Nail growth |process|why nails keep growing – Biology Bug

Do you ever realize that your nails never stop growing. But how do they grow even after cutting? Let me tell you that they are growing before you were born. Nails are hardened structure made of dead cells. They grow by the process of keratinization. Keratin is a protein which is responsible for our hair and nail growth. The article discuss about why there is continuous growth of nails and what are the factors associated with it.

Key points: nail growth, structure of nail, process of growth, role of keratin

Keratin is a protein made by our skin cells. As the cells push upwards to the skin they die and becomes harden. This process is known as keratinization. However there are several other factors which contribute to the growth of nails. Amino acids are required to synthesize any protein in your body. Similarly the amino acids which are required for synthesizing keratin are dependent on amount of Sulfur present in your body. Vitamin A is essential for absorbing this protein. Vitamin C works with zinc to create a protein called collagen. This protein develop healthy connective tissue in your finger and rest of the body. Collagen is also known to be skin tightening and glowing agent. Before we discuss the process in details, let us understand some of facts regarding the nail growth.

1) Growth of the nails depends upon the season. They grow faster in summer than any other season. 2) Fingernails grow faster than toenails. 3) Men show higher rate of growth than women.

Note: Technically nails aren’t growing tissue, hence they do not grow. They are results of those cells which stopped growing due to their genetic mechanism.

Structure of Nail:

The structure includes these important parts,

  1. Matrix
  2. Cuticle
  3. Lunula
  4. Nail bed
  5. Nail plate
  6. Hyponichium
  7. Nail grooves

Matrix: This is the root of the nail. Its function is to make new cells. These new cells pushed up by the old one through the skin. This part contains lots of nerves and blood vessels which are essential for cell reproduction. Technically it is the only living part of the nails at initial stage but ultimately results into dead cells which forms nail.

Cuticle: This is a small sliver of skin where the nail grows out of the finger. It basically protects the matrix from any germs or infections

Lunula: it is a small whitish curved like structure that sometime you see at the bottom of the nails. It can be said as a part of the matrix. Most of the time it is under the skin. Therefore not every individual can see the lunula.

Nail bed: This area lies under nail plate. Nail plate is the visible part of nails which is the result of keratinization.

Hyponichium: this is the line where nail plate separates from nail bed.

Nail grooves: These are the grooves at the side of your free edge which gives direction for nail growth.

Process of Growth

  • The process starts with the DNA and the gene which codes for keratin. Especially in the case of nails there is one gene called as CRATIN which is actively present in our nail cells.
  • This gene will code for the protein i.e. keratin which will be more produced near the nail area.
  • Now the matrix is continuously producing cells because it is rich in blood vessels. The keratin is present in every cell until the cell undergoes a death cycle.
  • As more new cells are produced, the older ones get pushed up by the new cells. This is a sensitive phase where a mineral balance (zinc, iron, cobalt) and hormonal balance is required (minerelocorticoids, thyroxine etc.)
  • The keratin protein in the cells grows harder and beyond a certain point there are no longer living cells with nuclei.
  • The growing hard structure continues to from a nail plate. Most of the growth takes place underside the nail plate and that area is called as germinal matrix. The outer layer of germinal matrix is a half-moon shaped structure that is lunula.
  • The nail plate is loosely attached to the germinal matrix. It also held by some skin at the bottom and at its sides. As it grows the nail will acquire a concave shape.

 Why do we have nails?

The nails are flattened version of claws. It is one of the important features of primates. If you observe the arboreal animals like apes, monkeys, lemurs etc. possess the same feature. Humans are primates and nails are our distinguished character. They are nothing but dead cells and hence not really useful as claws.

Do nails grow after death?

No. it is clearly a myth. Fingernails might appear long after death. It is not because they are still growing but the skin around that area is retracted. If you have carefully observed that the skin and other soft tissues starts shrinking after death. It is an optical illusion which makes the nails look bigger than the ordinary size.

Can they stop growing in certain cases?

This depends on various factors. One of the common reason which we usually see around us is the habit of biting nails. This in certain cases can damage the nail bed or matrix or lunula. If any sensitive area of the nail is damaged because of biting, injury, accident or by using sharpened objects then there is a possibility that the nail might stop growing.

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PROTEINS: Definition its Structures, Domains and Motifs.

Key terms: proteins, structure of proteins, alpha helix, Beta sheet, loops, domains, motifs, folding, unfolding.

I am sure that you all must have heard this term ‘protein’ during your high school or college. But when it comes to study of proteins, sometimes it gets difficult for some people to clearly get that idea and basic concepts behind it. So have you ever imagined how exactly the protein looks like or how does it function at molecular level? Well then this article is for you. Let’s make it simple.

  • What are Proteins?

They are the organic compounds which contains a long chain of amino acids (polypeptide chain) and maintains the structural components of body. They are mainly present in the muscles (eg. myosin), nails, hair (eg. keratin), immune system (eg. antibody) etc. They are also present in the food and dairy products such as egg, milk, pulses, fish etc. These proteins can be extracted and used as supplement or therapeutic purposes.

  • Structure of Proteins

The structure depends on the nature of protein i. e. whether the protein is globular or fibrous in nature. But they are classified in the following four types:

  1. Primary structure
  2. Secondary structure
  3. Tertiary structure
  4. Quaternary structure

1.Primary structure

The primary structure of protein contains a simple chain of amino acids without any loops or turns inside it. They involve formation of peptide bond. The peptide bond is covalent bond formed between carboxyl group and amino group of two amino acids.

2. Secondary structure

This involves the folding of structure with respect to polypeptide chain due to the reaction between atoms. The folding results into two most common structures, alpha helix and beta pleated sheet.

A. alpha helix

The polypeptide chain is coiled spirally in this structure. The backbone forms inner part of the coil while the side chains extend outward from the coil. In this structure the carbonyl group of amino acid is bonded with the hydrogen of amino group via hydrogen bonding. Therefore it gives the appearance of ribbon to the secondary structure.

B. Beta sheet

The linear extended zigzag pleated sheet is formed by the hydrogen bonds which is either intramolecular or intermolecular. The sheet like structure is formed when two or more segments of polypeptide chain are present next to each other and connected via hydrogen bonds. Individual segments in beta sheets are known as beta strands and they are rarely found in proteins because the structure is not stable. When two adjacent beta strands line up, they can form bridges of hydrogen bonds. This stable structure is known as Beta sheet. However there are further two types of beta sheets: a) Parellel and b) Anti-parallel.

a) Parallel beta sheet:When beta strands line up edge to edge in the same direction, it forms highly stable sheet.

b) Anti-parallel beta sheet: Beta strands runs into opposite direction with each other. The anti-parallel conformation is more stable and more common than the parallel one.

  • Loops and turns in the secondary structure
  1. Loops and turns connect alpha helices and beta strands.
  2. The more common cause for a polypeptide chain to contain more loops is to make the structure more compact and stable.
  3. Loops that have only 4-5 amino acid residues are called as turns.
  4. When they have internal hydrogen bonds, loops generally have hydrophillic residues and are found on the surface of the protein. While turns and bends refer to short segments of amino acids that connect the ends of two adjacent segments of anti-parallel beta sheets.

Before moving to the tertiary structure, it is important to understand some basic concepts for the functions of protein such as domains and motifs.

  • Domains, motifs and folds

The polypeptide chains with more than 100 amino acid residues often fold into two or more stable globular units are called domains. The domain is a functional area of protein which performs certain physical or chemical activity. Along with the domains there are certain motifs that represent only the structural characteristics of protein. Motif does not perform functional activity, instead they are a part of domain. In many cases a domain from a large protein still retain to its 3-D structure even if it is separated from polypeptide chain. While it is not in the case of motif because it contains short sequences of amino acids.

3. Tertiary structure

It represents the entire three dimensional conformation of protein. It indicates all the secondary structure helices, loops, turns, bends, sheets and how are they assembled to form a domain in space. It basically explains the 3-D structure of single protein(unlike quaternary structure) and how do all the small components contribute to coiling and compacting the structure to make it stable.

4. Quaternary structure

The quaternary structure of protein involves the clustering of more than one protein chains into a specific shape. This complex structure of protein is formed via various reactions and interactions such as hydrogen bonding, salt bridge formation, disulphide bonds, van der waals forces, covalent bonds etc. It contains many sub units and give rise to a complex structure held by various bonds.