Biochemistry: A Comprehensive Study Guide, Study notes of Biochemistry

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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