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semester 1 > Proteins > Flashcards

Proteins Flashcards

1
Q

What is released when a peptide bond is formed?

A

Water

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2
Q

What is the primary structure of a protein

A

The sequence of amino acids

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3
Q

What is the secondary structure of a protein?

A

The spatial arrangement of amino acid residues that are near each other in the linear sequence

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4
Q

What are the two structural forms of the secondary structure?

A

Alpha helix, beta sheets

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5
Q

What stabilises the alpha helix structure?

A

H bonds between the NH groups and the CO groups in the next turn of the helix

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6
Q

What stabilises the beta sheets?

A

H bonds between the amide groups of the linear polypeptide chains

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7
Q

What is the tertiary structure?

A

The spatial arrangements of amino acids residues that are far apart in the linear sequence

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8
Q

What is the tertiary structure held together by?

A

Van der waals forces
Ionic interactions
Hydrogen bonds
Disulphide bridges
Hydrophobic interactions

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9
Q

Where do ionic interactions take place?

A

Between two oppositely charged R groups

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10
Q

What environment is needed for intra polypeptide hydrophobic interactions to occur?

A

An environment within proteins from which water is excluded

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11
Q

Where do disulphide bridges occur?

A

They are strong covalent bonds that occur between two cysteine residues
They are common in extra-cellular proteins
They can occur between as well as within a polypeptide

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12
Q

What is the quaternary structure?

A

The spatial arrangement of individual polypeptide chains in a multi-subunit protein

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13
Q

What structure remains in tact after denaturation?

A

The primary structure

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14
Q

What are common causes of denaturation?

A

Acids
Heat
Solvents (ethanol)
Cross linking reagents (formaldehyde)
Chaotropic agents (urea)
Disulphide bond reducers (2 mercaptoehanol)

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15
Q

What is the effect of denaturation?

A

Decrease in solubility
Altered water binding capacity
Loss of biological activity
Improved digestibility

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16
Q

What is glycosylation?

A

Post translational modification whereby a sugar molecule binds via an amino acid to the protein

17
Q

Give an example of a glycoprotein

A

Immunoglobulins

18
Q

Where does glycosylation occur?

A

In the ER and the golgi apparatus

19
Q

What is the roles of glycosylation?

A

Protein stabilisation
Affects solubility
Protein orientation
Signalling
Cell recognition

20
Q

What is the function of lipoproteins?

A

Transport of water, insoluble fats and cholesterol in the blood

21
Q

What are metalloproteins?

A

Protein molecule with a bound metal ion

22
Q

What are the functions of metalloproteins?

A

Enzymes
Storage
Signalling
Transport

23
Q

Why does haemoglobin have four subunits?

A

The binding of O2 to one sub unit alters its shape
This in turn causes a change in shape of the other sub-units so that they bind O2 more easily

Co-operative binding

24
Q

How does sickle cell anaemia arise?

A

Substitution of one amino acid, hydrophilic Glutamic acid is replaced with hydrophobic amino acid Valine

25
Q

What are the clinical features of sickle cell anaemia?

A

Severe haemolytic anaemia
Oxygen is given up more easily in the tissues

26
Q

What is the structure of collagen?

A

Polypeptides coil to form a helix

Held together by hydrogen bonds
Interactions form fibrils which increases strength

27
Q

What is the effect of scurvy?

A

Vitamin C deficiency, there is less hydroxyproline and hydroxylysine which are essential in stabilising cross links between chains of collagen, so collagen produced is weaker

28
Q

What is the effect of osteogenesis imperfecta?

A

Protein cannot form into a tight coil due to amino acid substitution

There is less interaction between fibrils

Loss of secondary and tertiary structure

Weakened and brittle collagen is produced

29
Q

What are the possible mutations of the LDL receptor?

A

No receptors produced
Receptors never reach cell surface
Receptors can’t bind LDL
Receptors don’t internalise on binding LDL
Receptors don’t release LDL

30
Q

What disease can result as an effect of LDL mutation?

A

Familial hypercholesterolemia, resulting in early cardiovascular disease

semester 1 (105 decks)

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