Unit 3 AOS 1 - What is the role of nucleic acids and proteins in maintaining life?

Question 1

nucleic acids

Answer 1

information molecules that encode instructions for the synthesis of proteins

Question 2

Polymer/Monomer of DNA/RNA

Answer 2

Polymer: Nucleic Acids
Monomer: Nucleotide

Question 3

Polymer/Monomer of Protein

Answer 3

Polymer: Polypeptide Chain
Monomer: Amino acid

Question 4

Functional groups in amino acids:

Answer 4

Amino group and Carboxyl Group

Question 5

Differences between DNA and RNA

Answer 5

DNA | RNA
Double strand | Single strand
Thymine | Uracil
Deoxyribose | Ribose

Question 6

What does degenerate/reduntant mean

Answer 6

more than one codon can code for a particular amino acid

Question 7

what is meant by universal in terms of genetic code

Answer 7

in all organisms on earth codons code for the same amino acids. genetic information is transferrable between species.

Question 8

mRNA

Answer 8

carries codes from the DNA in the nucleus to the site of protein synthesis in the cytoplasm ( the ribosome). As information in DNA cannot be decoded into proteins it is must be transcribed/copied into mRNA

Question 9

tRNA

Answer 9

brings specific information from the nucleus to the ribosome. carries amino acids to ribosomes and are linked to form proteins

Question 10

rRNA

Answer 10

combines with proteins to form the ribosome and is exported to the cytoplasm to help translate the information in mRNA into protein.

Question 11

What are the steps in transcription?

Answer 11

Initiation, Elongation, Termination

Question 12

What is Initiation?(In transcription)

Answer 12

• Transcriptional factors and RNA polymerase bind to the promoter region of the template strand.
• This signals the DNA to unzip, leaving the nucleotides of the DNA(most importantly the template strand) exposed.

Question 13

What is Elongation?(In transcription)

Answer 13

• RNA polymerase moves along and reads the template strand in 3’ to 5’ direction
• Using free nucleotides, it creates a strand of pre-mRNA which is complementary to the template strand which is identical to the coding strand beside the fact that thymine is switched with uracil

Question 14

What is termination?(In transcription)

Answer 14

• The RNA polymerase keeps making the pre-mRNA and reading the template strand of DNA until it reaches the termination sequence
• When the termination sequence is reached, RNA polymerase detaches from DNA which releases the pre-mRNA
• The DNA winds up again to form the double helix and transcription is finished

Question 15

What happens inbetween transcription and translation and explain it?

Answer 15

Post-transcriptional modification is when the introns are spliced out of the pre-mRNA and also the addition of the 3’ poly-a tail and the 5’ methyl-g cap. The remaining sequence of nucleic is only comprised of exons and is now called mRNA.

Question 16

What stabilises and prevents mRNA from degrading?

Answer 16

The 3’ poly-a tail and the 5’ methyl-g cap

Question 17

What enzymes are used for the removal of introns?

Answer 17

Spliceosomes

Question 18

What is alternative splicing and what are it’s benefits

Answer 18

It is when certain exons can be removed from the mRNA, creating a new mRNA strand. The benefit of this is that it increases protein diversity.

Question 19

Where does transcription occur?

Answer 19

In the nucleus

Question 20

Where does translation occur?

Answer 20

In a ribosome

Question 21

Where does post-transcriptional modification occur?

Answer 21

In the nucleus

Question 22

What are the steps to gene expression?

Answer 22

Transcription, post-transcriptional modification and translation

Question 23

What are the steps to translation?

Answer 23

Initiation, elongation, termination

Question 24

What is initiation(In translation)

Answer 24

• The 5’ of the mRNA attaches to the ribosome and is read until the start codon is read AUG
• Then the first tRNA brings an amino acid to the ribosomal complex which signals the start of translation

Question 25

What is elongation(In translation)

Answer 25

- The ribosome continues to read the mRNA - tRNA with their complementary anticodons to the mRNA codons bring their amino acids and add them to the polypeptide chain through condensation polymerisation - The tRNA is now able to leave the ribosome and pick up another free amino acid

Question 26

What reaction occurs through the creation of the bonds between amino acids and what does it create as a by-product

Answer 26

Condensation polymerisation occurs and water is created as a by-product

Question 27

What is termination(In translation)

Answer 27

- The ribosome reads the mRNA until it reaches the stop codon which signals the end of translation - The polypeptide chain of amino acids Is released into the cytosol or an endoplasmic reticulum

Question 28

What bonds form between amino acids in a polypeptide chain

Answer 28

Peptide bonds

Question 29

What bonds occur between the bases in nucleic acid

Answer 29

Hydrogen Bonds

Question 30

What bonds occur between the sugar and phosphate groups in nucleic acid

Answer 30

Sugar-phosphate bonds

Question 30

What are introns

Answer 30

Non-coding regions of DNA Removing during RNA processing Only found in eukaryotic genes

Question 31

Exons

Answer 31

Coding regions of DNA Transcribed and translated to form protein In eukaryotic and prokaryotic genes

Question 32

Operator

Answer 32

Serves as binding site for repressor proteins

Question 33

In low levels of tryptophan...

Answer 33

Repressor protein unable to bind with tryptophan Unable to go conformational change Cannot bind to the operator RNA polymerase transcribes structural genes

Question 34

In high levels of tryptophan...

Answer 34

Repressor protein binds with tryptophan Repressor undergoes a conformational change Binds to the oppressor RNA polymerase is unable to transcribe structural genes to produce tryptophan

Question 34

Eukaryotic Genes

Answer 34

One promoter per gene No operator region linear chromosomes

Question 35

Prokaryotic Genes

Answer 35

One promoter and operator for multiple genes Operator region where repressor proteins bind No introns Circular chromosomes

Question 36

Primary Structure

Answer 36

Sequence of amino acids Peptide bonds (Polypeptide chain)

Question 37

Secondary Structure

Answer 37

Folded polypeptide chain Hydrogen bonds between amino acids Alpha helice + beta pleated sheets Random coils

Question 38

Tertiary structure

Answer 38

3 dimensional Folded beta pleated sheets + alpha helice Hydrogen bonds between R group of amino acids Disulphide bonds between cysteine amino acids Ionic bonds between charged amino acids

Question 39

Quaternary Structure

Answer 39

Two or more tertiary structures Polypeptide chain with prosthetic group also considered quaternary structure.

Question 40

The role of the Rough endoplasmic reticulum

Answer 40

- Within the cytoplasm of eukaryotic cells - Outer surface covered with ribosomes. - Proteins synthesised by ribosomes - Packaged into vesicle to be transported to the Golgi