9 Essential Functions of Protein in Your Body – Complete Guide

Protein stands as one of the most critical macronutrients your body needs to function properly. From building and repairing tissues to supporting your immune system, proteins perform countless essential tasks that keep you alive and healthy.

The word “protein” originates from the Greek term proteos, which translates to “primary” or “of first importance” – a fitting name considering how vital these molecules are to human health.

Structurally, proteins consist of long chains of amino acids linked together. Imagine a necklace where each bead represents an amino acid – that’s essentially what a protein molecule looks like at the molecular level.

Your body utilizes 20 different amino acids to construct thousands of unique proteins, each designed for specific functions. These proteins work primarily within your cells, carrying out diverse and crucial roles throughout your body.

Let’s explore the nine most important functions that proteins perform in your body.

1. Supporting Growth and Tissue Maintenance

One of protein’s primary roles involves building and maintaining your body’s tissues. Every cell in your body contains protein, making it fundamental to your physical structure.

Your body’s proteins exist in a continuous cycle of breakdown and renewal. Typically, your body maintains equilibrium, breaking down and rebuilding roughly equal amounts of protein to keep tissues healthy.

However, certain conditions increase your protein requirements significantly. During pregnancy, breastfeeding, or illness, your body breaks down more protein than usual, requiring additional protein intake to compensate.

Athletes, older adults, and people recovering from injuries or surgical procedures also need extra protein. Their bodies require more building blocks to repair damaged tissues and maintain muscle mass.

Without adequate protein intake during these critical periods, your body may struggle to maintain healthy tissues, potentially leading to muscle loss, weakened immunity, and slower recovery times.

2. Enabling Biochemical Reactions Through Enzymes

Enzymes represent a specialized class of proteins that facilitate thousands of chemical reactions occurring inside and outside your cells every moment.

These remarkable molecules work by binding to specific molecules called substrates. This binding triggers chemical reactions essential for your metabolism and survival.

Digestive enzymes provide excellent examples of proteins working outside cells. Lactase breaks down lactose in dairy products, while sucrase helps digest table sugar. Without these enzymes, your body couldn’t properly process many foods.

Many enzymes need helper molecules called cofactors to function properly. These cofactors often include vitamins and minerals, highlighting why a balanced diet matters so much.

Critical bodily functions dependent on enzymes include:

• Breaking down food during digestion
• Producing energy from nutrients
• Enabling blood to clot and stop bleeding
• Facilitating muscle contraction and movement
• Copying and repairing DNA

When enzymes malfunction or are absent, serious health problems can develop. Enzyme deficiencies can lead to metabolic disorders and various diseases.

3. Serving as Chemical Messengers

Many hormones are proteins that act as chemical messengers, facilitating communication between your cells, tissues, and organs.

Endocrine glands produce and release these protein hormones into your bloodstream, where they travel to target organs and tissues. Once there, they bind to specific protein receptors on cell surfaces, triggering specific responses.

Hormones fall into three main categories based on their structure:

Protein and Peptide Hormones: Constructed from amino acid chains ranging from just a few to several hundred amino acids in length. These make up the majority of your body’s hormones.

Steroid Hormones: Derived from cholesterol and including sex hormones like testosterone and estrogen.

Amine Hormones: Created from single amino acids, particularly tryptophan and tyrosine, and involved in regulating sleep and metabolism.

Important examples of protein-based hormones include:

• Insulin: Directs cells to absorb glucose from your bloodstream, regulating blood sugar levels
• Glucagon: Triggers your liver to release stored glucose when blood sugar drops
• Growth Hormone (GH): Promotes growth and development of bones and tissues
• Antidiuretic Hormone (ADH): Instructs kidneys to conserve water by reducing urine production
• Thyroid-Stimulating Hormone (TSH): Regulates thyroid function and metabolism

4. Providing Structural Support

Certain proteins called fibrous proteins give your cells and tissues their shape, strength, and elasticity.

Three crucial structural proteins include keratin, collagen, and elastin. These proteins create the connective framework supporting various body structures.

Keratin forms the protective outer layer of your skin and makes up the bulk of your hair and nails. This tough, fibrous protein helps shield your body from physical damage and environmental stressors.

Collagen ranks as the most abundant protein in your entire body. It provides structure to your bones, tendons, ligaments, and skin, essentially acting as the “scaffolding” that holds your body together. As you age, collagen production naturally decreases, leading to wrinkles and joint stiffness.

Elastin offers extraordinary flexibility – it’s several hundred times more elastic than collagen. This protein allows tissues to stretch and then snap back to their original shape. Your lungs, blood vessels, uterus, and skin all depend on elastin for their elasticity.

Without adequate amounts of these structural proteins, your body would lack the physical framework necessary for movement, protection, and proper organ function.

5. Regulating pH Balance

Proteins play a crucial role in maintaining the delicate acid-base balance in your blood and other bodily fluids.

The pH scale measures acidity and alkalinity, ranging from 0 (most acidic) to 14 (most alkaline), with 7 being neutral. Your blood maintains a slightly alkaline pH of approximately 7.4.

Even minor deviations from this optimal pH can prove harmful or fatal. Your body employs several buffering systems to prevent dangerous pH changes, and proteins form a key part of these systems.

Hemoglobin, the protein in red blood cells that carries oxygen, exemplifies how proteins buffer pH. Hemoglobin can bind to small amounts of acid, preventing your blood pH from dropping too low.

Here’s how different substances compare on the pH scale:

• pH 2: Stomach acid (highly acidic)
• pH 4: Tomato juice
• pH 5: Black coffee
• pH 7.4: Human blood (slightly alkaline)
• pH 8: Seawater
• pH 10: Milk of magnesia

Your body also uses phosphate and bicarbonate buffer systems alongside proteins to maintain proper pH. This multi-layered approach ensures your body chemistry remains stable even when you consume acidic or alkaline foods.

6. Maintaining Fluid Balance

Proteins help regulate your body’s fluid distribution, ensuring proper balance between blood and surrounding tissues.

Two key proteins – albumin and globulin – circulate in your bloodstream and attract water molecules. This attraction helps keep fluid inside your blood vessels where it belongs.

When you don’t consume enough protein, your body produces less albumin and globulin. Without sufficient amounts of these proteins, fluid leaks from your blood vessels into surrounding tissues.

As fluid accumulates in tissue spaces, swelling called edema develops. This condition appears most noticeably in the abdomen, legs, and feet.

Severe protein deficiency can lead to kwashiorkor, a form of malnutrition characterized by dramatic swelling of the abdomen. This condition occurs when people consume enough calories but insufficient protein – a situation rare in developed countries but still occurring in regions experiencing famine.

Maintaining adequate protein intake ensures your body can properly regulate fluid distribution and prevent uncomfortable or dangerous swelling.

7. Strengthening Immune Function

Your immune system relies heavily on proteins to protect you from disease-causing organisms.

Antibodies, also called immunoglobulins, are specialized proteins that identify and neutralize foreign invaders like bacteria, viruses, and other pathogens.

When harmful microorganisms enter your body, your immune system springs into action, producing specific antibodies designed to target these invaders. These antibodies attach to pathogens, marking them for destruction by other immune cells.

Without adequate antibodies, bacteria and viruses would multiply unchecked, causing serious infections and potentially life-threatening diseases.

Remarkably, once your body creates antibodies against a specific pathogen, specialized immune cells remember how to produce them. This immunological memory allows for rapid antibody production if you encounter the same pathogen again.

This memory response forms the basis of immunity – why you typically don’t get the same infection twice and why vaccines work to prevent diseases.

Protein deficiency can weaken your immune system significantly, making you more susceptible to infections and slowing recovery from illness.

8. Transporting and Storing Essential Nutrients

Transport proteins carry vital substances throughout your body, moving them into cells, out of cells, or between different locations.

These proteins transport various substances including vitamins, minerals, blood sugar, cholesterol, oxygen, and other essential nutrients.

Hemoglobin provides perhaps the best-known example. This protein captures oxygen in your lungs and delivers it to tissues throughout your body. Without hemoglobin, your cells would suffocate despite breathing normally.

Glucose transporters (GLUT proteins) move blood sugar from your bloodstream into cells where it’s needed for energy production.

Lipoproteins transport cholesterol and other fats through your bloodstream. Different types of lipoproteins include LDL (often called “bad” cholesterol) and HDL (“good” cholesterol).

Transport proteins show remarkable specificity – each type only binds and carries particular substances. A protein that transports glucose won’t carry cholesterol, and vice versa. This specificity ensures nutrients reach their proper destinations.

Some proteins also store nutrients for future use. Ferritin stores iron in your liver, spleen, and bone marrow, releasing it when your body needs to produce new red blood cells.

Casein, the primary protein in milk, serves as a storage protein providing amino acids to support infant growth.

9. Serving as an Energy Source

While not their primary function, proteins can provide energy when necessary.

Protein contains four calories per gram, matching carbohydrates and providing less than half the energy of fats (which contain nine calories per gram).

Under normal circumstances, your body strongly prefers using carbohydrates and fats for energy. These macronutrients are more efficiently metabolized for fuel, and your body maintains reserves of both for energy needs.

Your body reserves protein for its many other essential functions, only turning to it for energy in specific situations:

During Extended Fasting: After 18-48 hours without food, your body begins breaking down skeletal muscle to access amino acids for energy production.

Following Exhaustive Exercise: Intense or prolonged physical activity that depletes carbohydrate stores forces your body to break down muscle protein for fuel.

During Severe Calorie Restriction: When you don’t consume enough total calories, your body turns to muscle protein for energy, leading to muscle loss.

Using protein for energy is inefficient and undesirable because it means sacrificing muscle tissue and other important protein structures. Maintaining adequate calorie intake from carbohydrates and fats preserves protein for its essential structural and functional roles.

Understanding Your Protein Needs

Given protein’s numerous critical functions, consuming adequate amounts becomes essential for optimal health.

The Recommended Dietary Allowance (RDA) for protein is 0.8 grams per kilogram of body weight (0.36 grams per pound) for the average sedentary adult. However, many people benefit from higher intake.

Athletes, older adults, pregnant women, and people recovering from illness or injury typically need more protein to support their increased requirements.

Excellent protein sources include:

• Lean meats like chicken, turkey, and lean beef
• Fish and seafood
• Eggs and dairy products
• Legumes including beans, lentils, and chickpeas
• Nuts and seeds
• Whole grains like quinoa and oats
• Soy products such as tofu and tempeh

Combining various protein sources throughout the day ensures you obtain all essential amino acids your body needs.

The Bottom Line

Protein ranks among the most important nutrients for human health, performing an impressive array of essential functions.

From building and repairing tissues to facilitating chemical reactions, maintaining pH balance, regulating fluid distribution, and supporting immune function – proteins work constantly to keep you healthy and alive.

These remarkable molecules also provide structure to your body, transport vital nutrients, store essential compounds, and can even provide energy when necessary.

Collectively, these diverse functions make protein absolutely crucial for optimal health and wellbeing. Ensuring adequate protein intake through a balanced diet supports all these processes, helping you maintain strength, health, and vitality throughout your life.

Understanding how proteins work in your body highlights why meeting your protein needs should be a nutritional priority. Whether through animal or plant sources, consuming sufficient high-quality protein every day provides the building blocks your body needs to function at its best.

Sources:

• National Center for Biotechnology Information – The Cell: A Molecular Approach
• PubMed Central – Protein Requirements During Pregnancy
• PubMed Central – Enzyme Function and Metabolism
• NCBI – Molecular Biology of the Cell: Hormones
• NCBI – The Molecular Biology of Structural Proteins
• PubMed Central – Protein and pH Regulation
• PubMed Central – Protein and Fluid Balance
• PubMed Central – Proteins and Immune Function
• PubMed Central – Protein Transport and Storage
• PubMed Central – Protein Metabolism and Energy