Cellular Energy and Macromolecules: Study Notes for General Biology

Cellular Energy and Metabolism

Overview of Cellular Energy

Cells require energy to perform essential life processes, including growth, reproduction, and maintenance. This energy is primarily obtained through the breakdown of organic molecules, such as glucose, in metabolic pathways.

• Cellular Respiration: The process by which cells convert biochemical energy from nutrients into adenosine triphosphate (ATP), releasing waste products.

• Photosynthesis: The process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.

• Reverse Processes: Cellular respiration is essentially the reverse of photosynthesis in terms of reactants and products.

General Equation for Cellular Respiration:

$\mathrm{C_6H_{12}O_6} + 6\,\mathrm{O_2} \rightarrow 6\,\mathrm{CO_2} + 6\,\mathrm{H_2O} + \mathrm{ATP}$

• Glucose (C6H12O6): The primary fuel molecule for cellular respiration.

• ATP (Adenosine Triphosphate): The main energy currency of the cell.

General Equation for Photosynthesis:

$6\,\mathrm{CO_2} + 6\,\mathrm{H_2O} + \text{light energy} \rightarrow \mathrm{C_6H_{12}O_6} + 6\,\mathrm{O_2}$

• Photosynthesis stores energy in glucose, while cellular respiration releases energy from glucose.

ATP: The Energy Molecule

ATP (adenosine triphosphate) is the molecule that stores and transfers energy within cells.

• Structure: Composed of adenine, ribose (a sugar), and three phosphate groups.

• Function: Energy is released when ATP is hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate.

• Equation:

$\mathrm{ATP} + \mathrm{H_2O} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$

Macromolecules and Their Monomers

Overview of Biological Macromolecules

Biological macromolecules are large, complex molecules essential for life. They are typically formed by the polymerization of smaller subunits called monomers.

• Proteins: Polymers of amino acids.

• Carbohydrates: Polymers of monosaccharides (simple sugars).

• Lipids: Not true polymers, but composed of fatty acids and glycerol.

• Nucleic Acids: Polymers of nucleotides.

Monomers of Major Macromolecules

• Proteins: Monomers are amino acids.

• Carbohydrates: Monomers are monosaccharides (e.g., glucose).

• Lipids: Composed of fatty acids and glycerol (not true monomers, but building blocks).

• Nucleic Acids: Monomers are nucleotides (e.g., DNA and RNA).

Examples and Applications

• Glucose: A monosaccharide used in cellular respiration to produce ATP.

• Starch and Glycogen: Polysaccharides (carbohydrate polymers) used for energy storage in plants and animals, respectively.

• Collagen: A structural protein found in connective tissues.

• DNA: A nucleic acid that stores genetic information.

Comparison Table: Macromolecules and Their Monomers

Macromolecule	Monomer	Example	Main Function
Protein	Amino acid	Hemoglobin, Collagen	Structure, enzymes, transport
Carbohydrate	Monosaccharide (e.g., glucose)	Starch, Glycogen, Cellulose	Energy storage, structure
Lipid	Fatty acids & Glycerol	Triglycerides, Phospholipids	Energy storage, membranes
Nucleic Acid	Nucleotide	DNA, RNA	Genetic information

Additional Information

• Cellulose: A polysaccharide made of glucose monomers; provides structural support in plant cell walls.

• Reverse of Photosynthesis: Cellular respiration is often described as the reverse of photosynthesis, as it breaks down glucose to release energy, while photosynthesis builds glucose using energy.

• Energy Flow: Energy flows from the sun to producers (via photosynthesis) and then to consumers (via cellular respiration).

Additional info: Some content and terminology were inferred and expanded for clarity and completeness based on standard General Biology curriculum.