Cell

• Cell


  Basic unit of structure and function of all living organisms
• Cell components


  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Cell organelles
• Cell membrane


  • Thin covering of a double layer of phospholipids and associated proteins
  • Phospholipids have polar (hydrophilic) heads and non-polar (hydrophobic) tails
  • Hydrophobic barrier keeps water-dissolved contents inside
• Proteins in cell membrane


  • Intrinsic - embedded in lipid double layer
  • Extrinsic - associated outside lipid double layer
• Cytoplasm


  Living fluid part between cell membrane and nucleus, containing cell organelles
• Cytosol


  Liquid part of cytoplasm formed of water having dissolved or suspended substances
• Cell organelles


  • Double membrane bound: Mitochondria, Chloroplasts, Endoplasmic Reticulum, Golgi Body, Nucleus
  • Single membrane bound: Lysosomes, Peroxisomes, Vacuoles
  • Lacking membrane: Ribosomes, Centrioles, Nucleolus
• Nucleus


  Most distinct structure inside cell, contains DNA with information to form and run the cell
• Nuclear envelope


  • Formed of 2 membranes with a gap, has nuclear pores to allow RNA and proteins to pass through
• Nucleoplasm


  Liquid part of nucleus, different composition than cytosol
• Chromatin fibers


  Long molecules of DNA associated with proteins (histones and other nuclear proteins), organize into chromosomes during cell division
• Nucleolus


  Assembles both units of ribosomes, present in nucleus when cell is not dividing
• Endomembrane system components


  • Endoplasmic Reticulum
  • Golgi Apparatus
  • Lysosomes
  • Vacuoles
• Endoplasmic Reticulum (ER)


  • System of double membranes in form of tubes and sacs, main manufacturing facility for proteins and lipids, transports materials inside cell
• Golgi Apparatus


  • Stacks of flattened sacs called cisternae, receives transport vesicles from ER, modifies and packs chemicals into secretory vesicles
• Lysosomes


  • Single membrane bound organelles rich in digestive enzymes, help break down large molecules, provide safe place for digestion
• Vacuoles


  • Membrane bound sacs, functions include endocytosis, exocytosis, maintaining turgor pressure in plant cells, transportation
• Mitochondria


  • Powerhouses of cells, site of cellular respiration, have enzymes for breakdown of glucose, fatty acids and amino acids, generate ATP
• Cytoskeleton


  • Maintains cell shape and organizes cell contents, includes intermediate filaments, microtubules, and microfilaments
• Genes


  Segments of DNA found in chromosomes, contain information to form and run the cell
• Chromatin fiber


  Formed of DNA and histone proteins, organizes into compact chromosomes during cell division
• Chromosome


  Compact thread containing DNA and associated proteins, each species has a fixed number
• Cell cycle


  1. Interphase - cell grows and DNA replicates

  2. Mitosis - division of nucleus

  3. Cytokinesis - division of cytoplasm
• Mitosis

  1. Prophase - chromosomes condense, spindle formation starts

  2. Metaphase - chromosomes align at equatorial plate

  3. Anaphase - chromosomes move to poles

  4. Telophase - chromosomes unpack, nuclear envelope reforms
• Cytokinesis


  1. In animal cells - cleavage furrow appears at middle

  2. In plant cells - cell plate forms at middle
• Most plant cells lack centrioles, so centrosomes organize spindle formation