Advices For Studying Organic Chemistry

H

HO C

HO

HO HO

H 3 C

COOH

H

H 3 C C

COOH

H

C

H 3 C COOH

COOH

C

H 3 C H

Mismatch (−)

Mismatch

(+) (−)

Mismatch

(+)

Mismatch

Na+−OOCCHC(OH) C

H

COO−+NH 4

OH OH Y

H 3 C C

H

COOH X C

H

Z

Sodium ammonium tartrate Lactic acid

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5.3 THE BIOLOGICAL IMPORTANCE OF CHIRALITY

1. Chirality is a phenomenon that pervades the university.
   
   
   1. The human body is structurally chiral.
   
   
   2. Helical seashells are chiral, and most spiral like a right-handed screw.
   
   
   3. Many plants show chirality in the way they wind around supporting structures.
      i) The honeysuckle (忍冬;金銀花), Lonicera sempervirens, winds as a
      left-handed helix.
      ii) The bindweed (旋花類的植物), Convolvuus sepium, winds as a right-handed
      way.
   
   
   
   


2. Most of the molecules that make up plants and animals are chiral, and usually only
   one form of the chiral molecule occurs in a given species.
   
   
   1. All but one of the 20 amino acids that make up naturally occurring proteins are
      chiral, and all of them are classified as being left handed (S configuration).
   
   
   2. The molecules of natural sugars are almost all classified as being right handed (R
      configuration), including the sugar that occurs in DNA.
   
   
   3. DNA has a helical structure, and all naturally occurring DNA turns to the right.