B1.1.1: Chemical properties of a carbon atom allow for the formation of diverse compounds upon which life is based.
B1.1.2: Production of macromolecules by condensation reactions that link monomers to form a polymer.
B1.1.3: Digestion of polymers into monomers by hydrolysis reactions.
ORGANIC COMPOUNDS
Living organisms are composed of organic compounds.
An organic compound: contains carbon and is found in living things (certain exceptions exist, including CO2 and carbonates).
Carbon atoms can form four covalent bonds, allowing for a diversity of stable carbon compounds to exist.
MONOMERS → POLYMERS
Complex organic molecules may be comprised of smaller recurring subunits called monomers.
Monomeric subunits might not be identical but will share the same basic structural characteristics.
Carbohydrates, nucleic acids, and proteins are all composed of monomers.
Lipids do not contain monomers but may be comprised of distinctive subunits (e.g., triglycerides are made up of glycerol and three fatty acid chains).
METABOLISM
Metabolism describes the totality of chemical processes that occur within a cell to maintain life.
These metabolic processes provide a source of energy for biological processes.
Enable the synthesis and assimilation of cellular materials for use within the cell.
Metabolic reactions can broadly be described as being either anabolic or catabolic:
Anabolism:
Smaller compounds are combined to form larger compounds.
In the case of organic compounds, this involves condensation.
Water is released as a by-product of condensation reactions.
Catabolism:
Large compounds are broken down into smaller compounds.
In the case of organic compounds, this involves hydrolysis.
Water is required as an input for hydrolysis reactions.
ORGANIC MOLECULES
4 classes of organic compounds found in cells: carbohydrates, lipids, nucleic acids, and proteins.
Carbohydrates:
Used primarily as a short-term energy source (e.g., glucose).
Also involved in cellular structure (e.g., cellulose in plant cell walls) and signaling (membrane receptors are often glycoproteins).
Lipids:
Primary component of cell membranes (e.g., phospholipids).
Also involved in structure (waxes), cellular signaling (steroid hormones), and as a long-term energy source (e.g., triglycerides).
Nucleic Acids:
Function as a genetic blueprint for cellular activity.
DNA serves as a master copy, while RNA functions as a transient copy used to synthesize proteins (via transcription and translation).
Proteins:
Serve a wide variety of functions within a cell.
Including structure (e.g., collagen), signaling (e.g., peptide hormones), immunity (e.g., antibodies), and maintaining metabolic control (e.g., enzymes).
CARBOHYDRATES
Carbohydrates are comprised of monomeric units called monosaccharides.
These subunits form ringed structures that are covalently combined by condensation polymerization to form polysaccharides.
Glucose is an example of a monosaccharide used as an energy source within the cell.
It can form a variety of polymers, including glycogen (energy storage in animals), starch (storage in plants), and cellulose (structural component within plant cell walls).
Ribose is another example of a monosaccharide that functions as a core component of all nucleic acids (RNA contains ribose, while DNA contains the modified form – deoxyribose).
LIPIDS
Lipids are non-polar compounds that typically include long chains of hydrocarbons called fatty acids.
They do not contain monomers but may be composed of distinct subunits.
Triglycerides consist of a glycerol subunit combined with three fatty acid chains (via condensation reactions) and function as a source of long-term energy storage within a cell.
Phospholipids have only two fatty acid chains attached to the glycerol but include a polar phosphate group which makes the molecule amphipathic (possessing both hydrophilic and hydrophobic properties).
Phospholipids function as the primary component of membranes.
Steroids (such as cholesterol) do not consist of any subunits and are composed of four fused carbon rings.
NUCLEIC ACIDS
Nucleic acids are composed of monomeric subunits called nucleotides.
Each nucleotide contains a nitrogenous base attached to a backbone consisting of a sugar and a phosphate molecule.
Nucleotides are joined together by condensation polymerization to form long polymeric chains.
The bases protrude from the sugar-phosphate backbone to form a sequence that functions as a code for protein assembly.
DNA functions as a master copy, while RNA serves as a transient copy that plays an active role in the manufacturing of proteins.
PROTEINS
Proteins are composed of long chains of monomers called amino acids.
These amino acids are joined together via condensation polymerization to form polypeptide chains.
There are 20 different amino acids, and their order in a polypeptide sequence determines the overall shape and biological properties of the resulting protein.
Most polypeptide chains contain between 50 – 2000 amino acid residues.
Organisms can produce a huge range of possible proteins with a wide variety of functions.
Protein sequences are encoded by nucleic acids, and so proteins function to enact the genetic instructions of a cell.
INORGANIC MOLECULES
Organic compounds are formed from inorganic sources and may create inorganic byproducts if digested.
All organic compounds contain carbon (C), hydrogen (H), and oxygen (O) in varying ratios.
Nucleic acids and proteins always possess nitrogen (N) while nucleic acids also contain phosphorus (P), and proteins may contain sulfur (S) – depending on the specific amino acids present in a polypeptide.
Inorganic molecules also play important roles in the functioning of the cells that comprise living organisms.
Oxygen gas (O2) is required for aerobic cell respiration (producing ATP from the breakdown of glucose).
Carbon dioxide gas (CO2) is used by plants to synthesize vital organic molecules (like carbohydrates).
Water (H2O) comprises ~70% of the cell’s internal environment and functions as a transport medium.
Trace minerals (e.g., Na+, K+, Cl–) are necessary for maintaining survival in multicellular organisms.