Cell Biology Overview

Basic Characteristics of All Cells

• Smallest Living Units: Cells are the smallest units of life in organisms.
• Common Features:
  • Cell Membrane: Separates the cell from its environment.
  • Cytoplasm: Jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Categories of Cells

• Eukaryotic Cells:
  • Contain organelles, including a nucleus.
  • Found in advanced organisms such as plants and animals.
• Prokaryotic Cells:
  • Lack a nucleus and membrane-enclosed organelles.
  • Genetic material is not contained within a nucleus.
  • Typically unicellular organisms, such as bacteria.

Organelles and Their Functions

• Nucleus:
  • Control center containing DNA.
  • DNA is in the form of chromatin; condenses into chromosomes during cell division.
  • Contains the nucleolus, where ribosomes are made.
• Ribosomes:
  • Synthesize proteins.
  • Can be free in cytoplasm or attached to the endoplasmic reticulum (ER).
• Endoplasmic Reticulum (ER):
  • Rough ER: Has ribosomes attached, involved in protein synthesis.
  • Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification.
• Golgi Apparatus:
  • Processes and packages proteins and other materials.
  • Modifies proteins by folding them or adding other molecules.
• Vacuoles:
  • Sac-like structures for storage (e.g., water in plant cells).
• Lysosomes:
  • Break down waste material and cellular debris.
  • Contain enzymes for breaking down damaged cell parts.
• Mitochondria:
  • Powerhouse of the cell, creates ATP via cellular respiration.
  • Cells needing more energy have more mitochondria.
• Cytoskeleton:
  • Maintains cell shape.
  • Composed of microfilaments and microtubules.
• Chloroplasts:
  • Found in plant cells, site of photosynthesis.
  • Contains chlorophyll, which gives plants their green color.

Unique Structures in Certain Cells

• Cell Wall:
  • Found in plant cells, provides shape and protection.
  • Absent in animal cells.
• Cilia:
  • Hair-like projections in some cells, like those in the respiratory tract.
  • Help move particles and expel them when coughing.
• Flagella:
  • Tail-like structure for movement in some cells.
  • Present in some bacteria and human sperm cells.

Summary

• Eukaryotic vs Prokaryotic Cells:
  • Eukaryotes have a nucleus and organelles; prokaryotes do not.
• Common Features of All Cells: Cell membrane, cytoplasm, and genetic material.
• Energy Organelles: Chloroplasts in plant cells; mitochondria in both plant and animal cells.