1. Protein structure and function
Higher Human Biology
Sub topic 4 (a)

2. Learning Intentions Describe the different structures of proteins
Describe different functions of proteins
To discuss the effects of mutations in the code

4. Proteins are…. Made of the elements……. Long chains of amino acids.
Joined by peptide bonds.

5. The structure of the protein determines its function!!!!!!

6. PROTEIN PRIMARY STRUCTURE
The primary structure of a protein is the polypeptide chain of amino acids

7. PROTEIN SECONDARY STRUCTURE
Weak hydrogen bonds form between various amino acids.
This causes the polypeptide chain to become coiled into an  helix (coiled) or folded into a  pleated sheet (folded)

8. PROTEIN TERTIARY STRUCTURE
More links form between the polypeptides (hydrogen and sulphide bonds)
This forms fibrous proteins or globular proteins.

9. PROTEIN QUARTERNARY STRUCTURE
Quarternary structure is formed when several polypeptides become bonded together

10. Protein structure Proteins fall into two distinct groups:
Fibrous proteins
Globular proteins

11. FIBROUS PROTEIN
Formed when several polypeptide chains are bonded together in long parallel strands.
Long rope-like structure
e.g.
collagen (skin)
keratin (hair)
actin and myosin (muscle)

12. Collagen
Elastin
Actin and myosin
Keratin

13. GLOBULAR PROTEINS Look like a tangled ball of string.
Several chains folded into a ball
e.g.
Enzymes
Hormones
Antibodies

14. Growth Hormone
Prolactin

15. Glucagon
Insulin

16. Active site

17. CONJUGATED PROTEIN Contains polypeptide chains and a non- protein part
E.g.
haemoglobin consists of 4 polypeptide chains and 4 iron atoms

18. Conjugated proteins

19. Proteins with an attached carbohydrate
Glycoproteins
Proteins with an attached carbohydrate
e.g. Mucus.

20. Lipoproteins
Proteins with an attached lipid. The products of fat digestion are coated with lipoprotein before being transported.

23. What is a mutation?

24. How do mutations occur?
The Red Fox Ate The Pig The Fox Ate The Pig The Rd Fox Ate The Pig The Red Fox Ate The The Pig

25. Practical: At the end of your bench is a pot of sweets
At random select 1 from the pot
Round 1 Flu Epidemic
Colour
Mutation
Red
Able to fight off infection better
Orange
No mutation
Yellow
White
Less able to fight off infection
Green

26. Round 2 Intense sunshine and water shortage
Colour
Mutation
Red
No mutation
Orange
Prone to dehydration and sunstroke
Yellow
White
Green
Better able to store water and keep cool

27. Round 3 Heavy metal pollution
Colour
Mutation
Red
No mutation
Orange
Decreased tolerance to heavy metals
Yellow
White
Increased tolerance to heavy metals
Green

28. Round 4 Ebola epidemic Colour Mutation Red Ebola is always lethal
Orange
No mutation
Yellow
White
Green
Increased tolerance to ebola

29. Round 5 – Sickle cell anaemia
Colour
Mutation
Red
Sickle cell anaemia
Orange
Normal red blood cells
Yellow
White
Green

30. Mutations A mutation is a change to an individuals DNA.
There are 2 different types of mutation:
Gene mutation
Chromosome mutation.
Mutations are the only source of new variation.

31. They occur naturally and at random but are rare.
The mutation rate varies between genes and species.
Mutagenic agents can increase the frequency of mutation.
Some are advantageous, neutral or
lethal!

33. EXAMPLES Polydactyly – presence of extra finger or toes
Liam Gallagher and Marilyn Monroe!!

34. LIAM’S EXTRA TOE!

35. Gene Mutations
Changes in one or more nucleotides in the DNA of the cell giving a change in the base sequence.
3 types of POINT MUTATION:
SUBSTITUTION
INSERTION
DELETION
Some mutation are small and the protein isn’t changed.
Others results in different proteins or no protein at all.

36. Substitutions
Change in one nucleotide in the DNA sequence of a single gene.
This results in one or more codons for one or more amino acids being altered.

37. Substitution mRNA Protein Met Gln Thr Ser STOP mRNA Protein Met Gln

38. Substitution - Missense Mutation
Change in the codon for an amino acid so that a different amino acid is inserted into the protein.
An example of a disorder that results from a missense mutation is sickle cell anaemia.
This may or may not have an effect on the final protein

39. Sickle Cell Anaemia

40. Substitution - Nonsense Mutations
A codon for a specific amino acid being changed to a stop codon.
It causes protein synthesis to stop early and results in a shorter protein which is unable to function.
An example of this is Duchenne Muscular Distrophy

41. Splice-Site Mutations
This is where a mutation happens at a site where an intron is being spliced – the intron does not get spliced.
May cause non-functioning proteins.

42. Splice-Site Mutations
Intron
Exon
Normal splicing
Abnormal splicing
Normal functional haeomoglobin with 4 oxygen carrying subunits
Haeomoglobin with only 2 oxygen carrying subunits
Thalassemia, a disease caused by a defect in haemoglobin synthesis, is caused by a splice site mutation.

43. Nucleotide repeats
Where sections of the code are repeated (usually large copies of code are inserted.
Gives extra copies of an amino acid or if too many repeats then the gene is silenced.
Proteins are not always expressed but will be defective if they are.
Example – Huntington’s

45. Frameshift Mutations
Where the entire code is shifted affecting all amino acid codes after the point of mutation – large changes to the code
Protein formed will be non-functioning
Frameshift mutations can be:
Insertion
Deletion
Tay-sachs and cystic fibrosis

46. Frameshift - insertion
A nucleotide is added to the strand

47. Insertion mRNA Protein Met Gln Thr Ser STOP mRNA Protein Met Ala Asp
Ile
Leu

48. Frameshift - deletion
A nucleotide is removed from the strand

49. Deletion mRNA Protein Met Gln Thr Ser STOP mRNA Protein Met Gln His
Leu

50. Summary table Mutation Effect on the Protein Missense Nonsense
Depends on the proteins role
Nonsense
Shorter protein that won’t function
Splice - site
Non-functioning protein
Nucleotide Repeats
Defective if expressed
Frameshift
Non- functioning protein

51. Research Task – 300 words Create a fact sheet to show some information that you have gathered on one of the following : Sickle – cell Thalassemia PKU DMD Tay – sachs Cystic fibrosis Huntington’s Fragile – X Your fact sheet should contain info about the effects the condition has on the body and the type of mutation that causes it.

52. Chromosome Mutations
Chromosome structure mutations involve a change in the sequence or number of genes on a chromosome.
It is lethal
Examples are:
Deletion
Duplication
Translocation

53. Deletion
The chromosome breaks in 2 places and the segment in-between becomes detached.
The 2 ends then join up giving a shorter chromosome which lacks certain genes.
Drastic effect – e.g cri-du-chat

54. Duplication
When a segment of its homologous partner becomes attached at one end, or inserted somewhere along its length.
This results in a section of genes being repeated.
Common cause of cancer

55. Translocation
A section of one chromosome breaks off and becoming attached to another chromosome which is not its homologous partner.
This usually leads to problems during pairing up in meiosis and the gametes formed are often non-viable.
Common cause of cancer

56. Non-reciprocal translocation

57. Reciprocal translocation

58. Sickle Cell Videos Thalasessemia DMD Videos
anaemia.aspx?searchtype=Tag&searchterm=Conditions__Blood+diso rders&
DMD Videos
Documentary
Thalasessemia

59. Learning Intentions Describe the different structures of proteins
Describe different functions of proteins
To discuss the effects of mutations in the code

60. ESSAY TITLE Give an account of the replication of DNA
ESSAY TITLE Give an account of the replication of DNA. (maximum of 7 marks)

61. ANSWERS DNA is unwound and unzipped… …by the enzyme helicase…
…to form two template strands.
DNA polymerase is the enzyme which adds nucleotides to the new DNA strand.
DNA polymerase needs a primer to start replication.
DNA polymerase can only add complementary nucleotides to the deoxyribose / 3  end of the DNA strand.
This results in one strand / the leading strand being continuously replicated,
and the other strand / the lagging strand being replicated in fragments,
which are joined together (by the enzyme ligase).

62. ESSAY TITLE Give an account of gene expression under the following headings : Transcription (6 marks) Post-translational modification (PTM) (4 marks)

63. ANSWERS Transcription (maximum of 6 marks):
Transcription is the formation of a mRNA molecule on a DNA template.
DNA unwinds, and strands separate by the action of helicase.
RNA nucleotides attach to exposed bases of DNA.
DNA A pairs with RNA U, DNA T - RNA A, DNA G - RNA C and DNAC - RNA G.
RNA polymerase joins nucleotides (to each other).
This produces the primary transcript.
Which contains introns and exons.
Exons are protein coding sections of mRNA and introns are non-coding sections.
Post-translational modification (PTM) (maximum of 4 marks):
It takes place after the polypeptide has been completed on the ribosome.
It allows several proteins to be formed from one gene.
It may involve enzyme cutting and combining of polypeptide chains.
e.g. insulin from pro-insulin.
It may involve adding of phosphate or carbohydrate groups.
Addition of phosphate enables enzymes / receptors to be switched 'on' and 'off'.