Fichas
Proteins
Fichas del conjunto (35)
- 1What are some roles of proteins?structural
catalysts (enzymes)
carrier (haemoglobin)
protective (antibodies)
signalling (receptors) - 2What is the function of a protein determined by?external chemistry and shape
^determined by amino acid composition
diff AA have diff chemical and structural properties - 3What are the levels of protein structure?primary - sequence of AA
secondary- 2D fold
tertiary- 3D fold
quaternary - interaction of subunits - 4What are two key features of the primary structure of a protein?N-terminus
-amino terminus (H3N+)
C-terminus
-carboxyl terminus (COO-) - 5How many different R groups are there? Why are they important?20
result in a variety of chemical properties:
hydrophobic/hydrophilic
polar/non-polar
structural - 6Which amino acids have nonpolar, aliphatic side groups?glycine, Gly G
alanine, Ala A
valine, Val V
leucine, Leu L
methionine, Met M
isoleucine, Ile I - 7Which amino acids have aromatic side groups?Phenylalanine, Phe F
Tyrosine, Tyr Y
Tryptophan, Trp W - 8Which amino acids have positively charged side groups?Lysine, Lys K
Histidine, His H
Asparagine, Asn N - 9Which amino acids have negatively charged side groups?Glutamate, Glu E
Aspartate, Asp D - 10Which amino acids have polar, uncharged side groups?Serine, Ser S
Threonine, Thr T
Cysteine, Cys C
Proline, Pro P
Aspartate, Asp D
Glutamine, Glu Q - 11What is the peptide bond?bond that holds adjacent AA together
structural implications:
planar, H bonding - 12What differentiates a protein from a peptide?chains from 50+ are classed as proteins
- 13Why is there such a huge variation in proteins?50-2500 AA in a typical protein
20 possible AA per positon
so huge variation - 14What is the secondary structure of a protein determined by? What are the two main types?the interactions between the peptide bonds via hydrogen bonding
two main types: a-helix and B-sheet - 15Explain the a-helix secondary structure3.6 residues per 360degturn
stabilised by H bonding between peptide bonds - results in 0.54nm pitch
R groups point downwards - 16Explain the b-sheet secondary structureforms a flat sheet surface with strands of protein alongside
stabilised by H bonds between amide links
strands can be parallel or anti-parallel
b-sheets can be stacked to form 3D structure - 17What is the tertiary structure?the 3D fold of the protein which brings together secondary structure in 3D space
- 18What is the quaternary structure?a fold of 3D folded
not all proteins have quaternary structure
can be homo or hetero
e.g. haemoglobin (4 subunits) - 19Explain the structure of collagenstrong 3D structure
triple helix with a large number of prolines in a Pro-Pro-Gly
staggering of the three chains helps H-bonding btw chains - 20What is the result of post translational modification of amino acid side chains?covalent strand crosslinks
includes di-sulphide bonds between cysteine and lysine - 21What is the nomenculture of proteins based on?3D shape
globular
-majority of proteins
-overall globular shape, with a mix of 2nd structures
fibrous
-extensive packaging of 2nd structure
-often dominated by one type of 2nd structure
-form structural proteins e.g. collagen, keratin - 22Proteins can be made up of domains. What are protein domains?discrete regions of 3D structure
- 23What are proteins produced by?ribosomes
(translation of RNA to proteins) - 24What is the hydrophobic effect?the observed tendency of nonpolar substances to aggregate in aqueous solution and exclude water molecules
in proteins this means you get a hydrophobic centre
the exceptions to this is membrane proteins - 25What are molecular chaperons?a diverse group of proteins that assist with the folding and in some cases unfolding of proteins but are not involved in the usual biological functions for these proteins
- 26When do levels of chaperones increase?when the cell is subjected to stress e.g. heat shock
- 27How do chaperones help with folding?some bind to hydrophobic residues and prevent hydrophobic effect driven folding e.g. HSP70
some act to protect the folding protein from the cytoplasm e.g GroEL
chaperones often use ATP to provide energy to the folding process - 28What are some causes of protein folding diseases?inherited mutation
environmental stress
mechanism
-loss of function
-toxic gain of function
-dominant negative - 29What are some diseases associated with protein folding?neurodegeneration
-Alzheimer's
-Parkinson's
metabolic disorders
-monogenic obesity
cancer - 30What are the four types of post translational modification of proteins?addition of other functional groups
-acetate, phosphate, lipids
addition of other proteins/peptides
-Ubiquitination
changing the chemical nature of AA
-Deamination
structural changes
-Di-sulphide, cleavage - 31Explain how protein phosphorylation worksaddition of covalently bonded phosphate group by protein kinases
usually Ser, Thr, Tyr
alters structural conformations of a protein causing it to become activated, deactivated or changes its function
(dephosphorylation done by phosphatase) - 32Explain the importance of the formation of di-sulphide bonds - a post translational modificationcovalent links between cysteine residues
stabilises 3D structure
require specific environment to form
(often found extracellularly) - 33Explain the importance of cleavagebreaks down proteins into smaller peptides and amino acids so can be absorbed and used by an organism
e.g.
preproinsulin --> proinsulin --> insulin - 34Explain the process of Ubiquitinationfree Ubiquitin = Ub
Ub activated by E1 which uses ATP to form complex with Ub
E1-Ub transferred to E2
E2 joins to E3 - allows polymerization of 1 or more Ub molecules on target proteins
mono-Ubation= regulatory processes e.g. endocytosis, DNA repair, transcriptional regulation
multi-Ubation - labels substrate for degradation by the proteasome - 35What is deamination?unavoidable chemical reaction in physiological conditions
but can be reduced by removing reactive species from the cytosol
results in structural changes - therefore, protein damage
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- El usuario ha eliminado su información de asignaturas Fichas sobre Proteins, creado por Usuario eliminado el 08/09/2018.
- Creado por
- Usuario eliminado · sep 2018
- Actualizado
- 8 sep 2018
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- Creado por Ifeoma Ezepue · 13 nov 2015
- Copiado por amaim maryam · 8 sep 2018
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