Nutrition for Sports and Exercise: Carbohydrates, Proteins, and Lipids

Comprehensive practice flashcards covering carbohydrate, protein, and lipid digestion, transport, metabolism, and sports performance recommendations from Chapters 4, 5, and 6.

What are the three primary monosaccharides discussed in human nutrition, and how many carbon atoms does each molecule contain?

Glucose, galactose, and fructose; each is a $6\text{-carbon}$ ($6\,\text{C}$) molecule.

Identify the three monosaccharides shown in this chemical structure diagram from left to right:

D-glucose, D-galactose, and D-fructose.

What is the distinction between Glycemic Index (GI) and Glycemic Load (GL)?

Glycemic Index = how 1 single food item influences BS and insulin

Glycemic Load = how an entire meal or combination of foods impacts the BS and insulin response.

What are the constituent monosaccharide pairings that form sucrose, lactose, and maltose?

Sucrose consists of glucose + fructose, lactose consists of glucose + galactose, and maltose consists of glucose + glucose.

What polysaccharide serves as the only plant storage form of glucose, and what polysaccharide serves as the exclusive animal storage form?

Starch is the only plant storage form of glucose, while glycogen is the storage form of glucose found exclusively in animal products.

Which animal-sourced storage polysaccharide is represented by this branched chemical structure?

Glycogen.

At what rate does the stomach empty carbohydrates into the small intestine?

At a rate of $1\,\text{g/min}$ (or $60\,\text{g/hr}$).

Based on this absorption diagram, which apical transporters move glucose, galactose, and fructose into the intestinal epithelial cell, and which basolateral carrier transports them out?

SGLT transports glucose or galactose in alongside $\text{Na}^+$, GLUT-5 carries fructose in via facilitated diffusion, and GLUT-2 transports glucose, galactose, or fructose out into the interstitial fluid and capillary.

How is insulin resistance defined regarding hepatic glucose output?

The inability to stop the liver from making and putting out glucose.

In the 20 km cycling time trial study shown, which nutritional state resulted in a significant performance improvement when using a carbohydrate (CHO) mouth rinse compared to placebo?

The glycogen-depleted (DEP) state.

What are daily carb intake recs for athletes doing light-to-moderate, endurance/high-intensity, and ultraendurance training?

Light-to-moderate training: $3\text{ to }7\,\text{g/kg/day}$; Endurance/high-intensity training: $6\text{ to }10\,\text{g/kg/day}$; Ultraendurance training: $8\text{ to }12\,\text{g/kg/day}$.

What’s rec for carbs/hour consumed for untrained gut during exercise vs trained?

Untrained individuals = start $30\text{ to }60\,\text{g/hr}$, trained athletes = $60\text{ to }90\,\text{g/hr}$.

What specific carbohydrate mixture ratio is recommended when consuming more than $60\,\text{g/hr}$ during exercise to maximize uptake and avoid gastrointestinal distress?

A glucose:fructose mixture in a $2:1$ ratio.

Why is whey protein classified as a 'fast-acting' protein, and what is considered the best post-exercise cocktail?

Whey protein causes a rapid rise in blood levels of the amino acid leucine; the best post-exercise cocktail is whey combined with glucose.

What are the 9 indispensable (essential) amino acids that must be obtained directly from dietary sources?

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

Which two amino acids are completely ketogenic and cannot produce glucose?

Leucine and Lysine.

Which three amino acids are classified as branched-chain amino acids (BCAAs)?

Leucine, Isoleucine, and Valine.

Which two pancreatic proteolytic enzymes carry out the initial step of cleaving protein in the duodenum?

Trypsin and chymotrypsin.

How do deamination and transamination differ regarding their directionality and reaction mechanism?

Deamination is a permanent, one-direction, irreversible removal of an amino group forming an $\alpha\text{-keto acid}$; transamination is a reversible exchange involving two amino acids.

In deamination rxns, which enzyme and vitamin-containing cofactor convert threonine into $\alpha\text{-ketobutyrate}$ and ammonium ($\text{NH}_4^+$)?

Threonine dehydratase with pyridoxal phosphate (PLP)

What inter-organ cycle is depicted here, illustrating the transport of amino-nitrogen from muscle to the liver for gluconeogenesis during prolonged exercise?

The glucose-alanine cycle.

Glucose --> pyruvate + N => alanine. Alanine split into N and pyruvate in liver. Pyruvate --> glucose --> moved to muscle --> glucose --> 28-32 ATP in muscle

What physiological states do positive nitrogen balance ($\text{N} > 0$) and negative nitrogen balance ($\text{N} < 0$) represent?

$\text{N} > 0$ indicates an anabolic state supporting muscle growth; $\text{N} < 0$ indicates a catabolic state with net tissue protein loss.

What is the recommended daily protein intake range for athletes in training compared to the sedentary RDA of $0.8\,\text{g/kg/day}$?

$1.2\text{ to }2.0\,\text{g/kg/day}$.

How does beta-alanine supplementation boost performance during sprint exercise?

It increases muscle carnosine levels => buffers acid and helps maintain muscle pH in high-I exercise

How are fatty acids classified based on carbon chain length?

2-3 C = Short-chain, 5-10 C = medium-chain, and 12 and up = long-chain

What are the two essential fatty acids required by the human body, and what are their respective omega classifications?

Linoleic acid (omega-6) and alpha-linolenic acid (ALA, omega-3).

Eicosanoids from EPA and DHA vs Arachidonic Acid?

Eicosanoids made from EPA and DHA = anti-inflammatory and inhibit eicosanoids from arachidonic acid, which are pro-inflammatory.

By what circulatory compartment are medium- and short-chain fatty acids absorbed directly after SI abdorption?

Directly into the blood

Long-chain fatty acids are broken down into triglycerides and glycerol before being put into chylomicrons

What is the primary function of lipoprotein lipase in the bloodstream, and which hormone activates it?

It strips fatty acids from circulating chylomicrons to deliver them to adipose and muscle cells for use or storage; it is activated by insulin.

In the adipocyte lipolysis cascade shown, which enzyme breaks down stored triglycerides into glycerol and fatty acids, and what plasma protein carries free fatty acids (FFAs) through the capillary flow?

Hormone-sensitive lipase (HSL) breaks down stored triglycerides, and albumin (Alb) binds and carries the free fatty acids.

Identify the carrier compound and the enzymes labeled I and II in this diagram that transport fatty acyl groups across the mitochondrial membranes:

L-carnitine carrier —> carnitine acyltransferase 1 forms O-acylcarnitine —> Carnitine acyltransferase 2 remakes acyl-CoA and free L-carnitine

Why does rate of fatty acid mitochondrial transport decline as exercise progresses?

Carnitine is used more heavily during exercise => less free carnitine available as the workout progresses => slows transport over time

What happens to the relative utilization of fats versus carbohydrates as exercise running pace and heart rate increase?

Carbohydrate use rises for fast energy while the percentage of energy derived from fat decreases.