Amino acids Flashcards
What do amino acids contain
They contain a COOH group and an NH2 group
What is special about an α (alpha) amino acid?
They have an NH2 and COOH group bonded to the same carbon
Draw an amino acid with an R group
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What are the equilibrium equations with H+ ions
- NH2 + H+ → NH3
2. COOH → COO- + H+
What happens to the equilibrium in acidic and alkaline solutions?
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Draw an amino acids in acidic, alkaline solutions
Draw a zwitterion
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What are all amino acids at a low pH
All NH2 groups are pronated
What are all amino acids at a high pH
All COOH groups are depronated in high pH solutions
Draw lysine at pH 7 and pH 1
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Draw the structure of glycine, alanine, lysine and glutamic acid
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What are some physical properties of amino acids?
- High melting points
- Exist as dipolar ions, attraction between them is very strong
- Soluble in water
Give an example of the reaction of Glycine with sodium carbonate and where do these reactions take place on the molecule?
Observations?
2H2NCH2COOH + Na2CO3 → 2H2NCH2COONa + CO2 +H2O
Occur at the COOH group.
Bubbles of gas produced
Give an example of the reaction of Glycine with nitrous acid.
How is the nitrous acid formed? Where does the reaction occur? Observations
Nitrous acid is formed in situ from Sodium nitrite and Hydrochloric acid (HNO2)
The NH2 group is replaced by OH group
H2NCH2COOH + HNO2 →HOCH2COOH + N2 + H2O
Bubbles of gas produced
Give an example of the reaction of glycine with copper (II) sulfate. What is formed? What does glycine act as?
Observations
A complex is formed with a coordination number of 4.
Glycine acts as a bidentate ligand
Cu2+ + 2H2NCH2COOH → [Cu(H2NCH2COOH)2]2+
Blue solution formed when solutions of copper (II) sulfate and glycine are mixed
How are peptides formed?
Amino acids react together in a condensation polymerisation to form peptides.
What is the peptide group?
-CONH-
Show the formation of a peptide from glycine and alanine
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What are the two ways a peptide link can be hydrolyses?
Acidic - All NH2 groups become pronated to NH3+, COOH remains untouched. Positive amino acids
Alkaline - The amino acid formed is depronated, all COOH become COO-, negative amino acids. NH2 unaffected
How are amino acids identified?
All are colourless, chromatography is used, sprayed with ninhydrin and the compared against known Rf values.
What is the primary structure?
Sequence of amino acids joined by peptide links in the chain
What is secondary structure?
The twisting/coiling of the chain to form a β pleated sheet /α helix by intramolecular hydrogen bonding
What is tertiary structure?
The bending/folding of the secondary structure to give a precise 3D shape held together by hydrogen bonding / disulphide brides / ionic interactions / Van der Waals
What causes the different interactions?
The R groups are generally responsible for the interactions of amino acids. Non polar R groups are hydrophobic
Give a description of proteins as enzymes
Enzymes are biological catalysts. Enzymes provide an active site, the substrate binds to the active site. Initially binding holds it, but then changes occur in the active to fit around the substrate and hold it strongly. Induced fit model . Chemical groups in the active site catalyse the reaction.
What happens to enzymes at higher temperatures and non optimal pH
Temp - The enzyme become denatured, the bonds which hold the tertiary shape together are broken
pH - If the equilibrium of NH2 and COOH is altered it will affect the bonding
What are the different enzymes for carbohydrates, lipids and proteins?
Carbs - Amylase
Protein - Protease
Lipids - Lipase
What benefits are there of enzymes in washing powder?
Function at a lower temperature therefore save money
