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Biochemistry: A Comprehensive Study Guide, Study notes of Biochemistry

Proteins. • Contain C, H, O, N, and sometimes S and P. • Amino acids (20 types) o Monomers in proteins. – Joined by covalent bonds called peptide bonds.

Typology: Study notes

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Biochemistry

Biochemistry

  • Study of chemical composition and reactions of living matter o Biological chemistry
  • Organic compounds

o Molecules that contain carbon

  • Except CO 2 and CO (considered inorganic)
  • Carbon is electroneutral o Shares electrons; never gains or loses them o Forms four covalent bonds with other elements
  • Inorganic compounds

o All other compounds, not containing carbon

  • Ex: water, salts, acids, and bases

Organic Compounds

  • Attached functional groups

o Change physical and chemical properties

  • Synthesized by

o Dehydration synthesis

  • Broken down by

o Hydrolysis reactions

Dehydration synthesis and removal of H from the other at the site of bond formation.^ Monomers are joined by removal of OH from one monomer

Monomer 1

Hydrolysis

Monomers linked by covalent bond

Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other.

Example reactions Dehydration synthesis of sucrose and its breakdown by hydrolysis

Glucose Fructose

Water is released

Water is consumed Sucrose

Monomer 2

Monomer 1 Monomer 2 Monomers linked by covalent bond

Figure 2.14 Dehydration synthesis and hydrolysis.

Monosaccharides

  • Simple sugars containing three to seven C atoms
  • (CH 2 0)n – general formula; n = # C atoms
  • Monomers of carbohydrates
  • Important monosaccharides
    • Pentose sugars
      • Ribose and deoxyribose
    • Hexose sugars
      • Glucose (blood sugar)

Figure 2.15a Carbohydrate molecules important to the body.

Glucose Fructose Galactose Deoxyribose Ribose

Disaccharides

  • Double sugars
  • Too large to pass through cell membranes
  • Important disaccharides
    • Sucrose, maltose, lactose

Disaccharides Example^ Consist of two linked^ monosaccharides Sucrose, maltose, and lactose (these disaccharides are isomers)

Glucose Fructose Glucose Glucose Galactose Glucose Sucrose Maltose Lactose Figure 2.15b Carbohydrate molecules important to the body.

  • Contain C, H, O, and sometimes P
  • Insoluble in water
  • Main types:
    • Triglycerides o aka neutral fats
    • Phospholipids
    • Steroids
    • Eicosanoids

Lipids

Triglycerides

(aka Neutral Fats)

  • Called fats when solid and oils when liquid
  • Composed of three fatty acids bonded to a

glycerol molecule

Triglyceride formation Three fatty acid chains are bound to glycerol by dehydration synthesis.

Glycerol 3 fatty acid chains (^) Triglyceride, or neutral fat 3 water molecules

  • (^) +

Figure 2.16a Lipids.

Triglycerides (Neutral Fats)

Main functions in human body:

  • Energy storage
  • Insulation
  • Protection

Phospholipids

  • Modified triglycerides:
    • Glycerol + two fatty acids and a phosphorus (P) group
  • “Head” and “tail” regions have different properties
  • Important in cell membrane structure

“Typical” structure of a phospholipid molecule Two fatty acid chains and a phosphorus-containing group are attached to the glycerol backbone. Example Phosphatidylcholine

Nonpolar “tail” (schematic phospholipid)

Polar “head”

Phosphorus-containing group (polar “head”) Glycerol backbone^ 2 fatty acid chains (nonpolar “tail”) Figure 2.16b Lipids.

Proteins

  • Contain C, H, O, N, and sometimes S and P
  • Amino acids (20 types)

o Monomers in proteins

  • Joined by covalent bonds called peptide bonds
  • Contain o Amine group (--NH 2 ) o Acid group (--COOH)
  • Can act as either acid or base
  • Vary by “R group”

Generalized structure of all amino acids.

Glycine is the simplest amino acid. (an acidic amino^ Aspartic acid acid) has an acid group (—COOH) in the R group.

Lysine (a basic amino acid) has an amine group ( the R group.—NH 2 ) in

Cysteine (a basic amino acid) has a sulfhydryl (—SH) group in the R group, which suggests that this amino acid is likely to participate in intramolecular bonding.

Amine group group^ Acid

Figure 2.17 Amino acid structures.

  • Proteins vary widely in structure and function
    • All are constructed from different combinations of 20 common amino acids
  • Two major factors contribute to uniqueness
    • Each amino acid has distinct properties
      • R groups
    • Sequence of amino acids bound together
      • Varying combinations lead to distinct proteins
      • Changes in types or positions of amino acids
  • Sequence also affects levels of protein structure
  • Overall structure determines its biological function

Proteins

Primary structure: The sequence of amino acids forms the polypeptide chain.

Amino acid Amino acid Amino acid Amino acid Amino acid

Figure 2.19a Levels of protein structure.

Structural Levels of Proteins