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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
Frame-shift mutations and splice site mutation
alter the amount or structure of the protein
26
what are the 4 characteristics of the genetic code
specificity, universality, degeneracy, | nonoverlapping and commaless
27
specificity
a particular codon always codes for the same AA
28
universality
it is conserved from very early stages of evolution
29
degeneracy
also called redundancy | a given AA may have more than one triplet coding for it
30
nonoverlapping and commaless
the code is read from a fixed starting point as a continuous sequence of bases without any punctuation between codons
31
What are the 3 sites of the ribosome
A site P site E site
32
A site
binds an incoming aminoacyl-tRNA according to the codon occupying the site
33
P site
occupies by peptidyl-tRNA which carries the chain of AA that has already been synthesized
34
E site
occupies by the empty tRNA as it is about the exit the ribosome
35
What are the two forms of ribosomes
free in the cytosol | or associated with the ER (RER)
36
RER-ribosomes
synthesize proteins that are to exported form the cell or to be places in cell membranes (plasma, ER, lysosome)
37
cytosolic ribosomes
synthesize cytosolic proteins or those intended for the nucleus, mitochondria or peroxisomes
38
What are the three steps in protein synthesis?
Initiation Elongation Termination
39
Initiation
assembly of components of the translation system before peptide bond formation occurs
40
elongation
addition of amino acids to the carboxyl end of the growing chain. ribosome moves form 5'-3' of the mRNA
41
What are the three steps of elongation?
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
termination
occurs when one of the three termination codons moves into the A site
43
What are the 6 possible fates of a newly generated protein>
- 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
How do cells recognize the 'delivery address' in a protein?
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
What three kinds of protein does the ER synthesize?
lysosomal, secretory, membrane
46
characteristics of signal sequences
10-36 AA long at least one basic AA 10-13 hydrophobis AA small AA int he cleavage site, Alanin
47
Topographic arrangement of membrane proteins (3 types)
Type 1- C-terminus in cytosol Type 2- N-terminus in cytosol several transmembrane protiens bound together
48
What are the four types of protein structure?
primary, secondary, tertiary, quaternary
49
Primary structure
AA are link by peptide bonds between alfa carbozyl group of one and alfa amino group of another
50
secondary structure
polypeptide backbone forms arrangements of AA located near each other
51
What are three types of secondary structures of proteins?
alpha-helix beta-sheet beta-bend
52
alpha helix
tightly packed coiled polypeptide chain side chains of AA extend outward to avoid interfering with each other stabilized by H-bonds
53
Two examples of alpha helix
``` keratin= fibrous myoglobin= globular ```
54
Beta sheets
parallel or anti-parallel (pleated- | all AA are involved in H-bonds)
55
Beta bends
reverse direction of a polypeptide chain, helps it form compact, globular shape Proline is usually cause of kink
56
Tertiary structure
globular proteins folding and final arrangement of domains interactions between AA side chains stabilize the structure
57
domains
fundamental functional and 3D structural units of polypeptides
58
What are the four AA side chain interactions that stabilize a protein structure?
disulfide bonds hydrophobic interactions H-bonds ionic interactions
59
protein folding
involves nonrandom, ordered pathways | final stage is fully loaded, functional form, defined by low-energy state= very stable
60
protein folding- denaturation
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
what are 5 types of denaturing agents?
``` heat organic solvents strong acids/bases detergents heave metal ions (lead) ```
62
Chaperones
heat-stable proteins that aid in protein folding | require ATP
63
Quaternary structure
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
function of structural protein
components of connective tissue, bone, tendon, skin, feathers, nail, hair, horn, mostly fibrous, insoluble in water ex) collagen, keratin, elastin
65
Function or enzymes
biological catalysts, most are globular, conjugated proteins ex) DNA polymerase, lipase
66
Function of hormones
proteinaceous hormones such as insulin, glucagon, gastrin, cholecystokinin/CCK
67
function of respiratory pigments
colored, conjugated proteins with a pigment (chrome) | ex) haemoglobin, myoglobin
68
function or transport protein
trnasport materials in cells and form channels | ex) serum albumin
69
function of contractile protein
can contract muscles with the expense of energy from ATP | ex) actin, myosin
70
function of storage proteins
store metal ions and AA in cells, found in seeds and pulses, egg and milk ex) ferritin (iron), casein, ovoalbumin, gluten
71
function of toxins
toxic proteins such as snake venom or plant toxins
72
What are two diseases caused by protein misfolding
Amyloid disease | prion disease
73
Amyloid disease
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
prion disease
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
Post-translational modifications
glycosylation= where a carb such as glycan is attached to a protein= glycoprotein
76
what are two types of glycosylaiton
N-glycosylation | O-glycosylation
77
N-glycosylation
starts in ER attachment of sugar to an amino group of Asn Asn-X-Ser/Thr further processing/modificaiton in Golgi
78
O-glycosylation
starts in Golgi attachment of sugar to hydroxyl group of Ser or Thr important for functional confirmation and sorting
79
protein-phosphorylation
amino residue is phosphorylated by kinase= addition of a covalently bound phosphate group changes the structure of the protein
80
What three areas does the Golgi consist of?
cis-golgi network medial-golgi and trans-golgi area trans-golgi network
81
cis-golgi network
protein phosphorylaiton
82
medial-golgi and trans-golgi area
N- glycosylation and O-glycosylation
83
trans-golgi network
proteins will be backed in vesicles and sent to the specific 'delivery address'

VP Exam 2 (10 decks)

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