GCSE Biology AQA

Platelets are small fragments of cells. They help the blood to clot at a wound, preventing excessive bleeding and bruising.

Red blood cells carry oxygen from the lungs to all the cells in the body. They have a concave shape which means that they have a large surface area for absorbing oxygen. Red blood cells do not have a nucleus however they do contain haemoglobin. In the lungs, haemoglobin combines with oxygen to form oxyhaemoglobin. In body tissues, the reverse happens - oxyhaemoglobin splits up into haemoglobin and oxygen.

White blood cells are part of the immune system. They help to protect the body from infectious diseases by a) engulfing pathogens and digesting them b) producing antibodies which bind to antigens on the surface of pathogens and destroy them c) producing antitoxins which counteract poisons produced by invading bacteria

Follicle-Stimulating Hormone (FSH) is produced in the ovaries.

IVF ( in vitro fertilisation ) involves collecting eggs from a woman's ovaries and fertilising them in a lab using a man's sperm. They are then grown into embryos which are transferred to the woman's uterus. A disadvantage of IVF is that there is a risk of multiple births if more than one embryo grows into a baby, which can result in a higher risk of miscarriage.

Biomass is the mass of living material

Lichen are air pollution indicators which are very sensitive to the concentration of sulphur dioxide in the atmosphere. The number of lichen in a particular location will indicate how clean the air is.

Sexual reproduction involves one parent.

Asexual reproduction produces genetically identical offspring (clones of their parent).

Cystic Fibrosis and Polydactyly are genetic disorders which are both caused by a dominant allele.

Humans have 23 pairs of chromosomes in every body cell.

Enzymes are biological catalysts which speed up the rate of reactions.

Amylase converts starch into amino acids.