Amino Acids and Proteins Flashcards
What are the four major types of molecules?
- Proteins
- Nucleic Acids
- Lipids
- Carbohydrates
What do proteins contribute to the cells?
- Enzymes
- Structural proteins
- Proteins interact with RNA and DNA
- Transport Systems (Lipid bound proteins)
- Glycosylated Proteins
- Cell recognition
What is mean by glycosylated proteins?
Interact with sugars
What is lactoferrin?
Iron binding protein
What happens to lactoferrin when binding with iron?
The shape of the protein changes substantial
Why is it good that lactoferrin changes shape when bound with iron?
Other molecules can distinguish between iron-free and the iron bound forms
Are proteins linear or nonlinear polymers?
Linear polymer
What is monomer called that makes up protein?
Amino Acids
What groups do amino acids have?
- Amino group
- Carboxyl group
- Side chain
- Hydrogen
What is the carbon called which the amino group and carboxyl group is bonded to?
a-carbon
Do amino acids have the same general structure?
Yes
What distinguishes amino acids from one another?
Variation in the side chains
What is bonded to the a-carbon in an amino acid?
- Side chain group
- Carboxyl group
- Amino group
- Hydrogen atom
How do you name amino acids?
End in -ine
What can we do for convenience when naming an amino acid?
Abbreviate to a three letter code
Some can be shortened to one letter
What are the four main groups of amino acids?
- Hydrophobic amino acids with nonpolar R groups.
- Polar amino acids with neutral R groups but the
charge is not evenly distributed. - Positively charged amino acids with R groups that
have a positive charge at physiological pH. - Negatively charged amino acids with R groups that
have a negative charge at physiological pH.
What can Glycine be abbreviated to?
- Gly
- G
What is the side chain of glycine?
H atom
What is chirality?
A molecule or ion which can not be superposed by its mirror image by any rotation or translation combination
Does glycine have chirality?
No
Does all amino acids except for glycine have chirality?
Yes
Is glycine flexible?
Yes
Why is proline an unusual amino acid?
As the side chain bonds to the amine
What does the structure of proline do to the protein?
Causes tight restraint
Does prolines peptide bond cause trans or cis or trans and cis conformations?
Trans and cis
Where do you normally find proline?
In proteins that need to be rigid
What protein needs proline?
Collagen
Where can histidine be found?
At the active sites of enzymes
What is the pka of histidine?
6.7 - Near neutral
Is histidine the only amino acid with a pKa near neutral?
Yes
Why is histidine important?
As the near neutral pH can allow the side chain to alter its charge at physiological pH
How can the charge of histidine be modulated?
By the amino acids surrounding it in the 3D structure of the protein
Why is histidine found at the active site of enzymes?
The imidazole ring can bind and release protons during enzymatic reactions
What is the side chain called on the amino acid cysteine?
Free thiol (SH) group
When a cysteine and cysteine react together what bond is formed?
Covalent bond
What is another name for the bond formed between two cysteine?
disulphide bond
What is the importance of disulphide bonds in proteins?
Correctly folds the protein
What pKa does the cysteine side chain have?
8.4
Where can you find cysteine?
At the active site of an enzyme
What do two cysteine produce?
A cystine
Is the reaction oxidation or reduction when forming cystine?
Oxidation
What do we need to worry about when talking about cysteine and cystine?
The spelling
Is this correct?
cystine + cystine —> cysteine
No, cysteine + cysteine —> cystine
What are zwitterions?
A molecule which has two functional groups. One functional group is has a positive charge. One functional group has a negative charge
What are amino acids in a neutral solution?
zwitterions
What overall charge net does a zwitterion have?
Zero
What is another word for zwitterions?
Dipolar ions
What is meant by protonated?
addition of a proton
What does deprotonated mean?
removal of a proton
In dipolar form is the amino group in an amino acid deprotonated or protonated?
Protonated
In dipolar form is the carboxyl group in an amino acid deprotonated or protonated?
Deprotonated
Is the carboxyl or amino group the first to be protonated when the pH is raised to 2?
Carboxyl group
When the pH gets to 9 what happens to the amino group?
Is deprotonated
What pH does the dipolar form persist to?
9
Are the side chains in amino acids charged or not charged?
Can be both
Do amino acids with aromatic side chains absorb strongly?
Yes
What do two amino acids form?
Peptide
What bond is formed between two amino acids?
Peptide bond
Finish the sentence:
Amino acids join together to make a peptide by the loss of a….
molecule of water
Are peptide chains in proteins in the trans or cis conformation?
Trans
Why are peptide chains in proteins in a trans conformation?
To prevent steric clashes
What amino acid at an exception from being a trans conformation?
Proline
What transformation does proline have?
Cis
Are the side chain of an amino acid in a TRANS conformation on the same or different side of the chain?
Different
Are the side chain of an amino acid in a CIS conformation on the same or different side of the chain?
Same
What is the amino acid sequences direction?
From amino terminal residue (N-terminal) to carboxyl terminal residue (C-terminal)
What are bond lengths measure in?
Angstroms