Proteins, Cell Signalling and Transcription

Question 1

What is transcription?

Answer 1

The process by which sequences of deoxyribonucleic acid (DNA) produce specific messenger ribonucleic acid (mRNA) sequences.

Question 2

What is translation?

Answer 2

The process by which mRNA determines the final amino acid sequence via transfer ribonucleic acid (tRNA) within a ribosome.

Question 3

What is the start codon sequence?

Answer 3

AUG (also codes for methionine)

Question 4

What are the stop codons?

Answer 4

UAA, UAG or UGA

Question 5

What kind of bonds cause the primary structure of polypeptides to form?

Answer 5

Peptide, through a condensation reaction

Question 6

What kind of bonds cause the secondary structure of polypeptides to form?

Answer 6

Hydrogen bonds (alpha helices and beta pleated sheets)

Question 7

How is a polypeptide’s tertiary structure formed?

Answer 7

The helices or sheets fold forming a unique 3D structure. This is caused by various bonding arrangements

Question 8

How is a protein’s quaternary structure formed?

Answer 8

More than one polypeptide/protein chain joined together. Fibrous or globular proteins result. An example of a globular protein is haemoglobin

Question 9

What is the amino acid substitution in sickle cell?

Answer 9

Valine is coded instead of glutamic acid

Question 10

Proteins consist of a primary structure of bases linked via peptide bonds T/F

Answer 10

False. Proteins or polypeptides possess a primary structure of amino acids linked via peptide bonds.

Question 11

Proteins are folded into helices stabilized by hydrogen bonds T/F

Answer 11

The polypeptide chains are arranged into secondary alpha helices and beta-pleated sheets stabilized by hydrogen bonds.

Question 12

Proteins rarely have tertiary or quaternary structure T/F

Answer 12

False. The helices or sheets fold, forming a unique tertiary 3D structure. When more than one polypeptide chain is joined together, e.g. the alpha and beta chains in haemoglobin, a quaternary structure results.

Question 13

Haemoglobin is an example of a protein with a quaternary structure T/F

Answer 13

True

Question 14

During transcription uracil in mRNA pairs to the adenine on DNA T/F

Answer 14

True

Question 15

Transcription requires DNA polymerase T/F

Answer 15

False. Transcription requires RNA polymerase.

Question 16

The cytoplasm is the key site of transcription T/F

Answer 16

False. Transcription occurs in the nucleus.

Question 17

Amino acids with corresponding bases attach to RNA in the ribosome T/F

Answer 17

False. This statement describes translation not transcription. Transcription is the formation of mRNA from DNA.

Question 18

Translation requires tRNA to bring amino acids to the ribosome T/F

Answer 18

True

Question 19

Translation occurs in the nucleus T/F

Answer 19

False. Translation occurs in the cytoplasm.

Question 20

Translation pairs mRNA adenine with tRNA thymine T/F

Answer 20

False. Translation pairs mRNA adenine with tRNA uracil; RNA does not contain thymine.

Question 21

Translation requires the anti-codon sequence of tRNA to complement the codon sequence of mRNA T/F

Answer 21

True. Translation requires the anti-codon sequence of tRNA to complement the codon sequence of mRNA.

Question 22

Translation needs the action of aminoacyl tRNA polymerase to attach amino acids to tRNA T/F

Answer 22

False. Translation requires the action of aminoacetyl tRNA synthetase.

Question 23

Oestrogen enters its target cell via diffusion T/F

Answer 23

True. Oestrogen is fat soluble and diffuses into target cells.

Question 24

Oestrogen is not classed as a steroid hormone T/F

Answer 24

False. Oestrogen is classed as a steroid hormone.

Question 25

Thyroid hormone binds to a cytosol receptor to form a hormone/receptor complex T/F

Answer 25

False. Thyroid hormone binds to a nuclear receptor; oestrogen binds to its cytosol receptor, then the complex enters the nucleus.

Question 26

Thyroid hormone receptor binds to DNA and affects transcription without the presence of thyroid hormone T/F

Answer 26

True. Thyroid hormone receptor binds to DNA and represses transcription when thyroid hormone is not present.

Question 27

Hormones can affect genetic transcription in the cell nucleus T/F

Answer 27

True

Question 28

Hormones act exclusively via cell membrane receptors T/F

Answer 28

False. Thyroid and steroid hormones affect DNA transcription via intracellular nuclear or cytoplasm receptors. Their actions tend to be slower in onset than those of hormones affecting cell membrane receptors.