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Blood Vessels Figures

Figure 111

DNA information is transcribed into mRNA, which in turn is translated into a sequence of amino acids.

Figure 111

DNA information is transcribed into mRNA, which in turn is translated into a sequence of amino acids.

Figure 4.23

Next amino acid

Transfer RNA

Next amino acid

Vasos Sangu Neos

Transfer RNA

Messenger RNA

Messenger RNA

Messenger RNA

Messenger RNA

Messenger RNA

Messenger RNA

Molecules of transfer RNA (tRNA) attach to and carry specific amino acids, aligning them in the sequence determined by the codons of mRNA. These amino acids, connected by peptide bonds, form the polypeptide chain of a protein molecule.

Protein Synthesis

Protein Synthesis

Transcription (Within the Nucleus)

1. RNA polymerase binds to the base sequence of a gene.

2. This enzyme unwinds a portion of the DNA molecule, exposing part of the gene.

3. RNA polymerase moves along one strand of the exposed gene and catalyzes synthesis of an mRNA molecule, whose nucleotides are complementary to those of the strand of the gene.

4. When RNA polymerase reaches the end of the gene, the newly formed mRNA molecule is released.

5. The DNA molecule rewinds and closes the double helix.

6. The mRNA molecule passes through a pore in the nuclear envelope and enters the cytoplasm.

Translation (Within the Cytoplasm)

1. A ribosome binds to the mRNA molecule near the codon at the beginning of the messenger strand.

2. A tRNA molecule that has the complementary anticodon brings its amino acid to the ribosome.

3. A second tRNA brings the next amino acid to the ribosome.

4. A peptide bond forms between the two amino acids, and the first tRNA is released.

5. This process is repeated for each codon in the mRNA sequence as the ribosome moves along its length, forming a chain of amino acids.

6. As the chain of amino acids grows, it folds, with the help of chaperone proteins, into the unique conformation of a functional protein molecule.

7. The completed protein molecule (polypeptide) is released. The mRNA molecule, ribosome, and tRNA molecules are recycled.

What is the function of DNA?

How is information carried from the nucleus to the cytoplasm?

How are protein molecules synthesized?

Some antibiotic drugs fight infection by interfering with bacterial protein synthesis, RNA transcription, or DNA replication. Rifampin is a drug that blocks bacterial transcription by binding to RNA polymerase, preventing the gene's message from being transmitted. Streptomycin is an antibiotic that binds a bacterium's ribo-somal subunits, braking protein synthesis to a halt. Quinolone blocks an enzyme that unwinds bacterial DNA, preventing both transcription and DNA replication. Humans have different ribosomal subunits and transcription and replication enzymes than bacteria, so the drugs do not affect these processes in us.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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