Q.General structure of amino acid is given :
[Figure shown in the original paper]
Draw the structure of the amino acids,

Glycerol is a 3-carbon triol (CH2OH-CHOH-CH2OH), serine is HOOC-CH(NH2)-CH2OH; the most abundant animal protein is collagen and two aromatic amino acids are phenylalanine and tyrosine.

(a) Structures (written in line-formula form):

• (i) Glycerol - a trihydroxy alcohol with three carbons: CH2OH-CHOH-CH2OH (top and bottom carbons each bear one -OH, the middle carbon bears one -OH).
• (ii) Serine - an amino acid: a central (alpha) carbon bonded to COOH, NH2, H and the side chain CH2OH, i.e. HOOC-CH(NH2)-CH2OH.

(b) Naming: …

The zwitterion is the dipolar-ion form of an amino acid, in which the amino group is protonated (–NH3⁺) and the carboxyl group is deprotonated (–COO⁻) simultaneously.

Every amino acid has the general structure R–CH(NH2)–COOH, with both an acidic carboxyl group (–COOH) and a basic amino group (–NH2) attached to the same alpha-carbon.

In aqueous solution (and in the solid crystalline state), these two functional groups react with each other intramolecularly:

• The carboxyl group (–COOH) donates a proton (H⁺) and becomes negatively charged: –COO⁻
• The amino group (–NH2) accepts that proton and becomes positively charged: –NH3⁺

The resulting structure, R–CH(NH3⁺)–COO⁻, carries both a positive charge and a negative charge at the same time, yet the molecule as a whole is electrically neutral (the charges cancel out). This dipolar, doubly-charged-yet-neutral form is called the zwitterion (from German "zwitter" = hybrid).

…

Both amino acids follow the general structure H2N–CH(R)–COOH shown in the figure; glycine has R = H (the simplest amino acid) and serine has R = –CH2OH (a hydroxyl-bearing side chain).

As only text can be shown here, the structures are represented linearly, following the same layout as the given general formula (COOH on top, central carbon bonded to H and NH2, R group below):

(a) Glycine (R = H):

      COOH
       |
  H — C — NH2
       |
       H
``` …

Both are amino acids built on the same core plan -- a central (alpha) carbon bonded to -NH2, -COOH, -H, and a variable R group -- with R = -CH3 for alanine and R = -H for glycine.

Every amino acid has a general structure: a central carbon (the alpha-carbon) attached to four groups -- an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a side chain/R group that differs between amino acids and gives each its identity.

(a) Alanine has R = -CH3 (a methyl group). Its structure is CH3-CH(NH2)-COOH, i.e. the alpha-carbon carries -NH2, -COOH, -H, and -CH3.

…

Amino acids differ in their R-group attached to the central (α) carbon; Glycine's R group is –H, Alanine's is –CH₃.

Every amino acid has a general structure with a central α-carbon bonded to: an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom (–H), and a variable R group (side chain) that determines the amino acid's identity and properties.

• Glycine: R group = –H (hydrogen atom). This is the simplest amino acid and, because of this, glycine is not optically active (it is the only amino acid without a chiral α-carbon). …

Both are amino acids; the one with a CH2OH side chain is serine and the one with a CH3 side chain is alanine.

An amino acid has a central (alpha) carbon bonded to a carboxyl group (COOH), an amino group (NH2), a hydrogen atom, and a variable side chain called the R group. The identity of the amino acid is decided by its R group.

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