HW 2

• Enzymes are biological catalysts & most enzymes are 


  proteins
• Enzymes bind their substrates (or reactants) in a specialized "pocket" called the


  active site
• Once the substrates bind the enzyme, what are some possible mechanisms for how the enzyme can help the substrates go through the reaction?

  Substrate orientation and inducing physical strain
• Regulating the activity of enzymes is rarely needed bc virtually al biological rxns must go forward at max speed all the time in order to maintain homeostasis

  false
• In competitive inhibition, the inhibitor binds

  in the active site. This binding is weak and temporary
• Phosphate groups are too small to serve as allosteric regulators


  false
• Allosteric inhibition is also called non-competitive inhibition


  true
• Allosteric regulation is a strategy that either inhibit or activate enzymes


  true
• herpes virus

  neither eukaryote nor prokaryote
• Paramecium (protist)


  eukaryote
• E. coli

  prokaryote
• Yersinia pestis (bacteria)

  prokaryote
• mosquito

  eukaryote
• yeast

  eukaryote
• rose bush

  eukaryote
• Structures unique to prokaryotic cells (NOT found in eukaryotic cells)

  nucleoid, peptidoglycan cell wall
• Lysosome


  contains digestive enzymes for breaking down macromolecules
• Chloroplast

  site of photosynthesis
• Nucleolus


  dense area inside the nucleus where ribosomes are assembled
• Rough endoplasmic reticulum


  membrane structure where ribosomes "dock" while making proteins
• Mitochondria


  powerhouse of the cell
• Central vacuole


  large storage compartment commonly found in plants and fungi
• Nucleus


  contains the genetic material (DNA) of the cell
• Golgi apparatus


  stack of flattened sacs which sort and package proteins
• Smooth endoplasmic reticulum


  tubular structure for modification of toxins and lipid synthesis
• microtubules


  have cilia & flagella, and chromosome positioning during cell division
• microfilaments


  are made of actin and are involved in cell "crawling" and contraction movements
• intermediate filaments


  have an "interwoven" structure and are NOT dynamic (can't be easily lengthened or shortened)
• cells are enmeshed in a protein fiber network which allows a lot of fluid flow between cells


  animal tissues
• cells are connected by plasmodesmata 


  plant tissues
• Phospholipid molecules commonly "flip" back and forth, an action to maintain membrane fluidity

  false
• What changes should the protist make to its membrane to maintain a proper level of fluidity?

  Replace short fatty acids with longer ones & remove unsaturated fatty acids and replace them with saturated ones
• What molecules can pass directly through the bilayer by simple diffusion?

  CO2, estrogen, and ethanol
• The defining difference between voltage-gated and ligand-gated ion channels is


  what causes the channel to open
• Exocytosis


  is used to expel unwanted material from the cell, or secrete substances made in the cell
• Phagocytosis


  is used for uptake of large food particles, debris, or foreign invaders
• Pinocytosis 


  is primarily used for the uptake or transport of fluid
• Receptor-mediated endocytosis


  allows the very SPECIFIC uptake of molecules or particles in the environment which may be rare
• Steps of Phagocytosis in chronological order:

  1. a particle is engulfed by in invagination of the cell membrane, forming a phagosome
  2. a primary lysosome fuses with the phagosome
  3. digestive enzymes break macromolecules in the particle down into monomers
  4. small nutrient molecules such as sugars and amino acids are transported into the cytoplasm by facilitated diffusion
  5. undigested remnants of the particle are expelled from the cell by exocytosis
• Ultimately, the point of cellular respiration is to extract energy from food and use it to form (or re-assemble)


  ATP