Enzymes All enzymes are proteins. Not all proteins are enzymes. Enzymes are catalysts. A catalyst is a substance which increases the rate of chemical reaction – Catalysts themselves are NOT used up

What are Enzymes used for? 1)Used in industrial processes to reduce heat or pressure requirements 2)Used in living organisms – Reactions must occur at body temp and atmospheric pressure (LOW)‏ Why are enzymes important? Without catalysts reactions would be too slow Needed to sustain life

Enzymes – Are a type of protein that acts as a catalyst, speeding up chemical reactions 3 Substrate (sucrose) Enzyme (sucrase) Glucose OH H O H2OH2O Fructose 3 Substrate is converted to products. 1 Active site is available for a molecule of substrate, the reactant on which the enzyme acts. Substrate binds to enzyme Products are released. Figure 5.16

How enzymes work Enzymes act upon a substance called its substrate Each reaction requires a specific enzyme Enzymes must be made of something that can take many different shapes Proteins and their 4 levels of structure work well There is a small part of the enzyme that contacts the substrate called the active site – Like a small cleft or indent on the surface Substrate fits into active site and interacts with exposed amino acids by ionic or hydrogen bonding – Forms enzyme-substrate complex – Reaction then occurs

How enzymes work Proteins and their 4 levels of structure work well There is a small part of the enzyme that contacts the substrate called the active site – Like a small cleft or indent on the surface Substrate fits into active site and interacts with exposed amino acids by ionic or hydrogen bonding – Forms enzyme-substrate complex – Reaction then occurs

How enzymes work All reactions begin by breaking bonds which requires an activation energy to start Enzymes work by lowering the activation energy – This is done by the enzyme-substrate complex – This complex has lower activation energy – Makes the reaction proceed quicker and easier Without enzyme activation is too high to occur

Factors that affect How Enzymes Work 1)Temperature – Increase temperature --> Increase kinetic energy or movement of molecules – More collisions between substrate and enzyme – Moving higher than optimum temp reduces activity Enzyme is made of protein High temperatures can denature the enzyme – Tertiary structure is changed – 3D structure of enzyme changes too much for substrate to fit – Most enzymes in the human body have an optimum temperature around 40 C

Enzyme Activity Factors 2) pH – A change of pH means a change in H+ ions in the surrounding – Affects the bonding of R-groups – Affects the shape of the enzyme – Most human enzymes have optimum at 7 (neutral)‏ – Stomach enzymes (pepsin) have optimum at 2 – Liver enzymes arginase has optimum at 10

Enzyme Activity Factors 3) Enzyme concentration – Enzymes are not used up during reactions – Can work effectively at low concentrations – Usually substrate molecules are in excess – Reaction rate is limited by enzyme concentration – Increased concentration --> increased reaction rate

Enzyme Activity Factors 4) Substrate concentration – If substrate concentration is low some enzyme sites empty – Rate of reaction will be lower – If substrate conc. is then increased --> rate increases – This increase continues until substrate is in excess

Energy Changes

Temperature

pH

Enzyme Concentration

Substrate Concentration