1. Fisiologia Celular Básica
Aula Teórica Nº 3
Fisiologia Celular Básica
2001/2002
Prof.Doutor José Cabeda

2. Prof.Doutor José Cabeda
Expressão Genética
2001/2002
Prof.Doutor José Cabeda

3. Molecular definition of a gene
A gene is the entire nucleic acid sequence that is necessary for the synthesis of a functional polypeptide
DNA regions that code for RNA molecules such as tRNA and rRNA may also be considered genes
In eukaryotes, genes lie amidst a large expanse of nonfunctional, noncoding DNA and genes may also contain regions of noncoding DNA
2001/2002
Prof. Doutor José Cabeda

4. Prof. Doutor José Cabeda
Bacterial operons produce polycistronic mRNAs while most eukaryotic mRNAs are monocistronic and contain introns
Figure 9-1
2001/2002
Prof. Doutor José Cabeda

5. Organizing cellular DNA into chromosomes
Most bacterial chromosomes are circular with one replication origin
Eukaryotic chromosomes each contain one linear DNA molecule and multiple origins of replication
Bacterial DNA is associated with polyamines
Eukaryotic DNA associates with histones to form chromatin
2001/2002
Prof. Doutor José Cabeda

6. Chromatin exists in extended and condensed forms
Figure 9-29
2001/2002
Prof. Doutor José Cabeda

7. Nucleosomes are complexes of histones
Figure 9-30
2001/2002
Prof. Doutor José Cabeda

8. The solenoid model of condensed chromatin
Figure 9-31
2001/2002
Prof. Doutor José Cabeda

9. A model for chromatin packing in metaphase chromosomes
Figure 9-35
2001/2002
Prof. Doutor José Cabeda

10. Stained chromosomes have characteristic banding patterns
Figure 9-38
2001/2002
Prof. Doutor José Cabeda

11. Chromosome painting distinguishes each homologous pair by color
Figure 9-0
2001/2002
Prof. Doutor José Cabeda

12. Mitochondrial genetic codes differ from the standard genetic code
2001/2002
Prof. Doutor José Cabeda

13. Bacterial gene control: the Jacob-Monod model
Cis acting DNA sequences
Trans-acting genes/proteins
Figure 10-2
2001/2002
Prof. Doutor José Cabeda

14. 10.2 Bacterial transcription initiation
RNA polymerase initiates transcription of most genes at a unique DNA position lying upstream of the coding sequence
The base pair where transcription initiates is termed the transcription-initiation site or start site
By convention, the transcription-initiation site in the DNA sequence is designated +1, and base pairs extending in the direction of transcription (downstream) are assigned positive numbers which those extending in the opposite direction (upstream) are assigned negative numbers
Various proteins (RNA polymerase, activators, repressors) interact with DNA at or near the promoter to regulate transcription initiation
2001/2002
Prof. Doutor José Cabeda

15. DNase I footprinting assays identify protein-DNA interactions
Figure 10-6
2001/2002
Prof. Doutor José Cabeda

16. Gel-shift assays identify protein-DNA interactions
Figure 10-7
2001/2002
Prof. Doutor José Cabeda

17. Prof. Doutor José Cabeda
Most bacterial repressors are dimers containing  helices that insert into adjacent major grooves of operator DNA
Figure 10-13
2001/2002
Prof. Doutor José Cabeda

18. Prof. Doutor José Cabeda
Ligand-induced conformational changes alter affinity of many repressors for DNA
Tryptophan binding induces a conformational change in the trp aporepressor
Figure 10-14
2001/2002
Prof. Doutor José Cabeda

19. Prof. Doutor José Cabeda
Many genes in higher eukaryotes are regulated by controlling their transcription
The nascent chain (run-on) assay allows measurement of the rate of transcription of a given gene
Figure 10-22
2001/2002
Prof. Doutor José Cabeda

20. Prof. Doutor José Cabeda
Regulatory elements in eukaryotic DNA often are many kilobases from start sites
The basic principles that control transcription in bacteria also apply to eukaryotic organisms: transcription is initiated at a specific base pair and is controlled by the binding of trans-acting proteins (transcription factors) to cis-acting regulatory DNA sequences
However, eukaryotic cis-acting elements are often much further from the promoter they regulate, and transcription from a single promoter may be regulated by binding of multiple transcription factors to alternative control elements
Transcription control sequences can be identified by analysis of a 5-deletion series
2001/2002
Prof. Doutor José Cabeda

21. Construction and analysis of a 5-deletion series
Figure 10-24
2001/2002
Prof. Doutor José Cabeda

22. Three eukaryotic polymerases catalyze formation of different RNAs
I: pre-rRNA
II: mRNA
III: tRNAs, 5S rRNA,
small stable RNAs
Figure 10-25
2001/2002
Prof. Doutor José Cabeda

23. The TATA box is a highly conserved promoter in eukaryotic DNA
Alternative promoters in eukaryotes include initiators and CpG islands
Figure 10-30
2001/2002
Prof. Doutor José Cabeda

24. Prof. Doutor José Cabeda
Most eukaryotic genes are regulated by multiple transcription control mechanisms
Figure 10-34
2001/2002
Prof. Doutor José Cabeda

25. Prof. Doutor José Cabeda
Transcriptional activators are modular proteins composed of distinct functional domains
Figure 10-39
2001/2002
Prof. Doutor José Cabeda

26. DNA-binding domains can be classified into numerous structural types
Homeodomain proteins
Zinc-finger proteins
Winged-helix (forkhead) proteins
Leucine-zipper proteins
Helix-loop-helix proteins
2001/2002
Prof. Doutor José Cabeda

27. Prof. Doutor José Cabeda
Homeodomain from Engrailed protein interacting with its specific DNA recognition site
Figure 10-40
2001/2002
Prof. Doutor José Cabeda

28. Interactions of C2H2 and C4 zinc-finger domains with DNA
Figure 10-41
2001/2002
Prof. Doutor José Cabeda

29. Interaction between a C6 zinc-finger protein (Gal4) and DNA
Figure 10-42
2001/2002
Prof. Doutor José Cabeda

30. Interaction of a homodimeric leucine-zipper protein and DNA
Figure 10-43
2001/2002
Prof. Doutor José Cabeda

31. Interaction of a helix-loop-helix in a homodimeric protein and DNA
Figure 10-44
2001/2002
Prof. Doutor José Cabeda

32. Schematic model of silencing at yeast telomeres
Figure 10-57
2001/2002
Prof. Doutor José Cabeda

33. Prof. Doutor José Cabeda
Repressors and activators can direct histone deactylation at specific genes
Figure 10-58
2001/2002
Prof. Doutor José Cabeda

34. Prof. Doutor José Cabeda
Model for cooperative assembly of an activated transcription-initiation complex in the TTR promoter
Figure 10-61
2001/2002
Prof. Doutor José Cabeda

35. Prof. Doutor José Cabeda
Repressors interfere directly with transcription initiation in several ways
Figure 10-62
2001/2002
Prof. Doutor José Cabeda

36. Lipid-soluble hormones control the activities of nuclear receptors
Figure 10-63
2001/2002
Prof. Doutor José Cabeda

37. Processing of eukaryotic mRNA
Figure 11-7
2001/2002
Prof. Doutor José Cabeda

38. Prof. Doutor José Cabeda
The 5-cap is added to nascent RNAs after initiation by RNA polymerase II
Figure 11-8
2001/2002
Prof. Doutor José Cabeda

39. Multiple protein isoforms are common in the vertebrate nervous system
Alternative splicing of slo mRNA, which encodes a Ca2+-gated K+ channel in auditory hair cells, contributes to the perception of sounds of different frequencies
Figure 11-27
2001/2002
Prof. Doutor José Cabeda

40. Model for passage of mRNPs through nuclear pore complexes
Figure 11-31
2001/2002
Prof. Doutor José Cabeda

41. Prof. Doutor José Cabeda
Proteins with a nuclear-localization signal (NLS) are recognized by receptors and transported into the nucleus
Figure 11-35
2001/2002
Prof. Doutor José Cabeda

42. A model for the import of cytosolic cargo proteins bearing a basic NLS
Figure 11-37
2001/2002
Prof. Doutor José Cabeda

43. The roles of RNA in protein synthesis
Figure 4-20
2001/2002
Prof. Doutor José Cabeda

44. The genetic code is a triplet code
2001/2002
Prof. Doutor José Cabeda

45. The genetic code can be read in different frames
Figure 4-21
2001/2002
Prof. Doutor José Cabeda

46. Prof. Doutor José Cabeda
Simultaneous translation by multiple ribosomes and their rapid recycling increases the efficiency of protein synthesis
Figure 4-42
2001/2002
Prof. Doutor José Cabeda

47. Prof. Doutor José Cabeda
Animações
Transcrição
Pós-tradução
2001/2002
Prof. Doutor José Cabeda

48. Processos fisiológicos dependentes de membranas
2001/2002
Prof.Doutor José Cabeda

49. As membranas biológicas exibem permeabilidade selectiva
2001/2002
Prof. Doutor José Cabeda

50. Prof. Doutor José Cabeda
Transporte passivo
Figure 15-2
2001/2002
Prof. Doutor José Cabeda

51. Overview of membrane transport proteins
Figure 15-3
2001/2002
Prof. Doutor José Cabeda

52. Uniporter-catalyzed transport
Uniporters accelerate a reaction that is already thermodynamically favored (similar to enzymes)
This type of transport is termed facilitated transport or facilitated diffusion
Three main features distinguish uniport transport (facilitated diffusion) from passive diffusion
The rate of facilitated diffusion is much higher than passive diffusion
Transport is specific
Transport occurs via a limited number of uniporters
2001/2002
Prof. Doutor José Cabeda

53. Prof. Doutor José Cabeda
A comparison of the uptake rate of glucose by facilitated diffusion and passive diffusion
Figure 15-5
2001/2002
Prof. Doutor José Cabeda

54. Prof. Doutor José Cabeda
Ionic gradients and an electric potential are maintained across the plasma membrane
2001/2002
Prof. Doutor José Cabeda

55. Prof. Doutor José Cabeda
The membrane potential in animal cells depends largely on K+ resting potential
Figure 15-8
2001/2002
Prof. Doutor José Cabeda

56. Active transport by ATP-powered pumps
Figure 15-10
2001/2002
Prof. Doutor José Cabeda

57. Prof. Doutor José Cabeda
AE1 protein, a Cl-/HCO3- antiporter, is crucial to CO2 transport by erythrocytes
Figure 15-20
2001/2002
Prof. Doutor José Cabeda

58. Prof. Doutor José Cabeda
Transepithelial movement of glucose and amino acids requires multiple transport proteins
Figure 15-25
2001/2002
Prof. Doutor José Cabeda

59. Prof. Doutor José Cabeda
Parietal cells acidify the stomach contents while maintaining a neutral cytosolic pH
Figure 15-26
2001/2002
Prof. Doutor José Cabeda

60. Osmotic pressure causes water to move across membranes
Figure 15-30
2001/2002
Prof. Doutor José Cabeda

61. Prof. Doutor José Cabeda
Water channels are necessary for bulk flow of water across cell membranes
Aquaporin is a water channel that increases a membrane’s permeability to water
Figure 15-32
2001/2002
Prof. Doutor José Cabeda

62. Prof. Doutor José Cabeda
The structure of aquaporin, a water channel protein in the erythocyte plasma membrane
Figure 15-33
2001/2002
Prof. Doutor José Cabeda

63. Changes in intracellular osmotic pressure cause leaf stomata to open
Figure 15-34
2001/2002
Prof. Doutor José Cabeda