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5 Written questions

5 Matching questions

  1. Liposomes
  2. Chemiosmotic Hypothesis
  3. Saturated fatty acids
  4. Ligand
  5. Glutamate dehydrogenase
  1. a From the Latin ligandum, meaning binding, this is a substance that forms a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is a signal triggering molecule, binding to a site on a target protein.
    The binding occurs by intermolecular forces, such as ionic bonds, hydrogen bonds and van der Waals forces. The docking (association) is usually reversible (dissociation). Actual irreversible covalent binding between a ligand and its target molecule is rare in biological systems. In contrast to the meaning in metalorganic and inorganic chemistry, it is irrelevant whether the ligand actually binds at a metal site, as is the case in hemoglobin.
  2. b
    Glutamate dehydrogenase is an enzyme, present in most microbes and the mitochondria of eukaryotes, as are some of the other enzymes required for urea synthesis, that converts glutamate to α-Ketoglutarate, and vice versa. In animals, the produced ammonia is, however, usually bled off to the urea cycle. In bacteria, the ammonia is assimilated to amino acids via glutamate and amidotransferases. In plants, the enzyme can work in either direction depending on environment and stress. Transgenic plants expressing microbial GDHs are improved in tolerance to herbicide, water deficit, and pathogen infections.They are more nutritionally valuable.
  3. c The hypothesis of the movement of ions across a selectively permeable membrane, down their electrochemical gradient, generates energy. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration.
    An Ion gradient has potential energy and can be used to power chemical reactions when the ions pass through a channel.
    Hydrogen ions (protons) will diffuse from an area of high proton concentration to an area of lower proton concentration. Peter Mitchell proposed that an electrochemical concentration gradient of protons across a membrane could be harnessed to make ATP. He linked this process to osmosis, the diffusion of water across a membrane, which is why it is called chemiosmosis.
    ATP synthase is the enzyme that makes ATP by chemiosmosis. It allows protons to pass through the membrane using the kinetic energy to phosphorylate ADP making ATP. The generation of ATP by chemiosmosis occurs in chloroplasts and mitochondria as well as in some bacteria.
  4. d
    Saturated fatty acids are long-chain carboxylic acids that usually have between 12 and 24 carbon atoms and have no double bonds. Thus, saturated fatty acids are saturated with hydrogen (since double bonds reduce the number of hydrogens on each carbon). Because saturated fatty acids have only single bonds, each carbon atom within the chain has 2 hydrogen atoms (except for the omega carbon at the end that has 3 hydrogens).
  5. e
    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 Multiple choice questions

  1. A waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes and is required to establish proper membrane permeability and fluidity.It causes areas of rigidity in the membrane due to the interaction of its four fused ring sections with the hydrophobic tails of surrounding lipids.In addition, cholesterol is an important component for the manufacture of bile acids, steroid hormones, and vitamin D. Cholesterol is the principal sterol synthesized by animals; however, small quantities can be synthesized in other eukaryotes such as plants and fungi. It is almost completely absent among prokaryotes including bacteria. Although cholesterol is important and necessary for mammals, high levels of cholesterol in the blood can damage arteries and are potentially linked to diseases such as those associated with the cardiovascular system (heart disease).

  2. This matrix is secreted by cells and laid down externally and it's properties vary enormously depending on it's chemical composition and which tissue is being examined. In some cells it acts as cement or scaffolding. In plants it can be associated with individual cells.

  3. 9nm (approx) gaps in the nuclear envelope that allow the passage of RNA and ribosomes out of the nucleas and the entry of selected small proteins and small water soluble molecules.

  4. Alanine (abbreviated as Ala or A)[2] is an α-amino acid with the chemical formula CH3CH(NH2)COOH. It can be synthesized from the pyruvate intermediate of the TCA cycle. The L-isomer is one of the 22 proteinogenic amino acids, i.e., the building blocks of proteins. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid. L-Alanine is second only to leucine in rate of occurrence, accounting for 7.8% of the primary structure in a sample of 1,150 proteins.D-Alanine occurs in bacterial cell walls and in some peptide antibiotics.
  5. The release of substances from a cell membrane only when specific conditions exist. A good example is the release of gastrointestinal hormones and digestive enzymes in response to food.

5 True/False questions

  1. ATP synthase
    The precursor to several amino acids, including four that are essential for humans: methionine, threonine, isoleucine, and lysine. The conversion of aspartate to these other amino acids begins with reduction of aspartate to its "semialdehyde,"O₂CCH(NH₂)CH₂CHO.
    Asparagine is derived from aspartate via transamidation. Aspartate (the conjugate base of aspartic acid) stimulates NMDA receptors, though not as strongly as the amino acid neurotransmitter glutamate does.


  2. Oligonucleotide
    The basic building block of nucleic acids, such as DNA and RNA. It is an organic compound made up of nitrogenous base, a sugar, and a phosphate group.


  3. Active transport
    This form of transport is the movement of a substance against its concentration gradient (from low to high concentration). In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose, and amino acids. If the process uses chemical energy, such as from adenosine triphosphate (ATP), it is termed primary active transport. Secondary active transport involves the use of an electrochemical gradient. Active transport uses energy, unlike passive transport, which does not use any type of energy. Active transport is a good example of a process for which cells require energy. Examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.


  4. Feedback inhibition of regulatory enzymesThis equation can be used if a range of [S] values is known, to plot a line.
    E + S ↔ ES → E + P


  5. Allosteric Inhibitor
    A product produced later in a catalytic pathway which inhibits the activity of enxymes earlier in the catalytic pathway.