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Chapter 28

Absorption of Nutrients

Carbohydrates: Dietary Sources and Requirements
Carbohydrates: Dietary Sources and Requirements
Carbohydrates are a fundamental part of the human diet, primarily acquired from milk and edible plant sources. The primary sugars  — ...
Proteins: Dietary Sources and Requirements
Proteins: Dietary Sources and Requirements
Proteins are essential macronutrients for the human body. They serve as vital structural materials, such as keratin and collagen, and functional proteins, ...
Lipids: Dietary Sources and Requirements
Lipids: Dietary Sources and Requirements
Dietary lipids, or fats, primarily comprising triglycerides, are essential to human nutrition. Saturated fats predominantly come from meat, dairy, and ...
Vitamins
Vitamins
Dietary vitamins are essential as they facilitate the utilization of various other nutrients. They predominantly act as coenzymes, assisting different ...
Minerals
Minerals
Minerals are elements that work with other nutrients to ensure healthy body function. The human body primarily requires seven minerals — calcium, ...
Overview of Carbohydrate Metabolism
Overview of Carbohydrate Metabolism
During digestion, polysaccharides are broken down into simple sugars. After their absorption in the GI tract, glucose is transported into other cells ...
Overview of Protein Metabolism
Overview of Protein Metabolism
During digestion, proteins are broken down into smaller peptides and amino acids, which are absorbed. The amino acids are not stored for later use. ...
Overview of Lipid Metabolism
Overview of Lipid Metabolism
Lipid metabolism includes lipolysis and lipogenesis. In lipolysis, dietary triglycerides are converted into fatty acids and glycerol, producing ATPs ...
Cholesterol: Significance and Regulation
Cholesterol: Significance and Regulation
The liver synthesizes most cholesterol from acetyl CoA and transports it to the blood through lipoproteins. These lipoproteins are of three types. VLDLs ...
Carbohydrate Absorption
Carbohydrate Absorption
Digestion of carbohydrates, such as dietary starch, begins in the mouth with chewing and the action of the salivary amylase. After being partially ...
Protein Absorption
Protein Absorption
Proteins in the gastrointestinal tract primarily come from food but can also originate from disintegrated cells or secreted enzymes. In the stomach, these ...
Lipid Absorption
Lipid Absorption
In the duodenum, dietary triglycerides in chyme are mixed with bile salts. This process breaks down large fat droplets into smaller ones. Once emulsified, ...
Mineral, Vitamin and Water Absorption
Mineral, Vitamin and Water Absorption
Essential elements, including iron, calcium, sodium, chloride, and bicarbonate, are primarily consumed as dietary minerals or ions. While most ...
Metabolic States of the Body: The Absorptive State
Metabolic States of the Body: The Absorptive State
The absorptive state is a well-fed period lasting approximately four hours after a meal when the body absorbs nutrients from the gastrointestinal tract. ...
Metabolic States of the Body: The Postabsorptive State
Metabolic States of the Body: The Postabsorptive State
The postabsorptive state typically begins about four hours after a meal and lasts until the next meal is consumed. During this period, the digestive ...
Metabolic States of the Body: Fasting and Starvation
Metabolic States of the Body: Fasting and Starvation
During the initial hours of fasting, the body depletes its glycogen stores for energy. As glycogen stores diminish, the body begins the breakdown of ...
Energy Balance
Energy Balance
Energy is released when the chemical bonds in organic compounds, such as carbohydrates, proteins, and fats, are broken down. Food energy is measured in ...
Metabolic Rate
Metabolic Rate
The body's metabolic rate refers to the overall rate at which metabolic reactions consume energy. It can be measured as the total metabolic rate or ...
Body Temperature
Body Temperature
The average body temperature is 98.6 degrees Fahrenheit. At rest, metabolically active organs like the liver, heart, brain, and endocrine organs are vital ...
Mechanisms of Heat Transfer
Mechanisms of Heat Transfer
Heat is transferred between the body and its surroundings in four ways. Conduction is the heat transfer between molecules of two materials in direct ...
Thermoregulation
Thermoregulation
The body regulates core temperature through negative feedback mechanisms. When the core temperature drops, thermoreceptors send signals to the ...
Homeostatic Imbalances in Body Temperature
Homeostatic Imbalances in Body Temperature
Hyperthermia is an umbrella term for elevated body temperature that occurs when heat production exceeds the body's ability to dissipate it. ...
Regulation of Food Intake
Regulation of Food Intake
The hypothalamus releases peptides influencing feeding behavior. Two hypothalamic neuronal groups participate in this process. Neuropeptide Y (NPY) and ...
Obesity
Obesity
Obesity is a clinical condition marked by excessive body fat, with a BMI of 30 or higher, while a BMI of 18.5 to 24.9 is considered healthy. Excess ...
Inborn Errors of Metabolism
Inborn Errors of Metabolism
Genetic anomalies that disrupt metabolic processes cause inborn errors of metabolism. Phenylketonuria is an autosomal recessive protein metabolism ...
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