- La figure ci-dessus montre les résultats d'une cinétique El normale et de l'enzyme mutée E2. E2 ne diffère d'EI que par la substitution d'un radical valyle par un autre acide aminé. 1-Commenter l'affinité d'E1 et E2 pour S 2- Une électrophorèse à PH 7 montre qu'E2 migre rapidement vers l'anode. Quels acides aminés ont pu remplacés la valine dans la séquence de l'enzyme mutée ? Exercice 2 Soit une enzyme à cinétique Michaelienne ; tracer sur un même schéma, l'allure générale des autres courbes V=f(S) a- En absence d'inhibiteur b- En présence d'un inhibiteur compétitif c- En présence d'un inhibiteur non compétitif d- Préciser clairement sur le schéma K_(M) et V_(m)
- __ CTAGTT base sequence on DNA forms a GAUCAA base sequence with mRNA. __ GAUCAA base sequence on the mRNA is enough to allow tRNA to deliver 3 amino acids. __ Mutations occur when the base sequences are copied from DNA incorrectly. __ Meiosis and mitosis are both involved with the process of cellular division. __ The end product of meiosis and mitosis is the same. __ Normal body cells usually have paired chromosome strands __ Diploid cells have only one half of the total genetic material. __ Sperm cells are haploid because they have no paired chromosome strands. __ Haploid cells are produced by mitosis. __ During interphase normal body cells duplicate their genetic material. __ During meiosis the cell divides twice and the chromosomes duplicate twice.
- 0. Answer true or false to the following. 1 __ Chromosomes contain information that is used to produce proteins. 2. __ Chromosomes are found in the nucleus 3. __ RNA is part of a chromosome 4 __ DNA has a different sugar (deoxyribose) in its structure than RNA 5. __ DNA is the biochemical molecule that makes up the chromosome. 6. __ DNA is found in ribosomes. 7. __ Messenger RNA is found in the mitochondria. 8. __ Proteins are assembled in the mitochondria. __ 9. __ Ribose is an example of a nucleotide. __ 10. __ An anticodon is made up of three nucleotides and is found on the tRNA 11. __ Uracil is a base pair found on DNA. 12. __ A molecule of adenine matches with a molecule of cytosine. 13. __ Transcription involves the copying of the DNA code with messenger RNA. 14. __ Translation occurs when DNA is changed into mRNA. 15. __ Each base on the mRNA strand gives the information for an amino acid. 16. __ There are only 20 different amino acids that combine to make a protein 17. __ During DNA replication new strands are added to a splitting molecule of DNA 18. __ The message for producing protein is found in the ribosomes. 19. __ Transfer RNA has a specific anticodon for a specific amino acid that it carries. 20. __ A nucleotide is made up of a base, a sugar, and a phosphate. 21. __ Cytosine is an example of a base found on either DNA or mRNA. 22. __ Thymine is an example of a base found on either DNA or mRNA 23. __ Uracil is a base found only in mRNA and binds to the adenine on the DNA strand. 24. __ When amino acids join they form peptide bonds and eventually proteins.
- Exercice 1 Répondre par vrai ou faux affirmations suivantes Justifier brievement votre réponse. La vitesse d'une réaction enzymatique : 1-Présente une relation linéaire en fonction des quantités croissantes d'enzyme. 2- Présente une relation hyperbolique en fonction des quantités croissantes d'enzyme 3- Est maximale à une concentration en Nacl 9% 4. Est maximale à PH7 5-Est sensible à la présence d'autres ligands que le substrat 6- Les hydrolases provoquent toujours la rupture d une liaison covalente entre un atome de carbone et un ato différent. 7- a Oxydase >>est un nom synonyme d'oxydoréductase. 8- Les réactions catalysées par les ligases font nécessairement intervenir de l'ATP.
- 19. Label the following as either a description of an event in meiosis.mitosis, or in both meiosis and mitosis. Use the following key: me=meiosis mi=mitosis bt=both 1 __ chromosomes condense during the division 2. __ crossing-over occurs during the division 3. __ cytokinesis and de condensation occur at the end of the process 4. __ daughter cells are the same as parent cells 5. __ DNA must replicate before the process begins 6. __ end-products are not capable of further division by themselves 7. __ found only in 2n eukaryotic cells 8 __ granddaughter cells are formed as the end products become 9 __ has a long prophase 10. __ has two stages of division 11. __ homologous chromosomes align independently on the equatorial plate 12. __ interphase only occurs before the division 13. __ nuclear envelopes disintegrate in preparation for cellular division 14. __ occurs only in reproductive organs 15 __ spindle fibres are produced to guide division of genetic material 16. __ tetrads are formed 17. __ interphase occurs in the middle of the process 18. __ telophase is the final process
