Integration of Metabolism in Energy, Protein and Lipids
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Transcript of Integration of Metabolism in Energy, Protein and Lipids
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Integration of Metabolism in Integration of Metabolism in Energy, Protein and LipidsEnergy, Protein and Lipids
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Metabolism Metabolism
• A term referring to all chemical reactions necessary to maintain life. Substances are constantly being broken down and built up.
– Catabolism: complex structures broken down into simpler ones (digestion)
– Anabolism: larger molecules are built from small ones (like AA’sproteins)
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The Nutrient PoolThe Nutrient Pool
• Contains all organic building blocks cell needs:– to provide energy– to create new
cellular components
6 categories of nutrients• Carbohydrates• Lipids• Proteins• Vitamins• Minerals• Water
Lipids release 9.46 C/gCarbohydrates release 4.18 C/gProteins release 4.32 C/g
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Carbohydrates Carbohydrates
• Dietary sources–Predominately plants–Sugars – fruits, honey, milk, candy, soda–Starch – grains, legumes, root veggies–Cellulose – veggies
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Carbohydrates, cont.Carbohydrates, cont.
• Uses in the body– Glucose is a major fuel to make ATP
• Carbohydrate digestion yields fructose and galactose, liver converts them to glucose before circulation
– *when glucose is in excess, it is converted to glycogen or fat and stored for later use*
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Lipids Lipids
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• Brown fat had a small molecule, more blood vessels, low ATP produced and make more EN than White fat (Birth animal)
• Wild animal had lean meat (low marbling) and more PUFA ( >30% total FA vs. 12% in domestic animal )
• FUFA in wild ani. made unfavour meat from FUFA-phospholipids
form.
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Lipids, cont.Lipids, cont.
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Glycogen & Lactic cycle ( Cori cycle)Glycogen & Lactic cycle ( Cori cycle)
Insulin moving glucose to glycogen (storage in liver, mm)
Glucagon activate glycogenolysis for glucose in Liver, and Lactic in MM.
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ProteinsProteins
• Dietary sources–Primarily animal products (eggs, milk,
meat)–Legumes, nuts, & cereals are nutritionally
incomplete because they are low in one or more essential AA’s
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Proteins, cont.Proteins, cont.
• Uses in the body– Structural materials (collagen, elastin, keratin)– Functional proteins (enzymes, hemoglobin, H’s)
• Hormonal controls– Anabolic hormones accelerate protein synthesis
• i.e. growth hormone, sex hormones, adrenal glucocorticoids, etc.
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Proteins, cont.Proteins, cont.
• Adequacy of caloric intake–For protein synthesis you must have
adequate intake of carb’s & fats for ATP production
»If not…dietary & tissue proteins are used for En
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Energy Yield of Aerobic MetabolismEnergy Yield of Aerobic Metabolism
• For 1 glucose molecule processed, cell gains 36 molecules of ATP:– 2 from glycolysis– 4 from NADH generated
in glycolysis– 2 from TCA cycle (through
GTP)– 28 from ETS
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Carbohydrate Synthesis Carbohydrate Synthesis and Breakdownand Breakdown
Figure 25–7
• Gluconeogenesis - the synthesis of glucose from noncarbohydrate precursors:– lactic acid, glycerol, & AA’s– Stores glucose as glycogen in liver and
skeletal muscle
• Glycogenesis - the formation of glycogen from glucose
• Glycogenolysis - Is the breakdown• of glycogen to
glucose
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LipolysisLipolysis
• Breaks lipids down into pieces that can be converted to pyruvic acid & channeled directly into TCA cycle
• Hydrolysis splits triglyceride into component parts:– 1 molecule of glycerol & 3 fatty acid molecules
• Different enzymes convert fatty acids to acetyl-CoA (beta-oxidation)
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Fat & Glucose in Non RuminantFat & Glucose in Non Ruminant
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Fat & Glucose in RuminantFat & Glucose in Ruminant
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3 Energy Benefits of Beta-Oxidation3 Energy Benefits of Beta-Oxidation
1. For each 2-carbon fragment removed from fatty acid, cell gains:
– 12 ATP from acetyl-CoA in TCA cycle– 5 ATP from NADH
2. Cell can gain 144 ATP molecules from breakdown of one 18-carbon fatty acid molecule
3. Fatty acid breakdown yields about 1.5 times the energy of glucose breakdown
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Free Fatty Acids (FFAs)Free Fatty Acids (FFAs)
• Are lipids that can diffuse easily across cell membranes
• In blood, are generally bound to albumin (most abundant plasma protein)
• Are an important energy source:– during periods of starvation when glucose
supplies are limited• Liver cells, cardiac muscle cells, skeletal
muscle fibers, etc. metabolize free fatty acids
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ProteinsProteins
• The body synthesizes 100,000 to 140,000 proteins:– each with different form, function, and
structure
• All proteins are built from the 20 amino acids
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Protein MetabolismProtein Metabolism
• Cellular proteins are recycled in cytosol:– peptide bonds are broken– free amino acids are used in new proteins
• If other energy sources are inadequate:– mitochondria generate ATP by breaking down
amino acids in TCA cycle
• Not all amino acids enter cycle at same point, so ATP benefits vary
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3 Factors Against Protein Catabolism3 Factors Against Protein Catabolism
1. Proteins are more difficult to break apart than complex carbohydrates or lipids
2. A by-product, ammonium ion, is toxic to cells3. Proteins form the most important structural
and functional components of cells
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Protein Synthesis Protein Synthesis
• The body synthesizes half of the amino acids needed to build proteins (Nonessential AA’s)– amino acids made by the body on demand
• 10 essential AA’s:– 8 not synthesized: isoleucine, leucine, lysine,
threonine, tryptophan, phenylalanine, valine, and methionine
– 2 insufficiently synthesized: arginine and histidine
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Summary: Pathways of Catabolism and Summary: Pathways of Catabolism and AnabolismAnabolism
Figure 25–12
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Metabolic InteractionsMetabolic Interactions
Body has 2 patterns of daily metabolic activity:
1. absorptive state 2. postabsorptive state
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The Absorptive StateThe Absorptive State
• Is the period following a meal when nutrient absorption • most excess metabolites will be converted to fat for storage if
not used in anabolism• carbs-->liver to covert to glu-->released to blood or makes &
stores glycogen & makes fat to release to blood for storage by adipocytes
• triglycerides-->FA’s + glycerol-->sk mm, liver cells, & adipocytes use FA’s as primary E source-->most FA’s & glycerol re-enter adipose tissue & reconvert to triglycerides for storage
• AA’s-->some to liver for deamination to keto acids-->Kreb’s for ATP formation or conversion to liver fat stores; liver uses some AAs for plasma protein synthesis but most go into general circulation for uptake by other body cells to use for anabolism
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The Postabsorptive StateThe Postabsorptive State
• When nutrient absorption is not under way (fasting state)• Primarily catabolic to maintain blood glucose levels w/in
normal range b/t meals– glycogenolysis in liver can maintain blood glu levels for ~ 4 hrs– glycogenolysis in skeletal mm - glucose cannot be released to
blood as w/liver (lacks all necessary enzymes) but…partial oxidation to pyruvic acid (or lactic acid) occurs-->goes to liver for conversion back to glucose & is released to blood
– lipolysis in adipose tissue & liver -->leads to glycerol-->liver converts to glucose & releases to the blood
– catabolism of cellular protein - primary source of blood glucose w/fasting (glycogen stores are depleted)-->AAs are deaminated & coverted to glucose in liver & are released to blood
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Glucose for EnergyGlucose for Energy
• enzymes break apart glucose – yielding energy
• inadequate supply of carbohydrates– ketone bodies (fat fragments) are an alternate
energy source during starvation– excess ketones can lead to ketosis: imbalance
of acids in body
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Protein MetabolismProtein Metabolism
• protein turnover– constant making and breaking of
proteins• frees amino acids to “amino acid pool”
– can be used to make body proteins– nonessential amino acids can be made from
other amino acids
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• amino acid pool– Excreat of nitrogens and made available for
energy• deamination
– make fat• amino acids are deaminated, nitrogen is
excreted, carbon is converted to fat and stored• protein-rich foods can cause weight gain
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Feasting and Fasting
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Feasting and Fasting
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FastingFasting
• several hours after a meal, glucose is used up
• protein is used for energy• shift to ketosis
– suppresses appetite
• hormones slow metabolism• eventually starvation
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Regulatory Hormones on MetabolismRegulatory Hormones on Metabolism
Table 25–1
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Basal Metabolic Rate (BMR)Basal Metabolic Rate (BMR)
• Is the minimum resting energy expenditure:– Involves monitoring respiratory activity– Energy utilization is proportional to oxygen
consumption
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Hormonal EffectsHormonal Effects
• Thyroxine:– controls overall metabolism
• Cholecystokinin (CCK):– suppresses appetite
• Adrenocorticotropic hormone (ACTH):– suppresses appetite
• Leptin:– released by adipose tissues– binds to CNS neurons that suppress appetite
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Heat ProductionHeat Production
• BMR estimates rate of energy use• Energy not captured is released as heat:
– serves important homeostatic purpose
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ThermoregulationThermoregulation
• The body produces heat as by-product of metabolism
• Increased physical or metabolic activity generates more heat
• Body controls heat gains and losses to maintain homeostasis
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