Samenvatting
BCM 251 Summary
- Vak
- Instelling
BCM 251 detailed Summaries on lecture videos and lecture slides that can be used to study off for exams
[Meer zien]Voorbeeld 4 van de 179 pagina's
Voorbeeld 4 van de 179 pagina's
In winkelwagen
In winkelwagen
1 beoordeling
Door: hannahalexandralance • 9 maanden geleden
Verkoper
Volgen
ath101
Ontvangen beoordelingen
Voorbeeld van de inhoud
BCM 251 NOTESCHAPTER 3.1 – AMINO ACIDS
PROTEINS AND AMINO ACIDS’ FACTS
PROTEINS
‐ Proteins serve as the basic structural molecules of all tissues in the body
‐ Proteins make up nearly 17% of the total body weight
‐ 90-140 million molecules of proteins per one yeast cell
‐ Up to 1010 proteins per mammalian cell
AMINO ACIDS
‐ Amino acids are the fundamental building blocks of proteins
‐ Long linear chains of amino acids (polypeptides) make up proteins and determine their
structure, all their properties and the functions
‐ Amino acids consist of the following: carbon, hydrogen, oxygen, nitrogen and sometimes
sulfur
RESIDUES
‐ In proteins, each amino acid residue joined to its neighbour by a specific type of covalent
bond termed peptide bond
‐ Residue – loss of the elements of water when one amino acid is joined to another
AMINO ACID STRUCTURE
‐ general structure of amino acids consists of a carbon centre termed an 𝛼-carbon atom and 4
substituents linked to this atom
‐ 4 substituents:
• One amino group (NH2 → NH3+)
• Carboxyl group (COOH → COO-)
• Hydrogen atom (H)
• R-group (side radical)
‐ R group determines the structural identity and chemical properties of
individual amino acids
‐ The first 3 groups are common o all amino acids
‐ Basic amino acid structure is R-CH(NH2)-COOH → NH3+-RCH-COO-
Photos adapted from lecture slides A.THERON
,PROPERTIES OF AMINO ACIDS
PROPERTIES OF AMINO ACIDS DUE TO CARBOXYL GROUP
‐ Salt formation
• Amino acids are organic acids and may create salts with many cations:
‐ Reaction with alcohols (esterification)
‐ Reaction with amines to form amides
‐ Decarboxylation
• Amino acids may undergo alpha decarboxylation to form the corresponding amines
• This way many NB amines are produced from amino acids in living organisms
➢ Histidine → Histamine + CO2 (local immune response)
➢ Tyrosine → Tyramine + CO2 (role in blood-brain barrier)
➢ Tryptophan → Tryptamine + CO2 (neurotransmitter)
➢ Glutamic acid → 𝛾-amino butyric acid (GABA) + CO2 (neurotransmitter)
➢ Lysine → Cadaverine + CO2 (toxin)
PROPERTIES OF AMINO ACIDS DUE TO AMINO GROUP
‐ Reaction with mineral acids
‐ Reaction with benzaldehyde
• Schiff’s base formation is an intermediate step of the reaction of transamination –
important part of the biosynthesis of amino acids
Photos adapted from lecture slides A.THERON
, ‐ Sangers’ reaction
• Reaction with Sanger’s reagent produces a yellow-coloured derivative, DNB-amino
acid
• This reaction is used to detect amino acid concentrations, free N-terminal amino
acids in polypeptides and can be helpful in protein sequencing
• AA-NH2 + Sanger’s reagent = DNB + HF → REMEMBER THIS AND PRACTICAL USE OF
IT
PROPERTIES DUE TO AMINO GROUP AND CARBOXYL GROUP
‐ Peptide bonding
‐ Ninhydrin reaction
• Oxidative decarboxylation of 𝛼-amino acids
• Oxidised ninhydrin creates with the liberated NH3 a blue-coloured Rhumann’s
complex
• Very sensitive reaction used in analytic chemistry for detection of amino acids
• Remember application of this reaction
‐ Zwitterions
• The name “zwitter” is derived from German word “hybrid”
• Zwitterion (or) dipolar ion is a hybrid molecule containing positive and negative ionic
groups with no overall charge equal to zero
Photos adapted from lecture slides A.THERON
, • One proton is transferred from the carboxyl group to the amino group of self-
molecules at normal pH cellular levels
CHIRALITY OF AMINO ACIDS
‐ Optical properties
• All amino acids except Glycine possess optical isomers due to the presence of the
asymmetric 𝛼-carbon atoms
STEREOCHEMISTRY OF AMINO ACIDS
‐ In many cases – mirror images can be superimposed over the original by rotation
‐ Achiral objects – are superimposable on their mirror images
‐ Chiral objects – are not superimposable on their mirror images
‐ A chiral C-atom (chiral centre) in molecules is attached to 4 different groups
‐ Stereoisomers – molecules that differ from each other only by their 3D configuration
(optical isomer)
‐ Enantiomer – pairs of stereoisomers, which can be superimposed by a mirror reflection
‐ One chiral centre renders 2 optical stereoisomers, which are mirror reflections of one
another
‐ Maximum number of stereoisomers for a molecule: 2n (n = number of chiral centres)
‐ Total number of enantiomers: 2n/2 (n = number of chiral centres)
‐ Majority of natural amino acids, except Glycine, Isoleucine and Threonine – are enantiomers
and have L- and D- stereoisomers
‐ 𝛼-Carbon of all amino acids except Glycine is a chiral centre rendering a pair of enantiomers
(L- and D- stereoisomers)
‐ All amino acids found in proteins are L- stereoisomers
‐ D-amino acids may be found in several natural products synthesised by non-ribosomal
polypeptide synthetases (NRPS) and in cell wall of bacteria
‐ Solid wedge = out of paper plane
‐ Dashed wedge = behind
‐ Horizontal bonds = out of paper plane
‐ Vertical = behind
‐ Special nomenclature proposed by Fisher to specify the absolute configuration of the 4
substituents attached to the chiral carbon atom → D,L system for levorotatory (rotating
polarised light to the left) and dextrorotatory (to the right) glyceraldehyde
‐ L-stereoisomers = stereochemical isomers with the same spatial orientation of functional
groups regarding the aldehyde/carboxyl groups at the chiral centre – i.e. glyceraldehyde
Photos adapted from lecture slides A.THERON
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
√ Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, Bancontact of creditcard voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper ath101. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €9,76. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 67096 samenvattingen verkocht
Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen