BIOL 329 Midterm Exam Exercise 14 and 15 Starch, Lipid, Gelatin, and Carbohydrate Degradation

What is cellular metabolism?

the sum of all chemical reactions occurring in a cell

What are enzymes?

biological catalysts that govern biochemical transformations inside and outside of the cell

What are exoenzymes?

extracellular enzymes; act on substances outside of the cell; degrade high molecular weight materials into lower weight material that can be transported into the cell

True or False: exoenzymes are mainly hydrolytic enzymes

True! reduce molecules into building blocks by using water, which allows them to become smaller and transported into the cell

What are endoenzymes?

intracellular enzymes; function inside the cell and are responsible of synthesis of new protoplasmic requirements and production of extracellular energy from assimilated material

What is starch?

high molecular-weight branching polymer composed of glucose linked together by glycosidic bonds

What is amylase?

an enzyme involved in the extracellular breakdown of starch, and is involved in the hydrolysis of starch into shorter polysaccharides and ultimately maltose molecules

What is the purpose of starch agar?

used to demonstrate the hydrolytic activity of amylase

What is a starch test used for?

test used to determine the presence of starch in a media, meaning that if starch is present, hydrolytic activity of amylase does not occur

What is a negative result for a starch test?

presence of iodine imparts a blue-black color to the medium, indicating the absence of starch-splitting enzymes

What is a positive result for a starch test?

if the starch has been hydrolyzed, a clear zone of hydrolysis will surround the growth of the organism

What is lipase?

an exoenzyme that hydrolyzes triglycerides so that they're small enough to enter the cell

How does lipase produce glycerol and fatty acids?

lipase cleaves the ester bonds of triglycerides, producing glycerol and fatty acids that can be further metabolized to produce ATP

What is tributyrin agar used for?

to demonstrate the hydrolytic activities of the exoenzyme lipase

What is tributyrin agar made of?

composed of nutrient agar with triglyceride tributyrin as the lipid substrate

What is a positive result for lipid hydrolysis?

the loss of opacity due to hydrolytic reaction yielding soluble glycerol and fatty acids

What is a negative result for lipid hydrolysis?

no loss of opacity, or no clearing, meaning the bacteria does not have lipase

What is gelatin?

polymer gel composed of interlocking strands of collagen

What is collagen?

a protein polymer that forms the principal component of connective tissue in vertebrate animals

What is gelatinase, or collagenase?

extracellular enzyme that degrades collagen into individual amino acids that can be used as a source of energy for biosynthesis

What is the use of nutrient gelatin deep tubes?

demonstrate the hydrolytic activity of gelatinase

What does it mean if the nutrient gelatin deep tube remains liquidized?

the bacteria produced gelatinase and undergoes gelatin hydrolysis

What does it mean if the nutrient gelatin deep tube remains solid?

the bacteria does not produce gelatinase and does not undergoe gelatin hydrolysis

How can the ability of an organism to degrade and ferment carbohydrates be determined?

via the production of acid or acid and gas

What is the carbohydrate fermentation test?

used to determine the ability of an organism to ferment various simple carbohydrates (sugars)

True or False: some organisms are capable of fermenting sugars such as glucose (also known as dextrose) anaerobically, while others use the aerobic pathway

True!

What happens in fermentation?

substrates such as carbohydrates and alcohols undergo anaerobic dissimilation and produce organic acid (ex. lactic acid) that may be accompanied by gases such as carbon dioxide

What is the Embden-Meyerhof pathway?

the glycolytic pathway, or glycolysis

What happens in the glycolytic pathway?

one mole of glucose is converted into two moles of pyruvic acid, which is an intermediate in glucose degradation; this pyruvate can be converted into various end products depending on the organism

Where does fermentation degradation under anaerobic conditions take place?

carried out in a fermentation broth tube containing a Durham tube that can be used to detect gas production

Why is phenol red, a pH indicator, included in a carbohydrate fermentation medium?

phenol red changes colors at different pHs; it is red at a pH of 7, and changes yellow at a slightly acidic pH of 6.8

In a carbohydrate fermentation test, what is a positive reaction?

phenol red turns yellow, since the carbohydrates that have been fermented produce acidic waste

True or False: acid production can be accompanied by the evolution of gas, which is visible as a bubble in the inverted tube

True!

In a carbohydrate fermentation test, what is a negative reaction?

no change in phenol red, tube stays red and there is no gas; bacteria is unable to ferment the carbohydrate

What does it mean if the phenol red turns a deep red in a carbohydrate test?

peptones are present in the nutrient broth, which can be degraded into amino acids and converted to keto-amino acids; these are further metabolized, producing an alkaline environment

What would the tube of carbohydrate fermentation test look like if no fermentation, but rather peptonization with the production of ammonium hydroxide (alkaline end products) occurred?

the broth would be a dark, pinkish red