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Semester 1: Macronutrients
Carbohydrates: Introduction, Classification based on degree of polymerization, digestion, functions, food sources, requirements, digestion, absorption and metabolic utilization, regulation of blood glucose concentration, glycemic index, dietary fibre types and functions
Carbohydrates
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Carbohydrates are essential macronutrients that provide energy to the body. They are organic compounds composed of carbon, hydrogen, and oxygen, typically found in foods such as grains, fruits, and vegetables.
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Carbohydrates can be classified into three main categories based on their polymerization degree: monosaccharides (simple sugars), disaccharides (two monosaccharides linked together), and polysaccharides (long chains of monosaccharides). Monosaccharides include glucose and fructose, disaccharides include sucrose and lactose, while polysaccharides include starch and cellulose.
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The digestion of carbohydrates begins in the mouth with the enzyme amylase in saliva, which breaks down starches into simpler sugars. In the small intestine, additional enzymes, such as maltase and lactase, further break down carbohydrates into monosaccharides.
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Carbohydrates serve multiple functions including providing energy, serving as a source of dietary fiber, and aiding in the regulation of lipid metabolism. They are critical for brain function as glucose is the primary fuel for nerve cells.
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Common food sources of carbohydrates include grains (rice, wheat), fruits (apples, bananas), vegetables (potatoes, carrots), legumes (beans, lentils), and dairy products (milk, yogurt).
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The daily carbohydrate requirement varies by individual but generally comprises about 45-65% of total daily caloric intake according to dietary guidelines. For adults, this typically equates to about 225-325 grams per day.
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Once carbohydrates are digested into monosaccharides, they are absorbed in the small intestine and transported to the liver. The liver converts excess glucose into glycogen for storage. When needed, glycogen can be converted back to glucose to maintain energy levels.
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The body regulates blood glucose levels through various mechanisms, primarily involving hormones like insulin and glucagon. Insulin helps lower blood glucose levels by promoting cellular uptake, while glucagon raises glucose levels by stimulating glycogen breakdown.
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The glycemic index (GI) is a ranking of carbohydrates based on their effect on blood glucose levels. Foods with a high GI can cause rapid spikes in blood sugar, while low GI foods result in a more gradual increase.
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Dietary fiber is classified into two types: soluble and insoluble fiber. Soluble fiber dissolves in water and helps lower blood cholesterol and glucose levels, while insoluble fiber adds bulk to stool and aids in digestion. Both types are essential for maintaining gut health and regularity.
Lipids: Introduction, Classification, Function, Food sources, Requirements, digestion, absorption, transport and storage, Lipids and gene expression, dietary fat and coronary heart disease, fatty acids types, functions, deficiency, Omega fatty acids
Lipids
Introduction
Lipids are a diverse group of hydrophobic organic molecules that are insoluble in water but soluble in organic solvents. They play crucial roles in biological systems including energy storage, structure of cell membranes, and signaling.
Classification
Lipids can be classified into three main categories: triglycerides (fats and oils), phospholipids, and sterols. Triglycerides are the main form of stored energy, phospholipids are key components of cell membranes, and sterols, such as cholesterol, play essential roles in membrane structure and function.
Function
Lipids serve various functions including energy storage, insulation, protection of vital organs, and formation of cellular membranes. They also participate in the synthesis of hormones and vitamins.
Food Sources
Common food sources of lipids include nuts, seeds, avocados, olive oil, fatty fish, dairy products, and meat. Different sources provide varying types of fatty acids and other lipid forms.
Requirements
The recommended intake of lipids varies based on dietary guidelines, typically constituting about 20-35% of total daily caloric intake. It's essential to focus on healthy fats while limiting saturated trans fats.
Digestion
Lipids undergo digestion primarily in the small intestine. Bile salts emulsify fats, allowing lipases to break them down into fatty acids and glycerol for absorption.
Absorption
Once digested, fatty acids and glycerol are absorbed through the intestinal membrane. They are then reassembled into triglycerides and packaged into chylomicrons for transport.
Transport and Storage
Lipids are transported through the lymphatic system and into the bloodstream. They are stored in adipose tissue, serving as an energy reserve.
Lipids and Gene Expression
Certain lipids can influence gene expression by acting as signaling molecules. For instance, fatty acids can modulate the activity of transcription factors and impact metabolic processes.
Dietary Fat and Coronary Heart Disease
The type of dietary fat consumed can influence the risk of coronary heart disease. Unsaturated fats are generally protective, while trans fats and excessive saturated fats can contribute to heart disease.
Fatty Acid Types
Fatty acids are categorized as saturated, monounsaturated, or polyunsaturated. Each type has different health implications and functions in the body.
Functions of Fatty Acids
Fatty acids are essential for energy production, formation of cell membranes, and as precursors for hormone production. They are vital to overall health.
Deficiency
Deficiency in essential fatty acids can lead to various health issues, including skin problems, impaired growth, and hormonal imbalances.
Omega Fatty Acids
Omega-3 and Omega-6 fatty acids are crucial for health, needed for normal growth and development, as well as for reducing inflammation and supporting heart health.
Proteins: Introduction, Classification, Functions, Requirements, Food sources, digestion, absorption and metabolic utilization of protein, quality of proteins, Amino acids types, functions, food sources, deficiency, therapeutic applications
Proteins
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Proteins are large, complex molecules made up of amino acids that play crucial roles in biological processes. They are essential for growth, repair, and overall functioning of the body.
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Proteins can be classified based on their structure into fibrous, globular, and membrane proteins. They can also be categorized by their function, such as enzymes, antibodies, and hormones.
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Proteins perform a variety of functions in the body, including enzyme catalysis, transport of molecules, structural support, immune response, and regulation of cellular activities.
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Protein requirements vary based on age, sex, and level of physical activity. The recommended dietary allowance for adults is approximately 46-56 grams per day.
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Common dietary sources of protein include meat, fish, eggs, dairy products, legumes, nuts, and certain grains.
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Protein digestion begins in the stomach where enzymes like pepsin break down proteins into smaller peptides. This process continues in the small intestine with enzymes from the pancreas.
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Amino acids and small peptides are absorbed primarily in the small intestine through active transport and facilitated diffusion into the bloodstream.
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Once in the bloodstream, amino acids are used for protein synthesis, energy production, or converted to other compounds as needed by the body.
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Protein quality is determined by its amino acid composition and digestibility. Complete proteins contain all essential amino acids in adequate amounts, while incomplete proteins lack one or more.
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Amino acids are classified into essential, which must be obtained from the diet, and non-essential, which the body can synthesize.
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Amino acids are crucial for protein synthesis, neurotransmitter production, hormone regulation, and energy metabolism.
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Essential amino acids can be found in animal products like meat and dairy, as well as in some plant sources like quinoa and soy.
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A deficiency in protein or essential amino acids can lead to a range of health issues including stunted growth, loss of muscle mass, and weakened immune function.
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Proteins and amino acids have therapeutic applications in conditions such as malnutrition, recovery from surgery, and muscle-wasting diseases.
Energy: Units, determination of energy value of food, physiological fuel value, basal metabolic rate, measurement and calculation, thermic effect of food, total energy requirement, factors affecting BMR and physical activity
Energy
Units of Energy
Energy is commonly measured in Joules (J), calories (cal), and kilocalories (kcal). 1 kcal equals 4184 J. The calorie is defined as the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.
Determination of Energy Value of Food
The energy value of food is determined through calorimetry, where the heat released during combustion of food samples is measured. The Atwater system provides specific energy values for carbohydrates, proteins, and fats.
Physiological Fuel Value
The physiological fuel value refers to the usable energy obtained from macronutrients during digestion and metabolism. Generally, protein and carbohydrates provide 4 kcal/g and fats provide 9 kcal/g.
Basal Metabolic Rate (BMR)
BMR is the amount of energy expended while at rest in a neutrally temperate environment. It is influenced by factors such as age, sex, body size, and composition.
Measurement and Calculation of BMR
BMR can be estimated using equations like the Harris-Benedict equation, which incorporates weight, height, age, and sex. Direct measurement can be done through calorimetry.
Thermic Effect of Food (TEF)
TEF is the energy required for digestion, absorption, and metabolism of food. It typically accounts for about 10% of total energy expenditure and varies by macronutrient.
Total Energy Requirement (TER)
TER is the total energy expenditure of an individual, considering BMR, physical activity, and TEF. It helps in understanding energy needs for maintaining body weight.
Factors Affecting BMR
BMR can be influenced by several factors including age, sex, hormonal levels, muscle mass, and temperature. Individuals with more muscle mass typically have a higher BMR.
Physical Activity and its Influence
Physical activity significantly affects total energy expenditure. The more active a person is, the higher their energy requirement. Factors such as intensity, duration, and frequency of exercise contribute to overall energy needs.
Water and electrolytes: Introduction, body composition, body water distribution, electrolyte content, regulation of body water compartments, metabolism, impact of pathological conditions
Water and Electrolytes
Introduction
Water is essential for life, serving as a solvent, transport medium, and participating in biochemical reactions. Electrolytes are minerals that dissolve in water and produce ions, crucial for various bodily functions.
Body Composition
Water constitutes about 60% of an adult's body weight. It is influenced by factors such as age, sex, and body fat percentage. Muscle tissue holds more water than fat tissue, impacting overall hydration status.
Body Water Distribution
Body water is distributed in different compartments: intracellular fluid (ICF) and extracellular fluid (ECF). ICF accounts for approximately two-thirds of total body water, while ECF includes interstitial fluid and plasma.
Electrolyte Content
Key electrolytes include sodium, potassium, calcium, magnesium, chloride, bicarbonate, and phosphate. These ions are vital for maintaining osmotic balance, acid-base balance, and nerve and muscle function.
Regulation of Body Water Compartments
Body water distribution is regulated by various mechanisms, including hormones like aldosterone and antidiuretic hormone (ADH). These hormones help maintain homeostasis by controlling renal water reabsorption.
Metabolism
Water and electrolytes play a significant role in metabolism. They are involved in digestion, nutrient transport, thermoregulation, and the elimination of waste products.
Impact of Pathological Conditions
Pathological conditions such as dehydration, kidney disease, and heart failure can disrupt body water and electrolyte balance, leading to serious health complications. Monitoring fluid and electrolyte status is crucial in clinical settings.
