Nutrition and Protein Quiz

Proteins

• Proteins are complex organic molecules composed of carbon, hydrogen, and oxygen. They also contain nitrogen.
• Specific types of proteins include structural proteins (collagen and keratin), contractile proteins (actin and myosin), blood clotting proteins (thrombin and fibrinogen), transport proteins (hemoglobin and transferrin), and regulatory proteins (hormones and enzymes).
• The body uses proteins to create new cells and cell components. Proteins also make up structures like hair and nails, are used as enzymes, lubricants, clotting compounds, antibodies and certain hormones and neurotransmitters. In smaller amounts, protein can be used as an energy source.
• Proteins act as buffers, which maintain acid-base balance in body fluids. The ideal pH level for blood and tissue fluid is between 7.35 and 7.45.

Learning Outcomes

• Learning outcomes describe the various aspects of protein in the human body, covering topics such as protein function, classification of amino acids, high-quality vs. low-quality proteins, digestion and absorption, and nitrogen balance.
• A list of protein functions in the body was presented
• An explanation of how to classify amino acids (essential or nonessential)
• A description of high vs. low-quality proteins
• Foods rich in high-quality proteins were identified
• The process of protein digestion and absorption in the human digestive system was described
• The concept of nitrogen balance and conditions involving positive or negative nitrogen balance were explained

Amino Acids

• Proteins are made of smaller units called amino acids.
• Human proteins can have 20 different amino acids.
• Each amino acid is composed of an amino group (nitrogen-containing group), an R-group (which varies for each amino acid), and an acid group.

Classifying Amino Acids

• Essential amino acids cannot be made by the body and must be obtained from the diet. There are 9 essential amino acids.
• Nonessential amino acids can be made by the body. There are 11 nonessential amino acids.
• A list of essential and nonessential amino acids was presented. There also exist conditional amino acids.

Food Sources of Proteins

• No single food source provides all needed protein naturally
• Foods from animal sources generally have more protein per serving than foods from plants.
• Seeds, nuts, and legumes provide relatively more protein per serving than other plant foods.
• Legumes are plants that produce seed pods with a single row of seeds.

Protein Quality

• High-quality protein contains all nine essential amino acids in the quantities needed for protein deposition in tissues and children's growth. Most animal proteins are high quality.
• High-quality plant proteins include quinoa and processed soy.
• Low-quality protein lacks one or more essential amino acids. Most plant sources and gelatin (an animal connective tissue by-product) fit this description.
• Limiting amino acids are essential amino acids that are present in low quantities in a specific protein source. Two or more plant protein sources can be eaten together (complementary proteins), allowing the needed assortment of amino acids.

Protein Synthesis

• Cells assemble amino acids in specific sequences according to coded information from DNA.
• Amino acids connect to form proteins via peptide bonds. They are like beads on a string, with the sequence dictated by DNA.

DNA Directs Protein Synthesis

• Protein synthesis starts when a section of DNA, which is called a gene, undergoes transcription. The gene's amino acid sequence is copied into messenger RNA (mRNA).
• mRNA moves the information concerning amino acid sequence from the nucleus to ribosomes, which are protein manufacturing sites in the cytoplasm.
• In the translation process, ribosomes read mRNA, indicating which amino acid to add to the protein chain and the correct order.
• tRNA molecules deliver specific amino acids for each site in the polypeptide chain.

Protein Denaturation

• Denaturation alters a protein's shape and function by exposing the protein to certain conditions like heat, acid, or agitation/mixing.
• Examples include heating raw eggs, acidic lemon juice curdling milk protein, and agitating egg whites.

Protein Digestion

• Chemical digestion of protein starts in the stomach with hydrochloric acid denaturing proteins.
• The enzyme pepsin breaks down proteins into smaller polypeptides.
• Protein digestion continues in the small intestine where pancreatic enzymes further break down polypeptides into shorter peptides and individual amino acids.

Protein Absorption

• Absorption of protein occurs in the small intestine.
• Absorptive cells release enzymes to break down peptides into amino acids.
• Individual amino acids, and some di- and tripeptides, enter absorptive cells where they are completely digested to single amino acids. These then travel to the liver via the hepatic portal vein.

Summary: Protein Digestion and Absorption

• Protein digestion begins in the stomach and continues through the small intestine where various enzymes further break down proteins.
• The final products of protein digestion—individual amino acids—are absorbed in the small intestine and transported to the liver for various cell functions.

Protein in the Human Body

• About 40% of human body mass is skeletal muscle.
• Collagen is the most abundant protein (25-35%).
• There is no protein storage site in the body, unlike glucose or fat.
• Regularly consuming protein is important to ensure adequate intake or amino acids needed for replenishment.
• Urea is the primary method for removing excess nitrogen from the body.

Protein Turnover

• Protein turnover breaks down old or unneeded proteins and recycles their amino acid components for new uses in the body.
• Amino acid pools are sources of amino acids for protein synthesis.

Deamination and Transamination

• Deamination removes a nitrogen-containing group from an amino acid.
• Transamination transfers a nitrogen group from one amino acid to a carbon skeleton to form a new amino acid.

Ammonia and Urea Formation

• Deamination creates ammonia, which is toxic to the body.
• Ammonia is converted into urea in the liver and excreted in urine by the kidneys.

Nitrogen Balance

• Positive nitrogen balance occurs when the body retains more nitrogen than it loses, common with growth, pregnancy, and recovery from illness.
• Negative nitrogen balance means the body is losing more nitrogen than it retains, which can result from inadequate protein intake, certain diseases, conditions or injuries.
• Healthy adults generally are in nitrogen equilibrium.

How Much Protein Do You Need?

• Estimated Average Requirement (EAR) for protein in healthy adults is 0.66 g/kg body weight.
• Recommended Dietary Allowance (RDA) for protein in healthy adults is 0.8 g/kg body weight.
• Protein needs increase in growth stages due to development and tissue building, as well as during pregnancy, lactation, and recovery from illness or injury.

Meat Consumption and Health

• High intake of red or processed meats may increase heart disease risk and certain cancers.
• Processed meats tend to be higher in saturated fat and sodium.

Recommendations for Protein Intake

• Choose lean or low-fat cuts of meat and poultry.
• Trim excess visible fat from meats
• Limit processed meats.
• Increase intake of fish and protein-rich plant-based protein sources (legumes, nuts and seeds).

Vegetarian Diets

• Vegetarian diets vary in their inclusion of animal foods,
• Common types include semi-vegetarian, lacto-ovovegetarian, lactovegetarian, ovovegetarian, vegan, fruitarian, and macrobiotic.
• Vegetarian diets are often high in fiber, vitamins, and certain minerals but can have limitations in certain vitamins and minerals (vitamin B12, iron) if dietary variety and supplementation are not carefully considered.

Concerns for Vegetarians

• Vegetarian diets can be challenging for children, pregnant women, and breastfeeding women to ensure they have adequate protein and/or vitamin B12.

Excess Protein Intake

• Excessive red or processed meat intake is associated with a higher risk of heart disease and certain cancers of the colon/rectum.
• Excess protein can lead to higher-than-normal urinary calcium losses, dehydration, and potential gout, especially in individuals predisposed to developing gout.
• Protein-rich foods are high in purines, which form uric acid. High uric acid can contribute to kidney stones.

Protein Deficiency

• Protein deficiency is rare but can occur in elderly adults and low-income populations as well as individuals with alcoholism, anorexia nervosa, or intestinal tract disorders.
• Protein-energy malnutrition (PEM), a severe form of protein deficiency, results when intake is low in energy and high-quality protein.
• PEM can result in Kwashiorkor and Marasmic kwashiorkor, which have different symptoms of deficiency.

What Is a Food Allergy?

• An allergy occurs when the body's immune system inappropriately responds to a typically harmless substance, which is an allergen.
• Most food allergens are proteins that escape digestion and are absorbed as whole proteins, triggering an allergic response.

Signs/Symptoms of Food Allergy

• Common signs and symptoms of food allergies include hives, swollen lips, skin flushing, scaly skin rash, difficulty swallowing, wheezing, and abdominal pain.
• A severe/life-threatening reaction is called anaphylaxis.

Common Food Allergens

• Common food allergens include cow's milk, eggs, peanuts, tree nuts, wheat, soy, fish, and shellfish.
• Non-protein allergens include food dyes and naturally present or added sulfites.

Celiac Disease

• Celiac disease is a condition wherein your immune system attacks tissues when exposed to gluten. This reaction often damages the small intestine, hindering the absorption of nutrients.
• Symptoms of celiac disease include diarrhea, abdominal pain, and bloating.
• Gluten is present in wheat, barley, and rye.

What Is PKU?

• Phenylketonuria (PKU) is a rare genetic disorder present at birth.
• It is caused by a lack of enzyme needed to convert the essential amino acid phenylalanine into another substance.
• Untreated PKU results in a buildup of phenylalanine and its by-products in the bloodstream, which can be dangerous and cause damage to tissues. Simple blood tests detect PKU.
• Treatment involves a special dietary regimen restricting phenylalanine intake.

Diet for PKU

• Infants wit PKU need a phenylalanine-free formula and low phenylalanine foods. Foods to avoid include nuts, milk, and milk products, eggs, meat, and animal products. These have naturally high levels. Some food additives to avoid include aspartame

Test your knowledge on essential nutrition concepts including protein quality, food allergies, and amino acids. This quiz covers various topics such as nutritional deficiencies, sources of protein, and the characteristics of amino acids. Challenge yourself to see how well you understand these fundamental nutritional principles.