Chapter 24. The Chemistry of Life. Molecules of Life. Many of the most important molecules in our body are polymers. Proteins (amino acids), polysaccharides– ( monosaccharides ) and nucleic acids (nucleotides),. lipids are not polymers, no repeating units (monomers).
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Chapter 24 The Chemistry of Life
Molecules of Life Many of the most important molecules in our body are polymers. • Proteins (amino acids), • polysaccharides– (monosaccharides) and • nucleic acids (nucleotides), • lipids are not polymers, • no repeating units (monomers)
Molecules of Life In our diet, we need relatively large amts of • proteins, • carbohydrates, and • lipids. Organic cpds Nucleic Acids • Biomolecules for heredity and protein synthesis.
Biochemistry • Biochemistry • study of the chemistry of living things. • explores the substances involved in life processes and the rxns they undergo. • Other than H2O (about 80 % or more of the weight of an organism), most of the molecules of life—the biomolecules—are organic.
elemental composition of living things % By mass
Biochemistry • more than 95 % of the atoms in our bodies are H, O, C and N. • All 4 of these elements can form the strong covalent bonds found in organic molecules.
Biochemistry • S and P → proteins
Proteins • A protein: • an organic polymer composed of amino acids bonded together in one or more chains. • Monomer: amino acids • An amino acid • has a central C atom, to which are bonded a • carboxyl group(-COOH acid), • an amino group (-NH2), a H atom, and a variable side chain designated as R.
Proteins A protein • A peptide with more than about 100 amino acids. • structural proteins: skin, hair, nails, and muscles • ‘Functional’ proteins: enzymes, hormones • needed for almost all chemrxns that take place in the body.
Proteins Amino Acids in a Peptide Chain
Amino Acids An amino acid • cpd that contains an amino group (—NH2) and a carboxyl group (—COOH) in the same molecule.
Structure of an Amino Acid • Amino acids bond to each other by forming a peptidebond
Structure of an Amino Acid • 2 amino acids linked by a peptide bond form a dipeptide.
Structure of an Amino Acid • A Peptide: • A chain of 2 or more AAs linked by peptide bonds . • Polypeptide: • a chain of 10 or more AAs. • Proteins • may have 1 or several polypeptide chains, • each chain must have an exact sequence of AAs.
Enzymes • Enzymes • proteins • catalyzebiochemicalrxns • speeding up rxns • lower Ea
Enzymes • Substrates • The reactants in an enzyme-catalyzed process. • bind to the enzyme’s active site, • forming an enzyme-substrate complex. • enables the substrate(s) to react with a much lower Ea than …
The Nature of Enzyme Catalysis B A ●Enzyme provides a catalytic surface ●This surface stabilizes transition state ● Transformed transition state to product B A Catalytic surface Juang RH (2004) BCbasics
Enzyme Stabilizes Transition State Reaction direction Energy change ST Energy required (no catalysis) Energy decreases (under catalysis) EST S ES P EP T = Transition state
Carbohydrates • Familiar carbohydrates include glucose, sucrose, starches, and cellulose. • Simple carbohydrates consist of • a chain of C atoms • hydroxyl (–OH) groups and • a carbonyl gp, often in the form of an (alkanal) aldehydegp.
Monosaccharides • monosaccharides • The simplest carbohydrates (simple sugars) • e.g. glucose, ribose, fructose, deoxyribose
Polysaccharides • Polysaccharide • A polymer of many monosaccharides bonded into a chain. e.g. Starch consists only of glucose units.
Polysaccharides Plants also link glucose units together in a different way to form the polysaccharidecellulose
Polysaccharides • Glycogen • Animals store glucose as a polysaccharide
Lipids • Lipids • Fats and oils—produced by living things. • not polymers, • Digestion → fatty acids and glycerol • chem structures vary widely.
Triglycerides Lipids: • Fats, oils, and other water-insoluble cpds.
Fatty Acids • The most familiar lipids : plant oils and animal fats. • These lipids are esters of fatty acids, which are • alkanoic acids • with long, straight hydrocarbon chains • between 12 and 24 C atoms.
Saturated Fatty Acid • The simplest fatty acids are the saturated fatty acids, • no C ═ C double bonds between C atoms. • Stearic acid is found in pork and beef tissue.
Monounsaturated Fatty Acid • Many other fatty acids have 1 or more double bonds between C atoms →unsaturated fatty acids. • Oleic acid is a major component of olive oil.
Triglycerides Animal fats and plant oils are made up primarily of triglycerides, molecules in which 3 fatty acids are bonded to a glycerol molecule (by ester linkages).
The Functions of Lipids • long-term storage of energy is usually in the form of lipids. (more effective than carbohydrates.) • an important component of our skin and cell membrane.
DNA and RNA nucleic acids • polymers • found primarily in cell nuclei. • monomer: nucleotide • 2 kinds: • deoxyribonucleic acid (DNA) • ribonucleic acid (RNA)
DNA and RNA nucleotides. Each consists of a • phosphate group, • a five-carbon sugar, and • a nitrogen base.
Nucleic Acids 2 types of nucleic acids • DNA contains the sugar deoxyribose • RNA contains the sugar ribose. DNA • exists as a pair of polymer chains • backbone of each chain consists of alternating phosphate and deoxyribose units. • The bases stick out from the backbone.
The Structure of DNA A single DNA molecule contains many thousands of nucleotides.
Base Pairing • the N bases of 1 chain are H-bonded to the N bases of the other chain. • the chains wind into a spiral called a double helix.
Base Pairing 4 different N bases are found in DNA: • adenine, • guanine, • cytosine, and • thymine. • Adenine— thymine (H-bond) • Guanine— cytosine.
Base Pairing • The orderof these 3 N bases along 1 of the DNA chains provides the informn for the sequences of AAs in proteins. • Cell mechanisms “read” the DNA sequence in gps of three bases called triplets. • Each triplet codes for a specific AA or tells the cell to start or stop making a protein.
The Genetic Code A gene • a segment of DNA • carries the instructions for making 1 peptide chain. • The products of genes are the peptides and proteins.
Question 1 Label the amino group and the carboxyl group of the dipeptide.
Question 2 Draw an arrow pointing to the peptide bond.
Question 3 Draw a square around each variable side chain.