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Protein functions

functions of protein


Let’s know how the protein performs in the human body??


Proteins are essential macronutrients to perform various functions in every system of the human body.


Amino acids-> Peptide -> Polypeptides (Or Proteins)


Peptide refers to short amino acid chains linked by the peptide bonds. When one or more polypeptides joined together, they are referred to as proteins.




∫∫ Proteins as Hormones


⇔ Glucagon


⇔ Vasopressin




∫∫ Proteins as Transporters

⇔ Hemoglobin


∫∫ Proteins for Structure


⇔ Keratin

⇔ Collagen

⇔ Elastin


∫∫ Proteins as Antibody

⇔ Immunoglobulin


∫∫ Proteins for growth & as an energy supplier


∫∫ Proteins for contraction

⇔ Actin & Myosin


∫∫ Proteins as fluids balancer

Albumin & Globulin


∫∫ DNA Associated Protein

⇔ Histones

⇔ Cohesin


∫∫ Proteins as Enzymes

⇔ Amylase

⇔ Lipase

⇔ Pepsin

⇔ Trypsin




Proteins as hormones:



Below listed are the peptide hormones present in the human body for various activities.


⇒ Adrenocorticotropic hormone (ACTH), Amylin, Angiotensin, Atrial Natriuretic peptide

⇒ Calcitonin, Cholecystokinin (CCK)

⇒ Follicle-stimulating hormone (FSH)

⇒ Gastrin, Ghrelin, Glucagon, Growth hormone

⇒ Insulin, leptin, melanocyte-stimulating hormone (MSH)

⇒ Oxytocin, Parathyroid hormone (PTH), Prolactin

⇒ Renin, Somatostatin

⇒ Thyroid-stimulating hormone (TSH), Thyrotropin-releasing hormone (TRH)

⇒ Vasopressin, Vasoactive intestinal peptide


The function of five peptide hormones alone listed below.




⇒ It’s a protein chain produced in islets of Langerhans in the pancreas.


⇒ It helps to maintain blood sugar levels.




⇒ A peptide hormone, produced mainly by alpha cells in islets of Langerhans in the pancreas.


⇒ Its prevents blood sugar level to fall too low. This hormone makes the liver release glucose into the blood.


Human Growth Hormone (HGH):


⇒ Known as SOMATOTROPIN or SOMATROPIN is a natural protein secreted by the pituitary gland.


⇒ It helps in the development of bone, muscles, and tissues.


⇒ Essential for cell regeneration and cell reproduction.


⇒ It helps to heal, boost metabolism, enhance muscle mass and burn fat.




⇒ Known as ARGININE VASOPRESSIN or ANTIDIURETIC HORMONE secreted by the posterior pituitary gland based on the signal from the hypothalamus. (Hypothalamus detects the water level in blood)


⇒ The main function is to constantly regulate and balances the amount of water in the blood.


AdrenoCorticoTropic Hormone (ACTH):


⇒ It is produced by the anterior pituitary gland.


⇒ It helps to regulate the level of the steroid hormone cortisol which released from the adrenal gland.


Thyroid Stimulating Hormone (TSH):


⇒ It’s a pituitary hormone that stimulates the secretion of thyroxine by the thyroid gland.


⇒ It plays a vital role in stimulating metabolism in every tissue.


⇒ This regulating the body in utilizing energy and perform heart and muscle functions.


⇒ It helps in maintaining body temperature, regulates mood and enhances muscle strength and maintenance of bones.






Proteins as transporters:


⇒ Two major classes of membrane transport are Channel protein and Carrier protein; used to perform two types of transport (active and passive).


⇒ Active transport takes place through the sodium-potassium pump, exocytosis, and endocytosis.


⇒ Passive transport takes place either through simple diffusion, osmosis, and facilitated diffusion. Channel proteins are involved in passive transport.


⇒ Channel protein can transport through membrane passively, whereas carrier protein can transport either facilitated diffusion(passive transport) or through secondary active transport.


⇒ Protein transporters are specific and do perform their own functions.


⇒ Proteins carry various substances of nutrients such as vitamins, minerals, sugar, cholesterol, oxygen.


⇒ Some proteins transport nutrients, while some protein acts as storage for nutrients.


⇒ Thyroxine binding protein is a transport protein that binds thyroid hormone and carries around the bloodstream.




⇒ Hemoglobin protein is the reason that makes blood red. It contains four proteins two alpha chains and two beta chains, oxygen binds reversibly. It helps to maintain normal Ph value of blood.



NOTE: Proteins and polypeptides make up most of our body hormones.



Proteins for structure:


Below mentioned is the fibrous protein that aids in the structure, strength, and elasticity of the human system.




It’s a protein helps to form the skeletal system of living cells.  Tubulin which helps to form microtubules which assist cell to undergo mitosis and to regulate intracellular transport.




⇒ An essential protein present in the epidermis.


⇒ It assists in adhere cells to each other and protects epithelial cells from damage.


⇒ It’s the main structural material present in hair, nails and outer layer of skin.




⇒ The main protein present in the body.


⇒ It’s the main component of connective tissue, which is present in tendons, ligaments, skin, and muscles.


⇒ Its also found in blood vessels, cornea, muscles, gastrointestinal tract, and intervertebral discs.




⇒ Elastin present in connective tissue but more specifically in the extracellular matrix of the skin and in internal organs.


⇒ Since it’s an elastic protein, it helps tissues to return to their original shape after any contraction or stretching.


Proteins as Antibody:




⇒ The antibody is known as Immunoglobulin.


⇒ Its a Y shaped glycoprotein molecule produced by plasma cells used to neutralize pathogens such as bacteria or viruses.


⇒ It’s used by the immune system for recognizing and binding to a specific antigen and assist till destructing it entirely.


⇒ Five immunoglobulin classes of antibody molecules found in serum:


IgG, IgM, IgA, IgE, IgD



FACTS: A protein’s shape determines its function.



Proteins for growth & as energy supplier:


Protein supplies the human body with a little amount of energy during normal circumstances.


In general fats and carbs provide energy to the body, but protein supply is more at essential times such as during fasting, low-calorie intake, after a great workout, or when the body breaks down skeletal muscles.


Proteins are required for the growth and maintenance of tissues. During normal conditions, protein utilization is less, but the body breaks down more protein based on the needs of the human body (ie, after an injury, illness, pregnancy, breastfeeding or after surgery).


Proteins for contraction:


Contractile proteins are meant for muscle contraction and movement.


Actin & Myosin:


⇒ Muscle contraction occurs as a result of the interaction of actin and myosin filaments moving relative to each other.


⇒ Actin (thin filament intercellular protein) and myosin (thick filament motor protein) play an essential role in muscle contraction as well as in cell movements, shape, and its entire architecture.


Proteins as fluid balancer:


Blood proteins such as albumins and globulin help to maintain the fluid balance between blood and surrounding tissue.


Albumins and Globulin:


⇒ Albumins consist of 50% to 60% of blood plasma proteins, whereas globulins make upto 38% of blood protein.


⇒ It maintains body fluid either by attracting and retaining water. It helps to regulate the concentration of acidic and bases(alkaline) levels in solutions such as blood and all other body fluids.


Other bodily fluids listed below: 


⇒ Blood, Blood Plasma, Cerebro Spinal Fluid (CSF)

⇒ Urine, Tears, Saliva, Serum, Semen

⇒ Amniotic fluid, Synovial fluid, Mucus

⇒ Lymph, Aqueous humour, Bile

⇒ Vaginal lubrication, Breast milk

⇒ Vitreous body, Chyle, Gastric acid, Pus

⇒ Intestinal fluid, Transudate, Phlegm

⇒ Earwax, Rheum, Colostrum, Sebum

⇒ Chyme, Lochia, Human feces, Hemoglobin

⇒ Pre-ejaculate, Metabolic water, Intestinal juice

⇒ Pericardial effusion, Smegma, Glycocalyx


DNA association protein:


Proteins that are involved in the process of providing structure to DNA in the form of chromatin are referred to as DNA associated protein.


These proteins help to regulate gene expression and chromosome structure during cell division, regulate cell growth, it stores DNA inside the nucleus and controls protein production.




⇒ It’s the main protein in chromatin. Chromatin is made up of DNA and protein.


⇒ Its essential function is to form DNS into structural units as nucleosomes.


⇒ It helps in gene regulation.




⇒ This protein component, play a role in the cell division processes like mitosis or meiosis.


⇒ It helps to hold sister chromatids together until anaphase stage in order to prevent the premature separation of sister chromatids.


⇒ Cohesion involved as one of the main key factors for efficient repair to DNA damage.


⇒ It’s crucial for the regulation of transcription and 3D chromatin organization.


Proteins as Enzymes:


Enzymes are proteins that act as a catalyst to initiate chemical reactions in the human body.


Digestive enzymes such as amylase, lipase, protease and various other enzymes are used in the digestion process.




⇒ Salivary amylase is secreted by a salivary gland in the mouth to break down starch into smaller carbohydrates (maltose).


⇒ Pancreatic amylase secreted by pancreatic cells which pass to the small intestine where it completes the digestion of carbohydrates and produces glucose.


⇒ Glucose, a small molecule that is absorbed into the blood and is carried throughout the body.




⇒ Lipase enzyme breaks down dietary fats into small molecules as glycerol and fatty acids.


⇒ Stomach cells create gastric lipase, which specifically digests butterfat in food.


⇒ The pancreas secretes pancreatic lipase which acts in the small intestine for completion of fat digestion along with bile (secreted from the liver).


⇒ Finally, glycerol and fatty acids get absorbed in blood and travel throughout the body.




Protease enzymes (Proteinase or Peptidase) performs proteolysis. i.e, break down of proteins into smaller units from polypeptides -> peptide bonds -> amino acids -> single amino acid.


In simple terms,


Amylase -> For carbohydrate ( Converting to glucose)


Protease -> For proteins ( Converting to peptides & amino acids)


Lipase -> For fats (Converting into fatty acids & glycerol)


Various other bodily functions such as muscle contraction, blood clotting, and energy production are depending on specific enzymes to take place.

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