Protein
Synthesis
Unit 1
Sub-topic 1
Cell Function and Inheritance
Protein Structure and Function
Thousands of different proteins exist in living organisms, all with different roles to play, and
all vital for a fully functioning organism.
1 a) (i) Give the symbols of the four chemical elements always present in the amino acids that
make up a protein.
(ii) Approximately how many different types of amino acid are found in proteins?
b) (i) Identify the type of bonds that join amino acids into the polypeptide chain primary
structure.
(ii) Which type of bonds give the further linkages that produce secondary and tertiary
structures?
(iii) Label this polypeptide chain to indicate amino acids, peptide bonds and hydrogen bonds.
c) What is meant by the following terms with regard to protein structure:

primary structure
2


secondary structure
tertiary structure
3
d) (i) Name the three different types of proteins
(ii) Identify and label these diagrams of the 3 different types of proteins and add a
description of the arrangement of polypeptide chains in each.
non-protein part
4
2 a)(i) Actin and myosin are examples of fibrous proteins. Label which is which on the diagram
and identify the different bands.
(ii) How do actin and myosin bring about muscle contraction?
b) Complete the following table.
Name of
protein
Type of protein
(fibrous, globular or
conjugated)
antibodies
catalase
cytochrome
haemoglobin
insulin
keratin
transferrin
5
Role of this protein
Part 2
Nucleic acids and protein synthesis
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are both nucleic acids. The genetic
information carried on DNA is actually a molecular code for the production of all the
different types of protein that exist. RNA is a molecule that helps translate the code into
protein.
Structure of DNA
1 a) What name is given to each of the repeating units that make up a strand of DNA?
b) How many strands are present in a molecule of DNA?
2 a) Label the diagram with the THREE parts of a DNA nucleotide.
b) (i) Complete the diagram to show a strand of 5 nucleotides joined together.
(ii) Which type of bond joins the nucleotides into a strand of DNA?
Label this on your diagram.
6
c) (i) Name the four types of base molecule found in DNA and give the base-pairing rule.
(ii) Complete the complementary strand for this section of DNA.
A
G
T
C
d) What type of bond forms between the bases of adjacent strands of a DNA molecule?
3 a) What name is given to the twisted coil arrangement typical of a DNA molecule?
b) If DNA is like a spiral ladder, which part of it corresponds to the ladder’s: (i) rungs
(ii) uprights
c) Complete the diagram to include 2 more nucleotides (thymine and cytosine) on this strand,
and then add the complementary strand connected to these. Label the 2 types of bonds.
A
G
C
7
Structure of RNA
1 a) Label the diagram of an RNA nucleotide.
b) Name the 4 bases of RNA
c) State THREE ways in which RNA and DNA differ in structure and chemical composition.
1:
2:
3:
d) Draw a strand of RNA
2. What is: -
mRNA
tRNA
8
Sequence of bases
1 What has DNA of different species got in common?
2 In what 2 ways does the DNA of one species differ from that of another, which makes
each species unique?
1:
2:
3 What 2 things control an organisms inherited characteristics?
4 a) What do an enzyme’s structure, shape and ability to carry out its function all depend on?
b) Why?
5) What determines the sequence of amino acids in a polypeptide chain?
4a) With reference to the relationship between the genetic code and the protein synthesised
why is it not possible that
(i) one base corresponds to one amino acid?
(ii) two bases correspond to one amino acid?
9
b) How many bases in the genetic code do correspond to one amino acid?
c) What name is given to the groups of bases that make up the genetic code?
Protein Synthesis
Step 1 Transcription
1. a) What is transcription?
b) What is the role of mRNA?
2 Study the picture and then answer the following
questions
a) What is happening at stage 1?
b) What type of bond is breaking at stage 2?
DNA strand
being transcribed
10
c) (i) Complete the table to show which RNA base
pairs up with which DNA base at stage 3?
DNA base
Complementary
RNA base
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
b) Name the type of bond formed and the types of
molecule involved during: (i) stage 4
(ii) stage 5
c) What happens to a molecule of transcribed mRNA?
d) What happens to the DNA strand after transcription?
Step 2 Translation
1 a) What is translation?
b) Where is tRNA found and roughly how many types are there?
11
2 a) What name is given to a triplet of bases on a molecule of
i) mRNA
ii) tRNA
b) What type of molecule does each tRNA triplet correspond to?
3 a) What is the function of ribosomes?
b) Label this diagram of translation
with the following words: 





mRNA
tRNA
codon
anticodon
ribosome
amino acid
c) What type of bond forms between adjacent amino acids brought together by their tRNA
at a ribosome?
d) What is formed as the ribosome continues to move along the mRNA molecule?
4. Describe the role of the nucleolus in protein synthesis.
12
5. The picture shows the whole process of protein synthesis. The table gives some of the
triplets which correspond to certain amino acids.
a) Identify bases 1-9.
b) Label process P and Q.
c) (i) Where does process P occur?
(ii) Where does process Q occur?
d) Complete the table.
amino acid
alanine
arginine
cysteine
glutamic acid
glutamine
glycine
isoleucine
leucine
proline
threonine
tyrosine
valine
Codon (mRNA)
Anticodon (tRNA)
CGC
CGC
ACA
GAA
GUU
GGC
UAU
CUU
GGC
ACA
AUA
GUU
d) Use your table to rewrite the amino acid chain U, V, W, X, Y and Z.
13
After synthesis – processing and secretion
1 a) What is the difference between a protein synthesised on free ribosomes from those
made on ribosomes attached to the rough endoplasmic reticulum?
b) Note the roles of the rough endoplasmic reticulum and Golgi apparatus in the
processing of a newly formed protein.
This picture shows part of a hugely magnified secretory cell. You should be able to identify
the different organelles.
c) Annotate the diagram to summarise the synthesis and packaging of new proteins.
14