Nutrition: Protein Section 7/14/26

What are proteins

• Complex molecules that are essential components of human tissues

• Composed of amino acids

• Only macronutrient that has nitrogen.

• Energy: 4kcal/gram

Amino acids

• Humans use 20 specific amino acids to build protein

• 11 amino acids are nonessential (are not needed from diet)

• 9 amino acids are essential (not synthesized)

Protein synthesis

• Involves the nucleus and ribosomes

Transcription

DNA in the nucleus writes build instructions onto mRNA which leaves the nucleus.

Transcription

Ribosomes read instructions and assemble amino acids into proteins. (Proteins are not stored in the body).

Amino acid pool

Amino acids within cells can be used to make proteins.

Types of protein function:

• structural support

• contraction/movement

• transport

• biochemical process

• regulating and signaling

• immune support

collagen

“glue” for skin, bones, tendons, and ligaments

keratin

forms rigid structure of hair, skin, nails.

cells

help maintain cell shape

What proteins are involved in movement?

Actin and myosin

cellular transport

Proteins in cell membranes move in and out.

Protein channels

passive tunnels

carrier proteins

shuttles that act passively or actively

Fluid balance

albumin holds water inside of blood vessels

Alkalosis

Proteins act as a buffer by releasing hydrogen into the blood if it’s too basic.

Acidosis

Proteins take up hydrogen if it is too acidic.

What is good blood pH?

Maintained between 7.35 and 7.45

cell signaling

proteins act as receptors on cell surface to send and receive signals

Process of peptide hormones:

1) insulin binds to receptor

2) signals cascade

3) excyotosis

4) glucose entry permitted

basic way to describe hormones:

chemical messengers

Growth factors

Proteins that stimulate cell division and muscle growth.

Neuro transmission

Amino acids are precursors to neurotransmitters which send signals from to other nerve cells, muscles, or glands.

Antibodies

produced by the immune system to prevent against invaders

Nitrogen Balance

Nitrogen intake = Nitrogen used

Positive Nitrogen Balance

Nitrogen intake < Nitrogen used

Negative Nitrogen Balance

Nitrogen intake > Nitrogen used

complete proteins

contain all 9 essential amino acids in sufficient amounts

incomplete proteins

insufficient or lacking 1+ essential amino acids

complementary proteins

2+ incomplete protein sources with complementary essential amino acids

vitamin not found in plants:

Vitamin B12

Protein energy malnutrition (PEM) global impact:

a leading cause of childhood morality in developing countries

Kwashiorkar

Protein deficit, adequate calories (very severe).

Symptoms: edema, fatty liver, muscle wasting, infection risk

Marasmus

Protein and calorie deficit (starvation).

Symptoms: Severe muscle and fat wasting.

Bone health

Increases calcium excretion, but does NOT lead to bone loss (calcium intake > output).

Metabolic health

May contribute to weight gain if in a caloric surplus.