ANAT lecture 5 (03-10)

Overview of Cells and Macromolecules

• Cells are the basic units of life, composed of macromolecules - proteins, lipids, carbohydrates, and nucleic acids.

• These macromolecules are organic compounds essential for cellular structure and function.

• Cells originate from the fusion of a sperm and an egg, forming a zygote, which is the fertilized egg.

Cellular Differentiation

• Defining Cellular Differentiation: The process where a single cell develops into many specialized cells (e.g., nerve, muscle, etc.).

• Specialized cells perform distinct functions throughout the body, such as forming brain tissue or connecting bones through muscle.

Cell Structure

Plasma Membrane:

• The plasma membrane (or cell membrane) surrounds the cell, acting as a boundary between the intracellular and extracellular environments.

• Extracellular Area: The region outside the cell, including

  • Extracellular Fluid: Fluid in the extracellular area.

  • Extracellular Matrix: The structural network outside the cell.

• Cytoplasm: Refers to all the contents within the cell membrane excluding the nucleus, consisting of:

  • Cytosol: The fluid component of the cytoplasm.

  • Organelles: Tiny organs within the cell that perform specific functions.

Membranous vs. Non-Membranous Organelles

• Membranous Organelles: Surrounded by membranes, separating their internal environment from the cytosol (e.g., nucleus, endoplasmic reticulum).

• Non-Membranous Organelles: In direct contact with cytosol (e.g., ribosomes).

Nucleus

• The nucleus is the cell's control center, regulating its activities and metabolism.

• Nuclear Envelope: A double membrane that encloses the nucleus, separating nucleoplasm from cytoplasm.

• Nucleoplasm: The fluid inside the nucleus, distinct from cytoplasm.

• One of the main roles is to store genetic information (DNA).

• Nucleolus: A structure within the nucleus responsible for producing ribosomes, which are crucial for protein synthesis.

Endoplasmic Reticulum (ER)

• Exist in two forms: Rough ER and Smooth ER.

• Rough ER: Studded with ribosomes, primarily synthesizes proteins.

• Smooth ER: Lacks ribosomes and synthesizes lipids and carbohydrates.

• Functions of the ER: Combine (synthesize), store products, and detoxify substances, especially in the liver.

Ribosomes

• Ribosomes can either be Attached (Fixed) to the rough ER or Free in the cytoplasm.

• Fixed Ribosomes: Synthesize proteins intended for secretion or membrane integration.

• Free Ribosomes: Produce proteins for use within the cell.

Cytoskeleton

• Made of proteins, providing structure and support to the cell. It consists of three types:

  • Microfilaments: Smallest, assist in cell movement and shape (e.g., microvilli).

  • Intermediate Filaments: Intermediate in size, provide tensile strength and durability.

  • Microtubules: Largest, involved in cell shape and movement (e.g., cilia for mucus movement).

Golgi Apparatus

• Processes, alters, and packages proteins synthesized by the ER.

• Proteins from Rough ER destined for secretion go to the Golgi for modification and then to the plasma membrane or outside the cell.

Lysosomes and Peroxisomes

• Lysosomes: Vesicles containing digestive enzymes to break down waste and cellular debris.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

Glycocalyx

• A sugar coat on the plasma membrane that aids cell recognition and protects against mechanical stress.

Conclusion

• Understanding cell structure, differentiation, and the roles of organelles is crucial for grasping cell biology and its functions.