Chapter 3

• Plasma Membrane Structure


  Outer leaflet attached to system of glycoproteins, glycolipids, and polysaccharides that form glycocalyx surrounding membrane
• Plasma Membrane Functions

  Connect cytoskeleton and extracellular proteins, enzyme proteins that catalyze reactions, receptor proteins for extracellular regulators, antigen markers that identify cell to immune system
• Phagocytosis


  Cells that exhibit amoeboid motion to use pseudopods to surround and engulf particles of organic matter to protect body and remove debris
• Endocytosis


  Plasma membrane furrows inward
• Pinocytosis


  Form of endocytosis. Plasma membrane invaginates and furrow fuses to produce endosome that is pinched off and enters the cell, allowing it to engulf large molecules
• Receptor-Mediated Endocytosis


  Occurs only in response to specific molecules that must bind to specific receptor proteins in plasma membrane
• Exocytosis


  Cellular products secreted into extracellular environment, packaged in vesicles by Golgi complex
• Retrograde Transport

  Proteins within extracellular fluid are brought into cell and taken to Golgi complex and Endoplasmic Reticulum. Viruses and toxins rely on this to infect.
• Lysosomes


  Digestive enzymes isolated here.
• Primary Lysosome


  Digestive, acidic
• Secondary Lysosome


  Primary fused with food vacuole that contains engulfed extracellular material via autophagy
• Autophagosome


  Virus-containing fusion with lysosomal enzymes to degrade viruses for immunity
• Peroxisomes


  Membrane-bound organelles containing enzymes that promote oxidative reactions to remove hydrogen from organic molecules -> oxidases -> hydrogen peroxide
• Cristae


  Mitochondrial folds, shelf projections into matrix
• Ribosomes


  Protein factories, produced according to genetic information from mRNA
• Rough Endoplasmic Reticulum


  Ribosomes on surface, protein synthesis
• Smooth Endoplasmic Reticulum


  No ribosomes, site for enzymatic reactions in steroid hormone production, site for Ca+2 storage in striated muscle cells
• Golgi Complex


  Stack of flattened sacs with cavities called cisternae
• Nucleoli


  Not surrounded by membranes, contains genes that code for rRNA production
• Stages of Genetic Expression


  Transcription (RNA synthesis) and translation (protein synthesis)
• Genome


  All genes of particular individual or all genes of particular species
• Gene


  Regions of DNA that code through production of mRNA for polypeptide chains
• Proteome


  All different proteins produced by a genome
• Chromatin


  DNA within nucleus combined with protein, makes up chromosomes
• Histones


  Positively charged protein organized in spools about which negatively charged strands of DNA are wound
• Nucleosomes


  2 turns of DNA comprising 146 base pairs wound around a core of histones
• Euchromatin


  Extended form of chromatin active in transcription
• Heterochromatin


  Condensed inactive form of chromatin
• Types of RNA


  Precursor messenger, messenger, transfer, ribosomal
• Pre-mRNA


  Altered within nucleus to form mRNA
• mRNA


  Contains code for synthesis of specific proteins
• tRNA


  Decodes genetic message contained in mRNA
• rRNA


  Forms part of the structure of ribosomes
• RNAi


  Regulatory process performed by RNA molecules that don't code for proteins and prevent specific molecules from being translated
• siRNA


  Short interfering RNA. Formed from longer double-stranded RNA that leaves nucleus and are processed in cytoplasm by dicer enzyme into shorter double-stranded RNA.
• miRNA


  Micro RNA. Formed from longer RNA that fold into hairpin loops that leave nucleus and are processed in cytoplasm by dicer enzyme into 2 strands: 1 short, enters RISC
• RISC


  RNA-induced silencing complex
• Polyribosomes


  Result of attachment of mRNA to ribosomes in cytoplasm
• Golgi Complex Protein Functions


  Protein modification, separation, vesicle shipment
• Ubiquitin


  Short polypeptide tag for protein destruction via proteasome