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Synthesis and Release of Protein

Synthesis and Release of Protein. Mr G Davidson. Variety of Protein. Proteins are important molecules in biology. They contain the elements Carbon, Hydrogen, Oxygen and Nitrogen. They often contain Sulphur and Phosphorous. . Variety of Protein.

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Synthesis and Release of Protein

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  1. Synthesis and Release of Protein Mr G Davidson

  2. Variety of Protein • Proteins are important molecules in biology. • They contain the elements Carbon, Hydrogen, Oxygen and Nitrogen. • They often contain Sulphur and Phosphorous. G Davidson

  3. Variety of Protein • Proteins are built from chains of amino acids, held together by peptide bonds forming polypeptides. • If the polypeptides form parallel strands, fibrous proteins are formed, and if they become tangled up to form a spherical shape, globular proteins are formed. G Davidson

  4. Variety of Protein • Proteins form many different parts of an organism and have many functions. • e.g. -enzymes, antibodies, structural, hormones, etc. G Davidson

  5. Structure of DNA • Cell proteins are built according to inherited information held in the nucleus, the information is packaged as chromosomes. • The chromosomes are made up of chains of molecules, called genes. • A gene is a unit of heredity and is composed of a complex substance called Deoxyribonucleic acid. G Davidson

  6. Structure of DNA G Davidson

  7. Phosphate Deoxyribose sugar Structure of DNA G Davidson

  8. P Base Ribose sugar Structure of DNA • The DNA molecule can be described as a double helix. • It is made up of two strands of sub-units called nucleotides. • Each nucleotide has 3 parts: • deoxyribose sugar • a base • phosphate  G Davidson

  9. P Cytosine Ribose P P P Guanine Adenine Thymine Ribose Ribose Ribose Structure of DNA • There are four different nucleotides, because there are four different bases. • The four bases are: • Cytosine • Guanine • Adenine • Thymine G Davidson

  10. Structure of DNA • The molecule is held together in two different ways. • A strand is connected by strong bonds between the sugar and phosphate. • The strands are held together byweak hydrogen bonds connecting cytosine to guanine and adenine to thymine. G Davidson

  11. DNA Replication • During cell division, the genes must be able to replicate in order that each new cell gets a full chromosome compliment. • In order for replication to occur, the following must be present in the nucleus of the cell: • a supply of nucleotides (4 types) • ATP • a DNA molecule to copy • appropriate enzymes G Davidson

  12. DNA Replication • Replication begins with the uncoiling of the DNA helix. • Once this has happened, the weak hydrogen bonds joining the two strands break, causing the DNA molecule to ‘unzip’. • Once the bases are exposed, free nucleotides find their complimentary bases, forming two new DNA molecules, identical to the original molecule. G Davidson

  13. DNA Replication G Davidson

  14. Protein Synthesis • The sequence of bases along a strand of DNA is anything but random. • The order of bases is called the genetic code. • The code is actually a ‘recipe’ for protein production. G Davidson

  15. Protein Synthesis • Proteins are chains of amino acids of which there are twenty in nature , so it follows that the DNA code should be able to specify at least 20 different items. • To do this, the bases of DNA are grouped in threes, these are called triplets of bases, each containing a triplet code for a specific amino acid. G Davidson

  16. Protein Synthesis • DNA occurs in the nucleus of a cell, and protein synthesis on the ribosomes in the cytoplasm, therefore something must happen which transfers information from one place to another. • Protein synthesis occurs in two stages: -transcription -translation G Davidson

  17. Transcription • The information contained in the DNA code has to be collected and taken out of the nucleus and this is done by another nucleic acid called Ribonucleic Acid (RNA). • It is similar to DNA except: 1. it is a single strand 2. it has a ribose rather than a deoxyribose sugar 3. the base Thymine is changed to the base Uracil G Davidson

  18. Transcription • There are two types of RNA 1. messenger RNA (mRNA) 2. transfer RNA (tRNA) • During protein synthesis, the appropriate region of DNA temporarily opens up to expose the bases to produce a strand of mRNA which then leaves the nucleus through the pores. • The mRNA template is made of triplet bases called codons. G Davidson

  19. Translation • Once the mRNA leaves the nucleus, it becomes attached to a ribosome. • In the cytoplasm, there are still tRNA molecules containing only 3 bases called an anticodon, which corresponds to a specific amino acid. G Davidson

  20. Translation • The codons of the mRNA pair up with the anticodons of the tRNA which is carrying an amino acid. • The amino acids are then joined together by peptide bonds to form proteins. G Davidson

  21. Protein Synthesis G Davidson

  22. Protein Secretion • Many of the enzymes and other proteins made by the cell will have to be secreted by the cell since they may be used in remote parts of the organism. • These proteins are processed by the Golgi body where carbohydrates are added to form glycoproteins. • These are then pinched off to produce vesicles which are then transported to the plasma membrane where they are secreted. G Davidson

  23. Protein Secretion G Davidson

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