Cell Structure and Functions Quiz

Cell Structure and Functions

• Cells are the basic units of life.
• Studying cells involves prokaryotes and eukaryotes, cell structures, and organelles.
• Transport across cell membranes is also a key aspect.

Prokaryotes (Prokaryotic Cells)

• Prokaryotes are single-celled organisms.
• They are the smallest and simplest cells, typically ranging from 1 to 10 µm in size.
• Examples include bacteria and archaebacteria.
• Their cytoplasm/protoplasm is enclosed by a plasma membrane.
• They lack a cytoskeleton.
• The cell wall is made of peptidoglycan, which maintains cell shape.
• Gram-negative bacteria have thinner cell walls and do not retain the Gram stain.
• Gram-positive bacteria retain the Gram stain (purple).
• Some prokaryotes have capsules to limit phagocytosis.
• They lack membrane-bound organelles.
• Mesosomes are infoldings of the plasma membrane, involved in cellular respiration.
• Prokaryotes contain ribosomes for protein synthesis.
• Some prokaryotes have flagella for movement and pili for attachment.
• Genetic material is "naked" circular DNA (nucleoid).
• Some have plasmids (small circular DNA) storing important genes, such as antibiotic resistance.
• Prokaryotes have a high metabolic and growth rate, and a short lifespan.
• Reproduction occurs through binary fission.

Eukaryotes (Eukaryotic Cells)

• Eukaryotic cells include animal and plant cells. They can be unicellular or multicellular.
• Eukaryotic cells are larger, ranging from 10 to 100 µm.
• They are bounded by plasma membranes.
• Eukaryotic cells contain a distinct nucleus enclosed by a nuclear envelope.
• They have membrane-bound organelles.
• They possess a cytoskeleton for structural support and intracellular movement.
• Flagella are more complex in eukaryotes.
• Eukaryotic cells reproduce through meiosis and mitosis.

The Cell and Organelles

• Exterior structure:
  • Cell wall (in plants and some bacteria)
  • Plasma membrane (encloses the cytoplasm, semi-permeable)
  • Cilia and flagella (projections for movement and other functions)
• Interior structure:
  • Cytoplasm (the jelly-like substance inside the cell)
  • Cytoskeleton (in eukaryotes)
  • Organelles (specialized structures within the cell - endomembrane system, mitochondria, chloroplasts, ribosomes, and the nucleus)

Cell Wall

• Found in plants and some bacteria and protists.
• Provides support and protection.
• Plants - made of cellulose.
• Bacteria - made of peptidoglycan.

Plasma Membrane

• Encloses the cytoplasm.
• A phospholipid bilayer with embedded proteins.
• Semi-permeable (selectively permeable).
• Functions include separating the cell's interior from the environment, shape maintenance, cell adhesion, ion channel activity, cell signaling, and cytoskeleton attachment points.

Cilia

• Projections from the cell surface.
• Motile (move) or non-motile (primary).
• Primary cilia are present on nearly every cell in the human body.
• Function in movement and sensory reception.
• Microtubules (hollow cylinders formed from protein) are the structural components of cilia. The arrangement and positioning of microtubules determine cilia function. Primary cilia (9+0) are typically non-motile, whereas motile cilia (9+2) facilitate rhythmic beating.

Flagella

• Projections from the cell.
• Usually longer than cilia.
• Made of microtubules covered by a plasma membrane (9+2 arrangement).
• Involved in cell movement.

Differences between prokaryotic and eukaryotic cells

• Prokaryotic cells are smaller and simpler with no nucleus or membrane-bound organelles.
• Eukaryotic cells are larger and more complex, have a nucleus and membrane-bound organelles, and are more diverse.

Test your knowledge on the basic units of life, including prokaryotic and eukaryotic cells. This quiz covers cell structures, organelles, and the differences between Gram-positive and Gram-negative bacteria. Challenge yourself to understand the intricate details of cellular biology.