Biology: Cell Structure I Nucleus Medical Media

Key Concepts:

• Cell membrane, cytoplasm, DNA
• Eukaryotic cells (organelles, nucleus)
• Prokaryotic cells (no nucleus, unicellular)
• Organelles (nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, vacuoles, lysosomes, mitochondria, chloroplasts, cytoskeleton)
• Chromatin, chromosomes, nucleolus
• Cellular respiration, photosynthesis
• Microfilaments, microtubules
• Cilia, flagella

Cellular Basics:

All cells, regardless of type, share three fundamental components:

• Cell membrane: A boundary separating the cell's interior from its external environment.
• Cytoplasm: A jelly-like fluid filling the cell, housing organelles and other cellular components.
• DNA: The cell's genetic material, dictating its functions and characteristics.

Eukaryotic Cells:

Eukaryotic cells are characterized by their complexity and the presence of membrane-bound organelles. Key features include:

• Organelles: Specialized structures within the cell, each performing specific functions.
• Nucleus: The control center of the cell, containing the DNA. Eukaryotic cells are found in plants and animals.

Prokaryotic Cells:

Prokaryotic cells are simpler in structure, lacking a nucleus and membrane-bound organelles. Key features include:

• Absence of Nucleus: Genetic material is present but not enclosed within a nucleus.
• Unicellularity: Prokaryotic cells are always single-celled organisms, such as bacteria.

Organelle Functions:

• Nucleus: Contains DNA in the form of chromatin (tangled, spread-out DNA) or chromosomes (condensed DNA during cell division). The nucleus also contains the nucleolus, where ribosomes are made.
• Ribosomes: Synthesize proteins, either freely floating in the cytoplasm or attached to the endoplasmic reticulum.
• Endoplasmic Reticulum (ER): A membrane-enclosed passageway for transporting materials.
  • Rough ER: Has ribosomes attached, involved in protein synthesis.
  • Smooth ER: Lacks ribosomes, involved in lipid synthesis and other functions.
• Golgi Apparatus (Golgi Body): Modifies, sorts, and packages proteins received from the ER. Proteins are customized by folding or adding lipids or carbohydrates.
• Vacuoles: Sac-like structures for storing various materials. Plant cells have a large central vacuole for water storage.
• Lysosomes: "Garbage collectors" containing enzymes to break down damaged or worn-out cell parts.
• Mitochondria: The "powerhouse" of the cell, performing cellular respiration to produce ATP, the cell's energy currency. Cells requiring more energy have more mitochondria.
• Chloroplasts: Found in plant cells, where photosynthesis occurs. Contain chlorophyll, a green pigment that captures sunlight.

Cellular Support and Structure:

• Cytoskeleton: Maintains cell shape and provides structural support.
  • Microfilaments: Thread-like structures made of protein.
  • Microtubules: Thin, hollow tubes.
• Cell Wall: Found in plant cells, providing shape, support, and protection. Animal cells lack a cell wall.

Specialized Cellular Structures:

• Cilia: Microscopic hair-like projections found on some cells, such as those lining the respiratory tract. Cilia move in waves to trap and expel inhaled particles.
• Flagella: Tail-like structures used for movement. Found in some bacteria and sperm cells.

Synthesis/Conclusion:

Cells are the fundamental units of life, categorized into eukaryotic and prokaryotic types. Eukaryotic cells, found in plants and animals, possess complex organelles, including a nucleus, while prokaryotic cells, such as bacteria, lack these structures. All cells share a cell membrane, cytoplasm, and DNA. Organelles like mitochondria are present in both plant and animal cells, while chloroplasts are unique to plant cells. Specialized structures like cilia and flagella enable specific functions in certain cell types.