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VP Exam 2 > Cell bio- proteins > Flashcards

Cell bio- proteins Flashcards

1
Q

What are the 7 functions of membrane proteins

A

transport, channels, enzymes, signal, hormone receptors, second messengers, structure proteins

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2
Q

What is the central dogma of molecular bio?

A

Dna-transcription-RNA-translation-protein

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3
Q

peptides

A

short chains of amino acid monomers linked by peptide (amide) bonds
50 fewer AA

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4
Q

What 6 class of molecules are all physiological processes dependent on?

A

enzymes, peptide hormones, contractile proteins, collage, hemoglobin, Igs

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5
Q

9 AA with nonpolar side chains

A

Gly, ALa, Val, Leu, Iso, Phe, Try, Met, Pro

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6
Q

Characteristics of nonpolar side chains

A

can’t participate in hydrogen or ionic bonding
don’t gain/lost electrons
oily/lipid like

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7
Q

hydrophopic effect

A

side chains that cluster together in the interior of the protein when in aqueous solution

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8
Q

Why is prolin different from other nonpolar amino acids

A

it has a rigid ring structure

has a secondary amino group= imino acid

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9
Q

6 AA with uncharged polar side chains

A

Ser, Thr, Tyr, Asp, Glu, Cyc

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10
Q

characteristics of uncharged polar side chains

A

zero net charge at pH 7
in basic pH, cyc and try can lose a proton
Asp, glu, ser and thr can form H-bonds

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11
Q

Why is cysteine different than the other uncharged polar side chains

A

it has a SH group= thiol group
can form disulfide bonds between proteins
can stabilize proteins

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12
Q

2 AA with acidic side chains

A

Asp and Glu

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13
Q

Characteristics of acidic side chains

A

donate protons

fully ionized at pH 7

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14
Q

3 AA with basic side chains

A

His, Lys, Arg

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15
Q

characteristics of basic side chains

A

accept protons

fully ionized and positively charged at pH 7

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16
Q

Why is histidine different than other basic side chains

A

it can be either positively charged or neutral depending on the environment’s pH
it has an important function as a buffer

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17
Q

What 4 AA are precursors of important molecules in physiology

A
  1. hydroxylation of tryptophan yields serotonin (neurotransmitter and paracrine hormone)
  2. Acetylation and methylation of serotonin to melatonin (hormone which influences reproductive activity)
  3. hydroxylation of tyrosine yields dopa, which is decarboxylated to form dopamine (a neurotransmitter)
  4. decarboxylation of histidine yields histamine (mediator of allergic reactions)
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18
Q

What 5 peptides have physiological relevance

A
  1. oxytocin= peptide hormone produced in hypothalamus (uterine contractions and milk secretion)
  2. antidiuretic hormone (ADH)= produced in hypothalamus and essential for maintenance of water balance
  3. Creatine= involved in energy production in muscle and cardiac cells
  4. Bradykinin= vasoactive substance
  5. angiotensin 2= a potent vasoconstrictor
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19
Q

polypeptide

A

long, continuous and unbranched peptide chain

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20
Q

4 polypeptides with physiological relevance

A
  1. Gastrin= stomach hormone, stimulates secretion of gastric glands
  2. CCK= stimulates pancreas and liver secretion
  3. GLucagon= produced by alpha-cells and of the pancreas
  4. Atrial Natriuretic Peptide (ANP)= produced in the heart, essential for regulation of blood volume and pressure
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21
Q

What are the four consequences of altering the nucleotide sequence

A

Silent mutation, Missense mutation, Nonsense mutation, Frame-shift mutations and splice site mutations

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22
Q

Silent mutation

A

the codon containing the changed base may code fro the same AA

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23
Q

missense mutation

A

the codon containing the changed base may code for a different AA

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24
Q

nonsense mutation

A

the codon containing the changed base may become a termination codon and the protein is truncated

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25
Q

Frame-shift mutations and splice site mutation

A

alter the amount or structure of the protein

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26
Q

what are the 4 characteristics of the genetic code

A

specificity, universality, degeneracy,

nonoverlapping and commaless

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27
Q

specificity

A

a particular codon always codes for the same AA

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28
Q

universality

A

it is conserved from very early stages of evolution

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29
Q

degeneracy

A

also called redundancy

a given AA may have more than one triplet coding for it

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30
Q

nonoverlapping and commaless

A

the code is read from a fixed starting point as a continuous sequence of bases without any punctuation between codons

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31
Q

What are the 3 sites of the ribosome

A

A site
P site
E site

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32
Q

A site

A

binds an incoming aminoacyl-tRNA according to the codon occupying the site

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33
Q

P site

A

occupies by peptidyl-tRNA which carries the chain of AA that has already been synthesized

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34
Q

E site

A

occupies by the empty tRNA as it is about the exit the ribosome

35
Q

What are the two forms of ribosomes

A

free in the cytosol

or associated with the ER (RER)

36
Q

RER-ribosomes

A

synthesize proteins that are to exported form the cell or to be places in cell membranes (plasma, ER, lysosome)

37
Q

cytosolic ribosomes

A

synthesize cytosolic proteins or those intended for the nucleus, mitochondria or peroxisomes

38
Q

What are the three steps in protein synthesis?

A

Initiation
Elongation
Termination

39
Q

Initiation

A

assembly of components of the translation system before peptide bond formation occurs

40
Q

elongation

A

addition of amino acids to the carboxyl end of the growing chain.
ribosome moves form 5’-3’ of the mRNA

41
Q

What are the three steps of elongation?

A
  1. bind the aminoacyl-tRNAN to the A-binding domain
  2. generate the peptide bond in site P
  3. movement of the mRNA through the small subunit
42
Q

termination

A

occurs when one of the three termination codons moves into the A site

43
Q

What are the 6 possible fates of a newly generated protein>

A
  • transport into the ER
  • topographic placement of membrane proteins in the plasma membrane
  • protein folding
  • transport from ER to the Golgi
  • glycosylation of the newly synthesized proteins of the Golgi
  • transport to other organelles
44
Q

How do cells recognize the ‘delivery address’ in a protein?

A

N-terminal sequence= import into the ER or import into mitochondria
C-terminal sequence= retention in lumen of ER
internal signals= import into nucleus or import into peroxisomes

45
Q

What three kinds of protein does the ER synthesize?

A

lysosomal, secretory, membrane

46
Q

characteristics of signal sequences

A

10-36 AA long
at least one basic AA
10-13 hydrophobis AA
small AA int he cleavage site, Alanin

47
Q

Topographic arrangement of membrane proteins (3 types)

A

Type 1- C-terminus in cytosol
Type 2- N-terminus in cytosol
several transmembrane protiens bound together

48
Q

What are the four types of protein structure?

A

primary, secondary, tertiary, quaternary

49
Q

Primary structure

A

AA are link by peptide bonds between alfa carbozyl group of one and alfa amino group of another

50
Q

secondary structure

A

polypeptide backbone forms arrangements of AA located near each other

51
Q

What are three types of secondary structures of proteins?

A

alpha-helix
beta-sheet
beta-bend

52
Q

alpha helix

A

tightly packed coiled polypeptide chain
side chains of AA extend outward to avoid interfering with each other
stabilized by H-bonds

53
Q

Two examples of alpha helix

A 
keratin= fibrous
myoglobin= globular
54
Q

Beta sheets

A

parallel or anti-parallel (pleated-

all AA are involved in H-bonds)

55
Q

Beta bends

A

reverse direction of a polypeptide chain, helps it form compact, globular shape
Proline is usually cause of kink

56
Q

Tertiary structure

A

globular proteins
folding and final arrangement of domains
interactions between AA side chains stabilize the structure

57
Q

domains

A

fundamental functional and 3D structural units of polypeptides

58
Q

What are the four AA side chain interactions that stabilize a protein structure?

A

disulfide bonds
hydrophobic interactions
H-bonds
ionic interactions

59
Q

protein folding

A

involves nonrandom, ordered pathways

final stage is fully loaded, functional form, defined by low-energy state= very stable

60
Q

protein folding- denaturation

A

unfolding and disorganization of a proteins secondary and tertiary structures
no hydrolysis of peptide bonds= primary structure remains intact
may be reversible, but usually not

61
Q

what are 5 types of denaturing agents?

A 
heat
organic solvents
strong acids/bases
detergents
heave metal ions (lead)
62
Q

Chaperones

A

heat-stable proteins that aid in protein folding

require ATP

63
Q

Quaternary structure

A

arrangement of polypeptide subunits
subunits are held together primarily by non-covalent interactions (H-bonds, ionic bonds, hydrophobic interactions)
subunits may function independently of one another or may work cooperatively

64
Q

function of structural protein

A

components of connective tissue, bone, tendon, skin, feathers, nail, hair, horn,
mostly fibrous, insoluble in water
ex) collagen, keratin, elastin

65
Q

Function or enzymes

A

biological catalysts,
most are globular, conjugated proteins
ex) DNA polymerase, lipase

66
Q

Function of hormones

A

proteinaceous hormones such as insulin, glucagon, gastrin, cholecystokinin/CCK

67
Q

function of respiratory pigments

A

colored, conjugated proteins with a pigment (chrome)

ex) haemoglobin, myoglobin

68
Q

function or transport protein

A

trnasport materials in cells and form channels

ex) serum albumin

69
Q

function of contractile protein

A

can contract muscles with the expense of energy from ATP

ex) actin, myosin

70
Q

function of storage proteins

A

store metal ions and AA in cells, found in seeds and pulses, egg and milk
ex) ferritin (iron), casein, ovoalbumin, gluten

71
Q

function of toxins

A

toxic proteins such as snake venom or plant toxins

72
Q

What are two diseases caused by protein misfolding

A

Amyloid disease

prion disease

73
Q

Amyloid disease

A

may be spontaneous misfolding or caused by mutation in a gene
long, fibrous protein of beta pleated sheets
extracellualr peptide= aggregates and is neurotoxic
ex) alzheimer, parkinson and huntington

74
Q

prion disease

A

infectious protein is an altered version of a normal prion protein, it forms insoluble aggregated of fibrils
ex) Creutzfeld-Jakob, scrapie, Mad cow disease

75
Q

Post-translational modifications

A

glycosylation= where a carb such as glycan is attached to a protein= glycoprotein

76
Q

what are two types of glycosylaiton

A

N-glycosylation

O-glycosylation

77
Q

N-glycosylation

A

starts in ER
attachment of sugar to an amino group of Asn
Asn-X-Ser/Thr
further processing/modificaiton in Golgi

78
Q

O-glycosylation

A

starts in Golgi
attachment of sugar to hydroxyl group of Ser or Thr
important for functional confirmation and sorting

79
Q

protein-phosphorylation

A

amino residue is phosphorylated by kinase= addition of a covalently bound phosphate group
changes the structure of the protein

80
Q

What three areas does the Golgi consist of?

A

cis-golgi network
medial-golgi and trans-golgi area
trans-golgi network

81
Q

cis-golgi network

A

protein phosphorylaiton

82
Q

medial-golgi and trans-golgi area

A

N- glycosylation and O-glycosylation

83
Q

trans-golgi network

A

proteins will be backed in vesicles and sent to the specific ‘delivery address’

VP Exam 2 (10 decks)

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