1F03 - UNIT 3

Amino Acids

Amino Acids

• building block of protein

• contain C, H, O, N

• joined by peptide bonds

• 9 essential and 11 non-essential

Protein Structures

primary: amino acid sequence

secondary: interactions between amino backbones

tertiary: R group interaction

quarternary: 2+ polypeptide interactions

Denaturation

• loss of stability, shape, function

• by heat + acid

Protein Absorption

• in small intestine

1. amino acid → enterocyte (intestinal cells)

2. used for energy and protein synthesis

3. unused → liver

Protein Synthesis

transcription: mRNA uses DNA template to copy info

translation: tRNA attaches amino acids (based on mRNA) in ribosome

Roles of Proteins

• building materials

• hormones

• enzymes

• transporters

Deamination

• removes amino acids containing N

• forms ammonia and keto acid

Ammonia → Urea

• NH3 + CO2 → urea

• direct relationship to dietary protein intake (requires H2O)

• in the liver

• urea into blood through kidney

Protein Turnover

making and breaking proteins (1-2% a day)

Amino Acid Pool

• no storage

• constant

• used to make other proteins

• for energy

Nitrogen Balance

• difference between nitrogen intake

• change in total body protein

• positive, equilibrium, negative

Protein During Endurance Exercise

• amino acid oxidation → < 5% of energy production in athletes

• acute exercise causes a small increase in leucine oxidation

  • may result in small increase in requirement

  • protein consumption during exercise is not improved performance

Protein Intake vs Strength Gains (Meta-Analysis)

• improvement of 1 rep max with protein during resistance training

• overall: improvement / more in trained athletes

Factors Determining Protein Quality

1. digestibility

2. amino acid composition

Digestibility

animal: 90 - 99 %

soy+legume: > 90 %

plant: 70 - 90 %

Protein Digestibility Corrected Amino Acid Score (PDCAAS)

• scale of protein quality / 0 to 100

dairy/eggwhite/beef/chicken = 100

soybean = 94

legumes = 50s and 60s

gluten = 25

Complete Protein Sources

• contain all essential amino acids

• chicken, salmon, soy, beef, whey, quinoa

Complementary Proteins

• combining plant proteins to create full amino acid complement

• pea flour (67) + whole wheat flour (40) = combined flour (82)

Plant-Based Protein

• decreased greenhouse gas emission

• can make up for low quality

• decreased diseased risk

Protein Energy Undernutrition (PEU)

• insufficient intake of protein, energy, both

• most prevalent form of malnutrition

• infections from degradation of antibodies

• reversible

• marasmus and kwashiorkor

Transfer of Energy (ATP)

• energy is captured in ATP

• negative charges of phosphate are vulnerable to hydrolysis

• cleaving P groups releases energy

Enzymes

• proteins

• facilitate reactions

• remain unchanged

Coenzymes

• complex and organic

• required for enzyme function

• derivatives of vitamines

Fates

acetyl CoA: makes fat and energy

glycerol → pyruvate: makes glucose or acetyl CoA

fatty-acids → acetyl CoA: oxidation (2C at a time)

aa → energy

• glucogenic (converted to pyruvate or enter TCA)

• ketogenic (converted to acetyl CoA)

Glycolysis: Glucose to Pyruvate

• 6C to 2(3C)

• in cytoplasm

• hydrogens attach to coenzyme

• produce ATP and NADH

Anaerobic Energy Production

• when lacking oxygen/mitochondria

• fast ATP but not sustainable

1. converted to lactate/lactic acid

2. lactate to liver

3. converted back to glucose

4. glucose back to muscles (cori cycle)

Pyruvate Oxidation: Pyruvate to Acetyl CoA

• pyruvate enters mitochondria

• carbon removed from pyruvate

• produces CO2 and NADH

• decarboxylation, redox, synthesis

Tricarboxylic Acid (TCA) Cycle

• releases H+ and electrons

1. acetyl CoA + oxaloacetate = citrate

2. 2 carbons stripped/released as CO2

3. 8 H+ (and electrons) released to ETC

4. oxaloacetate regenerated and cycle continues

Electron Transport Chain (ETC)

• uses H+ atoms to create ATP

1. coenzymes deliver H+ and electrons to inner mitochondrial membrane

2. simultaneously:

   1. electrons pass through carriers → form water

   2. H+ pumped into outer compartment

3. H+ flow through pump to create ATP

4. ATP to cytosol for cell use

Energy Balance

• energy in = energy out

• a shift in balance causes weight changes

• changes can be rapid or gradual

• excess energy is stored as fat

Energy In: Food Intake Factors

• appetite

• hunger

• satiation

• satiety

Energy Expenditure Components

• basal metabolism (BMR and RMR)

• physical activity

• food consumption (thermic affect of food)

• adaptation responses

Estimating Energy Requirements (EER) Influencers

• sex

• growth

• age

• physical activity

• body composition and size

Body Mass Index (BMI)

• standards for body weight → relative weight for height

• related to disease risk, based on population average, increased accuracy with waist circumference

BMI Classification

< 18.5 : underweight

18.5 to 24.9 : healthy weight

25 to 29.9 : overweight

> 30 : obese

Body Fat Assessment Methods

• waist circumference

• skinfolds

• bioelectrical impedance

• DEXA

Fat Distribution

• visceral fat (central obesity)

• subcutaneous fat

Waist Circumference

• indicator of visceral fat

women: > 35 inches

men: > 40 inches

Female Athlete Triad

• relationship between disordered eating, amenorrhea, osteoporosis

• leads to increase chance of stress fractures

Relative Energy Deficiency in Sport (REDs)

• includes men

• psychological. arrow goes both ways

• many physiological systems affected by low energy availability

Consequences of REDs

• ostopenia/osteoporosis

• decreased training adaptation

• decreased metabolism control

• decreased fertility

• thyroid dysfunctions

REDs Impacting Factors

• body image

• drive for thinness

• EDs

• making weight

• unintentional LEA

• lack of understanding of maturation

REDs Healing Guidelines

• fuel

• no diets + fasting

• carbs!

• daily energy balance

• decrease fibre intake

• strength training

Energy Availability

EA = EI - EEE

• relative to FFM

• healthy: 40-45 kcal/kg FFM/day

Energy Distribution Across Day

• athletes with menstrual disorder had more time spent in energy deficit

  • decreased RMR / decreased estradiol / increased cortisol / decreased T3

• athletes with low RMR had 2x more time in energy deficit

  • increased cortisol / decreased testosterone