Metabolism is all the chemical reactions that occur in an organism Cellular metabolism Cells break down excess carbohydrates first, then lipids Cells conserve amino acids 40% of the energy released in catabolism is captured in ATP Rest is released as heat Metabolism

Figure 25.1 Figure 25.1 An Introduction to Cellular Metabolism

Figure 25.2 Figure 25.2 Metabolic Turnover and Cellular ATP Production

Figure 25.3 Nutrient Use in Cellular Metabolism Figure 25.3

Figure 25.8

Lipolysis Lipids broken down into pieces that can be converted into pyruvate Triglycerides are split into glycerol and fatty acids Glycerol enters glycolytic pathways Fatty acids enter the mitochondrion Lipid catabolism

Figure Lipid Synthesis Figure 25.10

5 types of lipoprotein Lipid-protein complex that contains large glycerides and cholesterol Chylomicrons Largest lipoproteins composed primarily of triglycerides Very low-density lipoproteins (VLDLs) contain triglycerides, phospholipids and cholesterol Lipid transport and distribution

5 types of lipoprotein (continued) Intermediate-density lipoproteins (IDLs) Contain smaller amounts of triglycerides Low-density lipoproteins (LDLs) Contain mostly cholesterol High-density lipoproteins (HDLs) Equal amounts of lipid and protein Lipid transport and distribution

Figure Lipid Transport and Utilization Figure 25.11a

Figure Lipid Transport and Utilization Figure 25.11b

Essential amino acids Cannot be synthesized by the body in adequate supply Nonessential amino acids Can be synthesized by the body via amination Addition of the amino group to a carbon framework Protein synthesis

Figure Figure A Summary of the Pathways of Catabolism and Anabolism

Liver The focal point for metabolic regulation and control Adipose tissue Stores lipids primarily as triglycerides Skeletal muscle Substantial glycogen reserves Body has five metabolic components

Neural tissue Must be supplied with a reliable supply of glucose Other peripheral tissues Able to metabolize substrates under endocrine control Body has five metabolic components

Figure The Absorptive State Figure 25.15

From the end of the absorptive state to the next meal Body relies on reserves for energy Liver cells break down glycogen, releasing glucose into blood Liver cells synthesize glucose Lipolysis increases and fatty acids released into blood stream Fatty acids undergo beta oxidation and enter TCA The Postabsorptive state

Figure Metabolic Reserves Figure 25.16a

Figure The Postabsorptive State Figure 25.17

Act as co-factors in enzymatic reactions Contribute to osmotic concentrations of body fluids Play a role in transmembrane potentials, action potentials Aid in release of neurotransmitters and muscle contraction Assist in skeletal construction and maintenance Important in gas transport and buffer systems Aid in fluid absorption and waste removal Minerals

Are needed in very small amounts for a variety of vital body activities Fat soluble Vitamins A, D, E, K Taken in excess can lead to hypervitaminosis Water soluble Not stored in the body Lack of adequate dietary intake = avitaminosis Vitamins

Total of all anabolic and catabolic processes underway Basal metabolic rate (BMR) is the rate of energy used by a person at rest Metabolic rate