starch hydrolysis practical

"What are the two main types of molecules that make up starch?"

"AMYLOSE: long chains of glucose molecules

AMYLOPECTIN: branched chains of glucose molecules"

"Why is starch considered a significant nutrient source for bacteria?"

"Starch can provide a large nutrient source due to its thousands of glucose units.

Glucose is a simple monosaccharide that bacteria can easily take up and use to produce energy (ATP)."

"What is the problem bacteria face when utilizing starch?"

"Starch is too large to pass through the bacterial cell membrane.

Bacteria need specific enzymes to break down starch into usable glucose."

"What enzyme do bacteria secrete to break down starch?"

"α-AMYLASE: an enzyme that breaks down glycosidic bonds between glucose molecules.

This enzyme is essential for bacteria to utilize starch as a nutrient source."

"What type of media is used to determine the presence of α-amylase?"

"STARCH AGAR: a medium that contains starch.

This media helps in identifying bacteria that can produce α-amylase by observing starch hydrolysis."

"What is the process to determine if a bacterium produces α-amylase?"

"Inoculate bacteria onto a starch plate and grow overnight.

Observe if α-amylase is secreted and diffuses into the agar, breaking down starch to glucose."

"What happens when iodine is added to a starch plate after bacterial growth?"

"Iodine reacts with starch, producing a dark brown/black color.

Iodine does not react with glucose, indicating starch breakdown if the agar around bacteria does not turn dark."

"What are the possible results from a starch hydrolysis test?"

"If the agar around bacteria turns dark brown/black, starch is present, indicating α-amylase is negative.

If the agar does not turn dark, starch has been broken down to glucose, indicating α-amylase is positive."

"How can you tell if a bacterium is α-amylase positive after iodine treatment?"

"The agar around the bacteria does not turn dark brown/black, indicating no starch is present.

This suggests that starch has been hydrolyzed to glucose, which does not react with iodine."

"What are the possible results from a starch hydrolysis test?"

"Positive result: Zone of clearing around the bacterium indicates starch breakdown.

Negative result: No zone of clearing around the bacterium indicates no starch breakdown."