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Semester 1-MCBG > Session 5-Protein Structure And Function > Flashcards

Session 5-Protein Structure And Function Flashcards

1
Q

Give examples of biological processes for which proteins are needed

A

Catalysts (enzymes)
Transporters (eg O2, Fe)
Structural support (eg collagens)
Machines (eg muscular contraction and motion)
Immune protection (eg immunoglobulins)
Ion channels
Receptors (for hormones, neurotransmitters etc)
Ligand in cell signalling (growth factors etc)

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2
Q

What is a peptide bond formation?

A

The linking of two AA accompanied by the removal of a molecule of water

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3
Q

What is the primary structure of a protein?

A

Linear AA sequence of the polypeptide chain

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4
Q

What is the secondary structure of a protein?

A

Folding of AA chain, stabilised by H bonds, alpha helix and beta pleated sheet

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5
Q

What is the tertiary structure of a protein?

A

Extensive coiling and folding of AA chain with hydrophobic side chain folded inside (3D configuration)

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6
Q

What is the quaternary structure of a protein?

A

Two or more polypeptide chains to form multi-subunit protein (eg Hb with 4 chains)

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7
Q

True or false: peptide bonds are planar so the alpha C, C, O, N, H all lie in the same plane?

A

TRUE

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8
Q

True or false: peptide bonds are rigid?

A

TRUE

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9
Q

What is the isoelectric point (pI) of a protein?

A

pH at which there is no overall net charge

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10
Q

What is the pI of basic proteins?

A

> 7

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11
Q

What is the pI of acidic proteins?

A

<7

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12
Q

What happens if the pH>pI?

A

Protein is deprotonated

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13
Q

What is the difference between peptides/oligopeptides and polypeptides/proteins?

A

Peptides/oligopeptides are only a few AA in length whereas polypeptides/proteins are many AA in length

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14
Q

What is a conjugated protein?

A

A protein that contains covalently linked chemical components in addition to AA

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15
Q

Give two examples of conjugated proteins

A

Lipoproteins

Glycoproteins

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16
Q

Which small hydrophobic resides are strong alpha helix formers?

A

Alanine and leucine

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17
Q

Why does proline act as a helix breaker?

A

The rotation around the N-C bond is impossible

18
Q

Why does glycine act as a helix breaker?

A

The tiny R-group supports other conformations

19
Q

True or false: the alpha helix is a left-handed helix

A

FALSE - it is right-handed

20
Q

What is an antiparallel beta sheet?

A

Adjacent beta strands run in opposite directions with multiple interstrand H bonds stabilising the structure

21
Q

What are the roles of fibrous proteins? (3)

A

Support
Shape
Protect

22
Q

What are the roles of globular proteins? (2)

A

Catalysis

Regulation

23
Q

True or false: fibrous proteins consist of a single type of repeating secondary structure

A

TRUE

24
Q

Give an example of fibrous proteins

A

Collagen

25
Q

Complete the sentence:

Collagen is a ______ helical arrangement of collagen chains

A

Triple

26
Q

Which AA is present in this repeating sequence in collagen: AA - X - Y?

A

Glycine

27
Q

What is domain in a tertiary structure of a protein?

A

Part of the polypeptide chain that folds into a distinct shape and often has a specific functional role

28
Q

Which force is involved in maintaining the primary structure of a protein?

A

Peptide (covalent)

29
Q

Which force is involved in maintaining the secondary protein structure?

A

H-bonds

30
Q

Which forces are involved in maintaining the tertiary and quaternary protein structures?

A 
Peptide
Ionic
H-bonds
Van der Waals
Hydrophobic 
Disulphide
31
Q

Between which AAs do disulphide bonds form?

A

Between cysteine residues

32
Q

True or false: the interaction between hydrophobic side chains due to the displacement of water is called hydrophobic interaction, not hydrophobic bond

A

TRUE

33
Q

Complete the sentence:

A normally folded protein that is functional is said to be in its ______ conformation

A

Native

34
Q

The disruption of protein structure is known as?

A

Denaturation

35
Q

How does heat cause denaturation?

A

Increased vibrational energy

36
Q

How does incorrect pH lead to denaturation?

A

Alters the ionisation states of AA and changes ionic/H bonds

37
Q

How do detergents lead to denaturation?

A

Disrupt hydrophobic interactions

38
Q

True or false: folding of proteins is random

A

FALSE - it would take too long if folding was random therefore it is ordered and driven by entropy (in order to find most stable conformation)

39
Q

How can protein misfolding cause disease?

A

Altered conformation of normal human protein promotes conversion of existing protein into diseased state

40
Q

Give examples of diseases caused by protein misfolding

A

Transmissible spongiform encephalopathies eg BSE, kuru and CJD

Semester 1-MCBG (20 decks)

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