Untitled Quiz

Learning Objectives

• List and describe the four basic functions of proteins in living organisms.
• Differentiate between the four levels of complexity of protein structure.
• Explain the importance of proteases in microbial metabolism.
• Explain the biochemistry involved in the utilization of casein by casein protease.
• Investigate the utilization of casein by the environmental isolate.
• Interpret the results found on the casein agar plates.

Introduction

• Studying an organism's structure, growth characteristics, and susceptibility to chemotherapeutics leads to studying biochemical or metabolic characteristics.
• Each organism adapts to its niche, including the development of physical structures and metabolic adaptations for nutrient utilization.
• This exercise studies biochemical adaptations of microorganisms, aiding in identifying unknown microbes.
• Microbes can be classified based on carbon source (heterotrophs or autotrophs) and energy source (organic chemicals, inorganic chemicals, or sunlight).
• Environmental isolates are chemoheterotrophs.
• Proteins are composed of amino acids. Amino acids are joined by peptide bonds.

Proteins

• Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
• Primary structure is the sequence of amino acids.
• Secondary structure involves interactions between adjacent amino acids (alpha-helices and beta-sheets).
• Tertiary structure is the overall three-dimensional shape of a polypeptide chain.
• Quaternary structure involves multiple polypeptide chains interacting.
• Structural proteins contribute to the organism's structure and cell components.
• Motility proteins aid in movement.
• Enzymes are catalysts that speed up chemical reactions.
• Antibodies are part of the immune response.

Casein Proteases

• Casein is a milk protein, giving milk its white color.
• Casein exists in colloidal molecules called casein micelles, carrying calcium and phosphate.
• Casein is commonly used in food (e.g., coffee whiteners, infant formulas).
• Casein is insoluble but caseinates (casein salts) are soluble.
• Cheese production involves fermentation of lactose by lactic acid bacteria.
• Acidic environment causes casein to coagulate (form curds).
• Whey is the liquid remaining after curds formation.
• Secondary fermentation occurs after removing liquid from curds.

Casein Agar Plates

• Creamy, opaque plates result from adding milk to agar.
• The presence of a casein protease (degrading casein) produces a clear zone around microbial growth on agar.
• If no protein digestion occurs, the medium around the growth remains cloudy.