What Are the Components of an Egg Shell?

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In summary, egg shells are rare biological materials that are composed mainly of calcium carbonate, with small amounts of magnesium carbonate and calcium phosphate. They have a porous structure and are made up of three layers - the mammillary layer, the middle layer of calcite crystals, and the top layer of protein. This structure provides strength and protection against breakage in certain directions. This information was taken from the USDA's Egg Grading Manual.
  • #1
Gonzolo
Hard substances are rare in biology. Egg shells feel and crack like ceramics, but it probably has carbon in it. It's not like nails and horns is it (dry and dead cells right?)? Bone? Please help me understand hard biological materials.
 
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  • #2
Egg shells are made of calcium carbonate

Gonzolo said:
Hard substances are rare in biology. Egg shells feel and crack like ceramics, but it probably has carbon in it.



  • Date: Tue Feb 23 14:22:01 1999
    Posted By: Joe Regenstein, Faculty, Food Science, Cornell University
    Area of science: Cell Biology
    ID: 919616162.Cb
    -------------------------------------------------------------------------
    Message:


    The cell of a chicken egg is made up of about 94 percent calcium carbonate
    (Ca(CO3)2), 1 percent magnesium carbonate, 1 percent calcium phosphate, and
    about 4 percent organic matter, mainly protein. The egg shell has pores
    through which air, moisture, and even bacteria can pass. The shell
    represents about 11 percent of the weight of an egg. The shell is made up
    of three parts -- the mammillary or inner layer is adjacent to the shell
    membranes and has a "knob" like appearance. The middle layer, the bulk of
    the shell is made up of small calcite crystals, mostly randomly arranged
    with the pores running through it. The cuticle or top layer is a thin film
    of protein that covers the egg when it is layed, but which drys up and
    flakes off over time. The organization of the shell (i.e., the crystals of
    calcite) provides a rigid structure that protects against breakage in
    certain directions. On the other hand a small tap in some directions will
    crack the shell.

    The information about the shell was taken from the USDA's Egg Grading
    Manual.
 
  • #3
It's (almost) chalk! Thanks.
 

What is the composition of an eggshell?

An eggshell is primarily composed of calcium carbonate, which is a mineral compound. It makes up the outermost layer of an egg and provides protection to the developing embryo inside.

How much calcium carbonate is in an eggshell?

Approximately 94% of an eggshell's composition is calcium carbonate. This mineral gives the eggshell its hardness and strength.

What are the other components of an eggshell?

In addition to calcium carbonate, an eggshell contains small amounts of other minerals such as magnesium carbonate and traces of proteins. These components contribute to the shell's structure.

What gives the eggshell its color?

The color of an eggshell can vary depending on the bird species but is often influenced by pigments that are deposited during the shell formation process. For example, in chicken eggs, brown pigment is added, while in some birds, like bluebirds, the pigment biliverdin contributes to blue-green eggshells.

How is the eggshell formed?

The formation of an eggshell is a complex biological process. It begins in the hen's uterus, where calcium and other minerals are deposited around the egg's membrane. This process gradually builds up the eggshell over about 20 hours.

Why is calcium carbonate used to make eggshells?

Calcium carbonate is used because it provides strength and protection to the developing embryo. It forms a hard outer layer that shields the egg from physical damage and helps maintain a stable internal environment.

Can eggshells be used for any practical purposes?

Yes, crushed eggshells are often used as a calcium supplement for plants and garden soil. They can also be used in composting to add calcium to the compost. Additionally, some people use finely ground eggshells as a dietary calcium source.

Is the composition of eggshells the same for all bird species?

No, the composition of eggshells can vary among bird species. Different species may have variations in the types and amounts of minerals and pigments present in their eggshells.

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