Proteins

Question 1

Features if genetic code

Answer 1

Non overlapping : each base in sequence only read once
Universal : each triplet codes for same amino acid in all organisms
Degenerate : most amino acids coded for by more than one triplet

Question 2

Process of protein synthesis

Answer 2

DNA provides the instructions in the form of long sequence of bases
Complimentary section of this sequence is made in form of molecule (PRE-mRNA) aka transcription
PRE-mRNA is spliced to form mRNA
mRNA is used as template to which complementary tRNA attach and amino acids they carry are linked to form polypeptide aka translation

Question 3

Transcription

Answer 3

Hydrogen bonds between DNA bases break
Only one strand acts as template
Free RNA nucleotides align by comp base pairing
In RNA uracil base pairs with adenine
RNA polymerase joins nucleotides by phosphodiester bond
Pre mRNA is spliced to form MRNA

Question 4

Role of RNA polymerase

Answer 4

Moves along template DNA strand and joins RNA nucleotides by phospohdiester bond formation

Question 5

Role of DNA helicase

Answer 5

Breaks hydrogen bonds between bases causing them to separate and exposé’s nucleotide bases

Question 6

Describe the process of semi-conservative replication of DNA.

Answer 6

1. DNA belicase breakes hydrogen bonds
2. both strands act as templates
3. Free nucleotides attach by complimentary base pairing
4. DNA polymerase joins nudeolides to new DNA strand
5. phosphodiester bond forms between nucleotides by c. reaction

Question 7

Genetic

Answer 7

Refers to the way the info about sequence of amino acids is coded for by the bases on mRNA

Question 8

Genome

Answer 8

Entire set of genes present in a cell/ organisms

Question 9

Proteome

Answer 9

The entire complement of proteins that can be expressed from genes

Question 10

Coding for amino acids

Answer 10

3 nucleotide bases
The codons can translate for 20 amino acids
Triplet codons do not overlap

Question 11

Features for Coding for amino acids

Answer 11

Different codons can translate for same amino acid = degenerate
The order of codons determines the amino acid sequence
Start codon (AUG) MET
Terminates with a stop codon
Code is universal

Question 12

Describe a Gene

Answer 12

Base sequence of DNA that codes for amino acid sequence of a polypeptide or functional RNA

Question 13

How change in one base along a DNA molecule may result in an enzyme becoming nonfunctional

Answer 13

Different base may code for different amino acid
Sequence of amino acids in polypeptide produced will be different
Change in primary structure
Enzyme shale will be different and may not fit S
E-S complexes cannot be formed

Question 14

mRNA

Answer 14

Used to make a copy of the genetic code contained on the DNA molecule and transfer to ribosomes
- mRNA is complementary to the DNA it codes for
- Single strand so can leave nuclear pore
- mRNA associates with ribosomes to initiate second stage of protein synthesis

Question 15

tRNA

Answer 15

Used to bring specific amino acids to the mRNA
Anticodon is complementary to mRNA codon
Allows ribosomes to link amino acids and build polypeptides

Question 16

rRNA

Answer 16

used for making ribosomes that are sites for protein synthesis

Question 17

Process or transcription

Answer 17

DNA helicase breaks hydrogen bonds holding two DNA strands exposing free nucleotides
Nucleotides on template strand pair up with complimentary RNA nucleotides
RNA polymerase joins nucleotides together by phosphodiester bond formation
Pre mRNA strand forms and DNA strand behind rejoins
RNA polymerase dethaches when met with stop codon

Question 18

How does transcription differ from replication

Answer 18

Only short segment of DNA is unwound not the whole strand
As RNA is being made arena polymerase not DNA is used
Only 1 strand of DNA is read (antisense)

Question 19

Splicing pre-mRNA

Answer 19

Bulk of euk genome has DNA sequences don’t code for proteins and not transcribed
Introns = non coding region
Exons = coding regions
Both present in pre-mRNA and removed by enzymes during transcription = mature MRNA which leaves nucleus to be translated into polypeptides

Question 20

Enzymes present in transcription and what they do

Answer 20

DNA helicase - breaks hydrogen bonds and unwinds section of DNA and exposes nucleotides
RNA polymerase - adds complimentary RNA nucleotides to form pre-mRNA

Question 21

What happens when the RNA polymerase attaches to the DNA at the start codon?

Answer 21

Forms phosphodiester bonds between RNA nucleotides on the pre-mRNA strand

Question 22

Translation

Answer 22

Process when the genetic information encoded in mRNA is translated into a sequence of amino acids in a polypeptide chain.

Question 23

What happens after mRNA leaves the nuclear pore

Answer 23

the mRNA will attach itself to a ribosome. A ribosome is composed of two halves, a large and a small subunit. During translation, ribosomal subunits assemble together on the strand of mRNA.

Question 24

Subunits

Answer 24

Each compose of RNA molecules and proteins
Small subunits binds to the mRNA
Large subunits has bindings sites for tRNA and catalyses peptide bonds between amino acids

Question 25

tRNA structure

Answer 25

In the cytoplasm are free amino acids and transfer RNA (tRNA) molecules In the cytoplasm are free amino acids Short single strand of RNA Folded into clover and held by H bonds At one end there’s a site where amino acids can bind to Other end threee unpaired bases = anticodons Only binds to specific amino acid Require energy from ATP

Question 26

Types of molecules which ribosomes is made

Answer 26

RNA Nuclei acids Proteins rRNA

Question 27

Primary structure of proteins

Answer 27

Sequence of amino acids that make up polypeptide chain and DNA determines sequence = shape and function of protein

Question 28

Secondary structure

Answer 28

Arrangement of polypeptide chains into regular repeating structure held tgt by hydrogen bonds can result in a helix or b pleated sheet

Question 29

Tertiary structure

Answer 29

Level of 3D organization causes by bonding between R groups of nearby acids includes disulfide ionic and hydrogen bonds

Question 30

Quaternary structure

Answer 30

Consist of two or more chains of polypeptides a prosethic group can be associated

Question 31

Chaperone proteins

Answer 31

Folding of protein depends on position and type of R-groups which determines which bonds are made Chaperons(HSP 70) bind to hydrophobic regions of polypeptides and prevent them from interacting with other hydrophobic regions and prevent misfolding HSP 60 allow polypeptide chains to fit within them and isolate them

Question 32

What’s an anticodon

Answer 32

Triplet of bases on tRNA which is complementary to binding site on mRNA.

Question 33

two differences between the structure of mRNA and the structure of tRNA (5)

Answer 33

MRNA does not have H-bonds / base pairing, tRNA does OR mRNA is linear / straight chain, tRNA is cloverleaf; • MRNA does not have an amino acid binding site, tRNA does; • MRNA has more nucleotides • Different mRNAs have different lengths, all tRNAs are similar / same in length; • MRNA has codons, tRNA has anticodons;

Question 34

Describe how translation leads to production of a polypeptide

Answer 34

MRNA associates with a ribosome Ribosome moves to / finds the start codon; TRNA brings / carries the appropriate / specific amino acid; Anticodon on tRNA is complementary to the codon on mRNA Ribosome moves along to the next codon process repeated and amino acids joined using energy from ATP to form polypeptide.

Question 35

tRNA structure

Answer 35

In the cytoplasm are free amino acids and transfer RNA (tRNA) molecules In the cytoplasm are free amino acids Short single strand of RNA Folded into clover and held by H bonds At one end there’s a site where amino acids can bind to Other end threee unpaired bases = anticodons Only binds to specific amino acid Require energy from ATP

Question 36

Describe the structure of proteins.

Answer 36

primary structure is a) chain of amino acids/sequence of amino acids Secondary structure formed by interactions between amino and carboxyl groups and hydrogen bonds formed Tertiary structure is folding up of the polypeptide Stabilized by disulfide bridges/hydrogen/ionic bonds Quaternary is when more than 2 polypeptide subunits join Conjugated proteins combine with other nonproteins