Universidad Anáhuac · Nutrition & Sport Science

Build → Fuel → Perform

Proteins, from molecule to muscle.

Build

Pizarro

Fuel

Raul Korenfeld

Perform

Emiliano Niño de Rivera

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Build

Pizarro · Biochemistry & structure

Field of view

1×

Raw meat, straight from the pan.

The graphic exaggerates scale for clarity — the zoom is real, the bead-and-ribbon drawings that follow are not photographs.

Amino acids, linked

Proteins are macromolecules built from amino acids joined by peptide bonds — a covalent bond between one amino acid's carboxyl group and the next one's amino group, releasing water.

The body uses 20 amino acids. Nine are essential — they must come from food:

Histidine

Isoleucine

Leucine

Lysine

Methionine

Phenylalanine

Threonine

Tryptophan

Valine

Four levels of structure

Click through the build.

Primary

Linear sequence of amino acids

Held by · Peptide bonds

Secondary

Local folding — helices, sheets

Held by · Hydrogen bonds

Tertiary

Full 3D fold of one chain

Held by · R-group interactions

Quaternary

Multiple chains as one unit

Held by · Non-covalent interactions

Sequence determines shape. Shape determines function.

Why so many proteins?

20^n

20 amino acids per position — sequence space explodes with chain length.

~20,000 → 1M+

~19,000–20,000 protein-coding genes; alternative splicing and post-translational modification push the estimated protein count into the hundreds of thousands, by some estimates over a million.

Same materials, different jobs

Collagen

Fibrous strands — structural support

Antibody

Y-shaped — immune recognition

Fuel

Raul Korenfeld · Nutrition & food sources

The same building blocks arrive through food — the amino acids from the last act, sourced from what's on the plate.

0.8 g/kg

The general baseline (WHO/FAO and EFSA converge close to this). For a 70 kg adult, roughly 56–58 g/day.

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ISSN 2017 position stand targets update live.

70 kg

Sedentary adult

56 g/day

~0.8 g/kg

Endurance athlete

84–112 g/day

~1.2–1.6 g/kg

Strength/power athlete

112–140 g/day

~1.6–2.0 g/kg

Spread roughly every 3–4 hours, in doses of ~0.25 g/kg (20–40 g), ideally with 700–3000 mg of leucine.

Complete vs. incomplete sources

Complete — all 9 essential

Meat

Poultry

Fish

Eggs

Dairy

Soy

Quinoa

Incomplete — pair to complete

Legumes

low in methionine, tryptophan

Grains

low in lysine

Nuts & seeds

low in methionine, lysine

Rice + beans, peanut butter + whole-grain bread → complementary pairing covers the gap. Doesn't need to happen in the same meal.

Perform

Emiliano Niño de Rivera · Physiology, health & performance

The finished protein goes to work.

Seven jobs, one molecule class

Every role traces back to the same building blocks.

Protein

Structural

Collagen, keratin

Enzymes

Nearly every reaction

Transport

Hemoglobin

Immune defense

Antibodies

Signaling

Insulin & hormones

Fluid balance

Albumin

Movement

Actin & myosin

When it's missing

Kwashiorkor

Adequate calories, too little protein

Low albumin lets fluid leak into tissue — edema, plus fatty liver, thinning hair, growth retardation.

Marasmus

Both protein and calories too low

Severe wasting and emaciation — mostly seen in infants.

And too much?

Genuinely debated — not a clean verdict.

Healthy kidneys

A large umbrella review found no clear evidence that higher intake specifically triggers kidney disease. Intakes up to ~2.0 g/kg/day are well-supported as safe for healthy, active people.

Reduced kidney function

Higher intake is linked to faster decline — restriction is standard clinical practice here.

Practical takeaway

Up to ~2.0 g/kg/day is well-supported as safe for healthy, active people. The real caution is pre-existing kidney conditions — not protein intake itself.

How muscle actually grows

Training tips the balance. Protein tips it further.

Toggle the state — watch the arm respond.

Net result

Slight gain

Mechanical stress plus the amino acid leucine activate mTOR, switching on the machinery that builds new muscle protein. Whey delivers leucine fast, producing a bigger synthesis spike than soy or casein; casein's slow release is useful before sleep.

Net growth is about consistent intake across the day, not one post-workout shake — the "anabolic window" is real, but wider than the 30–45 minute myth: sensitivity to amino acids lasts at least 24 hours post-training.

For a strength athlete, that means the 1.6–2.0 g/kg/day from the last section — in 20–40 g doses spread across the day — is exactly what this curve is asking for.