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Major Constituents of Cell
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Largest organelle (5 m in diameter)
Nucleus Largest organelle (5 m in diameter) some anuclear or multinucleate Nuclear envelope two unit membranes held together at nuclear pores Nucleoplasm chromatin (thread-like matter) = DNA and protein nucleoli = dark masses where ribosomes produced
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Kornberg & DNA polymerization
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Control of Cell Division
Surface-to-volume ratio of cells Contact inhibition
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Endoplasmic Reticulum
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Granules of protein and RNA
Ribosomes Granules of protein and RNA found in nucleoli, free in cytosol and on rough ER Uses directions in messenger RNA to assemble amino acids into proteins specified by the genetic code (DNA)
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Protein Synthesis DNA serves as master blueprint for protein synthesis Genes are segments of DNA carrying instructions for a polypeptide chain Triplets of nucleotide bases form the genetic library Each triplet specifies coding for an amino acid
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From DNA to Protein Nuclear envelope DNA Transcription Pre-mRNA
RNA Processing mRNA Ribosome Translation Polypeptide Figure 3.33
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From DNA to Protein DNA Figure 3.33
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From DNA to Protein Transcription DNA Figure 3.33
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From DNA to Protein DNA Transcription Pre-mRNA RNA Processing mRNA
Figure 3.33
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From DNA to Protein Nuclear envelope DNA Transcription Pre-mRNA
RNA Processing mRNA Figure 3.33
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From DNA to Protein Nuclear envelope DNA Transcription Pre-mRNA
RNA Processing mRNA Ribosome Translation Polypeptide Figure 3.33
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Roles of the Three Types of RNA
Messenger RNA (mRNA) – carries the genetic information (codons) from DNA Transfer RNAs (tRNAs) – carries amino acids contains anti-codon Ribosomal RNA (rRNA) – a structural component of ribosomes
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Transcription Figure 3.34 Coding strand RNA polymerase Unwinding
Termination signal Promoter Template strand Transcription unit Unwound DNA RNA polymerase In a process mediated by a transcription factor, RNA polymerase binds to promoter and unwinds 16–18 base pairs of the DNA template strand RNA polymerase bound to promoter RNA nucleotides mRNA synthesis begins mRNA RNA nucleotides RNA polymerase moves down DNA; mRNA elongates RNA polymerase mRNA synthesis is terminated DNA (a) mRNA transcript Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.34 Coding strand RNA polymerase Unwinding Rewinding of DNA
Termination signal Promoter Template strand Transcription unit (a) Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.34 Coding strand RNA polymerase Unwinding Rewinding of DNA
Termination signal Promoter Template strand Transcription unit Unwound DNA RNA polymerase In a process mediated by a transcription factor, RNA polymerase binds to promoter and unwinds 16–18 base pairs of the DNA template strand RNA polymerase bound to promoter (a) Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.34 Coding strand RNA polymerase Unwinding Rewinding of DNA
Termination signal Promoter Template strand Transcription unit Unwound DNA RNA polymerase In a process mediated by a transcription factor, RNA polymerase binds to promoter and unwinds 16–18 base pairs of the DNA template strand RNA polymerase bound to promoter RNA nucleotides mRNA synthesis begins (a) Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.34 Coding strand RNA polymerase Unwinding Rewinding of DNA
Termination signal Promoter Template strand Transcription unit Unwound DNA RNA polymerase In a process mediated by a transcription factor, RNA polymerase binds to promoter and unwinds 16–18 base pairs of the DNA template strand RNA polymerase bound to promoter RNA nucleotides mRNA synthesis begins mRNA (a) Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.34 Coding strand RNA polymerase Unwinding Rewinding of DNA
Termination signal Promoter Template strand Transcription unit Unwound DNA RNA polymerase In a process mediated by a transcription factor, RNA polymerase binds to promoter and unwinds 16–18 base pairs of the DNA template strand RNA polymerase bound to promoter RNA nucleotides mRNA synthesis begins mRNA RNA nucleotides RNA polymerase moves down DNA; mRNA elongates (a) Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.34 Coding strand RNA polymerase Unwinding Rewinding of DNA
Termination signal Promoter Template strand Transcription unit Unwound DNA RNA polymerase In a process mediated by a transcription factor, RNA polymerase binds to promoter and unwinds 16–18 base pairs of the DNA template strand RNA polymerase bound to promoter RNA nucleotides mRNA synthesis begins mRNA RNA nucleotides RNA polymerase moves down DNA; mRNA elongates RNA polymerase mRNA synthesis is terminated DNA (a) mRNA transcript Coding strand RNA polymerase Unwinding of DNA Rewinding of DNA Template strand RNA nucleotides mRNA RNA-DNA hybrid region (b) Figure 3.34
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Figure 3.36 Nucleus Nuclear membrane RNA polymerase Nuclear pore mRNA
Released mRNA mRNA Template strand of DNA RNA polymerase Nuclear pore Nuclear membrane Nucleus Figure 3.36
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Figure 3.36 1 Nucleus Nuclear membrane RNA polymerase Nuclear pore
mRNA Template strand of DNA Released mRNA 1 After mRNA processing, mRNA leaves nucleus and attaches to ribosome, and translation begins. Small ribosomal subunit Codon 15 Codon 16 Codon 17 Direction of ribosome advance Portion of mRNA already translated Large ribosomal subunit Figure 3.36
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Figure 3.36 1 Nucleus Nuclear membrane RNA polymerase Nuclear pore
mRNA Template strand of DNA Amino acids Released mRNA 1 After mRNA processing, mRNA leaves nucleus and attaches to ribosome, and translation begins. tRNA Aminoacyl-tRNA synthetase Small ribosomal subunit Codon 15 Codon 16 Codon 17 Direction of ribosome advance Portion of mRNA already translated Large ribosomal subunit Energized by ATP, the correct amino acid is attached to each species of tRNA by aminoacyl-tRNA synthetase enzyme. Figure 3.36
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Figure 3.36 1 2 Nucleus Nuclear membrane RNA polymerase Nuclear pore
mRNA Template strand of DNA Amino acids Released mRNA 1 After mRNA processing, mRNA leaves nucleus and attaches to ribosome, and translation begins. tRNA Aminoacyl-tRNA synthetase Small ribosomal subunit Codon 15 Codon 16 Codon 17 Direction of ribosome advance Portion of mRNA already translated tRNA “head” bearing anticodon Large ribosomal subunit Energized by ATP, the correct amino acid is attached to each species of tRNA by aminoacyl-tRNA synthetase enzyme. 2 Incoming aminoacyl- tRNA hydrogen bonds via its anticodon to complementary mRNA sequence (codon) at the A site on the ribosome. Figure 3.36
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Figure 3.36 1 2 3 Nucleus Nuclear membrane RNA polymerase Nuclear pore
mRNA Template strand of DNA Amino acids Released mRNA 1 After mRNA processing, mRNA leaves nucleus and attaches to ribosome, and translation begins. tRNA Aminoacyl-tRNA synthetase Small ribosomal subunit Codon 15 Codon 16 Codon 17 Direction of ribosome advance Portion of mRNA already translated tRNA “head” bearing anticodon Large ribosomal subunit Energized by ATP, the correct amino acid is attached to each species of tRNA by aminoacyl-tRNA synthetase enzyme. 2 Incoming aminoacyl- tRNA hydrogen bonds via its anticodon to complementary mRNA sequence (codon) at the A site on the ribosome. 3 As the ribosome moves along the mRNA, a new amino acid is added to the growing protein chain and the tRNA in the A site is translocated to the P site. Figure 3.36
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Figure 3.36 1 2 4 3 Nucleus Nuclear membrane RNA polymerase
Nuclear pore mRNA Template strand of DNA Amino acids Released mRNA 1 After mRNA processing, mRNA leaves nucleus and attaches to ribosome, and translation begins. tRNA Aminoacyl-tRNA synthetase Small ribosomal subunit Codon 15 Codon 16 Codon 17 Direction of ribosome advance Portion of mRNA already translated tRNA “head” bearing anticodon Large ribosomal subunit Energized by ATP, the correct amino acid is attached to each species of tRNA by aminoacyl-tRNA synthetase enzyme. 2 Incoming aminoacyl- tRNA hydrogen bonds via its anticodon to complementary mRNA sequence (codon) at the A site on the ribosome. 4 Once its amino acid is released, tRNA is ratcheted to the E site and then released to reenter the cytoplasmic pool, ready to be recharged with a new amino acid. 3 As the ribosome moves along the mRNA, a new amino acid is added to the growing protein chain and the tRNA in the A site is translocated to the P site. Figure 3.36
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RNA codons code for amino acids according to a genetic code
mutations multiple codons Figure 3.35
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Information Transfer from DNA to RNA
Figure 3.38
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Developmental Aspects of Cells
All cells of the body contain the same DNA but Genes of specific cells are turned on or off (i.e., by methylation of their DNA) Cell specialization is determined by the kind of proteins that are made in that cell muscle cell vs. nerve cell
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Endoplasmic Reticulum (ER)
Figure 3.18a, c
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Golgi Complex
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Signal Mechanism of Protein Synthesis
mRNA – ribosome complex is directed to rough ER by a signal-recognition particle (SRP) Cytosol Ribosomes mRNA Coatomer- coated transport vesicle Transport budding off Released glycoprotein ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site Sugar group removed Growing polypeptide 1 2 3 4 5
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Signal Mechanism of Protein Synthesis
Cytosol mRNA ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site 1 Figure 3.19
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Signal Mechanism of Protein Synthesis
Cytosol mRNA ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site Growing polypeptide 1 2 Figure 3.19
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Signal Mechanism of Protein Synthesis
Cytosol Ribosomes mRNA ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site removed Growing polypeptide 1 2 3 Figure 3.19
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Signal Mechanism of Protein Synthesis
Cytosol Ribosomes mRNA Released glycoprotein ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site removed Growing polypeptide 1 2 3 4 Figure 3.19
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Signal Mechanism of Protein Synthesis
Cytosol Ribosomes mRNA Transport vesicle budding off Released glycoprotein ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site Sugar group removed Growing polypeptide 1 2 3 4 5 Figure 3.19
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Signal Mechanism of Protein Synthesis
Cytosol Ribosomes mRNA Coatomer- coated transport vesicle Transport budding off Released glycoprotein ER cisterna membrane Signal- recognition particle (SRP) Signal sequence Receptor site Sugar group removed Growing polypeptide 1 2 3 4 5 Figure 3.19
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Role of the Golgi Apparatus
Secretion by exocytosis Extracellular fluid Plasma membrane Vesicle incorporated into plasma membrane Coatomer coat Lysosomes containing acid hydrolase enzymes Phagosome Proteins in cisterna Membrane Vesicle Pathway 3 Pathway 2 Secretory vesicles Proteins Pathway 1 Golgi apparatus Cisterna Rough ER Figure 3.21
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