1.2 PROTEINS Flashcards

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1
Q

What is the Genome?

A

An organism’s complete set of DNA

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2
Q

What is the Proteome?

A

The entire set of proteins expressed by a genome.

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3
Q

Why is the Proteome larger than the Genome?

A

Due to alternative RNA splicing and post-translational modification

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4
Q

What is the result of Gene Expression?

A

Not all genes are expressed as proteins in a particular cell

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5
Q

What is the benefit of Gene Expression?

A

Only essential proteins are produced and therefore the cell is more energy and resource efficient

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6
Q

What does amino acid sequence determine?

A

Protein structure

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7
Q

What is a protein?

A

A polymer of amino acid monomers

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8
Q

Which type of bond links amino acids?

A

Peptide bonds

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9
Q

What is a chain of amino acids called?

A

Polypeptide

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10
Q

What are the four types of protein structure?

A

Primary, Secondary, Tertiary and Quaternary

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11
Q

What is the primary structure of a protein?

A

The sequence in which the amino acids are synthesised into a polypeptide

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12
Q

What is the secondary structure of a protein?

A

Alpha helices / Beta sheets / Turns

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13
Q

What causes secondary structure?

A

Hydrogen bonding along the backbone of the protein

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14
Q

What is the tertiary structure of a protein?

A

3D folding of the polypeptide

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15
Q

What causes tertiary structure?

A

Bonding - interactions between R groups, hydrophobic/hydrophilic interactions, ionic bonds, van der Walls interactions, disulfide bridges

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16
Q

What is an R group?

A

Functional group attached to the amino and carboxyl group compound (other component of amino acids). They are the only thing which distinguishes the 20 different amino acids.

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17
Q

What affects R group interactions?

A

Temperature and PH

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18
Q

Other than folding, what else is included in tertiary structure?

A

Prosthetic groups

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19
Q

What are prosthetic groups?

A

Non-protein unit bound to a protein which is essential for protein function

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20
Q

What is the quaternary structure of a protein?

A

Consisting of several connected polypeptide sub-units

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21
Q

What influences the location of proteins in cells?

A

Hydrophobic and Hydrophilic Interactions

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22
Q

What determines the location of proteins in a cell?

A

R groups at the surface of the proteins

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23
Q

What is a soluble protein?

A

A protein found in the cytoplasm

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24
Q

What do Hydrophilic R groups in soluble proteins do?

A

The R groups predominate at the suface of the protein

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25
Q

What does predominate mean?

A

To become the strongest or main element; greater in number

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26
Q

What do Hydrophobic R groups in soluble proteins do?

A

The R groups may cluster at the centre to form a globular structure

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27
Q

What is the name of membrane model we study?

A

Fluid mosiac model

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28
Q

What are the two types of membrane protein?

A

Integral and peripheral

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29
Q

Give an example of an integral membrane protein.

A

Transmembrane protein (eg. Channel, transporter, receptor)

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30
Q

What holds integral proteins within the phospholipid bilayer?

A

Strong hydrophobic reactions caused by regions of hydrophobic R groups

31
Q

What is the difference between the R groups in peripheral and integral proteins?

A

Peripheral proteins have fewer hydrphobic R groups interacting with the phospholipids compared to integral proteins

32
Q

What is a ligand?

A

A substance which can bind to a protein

33
Q

What allows proteins to bind to ligands?

A

R groups NOT involved in protein folding can allow binding

34
Q

What must ligand-binding sites have?

A

A complementary shape and chemistry to the ligand

35
Q

What can DNA bind to?

A

A number of proteins

36
Q

How does DNA bind to histone proteins?

A

Positively charged histone proteins bind to negatively charged sugar-phosphate DNA backbone in eukaryotic cells

37
Q

What is the benefit of DNA binding to histone proteins?

A

DNA wraps around histones forming nucleosomes which pack the DNA in chromosomes

38
Q

What do nucleosomes do?

A

They pack DNA in chromosomes

39
Q

How do proteins (other than histones) bind to DNA?

A

They have binding sites specific to particular sequences of double-stranded DNA

40
Q

What can proteins (other than histones) do when bound to DNA?

A

Stimulate or inhibit transcription

41
Q

What is the result of a ligand binding to a protein?

A

Conformational change of protein

42
Q

What is the result of a substrate binding to an enzyme’s active site?

A

Conformational change of enzyme (protein)

43
Q

What is the result of a conformational change of a protein?

A

Functional change

44
Q

What is induced fit?

A

A temporary change in the shape of an enzyme’s active site

45
Q

What causes induced fit?

A

Correct substrate begins to bind to enzyme’s active site

46
Q

What is the result of induced fit?

A

Increases the binding and interaction of the enzyme with the substrate

47
Q

What is activation energy?

A

The minimum quantity of energy required in order to undergo a particular reaction

48
Q

How do enzymes lower activation energy?

A

The chemical environment lowers the activation energy required

49
Q

What happens after catalysis?

A

The original enzyme conformation is resumed and products are released from active site

50
Q

What is an allosteric enzyme?

A

An enzyme which changes its conformation upon the binding of a modulator to a secondary binding site

51
Q

What are the two types of modulators?

A

Positive and negative

52
Q

What is the result of a modulator binding to an allosteric enzyme?

A

Conformational change of enzyme, altering affinity of active site for the substrate

53
Q

What is the result of a positive modulator binding to an allosteric enzyme?

A

Increases enzyme’s affintiy for substrate

54
Q

What is the result of a negative modulator binding to an allosteric enzyme?

A

Reduces enzyme’s affintiy for substrate

55
Q

What is cooperativity?

A

When the binding of a ligand at one site influences binding at a second site

56
Q

Which type of proteins does cooperativity affect?

A

Proteins with quaternary structure

57
Q

What is the result of cooperativity in proteins with quaternary structure?

A

Binding at one subunit alters the affinity of the remaining subunits

58
Q

What is the result of a haemoglobin subunit binding to a molecule of oxygen?

A

The second subunit binds more easily, the third even more and the fourth easier still

59
Q

What is the result of an oxy-haemoglobin subunit releasing its oxygen?

A

The second subunit is more likely to release its oxygen and so on.

60
Q

Which factors affect haemoglobin’s ability to bind to oxygen?

A

Temperature and pH

61
Q

How does temperature affect haemoglobin’s ability to bind to oxygen?

A

As temperature increases, affinity for oxygen decreases

62
Q

How does pH affect haemoglobin’s ability to bind to oxygen?

A

As pH decreases, affinity for oxygen also decreases

63
Q

What can be used to cause a reversible conformational change in a protein?

A

The addition or removal of phosphate from particular R groups

64
Q

What is the addition/removal of phosphate from particular R groups a common form of?

A

Post-translational modification

65
Q

What is the benefit of a reversible conformational change?

A

Allows activity of cellular proteins to be regulated

66
Q

What is a kinase enzyme?

A

An enzyme which catalyses the transfer of a phosphate group from ATP to another molecule

67
Q

What are kinases responsible for?

A

Phosphorylation of other proteins

68
Q

What are phosphatases responsible for?

A

They catalyse dephosphorylation

69
Q

What are ATPases responsible for?

A

Using ATP to catalyse their own phosphorylation

70
Q

What is myosin?

A

A fibrous protein which forms the contractile filaments of muscle cells

71
Q

What is myosin responsible for?

A

Muscle contraction

72
Q

What happens when ATP binds to myosin?

A

Myosin head detaches from actin, swings forwards and rebinds

73
Q

What is the result of myosin rebinding?

A

ADP and a phosphate ion is released, dragging the myosisn along the actin filament

74
Q

What are the four classes of R groups?

A

Acidic (Negative), Basic (Positive), Polar, Hydrophobic