Ch 3 - Energy, Catalysis and Biosynthesis Flashcards
acetyl CoA
activated carrier that donates the carbon atom in its readily transferable acetyl group to many metabolic reactions, including the citric acid cycle and fatty acid biosynthesis; the acetyl group is linked to CoEnzyme A (CoA) by a thioester bond that releases a large amount of energy when hydrolyzed
activated carrier
a small molecule that stores energy or chemical groups in a form that can be donated to many different metabolic reactions. examples include ATP, acetyl CoA and NADH
activation energy
the energy that must be acquired by a molecule to undergo a chemical reaction
anabolism
set of metabolic pathways by which large molecules are made from smaller ones
ADP, ATP
ADP - nucleoside diphosphate produced by hydrolysis of the terminal phosphate of ATP
biosynthesis
an enzyme-catalyzed process by which complex molecules are formed from simpler substances by living cells; also called anabolism
catabolism
set of enzyme-catalyzed reactions by which complex molecules are degraded to simpler ones with release of energy; intermediates i these reactions are sometimes called catabolites
catalyst
substance that accelerates a chemical reaction by lowering its activation energy; enzymes perform this role in cells
cell respiration
process by which cells harvest the energy stored in food molecules; usually accompanied by the uptake of O2 and the release of CO2
coupled reaction
linked pair of chemical reactions in which free energy released by one reaction serves to drive the other reaction
diffusion
process by which molecules and small particles move from one location to another by random, thermally driven motion
entropy
thermodynamic quantity that measures the degree of disorder in a system
enzyme
a protein that catalyzes a specific chemical reaction
equilibrium
state in which the forward and reverse rates of a chemical reaction are equal so that no net chemical change occurs
equilibrium constant K
for a reversible chemical reaction, the ratio of substrate to product when the rates of the forward and reverse reactions are equal
free energy G
energy that can be harnessed to do work, such as driving a chemical reaction
free-energy change (∆G)
in a chemical reaction, the difference in free energy between reactant and product molecules. a large negative value of ∆G indicates that the rection has a strong tendency to occur
metabolism
the sum total of the chemical reactions that take place in the cells of a living organism
NAD+, NADH
a molecule that accepts a hydride ion (H-) from a donor molecule, thereby producing the activated carrier NADH. widely used in the energy-producing breakdown of sugar molecules
NADP+, NADPH
molecule that accepts a hydride ion (H-) from a donor molecule, thereby producing the activated carrier NADPH; widely used as an electron donor in biosynthetic pathways
oxidation
removal of electrons from an atom, as occurs during the addition of oxygen to a carbon atom or when a hydrogen is removed from a carbon atom; can also refer to a partial shift of electrons between atoms linked by a covalent bond
photosynthesis
the process by which plants, algae and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water
reduction
addition of electrons to an atom, as occurs during the addition of hydrogen to a carbon atom or the removal of oxygen from it; can also refer to a partial shift of electrons between atoms linked by a covalent bond
standard free-energy change (∆G°)
the free-energy change measured at a defined concentration, temperature and pressure
substrate
a molecule on which an enzyme acts to catalyze a chemical reaction
