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5 Written questions

5 Matching questions

  1. Connexon
  2. pH Optima
  3. Cytochromes
  4. Post-translation modification
  5. Caveolae
  1. a
    A multisubunit protein which holds gap junctions together in animal cells.
  2. b
    Latin for little caves, singular: caveola, which are a special type of lipid raft, are small (50-100 nanometer) invaginations of the plasma membrane in many vertebrate cell types, especially in endothelial cells and adipocytes.These flask-shaped structures are rich in proteins as well as lipids such as cholesterol and sphingolipids and have several functions in signal transduction.They are also believed to play a role in endocytosis, oncogenesis, and the uptake of pathogenic bacteria and certain viruses.They are one source of clathrin-independent endocytosis involved in turnover of adhesive complexes.
  3. c
    The optimum pH in which an enzyme is most active, this is normally related to the normal environment of the enzyme, for example Pepsin has a pH optima of around 2, ideal for the acidic environment of the vertebrate stomach.
  4. d
    Membrane-bound hemoproteins that contain heme groups and carry out electron transport.
    They are found either as monomeric proteins (e.g., cytochrome c) or as subunits of bigger enzymatic complexes that catalyze redox reactions. They are found in the mitochondrial inner membrane and endoplasmic reticulum of eukaryotes, in the chloroplasts of plants, in photosynthetic microorganisms, and in bacteria.
  5. e This is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins.A protein (also called a polypeptide) is a chain of amino acids. During protein synthesis, 20 different amino acids can be incorporated to become a protein. After translation, the posttranslational modification of amino acids extends the range of functions of the protein by attaching it to other biochemical functional groups (such as acetate, phosphate, various lipids and carbohydrates), changing the chemical nature of an amino acid (e.g. citrullination), or making structural changes (e.g. formation of disulfide bridges).Also, enzymes may remove amino acids from the amino end of the protein, or cut the peptide chain in the middle. For instance, the peptide hormone insulin is cut twice after disulfide bonds are formed, and a propeptide is removed from the middle of the chain; the resulting protein consists of two polypeptide chains connected by disulfide bonds. Also, most nascent polypeptides start with the amino acid methionine because the "start" codon on mRNA also codes for this amino acid. This amino acid is usually taken off during post-translational modification.Other modifications, like phosphorylation, are part of common mechanisms for controlling the behavior of a protein, for instance activating or inactivating an enzyme.

5 Multiple choice questions


  1. 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.

  2. 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.
  3. 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.

  4. An enzyme catalysed process in which which ATP is made by transferring phosphate directly onto ADP from a phsphporylated carbon intermediate in the cytosol. This is the only way for cells without mitochondria to make ATP, such as red blood cells and the lens of the eye. It is also a main contributor of ATP for high energy cells such as those of the immune system.

  5. 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).

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. Connective TissueThe constant release of small amounts of a substances from the cell membrane.

          

  3. Oxaloacetate
    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.

          

  4. Integral membrane proteins
    Proteins found in the cell membrane which attached to only one side of the membrane.

          

  5. Nascent ChainThe name given to a growing polypeptide chain. Literally translated this word means beginning to exist or develop.