GCSE Biology Paper 1 Revision

cells differentiate to become specialised, which allows them to perform different tasks.

In Aminals this ability is lost at an early stage, plants don't ever lose it.

Sperm Cells are specialised for reproduction. Their function is to get male DNA to female DNA. They have lots of mitochondria and enzymes to digest through the egg. 

Nerve cells are specialised for rapid signaling. Cells are long to cover more distance and branch to form a network. 

Muscle cells are specialised for contraction. They are long and have lots of mitochondria. 

Root hair cells specialised for absorbing water and minerals. They have a large surface area for maximum absorbtion. 

Phloem and xylem are specialised for transporting substances. They form tubes around a plant. Xylem are hollow and phloem have few subcellular structures. 

contain genetic information. 

they are coiled up DNA molecules, each one carries genes that controls characteristics. 

Body cells have two copies of each each, one from the mother and one from the father. 

Diffusion is particles spreading out from areas of high concentration to low concentration. 

It happens in solutions and gasses

The bigger the concentration gradient, the faster the rate of diffusion. 

The higher the temperature, the faster the rate of diffusion. 

Dissolved substances move in and out of cell membranes through diffusion. 

The larger the usrface area, the faster the rate of diffusion. 

Only small particles diffuse. 

The movement of water molecules across a partially permeable membrane, from a region of higher concentration to a region of lower concentration

Active transport is used by root hair cells and the gut to move particles against a concentration gradient. It reuqires energy. 

Similar cells are grouped to form a tissue

Tissues are gorup to form an organ

Organs are grouped to form an organ system

Organ systems are gouped sto form an organism

Enzymes are catalysts produced by living things. They are large protiens folded into unique shapes. 

Every enzyme has a unique active site which fits onto the subtance involved. It only fits onto that specific substance. 

Changing the temperature changes the rate of enzyme action. At first it increases the rate of reaction, then if it gets to hot the bonds holding the enzyme together break, which changes the active site so the enzyme won;t fit anymore and the reaction won't happen. The enzyme is denatured. 

It if the pH is too high or too low that also interferes with the bonds holding the enzyme together. 

carbohydrases convert carbohydrates into simple sugars. Amalayse breaks down starch. It is made in the salivary glands, the pancreas, and the small intestine. 

Proteases convert protiens into amino acids.They are made in the stomach, pancreas, and small intestine. 

Lipases convert lipid into glycerol + fatty acids, and are made in the pancreas and small intestine. 

Bile neutralises stomach acids and emulsifies fat. Produced in liver and released in small intestine

Benedicts test is used to test for sugars:

1) prepare 5cm³ food sample and put in test tube. 

2) prepare 75℃ water bath

3) add 10 drops of benedicts solution, transfer to water bath for 5 min

4) if food sample contains reducing sugar it will turn from blue to green, yellow, or brick red depending on the amount of sugar. 

iodine can be used to test for starch:

1) make a 5cm³ food sample in a test tube

2) add a few drops of iodine. If it contains starch it will turn from brown to black. 

biuret test tests for protien:

1) make a 2cm³ food sample in a test tube

2) add 2cm³ of biuret solution and gently shake. 

3) if protien is present it will change from blue to purple, if there is no protien it will remain blue. 

Sudan III stain test tests for lipids:

1) make a 5cm³ food smpale in a test tube

2) add 3 drops of Sudan III and gently shake. 

3) if a sample contains lipids, miture will seperate into a red and cloudy layer, if no lipids are present no second layer will form. 

the heart walls are amde out of muscle

there are valves to prevent blood flowing backwards

there are four chambers, left atrium, right atrium, left ventricle, right ventricle.

1) blood flows into the atria from the vena cava (right side) and the pulmonary vein (left)

2) the atria contract pushing blood into the ventricles

3) the ventricles conract pushing blood into the pulmonary arterty (right) and the aorta (left)

4) the blood then flows to the organs (right side to the lungs, left side to the body), then back to the atria, and the process begins again. 

epidermal tissue: covers the whole plant

palisade mesophyll: where photosynthesis happens

spongy mesophyll: big air spaces to allow gasses to diffuse

xylem and phloem: transport water, mieral ions, and food

meristem tissue: found at growing tips and shoots, able to differentiate allowing them to grow. 

Fungal disease the causes purple or black spots to develop in the leaves of rose plants

The leaves tehn turn yellow and drop off.

This causes less photsynthesis, so stunted growth.

Spreads through water and the wind.

Can be killed by fungicides, or infected leaves can be stripped away. 

Caused by a protist.

The vector is mosquito's. Every time the mosquito feeds on another animal it infects it by inserting the protist in the blood vessels. 

Malaria causes repeating episodes of fever and can be fatal. 

Bacterial disease that causes food poisoning. 

Symptoms include fever, stomach cramps, vomiting, and diorrhoea. 

This is caused by toxins produced by the bacteria. 

Salmonella can be transnfered by eating contaminated food. 

Most UK poultry is vaccinated against salmonella. 

Urine of a pregnant woman contains HCG hormone. 

The area where the urine goes on a pregnancy stick has antibodies with blue beads attatched.

If the user is pregnant the hormone binds to teh antibodies on the blue beads, the urine moves up the stick carrying the blue beads, the beasd and the hormone bind to the antibodies on the stick so the blue beads get stuck turning it blue. 

If the user is not pregnant the blue beads continue to move up the stick, but the urin doesn't get stuck as there is nothing to bind to. 

Plants need mineral ions from the soil, if there isn't enough then they suffer deficieny symptoms. 

Nitrates are needed to make protiens and therefore for growth. 

Magnesium ions are needed for making chlorophyll, plants without enough magnesium suffer from chlorosis and have yellow leaves. 

Are identical antibodies. They are produced from lots of clones of a single blood cell, they will only target one specific protien. 

Lymphocytes Don't divide very easily so they are fused to a tumour cell to create a hybridoma. these cna be cloned to get lots of cells. They all produce the same antibodies, and can be collected and purifed. 

Can be used to treat diseases. Different cells in the body have different antigens on their surface. Monoclonal antibodies can be made that will bind to specific cells in the body. 

Cancer cells have antigens on their cell membranes that aren't found on normal body cells, called tumour markers. Monoclonal antibodies can be made that will bind to the tumout markers. They are given to the patient through a drip. The drug kills cancer cells, but doesn't kill normal body cells near the tumour. 

a virus that affects any species of plant.s 

It causes a mosaic pattern on leaves, leaves become discoloured. This means they can't carry out photosynthesis, so the virus affects growth. 

spread by sexual contact or exchanging bodily fluid. 

Initially causes flu like symptoms for a few weeks, then the person might not experience symptoms for a few years. During this time it can be controlled by antiretroivral drugs, which stop the virus replicating. 

It attacks immune cells, which damages the immune system leading to other infections and cancers. 

At this stage it is the late HIV infection, or AIDS. 

A viral disease spread by droplets of water from an infected persons sneeze or cough. 

Symptoms include a red skin rash, and a fever. 

Measles can be very serious, or even fatal, if there are complications. 

Most people are vaccinated when they are young. 

Sexually transmitted disease caused by a bacteria. 

Symptoms include pain when urinating, thick yellow or green discharge. 

USually treated with penicillin, but some bacteria have become resistant. 

To prevent the spread barrier methods of contraception should be used. 

Attacks pathogens. 

White blood cells fight against disease by:

1) consuming them - phagocyte engulfs and digests foreign cells (phagocytosis)

2) producing antibodies - B-lymphocytes produce antibodies that lock onto invading cells so that they can be found and destroyed by other white blood cells. Antibodies produced are specific to that antigen. Antibodies can be produced rapidly, the next time a person is infected with the same pathogen the white blood cells can defend easier

3) producing antitoxins - counteract toxins produced by the invading bacteria.