Organic compounds - Contain carbon & hydrogen, are covalently bonded Biochemistry Organic compounds - Contain carbon & hydrogen, are covalently bonded Inorganic compounds Water, salts, and many acids and bases acid HCl --> H+ (proton donor) + Cl- pH below 7 base NaOH --> Na+ (cation) + OH- , proton acceptor, pH above 7 salt NaCl --> Na+ (cation) + Cl- (anion), pH 7

Figure 2.14

Organic Compounds Carbohydrates Lipids Proteins Nucleic Acids

Contain carbon, hydrogen, and oxygen Function: source of cellular food Carbohydrates Contain carbon, hydrogen, and oxygen Function: source of cellular food Examples: Monosaccharides or simple sugars 6-carbon structural isomers Figure 2.14a

Figure 2.16

Figure 2.15a

Figure 2.17

Figure 2.15b

Disaccharides or double sugars Carbohydrates Disaccharides or double sugars Figure 2.14b

Polysaccharides or polymers of simple sugars Carbohydrates Polysaccharides or polymers of simple sugars Figure 2.14c

Starch vs. Cellulose (fiber)

Lipids Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates Examples: Neutral fats or triglycerides Phospholipids Steroids

Neutral Fats (Triglycerides) Composed of three fatty acids bonded to a glycerol molecule Neutral fats – found in subcutaneous tissue and around organs Figure 2.15a

Figure 2.19

Phospholipids – chief component of cell membranes Other Lipids Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group Phospholipids – chief component of cell membranes Figure 2.15b

Figure 2.20

Steroids – four interlocking hydrocarbon rings Other Lipids Steroids – four interlocking hydrocarbon rings cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones Figure 2.15c

Amino Acids Building blocks of protein, containing an amino group, NH2 and a carboxyl (acid) group COOH

Figure 2.23a

Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid Dehydration synthesis Hydrolysis Dipeptide Peptide bond + N H C R O H2O OH Figure 2.17

Structural Levels of Proteins Primary Secondary Tertiary Quaternary

Structural Levels of Proteins Figure 2.18a–c

Structural Levels of Proteins Figure 2.18b,d,e

Protein Denaturation Reversible unfolding of proteins due to drops in pH and/or increased temperature Figure 2.19a

Protein Denaturation Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes Figure 2.19b

Characteristics of Enzymes Most are globular proteins that act as biological catalysts Holoenzymes consist of an apoenzyme (protein) and a cofactor (usually an ion) Enzymes are chemically specific Frequently named for the type of reaction they catalyze Enzyme names usually end in -ase Lower activation energy

Characteristics of Enzymes Figure 2.20

Mechanism of Enzyme Action Enzyme binds with substrate Product is formed at a lower activation energy Product is released Active site Amino acids Enzyme (E) Enzyme-substrate complex (E-S) Internal rearrangements leading to catalysis Dipeptide product (P) Free enzyme (E) Substrates (S) Peptide bond H2O +

Nucleic acids are polymers of monomers called nucleotides. Each nucleotide consists of three parts: a nitrogen base, a pentose sugar, and a phosphate group

Nucleic Acids Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus Their structural unit, the nucleotide composed of N-containing base pentose sugar phosphate group Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) Two major classes – DNA and RNA

Deoxyribonucleic Acid (DNA) Double-stranded helical molecule found in the nucleus of the cell Replicates itself before the cell divides, ensuring genetic continuity Provides instructions for protein synthesis

Structure of DNA Figure 2.22b

Ribonucleic Acid (RNA) Single-stranded molecule found in both the nucleus and the cytoplasm of a cell Uses the nitrogenous base uracil instead of thymine Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA

Adenosine Triphosphate (ATP) Source of immediately usable energy for the cell Adenine-containing RNA nucleotide with three phosphate groups

Figure 2.29

The capacity to do work (put matter into motion) Types of energy Kinetic – energy in action Potential – energy of position; stored (inactive) energy

Forms of Energy Chemical – stored in the bonds of chemical substances Electrical – results from the movement of charged particles Mechanical – directly involved in moving matter Radiant or electromagnetic – energy traveling in waves (i.e., visible light, ultraviolet light, and X-rays) Energy is easily converted from one form to another (First Law of Thermodynamics) During conversion, some energy is “lost” as heat ( Second Law of Thermodynamics - Entropy)

An exergonic reaction - release of free energy Chemical reactions can be classified as either exergonic (exothermic) or endergonic (endothermic) An exergonic reaction - release of free energy lower potential energy in endproduct Fig. 6.6a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

An endergonic reaction is one that absorbs free energy from its surroundings. Endergonic reactions store energy greater potential energy in endproduct Sunlight- source of energy for photosynthesis Fig. 6.6b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

ATP couples exergonic reactions to endergonic reactions ATP (adenosine triphosphate) is a type of nucleotide consisting of the nitrogenous base adenine, the sugar ribose, and a chain of three phosphate groups. Fig. 6.8a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The bonds between phosphate groups can be broken by hydrolysis. ATP is regenerated by adding a phosphate group to ADP.

Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction. An enzyme is an organic catalyst. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Exergonic reaction requiring Activation energy Activation energy is the amount of energy necessary to push the reactants over an energy barrier. Fig. 6.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 2.26

Enzyme speed reactions by lowering EA. The transition state can then be reached even at moderate temperatures (body temperature). Enzymes hasten reactions that would occur eventually. enzymes are selective they determine which chemical processes will occur at any time. Fig. 6.13 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Enzymes are substrate specific A substrate is a reactant which binds to an enzyme at its active site. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings