The human digestive system Flashcards – AQA GCSE Biology - Foundation (8461)

Where is bile made, stored and released?

Made in the liver, stored in the gall bladder and released into the small intestine.

How does bile provide conditions that increase lipase activity?

Alkaline bile neutralises hydrochloric acid from the stomach, providing alkaline conditions.

What does it mean for bile to emulsify fat?

It breaks fat into small droplets.

Why does emulsification increase the rate of fat breakdown?

It increases the surface area available to lipase.

Is bile an enzyme?

No, bile is not an enzyme.

What is the word equation for lipid digestion by lipase?

Lipid → glycerol + fatty acids

Which two organs produce lipase?

The pancreas and small intestine.

Where does lipase act during digestion?

In the small intestine.

Why can the products of lipid digestion be absorbed?

They are small molecules.

What happens to food molecules during chemical digestion?

Large, insoluble food molecules are broken down into small, soluble molecules.

Why is chemical digestion necessary for absorption?

It produces molecules that can be absorbed from the digestive system.

What is an enzyme?

A biological catalyst, usually a protein, that speeds up chemical reactions without being used up.

What happens when a substrate binds to an enzyme?

It binds to the active site and is converted into product or products. The products leave, and the enzyme can be used again.

How does the lock and key model explain enzyme specificity?

A substrate fits an enzyme’s active site because their shapes are complementary. This helps explain why an enzyme catalyses a specific reaction.

What is metabolism?

The sum of the chemical reactions in an organism.

What types of metabolic reactions do enzymes catalyse?

Reactions that build up and break down molecules.

What does amylase break down, and what does it produce?

It breaks down starch into simple reducing sugars.

Where do the salivary glands secrete amylase?

Into the mouth, where it acts on starch in food.

Where does the pancreas secrete amylase?

Into the small intestine, where it continues starch digestion.