chapter one: the relationship between nucleic acids and proteins

Question 1

2 monomers of a nucleic acid

Answer 1

deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

Question 2

state the base pairing rules

Answer 2

DNA:

• Adenine and Thymine
• Guanine and Cytosine

RNA

• Adenine and Uracil
• Guanine and Cytosine

Question 3

compare DNA and RNA

Answer 3

similarities:

• DNA and RNA are both made up of nucleotide monomers, which contain phosphate, a sugar and a nitrogenous base

differences:

• DNA contains thymine as a base instead of uracil
• DNA is double stranded and RNA is single stranded
• DNA is located in the nucleus whilst RNA is everywhere
• DNA has a function of instructing and RNA makes proteins

Question 4

eukaryotic genes features

Answer 4

consists of a coding region and flanking regions

• coding regions: part of a gene that contains the coded information for making a protein —> within the coding regions, it contains exons and introns
• exons contain the instructions for the synthesis of the protein and are both transcribed and translated —> they provide the instructions that code for the amino acids in the produced protein
• introns are sections that are no expressed
• flanking regions: in the upstream and downstream of a gene

Question 5

define gene regulation

Answer 5

gene regulation is when genes are regulated to keep them from producing but not overflood the cell with that gene.

• the process of turning genes on and off

Question 6

compare structural and regulatory genes

Answer 6

structural genes:

• codes for proteins that become part of the structure or function of cells

regulatory genes:

• code for proteins that control the expression of other genes -> their actions determine whether other genes are turned on or off

Question 7

outline how the trp operon works

Answer 7

presense of trp:

• trp binds to the repressor protein causing a configurational change in its shape → allows it to be active
• enables the repressor to bind to the operator
• RNA polymerase is unable to bind to the promoter and transcription does not occur
• operon is turned off
• trp isn’t made

absence of trp:

• repressor is unable to bind to the operator (in an inactive form)
• rna polymerase can bind to the promoter and start transcription of the structural genes
• operon is on
• trp can be made

Question 8

define the proteome

Answer 8

the complete array of proteins produced by a single cell or an organism in a particular environment

Question 9

describe condensation polymerisation

Answer 9

• the process of joining amino acids together
• condensation → water/smaller
• polymerisation → making a polymer
• amino acids join using energy and water is released
• carboxyl groups bind with the amino group
• OH of carboxyl group joins w/ H of the amino group to form water

Question 10

define polymer

• state 2 molecules fond in living things that are polymers

Answer 10

polymers are what makes up amino acids which makes proteins

• a large substance made up of smaller subunits

Question 11

describe the 4 levels of protein structure

Answer 11

primary:

• A linear sequence of amino acids linked together called a polypeptide chain
• NOT FUNCTIONAL

secondary:

• consists of alpha helices, beta pleated sheets and random coils
• the folding and coiling is caused by interactions of the R-group

tertiary:

• A irregular 3D folding held together by ionic or hydrogen bonds forming a complex shape
• A FUNCTIONAL STRUCTURE

quaternary:

• bonding of two or more polypeptide chain

Question 12

explain why the shape of a protein is important to its function

Answer 12

• allows it to have a specific function in a cell or body structure to interact with other molecules

Question 13

summaries nucleus

Answer 13

codes for the proteins (makes mRNA) which goes to the ribosome on the rough endoplasmic reticulum

Question 14

summaries rough endoplasmic reticulum

Answer 14

the ribosome uses the mRNA code to make a protein, which is then folded and modifies in the rough endoplasmic reticulum

Question 15

summaries transport vesicle

Answer 15

the proteins are placed into a transport vesicle and then moves to the golgi apparatus

Question 16

summaries golgi apparatus

Answer 16

the proteins undergo further modification before being packages into a secretory vesicle

Question 17

summaries secretory vesicles

Answer 17

exports the proteins out of the cell (at the cell membrane via exocytosis)

Question 18

summarise plasma membrane

Answer 18

the membrane found in all cells that separates the interior of the cell from the outside environment

• the secretory vesicles move to the plasma membrane and expel its contents through exocytosis

Question 19

describe the 3 forms of RNA

Answer 19

mRNA

• messenger RNA
• carries genetic message from DNA in the nucleus to ribosomes
• involved in transcription and translation

tRNA

• transfer RNA
• carry SPECIFIC amino acids to ribosomes to be used to construct proteins

rRNA

• ribosomal RNA
• works with other proteins to make ribosomes in cytosol
  Subunits that allow for the interaction of mRNA and tRNA. Allows for the growing peptide chain to be created.

Question 20

DNA code is…

Answer 20

is universal and redundant

universal:

• essentially the same across all organisms - bacteria, plants, animal

redundant:

• different triplets of bases can code for the same amino acid

Question 21

RNA processing

Answer 21

• turns pre-mRNA to mRNA
• capping of the 5’ end with a methyl cap
• addition of a poly-A tail on the 3’ end
• introns are removed and exons are spliced together

Question 22

define operon and operator

Answer 22

operon

• related genes found in a cluster on a chromosome, under the control of a single promoter

operator:

• short DNA segment found between promoter and gene to be transcribed

Question 23

attenuation

Answer 23

Attenuation –prevents the completion of
transcription.

• levels of tryptophan are high, attenuation causes RNA polymerase to stop prematurely when it’s transcribing the trp operon resulting in a shortened mRNA
• Specific coding in the attenuator regions allows
  sections known as hairpin loops to form when they are
  transcribed to mRNA

Question 24

difference between exocytosis and endocytosis

Answer 24

• endocytosis involves taking in a substance from outside the cell by engulfing them in a vesicle derived from the cell membrane
• exocytosis is where cells shift materials, such as waste products, from inside the cell to the extracellular space

Question 25

how can the same gene code for different proteins

Answer 25

the transcript of many eukaryotic genes are splices in a variety of different ways to produce a set of different mRNAs

Question 26

steps in transcription

Answer 26

1. DNA in the nucleus
2. That DNA is unzipped and read by RNA polymerase
3. The polymerase will create a complementary strand (however in MRNA T is replaced WITH U) (THYMINE IS REPLACED BY URACIL)
4. The strand is called a pre-mature mRNA with exons and introns
5. A method called excising is used to cut the mRNA sequence to remove introns and splicing is used to glue the exons together
6. A metal cap and tail (‘5 is the cap and ‘3 is the tail) are placed onto the corresponding ends of the now-matured mRNA

Question 27

steps in translation

Answer 27

1. The strand is exported to ribosomes in the rough endoplasmic reticulum
2. Once it is there, a ribosome made up of rRNA will attach to the matured mRNA
3. From there, the mRNA will be read by the ribosomes
4. They are read in groups of three also called codons
5. tRNA is free-floating and carries amino acids on the top
6. Once read, the complementary anticodon will dock and release the amino acid to form a polypeptide chain

Question 28

how can the same gene code for different proteins

Answer 28

• exon shuffling
• alternate folding
• golgi modification