Cell Theory and History Quiz

Cell History Timeline

• Robert Hooke (1665): First to observe cells
• Anton van Leeuwenhoek (1674): Observed microorganisms
• Matthias Schleiden (1838): All plants are made of cells
• Theodor Schwann (1839): All animals are made of cells
• Rudolf Virchow (1855): All cells come from pre-existing cells
• Janet Plowe (1931): Further cell research

Cell Theory

• All living things are made up of cells
• Cells are the basic unit of structure and function in an organism
• New cells are produced from existing cells

Cellular Organization

• Early studies described cells as protoplasm (primary substance) containing a nucleus surrounded by a membrane.
• The protoplasm surrounding the nucleus is called cytoplasm, while the protoplasm within the nucleus is called nucleoplasm.
• Electron microscopy (EM) revealed two basic cell types: prokaryotes and eukaryotes.
• Prokaryotes are simpler, without a nuclear envelope or compartments.
• Eukaryotes are more complex and contain a nuclear envelope and compartments called organelles.

Prokaryotic vs. Eukaryotic Cells

Cell Structure Details

• Size: Prokaryotic cells are typically 0.2-2.0 μm in diameter; eukaryotic cells are typically 10-100 μm in diameter.
• Nucleus: Prokaryotes lack a nucleus; eukaryotes have a true nucleus with a membrane and nucleolus.
• Membrane-enclosed organelles: Prokaryotes lack them; eukaryotes have various membrane-bound organelles (e.g., mitochondria, Golgi apparatus, endoplasmic reticulum).
• Flagella/Cilia: Can be present in both prokaryotes and eukaryotes; structures for movement.
• Glycocalyx: Present in some prokaryotes as a capsule or slime layer; in some eukaryotes.
• Cell Wall: Usually present in prokaryotes (typically peptidoglycan); can be present in eukaryotes (e.g., plants, fungi; composed of cellulose or chitin).
• Plasma membrane: Both types of cells have this structure; surrounds the cytoplasm.
• Cytoplasm: The contents of a cell between the nucleus and the plasma membrane.
• Cytoskeleton: More complex in eukaryotes; involved in cell structure and shape.
• Ribosomes: Found in both types of cells but different in size (70S vs 80S)
• Chromosome: Usually single circular in prokaryotes; multiple linear in eukaryotes
• Cell Division: Binary fission (prokaryotes); mitosis (eukaryotes)
• Sexual Recombination: Absent/only transfer of DNA (prokaryotes); Present (eukaryotes)

Cell Theory Processes

• Manufacturing: Involves the nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus. This includes synthesis of proteins, like enzymes.
• Breakdown: Includes lysosomes, vacuoles, and peroxisomes; responsible for digesting food, bacteria, and cellular waste.
• Energy-processing: Involves mitochondria (in animal cells), which generate energy to power cellular function in the form of ATP.
• Structural support, movement, and communication: Cytoskeleton and plasma membrane involved in cell structure, movement, and communication with other cells

Plasma Membrane Structure

• Composition: Made of a mix of proteins and lipids.
• Proteins:
  • Transmembrane proteins: Span the bilayer
  • Peripheral proteins: Located on the surfaces of the bilayer
• Carbohydrates:
  • Attached to protein (glycoproteins) or lipids (glycolipids); involved in cell recognition.
• Phospholipid bilayer: Main component; composed of two layers (bilayer) of phospholipid molecules. Phospholipids composed of fatty acid chains and a phosphate head group.

Transport Across the Membrane

• Passive transport: Movement of molecules from high concentration areas to low, without energy input - Diffusion: Movement of small molecules down the concentration gradient. Example: CO2 and H2O - Facilitated diffusion: Need protein carriers to move large molecules down the concentration gradient.
• Active transport: Movement of molecules from low concentrations to high, requiring energy input; utilizes protein carriers.
• Bulk transport: Movement of large molecules; requires cellular energy
  • Exocytosis: Transport out of the cell
  • Endocytosis: Transport into the cell; sub categories:
    • Pinocytosis: Transport of fluids
    • Phagocytosis: Transport of solids, including bacteria.

Test your knowledge on the history and theory of cells with this quiz. Explore the contributions of key scientists and understand the fundamental concepts of cellular organization. Perfect for students studying biology and life sciences.