AB Biochemistry

PROTEIN METABOLISM Introduction to Digestion Digestion is the process of breaking down food into simpler parts. Most of the food we eat must be broken down into more basic components so that it can be absorbed into the body and utilized within it. Proteins are digested into amino acids. The diet of human beings consists of different types of proteins. As a result of digestion, these proteins ultimately get broken down into their simplest units, namely amino acids. The digestion of the protein begins in the stomach and is completed in the small intestine. Digestion of protein in the human body Digestion of proteins involves the enzymatic breakdown of large protein molecules into their building blocks—amino acids—so the body can absorb and use them. This process occurs in three major stages: in the stomach, small intestine, and with the help of pancreatic enzymes. In the mouth:  Proteins remain unchanged in the mouth as the saliva does not have any protein-digesting enzymes. In th...

Translation (mRNA → Protein) Translation is the process of the synthesis of proteins using the genetic information in mRNA as a template. During this process, the sequence of nucleotides in the mRNA is decoded to form a specific sequence of amino acids, which are joined together to form a polypeptide (protein). This process occurs in the cytoplasm after the mRNA has left the nucleus through a nuclear pore. All three types of RNA (tRNA, mRNA, and rRNA) are involved in transferring the information obtained from the sequence of nucleotides in DNA to the sequence of amino acids in the polypeptide chain of a protein. Steps in translation 1. Activation of amino acids 2. Transfer of amino acids to tRNA 3. Initiation of protein synthesis 4. Elongation of the polypeptide chain 5. Chain termination 1. Activation of Amino Acids In the cytoplasm, 20 different amino acids exist in an inactive form. Before they can participate in protein synthesis, they must be activated. This activation is catalyze...

Transcription Transcription is the biological process through which ribonucleic acid (RNA) is synthesized using DNA as a template. It marks the first step in gene expression, where the genetic information stored in DNA is transferred to RNA.                                     In this process, the sequence of nucleotides in DNA is copied into a complementary strand of RNA. Among the various types of RNA, messenger RNA (mRNA) plays a crucial role. It carries the genetic code from the nucleus (where DNA resides) to the cytoplasm, where proteins are synthesized by ribosomes. Hence, mRNA acts as a messenger between DNA and the protein-synthesizing machinery. During transcription, only one of the two strands of the DNA double helix serves as the template strand, also known as the non-coding or sense strand (Note: Some textbooks may switch these terms, so always refer to specific usage). This strand prov...

Replication of DNA DNA replication is the process by which DNA makes an exact copy of itself during cell division. This ensures that each daughter cell receives an identical copy of the genetic material. Steps in DNA replication 1. Initiation of DNA Replication The primary step for the double helical DNA molecule to be replicated is the separation of the two strands of the parent DNA molecule. The separation begins at the small region of the DNA molecule known as the origin of replication. In E. Coli, the origin of replication is called “oriC,” and in eukaryotes, it is referred to as the consensus sequence. The single chromosome found in E. Coli has only one origin of replication, whereas the eukaryotic chromosome has multiple origins of replication. 2. Formation of replication fork At the origin of replication, the two strands begin to unwind or separate. It assumes the V or Y-shaped structure called as replication fork. The separated strand in the replication fork acts as a template ...

Lipids Lipids are organic compounds that are insoluble in water but soluble in organic solvents such as benzene, chloroform, and ether. Simply, they are defined as esters of fatty acids and alcohol. Examples- fats, oils, waxes, and related compounds. Classification of Lipids Lipids are broadly classified into simple, complex, and derived lipids. 1. Simple lipids : They are esters of fatty acids with alcohols. These are mainly of two types (a) Fats and oils (triacylglycerols): These are esters of fatty acids with glycerol. The difference between fat and oil is only physical. Thus, oil is a liquid while fat is a solid at room temperature. (b) Waxes:- Waxes are the esters of fatty acids with high molecular weight monohydroxy alcohol. It is the esters of long-chain fatty acids with long-chain alcohols in place of glycerol. Cetyl alcohol is most commonly found in waxes. CH3-(CH2)28-CH2OH (myricyl alcohol) + CH3-(CH2)14-COOH (palmitic acid) à CH3-(CH2)28-CH2-O-C=O-(CH2)14-C...

  Protein Protein is an organic compound made up of a chain of amino acids bonded together by the peptide bond. Simply, it’s a linear chain of amino acid residues. The term protein is derived from the Greek word proteios, meaning holding the first place. Berzelius (Swedish chemist) suggested the name proteins to the group of organic compounds that are of utmost importance to life. Proteins are large, complex macromolecules made up of amino acids joined together by peptide bonds. Biochemically, proteins are polymers of α-amino acids, typically containing carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes sulfur (S). They are synthesized based on the genetic code (DNA) via the process of transcription and translation, and they perform a vast range of functions in living organisms. E.g.- albumin, globulin. Amino acids are organic compounds that combine to form proteins. They are building blocks of protein. They are better defined as organic compounds containing functi...

    Enzymes Enzymes are biocatalyst that increases the rate of chemical reactions occurring in the living body. They make a chemical reaction millions of times faster than it would have been without it. They are protein in nature (exception – RNA acting as ribozyme), colloidal and thermolabile in character, and specific in their action. The term enzyme was coined by a German physiologist, Wilhelm Kühne, in 1878. Nomenclature of Enzymes In the early days, the enzymes were given names by their discoverers in an arbitrary manner. For example, the names pepsin, trypsin, and chymotrypsin convey no information about the function of the enzyme or the nature of the substrate on which they act. Some old names indicate the source but not the action, e.g., papain from Papaya, bromelain from Pineapple of the family Bromeliaceae. Sometimes, the suffix-ase was added to the substrate for naming the enzymes, e.g., lipase acts on lipids; nuclease on nucleic acids; lactase on lactose. These ...