• 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 25.10 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 25.11 Lipid Transport and Utilization

Figure 25.11a

Figure 25.11 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 25.14

Figure 25.14 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 25.15 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 25.16 Metabolic Reserves

Figure 25.16a

Figure 25.17 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