Biochemistry Nutrition Final Review: Amino Acids, Macronutrients, and Metabolic Adaptations

What is the primary method of amino acid absorption in the body?

Most amino acid absorption occurs across enterocyte transport systems, primarily using Na+-dependent carriers.

What happens when a large dose of a single amino acid is consumed?

It can monopolize a shared transporter and impair the absorption of competing amino acids, leading to an amino acid imbalance.

What is the role of PEPT1 in amino acid absorption?

PEPT1 transports di- and tripeptides efficiently, allowing for faster absorption than free amino acids.

What is the general goal of Medical Nutrition Therapy (MNT) for amino acid disorders like PKU?

To maintain biochemical equilibrium while providing adequate nutrition for growth and supporting social/emotional development.

What enzyme is deficient in classic PKU?

Phenylalanine hydroxylase.

What is the first nutritional goal in managing PKU?

To restrict phenylalanine and supplement tyrosine.

What are the potential consequences of protein excess?

It can compromise carbohydrate utilization, contribute to dehydration, and increase the workload on the liver and kidneys.

What is the bottom line regarding protein excess according to Dr. Wilson?

Protein excess is not automatically toxic; the source and accompanying nutrients matter.

List some functions of proteins in health and disease.

Proteins contribute to structure, catalysis, movement, transport, communication, protection, fluid balance, and pH regulation.

What are the nine essential amino acids (EAAs)?

Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Leucine, Lysine.

What defines a complete protein?

A complete protein contains all essential amino acids in proportions that meet human needs.

What is the Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates?

45-65% of energy.

What is the AMDR for protein?

10-35% of energy.

What is the recommended daily allowance (RDA) for carbohydrates?

130 g/day based on average brain glucose utilization.

What is the protein intake recommendation for healthy individuals?

1.2-1.6 g/kg/day.

What dietary modification is recommended for type I diabetes?

Carbohydrate modification.

What is the classic ketogenic diet ratio of fat to combined protein and carbohydrate?

4:1 ratio.

What is the MNT protein recommendation for burn patients?

1.5-2 g/kg/day to support positive nitrogen balance.

What are some examples of clinical conditions where macronutrient distribution is modified?

Type I diabetes, obesity, epilepsy, hyperlipidemia, heart disease, and chronic pancreatitis.

What is the significance of complementary proteins?

Complementary proteins combine to provide adequate essential amino acids, such as legumes and grains.

What is the impact of excessive protein on exercise?

Excessive protein can reduce carbohydrate availability for activity.

What is the consequence of protein excess on hydration?

It can contribute to diuresis and dehydration.

What is the role of insulin in protein function?

Insulin acts as a signaling protein involved in communication within the body.

What are some examples of proteins involved in transport?

Membrane transport proteins and albumin.

What is the significance of amino acid composition in protein quality?

High-biological-value proteins contain essential amino acids in proportions that meet human needs.

What are the potential effects of maternal hyperphenylalaninemia?

It can damage the fetus and is associated with cardiac defects, stunted growth, microcephaly, and mental incapacities.

What is the importance of monitoring blood phenylalanine levels in PKU?

To maintain levels between 2-6 mg/dL (120-360 micromol/L) for optimal health.

What is the impact of protein source on health?

The source of protein matters; high-protein diets from red/processed meats may increase saturated fat and cholesterol intake.

What is the purpose of carbohydrate loading in endurance athletes?

To increase muscle glycogen stores and potentially improve performance.

What are the strategies for carbohydrate loading according to Wilson's lecture?

An exercise taper followed by a high-CHO diet with low-intensity activity or 1-2 days of inactivity with a high-CHO diet before an event.

What is the physiological consequence of a very low carbohydrate/high fat diet?

Increased fat utilization, increased ketone production, and development of ketosis.

How does ketosis affect seizure frequency in epilepsy?

It is associated with reduced seizure frequency in refractory epilepsy.

What happens to muscle glycogen stores during high carbohydrate intake?

Muscle glycogen stores rise, leading to increased carbohydrate availability for endurance activities.

What is the relationship between physical activity and insulin sensitivity?

Exercise increases insulin sensitivity, which opposes insulin resistance.

What are the three energy systems identified by Wilson?

Creatine phosphate, anaerobic glycolysis, and aerobic metabolism/oxidative phosphorylation.

What is the gold standard for measuring energy expenditure?

Indirect calorimetry.

What is the respiratory quotient (RQ) for carbohydrates?

1.00.

What is the RQ for fats?

0.70.

How does physical activity influence body composition?

It affects energy needs, nutrient requirements, and helps preserve lean muscle mass.

What is the effect of resistance/mechanical loading on muscle adaptation?

It provides a training stimulus that supports protein synthesis and muscle hypertrophy.

What is the impact of high-intensity activity on fuel utilization?

It leads to greater carbohydrate dependence.

What nutritional needs arise during severe metabolic stress, such as burns?

High total energy and high protein to support positive nitrogen balance.

What is the role of protein during exercise?

It supports tissue/protein synthesis but is not a preferred fuel source.

What is the impact of carbohydrate intake on endurance potential?

Increased muscle glycogen leads to delayed glycogen depletion and improved endurance potential.

What is the effect of exercise on LDL cholesterol levels?

Exercise tends to decrease LDL cholesterol.

What happens to glucose utilization in trained athletes?

They use glucose more sparingly and utilize fatty acids more efficiently.

What are the general Acceptable Macronutrient Distribution Ranges (AMDR) for carbohydrates?

45-65%.

What are the general AMDR for fats?

20-35%.

What are the general AMDR for proteins?

10-35%.

What does a high carbohydrate intake during pre-operative feeding achieve?

Decreased postoperative insulin resistance and inflammatory response.

What is the effect of physical activity on cardiovascular disease risk?

It reduces risk by lowering LDL cholesterol, blood pressure, and body weight.

How does dietary protein support muscle adaptation?

It provides amino acids necessary for protein synthesis during resistance training.

What is the relationship between weight loss and cardiovascular/metabolic risk factors?

Improvements often track with the amount of weight lost rather than a single macronutrient pattern.

What is the significance of the RQ values

They may indicate unusual metabolic conditions or errors in measurement.

What is the impact of exercise on heart strength?

Exercise increases heart strength and coronary artery size/tone.

What is the role of nutrients during physical activity?

They fuel contraction, build new tissue, and maintain fluid/electrolyte status.