b2 notes

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  • Created on: 31-05-13 10:45
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B2 biology notes
Plant and animal cells
Cell membrane- this separates the contents of the cell from its
surroundings the cell membrane is vital in allowing gas exchange- gases
like oxygen in and carbon dioxide out.
Cytoplasm- is a substance in which many chemical reactions vital for
processes to happen take place, the cytoplasm contains organelles
which are small structures that have specific jobs.
Nucleus- this is an organelle which contains DNA which is genetic material. The nucleus controls the
activities of the cell.
Mitochondria- this is an organelle in which respiration takes place- the mitochondria are very small
and cannot be seen through a light microscope with low magnification.
Cell wall- a cell wall is only present in plant cells rather than animal cells, the cell walls holds the cell in
place and keeps t in its shape as well as it is made of tough cellulose that can support the cell.
Vacuole- a vacuole is a space in the cytoplasm in which contains cell sap which helps to keep the cell
Chloroplasts- organelles in which contain chlorophyll a substance used in the process of
photosynthesis in order to absorb the light energy, the chlorophyll gives the plant its green colour.
Modern light microscopes can magnify images up to
1500 times. Electron microscopes invented in the
1930's can magnify images up to 2 million times in
which if you look at bacteria. The microscope shows
that bacteria have two types of DNA, chromosomal
DNA a giant loop of DNA containing most of the
genetic material; however there is also plasmid DNA
which comes in small loops carrying extra
Information. The cell wall in a bacteria cell is not
made out of cellulose and is more flexible, the flagellum helps the bacteria to move around.
Bacteria cell-

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The chromosomes in the nuclei of your cells contain genetic information; they are made up of a
chemical called DNA deoxyribonucleic acid. Sections of DNA are called genes and they contain
instructions for specific proteins used in your body. One gene contains the instructions for one
protein often several genes work together to produce what is needed for one feature, for example
your eye colour. Some genes contain instructions for proteins that control chemical processes in
your body.…read more

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The benefits of this project were;
Improved testing for genetic disorders to see if people were carrying a faulty allele
New ways of finding genes that may increase the risk of certain diseases, Alzheimer's heart
New treatments and cures, gene therapy where scientists try and mend faulty genes.
New ways of looking at the genome to see how humans have evolved and how our genes
have changed.…read more

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Mitosis is the process in which a human cell which contains two copies of a chromosome hence is a
diploid cell- two sets of 23 chromosomes, body cells
are diploid cells except for sex cells. In order to make
more cells for growth or repair the cells need to divide
they do this by the process of mitosis the
chromosomes make copies of them- DNA replication.…read more

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Meiosis is the type of cell division needed to produce haploid cells/ gametes, this starts with DNA
replication but then two types of cell division. In the first type of cell division the two sets of
chromosomes are separated. In the second cell division the copies of these chromosomes are
separated this produces four haploid cells each containing one set of chromosomes.…read more

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Organisms that reproduce slowly can It will also lead to less variation in the
be made quickly, and plants that do not future.
produce seeds can also be made
If a certain organism has a desired If one clone is susceptable to disease
genetic characteristic it can be then all the clones will.
reproduced as a clone.
Stem cells
Stem cells are cells that can be made into differentiated cells.…read more

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A mutation can occur in a gene mutations can cause the genetic disease of sickle cell anaemia, as
well as causing misshapen nails. Mutations can alter the shape of enzymes and haemoglobin causing
cells to change shape as well, the protein for nails like keratin forms long fibrous molecules hence
our nails are hard. Mutation sin bacteria have made them antibiotic resistance which is a
disadvantage to us but an advantage to them.…read more


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