Protein, Beginner iteration
I’m starting to realize that, although there is congruency with the direction of the educational/informative videos on the page, I can do a better job at synthesizing information to the layman. In acknowledgement of this issue, not that there is any particular consensus, I’m going to drop down into some of the basic knowledge that I’ve accrued over the years. Selfishly, I understand the importance on brushing up on past knowledge of some of the basics within the space of physiology. Diving into the literature and peer reviewed research on the macronutrients, such as, protein, carbs, and fats. This can serve myself and the beginner in a fashion I didn’t really anticipate, it may prove the “Brilliance in the Basics” mantra that I’ve lived by for so many years. So lets get down and dirty, and take a dive into those macro Nutrients that we all know and love. First up, we’re addressing Protein.
Protein:
Haurowitz, Felix, Koshland, Daniel E.. "protein". Encyclopedia Britannica, 14 Feb. 2025, https://www.britannica.com/science/protein. Accessed 23 March 2025.
protein, highly complex substance that is present in all living organisms. Proteins are of great nutritional value and are directly involved in the chemical processes essential for life. The importance of proteins was recognized by chemists in the early 19th century, including Swedish chemist Jöns Jacob Berzelius, who in 1838 coined the term protein, a word derived from the Greek prōteios, meaning “holding first place.” Proteins are species-specific; that is, the proteins of one species differ from those of another species. They are also organ-specific; for instance, within a single organism, muscle proteins differ from those of the brain and liver.
A protein molecule is very large compared with molecules of sugar or salt and consists of many amino acids joined together to form long chains, much as beads are arranged on a string. There are about 20 different amino acids that occur naturally in proteins. Proteins of similar function have similar amino acid composition and sequence. Although it is not yet possible to explain all of the functions of a protein from its amino acid sequence, established correlations between structure and function can be attributed to the properties of the amino acids that compose proteins.
Plants can synthesize all of the amino acids; animals cannot, even though all of them are essential for life. Plants can grow in a medium containing inorganic nutrients that provide nitrogen, potassium, and other substances essential for growth. They utilize the carbon dioxide in the air during the process of photosynthesis to form organic compounds such as carbohydrates. Animals, however, must obtain organic nutrients from outside sources. Because the protein content of most plants is low, very large amounts of plant material are required by animals, such as ruminants (e.g., cows), that eat only plant material to meet their amino acid requirements. Nonruminant animals, including humans, obtain proteins principally from animals and their products—e.g., meat, milk, and eggs. The seeds of legumes are increasingly being used to prepare inexpensive protein-rich food (see human nutrition).
The protein content of animal organs is usually much higher than that of the blood plasma. Muscles, for example, contain about 30 percent protein, the liver 20 to 30 percent, and red blood cells 30 percent. Higher percentages of protein are found in hair, bones, and other organs and tissues with a low water content. The quantity of free amino acids and peptides in animals is much smaller than the amount of protein; protein molecules are produced in cells by the stepwise alignment of amino acids and are released into the body fluids only after synthesis is complete.
The high protein content of some organs does not mean that the importance of proteins is related to their amount in an organism or tissue; on the contrary, some of the most important proteins, such as enzymes and hormones, occur in extremely small amounts. The importance of proteins is related principally to their function. All enzymes identified thus far are proteins. Enzymes, which are the catalysts of all metabolic reactions, enable an organism to build up the chemical substances necessary for life—proteins, nucleic acids, carbohydrates, and lipids—to convert them into other substances, and to degrade them. Life without enzymes is not possible. There are several protein hormones with important regulatory functions. In all vertebrates, the respiratory protein hemoglobin acts as oxygen carrier in the blood, transporting oxygen from the lung to body organs and tissues. A large group of structural proteins maintains and protects the structure of the animal body.
What Are Proteins?
Proteins are large, complex molecules made up of amino acids.
Think of them as molecular machines that do most of the work in your body.
🔗 Basic Structure:
Monomers: Amino acids (20 different kinds).
Polymer: A polypeptide (amino acid chain) that folds into a functional shape = protein.
Bond type: Peptide bonds between amino acids.
🧩 Amino Acids:
20 total.
9 are essential (must get from food).
Each has:
Amino group (–NH₂)
Carboxyl group (–COOH)
R-group (side chain — defines the type of amino acid)
🌀 Levels of Protein Structure:
Primary: Amino acid sequence
Secondary: Local folding (α-helix or β-pleated sheet)
Tertiary: 3D folding due to R-group interactions
Quaternary (optional): Multiple polypeptides combine (e.g., hemoglobin)
🛠️ Functions of Proteins:
Enzymes: Catalyze reactions (e.g., amylase)
Structure: Keratin (hair), collagen (skin/tissue)
Transport: Hemoglobin carries O₂
Hormones: Insulin regulates blood sugar
Defense: Antibodies fight pathogens
Movement: Actin & myosin in muscle
Storage: Ferritin stores iron
🍗 Food Sources:
Complete proteins (all 9 essential AAs): meat, fish, eggs, dairy, soy, quinoa
Incomplete proteins: nuts, legumes, grains (combine them for full profile)
⚙️ Digestion and Use:
Digested in stomach (pepsin) and small intestine
Broken into individual amino acids
Reassembled into new proteins by ribosomes in your cells
Enzymatic Function
Proteins as enzymes speed up chemical reactions by lowering activation energy.
Examples:
Amylase (breaks down starch)
DNA polymerase (builds DNA)
Lactase (digests lactose)
2. Structural Support
Give shape, strength, and support to cells, tissues, and organs. Proteins are most tightly packed where there is the least amount of surrounding water.
Examples:
Collagen (connective tissue, skin)
Keratin (hair, nails, outer skin layer)
Elastin (elasticity in skin and blood vessels)
Examples:
Soft Tissue
Muscle
Organs (soft tissue)
3. Transport & Storage
Carry molecules in blood or across membranes; store important substances.
Examples:
Hemoglobin (transports oxygen in blood)
Myoglobin (stores oxygen in muscles)
Albumin (maintains blood osmotic pressure)
Ferritin (stores iron)
4. Hormonal Regulation
Some hormones are protein-based and act as chemical messengers.
Examples:
Insulin (regulates blood glucose)
Glucagon (raises blood glucose)
Growth hormone (stimulates growth)
ADH (water balance)
5. Immune Response
Identify and neutralize pathogens.
Examples:
Antibodies (Immunoglobulins): bind to specific antigens
Cytokines: signal immune cells
6. Movement
Allow contraction and movement in cells and muscles.
Examples:
Actin & Myosin (muscle contraction)
Dynein & Kinesin (intracellular transport)
7. Cell Signaling
Relay signals from outside to inside the cell.
Examples:
Receptor proteins (insulin receptor, neurotransmitter receptors)
G proteins (signal transduction pathways)
8. Buffering
Help maintain pH balance by acting as buffers.
Example:
Hemoglobin also buffers pH in blood by binding H⁺ ions.
9. Energy Source (Last Resort)
When carbs and fats are low, proteins are broken down for energy.
1 gram = 4 kcal (like carbs).
Not ideal — leads to muscle breakdown.
10. Cell Adhesion & Recognition
Help cells stick together and identify one another.
Examples:
Cell adhesion molecules (CAMs)
Glycoproteins on cell surfaces (immune function, development)
11. Gene Expression and Regulation
Some proteins bind to DNA and turn genes on/off.
Examples:
Transcription factors
Histones (organize DNA)
Protein is found in abundance in the Human Physiology, with that being said. Not all essential amino acids, as we saw above, is found within our own ability to synthesize amino acids. Which is why it is so crucial for us to eat our protein from comlete protein sources, such as soy beans and legumes, and lets not forget animal products such as beef, pork, chicken, fish, and eggs. And as far as protein goes guys, this is a great place to begin, we can dive in deeper and with more rigor next time. Thanks!