Essential Principles of Biochemistry and Cellular Metabolism

ATP: The Cellular Energy Currency

ATP acts as an intermediary between reactions that release energy and those that consume it. It is formed by the union of an energy-rich molecule and a phosphate group. ATP is synthesized in the inner mitochondrial membrane through the process of oxidative phosphorylation.

Aerobic Respiration

This is the process by which molecules are oxidized for energy, using oxygen as the final electron acceptor.

Catalysts and Enzymes

Catalyst

A substance that facilitates a chemical reaction in tiny quantities. It is not consumed, does not provide energy, and functions by lowering the activation energy.

Enzymes

Biological catalysts that regulate the speed of chemical reactions within organisms.

Enzymatic Digestion

Enzymes form an enzyme-substrate complex to produce a final product. Enzymes are highly specific, typically catalyzing reactions with only one specific substrate.

Cofactors, Coenzymes, and Vitamins

To be active, protein enzymes often require the presence of a non-protein component:

• Cofactor: A non-metallic ion.
• Coenzyme: An organic substance.

The union between an enzyme and a coenzyme is often superficial and ephemeral, whereas a stable union occurs with a prosthetic group. Vitamins are essential substances that the body cannot produce in sufficient quantities, yet they are required for basic cellular functions.

Enzyme Regulation

Enzyme Inhibition

Inhibitors can reduce the speed of a reaction or stop it entirely. The action of enzymes can be significantly affected by these inhibitors.

Enzyme Kinetics

The reaction rate depends on the concentration of both the enzyme and the substrate. If the enzyme concentration is constant, the reaction rate varies with the substrate concentration.

Biomolecules

Carbohydrates

Organic biomolecules formed by CHONPS, also known as polyhydroxyaldehydes. They are present in all cells and serve as the primary energy source. Glucose is the substance from which organisms obtain energy. Polymers of glucose include:

• Starch: Energy reserve in plants.
• Glycogen: Energy reserve in animals.

Carbohydrates also serve structural functions and are components of other biomolecules.

Monosaccharides

Simple carbohydrates with the formula (CH2O)n. They are solid, white, water-soluble substances with a sweet taste, classified as either aldoses or ketoses.

Lipids

Formed from CHONPS, these high-molecular-weight compounds are insoluble in water but soluble in organic solvents. They contain organic acids linked to an alcohol group and constitute a heterogeneous group with the following functions:

• Reservation: Stored in adipose tissue (animals) and seeds (plants).
• Structural: Components of the cell membrane lipid bilayer.
• Regulatory: Includes fat-soluble vitamins and hormones.

Fatty Acids

Lipid components characterized by their bonds:

• Saturated: Linked by single bonds.
• Unsaturated: Contain at least one double bond.