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Published byHelena Cameron Modified over 8 years ago
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Proteins
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Are the enzymes that catalyse all biochemical reactions in the body. Are the structure of the body Carry oxygen Fight disease Make up cell membranes Are chemical messengers
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Structure of proteins Are polymers (note: often confusion over peptides, proteins and polypeptides = all are amino acid chains, difference is length.) Units are amino acids (made up from 64 nucleotide combinations)
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20 different amino acids therefore some amino acids are specified by more than one codon. This is called degeneracy. This buffers against mutations as a single base change may not result in an affect Are joined together by condensation Some hydrophilic and some hydrophobic allowing proteins fold into specific shapes.
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Fibrous proteins and globular proteins (long and stringy or round and ball like). AUG is always the start signal Stop signals always come at the end – UAA,UGA,UAG Read amino acid tables for mRNA code: read left hand side, top and then right side.
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So remember: DNA: ATG CTG AGG GGT TAT TAA TAC GAC TCC CCA ATA ATT mRNA: AUG CUG AGG GGU UAU UAA Don’t forget – U not T in RNA, read amino acid code from mRNA.
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Protein structure and Function There are four levels of protein structure. The final shape of the protein determines its function. For enzymes, the shape is crucial for correct function.
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Primary structure = order of amino acids Secondary structure = how tight the coil or chain is Tertiary structure = how the chains loop back on themselves again and again. Quaternary structure = how separate protein molecules join to each other.
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