Biology

Mitosis is the process of new genetically identical cells being produced. The stges of the procces are;

Interphase - Its occurs before mitosis. During this the DNA makes an identical copy of itself then coils up into double-armed chromosomes (x shaped).

Prophase - The nucleus starts to break down and the spindle fibres appear.

Metaphase - Chromosomes line up at the centre of the cell. Cell fibres called the spindle attach to the middle of each chromosome.

Anaphase - Each copy of the chromosomes is then pulled apart to opposite pole of the cell on the spindle fibres.

Telophase - A membrane forms around each set of chromosomes to form the nuclei. The cytoplasm begins to divide.

 Cytokinesis - The cytoplasm has completely divided and there are now two genetcially identical cells.

Ciliated cells - Found in the nose and throat, have tiny hair like structures which moves bacteria and mucus away from the lungs. 

Muscle cells - Founs in the muscles in the body, contain special contractile proteins that can shorten the cell, conatins many mitochondria to provide every for contraction.

Sperm cells - The male sex cell found in the testes, they have tails and are streamlined to swi towards the egg cell.

Nerve cells - Carry electrical pulses around the body, found in the nerous system, they are very long to carry these messages quickly all around the body.

Red blood cells - Carry oxygen all around the body, they hae a biconcave shape which gives them a large surface area for more oxygen to pass into them. There is no nucleus so there's more room for red hamoglobin, the more haemoglobin the more oxygen.

Egg cells - Found in the ovaries, the female sex cell, large and cpntain a lot of cytoplasm, they contain food stores for the developing embryo

Root hair cells - Found behind the root tip, collect the water and minerals that soil contains, they have a large surface area for absorbing nutrients.

Palisade cells - Found in the upper part of all leaves, enable photosynthesis to be carried out efficiently, their cylindrical shape allows maximum absorbtion of light by chloroplasts.

Xylem - Found in any oragan were the plant needs mechanical strength but mainly in the stem, they transport water and nutrients from the plant soil to the stem and leaves, it has a thick wall made of lignin which supports the plant.

Meristem - Found in zones of the plant where growth can take place, they are physically responsible for the growth of the plant and they are undifferentiated.

Curing diseases: Embroyonic stem cells                                                                                              They can make new insuli producing cella for diabetics. They can make new nerve cells for people who ae paralysed from spinal injuries. They can be used to make new muscle cells for people who has muscular and movement problems.

Curinng diseases: Adult stem cells                                                                                                      They can be transferred from the one marrow of a healthy person to a patiant who has a disease.

Therapeutic cloning                                                                                                                               An embryo is produced in a lab which has the same genes as the patiant.

The central nervous system is made up of the brain, spinal cord and the nerves. The CNS is responsible for co-ordinating information for sensory organs to bring about a response.

Receptor cells - Decet the change in surrounding meaning the body can give a response.

A simulus - A change in a surrounding.

A response - Something moving or reacting.

Effector - A muscle or gland in the body that carried out the response.

Sensory neurons - Carry impulses from the receptor cells to the CNS, they have long dendrite which allow fast neurotransmission.

Motor neurones - Carry impulses to effectors, they have n dendrons.

Relay neurones - They link the motor and sensory neurons and also make up a lot of the nerve tissue in the brain, they are very short and have no dendrons.

In the gamete mother cell each chromosome replicates, each chromsosome has two genetically identical chromatides attached to their centromere. This means there are four chromosomes in the nucleus.

The chromosomes align in homolgous pairs, the points of contact or crossing over between the members of a homolgous pair are calles the chiasmata.

The homolgous pairs move to the equator of the cell. The cell membrane is starting to pnch inwards,

The cell divides to form two cells, each with a haploid set of chromosomes.

The chromatids in each cell are separated. The chromatids are pulled towards the opposite poles of the cell.

The cells divide are their are four cells each with the same haploid number.