Chapter 21: Biochemistry
21.4: Proteins
- Proteins
- Large biomolecules composed of amino acid chains that perform a wide range of functions in living organisms.
- Amino Acids
- The building blocks of proteins, containing an amino group (-NH₂), a carboxyl group (-COOH), and a unique side chain (R group).
- Peptide Bond
- The covalent bond formed between the carboxyl group of one amino acid and the amino group of another during protein synthesis.
- Polypeptides
- Long chains of amino acids linked by peptide bonds, which fold into functional proteins.
- Denaturation
- The process in which a protein loses its three-dimensional structure due to external factors such as heat, pH changes, or chemicals.
Protein Structure
- Primary Structure: The sequence of amino acids in a polypeptide chain.
- Secondary Structure: Local folding into structures like alpha helices and beta sheets due to hydrogen bonding.
- Tertiary Structure: The overall three-dimensional shape of a polypeptide, stabilized by interactions between side chains.
- Quaternary Structure: The arrangement of multiple polypeptide chains into a functional protein complex.
Functions of Proteins
- Structural Role: Proteins like collagen and keratin provide support in tissues and skin.
- Enzymatic Activity: Enzymes are proteins that catalyze biochemical reactions.
- Transport: Hemoglobin transports oxygen in the blood.
- Defense: Antibodies are proteins that protect the body from pathogens.
- Regulation: Hormones like insulin regulate physiological processes.
Protein Synthesis
- Occurs in ribosomes through the processes of transcription and translation.
- Transcription: DNA is transcribed into mRNA in the nucleus.
- Translation: mRNA is translated into a protein sequence at the ribosome with the help of tRNA.
Questions for Students
- What are amino acids, and how do they combine to form proteins?
- Describe the four levels of protein structure and their significance.
- What is denaturation, and how does it affect protein function?
- List the various functions of proteins in the body and provide examples.
- Explain the steps involved in protein synthesis, from transcription to translation.