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Science for Medicine > Proteins 2 > Flashcards

Proteins 2 Flashcards

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1
Q

Name 3 types of proteins which contain prosthetic groups?

A

Glycoproteins
Lipoproteins
Metalloproteins

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2
Q

What is a glycoprotein?

A

Compound composed of protein and carbohydrate

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3
Q

How are glycoproteins formed?

A

Post-translational modification (glycosylation) whereby a sugar molecule binds via an amino acid to the protein

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4
Q

What are examples of glycoproteins?

A

Immunoglobulins

Blood group determinants

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5
Q

Where does glycosylation occur?

A

ER and Golgi body

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6
Q

What does glycosylation play a role in?

A
  • Protein stabilisation
  • Affects solubility
  • Protein orientation
  • Signalling
  • Cell recognition
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7
Q

How can glycoproteins be used in disease?

A

Provides a marker of long term diabetic control

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8
Q

How are glycoproteins used in diabetes?

A
  • Non-enzymatic reaction forms glycated haemoglobin
  • Condensation reaction between N-terminal valine and glucose forms aldimine
  • Aldimine undergoes amadori rearrangement to from stable ketoamine
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9
Q

What are lipoproteins?

A

Proteins and lipids bonded together either covalently or non-covalently?

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10
Q

What is the function of lipoproteins?

A

To transport water-insoluble fats and cholesterol in the blood e.g. HDL, LDL

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11
Q

What are metalloproteins?

A

Protein molecules with a bound metal ion

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12
Q

What are the functions of metalloproteins?

A

Enzymes
Transport
Storage
Signalling

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13
Q

What functions can proteins have?

A
  • Movement
  • Enzymes
  • Structural
  • Protection
  • Receptors
  • Storage
  • Hormones
  • Transport
  • Control of gene expression
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14
Q

What functions do globular proteins have?

A

Varied functions:

  • Enzymes
  • Hormones
  • Transporters
  • Stock of amino acids
  • Structural function (actin and tubulin)
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15
Q

What functions do fibrous proteins have?

A

Structural function:

  • Bone matrixes
  • Muscle fibres
  • Tendons
  • Connective tissue
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16
Q

What functions do membranous proteins have?

A

Associated with cell/organelle membrane:

  • Relay signals
  • Membrane transporters
  • Membrane enzymes
  • Cell adhesion molecule
17
Q

What is the binding ratio of haemoglobin to oxygen?

A

Haem group at the centre of each polypeptide chain binds one molecule of oxygen. One molecule of haemoglobin can bind four molecules of oxygen

18
Q

Co-operativity

A

The increase in affinity of polypeptide chains when a substance binds to a sister polypeptide chain

19
Q

What is the genetics behind sickle cell anaemia?

A

Single base change causes hydrophilic amino acid glutamic acid to be replace with hydrophobic valine

20
Q

What are the properties of Hb S?

A
  • Insoluble

- At low O2 levels it forms crystals and polymerises to form long chains, causing the RBC to change shape

21
Q

What are the clinical features of Hb S?

A
  • Sever haemolytic anaemia

- Hb S gives up oxygen in the tissues more easily than Hb A.

22
Q

What is collagen?

A
  • Fibrous protein that makes up 25% of the total protein in humans
  • High tensile strength
23
Q

What is collagen composed of?

A

Repeating unit Glycine-X-proline where X is alanine, hydroxyproline, lysine

24
Q

What is the structure of collagen like?

A
  • Polypeptide chain coils to form a helix
  • 3 polypeptides then coil around each other
  • They are held together by hydrogen bonds which can interact to form fibrils increasing the strength
25
Q

What is vitamin C required for?

A

To convert proline to hydroxyproline and lysine to hydroxylysine.

26
Q

What happens when someone is deficient in vitamin C?

A

Scurvy:

  • Hydroxylysine and hydroxyproline are essential for stabilising the crosslinks between chains
  • Weaker collagen is produced
27
Q

Why does oesteogenesis imperfect occur?

A
  • Glycine substituted for a larger amino acid
  • Protein unable to form tight coil
  • Reduced fibril interaction
  • Loss of secondary, tertiary structure
  • Weakened and brittle collagen produced
28
Q

What is an LDL receptor?

A

A glycoprotein present on the surface of all cells which binds to apoB and causes the internalisation of LDL.

29
Q

What are the classes of mutations relating to the LDL receptor?

A
  • Class 1: no receptors produced
  • Class 2: Receptors never reach cell surface
  • Class 3: Receptors can’t bind LDL
  • Class 4: Receptors don’t internalise on binding LDL
  • Class 5: Receptors don’t release LDL
30
Q

What is Familial Hypercholesterolemia?

A

An autosomal dominant disorder caused by mutations in LDL receptor

31
Q

What does FH cause?

A

Elevate LDL concentrations in the blood which leads to cholesterol deposits in the skin, tendons and arteries and as a result early CV disease

Science for Medicine (50 decks)

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