Biomolecule Basics: Page 1 Transcript Notes

Amino Acids

• Amino acids are the monomers of proteins.
• There are 20 standard amino acids.
• Basic molecular structure:
  • Central (alpha) carbon connected to four groups: amino group (-NH₂), carboxyl group (-COOH), a hydrogen atom, and an R group (side chain).
  • Atoms typically involved include hydrogen (H), carbon (C), nitrogen (N), and oxygen (O); some side chains also contain sulfur (S).
• Side chain (R group) determines the properties of each amino acid (polarity, charge, size).
• The amino group and carboxyl group enable peptide bond formation during protein synthesis.

Peptide Bonds, Dipeptides, and Dehydration/Hydrolysis

• Dehydration synthesis (condensation reaction) forms a covalent bond between amino acids with the removal of water (H₂O).
  • General idea: joining the carboxyl carbon of one amino acid to the amino nitrogen of the next amino acid.
  • Resulting bond is a peptide bond (-CO-NH-).
• Reaction example (two amino acids forming a dipeptide):
  $\text{AminoAcid}<em>1{-}COOH + \text{AminoAcid}</em>2{-}NH<em>2 \rightarrow \text{AminoAcid}</em>1{-}CO{-}NH{-}\text{AminoAcid}<em>2 + H</em>2O$
• A dipeptide is formed when two amino acids are linked by a single peptide bond.
• Hydrolysis is the reverse process: water is added to break a bond (e.g., a peptide bond) to separate monomers.
  • General idea: disassembly of polymers into monomers via water addition.

Carbohydrates: Glycosidic Bonds and Disaccharides

• Glycosidic bonds join carbohydrates (sugars) together.
• When two glucose units join via a glycosidic bond, a disaccharide is formed (e.g., maltose is two glucose units linked by an α-1,4-glycosidic bond).
  • Example (conceptual): $\text{Glucose} + \text{Glucose} \rightarrow \text{Disaccharide} + H_2O$
• Hydrolysis of a glycosidic bond breaks the bond and yields two monosaccharides, typically with the incorporation of water:
  • Example: $\text{Disaccharide} + H<em>2O \rightarrow \text{Monosaccharide}</em>1 + \text{Monosaccharide}_2$
• Key terms:
  • Monosaccharide: single sugar unit (e.g., glucose).
  • Disaccharide: two sugar units (e.g., maltose).

Nucleotides and Ribose

• A nucleotide is the fundamental unit of nucleic acids.
• Components of a nucleotide:
  • Nitrogenous base (e.g., adenine, cytosine, guanine, thymine, uracil).
  • Five-carbon sugar (pentose): ribose in RNA; deoxyribose in DNA.
  • Phosphate group(s).
• The transcript references nucleotides as: base, ribose, and phosphate.
• Nucleotide formation (concept): base + ribose + phosphate → nucleotide.
• Note on ribose: ribose is the sugar component of RNA.

Lipids and Triglycerides

• Triglycerides are a type of lipid formed by esterification of glycerol with three fatty acids.
• Formation reaction (three ester bonds formed by removing water):
  $\text{Glycerol} + 3\,\text{Fatty Acids} \rightarrow \text{Triglyceride} + 3\,H_2O$
• The transcript mentions triglycerides in the context of lipid structure; lipids are characterized by hydrophobic properties and energy storage roles.

Atomic Structure

• Atoms are composed of subatomic particles organized into a nucleus and electron cloud.
• In the nucleus:
  • Protons (p⁺) are positively charged.
  • Neutrons (n⁰) are neutral.
  • The nucleus contains protons and neutrons (collectively called nucleons).
• Electrons (e⁻) are negatively charged and orbit the nucleus in electron orbitals.
• Common elements mentioned in biomolecules include hydrogen (H), carbon (C), nitrogen (N), oxygen (O), and phosphate (P) as part of functional groups (e.g., in nucleotides).
• Summary:
  • Protons: positive charge; located in the nucleus.
  • Neutrons: neutral; located in the nucleus.
  • Electrons: negative charge; located in orbitals surrounding the nucleus.

Connections and Significance (Overview)

• Biomolecules form the basis of structure and function in biological systems:
  • Amino acids assemble into proteins via peptide bonds; the sequence and composition determine protein structure and function.
  • Carbohydrates provide energy storage and structural roles; glycosidic bonds link sugar units to form polymers.
  • Nucleotides store and transmit genetic information; sugars (ribose or deoxyribose) and phosphate groups link into nucleic acids.
  • Lipids like triglycerides store energy and form cellular membranes; ester bonds connect glycerol to fatty acids.
  • Atomic structure underpins chemical bonding, reactivity, and the properties of biomolecules.

Quick Concept Equations (for review)

• Dehydration synthesis of amino acids (to dipeptide):
  $\text{AminoAcid}<em>1{-}COOH + \text{AminoAcid}</em>2{-}NH<em>2 \rightarrow \text{AminoAcid}</em>1{-}CO{-}NH{-}\text{AminoAcid}<em>2 + H</em>2O$
• Dipeptide formation (peptide bond): shown in the same equation above.
• Glycosidic bond formation (glucose + glucose → disaccharide + H₂O):
  $\text{Glucose} + \text{Glucose} \rightarrow \text{Disaccharide} + H_2O$
• Glycosidic bond hydrolysis (disaccharide + H₂O → 2 monosaccharides):
  $\text{Disaccharide} + H<em>2O \rightarrow \text{Monosaccharide}</em>1 + \text{Monosaccharide}_2$
• Nucleotide composition (base + ribose + phosphate):
  $\text{Base} + \text{Ribose} + \text{Phosphate} \rightarrow \text{Nucleotide}$
• Triglyceride synthesis (glycerol + 3 fatty acids → triglyceride + 3 H₂O):
  $\text{Glycerol} + 3\,\text{Fatty Acids} \rightarrow \text{Triglyceride} + 3\,H_2O$
• Atomic structure summary: Protons in nucleus, neutrons in nucleus, electrons in orbitals around the nucleus; charge signs: p⁺ (+), n⁰ (neutral), e⁻ (-).