Cell Biology Lesson 2: Cellular Organization

Three Main Parts of the Cell

• Plasma Membrane: Flexible barrier separating cell's interior from external environment; regulates substance entry and exit using the Fluid Mosaic Model.
• Cytoplasm: Gel-like substance within the cell containing organelles, excluding the nucleus.
• Nucleus: Largest cell structure; acts as the control center, storing genetic information necessary for synthesis.

Plasma Membrane

• Composed of lipids, carbohydrates, and proteins.
• Functions as a selective barrier, controlling the passage of ions and molecules.
• Important for cell signaling and communication with its environment.

Cell Theory

• Cells are the fundamental building blocks of all living organisms.
• All cells arise from the division of pre-existing cells.
• Cells are the smallest units that perform essential life functions.

Nucleus Structure

• Surrounded by a nuclear envelope; contains the nucleoplasm, chromatin, and nucleolus.
• Nucleolus: Site for assembling ribosomal subunits; contains DNA and RNA essential for ribosomal RNA synthesis.
• Chromatin: Composed of DNA, histone proteins, and RNA; organizes genetic material within the nucleus.

Nuclear Envelope and Pores

• Surrounding structure that maintains nuclear integrity and facilitates communication with the cytoplasm via nuclear pores.

Endoplasmic Reticulum

• Rough ER: Studded with ribosomes; modifies and packages proteins for transport.
• Smooth ER: Involved in lipid synthesis and carbohydrate metabolism.

Golgi Apparatus

• Functions in modifying, packaging, and distributing proteins and lipids for secretion or use within the cell.
• Cisternae: Series of fluid-filled cavities involved in these processes.

Lysosomes

• Contain powerful digestive enzymes; breakdown various biomolecules.
• Known as "suicide bags" due to their ability to digest worn-out organelles and cellular debris.

Peroxisomes

• Similar to lysosomes but smaller; involved in detoxifying harmful substances, particularly in the liver.

Mitochondria

• Powerhouses of the cell; site of ATP production through cellular respiration.
• Initially processes glucose in the cytosol before full conversion to ATP occurs within mitochondria.

Membrane Permeability

• Selectively permeable; nonpolar molecules (e.g., oxygen, carbon dioxide) easily pass through, while ions and large polar molecules (e.g., glucose) do not.

Transport Mechanisms

• Passive Transport: Substances move down their concentration gradient without energy (e.g., diffusion, facilitated diffusion).
• Active Transport: Substances move against their concentration gradient using energy (ATP).

Types of Diffusion

• Simple Diffusion: Movement of particles across a membrane without aid; occurs down the concentration gradient.
• Facilitated Diffusion: Requires transport proteins for movement but remains passive.
• Osmosis: Special case of diffusion concerning water across a semipermeable membrane.

Factors Affecting Diffusion Rate

• Concentration Gradient: Steeper gradients increase diffusion rates.
• Temperature: Higher temperatures lead to faster diffusion.
• Mass of Diffusing Substance: Smaller particles diffuse faster.

This quiz focuses on the cellular level of organization, specifically the three main parts of a cell: plasma membrane, cytoplasm, and nucleus. Test your knowledge on these essential cellular components and their functions in this engaging quiz.