Enzymes B11

1
Enzymes B11

• Reference chapter 5 of your text
• Quiz Wed March 31
• Test Thurs April 1st
• Very short unit, builds on what you already know
• Pay close attention to the study guide you were
  given (with answer key)

2
Metabolic Reactions and Energy Transformations

• Metabolism is the sum of all the chemical
  reactions that occur in a cell.
• A B C D
• (reactants) (products)

3
6.2 Metabolic Reactions and Energy
Transformations

• ATP Energy for Cells
• ATP stands for adenosine triphosphate, the common
  energy currency for cells.
• ATP is generated from ADP (adenosine diphosphate)
  an inorganic phosphate molecule ( P )

4
The ATP Cycle
5
Metabolic Reactions and Energy Transformations

• Structure of ATP
• ATP is a nucleotide that is composed of
• Adenine (a nitrogen-containing base)
• Ribose (a 5-carbon sugar)
• Three phosphate groups

6
Metabolic Reactions and Energy Transformations

• Structure of ATP
• ATP is a high energy compound because a
  phosphate group can easily be removed.

7
Metabolic Reactions and Energy Transformations

• Coupled Reactions
• The energy released by an exergonic reaction is
  used to drive an endergonic reaction.
• Exergonic releases energy, endergonic needs
  energy put in

8
Coupled Reactions
9
Metabolic Pathways and Enzymes

• Metabolic pathways are a series of linked
  reactions.
• These begin with a specific reactant and produce
  an end product

10
Metabolic Pathways and Enzymes

• Enzymes are usually proteins that function to
  speed a chemical reaction.
• Enzymes serve as catalysts

11
A Metabolic Pathway
12
Metabolic Pathways and Enzymes

• The Energy of Activation (Ea) is the energy that
  must be added to cause molecules to react with
  one another.

13
Energy of Activation
14
Metabolic Pathways and Enzymes

• How Enzymes Function
• Enzyme binds substrate to form a complex
• E S ? ES ? E P

15
Enzymatic Action
16
Metabolic Pathways and Enzymes

• How Enzymes Function
• Enzyme binds substrate to form a complex
• E S ? ES ? E P
• Induced fit model
• Substrate and active site shapes dont match
  exactly
• Active site is induced to undergo a slight change
  in shape to accommodate substrate binding

17
Induced Fit Model
18
Metabolic Pathways and Enzymes

• Factors Affecting Enzymatic Speed
• Substrate Concentration
• Temperature and pH
• Enzyme Activation
• Enzyme Inhibition
• Enzyme Cofactors

19
Metabolic Pathways and Enzymes

• Substrate Concentration
• Enzyme activity increases as substrate
  concentration increases because there are more
  collisions between substrate and enzyme
• Maximum rate is achieved when all active sites of
  an enzyme are filled continuously with substrate

20
Metabolic Pathways and Enzymes

• Temperature
• Enzyme activity increase as temperature rises
• Higher temperatures cause more effective
  collisions between enzymes and substrates
• High temperatures may denature an enzyme,
  inhibiting its ability to bind to substrates

21
The Effect of Temperature on the Rate of Reaction
22
Metabolic Pathways and Enzymes

• pH
• Each enzyme has an optimal pH
• Enzyme structure is pH dependent
• Extremes of pH can denature an enzyme by altering
  its structure

23
Effect of pH on the Rate of Reaction
24
Metabolic Pathways and Enzymes

• Enzyme Activation
• Cell regulates metabolism by regulating which
  enzymes are active
• Genes producing enzymes can be turned on or off
  to regulate enzyme concentration
• In some cases a signaling molecule is used to
  activate an enzyme

25
Metabolic Pathways and Enzymes

• Enzyme Inhibition
• Occurs when enzyme cannot bind its substrate
• Activity of cell enzymes is regulated by feedback
  inhibition
• Ex when product is abundant it binds to the
  enzymes active site and blocks further
  production
• When product is used up, it is removed from the
  active site
• In a more complex type of inhibition, product
  binds to a site other than the active site, which
  changes the shape of the active site
• Poisons are often enzyme inhibitors

26
Feedback Inhibition
27
Metabolic Pathways and Enzymes

• Enzyme Cofactors
• Molecules which help enzyme function
• Copper and zinc are examples of inorganic
  cofactors
• Organic non-protein cofactors are called
  coenzymes
• Vitamins are often components of coenzymes