Cell Biology Final Review

• Cell membrane


  Consists of a lipid bilayer that is semipermeable separating interior of the cell from the outside environment
• Cytosol


  The aqueous component of the cytoplasm of a cell, within which various organelles and particles are suspended
• Cytoplasm


  All material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus
• Nucleus


  This organelle contains our DNA with all our genetic information
• Nuclear membrane


  A double membrane with pores, governs import with Ran-GTP cycle and contains a intermediate filament inner cortex

  
• Mitochondria


  These have a double membrane that folds in on itself forming little finger-like projections called cristae. They break down sugars to make ATP, which is used by the cell as energy
• Ribosomes


  Contains a large and small submit involved in protein translation
• Endoplasmic reticulum (ER)


  Series of connected flattened sacs plays a central role in the synthesis of proteins and lipids
• Golgi apparatus


  These are made up of flat vesicles that package things to be transported around or leave the cell
• Lysosomes


  These are vesicles with digestive enzymes inside that break down things the cell doesn't need
• Vacuoles


  Membranous sacs, generally small and help sequester waste products
• Peroxisomes


  Hydrogen peroxide chemistry for breakdown & synthesis of molecules
• Endosomes


  Sort components brought into cells via endocytosis
• Protein domain


  A discrete structural and functional unit within a protein

  
• Amino acids are the building blocks for proteins

  
• Amino acid side chain classifications

  • Nonpolar (hydrophobic)
  • Polar uncharged
  • Positively charged (basic)
  • Negatively charged (acidic)

  
• Primary structure = amino acid sequence in a polypeptide chain

  
• Secondary structure = coils and folds due to interactions between atoms of the backbone and side chains
• Tertiary structure = interactions among various side chains (R groups)
• Quaternary structure = assembly of multiple polypeptide chains
• Protein domain

  A part of a protein that folds independently into a stable structure

  
• Many proteins are composed of separate functional domains
• Protein phosphorylation


  Protein kinases catalyze protein phosphorylation, and protein phosphatases remove the modification

  
• Phosphorylation of enzymes will not always activate them
• Regulation by phosphorylation can be rapidly reversible
• Protein phosphorylation adds a negatively charged group to a protein frequently causing a conformational change
• Feedback inhibition


  The end product of a metabolic pathway shuts down the pathway
• Phosphorylation can control protein activity by causing a conformational change

  
• Protein kinases phosphorylate proteins

  
• Protein phosphatases dephosphorylate proteins

  
• Phosphorylation can affect the location and interaction of proteins

  
• GTP-binding proteins


  Function as molecular switches, the dissociation of GDP and its replacement by GTP turns the switch on

  
• Activated GTP-binding proteins will bind to other proteins to control their activity, transmitting the signal

  
• Allosteric enzymes


  Typically have two or more binding sites that influence one another, binding of a ligand to one of the sites causes conformational changes
• Heterochromatin


  Most condensed = Gene poor regions (includes centromeres and telomeres), genes are not expressed, induced by tail modifications, including methylation of Lys 9 on the histone H3 tail

  
• Euchromatin


  Less condensed = Gene rich region

  
• Nucleosomes are the basic units of chromatin packing, consisting of 4 pairs of histones (octamer) and a 147 bp piece of DNA

  
• RNA is single-stranded but can contain conventional and "unconventional" base-pair interactions (e.g., A-G), RNA molecules can fold up into specific 3D shapes, DNA's function is purely storage of information whereas RNAs can have structural, regulatory and catalytic roles

  
• RNA polymerases are responsible for transcription of DNA into RNA, they move stepwise along DNA, unwinding the DNA helix just ahead to expose the template strand, the RNA chain is extended by one nucleotide at a time from its 5' → 3'

  
• TFs position the RNA polymerase and pull apart the DNA double helix to expose the template strand, TATA-binding protein (TBP) subunit of TFIID bends the DNA double helix