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MGD > Proteins > Flashcards

Proteins Flashcards

1
Q

What are the features of a peptide bond?

A

shorter than a normal single bond, rigid, planar, prevents free rotation and always in trans configuration

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2
Q

Is a peptide bond charged?

A

No but it is polar

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3
Q

Define a secondary structure

A

The regular arrangement of amino acids help together with hydrogen bonds

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4
Q

What are the features of an alpha helix?

A

tightly packed, coiled, side chains extend outwards, hydrogen bonds parallel to spiral, each turn contains 3.6 amino acids and a 0.54nm pitch.

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5
Q

Define tertiary structure

A

The folding of domains and the final arrangement of domains in the polypeptide

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6
Q

What is the only amino acid that doesn’t display stereoisomerism?

A

Glycine

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7
Q

What are the 2 types of spatial arrangement that an amino acid can take and which one is the only form naturally found?

A

2 arrangements: L-form and D-form

L-form is the only form found naturally

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8
Q

Define isoelectric point

A

The pH at which a protein has no overall net charge

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9
Q

What features do acidic proteins have?

A

contain many negatively charged amino acids and have a low pI

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10
Q

What features do basic proteins have?

A

contain many positively charged amino acids and have a high pI

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11
Q

Define homomeric proteins

A

When the polypeptide chains in the quaternary structure are identical

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12
Q

Define heteromeric proteins

A

When the polypeptide chains in the quaternary structure are different

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13
Q

Define denaturation

A

Loss of protein structure sufficient to cause the loss of function

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14
Q

Which amino acid does not contain a carboxyl group?

A

Proline

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15
Q

What value is physiological pH?

A

pH = 7.4

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16
Q

What is sickle cell anaemia?

A

A disease of the RBCs resulting from the substitution of glutamate for valine in the beta subunit of haemoglobin. (A->T)

17
Q

What is albumin?

A

A blood protein that functions as a transporter for a variety of molecules

18
Q

If a Ka value is higher what does this mean?

A

The larger the Ka value, the stronger the acid because most of the acid will dissociate.

19
Q

What is the Henderson-Hasselbach equation?

A

pH = pKa + log([A-]/[HA])

20
Q

How do you make a buffer?

A

By mixing a weak acid with its conjugate base

21
Q

If pH>pK the molecule is…

A

Deprotonated

22
Q

If the isoelectric point is greater than 7 then what kind of protein is it?

A

Basic protein

23
Q

If the isoelectric point is less than 7 then what kind of protein is it?

A

Acidic protein

24
Q

If the pH>pI then the molecule is…

A

Deprotonated

25
Q

What is a amphipathic molecule?

A

One that has both polar and non-polar regions

26
Q

What are some of the roles of proteins?

A

catalysts (enzymes), structural support, transporters, machines (contraction and motion), immune protection, receptors, ion channels and ligands in cell signalling

27
Q

Why are some R-groups positively charged?

A

Due to their high pKa value, they have acted as bases and accepted a proton.

28
Q

Why are some R-groups negatively charged?

A

Due to their low pKa values, they have acted as acids and donated a proton

29
Q

What are conjugated proteins?

A

Proteins that contain covalently linked chemical components in addition to amino acids.

30
Q

Why can’t we transport oxygen directly in the blood?

A

Oxygen isn’t very polar so does not dissolve in the aqueous environment of the blood.

31
Q

What are the features of myoglobin?

A

contains 1 haem group in the centre, comprised of 153 amino acids, compact and 75% alpha helical

32
Q

What are the features of haemoglobin?

A

comprised of 4 polypeptide chains, each chain contains a haem group and undergoes a structural change on binding oxygen

33
Q

What is the difference between the T state and R state of haemoglobin?

A

The T state has a low affinity for oxygen as this is before any oxygen has bound. The R state has a high affinity for oxygen as an oxygen molecule has bound and changed the structure so that the haem groups are more exposed and therefore can bind to oxygen more easily.

34
Q

What is the role of 2,3-bisphosphoglycerate?

A

This is a by product of glycolysis that causes the affinity of haemoglobin for oxygen to decrease. 1 BPG binds per tetramer and acts as a regulator by promoting oxygen release in the tissues.

35
Q

Define thalassaemias

A

A group of genetic disorders where there is an imbalance between the number of alpha and beta chains in haemoglobin.

36
Q

How many common amino acids are there?

A

20 common amino acids

37
Q

Define transition state

A

A high energy intermediate that lies between the reactants and products

38
Q

How does an increase in temperature increase the rate of reaction?

A

It increases the vibrational energy of the reactants. This increases the amount of molecules with the activation energy so more successful collisions will occur.

MGD (13 decks)

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