Chapter 8:

  • Define exergonic and endergonic
  • Exergonic reactions give off energy that could be trapped to do work (i.e. run other reactions, build molecules, move things).
  • Endergonic reactions require an input of energy – often they are coupled to an exergonic reaction.
  • How do the structures of ATP and, conversely, ADP, allow them to store and release energy?
  • ATP is an adenosine molecule that has 3 phosphate groups attached to it
  • The breaking of one Pi off ATP releases some energy (exergonic) and leaves products of ADP and Pi.
  • ADP has two phosphates –
  • The restoration of ATP from ADP and Pi is endergonic and requires input of energy. The breakdown of organic molecules like sugar releases energy that is used to make ATP.
  • Describe how ATP can be "coupled" to a reaction to help drive it?
  • For example, glucose is broken down with oxygen to finally be released as carbon dioxide and water. It gives off energy that is used to “make” ATP.
  • ATP can then be broken down to ADP and Pi and release the energy to drive some other process in the cell.
  • How is ATP regenerated
  • ATP is regenerated when energy is added to the reaction of ADP and Pi.
  • How do enzymes work based on a specfic shape?
  • Enzymes are proteins with a very specific 3-D shape
  • Enzymes have a specific active site that will only fit the target “substrate” unless an inhibitor.
  • Define substrate, active site
  • Substrate is the specific reactant(s) that an enzyme matches.
  • Active site matches the shape of the substrate (or is lined with complementary charges on amino acids)
  • Briefly describe the concept of activation barrier and how an enzyme works on it.
  • Even spontaneous reactions need to breach an energy of activation -
  • Enzymes lower the activation barrier and make it easier for the reaction to start.
  • What factors affect enzyme activity?
  • Enzymes are proteins and have a specific shape – anything that alters the shape will affect it –
  • Temperature - denature
  • pH
  • Presence of an inhibitor that might block the active site.
  • Enzymes also operate under roles of physics which means that force of collision will affect rate
  • Temperature can speed up movement or slow it down (warm and cold)
  • Concentration of substrate
  • Concentration of enzyme
  • Give a brief summary of redox reactions (oxidation and reduction).
  • The transfer of electrons from one element to another
  • Oxidation occurs to the element that loses an electron
  • Reduction occurs to the element that gains an electron
  • One cannot occur without the other.
  • Electrons are a high energy particle and can be used to transfer energy.
  • How is energy harvested when electrons are trapped by NAD+ and then put through the electron transport chain?
  • Electrons are released along with hydrogen atoms as organic molecules (like glucose) are broken down
  • These electrons can be “fed” into an electron transport chain (a series of molecules that are alternately reduced and oxidized as they pass electrons).
  • Like electricity, the movement of electrons is transferring energy and that energy is used to attach P to ADP making ATP.
  • Describe the stages of cellular respiration and account for the number of ATP generated at each stage.
  • Glycolysis occurs in the cytoplasm
  • Glucose (6 –C) is broken into two 3-C molecules
  • It takes a little energy to get started but it produces a net of 2 ATP
  • The products of glycolysis in the presence of O2 can be further broken down in the mitochondria.
  • Citric Acid cycle – in mitochondria – BLACK BOX version – the 2 3-C molecules are broken down fully to release 6 CO2 and the H that is released is picked up by a carrier called NAD+ NADH. You get 2 ATP.
  • Oxidative phosphorylation is where the NADH drops off both its electrons and the H+. The electrons go through an ETC (electron transport chain) – the energy generated is used to make a “charged” battery with a concentration of H+ on one side of the membrane. Basically the PE of the electrons goes to build PE of a H+ gradient. When the gradient is released, the energy is used to build ATP. The final step is that O2 must be present to take the H+ at the end. This process can generate up to 34 ATP.
  • Explain how fermentation occurs in the absence of oxygen
  • In the absence of oxygen the processes in the mitochondria cannot occur –
  • Fermentation is basically glycolysis followed by alcohol or lactic acid production.
  • Distinguish between alcohol and lactic acid fermentation
  • The product differs –
  • Yeast are an example that have alcohol fermentation and produce ethanol.
  • Humans and other mammals use lactic acid fermentation – in our muscles during heavy use we run short of O2 so we have some fermentation which produces lactic acid. Lactic acid must be reconverted to glycogen in the liver.
  • Compare fermentation to aerobic respiration
  • Fermentation only yields 2ATP/glucose.
  • Aerobic respiration can produce 38 ATP/glucose
  • What is significant about glycolysis?
  • It is an ancient system that nearly all organisms perform to get ATP.
  • How do organic molecules other than sugar feed into the metabolic pathways?

  • Compare/contrast anabolism to catabolism
  • Anabolism is building molecules
  • Catabolism is breaking them down
  • How are stages of cellular metabolism regulated?
  • Enzymes!
  • Feedback from different steps can slow or stop previous reactions by working on the enzymes -