{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

CooperCh2Cell - 1 G M Cooper The Cell A Molecular Approach...

Info icon This preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
1 G. M. Cooper, The Cell: A Molecular Approach NIH Bookshelf url http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=books Ch. 2. The Molecular Composition of Cells Table of Contents Carbohydrates 4 Lipids (more detail at end) 7 Nucleic acids (more detail to come) 14 Proteins (more detail to come) 18 Cell Membranes 27
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 ] Cells are composed of water, inorganic ions, and carbon-containing (organic) molecules. Water is the most abundant molecule in cells, accounting for 70% or more of total cell mass. Consequently, the interactions between water and the other constituents of cells are of central importance in biological chemistry. The critical property of water in this respect is that it is a polar molecule , in which the hydrogen atoms have a slight positive charge and the oxygen has a slight negative charge (Figure 2.1 ). Figure 2.1. Characteristics of water (A) Water is a polar molecule, with a slight negative charge ( δ - ) on the oxygen atom and a slight positive charge ( δ + ) on the hydrogen atoms. Because of this polarity, water molecules can form hydrogen bonds (dashed lines) either with each other or with other polar molecules (B), in addition to interacting with charged ions (C). Because of their polar nature, water molecules can form hydrogen bonds with each other or with other polar molecules, as well as interacting with positively or negatively charged ions. As a result of these interactions, ions and polar molecules are readily soluble in water ( hydrophilic ). In contrast, nonpolar molecules , which cannot interact with water, are poorly soluble in an aqueous environment ( hydrophobic ). Consequently, nonpolar molecules tend to minimize their contact with water by associating closely with each other instead. As discussed later in this chapter, such interactions of polar and nonpolar molecules with water and with each other play crucial roles in the formation of biological structures, such as cell membranes. The inorganic ions of the cell, including sodium (Na + ), potassium (K + ), magnesium (Mg 2+ ), calcium (Ca 2+ ), phosphate (HPO 4 2- ), chloride (Cl - ), and bicarbonate (HCO 3 - ), constitute 1% or less of the cell mass. These ions are involved in a number of aspects of cell metabolism, and thus play critical roles in cell function. It is, however, the organic molecules that are the unique constituents of cells. Most of these organic compounds belong to one of four classes of molecules: carbohydrates, lipids, proteins, and nucleic acids . Proteins, nucleic acids, and most carbohydrates (the polysaccharides) are macromolecules formed by
Image of page 2
3 the joining ( polymerization ) of hundreds or thousands of low-molecular- weight precursors: amino acids, nucleotides, and simple sugars , respectively. Such macromolecules constitute 80 to 90% of the dry weight of most cells. Lipids are the other major constituent of cells. The remainder of the cell mass is composed of a variety of small organic molecules, including macromolecular precursors. The basic chemistry of cells can thus be understood in terms of the structures and functions of four major classes of organic molecules.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 Carbohydrates The
Image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern