The Biochemistry of Energy Transfer

The carbohydrates, fat, and proteins consumed are oxidized, and the energy that is released in the process is transferred to ATP (A). The key substance for this energy transfer is acetyl-coenzyme A (acetyl-CoA). Carbohydrates are converted to pyru-vate during glycolysis and then further to acetyl-CoA. The fatty acids resulting from hydrolysis of triglycerides are also broken down into this two-carbon key compound. Amino acids from proteins are either metabolized indirectly through a pyruvate...

N r w

Riboflavin Deficiency Symptoms

Thiamin in the Citrate Cycle Pyruvate n-P-P ) Pyruvate dehydrogenase (C5 aldose) (C, ketose) Transketolase (C, aldose) Glycerin aldehyde-5-P Sedoheptulose-7-P H,C C OPO,2 + Erythrose-4-P Thiamin is found in all animal foods (A). Good sources are several species of fish (e. g., farmed catfish, sole, Florida pompano) as well as liver and muscle, especially porcine (e.g., ham), and egg yolk. Good plant sources are whole grains, potatoes, legumes, soy milk, and acorn squash. Like most B...

Homeostasis Leptin

Homeostasis Digestive System

A person's body weight is determined by the factors hunger satiation and energy intake energy use. Ever since hereditary forms of obesity were discovered in mice in the 1950s, researchers have investigated the regulation of these factors. About 20 years ago, it was found that the so-called ob mouse (for obese) is missing a satiety factor that would normally circulate in its blood. Finally, in 1994, the ob gene was cloned. The expression product, leptin, consists of 167 amino acids....

Basic Building Blocks The Amino Acids

The 20 amino acids (AA) used for protein synthesis are the proteinogenic amino acids (A). They are exclusively Lamino acids their D-enantiomers are biologically inactive. They can be divided into four categories, according to the chemical nature of their R-groups (exception glycine). AA with nonpolar side chains consist of a straight or branched hydrocarbon chain, or in methionine of a thioether group. They make up the hydrophobic core of proteins or are found in those protein sites that touch...

Preventive Nutrition The Mediterranean Diet

Mediterranean Diet Guide

Nutrition in accordance with the official guidelines could be considered as preventive, in spite of recent discussions about antioxidant vitamins, for instance. Nutrient data derived from scientific research provide an important foundation for institutional nutrition plans (e.g., hospitals, nursing homes) however, they are too abstract for the general consumer, who needs easy-to-apply nutritional recommendations. Translated into practical recommendations and compared to present intakes, a...

Introduction

Mycorrhiza Rice

Human foods are made up of essentially six basic component types (five groups of nutrients and water), each of which has different functions in the body (A). Carbohydrates and lipids represent our main energy sources. Proteins, vitamins, minerals, and trace elements are essential for growth and development of tissues. Water, proteins, and vitamins are needed for metabolism as well as for its regulatory functions. While energy nutrients (carbohydrates, lipids, proteins) are partially...

Classification

The term lipids refers to a group of substances that are insoluble in water and soluble in organic solvents. The easiest way to classify lipids is to divide them into classes according to structural characteristics (A). Chemically, these classes differ considerably. The polyprenyls class is based on the isoprene building block. They include steroids (e. g., cholesterol), fat soluble vitamins (vitamins A, D, E, K), and other terpenes (e. g., menthol). The largest branch of lipids is derived from...

Energy Requirements

Energy requirements should be stated as MJ (mega Joule) in reality, kcal (kilo-calories) are used more commonly. 1 MJ 239 kcal, and 1 kcal 4.184 kJ. A variety of models are available for the calculation of individual energy requirements. Here is a simple formula 1 kcal kg BW h is required to maintain basic metabolism (BMR). Light physical activity increases this amount by -V3 and moderate physical activity by 2A Intense physical activity doubles it. Here is an example A 70 kg man would have a...

Peter Grimm PhD

Institute of Biological Chemistry and Nutrition Sciences University of Hohenheim Stuttgart, Germany With the cooperation of Susanne Nowitzki-Grimm, Ph.D. Translated and adapted for the American market by Sigrid Junkermann, M.S., B.A., Adj. Asst. Prof. of Biology and Nutrition, F.I.T., SUNY Library of Congress Cataloging-in-Publication Data Biesalski, Hans Konrad Taschenatlas der Ern hrung. English Pocket atlas of nutrition Hans Konrad Biesalski, Peter Grimm with the co-operation of Susanne...

Enterohepatic Circulation

A number of substances that are absorbed into blood or lymph do not originate from foods but are released into the intestinal lumen endogenously. For instance, sloughed-off mucosa cells are digested and their components thereby recycled. The same applies to most intestinal secretions. Enterohepatic circulation is a prominent example of the body's substance-sparing tendency towards recycling. Bile acids, which are essential for the digestion of fat-soluble compounds, reach the duodenum A as...

From Chain to D Structure

Tertiary Structure Insulin

The DNA-determined sequence of amino acids in proteins is called their primary structure 1 A . This sequence contains all the information about the further behavior of the respective amino acid chain. The side chains R-groups of the individual amino acids predict the spatial arrangement of the protein. Today, the primary structure of even complex proteins is known. The first amino acid sequence discovered was that of insulin 1952 . Insulin is a comparatively simple protein, consisting of two...

Thiamin Chemistry Metabolism and Functions

Thiamin was the first of the water-soluble B vitamins to be identified as an essential nutrient. Chemically, it consists of a substituted pyrimidine ring A and a thiazole, connected by a methyl group. The term vitamin Bj encompasses several compounds with thi-amin-like effects. Naturally occurring Bj consists mostly of thiamin phosphates. In pharmaceuticals, water-soluble thiamin derivatives like thiamin hydrochloride or nitrate as well as lipophilic thiamin analogues like benfo-tiamine or...

Info

Energy Food Make Atp

Q,0Amino acids kinase complex lt Q,0Amino acids kinase complex lt The adult body makes and uses 85 kg 187 lb of adenosine triphosphate ATP per day. The energy in ATP A is stored in the high-energy bonds between the phosphates the terminal bond has the highest energy. Hydrolysis of these bonds B yields 8 kcal 33.47 kJ per 1 mol of ATP under physiological conditions. Additional energy can be obtained by further breakdown of ADP adenosine diphos-phate to AMP adenosine monophos-phate this reaction...

Vitamin D Functions

Vitamin Guide

The classic vitamin D function is to maintain calcium Ca and phosphate P homeostasis. Its cellular effects on intestinal Ca transport are best understood A . In the cytosol, 1,25- OH 2-D is probably bound to a cytosol receptor before being transferred to a DNA-asso-ciated nuclear receptor. This process induces the synthesis of several proteins, such as calcium-binding protein CaBP , an ATPase, alkaline phosphatase, phytase, etc. At the same time, lipid synthesis is increased, altering membrane...

Nutrient Compartmentalization Distribution to the Organs Homeostasis

Red Blood Cell Homeostasis

Nutrient intake, loss, metabolism, and requirements are subject to considerable changes over time and between individuals. Even intake can never be constant. This is in spite of the fact that most foods are always available nowadays, due to extensive world trade. Other factors like age, gender, or a person's state of health, lead to varying nutrient needs, different metaboliza-tion, and storage capacities. The fact that none of the measurable parameters have a normal value is a result of the...

Occurrence and Requirements

Only plant foods provide carbohydrates. Absolute carbohydrate in foods contents vary widely A . Contents in dry goods like grains or grain products are relatively high, whereas fruits contain only 10 weight in carbohydrates. Vegetables, with the exception of legumes, tend to be rather low in carbohydrates. The average adult needs at least 200 g glucose d for use by glucose-dependent organs. The brain alone needs 140 g d. At any age, at least 25 of caloric intake should come from carbohydrates...

The Colon

Names Colon Bacteria

The human large intestine colon is about 5 ft long and its largest diameter 2.4-3.6 in is in the cecum. Unlike the small intestine, its mucosa does not carry villi, but it does have crypts. It is characterized by extensive lymphatic tissue and plasma cells, especially in the area surrounding the appendix. Colonic contractions also differ from those of the small intestine. Circular musculature contracts in an irregular fashion and in several places at once, without any net movement of chyme....

Transcellular transport C can be

Cellulardiffusion

Electrogenic Na transport plays a central role as the driving force behind many absorptive processes. Na is pumped into the intercellular space by a Na pump located at the basolateral cell membrane. This process is ATP-dependent and creates an extreme difference between the Na concentration inside the cells 15 mmol l and the plasma 140 mmol l . Additionally, this creates a potential difference of about -40 mV between the two media. On the lumen side, the enterocytes are...

The recommended intakes are given in retinal activity equivalents RAE and

Fish Nutrition Chart

Range between 0.3 mg and 0.6 mg for children and are 0.7 mg and 0.9 mg, respectively, for females and males 1000 ag RAE 3000 IU see also p. 136 . During pregnancy and lactation the requirements are higher since plasma values in neonates are always lower than in the mother, and vitamin A use increases significantly during pregnancy. For this reason, supplementation of 0.7 mg d is recommended during pregnancy and 0.6 mg during lactation. Official recommendations state that liver should not be...

Listed in retinal activity equivalents

Vitamin Visual Cycle

For instance, 1 mg retinol, 1.15 mg retinyl acetate, or 6 mg p-caro-tene are 1 mg RAE. One mg RAE 3000 IU vitamin A. According to international chemical nomenclature IUPAC , vitamin A and its derivatives A are jointly called retinoids. The definition of this term has caused substantial confusion since it fails to differentiate between natural and synthetic vitamin A derivatives. In view of the biological medical aspects involved, the following distinction is made the term vitamin A...

Regulatory Functions Influence of Nutrition

Many studies have shown that fatty acid patterns can be affected by ingestion of particular fatty acids A . This opens the possibility of influencing cell membrane fluidity and associated membrane protein functions as well as eicosanoid synthesis through dietary measures. Many experiments are based on the administration of higher level homologues of the essential fatty acids, lino-leic and a-linolenic acid. The underlying assumption is that in certain diseases the first enzyme of the enzyme...

Nutrient Compartmentalization Cellular Distribution

Stored Ca2 Animal Cell

The distribution of carbohydrates, lip-ids, proteins, vitamins, and other elements and molecules in animal cells resembles that of human cells A while plant cells differ considerably B . In animal cells, carbohydrate reserves are stored as glycogen, and they can't store much of it. Their role as an energy reserve is of lesser importance since energy stored as fat uses space much more efficiently. Plants, except in seeds, don't have such problems of space and efficiency. They can, therefore,...

Absorption Cellular Mechanisms

Biochemical Absorption Mechanism

The digestive process in the small intestine is induced by free mostly pancreatic enzymes, at least for most nutrients. The final breakdown into the smallest molecules, ready for absorption, is achieved by membrane-bound enzymes at the microvilli A . The active sites of these enzymes are oriented towards the lumen side, achieving the final complete breakdown of nutrient molecules as they migrate towards the enterocytes. Actual absorption can happen in 3 ways B 1. Carrier-mediated transport is...

Vitamin A Uptake and Metabolism

Vitamin A can be obtained either as the provitamin mostly p-carotenes from plant sources or as its fatty acid ester RE retinyl ester from animal sources. The lipophilic retinyl esters RE are hydrolyzed by a pancreatic lipase cholesterol esterase during lipid digestion A . Retinol R is absorbed into the mucosa cells where it is reesterified in one of two ways retinol supplied at physiological levels is first bound to a specific cellular retinol-binding protein CRBP II . If supplied in very large...

Glucose Tolerance

Glucose Tolerance Bread

Glucose tolerance is the body's reaction to an increased carbohydrate supply. It is measured by reactive changes in blood glucose levels. During a glucose loading test, 50-100 g of glucose are administered on an empty stomach in 0.5 l of water, and blood glucose levels measured at time 0 start , and 30, 60, 90, and 120 minutes thereafter. Since glucose dissolved in water undergoes no digestive processes and passes an empty stomach without delay, the blood glucose level peaks 30 minutes after...

Glucose Homeostasis Insulin and Glucagon

Homeostasis Glucagon

All cells except brain, active muscle, and liver cells, require membrane transporters for glucose to enter the cells. The transporters are usually present inside the cells and insulin makes them available by bringing them to the cell surface with dropping insulin levels, they recede again. Insulin has three major metabolic effects Increasing glucose uptake in various tissues, Inhibiting gluconeogenesis. 2. It lowers blood fatty acids and enhances fat storage by Increasing glucose uptake by fat...

Absorption Anatomy and Histology

The small intestine can be divided into three sections the duodenum, which has important regulatory functions and receptors, with bile and pancreatic ducts leading into it the jejunum 1.52.5 m in length and the ileum 2-3 m in length . The intestinal tube is 4 cm in diameter and 5 m long, which would normally give it a surface area of 0.5 m2. Through the addition of folds, villi, and microvilli the absorptive surface increases to 200 m2. Each villus makes up a functional unit, together with its...

Smooth muscle cell proliferation

Lipoprotein Transport Distribution

Through stimulation of guanylate cyclase. These three factors leukocyte adhesion, proliferation, and subsequent platelet aggregation are of great significance in the initial phase of arteriosclerosis. The weakening of the Arg-NO system seems a likely pathogenetic factor in vascular lesions. Several variables are discussed as triggering factors for defects in NOS activity C reduced receptor coupling of the agonists, marginal substrate Arg or cofactor availability, or inactivation of EDRF NO on...

Tissue Specific Energy Metabolism

Energy Metabolism During Fasting

The brain depends almost exclusively on glucose for energy. Since it cannot store compounds for oxidation, it has to receive a constant supply of glucose. To make this possible, a minimum blood glucose level has to be maintained at all times A . The brain uses about 120 g of glucose per day during phases of prolonged fasting or starvation it can use ketone bodies instead, but only to a limited extent. Muscle tissue, on the contrary, possesses large glycogen stores. When broken down, it is...

Fatty Acids Metabolism

Palmitate Metabolism

Triglyceride triacylglycerol hydrolysis in adipocytes is subject to complex hormonal regulation A . Besides by glu-cagon, growth hormones, and others, hormone-sensitive lipase is activated, in particular, by catecholamines released during times of heightened energy need. Hormone-sensitive lipase is activated via a p-receptor and subsequent formation of the second messenger cAMP in the adenylate cyclase system. Hormone-sensitive lipase releases free fatty acids FFA from tri- and di-glycerides...

V

LCAT Lecithin-Cholesterol-Acyl-Transferase CEH Cholesterolester-Hydrolase LCAT Lecithin-Cholesterol-Acyl-Transferase CEH Cholesterolester-Hydrolase - B. Influence of Exogenous Cholesterol Supply - B. Influence of Exogenous Cholesterol Supply Compensator Plasma 210 mg dl 5.44 mmol l Compensator Plasma 210 mg dl 5.44 mmol l

Regulatory Functions The Blood Brain Barrier

Transport Neutral Amino Acid Brain

In the brain, so-called tight junctions between the endothelial cells of blood capillaries represent the blood-brain barrier. Lipophilic substances can pass this barrier, moving through the endothelial lipid bilayer. Also, O2-CO2 diffusion occurs along their partial pressure gradient. Water can diffuse through the tight junctions because of its small molecular size. All other polar substances need special transport systems to pass the blood-brain barrier A . For this, appropriate carriers have...

Ldl

Receptor Ldl

Since LDL particles primarily represent the transport form of cholesterol, their controlled uptake by the cells is essential. This occurs through an ApoBioo-and ApoE-specific receptor A . The interaction between ligand and receptor is based on their different charges on the ligand side, the apoproteins provide the alkaline amino acids lysine and arginine positive charge , while the active center of the receptor contains the acidic amino acids glutamic and aspartic acid negative charge . The...

Vitamin A Functions

Cis Retinyl Palmitate

Vitamin A does not act in a uniform manner. The various derivatives found in the body exert their effects through different functional mechanisms Retinol is a transport form and metabolic intermediate. Retinal is an essential component required for vision. Retinoic acid, in its cis-trans form, and its polar metabolites have pronounced effects on proliferation and differentiation of various tissues such as respiratory epithelium, intestinal mucosa, skin, and various tumor and embryonic cells....

Glucose Homeostasis Metabolic Aspects

Homeostasis Large Intestine

The blood glucose level of a healthy adult fluctuates between 70 mg dl 3.85 mmol l and 120 mg dl 6.6 mmol l postprandially. Beyond a certain blood glucose concentration of between 140 mg dl and 170 mg dl -7.7-9.35 mmol l depending on the individual , the kidney tubules are no longer capable of reabsorbing the glucose and glucosuria results. Below 50-70 mg dl -2.753.85 mmol l , the insufficient glucose supply to the CNS causes symptoms of weakness or fatigue. Further lowering may cause seizures,...

Homeostasis Hunger and Satiety

Homeostasis Hunger

The homeostasis of food intake is a complex process involving metabolic, endocrine, and neuronal processes. Due to their complexity this book can only provide a cursory overview A . Afferent control. Beyond visual and olfactory stimuli, taste plays a major role in regulating food intake. For example, metabolic effects of absorbed nutrients are either mediated directly by nutrient receptors or indirectly through a secondary change in the energy charge of liver cells. A multitude of...

Chemistry and Metabolism

Tocopherol Metabolism

First reports about a nutritional factor required to maintain pregnancy in rats appeared in the early 1920s. This factor was named vitamin E. a-tocopherol is the naturally occurring compound with the highest vitamin E activity A . It has three chiral centers at 2', 4', 8' in the figure at which the methyl groups are in R-configuration. According to IUPAC, the correct name is therefore 2R,4R,8R-a-tocopherol or short RRR-a-tocopherol. Naturally occurring a-tocopherol is usually accompanied by...

Hdl

Diagram Cholesterol Pathophysiology

HDL particles can be distinguished into discoidal disk-shaped and spherical ones. The discoidal ones are termed nascent n-HDL , the spherical ones mature HDL particles. Plasma contains mostly spherical particles with a hydrophilic core, consisting of triglycerides and cholesterol esters surrounded by phospholipids and apoproteins. The transition of the nascent to the spherical form is a result of cholesterol esteri-fication and uptake of cholesterol esters from the surroundings. Inside the...

Stomach Function

Stomach Anatomy Secretion

The stomach stores ingested foods, breaks them down mechanically, alters them chemically, disinfects them with stomach acid, and passes on the resulting chyme to the duodenum for further digestion in small portions. The proximal stomach A , also called fundus, develops an active tonus which can adjust to the intragastric pressure. Its primary function is, therefore, storage. Solid food is deposited layer upon layer while liquids run down the stomach wall. The distal stomach sections, corpus,...

Transport

Lipoprotein Continuum

Transport of lipophilic substances in watery media like blood or lymphatic fluid is dependent on the formation of particles with hydrophilic surfaces. This is achieved with the help of apoproteins A, B48, B100, C, and E . Their amphipathic structure allows them to mediate between the lipophilic particle cores and the hydrophilic medium. Depending on apoprotein compositions, different transport particles result. Apoproteins also function as markers for specific receptors in the tissues. Even...

Ascorbic Acid Chemistry Metabolism and Functions

Ascorbic Acid Function

The term vitamin C encompasses L- -ascorbic acid and its derivatives with identical levels of biological effects. Chemically, ascorbic acid is the enolic form of 3-oxo-L-gulofuranolac-tone A . Plants and many animals can synthesize it from glucuronic acid. Since humans, apes, and guinea pigs lack the last enzyme in the enzyme pathway, L-gulonolactone oxidase, the vitamin is essential for them. Vitamin C absorption begins at the buccal mucosa, but most of it is absorbed in the proximal small...

Lipid Digestion

Emulsion Lipid Colipase

Triglycerides with C16 and C18 fatty acids are of utmost quantitative importance for human nutrition. Whether fat is consumed in isolation or in emulsions, fat particles, regardless of their size, always contain additional lipophilic substances phospholipids, cholesterol and cholesterol esters, fat-soluble vitamins, and more. The subsequent digestion process takes up to 24 hours, due to limiting reactions. After ingestion, lingual lipase is mixed with the chyme A . The enzyme is active at low...

Vitamin K Chemistry Metabolism and Functions

Vitamin Function

The antihemorrhagic properties of vitamin K were first described in the 1930s the newly discovered factor was called coagulation vitamin. Besides the naturally occurring vitamins Ki phylloqui-none and K2 menaquinone , some additional quinones have vitamin K-like effects. The basic structure of vitamin K A is 1,4-naphtoquinone. Its vitamin activity depends on the methyl group in position two, while its fat solubility and other properties are due to the long side chains. Vitamin K2 is a...

Metabolism Distribution and Regulation

Adrenaline Triglycerides Hydrolysis

Once absorbed, carbohydrates are carried to the liver A . There, fructose and galactose are converted into glucose. Some of the absorbed glucose reaches the peripheral bloodstream, where it is recognized by pancreatic receptors. This triggers increased insulin secretion by the p-cells and reduces glucagon secretion. These hormonal changes provide a signal which affects the entire metabolism absorption of glucose into the liver, muscle cells, and fatty tissues is increased, and its conversion...

Lipoprotein Lipase

Lpl Heparan Sulfate

The activity of endothelial lipoprotein lipase LPL determines the various uptake levels of fatty acids in different tissues. LPL hydrolyzes triglycerides in high-triglyceride lipoproteins like chylomicrons and VLDL to 2-monoglycer-ides and fatty acids. It also effects the transfer of phospholipids and apopro-teins to HDL. Recent research shows that LPL is further responsible for specific binding of lipoproteins to cell surfaces and receptors. These functions point to a central role of the...

The RDA and DRI

Dri Nutrition

Early recommendations for nutrient intakes date back to the mid-1800s when, in the Lancashire district in England, nutrient intake recommendations were established because of a famine. The purpose, however, was solely to ensure adequate minimal nutrient intakes for the population and the army. In 1941, the U.S. National Research Council first issued recommendations which had the goal of achieving perfect health in the population. These Recommended Dietary Allowances RDA were updated in...

Digestion and Absorption

Protein Digestion Dipeptide Tripeptide

Protein digestion begins in the stomach, initiated by pepsins. Pepsins split peptide bonds involving Phe or Tyr R-groups. These endopeptidases split polypeptides inside the molecule are secreted by the gastric lining as inactive precursors, pepsinogens, which are activated at acidic pH. Acids further facilitate the enzymes' catalytic attack by denaturing the proteins. The activity of the gastric enzymes normally produces large fragments poly-, oligopep-tides . After stomach resections or in...

During the postabsorptive phase A

Postabsorptive Phase

The gastrointestinal tract, too, absorbs Gln, releasing Ala and cirtulline in turn. All AA are absorbed by the liver, the N released as ammonia, and the carbon skeleton processed for further use. Acidosis causes inhibition of hepatic Gln uptake. The kidneys then pick up Gln and convert it to ammonia, which combines with H ions that need to be excreted, forming NH4 . All H ions that need to be excreted due to acidosis are removed in this form. The AA Arg and...

Postprandial Lipid Distribution

Postprandial Lipid Metabolism

Lipids absorbed into the mucosa cells 1 after intraluminal hydrolysis A are re-esterified inside the cells and reach the circulatory system 2 in the form of chylomicrons via the lymphatic system. Chylomicrons CM can be found in the blood within 1-2 hours after a meal. With a half-life of 4-5 minutes, they are extremely short-lived however, after a high-fat meal, their influx continues for hours. After modification by lipoprotein lipase LPL, see p. 100 , the remnants are absorbed into the liver...

Fructose and Galactose

Fructose Galactose Metabolism

Fructose, which has no influence on the release of insulin, is metabolized in the liver A . Which metabolic pathway is used depends on the presence or absence of other monosaccharides. In case of simultaneous supply of glucose and fructose, fructose is transformed into intermediate products of the glycolytic pathway. Since only one phosphorylated product results from the splitting of fructose-1-phosphate, the remaining glyceraldehyde has to be processed via a different pathway first. Like...

Structure and Properties

Carbohydrates are hydroxylized aldehydes or ketones and are the most abundant of organic compounds. They serve as fuel, energy storage, basic building blocks in DNA and RNA, and as structural elements of bacterial and plant cell walls. Carbohydrates are bonded to other macronutrients in glycoproteins and glycolipids, which play important roles in cell membranes, as for instance in cell-cell recognition. Food carbohydrates are built almost exclusively from the monosaccharides, glucose, fructose,...

Metabolism Glucose Storage

Transamination

The glucose stored in the liver as glyco-gen can be considered a reservoir for buffering blood glucose levels A . Since glucose is the essential energy source of the CNS, blood glucose levels are regulated within a tight margin through the interplay of glucagon and insulin. Muscle glycogen is not directly integrated into the blood glucose regulation system. Since muscles lack glucose-6-phosphatase, their cells are unable to convert glucose-6-phosphate formed during glycogen breakdown into...