Absorption and neural control of digestion
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The document summarizes several key aspects of digestion and absorption in the small intestine: 1) Enterocytes in the small intestine have a turnover of around 5 days, with cells differentiating as they migrate up from crypts to villi before being shed. 2) Nutrients are absorbed across the intestinal cell membrane through mechanisms like active transport, passive diffusion, and facilitated diffusion after crossing several barriers. 3) Absorption of proteins involves breakdown into dipeptides/tripeptides/amino acids and reabsorption, while lipids require emulsification, enzymatic digestion, and reconstitution into triglycerides and chylomicrons.
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The document discusses the human digestive system. It explains that digestion breaks down large food molecules into smaller molecules that can be absorbed. Enzymes play an important role by speeding up digestion. The digestive system includes the mouth, esophagus, stomach, small intestine, large intestine and accessory organs like the liver and pancreas. Digestion involves both physical and chemical breakdown of food. Absorption takes nutrients into the bloodstream while assimilation incorporates them into body tissues. The small intestine contains villi with microvilli that increase absorption surface area.
6_1_Digestion_Eunji
1) Digestion of large food molecules is essential because molecules must pass through cell membranes to be absorbed and used. During digestion, food molecules are broken down into their smallest components like amino acids and monosaccharides that can then pass through membranes.
2) Enzymes are needed for digestion to break down food molecules. They lower the activation energy of reactions, allowing reactions to occur at normal body temperatures rather than higher temperatures.
3) The small intestine absorbs most digested nutrients through villi in its walls, which increase surface area for absorption into capillaries and lacteals. Nutrients are then transported throughout the body.
6.1 digestion
The document discusses the human digestive system. It explains that digestion breaks down large food molecules into smaller molecules that can be absorbed. Enzymes play an important role in speeding up digestion at body temperature. It lists the source, substrate, products and optimal pH for amylase, protease and lipase. Diagrams of the digestive system and villi are included to show their structures and roles in digestion, absorption and transport of nutrients.
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The document discusses the process of digestion and absorption in the small intestine, including how enzymes break down macromolecules, how villi and microvilli increase absorption surface area, and how different transport methods absorb breakdown products across the intestinal epithelium into capillaries and lacteals. It also provides examples of homework assignments related to the topic, such as producing a diagram of the digestive system and explaining starch digestion and transport to the liver.
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Carbohydrates are digested into monosaccharides like glucose, fructose, and galactose which are then absorbed in the small intestine. Glucose accounts for about 80% of absorbed monosaccharides and is actively transported into intestinal cells via sodium-glucose transporters, using the sodium gradient as an energy source. Galactose absorption is similar to glucose while fructose absorption occurs via facilitated diffusion without requiring sodium or energy. Absorption rates vary between sugars with galactose absorbing most rapidly, followed by glucose, then fructose and pentoses absorbing slowest. Health of the intestinal mucosa and various hormones can also impact carbohydrate absorption rates.
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1) Digestion of large food molecules is essential because molecules must pass through cell membranes to be absorbed and used. During digestion, food molecules are broken down into their smallest components like amino acids and monosaccharides that can then pass through membranes.
2) Enzymes are needed for digestion to break down food molecules. They lower the activation energy of reactions, allowing reactions to occur at normal body temperatures rather than higher temperatures.
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The document discusses the human digestive system. It explains that digestion breaks down large food molecules into smaller molecules that can be absorbed. Enzymes play an important role in speeding up digestion at body temperature. It lists the source, substrate, products and optimal pH for amylase, protease and lipase. Diagrams of the digestive system and villi are included to show their structures and roles in digestion, absorption and transport of nutrients.
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Carbohydrates are digested into monosaccharides like glucose, fructose, and galactose which are then absorbed in the small intestine. Glucose accounts for about 80% of absorbed monosaccharides and is actively transported into intestinal cells via sodium-glucose transporters, using the sodium gradient as an energy source. Galactose absorption is similar to glucose while fructose absorption occurs via facilitated diffusion without requiring sodium or energy. Absorption rates vary between sugars with galactose absorbing most rapidly, followed by glucose, then fructose and pentoses absorbing slowest. Health of the intestinal mucosa and various hormones can also impact carbohydrate absorption rates.
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Complex carbohydrates are polysaccharides made of long chains of monosaccharides that take longer to digest. Humans need to get most of their energy from complex carbs like glycogen, fiber, and starch. Simple carbs are sugars made of single or double monosaccharides and include natural sugars from fruits as well as refined sugars. Carbs are digested through enzymes in saliva and the small intestine that break them down into monosaccharides, which are then absorbed and used for energy or storage.
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1. Digestion breaks down carbohydrates into monosaccharides like glucose and fructose. Salivary amylase and enzymes in the small intestine like maltase, lactase, and sucrase aid in this process.
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This document discusses metabolism and nutrition. It explains that metabolism is the sum of all chemical reactions that break down molecules (catabolism) or build them up (anabolism) in the body. These reactions release or use energy. The three main macronutrients - carbohydrates, lipids, and proteins - undergo digestion and are used to meet the body's energy demands. A balanced diet and sufficient intake of calories is important for health. The metabolic rate depends on factors like age, gender, activity level, and can be modified through diet and exercise.
Vbspu prabhakar singh first sem_ biochem unit iii_ lipids
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Fat usually means any ester of fatty acids or mixture of such compounds most commonly those that occur in living beings or in food. Fat is used as the fatty components of foods and diet. Fats are best known members of a chemical group called the lipids.
Content
Classification
Functions
Sources
Digestion
Absorption
Deficiency and disorders of lipids
Essential fatty acid
Role of omega-3 & omega 6 fatty acids in physiological disorders
References
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The document discusses various topics related to nutrition including macromolecules that provide energy like proteins, carbohydrates, and fats. It describes the roles of the liver, vitamins, minerals, and enzymes in breaking down nutrients. Specific carbohydrates like monosaccharides, disaccharides, and polysaccharides are defined. The document also covers protein structure, fat types, cholesterol, blood sugar regulation, energy requirements, metabolic rate, and eating disorders like anorexia and bulimia.
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The document discusses lipid digestion and absorption. It begins by defining lipids and describing the organs involved in digestion. It then discusses the different types of lipases secreted in the oral cavity, stomach, and pancreas to break down lipids. The role of bile salts in emulsifying lipids in the small intestine is also covered. Finally, it summarizes how lipids are further digested by pancreatic lipases in the duodenum, absorbed via micelles, and transported to the liver within chylomicrons.
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Lipids.pdf
Lipids are organic compounds made of carbon, hydrogen and oxygen that are a major source of energy. They have several important functions including being a fuel source, maintaining structure, and supporting metabolism. Lipids are digested in the mouth, stomach and small intestine where enzymes break them down. They are then absorbed and transported before being used or stored. Lipid metabolism involves breaking down fatty acids to produce energy or synthesizing them. Deficiencies can result in diseases like skin disorders, mental illnesses and heart conditions.
Digestion
This document summarizes the human digestive system. It describes how digestion involves both mechanical and chemical breakdown of food. Mechanical digestion begins in the mouth through chewing, while chemical digestion occurs through enzymes secreted in the mouth, stomach, pancreas, and intestines. The digestive system is made up of the digestive tract, which includes the mouth, esophagus, stomach, small intestine, large intestine, and anus. Food moves through this tract as it is broken down and nutrients are absorbed for use by the body.
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The document provides information about four main types of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids. It defines each macromolecule and provides examples. Carbohydrates function as the primary energy source and are made up of saccharides. Lipids function for long-term energy storage and insulation and are made of fatty acids. Proteins have structural and functional roles in the body and are composed of amino acids. Nucleic acids involve genetic material and are made of nucleotides that contain nitrogenous bases, sugars, and phosphates. The document explains the monomers that make up each macromolecule and their basic structures.
Digestion And Absorption of Lipids (1).pptx
Lipids are digested and absorbed through a multi-step process. They are emulsified by bile salts and pancreatic enzymes in the small intestine. Pancreatic lipase breaks down triglycerides into fatty acids and monoacylglycerols. These products along with cholesterol and fat-soluble vitamins are incorporated into micelles for absorption by enterocytes. Enterocytes resynthesize triglycerides and package the lipids into chylomicrons for transport through the lymphatic system and bloodstream to tissues.
Digestion, absorption and transport of food
General Idea about absorption and digestion of various food nutrients. overview of digestion and absorption
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- 1. Copyright © 2006 by Elsevier, Inc. Figure 65-6; Guyton & Hall
- 2. Copyright © 2006 by Elsevier, Inc. Life Cycle of S.I. Enterocytes • Villi house self-renewing population of epithelial cells with a 5-day turnover. • Cell types in villus include: secretory cells, endocrine cells, goblet cells, and mature absorptive epithelial cells. • Cells in enterocyte lineage divide and differentiate as they migrate up crypts, becoming mature absorptive cells. • Enterocytes are shed into lumen to become part of ingesta to be digested and absorbed.
- 3. Copyright © 2006 by Elsevier, Inc. Mechanisms of Absorption • Four mechanisms are important in transport of substances across intestinal cell membrane - Active Transport - - primary - secondary (co-transport, counter-transport) - Passive Diffusion - Facilitated Diffusion - carrier mediated - Endocytosis
- 4. Copyright © 2006 by Elsevier, Inc. Absorptive Pathway of Nutrients 1. Mucous layer 2. Glycocalyx 3. Apical cell membrane 4. Cytoplasm of enterocyte 5. Basolateral cell membrane 6. Intercellular space 7. Basement membrane 8. Wall of capillary or lymph vessel • A nutrient must cross 8 barriers to be absorbed by blood or lymph
- 5. Copyright © 2006 by Elsevier, Inc. Stomach (2) Fluid Entering and Exiting the Gut Bile (1) 0 2 4 6 8 10 Volume (L/day) Diet (2) Pancreas (1) Saliva (1) S.I. (2) Duodenum and Jejunum (4) Colon (1.4) Ileum (3.5) Volume entering Volume absorbed Volume Excreted 100-200 ml
- 6. Copyright © 2006 by Elsevier, Inc. Sodium Absorption in Small Intestine Na+ Na+ Na+ Gl Gl Na+ Na+ Cl- Na+ Cl- Na+ H+ Na+ H+ P Na+ Na+ K+ K+ Cl- Cl- 1 2 3 4 Aldosterone increases Na+ reabsorption and K+ secretion in S.I. and colon.
- 7. Copyright © 2006 by Elsevier, Inc. Protein Digestion and Absorption Dipeptides and tripeptides Cytoplasmic peptidases Amino acids Di- and Tri- peptides Large peptides Free amino acids Carriers Peptidases Small amounts Amino acids Protein Pepsin Pancreatic proteases Carriers
- 8. Copyright © 2006 by Elsevier, Inc. Assimilation of Lipids – Overall Scheme Triglyceride Fatty acids & Monoglyceride Triglyceride Duodenum Enterocyte
- 9. Copyright © 2006 by Elsevier, Inc. Basic Steps of Lipid Assimilation • Most dietary lipid is neutral fat or triglyceride. Three main processes must occur for triglyceride to be absorbed into blood: - Emulsification - large aggregates of dietary triglyceride are broken down. - Enzymatic digestion - to yield monoglyceride and fatty acids. Both can diffuse into enterocyte. - Reconstitution of triglyceride and chylomicron formation
- 10. Copyright © 2006 by Elsevier, Inc. Assimilation of Lipids Emulsified fat 2-MG FFA FOOD lecithin bile salts lipase-colipase 2-MG FFA (micelles) bile salts micelles 2-MG FFA TG (enterocyte) apoprotein + TG chylomicrons lymph vessel
- 11. Copyright © 2006 by Elsevier, Inc. “Malabsorption” • Malabsorption as a general phenomenon is defined clinically in terms of fat malabsorption because fat can be measured easily in stool, unlike carbohydrates and proteins. • Motility disorders - moving through too rapidly • Digestion disorder - pancreatitis / cystic fibrosis - (not enough lipase) • Absorption disorder - tropical and nontropical sprue - resection of small intestine
- 12. Copyright © 2006 by Elsevier, Inc. Neural Control of GI Tract • Intrinsic Control - Enteric nervous system - Myenteric (Auerbach’s) plexus - Submucosal (Meissner’s) plexus • Extrinsic Control - Autonomic nervous system - Parasympathetic - mainly stimulates (Ach) - Sympathetic - mainly inhibits (NE)
- 13. Copyright © 2006 by Elsevier, Inc. Figure 62-4; Guyton & Hall