Day 3: Amino Acids and Peptides Flashcards
What are the three options for the use of Amino Acids (AA) in our body?
- synthesis of protein and peptides. AA’s are the building blocks of proteins
- Synthesis of essential nitrogen containing biomolecules
- AA (protein) cant be used as fuel directly. During starvation, some AAs can be converted to glucose or ketone bodies to be used by cells as a source of energy
What is the bodies more perferred fuel?
Glucose: comes from carbs in diet like starch, sucrose, lactose
When low glucose the body burns fat as fuel
Can our brain use dietary fats as fuel?
No, it cant. so during starvation, some AAs are converted to glucose, fat and some AAs convert to ketone bodies to meet energy needs of the brain.
Can protein drugs be delivered orally?
No, it will get broken down into single amino acids by our GI system before being absorbed by our body
What are proteinogenic amino acids?
All the proteins in eukaryotes are composed of 20 different amino acids known as standard amino acids
**The name means that they are present in AA
What is the chirality of standard amino acids?
they are all chiral expect for glycine
what are human proteins composed of?
L-amino acids, no exeptions
What are proteases?
a group of enzymes whose catalytic function is to hydrolyze (break down) proteins by breaking the peptide bonds
also called proteolytic enzymes or proteinases
What are the two main groups and the subgroups of amino acids?
Main groups: Hydrophobic and Hydrophilic
Subgroups: Charged, Aromatic, Sulf-containing, branched-chain
What are the charged amino acids?
Negative: Aspartic acid, Glutamic acid
Positive : Lysine, Histidine,, Arginine
What are the polar amino acids?
Polar (hydrophilic): Tyrosine, Serine, Cysteine, Threonine, Asparagine, Glutamine
What are the Non-Polar amino acids?
Non-polar (hydrophobic): Glycine, Alanine, Valine, Leucine, Tryptophan, Methionine, Isoleucine, Proline, Phenyl alanine
What are the branched-chain amino acids?
Valine, Leucine, Isoleucine
BCAAs: May be useful supplement for muscle recovery and immune upregulation
What are the Aromatic amino acids?
Phenylalanine, Tyrosine, Tryptophan
What are the Sulfur-containing amino acids?
Cysteine, Methionine
What is Protein Phosphorylation? (Phosphorylation of amino acids)
One of the most important modes of regulation of protein function. (phosphoregulation)
almost all cases of phosphoregulation, the protein switches between active and inactive form.
What are the three amino acids that can be phosphorylated at hydroxyl residue
Serine, tyrosine (major), throenine
What are residues?
Amino acids that make up, or that are derived from a polymer
Direction is always N-terminal to C-terminal
What is a dipeptide?
Contains 2 residues
What is a tripeptide?
Contains 3 residues
What is an oligopeptide?
contains a few residues
What is a nonapeptide?
An oligopeptide containing nine amino acid residues
ex: oxytocin
what is a polypeptide?
Contains many residues
What is a protein (in terms of residues)
Has many residues (have defined 2D and 3D structure, usually ~40+
What are disulfide bonds?
These bonds between cysteine residues play a major role in the corsslinking folding and stability of the proteins
These protein crosslinking increases the rigidity, functions and proteolytic resistance
What is the ioselectric point (pI) of amino acids, peptides, and proteins
its when they carry no net electrical charge (equal numbers of + and - charges).
EX: if a peptide have 2 + and two - charges, overall charge is 0
What kind of charge do AAs / peptides / proteins carry at a pH value below the pI
A net postive charge
What kind of charge do AAs / peptides / proteins carry at a pH value above the pI
a net negative charge
Why do you want to know the values of peptides?
can be utilized for protein and peptide isolation, identificationa nd delayed absorption
When are peptides and proteins least soluble in water and whats the clinical implication of this?
At their isoelectric points
A peptide with pI 6 will be less soluble than a peptide with a pI 5 at pysiological pH (7.3)
Clinical implication: Long acting insuline Glargine; added modifications which lead to a shift of the pI from pH 5.4 to pH 6.7, making insulin glargine less soluble at physiological pH levels. This retarded its absorption and thereby extended its duration of action
What is an essential amino acid and which ones are they?
Cannot be synthesized in our body
valine, lysine, typtophan, leucine, methionine, phenylalanine, isoleucine, threonine, hisidine
9 of them