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Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their...
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Transcript of Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their...
![Page 1: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/1.jpg)
Digression of amino acidsCissy Gao / Irene Meng / Zero Yao
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Today’s Object• Identify amino acids and understand their structure
•Identify the peptide bonds in dipeptides and polypeptides
•Explain why amino acids are soluble in water
![Page 3: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/3.jpg)
What is amino acid?
• An amino acid is a carboxylic acid with an amine group at the 2-position.
– A carboxylic acid contains a –COOH group.– An amine group contains a NH₂ group.
• Amino acids are the building blocks of proteins.A general 2-amino acid
CH₃—CH—COOH
NH₂2-aminopropanoic acid [alanine]
![Page 4: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/4.jpg)
Amino group Carboxyl group
Hydrogen atom
Radical group
Central carbon
S t r u c t u r e
![Page 5: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/5.jpg)
• An amino acid has a central carbon atom bonded to a hydrogen atom and three groups:
– An amino group(-NH₂)– An carboxyl/acidic group(-COOH)– An R group [radical group] “R" can be quite a complicated group containing
other active groups like -OH, -SH, other amine or carboxylic acid groups, and so on.
• There are only 20 different amino acids.– Amino acids differ from one another by their R group
Structure Summary:
![Page 6: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/6.jpg)
![Page 7: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/7.jpg)
Reaction:
• Amino acids can react with both acids and bases.
CH₃—CH—COOH + H⁺
NH₂
CH₃—CH—COOH
+NH₃
Reaction with acids
Reaction with bases
CH₃—CH—COOH + OH⁻
NH₂
CH₃—CH—COO⁻
NH₂
+ H₂O
[alanine]
After reacting with either an acid or base the amino acid is ionic and remains soluble in water.
![Page 8: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/8.jpg)
Two important properties:
1. Amino acids are highly soluble in water.
Amino acids have both acid and base groups arranged such that the acid and base groups can “neutralize” each other.
H atom is lost from COOH and gained by NH₂
IonicAcidic
Basic
zwitterion
![Page 9: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/9.jpg)
2. Amino acids link with each other to form “dipeptides” and “polypeptides”.
Two important properties:
• An amino acid can be referred to as a peptide.• When two amino acids bond together, they produce a dipeptide.
Question #1: When three amino acids bond together, what is it called?
Answer: Tripeptide
Question #2: When more than three amino acids bond together, what is it called?
Answer: Polypeptide
![Page 10: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/10.jpg)
2. Amino acids link with each other to form “dipeptides” and “polypeptides”.
Two important properties:
H—N—CH₂—C—OH + H—N—CH₂—C—OH
H H
O O
H—N—CH₂—C—N—CH₂—C—OH + H₂O
H
O O
H Peptide bond[Amide linkage]
Dipeptide
Dehydration synthesis-water is removed
![Page 11: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/11.jpg)
2. Amino acids link with each other to form “dipeptides” and “polypeptides”.
Two important properties:
• A series of amino acid molecules can be joined by a series of amide linkages to form a polypeptide.
• A polypeptide is a single chain of amino acids.• The order or combination of these amino acids determines which protein is produced.
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Practice:
1. Identify which of the following is an amino acid.
![Page 13: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/13.jpg)
2. What is this reaction called ?
Dehydration synthesis
![Page 14: Cissy Gao / Irene Meng / Zero Yao. Today’s Object Identify amino acids and understand their structure Identify the peptide bonds in dipeptides and polypeptides.](https://reader036.fdocuments.in/reader036/viewer/2022062809/5697bfd11a28abf838cab563/html5/thumbnails/14.jpg)
Bonus:
Hydrogen bondBesides peptide bond, what other bond is presented?
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Video