Chapter 4

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Chapter 4
2010-02-21 22:07:03
Bio 32

Cellular metabolism
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  1. Define Potential energy
    Potential energy is stored energy or the potential to do work.
  2. Define Kinetic energy.
    Kinetic energy is the energy of motion.
  3. What is an exergonic reaction
    Exergonic reactions release energy because the products have less energy than the reactants.
  4. What is an endergonic reaction
    Endergonic reactions trap some activation energy in the products when then have some more free energy than the reactants.
  5. State the 1st law of thermnodynamics
    1st law states that the total amount of energy in the universe is constant.
  6. State the 2nd law of thermodynamics:
    • 2nd law of thermodynamics state that processes mnove from state of order to disorder or entropy.
    • (higher entropy=more disorder)
  7. What is entropy?
    Entropy is a measure of disorder of a system.
  8. How are reaction rates measured?
    Reaction rates are measured by measuring the utilization rate of the reactants or measuring the production rate of the products.
  9. What are isozymes?
    Isozymes are isoforms(closely related variants) of enzymes. They are also known as isoenzymes and they differ in amino acids sequence but catalyze the same chemical reaction.
  10. What is the law of mass action?
    Law of mass ation states that if a system at equilibrium is distributed by a change in concentratino of one of the components or in temperatre or pressure, the system will shift until a new equilibrium is reached. All reactions have an equilibrium constant, K.
  11. Define catabolism
    catabolism= reactions that produce energy through the breakdown of large biomolecules(proteins, carbohydrates& lipids.)
  12. Define Anabolism.
    Anabolism is energy-utilyzing reactions that result in the synthesis of large biomolecules.
  13. What are five ways that cells regulate their metabolism?
    • 1. controlling enzyme concentrations
    • 2. producing modulators
    • - Feedback inhibition
    • 3. USing different enzymes for reversible reactions.
    • 4. Isolating enzymes within intracellular organelles.
  14. Maintaining optimum ratio of ATP to ADP
    ADP + Pi + energy <----> ATP
  15. Where in the cell does glycolysis take place and where does the citric acid cycle take place?
    Glycolysis- cytoplasm; citric acid cycle--mitochondria.
  16. What is the two carbon molecule that enters the citric acid cycle and combines with the four carbon oxaloacetate molecule that is the last intermediate in the cycle?
    Acetyl CoA
  17. What is meant by oxidatiob or reduction of a nolecule?
    Oxidation-Reduction- A molecule that gains electrons or loses H+ is reduced. Molecules that loses electrons or gain H+ are oxidized. (Mnemonic OIL RIG)
  18. If glucose can easily penetrate the cell membrane, why doesn't it leave the cell as fast as it diffuses in?
    Glucose rapidly combines with a phosphate to form glucose-6-phosphate which cannot diffuse out of the cell.
  19. Each of the metabolic pathways produces small amounts of ATP, but their most important contributions to ATP synthesis are_______________carried by_____________ to electron transport system in the mitochondria.
    high energy electrons; NADH and FACH2
  20. What does the glycolysis of one molecule of glucose yield (no oxygen needed)?
    1 glucose yields: 2NADH + 4 ATP(-2ATPs used in previous steps)= 2NADH+ 2 ATP net gain
  21. Another way to ask the same question: write a short word equation that summarizes glycolysis.
    Glucose+ 2NAD+ + 2ADP + 2Pi--> 2Pyruvate + 2 ATP + 2 NADH + 2H+ +2H2O
  22. What molecule is formed if the pathway into the mitochondria is blocked by the lack of adequate oxygen?
  23. What causes the variability in reported ATP yield in cellular respiration?
    • - Mitochondria often don't work up to capacity.
    • - e- from glycolysis NADH(in cytosol) are transferred randomly to mitochondial NADH or FADH2--giving varied yeild of ATP. (FADH=1.5 ATP and NADH = 2.5 ATP)
    • - leakage of H+ ions back into the matrix.
    • - The electron transport system stops if O2 is not present. NADH & FADH2 normally return to the citric acid cycle as NAD+ and FAD+ so citric acid cycle runs out of e- acceptors.
  24. What are the two basic chemical reactions for breading down large protein molecules?
    Hydrolysis of peptide bonds and deamination.
  25. Why is it said that "proteins are key to cell function:
    • - protein runs cell from day to day.
    • - protein enzymes control synthesis and breakdown of all molecules
    • - protein transporters and pores in membrane regulate movement of molecules.
    • - proteins form structural skeleton of cells & tissues.
    • - proteins synthesis is critical to cell function.
  26. How do only four nitrogenous bases in DNA code for more than 20 different amino acids? What are codons?
    Triplets of bases= 43 =64 different combinations(=amino acids) A codon is a triplet of bases that code for different amino acids.
  27. What is a gene?
    It is a region of DNA that has the information needed to make a functional piece of mRNA which can beused to make a protein.
  28. Explain how DNA is translated into protein.
    • 1. DNa sequence is used to create a piece of messenger RNA(mRNA)
    • 2. mRNA is processesed in the nucleus.
    • 3. Processed mRNA leaves the nucleus and enters cytosol where it directs translation, the assembly of amino acids into proteins.
    • 4. In the cytoplasm, mRNA works with transter RNA(tRNA) & ribosomal RNA(rRNA) to assemble amino acids into protein chains.
    • 5. New proteins are subjected to post-transitional modification(folded, split or add various chem. groups)
  29. What are exons
    Exons= coding segments of mRNA(leave the nucleus & code for proteins)
  30. What are Introns
    noncoding segments of mRNA(spliced out of mRNA sequence and do not leave the nucleus)
  31. What is an anticodon and what does it do?
    3 sequence region on each tRNA that is complementary to an mRNA codon. Each tRNA molecule attaches art one end to a specific amino acid. The anticodon of the tRNA molecule pairs with the appropriate codon on the mRNA, allowing amino acids to be linked in the order specified by the mRNA code.
  32. What are some of the ways that proteins can be changed by post-translational modification?
    • 1. protein foldingcreates tertiary structure)
    • 2. cross-linkage (strong covalent bonds--> ie: disulfide bonds)
    • 3. Cleavage(split) into fragments
    • 4. addition of other molecules or groups
    • 5. Assembly into polymeric proteins(i.e: multiple subunits)