enzymes and digestion

What is a tissue?

A group of cells with similar structure and function working together.

What is an organ?

An aggregation of tissues performing specific functions.

What is an organ system?

A group of organs working together to perform a specific body function.

What is an enzyme?

A biological catalyst made of protein that speeds up chemical reactions in living organisms without being used up itself.

What is an active site?

The specific region on an enzyme where the substrate binds to undergo a chemical reaction.

Explain the lock and key model of enzyme action?

The active site has a specific 3D shape complementary to a specific substrate; they fit together like a lock and key to form an enzyme-substrate complex.

What happens when an enzyme denatures?

High temperatures or extreme pH break bonds in the protein structure, altering the shape of the active site so the substrate can no longer fit.

How does temperature affect enzyme activity?

Every enzyme has an optimum temperature. Increasing temperature up to the optimum increases the rate (more kinetic energy, more collisions). Above the optimum, bonds break and the enzyme denatures, so the rate drops rapidly.

How does pH affect enzyme activity?

Every enzyme has an optimum pH. Moving above or below alters charges and breaks bonds in the active site, causing denaturation.

What is the function of digestive enzymes?

To break down large, insoluble food molecules into small, soluble molecules so they can be absorbed into the bloodstream.

What are the main organs of the digestive system and their specific roles?

1. Mouth/Salivary Glands: Chews food and secretes amylase. 2. Oesophagus: Transports food to stomach via peristalsis. 3. Stomach: Churns food, secretes HCl (kills bacteria) and protease (pepsin). 4. Liver/Gallbladder: Produces and stores bile. 5. Pancreas: Secretes amylase, protease, and lipase. 6. Small Intestine: Produces enzymes, digests food, and absorbs soluble nutrients into blood. 7. Large Intestine: Absorbs water to form faeces.

Where is amylase produced and what does it do?

Produced in salivary glands, pancreas, small intestine. Breaks down starch into simple sugars (specifically maltose).

Where are proteases produced and what do they do?

Produced in stomach (pepsin), pancreas, small intestine. Break down proteins into amino acids.

Where are lipases produced and what do they do?

Produced in pancreas and small intestine. Break down lipids (fats) into fatty acids and glycerol.

Where is bile produced, stored, and what are its two main functions?

Produced in liver, stored in gallbladder. 1. Neutralises stomach acid (HCl) in small intestine to create optimal alkaline pH for enzymes. 2. Emulsifies fats (breaks large droplets into smaller ones to increase surface area for lipase).

What are the products of digestion used for?

Some glucose is used in respiration to release energy. The products are absorbed into the blood and used to build new carbohydrates, lipids, and proteins.

What is the test for starch?

Add Iodine solution. Positive result: colour change from orange-brown to blue-black.

What is the test for reducing sugars (glucose)?

Add Benedict's reagent and heat in a water bath at approximately 75°C for 5 minutes. Positive result: colour change from blue to green, yellow, or brick-red precipitate.

What is the test for proteins?

Add Biuret reagent. Positive result: colour change from blue to purple/lilac.

What is the test for lipids (fats)?

Add ethanol, shake, pour into water. Positive result: cloudy white emulsion forms.

What do carbohydrases do?

Break down carbohydrates to simple sugars. Amylase is a carbohydrase which breaks down starch.