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Nutrition Chapter 7: Metabolism From Food to Life
Terms in this set (39)
Is sum of all chemical and physical processes by which the body breaks down and builds up molecules. Chemical reactions require or release energy and a calorimeter measures a food's caloric content.
Is the process of making new molecules from smaller one. Critical growth, repair, and maintenance and synthesis of body tissue, requires energy.
Is the breakdown or degradation of larger, more com[lex molecules to smaller, more basic molecules. During digestion, chemical reactions break down proteins, lipids, and carbohydrates, old tissues or cells are broken down for repair or replacement, and releases energy.
Adenosine Triphosphate (ATP)
Is an organic compound used by cells as a source of energy, energy is stored in phosphate bonds, when the bonds are broken, they release energy, this energy is used to do work of the cell, and it is the "currency" used by the body for energy.
Are chemical reactions that occur sequentially to achieve a particular goal. Occur in specific types or parts of the cell- may be limited to specific organs or tissues.
Is the site of energy production in the nucleus of a cell.
"Networking" of Metabolic Pathways
Liver, muscle, and adipose cells are key locations for the integration of metabolic pathways.
Anabolic process and water is released as a by-product.
Usually a catabolic process and a large molecule is broken apart with the addition of water.
Is the addition of a phosphate group to a compound. When the 2 high-energy phosphate bonds in ATP are hydrolyzed energy is released and phosphate is transferred to other molecules. When glucose goes through this, it can be oxidized for energy or stored as glycogen.
Molecules exchange electrons (hydrogen), and exchange reactions occur together.
A molecule giving up an electron because its electron is removed by oxygen.
Molecules securing an electron because in gaining an electron, it becomes more negatively charged.
Are protein that accelerate the rate of a chemical reaction.
Are nonprotein substances that enhance or are required for enzyme activity. Many B vitamins function as this.
Are required for enzyme activity and typically minerals: iron, zinc, and magnesium.
Energy from Carbohydrates
When glucose is transported to the liver, it is
Phosphorylated and metabolized for energy or stored as glycogen, released into circulation for other cells to use as fuel or stored as glycogen (muscle tissue), and converted to fatty acids, if glucose exceeds caloric needs, and stored as triglycerides in adipose tissue. Fructose and galactose are converted to glucose in the liver and follow the same fate.
First stage of glucose oxidation (breakdown), occurs in the cytosol, anaerobic reactions (no oxygen), and net production from this is 2 pyruvate, 2 ATP, and 2 NADH +H.
In the Absence of Oxygen
When oxygen becomes available, the liver converts lactate back to glucose. This is known as the Cori Cycle.
In the Presence of Oxygen
Aerobic (with oxygen) conversion of pyruvate to acetyl CoA, this reaction links the first and second stages of glucose oxidation, and the pyruvate was generated from glucose through glycolysis.
Acetyl CoA is generated as a results of the metabolism of:
CHO, fatty acid, amino acid, and alcohol.
Tricarboxylic Acid Cycle (TCA)
In the second stage of glucose oxidation, Acetyl CoA enters this cycle, and resulting in the release of carbon dioxide, GTP (ATP), and reduced coenzymes NADH and FADH2.
Electron Transport Chain
The third and final stage of glucose oxidation, additional ATP and water are produced as electrons from NADH and FADH2 are passed from one carrier to the next.
ATP produced in Glucose Oxidation
Energy from Fat-Lipolysis
Lipolysis of a triglyceride, dietary and adipose triglycerides are hydrolyzed by lipase to yield: one glycerol and 3 fatty acids, free fatty acids are used for energy or stored, and glycerol is converted to pyruvate, then to acetyl CoA for entry into the TCA cycle.
B-Oxidation of Fatty Acids
Attached to albumin, fatty acids are transported to working cells needing energy (such as liver or muscle cells), and fatty acids must be activated by Coenzyme A before shuttled across the mitochondrial membrane (from the cytosol) by carnitine.
Long chain fatty acids are sequentially broken down into two-carbon segments that lead to forming of acetyl CoA. A series of metabolic reactions that oxidize free fatty acids, producing: Carbon dioxide and ATP.
A 16 Carbon Fatty Acid Yields:
8 Acetyl CoA units, 8 FADH2, 8 NADH + H, and a total of 131 ATP.
Fatty Acids Cannot Form Glucose
There is no pathway to convert Acetyl CoA to pyruvate: Since Acetyl CoA cannot be converted to glucose, fatty acids cannot be converted to glucose, and in the absence of adequate CHO, ketones are used to supply the brain and RBC with fuel.
Energy from Protein
The body prefers using CHO and fat for energy, this is reserved for metabolic functions that cannot be performed by others: building and repairing tissues, and they are used for fuel primarily during low total energy or CHO intake.
Can be used during exercise, during times of sleep, fasting, or exercise. Extra energy is stored as CHO in limited amounts as liver and muscle glycogen, fat (triglycerides) in unlimited amounts, and the body has no mechanism for storing amino acids or nitrogen.
Making glucose from non-glucose substrates, primarily from Glucogenic amino acids, small amount from glycerol (triglycerides), and maintains blood glucose during sleep, fasting, illness, and exercise.
For glucose production can drawn on vital tissue proteins (skeletal and heart muscles and organ proteins).
Making fat from non-fat substances such as CHO, amino acids, and alcohol. Occurs when consuming excess calories, Acetyl CoA units assemble into fatty acids chains, fatty acids combine with glycerol to form triglycerides, and mostly occurs in liver cells.
Metabolism During Feeding
Bloodstream is enriched with glucose, fatty acids, and amino acids. Glucose is stored as liver and muscle glycogen, when glycogen stores are saturated glucose is stored as triglycerides, fatty acids are stored mostly as triglycerides in adipose tissue, and amino acids are deaminated and carbon skeleton are converted to fatty acids for storage as triglycerides.
Metabolism During Fasting
Liver glycogen is broken down releasing glucose into the blood, most cells can switch to using fatty acids as fuel to conserve glucose for brain and other cells that rely on glucose as fuel, ketones form as Acetyl CoA units are blocked from entering TCA cycle, and gluconeogenesis from the breakdown of muscle protein and glycerol.
Metabolism During Starvation
The body switches to starvation mode, blood glucose is maintained to support brain and RBC, activity, body temperature, and metabolism decline, fatty acids become primary fuel, and brain cells start to use ketone bodies as fuel, and muscle protein supplies glucose.
Is the primary anabolic hormone, increases in the blood after eating, activates storage enzymes, and signals cellular uptake of glucose, fatty acids, and amino acids.
Glucagon, Epinephrine, and Cortisol
Are catabolic hormones that trigger the breakdown of stored triglycerides, glycogen, and body protein for energy.
Recommended textbook explanations
Biocalculus: Calculus for the Life Sciences
Campbell Biology (AP Edition)
Cain, Jackson, Minorsky, Reece, Urry, Wasserman
Campbell Biology (AP Edition)
Cain, Campbell, Minorsky, Reece, Urry, Wasserman
Lehninger Principles of Biochemistry
David L Nelson, Michael M. Cox
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