Monday 14 April 2014

GCSE biology unit 1 - the nervous system

The nervous system

Its job is to detect stimuli so we can coordinate our behaviour. Stimuli are changes in the environment.
Receptors sense these changes:

  • eyes contain light receptors that detect light
  • noses contain chemical receptors that detect smells
  • mouths contain chemical receptors that detect tastes
  • skin has various receptors that are sensitive to touch, temperature, pressure and pain
  • ears contain sound receptors and also receptors that detect position (balance)
once the receptor has detected the stimulus, the sensory neurone passes an electrical impulse to the central nervous system (brain + spinal chord), where relay neurones pass the signals from one nerve cell to another. The CNS then passes an impulse through the motor neurone to the effectors  and a response happens.

e.g. sound stimulus - sound receptors - sensory neurone - CNS - motor neurone - effector - response.

The CNS contains synapses which are junctions between the three neurones. that pass the electrical impulses through gaps by using chemical signals.

Reflexes miss out the CNS and go straight through the three neurones. This way they are quicker so protect you. If the brain was involved, there would be a delay.

GCSE biology unit 1 - growing microbes

Growing Microbes

Also referred to as "culturing" microbes. We grow microbes to investigate what medicines can kill it. we do this under ASEPTIC CONDITIONS (make sure nothing gets contaminated that might effect the results)

STEP 1: sterilise the agar jelly inside the Petri dish
STEP 2: transfer microbes to the agar jelly using a inoculating hoop and place in neat, straight lines. The inoculating hoop should be heated first to kill any bacteria then left to cool before transferring the microbes.
STEP 3: quickly place lid on Petri dish and seal the container with tape to prevent any further contamination.
STEP 4: incubate at 25 degrees if in a school or 37 degrees if in a safe lab with scientists incase a pathogen is grown at the higher temperatures.

testing for disinfectants or antibiotics

use the microbes grown and place different sorts of disinfectants or antibiotics on the patch of microbes. once the microbes die, the agar jelly turns clear so the most effective disinfectant of antibiotic will have the largest clear area.

GCSE biology unit 1 - antibiotic resistance

Antibiotic Resistance

Medicines and Antibiotics

Pathogens infect the body and, after a while, cause symptoms. people's options are to wait for the white blood cells kick in or they can take medicines (pain killers) to relieve the symptoms. Medicines such as painkillers only relieve the symptoms - they don't effect the pathogens.

Antibiotics are medicines that relieve symptoms, have an effect on bacteria and can actually kill pathogens. These are good but...

If a doctor prescribes too many and too often the bacteria get a lot of exposure to the antibiotics and a mutation occurs (a random, spontaneous change in tis DNA) that causes the bacteria to become antibiotic resistant. This mutation is caused by natural selection. as this new bacteria multiplies, the person ends up with a population of antibiotic resistant bacteria.

scientists are developing new antibiotics that will actually kill that bacteria as opposed to just having an effect on them. These, again should not be prescribed too much.

Saturday 12 April 2014

GCSE biology unit 1 - vaccinations

vaccinations

protecting against future diseases
  • vaccines contain dead pathogens that still have antigens (codes or shapes on the cell wall)
  • the white blood cells will produce antibodies to attack the antigens
  • in the future, if these pathogens enter the body, the white blood cells will be able to produce antibodies quicker as it will recognise the antigens
The more people that are vaccinated, the harder it is for the disease to spread as there are fewer people who can catch it.

MMR
  • measles, mumps and rubella
  • linked to autism (condition that effects people's communication and social interaction skills)
Ignas Semmelweis (1850s) noticed that there were fewer cases child bed fever (a common birth disease) in the wards where only the midwives worked and the were more cases of child bed fever in the wards where the medical students dealt with child birth. 
He noted that the medical students were also working on dead bodies whereas the midwifes only dealt with child birth. He also noted that the medical students didn't wash their hands after carrying out investigations on dead bodies.

He recorded results and there were indeed many more cases of the disease on the medical student wards. Semmelweis predicted that something from the dead bodies was passing on causing child bed fever. He asked the medical students to wash their hands and the number of deaths reduced but his ideas were rejected because he could not explain what was passing on. Nowadays we know this is bacteria and it is normal procedure for doctor and nurses to wash their hands continually.



Wednesday 9 April 2014

GCSE CHEMISTRY - unit 1 - compounds and bonding

REACTIONS AND COMPOUNDS

New substances are formed by chemical reactions. When elements react together to form compounds their atoms join to other atoms using chemical bonds.

Ionic bonds

Compounds formed from metals and non-metals consist of ions. Ions are charged particles that form when atoms (or clusters of atoms) lose or gain electrons:
  • metal atoms lose electrons to form positively charged ion
  • non-metal atoms gain electrons to form negatively charged ions
The ionic bond is the force of attraction between the oppositely charged ions. 

Covalent bonds

Two non-metals share an electron to form covalent bonds that hold the atoms together to form molecules.

Chemical formulas

The chemical formula of a compound shows how many of each type of atom join together to make the units which make up the compound. For example, in iron sulfide every iron atom is joined to one sulfur atom, so we show its formula asFeS. In sodium oxide, there are two sodium atoms for every oxygen atom, so we show its formula as Na2O. Notice that the 2 is written as a subscript, so Na2O would be wrong.


GCSE biology unit 1 - infectious diseases

Infectious diseases

Microorganisms
  • E.g bacteria, viruses, fungi
  • Not all cause diseases
  • Ones that cause diseases are called pathogens 
Pathogens
Microorganisms that cause disease

Bacteria
Produce toxins (poisons)

Viruses
Much smaller
Infect body cells by getting inside and reproducing so many times that the cell explodes/breaks so is permanently damaged

DEFENCE - white blood cells
They ingest bacteria and release enzymes to digest pathogens
They produce antibodies to latch onto the antigens (small shapes on cell walls) of the pathogen and start destroying them. Different diseases have different antigens.
They produce antitoxins which neutralise bacteria toxins, making them harmless.

GCSE biology unit 1 - balanced diets

Balanced diet

Proteins
  • Meat, fish, eggs, pulse veg. Etc.
  • Build new tissue (important if still growing)
  • Repairs damaged tissues
  • Made up of amino acids
Carbohydrates
  • Potatoes, breat, rice, sugars, etc.
  • Provide energy
  • Can lead to obesity if not balanced with exercise 
Fats
  • Butter, oil, etc.
  • Provides stored energy to be used later when needed
  • Can lead to obesity if not balanced with exersise
Fibre
  • Veg, fruit, etc.
  • Not absorbed by body/ blood so not a nutrient
  • Helps prevent constipation
Vitamins and minerals
  • For general health
  • Can't get energy from them
  • A lack of them leads to deficiency disease
If you take in more energy compared with what you release, you will put on weight.

MALNUTRITION is caused by a non-balanced diet.
You can either be underweight or overweight.

Metabolism
Total of the chemical reactions that are going on in your body

Affected by
  • Amount of exersise you do
  • Genetics
  • Muscle to fat ratio (muscle requires energy)
  • Gender (females tend to have lower)
Cholesterol 
Required in the body to make cell membranes
Too much can lead to blocked arteries (especially around the heart), restricting the blood flow
This can lead to a heart attack.

Type 2 diabetes
Linked to being overweight
Means you cannot control blood sugar levels
Insulin is not recognised by body cells so cells don't take sugar out of the blood.


GCSE chemistry unit 1 - fractional distilation of air

Fractional distillation of the air

Today the air is a mixture of:
  • 78% nitrogen
  • 21% oxygen
  • And 1% other gases (including 0.04% carbon dioxide and 0.8% argon - a noble gas)
Fractional distillation

The air is cooled to -200 degrees so all the gases in the air are condensed into a liquid. Carbon dioxide and water are then removed so we are left with the other gases including nitrogen, argon and oxygen, which all have different boiling points. Heating it to a hoc her temperature each time, nitrogen evaporates first, then argon, then oxygen which can be collected as three different substances.

Uses of argon
  • Unreactive so used inside filament bulb and fluorescent tubes
  • Preserving old document because they are so unreactive.
Uses of nitrogen
  • Food packaging to stop food decomposing (unreactive)
  • In liquid form it can preserve living cells
  • Fertilisers
Uses of oxygen
  • Part of fuels for rockets
  • Oxygen masks etc.

GCES chemistry unit 1 - Miller-Urey experiment

Miller-Urey experiment

Miller and Urey were two scientists who set up apparatus that recreated the conditions that were in the atmosphere 4.5 billion years ago to try and work out how organisms could have been created. 

Water was heated to create water vapour which travelled to a flask containing ammonia, hydrogen and methane. They used a series of different electric shocks on the flask and then condensed the gasses. Within a week, they found they had produced the organic chemicals needed for life such as amino acids. But how these organic chemicals turned into life, still remains unanswered, they won a Nobel Prize for their discoveries.

GCES chemistry unit 1 - the development of the Earth's atmosphere

The development of the Earth's atmosphere

Volcanic eruptions 4.5 billion years ago gave off carbon dioxide, water vapour, ammonia and methane. The earth was continually cooling so, over time, the water vapour condensed into water and created the oceans . The ocean then gradually removed some of the CO2 in the air by absorbing it.

3.5 billion years ago, the first signs of life occurred somehow and they could carry out photosynthesis which removed CO2 from the air and replaced it with oxygen. Oxygen levels continued to rise and Co2 levels fell.

More complex organisms evolved and CO2 from the ocean became CO3 (carbonate) in the shells and skeletons of these animals. These shells and skeletons, along with plant waste, all contained CO2 and over millions of years formed sedimentary rocks containing locked away carbon - a carbon sink. These are the fossil fuels we use today but they are running out.

GCSE chemistry unit 1 - plate tectonics

Plate tectonics

The Earth's structure
  • The atmosphere - 10km thick (mostly)
  • The crust - 5-70km thick)
  • The mantle - 3500km thick 
  • The core (inner and outer) - 3500km thick
Plate tectonics

1915, Alfred Wegener proposed continental drift. He noted that continents fit together like a jigsaw and found that, where they supposedly met, the rocks and fossils are identical. He could not explain, however, how this happened so his proposal was rejected.

Nowadays we accept the theory because we have found that the plates moved, and continue to move, due to radioactive processes in the core that produce heat which leads to convection currents in the mantle. The convection currents move the plates by about a centimetre a year.

Volcanoes can form where the plates move away from each other or one subsides (goes under the other).
Mountains are formed when plates move towards each other and buckle upwards.
Earthquakes occur when plates slide past each other.

It is difficult to predict exactly when earthquakes and volcanic eruptions will occur.

GCSE chemistry unit 1 - plant oils

Plant oils

Oils from plants are useful:
  • They contain nutrients and energy
  • Give a much higher energy content to food
  • Give different flavours to food
  • Are used in cosmetics
  • Can be used in biofuels (more renewable fuels)
They can be made in two ways:
  • STEAM DISTILLATION
  • OR PULPING THE FRUIT

Steam distillation



















As the plant material and water is heated, the plant oils and steam is evaporated but then condenses when it reaches the cooling jacket. The products are two separate liquids: water and plant oil. It is simple to separate them because they are not mixed.


Pulping the fruit

Plant or fruit is crushed to a pulp and then squeezed. The squeezed oils are purified, removing water and impurities and is now pure oil. The pulp or seed left over are dissolved in a solvent to create oil. The solvent and oil are then separated to create even more pure oil. There is little waste.

GCES chemistry unit 1 - saturated and unsaturated fats/oils

Saturated and unsaturated fats(solid) and oils(liquid)

Saturated
  • Solid at room temperature
  • Higher melting point
  • Come from animals (e.g butter)
  • Less healthy (build up cholesterol)
  • NEVER HAS A DOUBLE BOND
  • E.g alkane
Unsaturated
  • Liquids at room temperature
  • Lower melting point (due to double bond)
  • From plants (e.g olive oil)
  • More healthy
  • ALWAYS HAS ONE OR MORE DOUBLE BONDS
  • E.g alkene
Test for unsaturated fats
In bromine water, an unsaturated fat will turn the bromine water colourless and if it's a saturated fat, the solution will stay browny, orange.

Turning an unsaturated fat into an almost saturated fat

React the unsaturated fat (containing hydrocarbon chains) with hydrogen at 60 degrees. The double bonds break as the hydrogens join the hydrocarbons. 
Add a nickel catalyst to speed up the reaction.
It creates an almost saturated molecule
DOSEN'T GET RID OF ALL THE DOUBLE BONDS BUT MOST OF THEM (it's still healthier than fully saturated)

This almost saturated product can be turned into low fat butters as they now have a higher boiling point so are solid at room temperature. They are also great for making cakes. They are a healthier than fully-saturated products.

GCSE chemistry unit 1 - emulsions

Emulsions

An emulsifier helps water and oil mix by suspending oil droplets throughout the water. They create EMULSIONS.

Emulsions are:
  • More viscous (thicker)
  • Better at coating things
  • Have a better texture
  • Because of this, emulsifiers are added to make products such as paint, mayonnaise, salad dressing, ice cream, milk and cosmetics.
  • Egg yolk is an example of a good emulsifier
Molecules of an emulsifier look like this:


The hydroPHOBIC tail repels water (just remember phobia means you're scared of something).

The hydroPHILIC head is attracted to water.

So when added to a substance contains oil and water the molecules surround the oil droplets, the tails in the oil droplet, repelling the water and the heads in the water.

This suspends the oil droplets throughout the water so they appear to be mixed, like below:




GCSE chemistry unit 1 - ETHANOL (alcohol)

Ethanol

Uses
  • Used in alcoholic drinks
  • Disinfectants (kills microbes)
  • Perfumes
  • Fuels (because it as originally part of a cracked hydrocarbon that came from crude oil)
Can be made in 2 ways:
  1. FERMENTATION
  2. REACTING ETHENE (alkene) WITH STEAM (water)

Fermentation

Sugar (glucose), yeast (microorganism) are placed in a container and water is added to help them mix easily. The yeast converts the glucose into ethanol, shown in the equation below:

GLUCOSE --------- ETHANOL + CARBON DIOXIDE

(the CO2 comes from the yeast respiring)

This can be carried out on a huge scale and the ethanol can then be purified.

Hydration (reacting ethene with water)

ETHENE + WATER (in the form of steam) ------(300 degrees)------- MAKES JUST ETHANOL

The hot temperature is a catalyst and speeds up the reaction.

Comparison

Fermentation
  • Much cheaper
  • Happens at low temperatures (no cost of heating)
  • Produces carbon dioxide which adds to the greenhouse effect
  • Lots of land is needed to grow crops that produce glucose (land that could be used for something else)
Hydration
  • No carbon dioxide produced
  • Quicker
  • Less people needed to complete the process
  • Expensive - equipment, high temperatures + energy used
  • Uses ethene (part of crude oil) which is running out ( non-renewable)