Chemical Reactions in Cells The molecule you start with is called the SUBSTRATE (also known as the reactant). The molecule you end up with is called the PRODUCT. SUBSTRATE PRODUCT

Chemical Reactions in Cells Glycogen Glucose + Glucose + Glucose Amino Acid + Amino AcidProtein Substrate Products Substrates Product

Enzymes – Made of PROTEIN Enzymes are : catalysts in living organisms A catalyst is a molecule which speeds up chemical reactions. SubstrateProducts Enzyme makes it happen more q qq quickly Enzyme Shoulder partner examples

In order to speed up reactions, the substrate must fit PERFECTLY into a place on the enzyme known as the ACTIVE SITE. The active site and substrate fit together like a lock and a key.

Products The enzymes bind the substrates, and force them into a position which makes it easier for bonds to be broken so they can be converted into products.

Enzyme activity can be affected by several factors

Enzymes are proteins Each protein has its own unique shape that is perfect for its function. Protein structure is very delicate.

Protein structure can be: Denatured (destroyed) by high temperatures Denatured by changes in pH When an enzyme is denatured, the shape of its active site is changed, so the active site (lock) no longer matches the substrate (key).

Effect of temperature on enzyme activity Low temp. – molecules move slowly As temperature increases to optimum temperature, molecules move faster and reaction rate increases At very high temp. – enzyme structure is denatured

Effect of pH on enzyme activity Enzymes have an optimum pH, which is the pH at which they work best At other pH’s, enzymes are denatured

Competitive inhibitors of enzymes Competitive inhibitor competes with the substrate for the active site. Therefore, the substrate is sometimes prevented from binding to active site.

Many chemical reactions occur in living organisms Examples: Break down starch into many glucose molecules Link amino acids together to build proteins

Effect of competitive inhibitors on enzyme activity Normal activity Increasing substrate concentration →

Effect of amount of substrate on enzyme activity concentration Increasing substrate 

Effect of amount of enzyme on enzyme activity Increasing enzyme concentration →

Essential points to understand Enzyme activity is affected by: Temperature pH Substrate concentration Enzyme concentration Competitive inhibitors