Animal Cell

• Cell Functions:

  • Metabolize and release energy through chemical reactions within cells
  • Release of energy in the form of heat helps maintain body temperature
  • Synthesize molecules, leading to cells differing from each other
  • Provide a means of communication through chemical and electrical signaling
  • Reproduction and Inheritance through mitosis and meiosis
• Cell Organization:

  • The cell is the basic structural and functional unit of life
  • Each cell is a highly organized unit with:
  • Plasma membrane: forms the outer boundary of the cell
  • Cellular organelles: each performs specific functions
  • Nucleus: contains the cell's genetic material and directs cell activities
  • Cytoplasm: the material between the plasma membrane and nucleus
• Plasma Membrane:

  • Plays a dynamic role in cellular activity
  • Encloses the cell and supports its contents
  • Acts as a selective barrier regulating what goes in and out of the cell
  • Separates intracellular substances from extracellular substances
• Fluid Mosaic Model:

  • Lipid bilayer with dispersed proteins
  • Bilayer consists mainly of phospholipids and cholesterol
  • Phospholipids have hydrophobic (nonpolar tails) and hydrophilic (polar heads) bipoles
  • Cholesterol gives the membrane added strength and flexibility
• Functions of Membrane Proteins:

  • Protein molecules "float" among the phospholipid molecules
  • Functions include:
  • Marker molecules
  • Attachment proteins (cadherins and integrins)
  • Transport proteins
  • Receptor proteins
  • Enzymes
• Vesicular Transport:

  • Transport of large particles and macromolecules across plasma membranes
  • Endocytosis: movement of materials into cells by vesicle formation
  • Phagocytosis: movement of solid material into cells
  • Pinocytosis: uptake of small droplets of liquids and materials
  • Receptor-mediated endocytosis: plasma membrane receptors attaching to molecules taken into the cell
  • Exocytosis: secretion of materials from cells by vesicle formation
• Cytoplasm:

  • Material between the plasma membrane and nucleus
  • Consists of cytosol, cytoskeleton, and cytoplasmic inclusions
  • Cytoskeleton supports the cell and enables cell movements
  • Cytoplasmic inclusions are aggregates of chemicals produced or taken in by the cell
• Cytoplasmic Organelles:

  • Specialized subcellular structures with specific functions
  • Membranous organelles include mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, and Golgi apparatus
  • Nonmembranous organelles include centrioles and ribosomes
• Nucleus:

  • Nuclear envelope consists of two separate membranes with nuclear pores
  • Contains DNA and associated proteins
  • DNA is the hereditary material of the cell and controls cell activities
  • Chromatin organizes DNA between cell divisions, condensing into chromosomes during cell division
• Nucleoli and Ribosomes:

  • Nucleoli produce ribosomal ribonucleic acid (rRNA) and assemble ribosomal subunits
  • Ribosomes are sites of protein synthesis, with free ribosomes synthesizing proteins inside the cell and attached ribosomes part of the rough endoplasmic reticulum
• Endoplasmic Reticulum (ER):

  • Rough ER is studded with ribosomes and a major site of protein synthesis
  • Smooth ER lacks ribosomes and is a major site of lipid and carbohydrate synthesis
• Golgi Apparatus:

  • Series of closely packed membranous sacs that collect, package, and distribute proteins and lipids produced by the ER
• Lysosomes:

  • Spherical membranous bags containing digestive enzymes
  • Functions include digesting bacteria, viruses, toxins, nonfunctional organelles, and breaking down various substances
• Peroxisomes:

  • Membranous sacs containing oxidases and catalases
  • Breakdown fatty acids, amino acids, hydrogen peroxide, detoxify harmful substances, and neutralize free radicals
• Mitochondria:

  • Major sites of ATP production via aerobic cellular respiration
  • Have a smooth outer membrane and inner membrane with infoldings called cristae
  • Contain their own DNA, produce some proteins, and can replicate independently
• Centrioles and Spindle Fibers:

  • Centrioles are cylindrical organelles in the centrosome, involved in microtubule formation and separation of chromosomes during cell division
  • Spindle fibers extend from the centrosome and form the bases of cilia and flagella
• Cilia, Flagella, and Microvilli:

  • Cilia move substances over cell surfaces
  • Flagella propel sperm cells
  • Microvilli increase cell surface area aiding in absorption and secretion