protein structure & genes

Question 1

Describe how amino acids react together to form a polypeptide

Answer 1

2 amino acids join in a condensation reaction to form a dipeptide with a peptide bond forming between the 2 subunits this process is repeated to form polypeptide chains

Question 2

Give a definition of the primary structure of a protein

Answer 2

the sequence of amino acids in a polypeptide chain

Question 3

Describe how the secondary structure of a protein forms from the primary structure (make reference to alpha helix and beta pleated sheets)

Answer 3

chain twists and folds into 3D shape, may coil into alpha helices or come together into beta pleated sheets

Question 4

Describe how the tertiary structure of a protein forms from the secondary structure

Answer 4

folds ( know theres more to it but i cant find it anywhere)

Question 5

Explain how the primary structure of a protein determines the functional shape of the protein (typical 4 mark question)

Question 6

Describe the structure of a globular protein

Answer 6

polypeptide chain folded into a sperical shape

soluble due to hydrophilic side chains that project from the outside of the molecules

Question 7

Explain how the structure of a globular protein determines its function and properties
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Answer 7

their 3D shape is crucial to their ability to form enzyme substrate complexes and catalyse reactions within cells

Question 8

Describe the structure of a fibrous protein (incl. specific reference to collagen)

Answer 8

3 polypeptide chains wound round each other to form a rope like structure held together by H bonds

Question 9

Explain how the structure of a fibrous protein determines its function and properties

Answer 9

three polypeptide chains wound round each other and held together by hydrogen bonds and staggered strands makes fibrous proteins very strong, strength allows them to connect and protect tissues without breaking.

Question 10

1) Give the definition of a gene

Question 11

Questions for 2.13:
1) Define the following terms: Gene, Allele, Genotype, Phenotype, Recessive, Dominant, Incomplete dominance, Homozygote, Heterozygote

Answer 11

gene= a sequence of DNA bases that codes for a sequence of amino acids in a polypeptide chain
allele= alternative form of a gene found at the same locus
genotype=the combination of alleles in an individual
phenotype=characteristics caused by the genotype
recessive=only expressed in the phenotype if the individual is homozygous for the recessive allele
dominant=expressed in the phenotype if one of these alleles is present in the genotype
homozygote=an individual having 2 identical alleles of a particular gene
heterozygote=individual having 2 different alleles of a particular gene

Question 12

2) Using a genetic diagram, predict the genotype and phenotype outcomes of a cross between two parents who are heterozygous for Cystic Fibrosis

Answer 12

|F |f
————
F |FF|Ff 25% chance of suffering
———— CF, 50% chance of being
f |Ff|fF a carrier, 25% chance of
not being a carrier

Question 13

3) Using a genetic diagram, predict the genotype and phenotype outcomes of a cross between two parental plants that are heterozygous for flower colour (possible phenotypes are red, white and pink). Hint: this illustrates incomplete dominance.

Answer 13

100% chance of being pink? ( not too sure)

Question 14

4) Give the genotype of an individual who is a symptomless carrier of a recessive disease

Answer 14

heterozygous