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5 Written Questions

5 Matching Questions

  1. Cadherin
  2. Transaminase
  3. Uncoupler
  4. 3 useful functions of TCA cycle
  5. Feedback inhibition of regulatory enzymes
  1. a
    This is the mechanism by which the activity of an enzyme is allosterically effected by the later products in the catalytic pathway, thus preventing over production of the product. So the penultimate product of the enzyme also acts as the effector molecule at the enzyme allosteric site.
  2. b 1. Uses glucose atoms to form reduced coenzymes. In the last stage of glucose oxidation (the electron transport chain) these H atoms finally make energy available as ATP, through the process of oxidative phosphorylation.
    2. It produces a molecule of ATP by substrate level phosphorylation (reaction T5). Since the cycle turns twice for every glucose oxidised , the yield is 2 ATP's per glucose molecule.
    3. It produces carbon intermediates for biosynthesis. This is particularly relevant in plants, where biosynthesis rather than energy production is the main role of the TCA cycle.
  3. c
    A specific enzyme which catalyses the transfer of NH₂ from amino acids to α-Ketoglutarate of the TCA cycle (forming glutamate which can also be used for protein synthesis) during the break down of amino acids derived from proteins, in carnivorous animals or in other animals at times of low availability of glucose or TAGs for energy production. Their are specific versions of this enzyme for each of the two acidic amino acids.
  4. d
    Cadherins (named for "calcium-dependent adhesion") are a class of type-1 transmembrane proteins. They play important roles in cell adhesion, ensuring that cells within tissues are bound together. They are dependent on calcium (Ca2+) ions to function, hence their name. The extra cellular domains on cadherins interact with their counterparts in other cell membranes and their intracellular domains interact intracellular proteins. The intracellular proteins are then bound to cytoskeleton intermediate filaments known as keratin.
  5. e Any compound that increases the proton permiability of the inner mitochondrial membrane and hence severes the link between electron transport and ATP synthesis. Two example are thyroxine and brown adipose tissue.

5 Multiple Choice Questions


  1. A small regulatory protein that has been found in almost all tissues (ubiquitously) of eukaryotic organisms. Among other functions, it directs protein recycling.It can be attached to proteins and label them for destruction. This protein tag directs proteins to the proteasome, which is a large protein complex in the cell that degrades and recycles unneeded proteins. This discovery won the Nobel Prize for chemistry in 2004.
    The tags can also direct proteins to other locations in the cell, where they control other protein and cell mechanisms.

  2. Five key characteristics (of this enzyme)
    1.Larger, multi-subunit proteins consisting generally of two different subunits eg. catalytic and regulatory.
    2. Substrates bind cooperatively to active sites on catalytic subunits.
    3. A plot of v against s produces an S shaped sigmoid curve.
    4. Effectors for these enzymes can be inhibiting or activating and their binding can also produce sigmoid curves.
    5. Feedback inhibition can occur- the end product of the enzymes pathway can inhibit enzyme activity.

  3. In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate(s). In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or more products, which are then released from the active site. The active site is now free to accept another substrate molecule. In the case of more than one substrate, these may bind in a particular order to the active site, before reacting together to produce products.
  4. Pertaining to a compound exhibiting polarity or dipole moment, that is a compound bearing a partial positive charge on one side and a partial negative charge on the other.

  5. Hollow tubes composed of thirteen parallel filaments of polymerized tubulin, measuring about 25 nm in external diameter. Part of the cytoskeleton of ALL eukaryote cells radiating from the centrosome in the nucleas towards the edges of the cell. They are very unstable and are constantly disassembling and reassembling so most do not reach the cell cortex. These tubules play a crucial role in cell organisation, movement of organelles and the reorganization of chormosomes in to daughter cells during mitosis.

5 True/False Questions

  1. LDH reaction
    A specialised type of cell junction, an example of which is the smooth muscle of the intestine. The gap's allow for effective transmission of molecules and electrical activity between the cells.

          

  2. Km
    The point on a rectangular hyperbola which is half the value of the Vmax. It indicates the affinity of an enzyme and substrate a high value means low affinity and a low value means high affinity (the enzyme substrate locks more securely and takes longer to seperate and release products).

          

  3. Substrate specificityA characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. An ezyme can only react upon the substrate with which it locks.

          

  4. Ficks Law
    The structure formed by two tailed lipids when mixed with water, it consists of a spherical bilayer withthe hydrophobic tails pointing inwards and the hydrophillic heads pointing outwards in close contact with each other and the water.

          

  5. Peroxisomes
    Special proteins around which DNA is wrapped.

          

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