2.5 Organic Compounds Essential to Human Functioning
Organic Compounds Essential to Human Functioning
Nucleotides
Definition of Nucleotide:
A class of organic compounds composed of three subunits:
One or more phosphate groups.
A pentose sugar: either deoxyribose or ribose.
A nitrogen-containing base: adenine, cytosine, guanine, thymine, or uracil.
Functionality of Nucleotides:
Nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate (ATP).
Nucleic Acids
Differences in Nucleic Acids:
The nucleic acids differ based on the type of pentose sugar they contain.
Deoxyribonucleic Acid (DNA):
Contains deoxyribose (characterized by having one less oxygen atom than ribose), one phosphate group, and one nitrogen-containing base (choices: adenine, cytosine, guanine, thymine).
DNA stores genetic information.
Ribonucleic Acid (RNA):
Contains ribose, one phosphate group, and one nitrogen-containing base (choices: adenine, cytosine, guanine, uracil).
RNA helps manifest the genetic code as proteins.
Classification of Nitrogen-Containing Bases:
Purines:
Adenine and guanine, characterized as nitrogen-containing molecules with a double-ring structure that accommodates several nitrogen atoms.
Pyrimidines:
Cytosine, thymine (found only in DNA), and uracil (found only in RNA), characterized as nitrogen-containing bases with a single-ring structure.
Backbone Structure of Nucleic Acids:
Bonds formed by dehydration synthesis between the pentose sugar of one nucleotide monomer and the phosphate group of another form a "backbone" to which the nitrogenous bases protrude.
In DNA, two such backbones attach at their protruding bases via hydrogen bonds, resulting in a structure known as a double helix.
Gene Sequence and Function:
The sequence of nitrogen-containing bases within a strand of DNA forms the genes that act as a molecular code, instructing cells in the assembly of amino acids into proteins.
Humans possess almost 22,000 genes within their DNA, contained in 46 chromosomes located inside the nucleus of each cell (with the exception of red blood cells which lose their nuclei during development).
Genes carry unique genetic codes vital for body development, and except for identical twins, each individual has a unique genetic composition.
Messenger RNA (mRNA)
Role of Messenger RNA:
Produced during protein synthesis to carry genetic instructions from DNA to the cell's protein-manufacturing sites in the cytoplasm, known as ribosomes.
Adenosine Triphosphate (ATP)
Structure of ATP:
Composed of a ribose sugar, an adenine base, and three phosphate groups.
Classified as a high-energy compound due to the substantial amount of potential energy stored within the two covalent bonds linking its three phosphates.
Energy Utilization:
The energy released from these high-energy bonds fuels various bodily activities, including:
Muscle contraction.
Transport of substances in and out of cells.
Anabolic chemical reactions.
Hydrolysis of ATP:
When a phosphate group is cleaved from ATP, the products are adenosine diphosphate (ADP) and inorganic phosphate (Pi), which can be represented by the reaction:
The removal of a second phosphate group results in adenosine monophosphate (AMP) and two phosphate groups, releasing energy stored in the phosphate-phosphate bonds.
This reaction is reversible; for instance, ADP can undergo phosphorylation where a phosphate group is added back, resulting in ATP.
Phosphorylation Process:
Phosphorylation is defined as the addition of a phosphate group to an organic compound, here resulting in the regeneration of ATP.
The energy released during hydrolysis must be invested to drive dehydration synthesis for this to occur.
Phosphate Transfer Example:
When glucose first enters a cell, a phosphate group from ATP is transferred to glucose, forming glucose phosphate (C₆H₁₂O₆—P) and ADP.
This phosphorylation allows glucose to be stored as glycogen or metabolized for immediate energy.