Chapter 1 pt 2

Biochemistry and the Unity of Life

• Cells are the basic unit of life
• Organisms can be single-celled or multicellular
• Cells grow, replicate, and interact with each other

Learning Objectives

• Differentiate between prokaryotic and eukaryotic cells
• Describe the structure and function of the two main parts of a cell: the cell membrane and cytoplasm
• Describe the structure and function of organelles including the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus

1.4 Membranes Define the Cell and Carry Out Cellular Functions

• Basic unit of life is the cell
• Cells grow, replicate, and interact
• Two types of cells
  • Prokaryotic - lack a nucleus and membrane-bound organelles
  • Eukaryotic - have a nucleus and membrane-bound organelles
• Two parts of a cell (regardless of type)
  • Cell membrane - outer boundary of the cell
    • Phospholipid bilayer
      • Phosphate heads are hydrophilic (water-loving), facing outward
      • Fatty acid tails are hydrophobic (water-fearing), facing inward
    • Cytoplasm - intracellular material within the membrane, chemically different from the external environment.
• Semipermeable membrane – allows some things to cross, but not others
• Phospholipids primarily allow very small and hydrophobic substances to cross the membrane, while proteins facilitate the transport of larger, hydrophilic substances.
• Cytoplasm is the fluid inside the cell, where many biochemical processes occur including glucose metabolism, fatty acid synthesis, and protein synthesis
• Cytoplasm is organized by the cytoskeleton consisting of
  • Actin filaments
  • Intermediate filaments
  • Microtubules

Organelles Important in Biochemistry

• Nucleus - double-membraned organelle with nuclear pores, houses DNA and is the information center of the cell
• Mitochondria - double-membraned, inner membrane highly folded (cristae) - Intermembrane space between the membranes - Mitochondrial matrix inside the inner membrane - Produces most energy used by the cell
• Endoplasmic Reticulum (ER)
  • Network of membranous sacs
  • Two types
    • Rough ER - studded with ribosomes; synthesizes proteins that will be inserted into or secreted from the cell, and modifies/folds these proteins
    • Smooth ER - processes exogenous chemicals; synthesizes lipids
• Golgi complex - receives vesicles containing proteins from the rough ER, further processes proteins, adds carbohydrates, packages proteins in vesicles, and sends them to their target locations .