reproduction

In asexual reproduction no gametes join.
Asexual reproduction uses clones.
Clones are identical to their parents.
Sexual reproduction leads to variety within the offspring.

5.3 Genetic and environmental differences

Differences in characteristics can be due to:
Differences in genes.
Conditions that have developed.
A combination of genetic and environmental causes.
Plants may be affected by:
Light.
Nutrients.
Space to grow.
Different conditions whilst growing affects people, e.g. More food and training will develop muscles and the individual will grow more.

5.4 Cloning

Plants can be cloned from cuttings or via tissue culture. This is more expensive, but produces high numbers of the plant.
Embryo transplants are used to clone animals, each group of genetically identical cells is transplanted and grown in a host animal.
Plants can be genetically modified to produce useful substances before they are cloned.

5.5 Adult Cell Cloning

The nucleus of an adult cell (e.g. skin cell) replaces the nucleus of an egg cell.
The nucleus is removed from an unfertilised egg cell. The nucleus is removed from the skin cell and placed inside the egg cell without the nucleus.
The new cell is given an electric shock which starts the division process. It forms an embryo.
Once the embryo has developed, it is inserted into the womb of the host mother.

Advantages – animals can be engineered to produce substances that can be used in medicine or industry. Cloning can save animals from extinction.
Disadvantages – there are ethical concerns with cloning. Cloning limits the gene pool and prevents natural selection.

5.6 Genetic Engineering

Genetic engineering can transfer a gene from one organism to another.
Enzymes ‘cut out’ a gene from a human chromosome and then it is inserted into a bacterial cell.

This may be done to give the organism a desired characteristic.
The gene to produce insulin can be placed in bacteria, to mass produce this chemical.
GM crops have a higher yield and solves problems.
Insects are affected by GM crops and there may be effects on humans.
Medicines can be produced via genetic engineering, e.g. Insulin.


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GCSE AQA Core Biology – Medicine – B1.4

Medicine and Drugs

4.1 Developing new medicine

New drugs have to be throughly tested before they can be sold.
Drugs are tested to find their effectiveness, toxicity and to see if they cause side effects.
Thalidomide was developed as a sleeping drug but not tested for preventing morning sickness, so some babies had birth defects.

The first steps involve testing on cells and tissue culture. It is then tested on animals, and then human volunteers. Then it is given to patients.
Healthy are given very low doses of the drug to find out if it is safe.
In some trials, placebos are used. They do not contain the drug. Half the patients are given the drug and the other half the placebo. This is to test wether the drug actually has an effect on the patient.
In a double-blind trial, neither the doctor nor the patient knows who is given the drug. Side effects are an important aspect of testing drugs.

Thalidomide was developed as a sleeping pill, but doctors realised it could control morning sickness in pregnant women, unfortunately it had not been tested for use in pregnancy.

Some babies were born with defects and so the drug was banned and the rules for testing were improved. It is now used to treat leprosy, but not given to pregnant women.

4.2 How effective are medicines?

Statins are drugs which lower blood cholesterol levels. Their use has lowered cardiovascular disease in the population by over 40%.
Double-blind trials should be used to check if both non-prescribed and prescribed drugs actually work.

Statins are drugs which lower the amount of low density lipoproteins carried in the blood
Some illnesses can be cured with non-prescribed herbs and the only ways to test their effectiveness is to conduct double-blind trails.

4.3 Drugs

Drugs are chemicals which alter the body’s chemistry.
Legal and illegal drugs may harm your body.
Some are addictive and may cause mental health problems.

4.4 Legal and Illegal drugs

Many recreational drugs cause mental health problems and damage to the nervous system.
More people use legal drugs, which have abetter impact on your health, compared to illegal drugs.

Recreational drugs have adverse affects on the heart and circulatory system. These include cannabis and heroin.
They affect the nervous system and this can make us addicted.
Caffeine, nicotine and alcohol are recreational drugs and are also legal. However there are many health problems associated with these legal, recreational drugs. For example; alcohol poisoning, lung disease, etc.

4.5 Does cannabis lead to hard drugs?

Contact with drug dealers can lead to harder drugs.
The chemicals in cannabis smoke may cause mental illness in some people, particularly teenagers.
Cannabis increases the risk of depression.
Not everyone who smokes cannabis goes onto harder drugs.

4.6 Drugs in Sport

Steroids are drugs which are used to build up muscle mass. Other drugs may be used to increase stamina. Strong pain killers are also used to ignore injury and suffer further damage.
Using performance-enhancing drugs can lead to permanent damage to the body and can lead to death.


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GCSE AQA Core Biology – Coordination – B1.3

Coordination and Control

3.1 Responding to Change

The nervous system has receptors that detect stimuli.
The receptors are found in the sense organs.
Light stimulates the receptors in the eyeing electrical impulses pass to the brain along neurons.
Sensory neurons carry impulses carry impulses from the receptors to the CNS (brain + spinal cord)
Motor Neurons carry impulses from the CNS to the effectors which are muscles and glands. The muscles respond by contracting and the glands respond by secreting chemicals.

3.2 Reflex Actions

The response to the stimulus explained above is a reflex action.
The junction between two neurons is a synapse. Chemicals emit he impulse across he gap and the sequence from receptor to effector is a reflex arc.

3.3 Hormones and the Menstrual Cycle

FSH is made in the pituitary gland and causes the egg to mature and oestrogen to be produced.
Oestrogen is produced by the ovaries and tops further production of FSH (inhibits it). It stimulates LH production and also makes the womb lining develop to receive the egg.
LH is also made by the pituitary gland and releases the egg from the ovary.

3.4 The Artificial Control of Fertility

Contraceptive pills contain oestrogen and progesterone to stop/inhibit FSH.
FSH can also be given to a woman to help her produce eggs.

LH can also be given as fertility treatment. It stimulates ovulation and FSH causes eggs to mature.

3.5 Controlling Conditions

The body controlles its internal environment. This includes:
Water content
Ion content
Temperature
Blood sugar levels
It is important to keep temperature constant, as enzymes will not work otherwise.
Sugar in he blood is an energy source for cells. The level of sugar in our blood is controlled by the pancreas.

3.6 Hormones and the Control of Plant Growth

Plant shoots grow towards light. This response is phototropism.
Roots grow down towards gravity. This is gravitropism.
Roots also grow towards water.
Hormones which control these are auxins.
The bending of a shoot or root may be because of too much of an auxin.
Plant hormones have use in agriculture, as weed killers or to make plants grow faster.


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