Cell Chemistry and Bioenergetics
THE CHEMICAL COMPONENTS OF A CELL
Living organisms are made of only a small selection of the 92 naturally occurring elements, four of which carbon (C), hydrogen (H), nitrogen (N), and oxygen (O).
The reactions inside a cell occur in an aqueous environment.
The atoms of these elements are linked together by covalent bonds to form molecules
Four Types of Non covalent Attractions Help Bring Molecules Together in Cells
hydrogen bonds
van der Waals attractions
electrostatic attractions
CATALYSIS AND THE USE OF ENERGY BY CELLS
The chemical reactions that a cell carries out would normally occur only at much higher temperatures than those existing inside cells.
Enzyme catalyzed reactions are connected in series, so that the product of one reaction becomes the starting material, or substrate.
catabolic
anabolic
Cells Obtain Energy by the Oxidation of Organic Molecules
All animal and plant cells are powered by energy stored in the chemical bonds of organic molecules.
Organisms must extract this energy in usable form to live, grow, and reproduce.
Oxidation refers to more than the addition of oxygen atoms, the term applies more generally to any reaction in which electrons are transferred from one atom to another. Oxidation in this sense refers to the removal of electrons, and reduction the converse of oxidation means the addition of electrons.
How Enzymes Find Their Substrates: The Enormous Rapidity of Molecular Motions
An enzyme will often catalyze the reaction of thousands of substrate molecules every second. Tis means that it must be able to bind a new substrate molecule in a fraction of a millisecond.
Rapid binding is possible because the motions caused by heat energy are enormously fast at the molecular level.
diffusion is every molecule in a cell collides with a huge number of other molecules each second.
ATP Is the Most Widely Used Activated Carrier Molecule
ATP is a convenient and versatile store, or currency, of energy used to drive a variety of chemical reactions in cells.
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Te most important and versatile of the activated carriers in cells is ATP
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ATP is synthesized in an energetically unfavorable phosphorylation reaction in which a phosphate group is added to ADP
HOW CELLS OBTAIN ENERGY FROM FOOD
Te constant supply of energy that cells need to generate and maintain the bio-logical order that keeps them alive comes from the chemical-bond energy in food molecules
Te proteins, lipids, and polysaccharides that make up most of the food we eat must be broken down into smaller molecules before our cells can use them.
Most of the ATP needed for general plant cell metabolism is synthesized in these mitochondria, using exactly the same pathways for the oxidative breakdown of sugars as in nonphotosynthetic organisms, this ATP is then passed to the rest of the cell