Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.Slide 1 Chapter 4 Cell Metabolism B. Souto

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.Slide 2 Introduction  To carry on its functions, the cell must metabolize its fuel ( raw material) : the CHO, proteins, and fats.

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.Slide 3 Metabolism  Metabolism the series of chemical reactions necessary for the use of raw material by the cell to maintain life.  Anabolism: includes the chemical reactions that build larger, more complex substances from simpler substances. Requires an input of ATP ( review pgs )  Catabolism: includes those chemical reactions that break down larger, more complex substances into simpler substances. Energy is released and captured as ATP.

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Carbohydrates: Structure and Function Carbohydrates: classified according to size and composed of: 1. Monosaccharides ( glucose is the most important of the 3 –six carbon simple sugars listed). Ribose and deoxyribose and 5-carbon monosaccharides used in the synthesis of RNA and DNA. 2. Disaccharides ( must be)____ before being absorbed across the walls of the digestive tract and used by the cells. 3. Polysaccharides ( see pg. 51). Slide 4 Glucose is the primary source of energy.

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Carbohydrates: Structure and Function cont’d  Glucose can be burned and used immediately as fuel for energy, stored as glycogen ( primarily in the liver and skeletal muscle), and burned as fuel at a later time, or stored as fat and burned as fuel at a later time.  Glucose can be catabolized anaerobically and aerobically. Anaerobically, glucose is incompletely broken down (glycolysis) into lactic acid and small amounts of ATP. Aerobically, glucose is broken down completely (citric acid cycle) into carbon dioxide (CO 2 ) and water (H 2 O) and large amounts of energy (ATP).  Glucose can be synthesized from nonglucose substances such as protein (gluconeogenesis) when BS gets ↓. Slide 5 The Kreb Cycle

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Lipids  The most common lipids are triglycerides, phospholipids, and steroids ( see Table 4-2).  Building blocks fatty acids and glycerol, they are of an organic nature, longer chains and have a more complex arrangement  Lipids are used primarily in the synthesis of membranes ( cells and myelin sheath) and steroids. A source of energy as well ( huge amount of ATP).  The long chains of fatty acids are broken down into two-carbon units and metabolized by the enzymes of the citric acid (Krebs) cycle into CO 2 and H 2 O, releasing large amounts of energy.  The extra donut eaten today is worn on your hip tomorrow! What does this mean?  What is the correlation between DM and utilizing of fats for glucose? See Case Study. Slide 6 Saturated vs. Unsaturated fats HDL vs. LDL

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Protein  The most important organic matter in the body.  Why are proteins Essential to Life?  Participates in every body function.  Almost every chemical reaction is regulated by enzymes, which are proteins.  Most hormones are proteins, Hgb, which delivers O2 to every cell in the body, is a protein and muscles contract because of contractile proteins.  Protein is composed of a series of amino acids linked together by peptide bonds in a specific sequence. Amino acids “AKA” building blocks of proteins.  Amino acids (Table 4-3)  Essential amino acids (cannot be synthesized)  Nonessential amino acids (can be synthesized by the liver). Slide 7

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Protein  Non-essential amino acids are not VITAL to the body? True or False? Explain.  Define: peptide bond, peptide and polypeptide. Uses of Proteins: Uses of Proteins:  Proteins are used primarily in the synthesis of hormones, enzymes, antibodies, plasma proteins, muscle proteins, hemoglobin, and cell membranes.  Proteins are also used as fuel and as raw material for making glucose (gluconeogenesis). This is done when BS levels can’t be maintained by dietary CHO and glycogen stores ( anorexia/starvations). Not preferred source of fuel—Why?  There is special handling of protein nitrogen by the urea cycle. Why?  What could happen if there’s hepatic dysfunction?  What is the significance of the following dx. tests: BUN & Blood Ammonia level? Slide 8

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.Slide 9 Protein Synthesis and DNA  DNA (deoxyribonucleic acid) DNA (deoxyribonucleic acid) DNA (deoxyribonucleic acid)  DNA stores the code for protein synthesis.  DNA is a double-stranded series of nucleotides, arranged in a twisted-ladder formation.  A nucleotide is composed of a sugar, a phosphate group, and a base. For DNA, the sugar is deoxyribose, and the bases are adenine, thymine, cytosine, and guanine.  The genetic code is stored in a sequence of three bases.

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Protein Synthesis and DNA - cont’d RNA  The structure of ribonucleic acid (RNA) is similar to the structure of DNA, with the following differences: in RNA the sugar is ribose; RNA is single-stranded; and the RNA bases are adenine, uracil, cytosine, and guanine.  Two types of RNA include messenger RNA (mRNA) and transfer RNA (tRNA).  Protein Synthesis: five steps summarized in Figure 4-9. → Slide 10 a. Transcription b. mRNA in nucleus  cytoplasm (ribosomes) c. Translation d. Formation of the peptide bond between the amino acids e. The completed protein leaves the ribosome

Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc. Disorders of Metabolism ( pg. 62)  How do anticancer drugs affect protein synthesis?  Misreading the genetic code: mutations/drugs  Defective genetic code (e.g., PKU, sickle cell anemia) Slide 11