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Biochemistry > Proteins > Flashcards

Proteins Flashcards

1
Q

Levels of structural organization

A

4

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2
Q

Primary structure

A

amino acid sequence important: peptide bonds

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3
Q

secondary structure

A

alpha- helix beta- sheets important: H- bonds

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4
Q

Other secondary structures

A

loops and coils

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5
Q

alpha- helix characteristics

A

right handed Proline- not found in helical regions “helix breaker”

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6
Q

How peptide bonds are connected on an alpha- helix.

A

Each peptide bond is connected by H- bonds 4 AA residues ahead from it

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7
Q

Amino- acids per turn in a helix

A

3.6

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8
Q

Rule (n+4) for the alpha- helix

A

CO of 1st AA connected to the 4th AA ahead of it or behind of it

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9
Q

ß- sheet

A

H- bonding is bent to form the correct pleated sheet

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10
Q

anti- parallel ß-sheet

A

polypeptide strands run in the opposite direction

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11
Q

parallel ß- sheet

A

polypeptide strands run in the same direction

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12
Q

beta sheet arrangement of side chains

A

projected above and below the plane

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13
Q

Bends, loops and turns

A

non- regular, non- repetitive secondary structures

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14
Q

What AA are present in bends and turns?

A
  • Glycine (Gly)
  • Proline (Pro)
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15
Q

Globular proteins

A

bends, loops and turns over their surface (rich in Gly and Pro over the surface)

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16
Q

Describe globular proteins

A

a- helices and B- sheets= core of the globular protein bends and turns = surface of the globular protein

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17
Q

Tertiary Structure

A

a- helix, ß- sheet and bends arrange in a regular fashion to form the fundamental functional and 3D structural unit.

18
Q

Describe alpha- helix (secondary structure)

A
  • Right handed
  • Hidrogen bonds are the most important
  • trans side chains project outward and outward from the helix
  • Proline is not found, is a helix breaker because the ring causes a kink an change of direction
19
Q

What is the function of bends, loops and turns?

A
  • Reverse the direction of a polypeptide chain
    *
20
Q

Where are bends, loops and turns found in a globular protein?

A
  • Over the surface
21
Q

What “special bonds” are found in the tertiary structure?

A

disulfide bonds

22
Q

In a quaternary structure which are the predominant interaction?

A

Covalent or non covalent between subunits

23
Q

Define quaternary structure

A

Specific interactions between domains or subunits

24
Q

What is the effect of assembly into a multisubunit

A

Increases the stability of a protein and improves proteins efficiency

25
Q

Protein Folding

A
  • Can be spontaneous by a trial and error process
  • Chaperones and chaperonines assist in the process
  • cis- trans isomerase participates
  • protein disulfide isomerase participates
26
Q

Most important proteins that assist in protein folding

A
  • chaperones
  • chaperonines
27
Q

Why proteins are degraded?

A

misfolding or have accomplished their lifetime

28
Q

How proteins are degraded?

A

By the Ubiquitin- Proteasome Pathway System

  • tag with Ubiquitin
  • 28 subunit proteasome machinery comes and degrades
29
Q

Define pre- fibrils

A

pre- fibrils are proteins that become misfolded but are succesfully degraded

30
Q

Describe Amyloidosis

A
  • When prefribris (ß- sheets) fail to be degraded, they aggregate together and form amyloid fibrils
  • Excess degradation
  • more deposition
  • Organ dysfunction
31
Q

What process is caused by the accumulation of amyloid repeated ß- sheet structure from partially degraded proteins ?

A

“seeding”

  • process of conversion and deposition
32
Q

Congo red dye

A

deposition of amyloid structures seen red in light microscopy

33
Q

Apple- green birefringence

A

amyloid structures seen under polarized light

34
Q

Prion disease

A
  • PrPc normal is a- helix rich with litle or no ß- sheets
  • PrPsc turns rich with ß- sheets

Diseased is insoluble and becomes accumulated which are resistant to degradation

35
Q

Describe Prion Diseases

A
  • spongiform degeneration
  • astrocytic gliosis in the CNS
  • Rapid Brain shrinkage ad deterioration
  • In humans: Creutzfeld- Jakob Disease
  • transmissible via Mad cow disease
36
Q

Creutzfeld- Jakob Disease-CJD (Prion disease in humans)

A
  • Type 1:Sporadic (commonest- 85%)
    • somatic cell mutation OR
    • Rare spontaneous refolding of PRPc to PRPsc
  • Type 2: Familial CJD
37
Q

Alzheimer disease

A
  • Amyloid accumulation of Aß42 having characteristic ß- pleated sheets, precursor of Aß42 is APP (amyloid precursor protein)
  • Neurofibrillary tangles
38
Q

Neurofibrillary tangles

A
  • Alzheimers
  • hyperphosphorylated tau proteins
  • inside neurons
39
Q

Parkinson’s disease

A
  • multifactorial
  • important defect in ubiquitin proteasome pathway to degrade a- synuclein which leads to its accumulation (bound to ubiquitin)—–> inclusions (Lewy bodies)
40
Q

Describe Parkinson’s Disease

A
  • Face is expressionless
  • Tremors
  • pill- rolling tremor
  • Bradykinesia (slow movement)
  • Rigid muscles —-> limited ROM
  • Shuffling gate
  • Impaired posture and balance
  • speech changes
41
Q
A

Biochemistry (7 decks)

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