1 / 18

Cell structure

Cell structure. Nucleoid. Single strand of DNA, usually circular, usually looks like a big ball of messed up twine… Size – smallest organism yet discovered (Nanoarchaeum equitans) 490,889 base pairs; e. coli 4.7 Mbp, most prokaryotes 1-6 million base pairs (1-6 MBp); Humans 3300 MBp

kert
Download Presentation

Cell structure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Cell structure

  2. Nucleoid • Single strand of DNA, usually circular, usually looks like a big ball of messed up twine… • Size – smallest organism yet discovered (Nanoarchaeum equitans) 490,889 base pairs; e. coli 4.7 Mbp, most prokaryotes 1-6 million base pairs (1-6 MBp); Humans 3300 MBp • DNA is around 1000 mm long in bacteria, while the organism is on the order of 1 mm long – special enzymes called gyrases help coil it into a compact form

  3. Construction, Part 3 • Bases – Two types: Pyrimidine Purine • Derivatives Cytosine, C Uracil, U Thymine, T Adenine, A Guanine, G DNA  C,T,A,G No U RNA  C,U,A,G No T

  4. dNTP’s • Deoxyribonucleotide triphohosphate • ATP (the energy-generating molecule) is the same and the ‘A’ building block – also GTP, CTP, UTP, TTP • These react to chain lengthen and form RNA or DNA – lose 2 of the PO4 groups in the process

  5. DNA is double-stranded (double helix), while RNA is single stranded • RNA has a slightly different sugar backbone – ribose instead of deoxyribose • RNA has a lot of turns and kinks, more chaotic structure, but some sections are closer to the outside than others… RNA DNA

  6. Palindromes and DNA • DNA’s structure is inherently directional • dNTP’s have bonds on opposite ends that attach  3’ (OH) and a 5’ (PO4) • Direction of the ‘code’ 3’  5’

  7. DNA enzymes • Restriction endonuclease – cuts DNA at specific base combinations • DNA ligase – links DNA molecules • DNA polymerase I – attaches DNTP’s, repairs DNA • DNA polymerase II – attaches DNTP’s, proofreads • DNA gyrase – twists, coils DNA • DNA Helicase – DNA strand separation • DNAse - degrades DNA to DNTP’s

  8. Data copying inside a cell • Polymerases – proteins that catalyze different components of DNA, RNA replication • DNA replication – occurs by unwinding, copying each strand, and putting 2 identical pairs together • Transcription – formation of RNA from DNA • Translation – formation of proteins from RNA information

  9. Transcription RNA polymeraze takes the DNA and temporarily unwinds it, templates the transfer RNA from that, using ribonucleoside triphosphates to assemble…

  10. Ribosome • The ribosome is the site of translation of messenger RNA into protein. It is composed of two subunits. • In prokaryotes, the large subunit is called 50S and the small subunit is called 30S. The 30S subunit consists of a single strand of RNA (the 16S rRNA, 1542 bases), and 21 proteins ranging in molecular weight from 9 kD to 61 kD. • The 30S subunit is the site of translation initiation. • Measured by a ‘sedimentation coefficient’ – 16S rDNA is associated with a 16S sized small subunit of the RNA translating ribosome

  11. RNA and protein construction • The nucleotide base sequence of mRNA is encoded from DNA and transmits sequences of bases used to determine the amino acid sequence of the protein. • mRNA (“Messenger RNA”) associates with the ribosome (mRNA and protein portion). • RNA (“Transfer RNA”) also required • Codons are 3 base mRNA segments that specify a certain amino acid. • Most amino acids are coded for by more than one codon. • Translation ends when ribosome reached “stop codon” on mRNA.

  12. Ribosomal RNA • Ribosomal RNA is single stranded • RNA is a single stranded nucleic acid • mRNA- messanger RNA – copies information from DNA and carries it to the ribosomes • tRNA – transfer RNA – transfers specific amino acids to the ribosomes • rRNA – ribosomal RNA – with proteins, assembles ribosomal subunits DNA is transcribed to produce mRNA mRNA then translated into proteins.

  13. Codons • 64 combinations of bases – 61 of these code for amino acids, 3 of them signal the end or start of the chain Anticodons – the opposite sequence (G-C U-A) on the transfer RNA

  14. Translation • mRNA is coded for one or more specific amino acids and moves to the ribosome to assemble amino acids into proteins • On mRNA, codons are 3 bases, coded to specific amino acids • On tRNA, the anticodon latches to the codon on the mRNA

  15. Translation = Protein Formation • The ‘code’ on mRNA determines the sequence of protein assembly • Codon-anticodon?

More Related