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Biology Paper 1: B3
Biology Paper 1: B3
DNA, proteins and mutations
Proteins are coded for by DNA. The base sequence codes for the order of amino acids, each amino acid is coded for by three bases
Mutations may lead to the production of different proteins This is because a change in bases in DNA can change the amino acid sequence
Proteins:- are made of long chains of amino acids, can be structural, hormones, carrier molecules or ensymes
Chromosomes are long, coiled molecules of DNA, divided up into regions called genes
The code needed to produce a protein is carried from the DNA to the ribosomes by a molecule called mRNA
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Enzyme activity is affected by pH and temperature. This is due to:- lower collision rates at lower temperatures, denaturing at extremes of pH and high temperatures
Cell division and growth
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Growth can be measured by a change in wet mass, dry mass or length. Each method has advantages and disadvantages but dry mass is the best measure
In meiosis, the chromosome number is halved and each cell is genetically different.
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Undifferentiated cells called stem cells can develp into different cells, tissues and organs
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Being multicellular allows organisms to :- be larger, use cell differentiation, be more complex
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