Enzymes All enzymes are proteins Not all proteins

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 1 Active site is available for a molecule of substrate, the reactant on which the enzyme acts. Substrate (sucrose) 2 Substrate binds to enzyme. Glucose OH Enzyme (sucrase) H 2 O Fructose H O 4 Products are released. Figure 5. 16 3 Substrate is converted to products. 3

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 – 3 D 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) p. H – A change of p. H 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

p. H

Enzyme Concentration

Substrate Concentration