Nucleic acids & DNA replication

Question 1

DNA polymerase action on strand

Answer 1

• Syntheses the leading strand in a continuous manner, whereas the lagging strand is synthesised discontinuously (producing and joining Okazaki fragments)

Question 2

rRNA

Answer 2

• RNA molecule that forms the structural and catalytic core of the ribosome

Question 3

mRNA

Answer 3

• Mature and functional RNA molecule that specifies the amino acid sequence of a protein

Question 4

tRNA

Answer 4

• Adaptor that “reads” a codon in mRNA and adds the correct amino acid to the growing polypeptide chain

Question 5

Pre-mRNA

Answer 5

the RNA transcript of a gene produced by transcription and subjected to RNA maturation

Question 6

Ribosomes and innitiation of translation

Answer 6

• The small ribosomal subunit (40S) attaches to the tRNA carrying Methionine (the first amino acid of the polypeptide chain)
• The small ribosomal subunit (40S) binds to the 5’ end of the mRNA, by recognising the 5’ cap modification added during RNA processing step
• The small ribosomal subunit (40S) slides along the mRNA, stopping when they reach the start codon
• The large ribosomal subunit (60S) joins the small ribosomal subunit (40S) to form the initiation complex (80S)

Question 7

Coenzyme

Answer 7

• A specific type of coenzymes is represented by prosthetic groups (firmly attached to an enzyme)
• Coenzymes are organic (carbon-containing) cofactors
• A specific type of coenzymes is represented by cosubstrates (weakly/temporarily bound to an enzyme)
• They provide additional organic groups required for the activity of some enzymes, converting them into their active forms (from apoenzyme to holoenzyme)

Question 8

Oxidoreductases

Answer 8

Transfer electrons from one molecule (oxidant) to another one (reductant)

Question 9

Hydrolase

Answer 9

Cleave/break specific types of covalent bonds, transferring groups to water

Question 10

Transferase

Answer 10

Transfer of specific functional groups from one molecule (donor) to another one (acceptor)

Question 11

Isomerase

Answer 11

Convert one isomer to another

Question 12

Lyases

Answer 12

Break a chemical bond between two parts of a molecule (other than hydrolysis or oxidative bond breaking)

Question 13

Translocases

Answer 13

Assisting in moving molecules, usually across a cell membrane

Question 14

Ligases

Answer 14

Join two molecules by forming a new chemical bond