BIO CH 9

Which of the following is the most correct interpretation of the figure?

ATP is a molecule that acts as an intermediary to store chemical energy for cellular work. ATP is a renewable resource that can be regenerated by the addition of inorganic phosphate (Pi) to ADP. Energy released by catabolism in the cell is used to phosphorylate ADP, regenerating ATP. Chemical energy stored in ATP drives most cellular work.

Which of the following is true for all exergonic reactions?

The reaction proceeds with a net release of free energy. Chemical reactions are classified based on their free-energy changes. An exergonic reaction proceeds with a net release of free energy, whereas an endergonic reaction is one that absorbs free energy from its surroundings. If a chemical process is exergonic (downhill), releasing energy in one direction, then the reverse process must be endergonic (uphill), using energy.

Which of the following is true of the energy levels of electrons in shells?

Valence electrons have a higher energy level than those in other filled shells. The negatively charged electrons of an atom are attracted to the positively charged nucleus. It takes work to move a given electron farther away from the nucleus, so the more distant an electron is from the nucleus, the greater its potential energy. The valence electrons, located in the outermost electron shell (the valence shell), have the highest energy level.

Two molecules with the chemical formulas C6H12O6 and C6H12O2 are probably

a monosaccharide and a fatty acid Monosaccharides generally have molecular formulas that are some multiple of the unit CH2O. Glucose (C6H12O6) is the most common monosaccharide. A fatty acid has a long carbon skeleton with a carbon at one end that is part of a carboxyl group (-COOH); the remainder of the skeleton consists of a hydrocarbon chain. The relatively nonpolar C-H bonds in the hydrocarbon chains of fatty acids are the reason fats are hydrophobic.

A covalent bond is likely to be polar when

one of the atoms sharing electrons is more electronegative than the other. When an atom is bonded to a more electronegative atom, the electrons of the bond are not shared equally and a polar covalent bond is formed. Such bonds vary in their polarity, depending on the relative electronegativity of the two atoms. Atoms that have similar (or the same) electronegativities will form a nonpolar covalent bond. For example, a C-H bond is nonpolar because C and H have similar electronegativities.