2B Proteins and Genetics

Question 1

What are proteins made up of

Answer 1

amino acids

Question 2

structure of an amino acid

Answer 2

NH2CH(R)COOH

Question 3

Polypeptide formation: reaction and bond

Answer 3

condensation reaction
peptide bond

Question 4

Protein structure levels

Answer 4

Primary: sequence of amino acids
Secondary: alpha helix or beta pleated sheets as hydrogen bonds form
Tertiary: Bonds form between the R groups eg. disulfide, ionic causing it to coil more
Quaternary: Several polypeptide chains eld together

Question 5

Types of bonds at each protein structure level

Answer 5

primary: peptide
secondary: hydrogen
tertiary: ionic, disulfide (two cytosine) hydrophobic and hydrophilic interactions, hydrogen
quaternary: all of the above

Question 6

what will happen to protein structure and function if an amino acid is translated wrong

Answer 6

If the sequence of amino acids (primary structure) changes there will be different R groups forming additional or less bonds eg. a disulfide bond might form which changes the 3D structure of the protein, its properties and therefore its function

Question 7

Globular vs fibrous proteins

Answer 7

globular- round, compact with multiple polypeptide chains. hydrophobic parts on the inside hydrophilic outside, making them soluble

Fibrous- long insoluble chains coiled in a rope shape. the chains are held together by lots of bonds making them strong, so they are often found in supportive tissue.

Question 8

Enzymes properties

Answer 8

proteins which catalyse metabolic reactions
specific active site
can be intra or extracellular

Question 9

lock and key vs induced fit

Answer 9

lock and key- specificity to substrate allows the substrate to fit into the enzyme like a key fits a lock. the enzyme remains unchanged

induced fit- the enzyme changes shape slightly to lock the substrate in

Question 10

What is a mononucleotide made from

Answer 10

phosphate group
pentose sugar
organic base containing nitrogen

Question 11

DNA vs RNA: mononucleotide structure

Answer 11

DNA- deoxyribose sugar, ATCG
RNA-ribose sugar, AUCG

Question 12

polynucleotide bond and reaction

Answer 12

condensation reaction forms ester bonds between sugar and phosphate group

Question 13

Purine vs pyrimidine bases

Answer 13

purine- Adenine Guanine
pyrimidine- Cytosine Thymine Uracil

Question 14

Complementary base pairing

Answer 14

Adenine and thymine 2 hydrogen bonds
Cytosine and guanine 3 hydrogen bonds

Question 15

what is a triplet and what does it code for

Answer 15

a sequence of three bases in a gene which codes for one amino acid

Question 16

Characteristics of the genetic code and what they mean

Answer 16

Non-overlapping - each triplet is read separately from the triplet before and after it, they do not share bases
Degenerate- multiple triplets code for the same amino acid

Question 17

Transcription

Answer 17

RNA polymerase attaches at the start codon of the gene and breaks the hydrogen bonds, unwinding the DNA
RNA polymerase lines up free floating RNA mononucleotides complimentary to the template strand and joins them together to form mRNA
The process continues until a stop codon is reached.

Question 18

Translation

Answer 18

mRNA moves out of the nucleus via a nuclear pore and attaches to a ribosome.
tRNA with a complimentary anticodon to the start codon attaches. another tRNA molecule complimentary to the next codon attaches.
the amino acids attached are joined by a peptide bond and the empty tRNA moves away.
The ribosome moves along and the process repeats until there is a stop codon.