PROTEINS: DEFINITION, FUNCTIONS & SOURCES

WHAT ARE PROTEINS?

Proteins are large, complex molecules that are essential for the structure, function, and regulation of cells and tissues in living organisms. They are one of the three major types of macromolecules found in all living organisms, along with carbohydrates and nucleic acids (DNA and RNA).

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Proteins are composed of long chains of smaller subunits called amino acids. There are 20 different types of amino acids that can be combined in various sequences to form various proteins. The specific sequence of amino acids determines the protein’s unique three-dimensional structure and, consequently, its particular function.

The synthesis of proteins occurs through a process called protein synthesis or translation, where the genetic information encoded in DNA is transcribed into mRNA and then translated by ribosomes to assemble the corresponding amino acids into a functional protein.

Overall, proteins are fundamental to life, and their diverse functions are essential for the proper functioning and survival of living organisms.

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25 FUNCTIONS OF PROTEINS

Proteins have a wide range of functions in living organisms, playing essential roles in various biological processes. Proteins are truly the workhorses of biology, carrying out an astounding array of tasks necessary for life and maintaining the proper functioning of cells and organisms. Their structural diversity and functional versatility make them essential components of every living system.

Here are some functions of proteins:

1. Enzymes: Proteins act as enzymes, catalyzing chemical reactions within cells. Enzymes accelerate the conversion of substrates into products, enabling crucial metabolic pathways and physiological processes.

2. Structural Support: Proteins provide structural support and integrity to cells, tissues, and organs. Examples include collagen in connective tissues, keratin in hair and nails, and actin and myosin in muscle fibers.

3. Transport: Transport proteins facilitate the movement of molecules and ions across cell membranes and throughout the body. Hemoglobin, for instance, transports oxygen in the blood.

4. Hormones: Some proteins serve as hormones, acting as chemical messengers that regulate and coordinate various physiological processes in the body. For example, insulin regulates blood sugar levels.

5. Defense: Antibodies (immunoglobulins) are proteins produced by the immune system to defend the body against foreign invaders like bacteria, viruses, and other pathogens.

6. Signal Transduction: Proteins play a crucial role in signal transduction pathways, relaying external signals from the environment or other cells to the cell’s interior. This communication helps regulate cell growth, metabolism, and other cellular processes.

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7. Contractile Elements: Proteins like actin and myosin are responsible for muscle contraction, enabling movement and locomotion.

8. Receptors: Receptor proteins on the cell surface or within cells bind to specific ligands (molecules), initiating a cellular response. This process is essential for cell communication and regulation.

9. Storage: Some proteins serve as reservoirs for essential molecules. For instance, ferritin stores iron in cells until it is needed for various biological processes.

10. Immune Response: Proteins involved in the immune system recognize and destroy foreign substances, helping to protect the body from infections and diseases.

11. Gene Expression Regulation: Regulatory proteins control the expression of genes, turning them on or off to regulate the production of specific proteins in response to cellular needs.

12. Metabolism: Various metabolic enzymes facilitate biochemical reactions that break down nutrients and generate energy for cellular activities.

13. Cell Adhesion: Proteins mediate cell adhesion, helping cells stick together to form tissues and organs. They also play a role in cell migration during development and wound healing.

14. Ion Channels: Ion channel proteins regulate the flow of ions (charged particles) across cell membranes, controlling the electrical properties of cells and enabling nerve impulses and muscle contractions.

15. pH Balance: Buffer proteins help maintain the body’s pH balance by stabilizing the acidity or alkalinity of bodily fluids.

16. Blood Clotting: Clotting factors, a group of proteins, are crucial for the formation of blood clots, which prevent excessive bleeding and promote wound healing.

17. Osmotic Balance: Some proteins in cell membranes facilitate the transport of water and maintain osmotic balance within cells.

18. DNA Replication and Repair: Proteins are involved in DNA replication, ensuring accurate duplication of the genetic material during cell division. They are also critical in repairing damaged DNA.

19. Neurotransmitters and Receptors: Neurotransmitter proteins facilitate communication between nerve cells, transmitting signals across synapses in the nervous system. Receptor proteins receive these neurotransmitter signals on target cells.

20. Photosynthesis: In plants and some bacteria, proteins are essential components of the photosynthetic machinery, capturing light energy and converting it into chemical energy.

21. Storage of Nutrients: Some proteins store essential nutrients like iron, copper, and zinc in the body, releasing them when needed.

22. Chaperones: Chaperone proteins assist in the proper folding of newly synthesized proteins, preventing misfolding and assisting in their transport within cells.

23. Toxins and Antitoxins: Some proteins act as toxins, while others function as antitoxins, protecting cells from the harmful effects of toxins.

24. Chromatin Structure: Histones are proteins that help package and organize DNA into chromatin, regulating gene expression.

25. Seed Nutrition: In seeds, proteins serve as a source of nutrition for the developing embryo.

These are just some examples of the diverse functions of proteins. Each protein’s function is determined by its unique three-dimensional structure, which, in turn, is dictated by the sequence of amino acids in its chain. The incredible versatility and specificity of proteins enable them to carry out these vital roles in all living organisms.

14 DEFICIENCIES OF PROTEINS

Protein deficiency, also known as protein-energy malnutrition, occurs when a person does not consume enough protein in their diet. Protein deficiency can have significant adverse effects on the body, as proteins are essential for various physiological functions. It is important to note that protein deficiency is relatively rare in well-nourished individuals who consume a balanced diet.

However, in certain populations with limited access to diverse and nutritious food sources, protein deficiency can still be a significant concern. Early recognition and appropriate intervention are crucial to prevent severe health consequences associated with protein deficiency. In such cases, medical professionals and nutrition experts can provide guidance and support to ensure adequate protein intake and overall nutritional health.

1. Kwashiorkor: This form of protein deficiency occurs when there is an inadequate intake of protein but a sufficient intake of calories from carbohydrates and fats. Kwashiorkor is often seen in regions where people rely heavily on starchy foods with little protein content. Common symptoms of kwashiorkor include:

– Edema (swelling) due to fluid retention, especially in the abdomen and legs.
– Muscle wasting and weakness.
– Changes in skin and hair texture.
– Fatigue and irritability.
– Stunted growth in children.

2. Marasmus: Marasmus is a severe form of protein-energy malnutrition resulting from a deficiency of both protein and overall calories in the diet. It often affects very young children who are not receiving adequate nutrition. Symptoms of marasmus include:

– Severe wasting of muscle and body fat, leading to an emaciated appearance.
– Weakness and lethargy.
– Poor growth and development.
– Frequent infections due to a weakened immune system.
– Thin, dry skin and brittle hair.

3. Impaired Muscle Function: Proteins are essential for muscle health and function. In protein-deficient individuals, there may be a reduction in muscle mass and strength, leading to muscle weakness and reduced physical performance.

4. Impaired Cognitive Function: Protein deficiency can negatively affect brain health and cognitive function. This is especially critical during periods of rapid brain development, such as infancy and early childhood, as insufficient protein intake may lead to learning and developmental delays.

5. Impaired Wound Healing: Proteins play a crucial role in tissue repair and wound healing. Inadequate protein intake can slow down the healing process and increase the risk of infections.

6. Hair Loss and Changes in Hair Color: Insufficient protein can result in hair loss (alopecia) and changes in hair color and texture, making the hair appear dull and brittle.

7. Skin Problems: Protein deficiency can lead to skin issues, including dryness, flakiness, and a higher susceptibility to skin infections.

8. Weakened Immune System: Proteins are vital for the proper functioning of the immune system. A lack of protein can weaken the immune response, making the body more susceptible to infections and diseases.

9. Anemia: Protein deficiency, particularly a deficiency in certain amino acids like lysine, can impact the production of hemoglobin and contribute to anemia, a condition characterized by low red blood cell count and reduced oxygen-carrying capacity in the blood.

10. Hormonal Imbalances: Some proteins serve as hormones or are involved in hormone regulation. Protein deficiency can lead to hormonal imbalances, affecting various bodily processes and functions.

11. Organ Damage: Chronic protein deficiency can cause damage to organs due to the body breaking down its own tissues for essential amino acids. This can lead to issues with liver, kidney, and heart function.

12. Increased Susceptibility to Infections: Protein deficiency weakens the body’s defense mechanisms, making individuals more susceptible to infections, including respiratory and gastrointestinal infections.

13. Increased Appetite and Stunted Growth in Children: Protein deficiency can lead to increased appetite as the body tries to compensate for the lack of essential nutrients. In children, it may result in stunted growth and developmental delays.

14. Electrolyte Imbalance: Some proteins help regulate fluid balance and maintain proper levels of electrolytes in the body. Protein deficiency can disrupt these processes, leading to imbalances in sodium, potassium, and other electrolytes.

Protein deficiency can lead to serious health consequences, including impaired growth and development in children, compromised immune function, and increased susceptibility to infections. In severe cases, it can be life-threatening.

To prevent protein deficiency, it is crucial to consume a balanced diet that includes a variety of protein sources such as meat, poultry, fish, eggs, dairy products, legumes, nuts, and seeds. Adequate protein intake is especially important during periods of growth, pregnancy, and lactation, as well as for individuals engaged in physically demanding activities or recovering from illnesses or injuries. If someone suspects a protein deficiency, it is essential to seek medical attention and follow appropriate dietary recommendations to address the deficiency and prevent further complications.

15 FOOD SOURCES OF PROTEINS

Proteins can be found in a variety of foods, both from animal and plant sources. Including a diverse range of protein-rich foods in your diet is essential for meeting your body’s protein needs. Remember that the protein content of foods can vary, so it’s essential to check nutrition labels or refer to reliable sources to get accurate information. The recommended protein intake can vary based on factors like age, sex, physical activity level, and overall health. Consulting with a healthcare professional or a registered dietitian can help determine your specific protein needs and create a well-balanced diet plan.

Common food sources of proteins:

1. Animal Sources:
– Meat: Beef, pork, lamb, poultry (chicken, turkey), and game meats (e.g., venison).
– Fish: Salmon, tuna, cod, haddock, trout, sardines, and many others.
– Seafood: Shrimp, crab, lobster, mussels, and other shellfish.
– Eggs: Eggs are a complete protein source, containing all essential amino acids.
– Dairy: Milk, yogurt, cheese, cottage cheese, and other dairy products.

2. Plant Sources:
– Legumes: Lentils, chickpeas, black beans, kidney beans, pinto beans, and other types of beans.
– Soy Products: Tofu, tempeh, edamame, and soy milk are rich sources of plant-based proteins.
– Peas: Green peas and split peas are good sources of protein.
– Nuts and Seeds: Almonds, peanuts, cashews, chia seeds, flaxseeds, and sunflower seeds.
– Grains: Quinoa, bulgur, farro, brown rice, and whole wheat products like bread and pasta.
– Vegetables: Certain vegetables, such as spinach, broccoli, Brussels sprouts, and asparagus, contain notable amounts of protein.
– Seitan: Also known as wheat gluten, it is a protein-rich meat substitute often used in vegetarian and vegan diets.

3. Plant-Based Protein Products:
– Protein Powders: Plant-based protein powders made from sources like pea, hemp, rice, or soy protein.
– Protein Bars: There are various protein bars available, often made with plant-based protein sources.

4. Dairy Alternatives (Plant-Based):
– Plant-based milk alternatives like almond milk, soy milk, oat milk, and hemp milk can provide some protein.

5. Dairy and Dairy-Based Products:
– Greek Yogurt: A high-protein yogurt variety that contains more protein than regular yogurt.
– Cottage Cheese: A cheese curd product known for its protein content.
– Whey Protein: A protein supplement derived from milk whey and commonly used by athletes and fitness enthusiasts.

6. Meat Alternatives (Plant-Based):
– Seitan: A high-protein meat substitute made from wheat gluten.
– Tempeh: A fermented soy product that is a good source of protein and nutrients.
– Plant-Based Burgers: Burgers made from plant-based protein sources like soy, peas, or beans.

7. Edible Insects:
– In some cultures, insects are consumed as a protein source. Examples include crickets, mealworms, and grasshoppers.

8. Quorn Products:
– Quorn is a brand that produces various meat substitutes made from a fungus-based protein called mycoprotein.

9. Spirulina and Chlorella:
– These are types of algae that are highly nutritious and contain a significant amount of protein.

10. Protein-Rich Snacks:
– Trail Mix: A combination of nuts, seeds, and dried fruits that can provide a protein boost.
– Protein Bars: Snack bars are designed to be rich in protein and convenient for on-the-go consumption.

11. Lentils and Pulses:
– Besides common beans, other pulses like lentils, black-eyed peas, and chickpeas are excellent protein sources.

12. Nutritional Yeast:
– Nutritional yeast is a deactivated yeast that is often used as a cheese-like seasoning. It’s also a good source of protein.

13. Hemp Seeds:
– Hemp seeds are rich in protein and also contain healthy fats and essential nutrients.

14. Green Peas:
– Green peas are not only a vegetable but also a good source of protein.

15. Wild Rice:
– Wild rice is a nutritious grain with a relatively higher protein content compared to other rice varieties.

Incorporating a mix of both animal and plant-based protein sources in your diet allows you to access a broad spectrum of amino acids and nutrients. For vegetarians and vegans, it’s especially important to combine different plant protein sources to ensure you’re getting a complete range of essential amino acids. For example, combining legumes with grains (e.g., beans with rice) or nuts/seeds with whole grains can help achieve a more balanced amino acid profile.

It’s worth noting that the protein content of different foods can vary significantly, so it’s essential to be mindful of your protein intake and dietary preferences to ensure you meet your individual nutritional needs.