Topic 2. Amino acids peptides and protein Flashcards
Primary structure of a polypeptide chain
the sequence of amino acids in the polypeptide chain, termed the protein configuration
Secondary structure of a polypeptide chain
how the chain is folded as a result of interaction of peptide bonds; such as helix or pleated sheet.
Tertiary structure of a polypeptide chain
dealing with R group interactions, or large scale bends and folds of helix’s.
Quaternarystructure of a polypeptide chain
how polypeptide chains interact if there are more than one in the single protein. 2 or more polypeptide chains.
some general functions of proteins (8)
biological catalysts, Transport, Storage, contracting muscles, cell structure, defence, hormones/regulation, semi permeable membranes.
The term prosthetic group is used to indicate
the non-protein part of a conjugated protein
All amino acids have - the same skeleton of a central (or alpha) carbon atom, with attachments of: (4)
- an amino groupN2R
- a carboxy group COO
- a hydrogen atom H
- an R side-chain group.
Aliphatic R groups
nonpolar and hydrophobic, Hydrophobicity increases with increasing number of C atoms in the hydrocarbon chain. Although these amino acids prefer to remain inside protein molecules,
2 examples of Non-polar aliphatic R group amino acids
Alanine(CH), Glycine(H)
they tend to cluster together within proteins, stabilizing protein structure by means of hydrophobic interactions
Aromatic R group amino acid example
Tyrosine (C-Benzene-OH
r aromatic side chains, are relatively
nonpolar (hydrophobic)
Polar, uncharged R group amino acids
Serine (CHOH), cystein (CHSH)
these amino
acids are more soluble in water, or more hydrophilic,
than those of the non polar amino acids, because they
contain functional groups Lhat form hydrogen bonds
Positively charged R group amino acid example
Lysine (CCCCNH3). The most hydrophilic
R groups are those that are either positively or negatively charged.
Negatively charged R group amino acid
Aspartate (CCOO)
chiral atom
the atom in a molecule that is bonded to four different chemical species.
alpha carbon
is a carbon atom bonded to a functional group in an organic compound; the carbon atom next to the α carbon is the beta (symbol: β) carbon,
Where to place the amino group when drawing structures of amino acids?
generally always on the left (L) unless drawing its stereoisomer (D)
2 cysteins can become …….. after formation of a disulfide bond/bridge?
cystine
amphoteric
of a compound, especially a metal oxide or hydroxide) able to react both as a base and as an acid.
zwitterions
where the amino acid has an equal number of positive and negative charges
pKa value?
The pKa value is one method used to indicate the strength of an acid
Tryptophan is a precursor to
auxin
Lignin is derived from what amino acid?
phenylalanine
2 amino acids which help form tannins?
tyrosine and Phenlyalanine
amino acids which are neurotransmitters in the brain
glycine, aspartate and glutamate
Hormones, Dopamine
Noradrenaline and Adrenaline are all derrivitives of which amino acid?
tyrosine
peptide bond
Two amino acid molecules can be covalently joined
through a substituted amide linkage called a peptide bond
oligopeptide
are short chains of amino acid monomers linked via peptide bonds. The term oligopeptide is used to refer to a peptide with fewer members of amino acids as opposed to a polypeptide, which is a peptide comprised of several amino acid residues.
Amphoteric molecule
has a both negative and positive charge
5 different structure Categories of amino acids
- non polar aliphatic
- aromatic
- polar uncharged
- positively charged
- negatively charged
folding due to H bonds place proteins into two classes:
globular and fibrous
globulous: mainly coiled or folded (helix) are generally enzymatic. while fibrous proteins: elongated (pleated sheet) are generally structural.
A protein with multiple polypeptide chains are called
oligomeric protein
Denaturation of a protein is defined as
any change of shape of a protein associated with loss of function. Does not come about by cleaving covalent bonds, but by disrupting the weak forces that maintain the tertiary structure.
The 5 forces maintaining protein structure
- covalent bonding
- ionic bonding
- hydrogen bonding
- hydrophobic interactions
- Van der Waals interactions
Collagen protein
is perhaps the most abundant protein in animals (constituting about 25% of all proteins) and is the major protein in extracellular matrix. Collagens are involved in cell adhesion and provision of elasticity in connective tissues.
Myoglobin
is a conjugated protein with the iron-containing compound haem as its prosthetic group. It is the oxygen-storing protein of muscle. Its role is to accept oxygen from haemoglobin and carry it to the respiring cells.
Haemoglobin
is the oxygen-carrying protein in blood. It carries oxygen from the lungs to the tissues. It consists of four chains,
