Amino Acids
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All amino acids have. central carbon atom bonded to, what four substituents?
A carboxylic acid group, an amine group, a hydrogen atom and an R group
What the does R group determine in an amino acid?
The size, name and its polarity
Of the 21 amino acids, how many are essential and why? (esntl. bcse. cnt. synthsd. bdy. + mst. obtnd. frm. diet)
9 of the 21 amino acids are essential because they cannot be synthesised by the body and must be obtained from the diet
How many amino acids do humans use and how many show optical isomerism?
Use 21; 20 show optical isomerism
Why do amino acids have higher melting points than similar - sized molecules? (AA hve. strng. elctrstc. frcs. btwn. zwtrns. rqre. alt. enrgy. brk,)
This is because amino acids have strong electrostatic forces between zwitterions that require a lot of energy to break
What happens to amino acids in neutral conditions? (amne. grp. gns. prtn. bcme. NH3+ and crbxylc. acd. grp. lsss. prtn. bcme. COO frmng. Z)
The amine group gains a proton to become NH₃⁺ and the carboxylic acid group loses a proton to become COO⁻, forming a zwitterion
What is a zwitterion? (mlcle. cntns. bth. pos./neg. chrg. - ovrll. ntrl. chrge.)
A molecule that contains both a positive and negative charge but has an overall neutral charge
What type of forces exist between zwitterions?
Strong electrostatic forces
How do amino acids act in terms of acids and bases?
The NH₂ group acts as a base and the COOH group acts as an acid
What happens to amino acids in acidic conditions, are amide groups protonated in acidic conditions?
All amine groups gain a proton and become NH₃⁺, however amide groups are not protonated
What is formed when an amino acid reacts with hydrochloric acid (HCl)?
A salt is formed and chloride ions are present
What happens to amino acids in alkaline conditions?
All carboxylic acid groups lose a proton to form COO⁻ ions
What conditions are considered alkaline for amino acids?
Aqueous NaOH or high pH conditions
Why are amino acids soluble in water? (thy. frm. zwtrns. alwng. ion dpl. intrctns. w/ wtr. mol.)
Because they form zwitterions, allowing ion–dipole interactions with water molecules
Draw this amino acid (lystine) as a zwitterion:
At what point do amino acids become zwitterions?
At the Isoelectric point