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Questions and Answers
What are the basic units that proteins are synthesized from?
What are the basic units that proteins are synthesized from?
Amino acids
Which of the following is NOT an essential amino acid?
Which of the following is NOT an essential amino acid?
Incomplete proteins can support growth and maintain life.
Incomplete proteins can support growth and maintain life.
False
What is the name of the protein considered to be a reference protein with the highest biological value?
What is the name of the protein considered to be a reference protein with the highest biological value?
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Plant proteins are generally considered to be of higher quality than animal proteins.
Plant proteins are generally considered to be of higher quality than animal proteins.
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What is the supplementary effect in the context of nutrition?
What is the supplementary effect in the context of nutrition?
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What two conditions are often seen in developing counties due to deficiencies in protein and energy?
What two conditions are often seen in developing counties due to deficiencies in protein and energy?
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Which of the following is a characteristic of Kwashiorkor?
Which of the following is a characteristic of Kwashiorkor?
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Which of the following conditions is caused by inadequate energy intake in all forms, including protein?
Which of the following conditions is caused by inadequate energy intake in all forms, including protein?
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What are the main symptoms of protein energy malnutrition (PEM)?
What are the main symptoms of protein energy malnutrition (PEM)?
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What are the two main effects of undernutrition on tissue mass and function?
What are the two main effects of undernutrition on tissue mass and function?
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Malnutrition can lead to a decrease in the proliferation rate of intestinal mucosal epithelial cells.
Malnutrition can lead to a decrease in the proliferation rate of intestinal mucosal epithelial cells.
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What are the main effects of chronic undernutrition on the heart?
What are the main effects of chronic undernutrition on the heart?
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Undernutrition can impair the function of respiratory muscles, decreasing vital capacity and tidal volume.
Undernutrition can impair the function of respiratory muscles, decreasing vital capacity and tidal volume.
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The kidneys are relatively well-preserved during malnutrition as long as adequate water intake is maintained.
The kidneys are relatively well-preserved during malnutrition as long as adequate water intake is maintained.
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What is the effect of severe malnutrition on the immune system?
What is the effect of severe malnutrition on the immune system?
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Plasma insulin concentration is usually increased in individuals with severe malnutrition.
Plasma insulin concentration is usually increased in individuals with severe malnutrition.
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High protein diets, especially those rich in red meat, are associated with an increased risk for cardiovascular disease.
High protein diets, especially those rich in red meat, are associated with an increased risk for cardiovascular disease.
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Protein is essential for maintaining ______ integrity and function, and for health and reproduction.
Protein is essential for maintaining ______ integrity and function, and for health and reproduction.
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What specific element differentiates proteins from carbohydrates and fats?
What specific element differentiates proteins from carbohydrates and fats?
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Study Notes
Protein Structure and Function
- Proteins are the building blocks of various tissues in the body, such as muscle, blood, bone, skin, and hair.
- Many hormones and enzymes are either proteins or protein derivatives.
- Nucleic acids within cells combine with proteins to form nucleoproteins.
- Protein is essential for maintaining cellular integrity, function, health, and reproduction.
Protein Composition
- Proteins contain carbon, hydrogen, oxygen, and nitrogen.
- Proteins differ from carbohydrates and fats due to the presence of nitrogen.
- Proteins are composed of amino acids.
- Protein molecules can contain hundreds of amino acids.
- Chemically, amino acids consist of a carbon atom bonded to a carboxyl group, a hydrogen atom, an amino group, and an amino acid radical (R group).
Essential and Non-essential Amino Acids
- An essential amino acid cannot be synthesized by the body and must be obtained from the diet.
- Essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
- Non-essential amino acids can be synthesized by the body.
- Non-essential amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
Complete, Partially Complete, and Incomplete Proteins
- Complete proteins contain all essential amino acids in proportions that meet human needs for growth and maintenance.
- Examples of complete proteins include those derived from animal foods.
- Partially complete proteins contain sufficient amounts of amino acids for maintaining life but fall short of promoting growth.
- Gliadin in wheat is an example of a partially complete protein.
- Incomplete proteins lack one or more essential amino acids and cannot support growth or tissue building.
- Examples of incomplete proteins include protein found in wheat germ.
Protein Quality and Biological Value
- Egg protein is considered a complete protein with the highest biological value.
- The quality of other proteins is assessed by comparing their biological value to that of egg protein.
- Animal proteins (milk, meat, and fish) generally have high essential amino acid composition compared to plant proteins.
- Plant proteins (pulses, cereals, oilseeds) often have imbalances in essential amino acid composition.
Protein Digestion and Absorption
- Proteins in the diet are digested into amino acids in the stomach and small intestine.
- Gastric juice contains enzymes such as pepsin, which hydrolyzes proteins into polypeptides.
- Pancreatic and intestinal juices contain proteolytic enzymes (trypsin, chymotrypsin, elastase).
- These proteolytic enzymes break down polypeptides into smaller polypeptides.
- Peptidase enzymes further break down smaller polypeptides into free amino acids.
- Free amino acids are absorbed by active transport into intestinal cells.
- Some whole proteins may be absorbed by pinocytosis.
- Absorbed amino acids pass into the portal blood and liver, where conversion to proteins occurs.
Amino Acid Recycling
- All cells continually break down proteins and build new ones to maintain protein turnover.
- The body uses amino acids from protein breakdown and dietary protein to build proteins, other biological molecules (DNA, RNA), and produce energy.
Protein Requirements and Sources
- The safe daily intake of protein for adults is 1 g per kg of body weight.
- Pregnant and lactating individuals require higher protein intakes.
- Children's protein requirements depend on weight gain and growth.
- Animal-based foods (meat, fish, milk, egg) are rich sources of complete proteins.
- Plant-based foods (pulses, cereals, nuts, seeds) are useful protein sources but often less complete than animal products.
- Combining plant-based proteins (e.g., cereals and pulses) creates a more balanced amino acid profile.
Protein Deficiency
- Protein-energy malnutrition (PEM) frequently affects developing countries.
- PEM is commonly seen in young children in poverty.
- The two forms of PEM are kwashiorkor and marasmus.
- Kwashiorkor occurs due to a deficiency in protein intake with adequate energy intake.
- Marasmus is due to prolonged energy restriction, affecting both protein and energy intake.
Symptoms of Protein Deficiency
- Clinical symptoms of PEM include failure to grow, thinning/weakening/wasting of muscles, behavioral changes (irritability/apathy), edema, skin changes, hair changes, loss of appetite, vomiting, dehydration, liver enlargement, anemia, and increased susceptibility to infections and fever.
Protein and Body Composition
- Undernutrition can lead to loss of muscle mass and fat.
- Chronic undernutrition can negatively affect cardiac function, respiratory function, renal function, and the immune system.
High Protein Diet
- Diets high in animal protein sources, especially red meat, have a possible increased risk for kidney stones, kidney disease, liver malfunction, colorectal cancer, and osteoporosis.
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Description
Explore the vital roles and composition of proteins in the body, including their building blocks, amino acids, and the distinction between essential and non-essential amino acids. This quiz assesses your understanding of how proteins contribute to cellular integrity and health.
