text stringlengths 471 10k |
|---|
milligrams per day of Fe, Cu, and Zn, even less of the others. The elemental requirements for plants and microorganisms are similar to those shown here; the ways in which they acquire these elements vary. 8885d_c01_013 1/15/04 3:28 PM Page 13 mac76 mac76:385_reb: form the strongest bonds. The trace elements (Fig. 1–12)... |
or out of cells. Proteins are perhaps the most versatile of all biomolecules. The nucleic acids, DNA and RNA, are polymers of nucleotides. They store and transmit genetic information, and some RNA molecules have structural and catalytic roles in supramolecular complexes. The polysaccharides, polymers of simple sugars ... |
all the chemical properties of tartaric acid, but in solution one type rotated polarized light to the left (levorotatory), the other to the right (dextrorotatory). Pasteur later described the experiment and its interpretation: Louis Pasteur 1822–1895 In isomeric bodies, the elements and the proportions in which they ar... |
in quantitative and chemical terms, the means by which energy is extracted, channeled, and consumed in living cells. We can consider cellular energy conversions—like all other energy conversions—in the context of the laws of thermodynamics. Living Organisms Exist in a Dynamic Steady State, Never at Equilibrium with The... |
g systems) is the means by which energy from fuel metabolism or light capture is coupled to a cell’s energy-requiring reactions. In thinking about energy coupling, it is useful to consider a simple mechanical example, as shown in Figure 1–26a. An object at the top of an inclined plane has a certain amount of potential ... |
ose 6-phosphate can therefore occur by reaction 3. The coupling of exergonic and endergonic reactions through a shared intermediate is absolutely central to the energy exchanges in living systems. As we shall see, the breakdown of ATP (reaction 2 in Fig. 1–26b) is the exergonic reaction that drives many endergonic proc... |
cussed in Chapter 15, have begun to offer important insights into the overall regulation of metabolism. Cells also regulate the synthesis of their own catalysts, the enzymes, in response to increased or diminished need for a metabolic product; this is the substance of Chapter 28. The expression of genes (the translatio... |
sequence complementary to one of the original strands. The result is two double-helical molecules, each identical to the original DNA. a three-dimensional cell. This change from one to three dimensions occurs in two phases. A linear sequence of deoxyribonucleotides in DNA codes (through an intermediary, RNA) for the pr... |
as catalysts in their own forma- 8885d_c01_033 12/20/03 7:09 AM Page 33 mac76 mac76:385_reb: Spark gap Condenser Electrodes Mixture of NH3, CH4, H2, and H2O at 80 °C FIGURE 1–33 Abiotic production of biomolecules. Spark-discharge apparatus of the type used by Miller and Urey in experiments demonstrating abiotic format... |
y acquiring greater motility, efficiency, or reproductive success than their free-living single-celled competitors. Further evolution of such clustered organisms led to permanent associations among individual cells and eventually to specialization within the colony—to cellular differentiation. The advantages of cellula... |
B Gene 1* Function 1 1 Gene duplication leads to a superfluous copy of gene 1 Homologous genes 1 and 1* are orthologs, encoding proteins of the same function in different species. Gene 1 Gene 1 copy Function 1 Function 1 2 Mutations in gene 1 copy give rise to gene 2. Gene 2 encodes a protein with a new, different func... |
nd Function, W. H. Freeman and Company, New York. Up-to-date discussions of stereochemistry, functional groups, reactivity, and the chemistry of the principal classes of biomolecules. Physical Foundations Atkins, P. W. & de Paula, J. (2001) Physical Chemistry, 7th edn, W. H. Freeman and Company, New York. Atkins, P.W. ... |
s long as 2 m—for example, the axons that originate in your spinal cord and terminate in the muscles of your toes. Small membrane-enclosed vesicles carrying materials essential to axonal function move along microtubules of the cytoskeleton, from the cell body to the tips of the axons. (a) If the average velocity of a v... |
try. We begin with water because its properties affect the structure and function of all other cellular constituents. For each class of organic molecules, we first consider the covalent chemistry of the monomeric units (amino acids, monosaccharides, nucleotides, and fatty acids) and then describe the structure of the m... |
stick and (b) space-filling models. The dashed lines in (a) represent the nonbonding orbitals. There is a nearly tetrahedral arrangement of the outer-shell electron pairs around the oxygen atom; the two hydrogen atoms have localized partial positive charges ( ) and the oxygen atom has a partial negative charge (2 ). (c... |
ater dissolves many crystalline salts by hydrating their component ions. The NaCl crystal lattice is disrupted ions. The ionic as water molecules cluster about the Cl and Na charges are partially neutralized, and the electrostatic attractions necessary for lattice formation are weakened. 8885d_c02_47-74 7/25/03 10:05 A... |
an der Waals radii. J. Phys. Chem. 96, 9194–9197. For covalent radii, Pauling, L. (1960) Nature of the Chemical Bond, 3rd edn, Cornell University Press, Ithaca, NY. Note: van der Waals radii describe the space-filling dimensions of atoms. When two atoms are joined covalently, the atomic radii at the point of bonding ar... |
ueous solutions. (a) At 101 kPa (1 atm) pressure, pure water boils at 100 C and freezes at 0 C. (b) The presence of solute molecules reduces the probability of a water molecule leaving the solution and entering the gas phase, thereby reducing the vapor pressure of the solution and increasing the boiling point. Similarl... |
pressed as the pH of the solution. To predict the state of ionization of solutes in water, we must take into account the relevant equilibrium constants for each ionization reaction. We therefore turn now to a brief discussion of the ionization of water and of weak acids and bases dissolved in water. Pure Water Is Sligh... |
End of preview. Expand in Data Studio
README.md exists but content is empty.
- Downloads last month
- 6