Applied Physiology I Exam #1

3 basic sources of fuel

Carbohydrates

• give off great energy but not great for much else

Lipids

• good for structural building, and biologically useful

Proteins

• tons of biological use

• wasting if using fuel, so would rather not burn this

Excess Storage

All 3 can be converted into forms for energy (ATP) production or converted into forms for storage

• all stored primarily as fat (evolutionarily advantageous)

• Fat is worth more energy, don’t have to store water with it

Carbohydrate Types

Monosaccharides (single molecules)

• Glucose (what we mainly eat)

• Galactose

• Fructose

Can only absorb a monosaccharide

Disaccharides (links of two simple sugars)

• Maltose (glu + glu)

• Lactose (glu + gal), milk sugar

• Sucrose (glu + fru), table sugar

Polysaccharides (Links of many 3+)

• Starches (only alpha links)

• Fiber (incl. cellulose), beta links cannot break these bonds, pulls in water and loosens stools

• Glycogen (only alpha links, break down for processing)

Carbohydrate Conversion Terms

Glycolysis (glucose to pyruvate)

• the metabolic process that breaks down one molecule of glucose into two molecules of pyruvate while capturing usable energy

Gluconeogenesis (pyruvate to glucose)

• Gluconeogenesis is the metabolic process of building new glucose from non-carbohydrate sources, using pyruvate as its central entry point and primary building block

Glycogenolysis (glycogen to glucose)

• the metabolic process of breaking down stored glycogen into glucose to maintain blood sugar levels and provide immediate cellular energy

Glycogenesis (glucose to glycogen)

• the metabolic process of building glycogen by chaining glucose molecules together for storage

Glycogen Storage

Glucose is a monosaccharide + add more glucose = Glycogen

Glycogen is the stored version of glucose, molecules packed together for quick storage

• Liver Storage: Holds about 100 grams, used to maintain blood sugar levels for the entire body. SHARES

• Muscle Storage: Holds about 400 grams, used exclusively to power local muscle contractions. KEEPS

Role of Carbohydrates

Serve as primary movement fuel

Recommended Intake

• 40 to 60% of daily calories

• Active needs more carbs, and higher intensity

Body’s Primary Energy Source

• Only source for neurons and RBCs

Sufficient Glucose/Glycogen Stores:

• spare muscle protein (don’t use protein as a fuel source)

• Prevent ketoacidosis (incomplete fat breakdown) Carbohydrate intake prevents ketoacidosis by triggering the release of insulin, which stops the liver from breaking down fats into dangerous amounts of acidic ketones

Muscle and Liver Glycogen Stores

Crucial for energy during high intensity aerobic activity

• Liver stores about 55% depleted after 1 hour, almost complete at 2 hours

Carbohydrates and Exercise Kinetics

Transition to Exercise (first 5 - 10 mins)

• almost exclusively muscle glycogen

• some plasma glucose

First 20-30 mins

• about 50% liver and muscle glycogen (remainder mostly fat catabolism) (rate dependent)

Performance declines significantly when glycogen stores are depleted

• Fat may have more cal/g but rate of oxidation is much slower

• Therefore, glycogen stores are critical to maintain high performance over longer periods

Lipids (aka Fats)

98% for dietary lipids are triacylglycerols

• three fatty acid chains linked to a glycerol

• more biologically valuable than carbs, but lipids are hydrophobic and do not require a lot of water to go with it

Saturated Fats

• Single Bonds Only: The carbon backbone contains only single covalent bonds (C–C) with absolutely no carbon-to-carbon double bonds (C=C).

• Densely Packed: The straight, linear shape of the hydrocarbon chains allows the molecules to align closely and stack tightly against one another.

• Solid at Room Temperature: Due to this dense molecular packing, they have higher melting points and remain solid at room temperature.

Unsaturated Fats

• C=C Double Bonds: The carbon backbone is not fully saturated with hydrogen atoms, creating at least one double bond.

• The Molecular Kink: In nature, these double bonds usually create a structural bend or "kink" in the hydrocarbon chain.

• Less Densely Packed: Because of the kink, the molecules cannot stack tightly or align closely against one another.

• Liquid at Room Temperature: This loose molecular packing gives them a lower melting point, keeping them in liquid form (oils) at room temperature.

Biological Unsaturated Fats (Cis Configuration)

• The Structure: The hydrogen atoms sit on the same side of the double bond. This asymmetry creates the characteristic molecular kink.

• The Sources: Found abundantly in nature. Examples include olive oil, avocados, nuts, seeds, and fatty fish (like salmon).

• Health Impact: Considered highly beneficial. They lower harmful LDL cholesterol, raise beneficial HDL cholesterol, and reduce the risk of cardiovascular disease.

Trans Unsaturated Fats (Trans Configuration)

• The Structure: The hydrogen atoms sit on opposite sides of the double bond. This straightens out the chain, mimicking a saturated fat. Because it lacks a kink, trans fats can pack densely and are often solid at room temperature.

• The Sources: A tiny amount occurs naturally in dairy and meat from ruminant animals. However, the vast majority are industrial byproducts formed through partial hydrogenation—a chemical process that turns liquid vegetable oil into solid shortening (like margarine or commercial frying fats).

• Health Impact: Extremely hazardous to cardiovascular health. They aggressively raise harmful LDL cholesterol while simultaneously lowering beneficial HDL cholesterol, triggering systemic inflammation.

Fun Fat Facts

Fatty acid absorption depends on the length

< 12 carbon… unmodified uptake by GI

> 12 carbons require bile salts, uptake by lymphatics, transport to adipose for fat storge

Essential Fats

• Fats we cant manufacture ourselves

• Several polyunsaturated fats i.e. linoleic acid, Omega-3s

Trans Fats (synthetic usually harder to metabolize)

• Unsaturated fats with hydrogens on the opposite sides of double bond (same side are cis)

Lipogenesis vs. Lipolysis

Lipogenesis is the anabolic process of building and storing fat by synthesizing triglycerides from glucose or other precursors.

Lipolysis is the catabolic process of breaking down stored triglycerides into free fatty acids and glycerol to release energy.

Together, these opposite pathways manage the body's fat balance and energy reserves.

Fat in the Diet

In a nutshell: most Americans eat too much

• Try to reduce saturated fats to <10% total calories (about 200-300 cal)

• Omega-3 and 6 unsaturated fats (last C=C is 3 carbons from the end) actually seem to benefit the lipid profile, and overall health, high levels in certain fish, shellfish, and sea mammals

Other Lipids

Packaging material, contains things

Phospholipids (cell membranes), attached phosphate group and 2 fatty acids (amphipathic- both hydrophilic and hydrophobic)

Lipoproteins (lipids (softer)+ proteins (dense)) 3 types

1. Chylomicrons absorbed from GI

• mostly emulsified fats (LCFA, TAG, PL, and Vit ADEK)

2. HDL (>50% protein)

• high density, more protein less lipid

• good cardiac, chol sponge and delivers back to liver

3. LDL (<20% protein)

• >80% chol + fat, low density, more lipid less protein

• Bad chol and bad cardiac

• Cant take up lipid, deposits chol

HDLs seem to help remove unnecessary cholesterol from tissues… higher levels positive for CV health

Body Fat Stores

Someone with average body fat stores around 108,000 calories at a time

• This can last a person for about 54 days

Fat is essentially water free, light weight fuel

• stored fat can maintain activity >75x stored glycogen (and this is for an individual with normal body fat)

• Protects vital organs

• Insulation

• “Carries” Vits A,D,E,K (can overdose on these fat soluble vitamins, D is main culprit)

• Spares muscle proteins and suppresses hunger (leptin), obesity can mean that someone is leptin deficient

Fat and Exercise

Respiratory Quotient = which fuel is being used

• RQ of about 1 = cho

• RQ of about 0.7 = fat

Fat provides 30-80% of energy for physical activity; depends on nutrition, intensity, and duration

• When glycogen stores are full you burn carbs, as they deplete, you rely on fat and slow down

Fat contribution to exercise is dependent on:

• Glycogen stores: diet

• Duration: depletion of glycogen stores (1 or 2 hrs enough glycogen)

• Intensity: faster and harder means more carbs

• Training: make more mitochondria in cells to make ATP faster

Protein

Don’t want to use protein for energy

• chains of amino acids

• quite anabolic (helps build stuff) but too valuable to be used for energy

• 20 different amino acids used in human protein codes

• 8 essential AAs (9-10 in kids) REQUIRED IN DIET, eggs

• Non-essential means that we can make our own from carbon sources

Despite the ability to synthesize many, animals tend to consume most of their protein from eating other animals

Amino Acids

Amino Group: A nitrogen atom bonded to two hydrogen atoms (-NH₂).

Carboxyl Group: A carbon atom double-bonded to oxygen and single-bonded to a hydroxyl group (-COOH). This is the acidic part.

Hydrogen Atom: A single hydrogen atom (-H).

Side Chain (R-Group): This is the unique "X-factor" chemical group. It is different for every amino acid and determines its specific properties (like size, charge, and whether it likes water).

To use amino acids for energy, your body must first remove the nitrogen group through deamination:

• Nitrogen Waste: The liver strips the toxic nitrogen (-NH₂) and turns it into ammonia, then urea, which you pee out.

• Carbon Fuel: The remaining carbon skeleton is converted into glucose or acetyl-CoA.

• Energy Output: This fuel enters the Krebs cycle to create ATP (energy).

Complete vs. Incomplete Proteins

Number of essential amino acids and balance

Protein sources are “rated” 0-100 based on quality

• Complete proteins: all essential amino acids and balanced in amino acids

• Eggs=100, Beef=69, Potatoes=34

Vegan and vegetarian diets are possibility, but correct foods must be chosen carefully to avoid protein malnutrition (even if total protein is high)

Excess Protein

Does not give you big muscles

• transaminated and used for energy

• excess stored as fat

Step 1: Excess intake. You eat more protein than your body needs for muscle repair and daily function.

Step 2: Nitrogen stripping. Because your body cannot store extra protein, it strips the nitrogen-rich amino groups off the leftover amino acids.

Step 3: Ammonia creation. This freed nitrogen immediately turns into highly toxic ammonia.

Step 4: Liver conversion. Your liver quickly intercepts the toxic ammonia and processes it into a safe, non-toxic compound called urea.

Step 5: Kidney excretion. The liver releases urea into your blood, where your kidneys filter it out and flush it from your body through urine.

Protein and Exercise

Negative Protein Balance during exercise (worse is CHO or FFA deficit)

Positive protein balance during recovery

• build protein balance

• keep nitrogen higher than what you lost

Consuming more nitrogen (via dietary protein) than you lose (via sweat, urine, and urea) ensures your body has the structural surplus required to build new muscle tissue during rest.

Alanine Glucose Cycle- Turning Protein to Glucose for Fuel

• 10-15% of total exercise energy requirement

• Long periods of exercise (hours) alanine derived glucose about 50% of hepatic glucose output

• Increases with exercise training to stabilize blood glucose during prolonged activity

In the muscle: When you exercise for hours, your muscles break down a little protein and use the amino acid alanine.

In the blood: Muscles release alanine into your bloodstream. It travels to your liver.

In the liver: Your liver turns alanine into glucose (blood sugar).

Back to the muscle: The liver sends this new glucose back through the blood to your muscles to give you energy.

Vitamins, Minerals, and Water

Vitamins are ESSENTIAL

• It cannot be made, you must eat it (except for vitamin D)

These are all important things that you must ingest

Key Vitamin Roles in Metbolism

Vitamins are not useful for energy

They are Cofactors:

• help energy pathways by speeding up or mediating chemical reactions

Increased metabolism generates free radicals (increased aerobic exercise = more free radicals)

• Lonely electrons, known as free radicals, can damage the DNA

• vitamins are antioxidants and can scavenge free radicals (A,C,E)

Vitamins and Exercise

Fat Soluble Vitamins

• A,D,E,K

• excess amounts are stored and can become toxic

Water Soluble Vitamins

• B’s & C

• can ingest all that you want, excess will come out in urine

In general, vitamins participate repeatedly in chemical reactions, therefore individuals who exercise do not need increased demand

Does exercise increase damage?

Sure, it stresses the body

• but, the more you exercise the more the body build up defenses and the benefits outweigh the risks

Do vitamin supplements help?

A bit controversial, but probably no more that from a balanced diet

• they contain no useful energy

• serve as links and regulators of metabolic reactions

• control tissue syn and repair, integrity of PM

"Syn" is short for synthesis (making or building something)

"PM" stands for Plasma Membrane, which is the outer wall or "skin" protecting every single cell in your body

Although the excess does you no good, dietary supplement sales continue to go up

Key Vitamins

B9 is important in early cellular division

• folic acid, reduces spina bifida risk

• pregnant women should increase folic acid intake, cant take too much

B12

• Important for energy reactions and RBC synthesis

Vitamin C

• in fruits and vegetables, good for antioxidant reactions

How much do i need?

Recommended Dietary Allowance (RDA)

• recommended amount that is more than enough for the average person (only 3% of people will need more than this)

Estimated Average Requirements (EAR)

• how much a normal person needs

Adequate Intake (AI)

• how much is good enough

Tolerable Upper Intake Level (UL)

• how much before it becomes toxic

Minerals

Good for cell osmolarity and communication

Osmolarity: Sodium and potassium balance water inside and outside your cells to keep them stable.

Signaling: These same minerals act as electrolytes, creating electrical charges that let your brain and nerves talk to your muscles.

• chemists just call them elements

• several play key roles as rats of enzymes, proteins, hormones, and vitamins

Two classifications:

• Major (7) >100 mg/day

• Trace (14) <100 mg/day

Role of Minerals in Metabolic Pathways

Key for:

• Bone structure and teeth (Ca and P) form hydroxyapatite

• Maintenance (Na, K, Ca)

• Regulation (co-enzyme roles; Fe, Zn, Mg, Ca)

Mineral Bioavailability

The body’s capacity to absorb and use food minerals varies and depends on four factors:

1. Type of food

2. Mineral-mineral interaction

3. Vitamin-mineral interaction

4. Fiber-mineral interaction

Also, hormones, age, and other co-factors are all important!

Sodium is easy to absorb

calcium need iron to better absorb

Doctors will tell patients about important considerations

Calcium

is important for structure

• maybe the body’s most abundant material (about 99% in bone)

• combines with phosphorus (phosphate) to make bones and teeth

Inadequate Calcium Intake

or low regulating hormone levels reduces bone mineral contact which promotes two conditions:

1. Osteopenia: weakened bone. increased fracture risk

2. Osteoporosis: bone loses its calcium mass and concentration, which causes bone to progressively become more porous and brittle with high likelihood of fracture

Bone Density Scores

• z-score: compared to others in your demographic

• t-score: compared to the best bone density (0 is good, if btwn -1 and -2.5 then penia, if even lower than porosis

Older, post menopausal women can struggle with bone density loss because of

1. calcium intake

2. hormones

3. bone stress, weight bearing

4. medications

The major hormone for calcium intake is VITAMIN D which helps absorb and deposit calcium into the bones

• the body can synthesis this from the sun

Bone

Weight bearing activities have the most positive impacts on bone density, but not all are created equally

• Runners= good legs bones, not so much arms

• Swimmers= not really better than the average person

• Weightlifters= better all around

Female Athlete Triad

Women who train intensely and emphasize weight loss often engage in disordered eating behaviors that link to menstrual irregularities

Progression:

1. Energy drain (burning more than they eat)

2. Amenorrhea (absence of menstruation)

3. Osteoporosis (caloric imbalance, calcium probs)

Phosphorus

• Bones & teeth: Forms hydroxyapatite with calcium for skeletal strength.

• Membranes: Creates the hydrophilic heads of phospholipids in bilayers.

• ATP: Stores and releases chemical energy via phosphate bonds.

• Creatine-P: Recharges ADP to ATP during rapid muscle contraction.

• Metabolism: Acts as a molecular switch through enzyme phosphorylation.

• Buffering: Maintains stable cellular and renal pH by absorbing hydrogen ions.

Magnesium

• Glycogen formation: Activates glycogen synthase by binding to oxygen atoms on phosphate groups.

• Metabolic regulation: Serves as a mandatory cofactor for all ATP-utilizing enzymes and kinases.

• Neuromuscular function: Acts as a natural calcium blocker to allow muscle relaxation and prevent hyperexcitability.

Iron

• Oxygen transport: Forms the core of hemoglobin and myoglobin to bind and deliver oxygen.

• Energy transfer: Serves as a key component in cytochromes for mitochondrial electron transport.

• Tissue repair: Acts as an essential cofactor for collagen synthesis and cellular growth.

• Low absorption: Only 10% to 15% of dietary iron is actually absorbed by the body.

• Female demand: Higher requirements due to monthly blood loss from menstruation.

• Male storage: Higher levels of ferritin provide men with superior long-term iron reserves.

Iron Deficiency

Women of childbearing age and those on vegetarian diets are at increased risk for dietary insufficiency, which could lead to inro-deficiency anemia

• small and lightly colored RBCs

Symptoms:

• general sluggishness

• loss of appetite

• pale skin

• sore tongue

• brittle nails

• frontal headaches

• dizziness

• reduced capacity to sustain even mild exercise and physical activity

Exercise Induced Anemia

Strenuous training may create added demand for iron that exceeds its intake, resulting in an iron drain and reduced physical performance

In contrast, several days of training increase plasma volume by 20% while RBC volume remains unchanged and hemoglobin concentration decreases in the expanding plasma volume. Although diluted, exercise training improves aerobic capacity and exercise performance and even leads to more liters of blood circulating the body.

The Electrolytes

Sodium, Potassium, and Chloride

• play key roles in membrane potential and total body fluid compartments (and total body water)

Electrical signals: Create the cellular voltage needed for nerve impulses and muscle contractions.

Water balance: Divide body water properly between the inside and outside of cells.

Fluid movement: Pull water across membranes via osmosis to prevent cell shrinking or swelling.

Concentration control: Keep the body's overall fluid thickness stable to trigger thirst or hydration.

Minerals and Exercise

Excessive sweating during exercise produces body water loss and loss of related minerals, the immediate need can:

• impair hear tolerance and exercise performance, leading to heat cramps, heat exhaustion, or heat stroke

• both body water and minerals must be replaced during and following exercise

Sweat loss during exercise usually does not increase mineral requirements above recommended values

Water

40-70% of total body mass (minimum 40-45%)

• varies with % body fat

• muscle is about 70% water

• fat is only 10% water

more fat= less total body water

Of the total water:

• about 60% is intracellular (inside cells)

• about 40% is extracellular (btwn cells) (plasma, interstitial, lymph, GI, urinary)

Water is the body’s primary transport medium

Lose most water though urine, to get rid of nitrogen

Balance is 2-3L of water

We can also make water- oxidation water

Water Requirement in Exercise

Loss of body water represents the most serious consequence of profuse sweating

Three factors determine amount of water loss

1. physical activity intensity

2. environmental temp

3. relative humidity

Each 0.45 kg (1lb) body weight loss corresponds to 450 mL (15oz) of dehydration

Overdoing the Water

Hyponatremia (“water intoxication”)

• low plasma Na+ creates osmotic imbalance across the BBB

• can lead to swollen CNS, headache, confusion, seizure, coma, cardiorespiratory edema/arrest, then death

DASH (Dietary Approaches to Stop Hypertension)

Balance! calories burned = calories replenished

Optimal Diet

• supplies required nutrients in adequate amount for tissue maintenance, repair, and growth without excess food intake

• individuals who regularly participate in physical activity to keep fit do no require additional nutrients beyond those from nutritionally balanced meals

Recommended Total Daily Nutrient Intake

Average values for young adults:

• about 2000 kcal for women

• about 3000 kcal for men

A variety of food sources supply extra energy demands for physical activity

Metabolism only slows down over time

Athletes burning a lot of calories should be replenishing a lot of calories

Recommendations for Protein, Fats, and Carbs

Protein

• recommended daily allowance equals 0.83 g per kg of body mass

• Athletes who train intensely should increase intake to 1.2 to 1.8 g per kg body mass

Fats (no real standards, from AHA)

• for “good” health, lipid intake should not exceeds 25 to 35% of total daily kcal intake

• >70% of total daily lipid intake should come from unsaturated fatty acids (limit sat and trans fats), olive oil

Carbohydrates

• recommendations for carbs intake range between 6 to 10 g/kg.BM/d, predominately unrefined and complex

• athletes on high end to preserve glycogen stores to preserve muscle protein

• a low carb diet rapidly compromises glycogen reserves for vigorous physical activity and intense training

Complex btwn exercise, slowly digested

Simple during exercise, easily digested

High-Carb vs. High-Fat

Diets rich in carbs maintain glycogen stores and evidence suggests that training and performance are much better compared to diets rich in lipids

Who do you need to look out for diet wise?

Gymnasts, dancers, and weight class athletes (boxers, wrestlers)

Need good amounts of water and calories

Pre-competition Meal

• foods high in carbs and low in lipids and proteins

• consume food three hours prior to event (1-4hrs)

Individualize meal by considering:

1. athletes food preference

2. psychological set of competition

3. digestibility of foods

The meal should maximize muscle/liver glycogen storage and provide glucose for intestinal absorption during activity

Carb Intake Pre-, During, and Post-Exercise

Pre-exercise: should be ingested >60 mins before

During exercise: 60 g carbs hourly to enhance high-intensity endurance performance

Post exercise: consuming carb rich, high glycemic foods immediately following intense training or competition speeds glycogen replenishment

• glycogen stores replenish 5 to 7% per hr with optimal carb intake

• full replenishment takes about 20 hours

Post-Exercise

• Consumption of foods with a relatively high glycemic index will help replenish glycogen stores (simple sugars are processed quicker and will raise Glycemic Index) so…

Simple Carbs: Made of one or two sugar molecules (monosaccharides or disaccharides). They digest and absorb very quickly, often causing a sharp rise in blood sugar.

Rehydration with a carb and electrolyte containing beverage will help to replace lost water and lost electrolytes, and provide energy to replenish glycogen stores

How much?

• about 50-75 g per hour or until a large carb meal

• drink about 1 L per hour of a solution containing 4-8% carbs

Glycemic Index and Performance

Pre Competition

• lower performance for pre comp meals with high glycemic index

• better performance for pre comp meals with low glycemic index