Mod 5: DNA & Polypeptide synthesis (CQ3)

Question 1

What are proteins?

Answer 1

Consist of building blocks called amino acids, linked together via peptide bonds

Question 2

What is the structure of Amino acids?

Answer 2

• R groups: Varies between amino acids (20 different R groups)
• Amino group
• Carboxyl group
• H atom

Question 3

What are the functions of proteins?

Answer 3

• Structural: Maintain cell shape and make our connective tissues
• Enzymes: Biological catalysts
• Hormones: Proteins secreted into blood by endocrine cells (glands)
• Immunity: Antibodies involved in immune response
• Contractile: Enable movement through contraction & relaxation of muscles
• Transport: Move substances around the body in the blood or lymph system
• Storage: Provide a source of food for embryos in animals that lay eggs

Question 4

What is the primary structure of a protein?

Answer 4

• Polypeptide chain -> Sequence of amino acids joined together by peptide bonds
• Sequence determined by genes, polypeptide produced by protein synthesis

Question 5

What is the secondary structure of a protein?

Answer 5

• Polypeptide chain gets folded into alpha helics and beta pleated sheets
• Folding made by H-bonds between carboxyl group and hydrogen of amino group

Question 6

What is the tertiary structure of a protein?

Answer 6

Occurs due to interactions between R-groups of amino acids. Many different types of bonds & interactions based on interactions of R-group

Question 7

What is a hydrophobic R-group?

Answer 7

Cluster inside protein

Question 8

What is a hydrophilic R-group?

Answer 8

Amino acid form outside

Question 9

What is a codon?

Answer 9

Set of 3 bases that code for 1 particular amino acid

Question 10

What are the stages of Protein Synthesis?

Answer 10

1. Transcription -> DNA to mRNA
2. Translation -> mRNA to protein

Question 11

What happens during Transcription in Protein Synthesis?

Answer 11

mRNA copy of a gene is made using DNA as template

Question 12

What is the process of Transcription in Protein Synthesis?

Answer 12

1. RNA polymerase attaches to DNA at desired gene and separates strands to expose nucleotide in that region
2. One strand use as template to make mRNA strand identical to other strand through complementary base pairings
3. Free floating nucleotide pair with their complementary bases on template strand
4. RNA polymerase reaches stop codon & lets go of DNA strand
5. In eukaryotes, introns spliced out of strand & exons are stuck together to form final mRNA strand
6. mRNA molecules leave the nucleus and enter cytoplasm through nuclear pore
7. Attaches to ribosome for translation

Question 13

What happens during Translation in Protein Synthesis?

Answer 13

• Nucleic acid is translated into protein
• Polypeptide chain is formed
• Anticodon: Triplet of bases that correspond to specific mRNA codon

Question 14

What is the process of Translation in Protein Synthesis?

Answer 14

1. mRNA attaches to a ribosome at a particular start codon
2. tRNA molecule with correct anticodon pairs up with mRNA in the ribosome
3. Second tRNA molecule attaches to the next codon on the mRNA strand
4. Ribosome catalyses the formation of a peptide bond between 2 amino acids
5. Ribosome continues to move along the mRNA until it reaches a stop codon
6. Polypeptide chain and mRNA strand are released from the ribosome

Question 15

What is epigenetics?

Answer 15

How an individual’s behaviour and environment cause changes in the way genes are expressed. How environment can influence phenotype