Nutrition: Proteins, Fats, Hydration, Vitamins, and Minerals

Comprehensive practice flashcards detailing protein structure, quality metrics, and malnutrition syndromes; lipid classifications and cardiovascular risk targets; dehydration stages and fluid-electrolyte dynamics; and water-soluble/fat-soluble vitamin and mineral metabolic functions and clinical pathologies.

Why are proteins chemically unique compared to the other energy-yielding nutrients, carbohydrates and lipids?

Proteins contain nitrogen in addition to carbon, hydrogen, and oxygen. The term "amino" means nitrogen-containing, which gives the building blocks their name: amino acids.

How do essential, nonessential, and conditionally essential amino acids differ?

Nonessential amino acids can be synthesized by the body (specifically the liver). Essential amino acids cannot be synthesized and must be consumed through the diet. Conditionally essential amino acids occur when dietary intake of an essential amino acid is insufficient to produce its corresponding nonessential amino acid.

How are peptide chains classified based on their number of amino acid molecules?

Two joined amino acids form a dipeptide, three form a tripeptide, chains between $4$ and $20$ form an oligopeptide, and chains containing more than $20$ form a polypeptide.

What defines a complete protein, and which food sources typically provide them?

A complete protein contains all of the essential amino acids (it does not have to contain all nonessential amino acids). Animal-derived foods generally provide complete proteins, whereas plant sources (such as legumes) usually lack one or more essential amino acids.

What is protein denaturation, and what agents cause this irreversible change?

Denaturation is the irreversible loss of a protein's ability to function when exposed to heat or acid, such as during cooking or upon contact with hydrochloric acid in the stomach.

What distinguishes a positive nitrogen status from a negative nitrogen status in the human body?

A positive nitrogen status exists when the body creates more protein than it destroys, whereas a negative nitrogen status occurs when the body destroys more protein than it creates.

What are the daily dietary protein requirements for sedentary/lightly active individuals, endurance athletes, and strength-training athletes?

Individuals with light activity require $0.8\,\text{g/kg}$ of body weight. Endurance athletes need between $1.2\,\text{g/kg}$ and $1.4\,\text{g/kg}$. Athletes engaging in strength training require between $1.4\,\text{g/kg}$ and $1.8\,\text{g/kg}$.

Which food protein is used as the standard reference protein with a quality score assigned at $100$?

Egg protein, because it is one of the most complete and highly digestible proteins available.

What does Net Protein Utilization (NPU) measure, and what does a higher value signify?

Net protein utilization measures how efficiently a protein is utilized by the body based on the retention of consumed food nitrogen. The more nitrogen retained, the higher the quality of the protein.

Which protein quality measurement method is specifically used for infant formulas and baby food?

The Protein Efficiency Ratio (PER), which evaluates the weight gain of a growing animal compared to its protein intake.

What are the key clinical differences between Marasmus and Kwashiorkor?

Marasmus results from chronic deprivation of both energy and protein (common in infants aged $6\text{--}18\,\text{months}$) causing severe muscle wasting, absent body fat, and hypothermia. Kwashiorkor results from sudden, acute protein deprivation (typically in children aged $18\,\text{months}\text{--}2\,\text{years}$) characterized by facial/limb edema and a bulging belly from a fatty liver.

Which gastrointestinal infection commonly develops in children with severe protein-energy malnutrition due to lack of protective antibodies?

Dysentery, an infection of the gastrointestinal tract that causes severe diarrhea and can precipitate fatal heart failure.

How does excessive dietary protein consumption negatively affect mineral balance and renal workload?

High protein intake increases urinary calcium excretion (potentially compromising bone health) and places excessive demand on the kidneys, which must clear and excrete the byproducts of protein metabolism.

What structural feature chemically differentiates saturated, monounsaturated, and polyunsaturated fatty acids?

Saturated fatty acids contain only single bonds with every carbon bonded to two hydrogen atoms. Monounsaturated fatty acids have one carbon-carbon double bond (missing two hydrogens). Polyunsaturated fatty acids contain more than one double bond (missing four or more hydrogens).

How is the numerical designation of an Omega-3, Omega-6, or Omega-9 fatty acid determined?

By the position of the very first carbon-carbon double bond relative to the methyl end of the carbon chain (e.g., after the 3rd carbon for Omega-3, 6th for Omega-6, and 9th for Omega-9).

What occurs chemically during the commercial hydrogenation of unsaturated fats, and what harmful byproduct forms?

Hydrogen gas is bubbled into unsaturated oil to break unstable double bonds and attach hydrogen atoms, converting liquid oils into solid fats and creating trans fatty acids that raise LDL and lower HDL.

What is the function of lipoprotein lipase (LPL) on the surface of adipose tissue cells?

Lipoprotein lipase captures circulating postprandial triglycerides from the blood and hydrolyzes them into fatty acids and monoglycerides so they can cross cell membranes for storage.

Why is lecithin able to act as an effective emulsifier in aqueous solutions?

It is an amphipathic phospholipid containing hydrophobic fatty acid tails that associate with fats and a hydrophilic phosphate-choline group that interacts with water.

What are the recommended clinical blood lipid target levels for LDL, HDL, total cholesterol, and triglycerides?

LDL should be less than $100\,\text{mg/dL}$, HDL should be greater than $60\,\text{mg/dL}$, total cholesterol should be less than $200\,\text{mg/dL}$, and triglycerides should be less than $150\,\text{mg/dL}$.

What proportion of the body's energy needs at rest is supplied by fat, and which enzyme mobilizes stored adipose triglycerides?

$60\%$ of resting energy is supplied by fat. Hormone-sensitive lipase mobilizes stored triglycerides by cleaving them into glycerol and free fatty acids for release into circulation.

How much energy can ketone bodies provide to brain and nerve cells during prolonged carbohydrate deprivation?

Ketone bodies cannot sustain life alone, but they can provide up to two-thirds ($\frac{2}{3}$) of the energy needed by the brain and nervous tissue.

How is total body water divided across the major body fluid compartments?

Approximately two-thirds ($\frac{2}{3}$) is intracellular fluid (located inside cells) and one-third ($\frac{1}{3}$) is interstitial fluid (located between cells).

What four clinical findings serve as the best indicators of a patient's hydration status?

Level of consciousness, capillary refill time, mucous membrane appearance, and tear production.

What physical assessment findings differentiate mild, moderate, and severe dehydration regarding capillary refill, skin turgor, and tears?

Mild: capillary refill $2\,\text{seconds}$, normal turgor, normal tears. Moderate: capillary refill $2\text{--}4\,\text{seconds}$, slow turgor, decreased tears. Severe: capillary refill greater than $4\,\text{seconds}$ with cool limbs, tenting skin turgor, and absent tears.

What is the fluid replacement rule of thumb based on body weight lost after physical exertion?

One pound ($1\,\text{lb}$) of body weight lost during activity represents approximately $2\,\text{cups}$ of fluid loss that must be consumed to restore hydration.

What is the obligatory minimum daily urine output required by the human body to clear metabolic waste products?

A minimum of $500\,\text{mL}$ per day.

Which major electrolytes are primarily extracellular, and which are primarily intracellular?

Sodium ($\text{Na}^+$) and chloride ($\text{Cl}^-$) are primarily extracellular solutes; potassium ($\text{K}^+$), magnesium ($\text{Mg}^{2+}$), phosphate ($\text{PO}_4^{3-}$), and sulfate ($\text{SO}_4^{2-}$) are primarily intracellular.

How do antidiuretic hormone (ADH) and aldosterone coordinate renal regulation of fluid and electrolyte status?

ADH controls total body water volume by stimulating water reabsorption. Aldosterone controls electrolyte balance by prompting renal sodium reabsorption and reciprocal potassium excretion.

What is the standard home formulation for oral rehydration therapy (ORT)?

$1\,\text{cup}$ of boiling water, $2\,\text{teaspoons}$ of sugar, and a pinch of salt.

What deficiency syndrome results from a lack of vitamin B1 (thiamin), and what are its symptoms?

Beriberi, which presents with muscle degeneration, anorexia, depression, irritability, tachycardia, peripheral edema, and heart failure.

What are the cardinal physical symptoms of a vitamin B2 (riboflavin) deficiency?

Glossitis (smooth/swollen tongue), dermatitis, itchy/burning eyes, and cheilosis (painful fissures and sores in the corners of the mouth and lips).

What disease is caused by niacin deficiency, and what are its manifestations?

Pellagra, characterized by dermal sores, severe diarrhea, anxiety, confusion, memory impairment, dizziness, and death if untreated.

Why is maternal periconceptional supplementation of folate (folic acid) essential?

Folate is required for DNA/RNA synthesis and rapid cell division; deficiency drastically elevates the risk of neural tube defects in the developing fetus.

What type of anemia is caused by a deficiency in vitamin B12 (cobalamin)?

Megaloblastic anemia, often accompanied by glossitis, fatigue, sore mouth, and neurological/myelin degradation.

Eating large quantities of raw egg whites can induce a deficiency of which B vitamin?

Biotin, because raw egg whites contain avidin, a protein that tightly binds biotin and prevents its intestinal absorption.

What fatal deficiency disease is caused by a lack of vitamin C, and what are its primary symptoms?

Scurvy, manifesting with impaired wound healing, bleeding gums, easy bruising, structural muscle/heart damage, hemorrhage, and psychological changes.

What duration of unprotected sun exposure is required for cutaneous vitamin D synthesis, and what sunscreen threshold halts it?

Approximately $10\text{--}15\,\text{minutes}$ of unprotected sunlight exposure is sufficient. The application of sunscreen with an SPF of $8$ or higher blocks the skin from producing vitamin D.

What skeletal pathologies occur in children and adults due to severe vitamin D deficiency?

Rickets develops in children (marked by bowed legs/arms and defective tooth development), and osteomalacia develops in adults (characterized by progressive softening of bone matrix).

What is the primary physiological function of vitamin K, and what lab value does deficiency prolong?

Vitamin K is required for hepatic synthesis of blood-clotting factors and protein synthesis. A deficiency leads to defective coagulation and an increased prothrombin time (PT).

What quantitative intake distinguishes a major mineral from a trace mineral?

Major minerals are present in large body stores and required in daily quantities greater than $100\,\text{mg/day}$. Trace minerals are needed in amounts less than $100\,\text{mg/day}$.

How are Chvostek's sign and Trousseau's sign elicited to evaluate hypocalcemic tetany?

Chvostek's sign is elicited by tapping the facial nerve anterior to the ear, triggering involuntary facial twitching. Trousseau's sign is elicited by inflating a sphygmomanometer cuff on the arm for $30\,\text{seconds}$, precipitating carpal spasm.

Why are extreme deviations in serum potassium (hypokalemia and hyperkalemia) life-threatening emergencies?

Potassium regulates cardiac electrical conduction and membrane potentials; both severe deficiency and excess cause lethal cardiac arrhythmias and cardiac arrest.

What specific rule of co-supplementation prevents trace mineral antagonism when taking zinc doses greater than $20\,\text{mg}$?

For every additional $10\,\text{mg}$ of zinc ingested above a $20\,\text{mg}$ baseline, an individual should add $1\,\text{mg}$ of copper and half as much manganese as zinc.

What conditions arise from severe iodine deficiency during adulthood and fetal development?

Adult deficiency produces goiter (compensatory enlargement of the thyroid gland). Gestational deficiency leads to congenital cretinism, resulting in severe physical and intellectual disability.

What irreversible dental condition is caused by excessive fluoride intake during tooth development?

Fluorosis, characterized by permanent brownish staining and structural pitting of the enamel surface.