Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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. Tuesday, 23 May 2017 G Davidson Slide 2 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. Tuesday, 23 May 2017 G Davidson Slide 3 Variety of Protein • Proteins form many different parts of an organism and have many functions. • e.g. -enzymes, antibodies, structural, hormones, etc. Tuesday, 23 May 2017 G Davidson Slide 4 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. Tuesday, 23 May 2017 G Davidson Slide 5 Structure of DNA Tuesday, 23 May 2017 G Davidson Slide 6 Structure of DNA Phosphate Deoxyribose sugar Tuesday, 23 May 2017 G Davidson Slide 7 Structure of DNA • The DNA molecule can be described as a double helix. • It is made up of two strands of subunits called nucleotides. • Each nucleotide has 3 parts: – deoxyribose sugar – a base – phosphate Tuesday, 23 May 2017 G Davidson P Ribose sugar Base Slide 8 Structure of DNA • There are four different nucleotides, because there are four different bases. • The four bases are: – – – – Cytosine Guanine Adenine Thymine P Ribose Cytosine P Ribose Guanine P Ribose Adenine P Ribose Tuesday, 23 May 2017 G Davidson Thymine Slide 9 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 by weak hydrogen bonds connecting cytosine to guanine and adenine to thymine. Tuesday, 23 May 2017 G Davidson Slide 10 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: 1. 2. 3. 4. a supply of nucleotides (4 types) ATP a DNA molecule to copy appropriate enzymes Tuesday, 23 May 2017 G Davidson Slide 11 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. Tuesday, 23 May 2017 G Davidson Slide 12 DNA Replication Tuesday, 23 May 2017 G Davidson Slide 13 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. Tuesday, 23 May 2017 G Davidson Slide 14 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. Tuesday, 23 May 2017 G Davidson Slide 15 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 Tuesday, 23 May 2017 G Davidson Slide 16 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 Tuesday, 23 May 2017 G Davidson Slide 17 Transcription • There are two types of RNA 1. messenger RNA 2. transfer RNA (mRNA) (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. Tuesday, 23 May 2017 G Davidson Slide 18 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. Tuesday, 23 May 2017 G Davidson Slide 19 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. Tuesday, 23 May 2017 G Davidson Slide 20 Protein Synthesis Tuesday, 23 May 2017 G Davidson Slide 21 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. Tuesday, 23 May 2017 G Davidson Slide 22 Protein Secretion Tuesday, 23 May 2017 G Davidson Slide 23