proteins and enzymes. thermodynamics the study of energy in living systems
TRANSCRIPT
Proteins and Enzymes
Thermodynamics
The study of energy in living systems
Two laws of thermodynamics
• 1st law of thermodynamics: conservation of energy. Energy is neither lost nor gained but just changes from one form to another.
• 2nd law of thermodynamics: entropy– Tendency to move from order to disorder.
Conservation of energy
• Energy can neither be created nor destroyed.
• Energy can only be changed from one form to another.
Entropy: disorder
• For living beings or just molecules to be organized, a lot of energy is required.
• Very little energy is needed to create disorder.
A B + C
• Breaking down a reactant (A) into products (B and C)
• Requires little energy to start breaking down substances
• Exergonic reaction – releases energy
A + B C
• Making a product (C) from reactants (A and B)
• Requires much energy to start this reaction – Why?
• Endergonic reaction – absorbs energy
Energy graphs
Activation energy
• Activation energy: how much energy is required to start a reaction
• http://www.youtube.com/watch?v=-vgkvUxxZFg&feature=related
• http://www.britishpathe.com/record.php?id=50144
Activation energy on two types of reactions
Energy-Absorbing Reaction Energy-Releasing Reaction
Products
Products
Activation energy
Activation energy
Reactants
Reactants
Graph of Energy of a reaction
Which graph is Endergonic?
Which graph is Exergonic?
Enzyme action
• Enzymes: special proteins that help to reduce the activation energy (Ea)
• What will enzymes do to the speed (rate) of a reaction?
Effects of Enzymes
Reaction pathwaywithout enzyme Activation energy
without enzyme
Activationenergywith enzymeReaction pathway
with enzyme
Reactants
Products
• How do enzymes help with the activation energy required for metabolic processes?
DNA
Polypeptide= protein
Amino acids
Enzymes are Proteins (made of amino acids)
• Remember, All enzymes are Proteins
Glucose
Substrates
ATP
Substratesbind toenzyme
Substratesare convertedinto products
Enzyme-substratecomplex
Enzyme(hexokinase)
ADPProducts
Glucose-6-phosphate
Productsare released
Section 2-4
Figure 2-21 Enzyme Action
Active site
Enzyme activity (1)
Glucose
Substrates
ATP
Substratesbind toenzyme
Substratesare convertedinto products
Enzyme-substratecomplex
Enzyme(hexokinase)
ADPProducts
Glucose-6-phosphate
Productsare released
Section 2-4
Figure 2-21 Enzyme Action
Active site
Enzyme activity (2)
Glucose
Substrates
ATP
Substratesbind toenzyme
Substratesare convertedinto products
Enzyme-substratecomplex
Enzyme(hexokinase)
ADPProducts
Glucose-6-phosphate
Productsare released
Section 2-4
Figure 2-21 Enzyme Action
Active site
Enzyme activity (3)
Glucose
Substrates
ATP
Substratesbind toenzyme
Substratesare convertedinto products
Enzyme-substratecomplex
Enzyme(hexokinase)
ADPProducts
Glucose-6-phosphate
Productsare released
Section 2-4
Figure 2-21 Enzyme Action
Active site
Enzyme activity (4)
Proteins can be Denatured
• Denature – changes the Secondary, Tertiary or Quaternary structure of a protein.
• Heat and pH changes are the most common ways to denature a protein (polypeptide).
Enzymes and Metabolism
• Enzymes facilitate the metabolic processes (chemical reactions) to sustain life.
• Enzymes help to maintain homeostasis.
• Enzymes help to build cells.
• Enzymes help in reproduction.
Click on image to play video.