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Introduction to Biochemistry — Video Notes
Introduction to Biochemistry
What biochemistry studies
Biochemistry examines the chemical and physical processes that make life possible. It connects biological functions—such as respiration, growth, inheritance, and disease—to the molecules and reactions occurring inside organisms.
A biochemist asks molecular-level questions:
What is this protein’s structure and function?
Which enzyme controls a reaction or pathway?
How does a DNA change alter a protein?
How can a molecular defect produce disease?
Chemical composition of life
The body is made primarily of a small set of elements:
Oxygen: about 65%
Carbon: about 18%
Hydrogen: about 10%
Nitrogen: about 3%
Calcium: about 2%
Other elements: about 2%
These elements form the molecules required for cells to survive and function.
Levels of biological organization
Life can be understood as a hierarchy:
\[
\text{Elements} \rightarrow \text{Biomolecules} \rightarrow \text{Organelles} \rightarrow \text{Cells}
\]
Biomolecules (macromolecules)
The four major groups are:
Proteins — perform structural, transport, signaling, and catalytic roles.
Nucleic acids — DNA and RNA; store and use genetic information.
Carbohydrates — provide energy and structural support.
Lipids — store energy, form membranes, and participate in signaling.
Biomolecules work together to form organelles. Organelles are structures inside cells, and the cell is the basic structural and functional unit of life.
Case study: red blood cells and hemoglobin
Red blood cells illustrate the biochemist’s approach. Their main role is oxygen transport, which depends on hemoglobin, a protein.
Hemoglobin contains a heme group. At its center is an iron atom held within a porphyrin ring. The iron binds oxygen, allowing hemoglobin to carry oxygen through the bloodstream.
Studying this system involves examining:
Hemoglobin’s protein structure
The heme group
How iron binds oxygen
How changes in DNA can change hemoglobin function
From DNA mutation to disease: sickle cell anemia
Sickle cell anemia demonstrates how a tiny molecular change can have body-wide effects.
A mutation changes the DNA sequence.
The mutation changes the amino-acid sequence of hemoglobin.
In the example, glutamine is replaced by valine.
The altered hemoglobin functions abnormally.
Red blood cells become misshapen and can obstruct blood vessels.
The key principle is:
\[
\text{DNA change} \rightarrow \text{altered protein} \rightarrow \text{altered cell function} \rightarrow \text{disease}
\]
Why biochemistry matters
Biochemistry helps explain disease at its source: molecules. This knowledge supports:
Drug discovery and development
Genetic disease research
Pharmacology
Immunology
Pathology
Biotechnology and laboratory research
Key terms
Biochemistry: Study of chemical processes in living organisms.
Biomolecule/macromolecule: Large molecule essential for life, such as a protein, nucleic acid, carbohydrate, or lipid.
Organelle: Specialized internal cell structure.
Enzyme: Usually a protein that speeds up a chemical reaction.
Heme group: Iron-containing component of hemoglobin that binds oxygen.
Porphyrin ring: Ring-shaped structure surrounding iron in heme.
Mutation: Change in a DNA sequence.
Sickle cell anemia: Genetic disease in which altered hemoglobin disrupts red-blood-cell shape and function.
Fast review
Biochemistry links chemistry to biological function.
The major biological macromolecules are proteins, nucleic acids, carbohydrates, and lipids.
Organization progresses from elements to biomolecules, organelles, and cells.
Molecular changes, including DNA mutations, can alter proteins and cause disease.
Understanding molecular mechanisms is central to developing treatments.