Biology: B3 - Additional Science OCR

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  • Created on: 17-12-12 20:03
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Cytoplasm: Where chemical reaction take place
Cell Membrane: Allows movement into and out of cell
Nucleus: Contains the genetic information and controls what the cell does
Mitochondria: Respiration takes place inside, supplying energy for the cell. Cells that need a
lot of energy (sperm cells, muscle cells and liver cells) have a lot of mitochondria
Ribosomes: In the cytoplasm and are the site of protein synthesis
Genetic Information
In the nucleus of every cell there are chromosomes which carry genetic information in the
form of genes.
A gene are chromosomes that carries information about and controls characteristic
The sequence of the bases (A,T,G,C) provide a genetic code that controls cell activity
Each gene has a different sequence of bases
The DNA molecules in a cell form a complete set of instructions for how the organism should
be constructed and how each cell should work
Nucleus of each cell contains a complete set of genetic instructions
The instructions are carried by genes on chromosomes
Chromosomes are long coiled molecules of DNA, divided up into regions called genes
Genes are made from a DNA
Human cells have 23 pairs
Gametes contain individual chromosomes and therefore have exactly half the number of
normal cells
Controls the production of proteins
Genetic code controls cell activity and some characteristics of the organism
DNA is made of two strands coiled around each other in a double helix
Each gene codes for a particular protein
Structure of DNA
Structure of DNA was first worked out by Watson and Crick
Made in the cytoplasm
Genes can't leave the nucleus so a copy of the gene is needed, which can leave the nucleus
The sequence of bases in a gene represents the order in which the cell should assemble
amino acids to make the protein
A group of three bases represents one amino acid in a protein chain
Each protein has different shape and function

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Code needed to produce a protein is carried from the DNA in the nucleus to the ribosomes in
the cytoplasm by a molecule called mRNA.
DNA controls cell function by controlling the production of proteins, some of which are
Proteins and Mutation
Made of long chains of amino acids
Functions include:
o Collagen
o Insulin
o Haemoglobin
o Enzymes
Each protein has its own number and sequence of amino acids.…read more

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These changes can be spontaneous but the rate can be increased by environmental factors
such as radiation or chemicals.…read more


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