chapter 17

Question 1

What is a protein?

Answer 1

A protein is a polypeptide formed from an amino acid chain.

Question 2

Describe the different functions of proteins.

Answer 2

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

Question 3

What is an essential amino acid?

Answer 3

An amino acid that must be taken in from the diet

Question 4

Describe the process of transcription

Answer 4

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.

Question 5

Where does transcription take place?

Answer 5

In the nucleus

Question 6

What enzyme transcribes mRNA?

Answer 6

RNA polymerase

Question 7

What are transcription factors?

Answer 7

Proteins that bind to the promoter of the gene

Question 8

What roles do transcription factors play in transcription?

Answer 8

Help the RNA polymerase to bind to the promoter

Question 9

Describe the process of translation

Answer 9

Translation is the making of a polypeptide, using information in the mRNA. It also has a three step process: initiation, elongation, and termination

Question 10

Where does translation occur?

Answer 10

ribosomes

Question 11

What is produced during translation?

Answer 11

A polypeptide (or protein)

Question 12

What is the “central dogma of molecular biology”?

Answer 12

DNA is transcribed into mRNA which is translated into a polypeptide (protein)

Question 13

What are codons?

Answer 13

A series of three mRNA nucleotides that correspond to a specific amino acid

Question 14

How many nucleotides are there per codon?

Answer 14

3

Question 15

What are start and stop codons?

Answer 15

Start = AUG; Stop= UAA, UAG, or UGA

Question 16

What is mRNA splicing?

Answer 16

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)

Question 17

What are the advantages of RNA splicing?

Answer 17

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

Question 18

Describe how ribosomes and various forms of RNA cooperated to translate mRNA into protein.

Answer 18

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

Question 19

Describe how tRNA moves through a ribosome during protein synthesis.

Answer 19

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

Question 20

Describe how translation is terminated.

Answer 20

the process is terminated when the stop codon is reached

Question 21

Which of the amino acids are essential amino acids?

Answer 21

Valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, threonine, lysine, and histidine