Digestive Enzymes Table
Biochemical Catalysts. Substrates, Products, and Optimal Conditions.
Mouth
Salivary Amylase (Ptyalin)
Starts carbohydrate digestion. Breaks down starch into simpler sugars.
Stomach
Pepsin
Secreted as inactive Pepsinogen. Activated by HCl. Breaks peptide bonds.
Renin
Curdles milk to optimize digestion in infants. Absent/Low in adults.
Small Intestine
Pancreatic Amylase
Completes the digestion of carbohydrates that escaped saliva.
Trypsin
Secreted as Trypsinogen by Pancreas. Activated in intestine.
Lipase
Primary fat-digesting enzyme. Works on fats emulsified by bile.
Maltase
Final step of starch digestion.
Sucrase
Digests table sugar finding in sweets and fruits.
Lactase
Breaks down milk sugar. Deficiency causes Lactose Intolerance.
Peptidases (Erepsin)
Final step of protein digestion releasing absorbable amino acids.
Understanding Biological Catalysts
Enzymes are protein molecules that speed up chemical reactions in the body without getting used up. They are vital for breaking down food into nutrients your body can absorb.
The Lock & Key Mechanism
Specific Shape
The Enzyme (Lock) has a unique active site shape.
Perfect Fit
Only the correct Substrate (Key) combines to form a complex.
Reaction
Reaction occurs, product is released, enzyme remains unchanged.
Factors Affecting Activity
Temperature
Optimum is 37°C (Body Temp).
Low Temp = Inactive.
High Temp (>50°C) = Denatured (Permanently destroyed).
pH Level
Each enzyme has a specific pH.
Stomach: Acidic (pH 2) for Pepsin.
Intestine: Alkaline (pH 8) for Trypsin.
Frequently Asked Questions
What is the Lock and Key hypothesis?
The Lock and Key hypothesis explains enzyme specificity. The enzyme (Lock) has a specifically shaped active site that only accepts a specific substrate (Key). If the shape doesn't match, the reaction won't happen.
Why does Pepsin need an acidic environment?
Pepsin is a protease that works in the stomach. The presence of Hydrochloric Acid (HCl) creates a low pH (1.5-2.0), which activates Pepsinogen into Pepsin and optimizes its shape to digest proteins.
What happens to enzymes at high temperatures?
At high temperatures (usually above 40-50°C), enzymes get denatured. This means their protein structure unravels, the shape of the active site changes, and they can no longer bind to substrates.
Which enzyme starts digestion in the mouth?
Salivary Amylase (also known as Ptyalin) starts chemical digestion in the mouth by breaking down complex starch into simpler maltose sugar.
What are cofactors?
Cofactors are non-protein "helpers" required by some enzymes to function. They can be metal ions (like Zinc or Calcium) or organic molecules (coenzymes like vitamins).
Why doesn't the stomach digest itself?
The stomach wall is lined with a thick layer of mucus that protects the cells from the corrosive acid and the protein-digesting enzyme Pepsin.
Difference between Pepsin and Trypsin?
Both digest proteins, but Pepsin works in the acidic stomach, while Trypsin works in the alkaline small intestine. Trypsin continues the work started by Pepsin.
What is emulsification?
Emulsification is the physical breakdown of large fat globules into tiny droplets by Bile Salts. This increases the surface area for the enzyme Lipase to work effectively.
Where is Bile produced and stored?
Bile is produced by the Liver and stored in the Gallbladder. It is released into the small intestine to aid fat digestion.
What is the end product of protein digestion?
Proteins are broken down into Amino Acids, which are then absorbed into the bloodstream to build body tissues.