مقدمة في علم الأحياء الخلوية

Introduction to Cell Biology

• Cell biology is the study of the structure and function of cells.
• Cells are the basic units of life.
• All living organisms are composed of cells.
• Cells vary greatly in structure and function, but share common features.

Cell Structure

• Cells are enclosed by a cell membrane.
• Cell membrane is selectively permeable, controlling the passage of substances into and out of the cell.
• Some cells have cell walls outside the membrane.
• Examples of cell structures include:
  • Nucleus: Contains the cell's DNA, controls cellular activities.
  • Cytoplasm: The jelly-like substance filling the cell, contains organelles.
  • Mitochondria: Site of cellular respiration, generates energy.
  • Ribosomes: Site of protein synthesis.
  • Endoplasmic reticulum: Involved in protein and lipid synthesis.
  • Golgi apparatus: Processes and packages proteins.
  • Lysosomes: Contain enzymes that break down waste materials.
  • Vacuoles: Store water and nutrients.
  • Chloroplasts (plant cells): Site of photosynthesis.
  • Cytoskeleton: Provides structure and support for the cell.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic cells are simpler, smaller, and lack a nucleus and other membrane-bound organelles.
• Examples: Bacteria and archaea
• Eukaryotic cells are larger and more complex, containing a nucleus and membrane-bound organelles.
• Examples: Animal cells, plant cells, fungi, protists.

Cell Membrane

• Composed primarily of phospholipids arranged in a bilayer.
• Also contains proteins and cholesterol.
• Fluid mosaic model describes the structure of the membrane.
• The membrane is selectively permeable, regulating movement of substances across it, and allowing the cell to maintain homeostasis.
• Transport across the membrane includes passive transport (diffusion, osmosis) and active transport (requiring energy).

Cell Function

• Cellular respiration: Process of breaking down glucose to produce ATP (energy).
• Photosynthesis (plant cells): Conversion of light energy into chemical energy (glucose).
• Cell division: Process of creating new cells (mitosis, meiosis).
• Protein synthesis: The process of building proteins according to genetic instructions.
• Signal transduction: Cells responding to signals from other cells.

Cell Specialization and Tissues

• Different cell types have different structures and functions.
• Specialized cells work together as tissues, organs, and organ systems to perform complex functions.

Cellular Processes

• Metabolism: All chemical reactions in the cell.
• Respiration: Process of releasing energy from food.
• Growth and development: Controlled by gene expression and cell division.
• Homeostasis: Maintaining a stable internal environment.
• Cell signaling: Communication between cells.

Cell Cycle and Cell Division

• Consists of interphase (growth and DNA replication) and mitotic phase (mitosis and cytokinesis).
• Mitosis: Division of the nucleus into two identical nuclei.
• Cytokinesis: Division of the cytoplasm.

Cellular Adaptations

• Cells adjust their structure and function in response to their environment.
• Adaptations can include changes in size, shape, or the production of specific proteins.

يستعرض هذا الاختبار أساسيات علم الأحياء الخلوية، والذي يدرس بنية الخلايا ووظيفتها. تتكون جميع الكائنات الحية من خلايا، وتشارك الخلايا هيكلاً ووظائف مشابهة، ولكنها تختلف في ميزاتها. كذلك، نناقش مكونات الخلية المختلفة مثل النواة والميتوكندريا.