Overview
This lecture introduces the fundamentals of biochemistry with a focus on the structure and components of eukaryotic cells, including their organelles and functions.
Introduction to Biochemistry
- Biochemistry is the study of cells, their components, and biological processes.
- Understanding biochemistry helps find solutions for diseases like HIV and sickle cell anemia.
- Applications include development of medications such as PrEP for HIV prevention.
Eukaryotic Cells: Overview
- Eukaryotic cells have organelles (mini "factories") such as the nucleus and mitochondria.
- Typical diameter is 10–100 micrometers, larger than prokaryotic cells.
- Present in animals, plants, and protozoa.
- Animal cells lack cell walls and have only a plasma membrane; plant cells have both.
Plasma Membrane and Compartmentalization
- Plasma membrane is a chemical barrier made of lipids (fats) and proteins.
- Compartmentalization creates specialized regions (organelles) for specific functions, increasing efficiency.
Cytoplasm and Cytoskeleton
- Cytoplasm (cytosol) is a jelly-like aqueous environment inside the plasma membrane.
- About 20–30% of cytoplasm is protein, supporting metabolism (e.g., glycolysis).
- Cytoskeleton is a 3D network of protein fibers that gives shape and structure to the cell and organelles, and enables cell movement.
Nucleus
- Largest cell organelle, bound by a double membrane.
- Stores genetic information and synthesizes most DNA and some RNA.
Endoplasmic Reticulum (ER) and Ribosomes
- ER is a network of interconnected, membrane-bound vesicles attached to the nuclear membrane.
- Smooth ER synthesizes lipids (fats); Rough ER synthesizes proteins via ribosomes.
- Ribosomes are made of RNA and proteins, not membrane-bound, and perform protein synthesis.
Vesicles
- Vesicles are small membrane-bound sacs that transport materials within the cell.
- Function as transport vehicles for proteins, fats, and enzymes.
Lysosomes
- Lysosomes act as waste disposal, degrading old or defective proteins and other polymers.
- Contain acidic enzymes (pH ~5) that break polymers into monomers (e.g., proteins into amino acids).
Golgi Complex
- Golgi complex consists of flattened vesicles made from lipids, proteins, and sugars.
- Processes, modifies, and distributes proteins and fats throughout the cell, working closely with the ER.
Mitochondria
- Mitochondria have inner and outer membranes and perform oxidative energy production.
- Generate ATP (adenosine triphosphate), the cell's energy currency.
- Possess their own circular DNA and genome, supporting the endosymbiotic hypothesis of origin.
- Muscle cells contain many mitochondria to meet high energy demands.
Key Terms & Definitions
- Biochemistry — Study of cells and their molecular processes.
- Eukaryotic cell — Cell with membrane-bound organelles and a nucleus.
- Plasma membrane — Lipid and protein barrier surrounding the cell.
- Compartmentalization — Separation of cell functions into organelles.
- Cytoplasm (cytosol) — Jelly-like fluid inside the cell where metabolism occurs.
- Cytoskeleton — Protein network providing cell shape and organelle structure.
- Nucleus — Organelle storing genetic material (DNA/RNA).
- Endoplasmic reticulum (ER) — Organelle synthesizing lipids (smooth ER) or proteins (rough ER).
- Ribosome — Molecular machine that synthesizes proteins.
- Vesicle — Membrane-bound sac transporting substances.
- Lysosome — Organelle degrading waste and polymers into monomers.
- Golgi complex — Organelle processing and shipping proteins and lipids.
- Mitochondrion — Organelle producing ATP; has its own DNA.
- ATP (adenosine triphosphate) — Main energy carrier in the cell.
- Polymer — Large molecule made of repeating units (monomers).
- Monomer — Basic building block of a polymer.
- Endosymbiotic hypothesis — Theory that mitochondria originated from bacteria engulfed by ancient cells.
Action Items / Next Steps
- Review organelle functions and their distinguishing features.
- Prepare for questions on cell anatomy and roles of key organelles.