Questions and Answers
What are the three fates of amino acids after entering intestinal cells?
Which condition is primarily characterized by severe protein deficiency and presents with edema?
How does a high-protein diet impact heart disease risk?
What is the recommended calcium-to-protein intake ratio for bone health?
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What is the primary reason a high protein intake may accelerate kidney deterioration?
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What is the protein RDA for adults based on body weight?
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What misconception do many athletes have regarding protein powders?
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Which protein-rich foods are suggested to lower the risk of some cancers?
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What is a common symptom of marasmus?
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Why may protein-rich diets contribute to an increase in calcium excretion?
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Study Notes
Overview of Protein
- Protein is essential in every living cell, including plants, animals, and microorganisms.
- The primary building blocks of proteins are amino acids and nitrogen, which result from protein digestion.
Amino Acids
- Amino acids are linked by peptide bonds to create various proteins.
- Classified into:
- Essential amino acids: cannot be synthesized by the body and must be obtained from the diet.
- Non-essential amino acids: can be synthesized by the body.
Types of Protein
- Simple Protein: yields only amino acids upon hydrolysis (e.g., albumins, globulins, enzymes).
- Complex Protein: includes non-protein groups (e.g., glycoproteins, phosphoproteins, lipoproteins, chromoproteins).
- Derived Protein: formed from the degeneration of primary and secondary protein forms (e.g., peptides).
Protein Sources
- Complete Protein: contains all nine essential amino acids; typically animal-based (e.g., meats, dairy).
- Partially Complete Protein: lacks sufficient essential amino acids for growth; some animal sources are included.
- Incomplete Protein: deficient in one or more essential amino acids and often plant-based (e.g., grains).
Protein Functions
- Tissue building: repairs and builds tissues.
- Energy source: can be utilized for energy.
- Plasma proteins: maintain osmotic balance (e.g., albumin).
- Defense system: produces antibodies for immune response.
Acid-Base Regulation
- Proteins help maintain acid-base balance by attracting hydrogen ions to buffer solutions.
- Normal pH range for blood and body fluids is between 7.35 and 7.45.
Transportation
- Proteins transport nutrients, oxygen (e.g., hemoglobin), and lipids throughout the body.
- Some proteins function as membrane transporters for vitamins and minerals.
Fluid Balance Regulation
- Plasma proteins usually do not cross blood vessel walls; however, during illness, they can leak and attract water, causing edema (swelling).
- Edema can arise from protein losses due to inflammation, inadequate protein synthesis, or insufficient protein intake.
Digestion and Absorption
- Digestion begins in the stomach and involves hydrolysis by HCL and proteolytic enzymes, breaking proteins into polypeptides.
- Amino acids are absorbed in the small intestine and can:
- Enter circulation for enzyme synthesis.
- Convert to different amino acids.
- Be oxidized for energy.
Protein Sources in Foods
- Notable protein sources include casein in milk, albumin in eggs, and gluten in wheat products.
Protein Deficiency
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Protein-energy malnutrition (PEM) includes:
- Kwashiorkor: severe protein deficiency characterized by edema, muscle loss, and brittle hair.
- Marasmus: severe energy and protein deficiency with symptoms like weakness and growth retardation.
Health Implications
- High-protein diets related to heart disease due to saturated fats in animal proteins.
- Red and processed meats linked to increased cancer risk.
- High protein intake can increase calcium excretion, impacting bone health (osteoporosis).
- Protein does not cause kidney disease, but excessive intake can strain kidneys and worsen chronic conditions.
Recommended Protein Intakes
- Protein should make up 10-35% of total energy intake.
- Recommended dietary allowance (RDA) for adults is 0.8 grams per kilogram of body weight.
Protein Supplements
- Protein powders are often misunderstood; muscle growth is primarily through exercise, not supplements.
- Most athletes may not require additional protein beyond normal dietary intake.
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Description
Explore the fundamental role of proteins in living cells with this quiz. Learn about amino acids, their classifications, and the significance of peptide bonds. Test your knowledge on the building blocks of life and their importance in biology.
