chapter 17 Flashcards
What is a protein?
A protein is a polypeptide formed from an amino acid chain.
Describe the different functions of proteins.
Enzymes: speed up chemical reactions Storage: store amino acids Defensive: protect against disease Transport: transport substances across cell membrane or around body Structural: support within the cell Contractile/motor proteins: movement
What is an essential amino acid?
An amino acid that must be taken in from the diet
Describe the process of transcription
It is the process by which the information in a strand of DNA is copied into a new molecule of messenger (mRNA). It goes through a three step process: initiation, elongation, and termination.
Where does transcription take place?
In the nucleus
What enzyme transcribes mRNA?
RNA polymerase
What are transcription factors?
Proteins that bind to the promoter of the gene
What roles do transcription factors play in transcription?
Help the RNA polymerase to bind to the promoter
Describe the process of translation
Translation is the making of a polypeptide, using information in the mRNA. It also has a three step process: initiation, elongation, and termination
Where does translation occur?
ribosomes
What is produced during translation?
A polypeptide (or protein)
What is the “central dogma of molecular biology”?
DNA is transcribed into mRNA which is translated into a polypeptide (protein)
What are codons?
A series of three mRNA nucleotides that correspond to a specific amino acid
How many nucleotides are there per codon?
3
What are start and stop codons?
Start = AUG; Stop= UAA, UAG, or UGA
What is mRNA splicing?
A process by which the RNA strand is processed; usually some interior parts of the molecule are cut out (introns), and the other parts spliced together (exons)
What are the advantages of RNA splicing?
It allows genes to encode more than one kind of polypeptide, making the number of different proteins that an organism can produce much greater than its number of genes
Describe how ribosomes and various forms of RNA cooperated to translate mRNA into protein.
mRNA carries the code of DNA to the ribosome which is made of rRNA; the tRNA carries the amino acids that correspond to the mRNA codons to the ribosomes for translation
Describe how tRNA moves through a ribosome during protein synthesis.
a charged tRNA enters at the A site; the growing polypeptide bonds to its amino acid causing it to move to the P site; then its amino acid breaks off to bond to the next amino acid causing the tRNA to move to the E site and out of the ribosome
Describe how translation is terminated.
the process is terminated when the stop codon is reached
Which of the amino acids are essential amino acids?
Valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, threonine, lysine, and histidine
