Cell Biology Quiz: Prokaryotes vs Eukaryotes

The Cell (I)

• All living things are made of one or more cells.
• Cells are the smallest units of living things.
• The human body contains many different types of cells.
• All cells share basic characteristics, such as being enclosed by a cell membrane, capable of respiration, reproduction, and growth.
• Cells vary in function, shape, and size.
• Examples of cell shape variation include: rounded, oval, flat, cubical, columnar, spindle or fusiform.
• Examples of cell size variation: lymphocyte (6µm) and fat/ova cells (160µm).

Cell Types

• Cells are categorized into prokaryotic and eukaryotic cells.
• Prokaryotic cells lack a nuclear membrane or other membrane-bound organelles within their cytoplasm, and are surrounded by a cell wall .
• Examples include bacteria and blue-green algae.
• Eukaryotic cells possess a nuclear membrane and membrane-bound organelles in their cytoplasm.
• They are surrounded by a cell membrane (plasma membrane).
• Examples include plant and animal cells.

Eukaryotic Cell Possessions

• Cell (plasma) membrane: A thin membrane (7.5-10 nanometers thick) separating the intracellular and extracellular environments.
• Protoplasm: A fluid-like material encompassing the cell's contents; including:
  • Cytoplasm (cytosol): The protoplasm surrounding the cell nucleus.
  • Nucleoplasm: The protoplasm within the nucleus.
• Organelles: Living structures crucial for cellular functions.
• Inclusions: Non-living accumulations of metabolites or cell products.
• Other substances: Water (75%), proteins, carbohydrates, lipids, nucleic acids, and minerals.
• Nucleus: A prominent organelle containing genetic material.

Cell Structure

• Protoplasm: Includes the entire contents of the cell—the nucleus and the cytoplasm (cytosol).
• Cell membrane: Surrounds the entire protoplasm.
• Cytoplasm (cytosol): The fluid portion of the cell, outside of the nucleus.
• Nucleus: Contains the nucleoplasm, where the cell's genetic information resides.
• Organelles: Small structures within the cytoplasm performing specific functions.

Cell Membrane (Plasma Membrane)

• A very thin membrane (7.5-10 nm thick)
• Separates the intracellular from the extra cellular environments.
• Not visible with a light microscope, but visible with an electron microscope.
• Composed of:
  • A bilayer of phospholipids.
  • Proteins.
  • Cholesterol.
  • Short chains of sugars (glycoproteins and glycolipids).
• The membrane is flexible due to the lateral movement of phospholipids and proteins.

Molecular Structure of the Cell Membrane

• Phospholipid bilayer: Two layers of phospholipids.
• Polar heads face outward, interacting with water.
• Nonpolar tails face inward, avoiding water.
• Cholesterol embedded within the bilayer regulates membrane fluidity.
• Peripheral proteins: On the surface of the membrane.
• Integral proteins: Span the membrane, possibly acting as channels or carriers.

Cell Membrane Lipids

• Phospholipids: Have a polar (hydrophilic) head and nonpolar (hydrophobic) tails.
• The hydrophilic heads face outward and the hydrophobic tails face inward.
• Cholesterol: Embedded in the phospholipid bilayer.
• Regulates membrane fluidity.

The Proteins of Cell Membrane

• Globular proteins embedded in the phospholipid bilayer.
• Integral proteins: Span the membrane;
  • Transmembrane proteins: Span the entire membrane (e.g., ion channels)
  • Monotopic proteins: Embedded into one side of the membrane (e.g., enzymes).
• Peripheral proteins: Loosely attached to the membrane surface.

Functions of Proteins of the Cell Membrane

• Structure support.
• Transport of molecules (channels or carriers).
• Cell-cell recognition.
• Receptors for hormones and antigens.
• Enzymatic control of chemical reactions.

The Carbohydrates of Cell Membrane

• Attached to membrane proteins (glycoproteins) and lipids (glycolipids).
• Form the glycocalyx (cell coat).
• Functions:
  • Cell adhesion (binding cells to each other).
  • Cell-cell recognition (e.g., distinguishing self from non-self cells).

Transport Across Cell Membrane

• Movement can be passive or active.
• Passive Transport:
  • Simple diffusion: Movement of small molecules (e.g., O2, CO2) from high concentration to low concentration across a semi-permeable membrane.
  • Osmosis: Movement of water from high concentration to low concentration across a selectively permeable membrane.
  • Facilitated diffusion: Large or charged molecules (e.g., ions, glucose, amino acids) move through membrane proteins.
• Active Transport: Uses energy (ATP) to transport molecules against their concentration gradient.

Bulk Transport

• Endocytosis: Active transport of large particles into the cell.
  • Phagocytosis: Cell eating (taking in solid particles).
  • Pinocytosis: Cell drinking (taking in liquid particles).
  • Receptor-mediated endocytosis: Specific molecules bind to receptors on the membrane.
• Exocytosis: Active transport of molecules out of the cell.

Solutions and Osmosis

• Isotonic solution: Concentration of solutes same inside and outside the cell.
• Hypertonic solution: Higher concentration of solutes than inside the cell.
• Hypotonic solution: Lower concentration of solutes than inside the cell

Test your knowledge on cell biology with this quiz focused on prokaryotic and eukaryotic cells. Explore concepts such as cell structures, functions, and transport mechanisms. Challenge yourself with questions that highlight the differences and similarities between these two types of cells.