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5 Written questions

5 Matching questions

  1. Nuclear localization signal
  2. Glycophorin
  3. Stroma
  4. N-CAMS/Neural Cell Adehesion Molecules
  5. cis-unsaturated fatty acid
  1. a
    A cis configuration means that adjacent hydrogen atoms are on the same side of the double bond. The rigidity of the double bond freezes its conformation and, in the case of the cis isomer, causes the chain to bend and restricts the conformational freedom of the fatty acid. The more double bonds the chain has in the cis configuration, the less flexibility it has. When a chain has many cis bonds, it becomes quite curved in its most accessible conformations. For example, oleic acid, with one double bond, has a "kink" in it, whereas linoleic acid, with two double bonds, has a more pronounced bend. Alpha-linolenic acid, with three double bonds, favors a hooked shape. The effect of this is that, in restricted environments, such as when fatty acids are part of a phospholipid in a lipid bilayer, or triglycerides in lipid droplets, cis bonds limit the ability of fatty acids to be closely packed, and therefore could affect the melting temperature of the membrane or of the fat.
  2. b
    Negatively charged membrane glycoprotein which help to prevent red blood cells from sticking together through the actions of sialic acid sugar which is attached to it's extracellular domain .
  3. c Membrane glycoproteins with an extracellular region made up of several domains. They are involved in the formation of intercellular junctions in neural tissue and unlike cadherins are not calcium dependant. As with cadherins they have sialic acid sugar components giving the cell membrane a negative charge discouragin inter cell adhesion.
  4. d
    Also known as a nuclear localisation sequence (NLS) this is an amino acid sequence which 'tags' a protein for import into the cell nucleus by nuclear transport. Typically, this signal consists of one or more short sequences of positively charged lysines or arginines exposed on the protein surface. Different nuclear localized proteins may share the same NLS. An NLS has the opposite function of a nuclear export signal, which targets proteins out of the nucleus.
  5. e
    Stroma (fluid), the fluid in between grana, where carbohydrate formation reactions occur in the chloroplasts of plant cells photosynthesizing

5 Multiple choice questions

  1. A system of specialised long filament like proteins found in the cytosol of eukaryote cells which forms the constantly changing 'scaffolding'. They have many roles such as movement of motile cells, transport of organelles around the cell and intracellular movement of chromosomes during mitosis.

  2. Also known as actin filaments,one of three protein sub units that make up the eukaryote cytoskeleton. Found in highest concentration around the edges of the cell just below the cell membrane, they tend to form bundles. Actin polymers have the ability to disassemble and re-assemble meaning they are particulary useful for cell locomotion and in the microvilli of absorptive epithelial cells.

  3. Also known as A and Ade, this is a nucleobase (a purine derivative) with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD), and protein synthesis, as a chemical component of DNA and RNA.[2] The shape of adenine is complementary to either thymine in DNA or uracil in RNA.

  4. Junctions present in many types of animal tissue which serve to hold the constituentcells to each other and to the surrounding extra cellular matrix. They all have a common general structure consisting of transmembrane protein molecules known as cadhedrins.

  5. This protein plays a major role in the formation of coated vesicles. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskelia interact they form a polyhedral lattice that surrounds the vesicle. Coat-proteins, like clathrin, are used to build small vesicles in order to safely transport molecules between cells. The endocytosis and exocytosis of vesicles allows cells to transfer nutrients, to import signaling receptors, to mediate an immune response after sampling the extracellular world, and to clean up the cell debris left by tissue inflammation. On occasion, this mechanism also provides a pathway for raiding pathogens or toxins.

5 True/False questions

  1. ATP synthase
    Internal compartments formed by the inner membrane of a mitochondrion. They are studded with proteins, including ATP synthase and a variety of cytochromes. The maximum surface for chemical reactions to occur is within the mitochondria. This allows cellular respiration (aerobic respiration since the mitochondrion requires oxygen) to occur.


  2. Isocitrate
    An isomer of citrate formed after the T2 reaction in the TCA cycle.Isocitrate is formed from citrate with the help of the enzyme aconitase, and is acted upon by isocitrate dehydrogenase.


  3. Mitochondrial Matrix
    Sausage shaped organelles with a double membrane. The inner membrane folds in to cristae. This organelle plays a fundamental role in the production of ATP in eukarayote cells and they are abundant in cells which require high amounts of energy such as muscle cells.


  4. Biosynthetic-Secretory pathway
    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.


  5. Fatty Acid
    A generic term for the N- or O-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone. It is the sugar present on cadherins and N-CAMS which gives them their negative charge. It is also the name for the most common member of this group, N-acetylneuraminic acid (Neu5Ac or NANA). Sialic acids are found widely distributed in animal tissues and to a lesser extent in other species ranging from plants and fungi to yeasts and bacteria, mostly in glycoproteins and gangliosides. The amino group generally bears either an acetyl or glycolyl group but other modifications have been described. The hydroxyl substituents may vary considerably: acetyl, lactyl, methyl, sulfate, and phosphate groups have been found.