Biology Module 6 & 7: Cell Functions

Module 6: Cell Functions and Prokaryotic vs. Eukaryotic Cells

• All cells share three core functions:

  • Metabolism
  • Reproduction
  • Maintain homeostasis

• Prokaryotic cells lack membrane-bound organelles, while eukaryotic cells possess them.

Module 7: Eukaryotic Cell Structures and Functions

• Compartmentalization increases eukaryotic cell efficiency by separating cellular processes.

• Endomembrane system components:

  • Endoplasmic Reticulum (ER): Rough ER (protein synthesis) and Smooth ER (lipid synthesis, detoxification).
  • Golgi apparatus: Modifies, sorts, and packages proteins and lipids.
  • Vesicles: Transport materials between organelles.
  • Lysosomes: Contain digestive enzymes that break down cellular waste.

• Mitochondria carry out cellular respiration (ATP production).

• Chloroplasts carry out photosynthesis (energy conversion).

• Plant cell walls provide support and structure, primarily composed of cellulose.

Module 8: Cell Size and Surface Area-to-Volume Ratio

• Cell size is limited by the ratio of surface area to volume (SA:V).
• A smaller surface area-to-volume ratio is associated with larger cells.
• Larger SA:V favors exchange of materials with the environment.

Module 9: Cell Membranes

• Phospholipids are amphipathic molecules (both hydrophobic and hydrophilic).
• Membrane fluidity is affected by temperature and cholesterol content.
• Integral proteins span the membrane; peripheral proteins are bound to a surface.
• Membrane proteins can perform transport, signal reception, or enzymatic activities.

Module 10: Membrane Transport

• Hydrophobic molecules readily cross cell membranes via passive diffusion.
• Diffusion is the movement of a substance down a concentration gradient, a spontaneous process.
• Potential energy is created by a concentration gradient.
• Osmosis, facilitated diffusion, and active transport are different types of membrane transport.

Module 11: Osmosis and Water Potential

• Hypertonic solutions have a higher solute concentration than the cell; hypotonic solutions have lower solute concentration; isotonic solutions have equal solute concentration.
• Osmosis is the diffusion of water across a semipermeable membrane.
• Water moves toward the region of higher solute concentration to maintain equilibrium.
• Water potential (Ψ) is used to predict water movement. Water will move from high Ψ to low Ψ.
• Living cells regulate water balance differently based on the presence of a cell wall.

Module 12: Endosymbiotic Theory

• Endosymbiotic theory proposes that mitochondria and chloroplasts evolved from prokaryotic cells engulfed by larger cells.
• Evidence for the theory includes the double membrane of these organelles and their similar size and DNA replication process to prokaryotes.