Proteins

Ribosomes are the cellular structures responsible for protein synthesis. They are composed of ribosomal RNA (rRNA) and proteins, and they can either be found floating freely in the cytoplasm or attached to the rough endoplasmic reticulum (ER). Ribosomes read messenger RNA (mRNA) sequences to assemble amino acids into proteins according to the genetic instructions provided by the DNA. Thus, ribosomes are responsible for producing proteins in the cell.

Concept: Colostrum is the first milk produced by the mother immediately after childbirth. It is rich in proteins, vitamins, minerals, and especially antibodies that provide passive immunity to the newborn. Immunoglobulins (antibodies) are proteins produced by the immune system to fight against pathogens such as bacteria and viruses.

Step 1: Understanding antibodies present in colostrum. Among different types of antibodies ( , , , , ), Immunoglobulin A (IgA) is the most abundant in human colostrum.

Step 2: Role of IgA in newborn immunity.
• IgA protects mucosal surfaces such as the gastrointestinal and respiratory tracts.
• It prevents pathogens from attaching to the mucous membranes.
• It provides passive immunity to the newborn during the early stages of life.

Step 3: Conclusion. Therefore, the antibody most abundant in human colostrum is IgA.

Concept: Proteins are polymers made up of amino acid monomers. The bond that links two amino acids together is called a peptide bond.

Step 1: Structure of amino acids. Each amino acid contains:
• An amino group ( )
• A carboxyl group ( )
• A hydrogen atom
• A variable side chain (R-group)

Step 2: Formation of peptide bond. A peptide bond forms when the carboxyl group of one amino acid reacts with the amino group of another amino acid.

Step 3: Condensation reaction. During this reaction, a molecule of water is released, forming a peptide linkage: This process forms long chains called polypeptides which fold into proteins.