Biochemistry Chapter: Enzymes and Activation Energy

Study Notes

Activation Energy Analogy

Imagine climbing a hill. The hill represents the activation energy—the initial push needed to get moving. Without that push the ball (reactants) would just sit there. The energy required to get them started.

Enzyme Affect on Activation Energy

Enzymes lower the "activation energy" needed to start a reaction, like having a ramp to climb the hill making it easier.

Catalyst Definition

An enzyme is a catalyst because it speeds up a chemical reaction without being consumed in the process. It acts as a helper to the reaction.

Enzyme-Catalyzed Reaction Sketch

        +
       / \
      /   \  -- Substrate 1
     |     |   (reactant)     
   Enzyme    (catalyst)
     |     |
     |     |
     |     |  -- Substrate 2
   <---|----|--->     ---> Product (result)
       \ /
        |
       Active Site

Competitive and Non-Competitive Inhibitors Sketch

        +
       / \
      /   \  -- Substrate 1
     |     |    
   Enzyme    
     |     |
     |     |  -- Substrate 2
   <---|----|--->    ---> Product 
       \ /
        | <--- Competitive Inhibitor (blocks active site)
       Active Site

        +
       / \
      /   \  --Substrate 1
     |     |    
   Enzyme     
     |     |            
     |     |  -- Substrate 2
   <---|----|--->     ---> Product        
       \ /
        | <--- Non-Competitive Inhibitor (binds elsewhere, changing the shape)
       Active Site

Competitive inhibitors block the active site, whereas non-competitive inhibitors bind elsewhere, changing the enzyme's shape, and thus rendering it ineffective.

Lock-and-Key vs. Induced-Fit Models

The lock-and-key model suggests enzymes and substrates have precisely complementary shapes in order for the reaction to work. The induced fit model proposes that the enzyme changes shape slightly to fit the substrate, rather than having a perfectly complementary shape initially.

Enzyme Function & Energy Diagrams

Reaction Progress
        |
        |  -----With Enzyme----
        | /
        |/
       ___|_____
      |       |
      |   Peak - Activation energy|
      |       |
      |_______|
        |     ----Without Enzyme----
        |     /
        | ____|
        |    |
        |    |
        |   Peak - Activation energy|
        |____|

Enzymes speed up reactions by lowering the activation energy, making the reaction proceed faster.

Acidic and Basic Solutions

An "acidic" solution has a high concentration of hydrogen ions (H+), while a "basic" solution has a low concentration of hydrogen ions (H+). Opposite occurs for basic solutions.

Buffer Definition

A buffer is a substance that minimizes changes in pH by accepting or donating hydrogen ions (H+) when needed in a given solution.

Variables Affecting Enzyme Reaction Rate

Temperature: Increased temperatures generally increase reaction rates until the enzyme denatures.
pH: The optimal pH exists for each enzyme, where it works best, deviation from this results in decreased activity.
Substrate Concentration: Increasing substrate concentration increases the reaction rate up to a point where the enzymes are saturated.
Enzyme Concentration: Increasing enzyme concentration increases the reaction rate as more active sites are available.

Protein Denaturation

Denaturation is when a protein loses its structure (and therefore its function). This might happen when exposed to extreme temperatures, pH changes, or other damaging agents.

Cellular Respiration Purpose and Overall Equation

Cellular respiration's purpose is to convert chemical energy (stored in glucose) into usable energy (ATP).
Overall Reaction: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

Anaerobic vs. Aerobic Respiration

Anaerobic: No oxygen required. Occurs much faster but makes less ATP.
Aerobic: Oxygen required. Occurs slower but makes more ATP.

Mitochondria Structure and Function

Mitochondria are organelles with inner membrane folds (cristae), and an outer membrane and matrix.
- Often referred to as the "powerhouse" of the cell due to their role in ATP production (cellular respiration).

Yeast and Animal Fermentation

Yeast fermentation produces ethanol and carbon dioxide .
Animal fermentation produces lactic acid.

Photosynthesis Purpose and Overall Equation

Photosynthesis' purpose is to convert light energy into chemical energy stored in glucose.
Overall Reaction: 6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂

Light-Dependent vs. Light-Independent Reactions

Light-Dependent Reactions: Require light; happen in thylakoids; produce ATP, NADPH, and oxygen.
Light-Independent Reactions (Calvin Cycle): Don't require light; happen in the stroma; use ATP and NADPH to produce glucose.

Description

This quiz covers key concepts in biochemistry related to enzymes and activation energy. Explore how enzymes act as catalysts and their role in lowering activation energy. Understand the mechanisms of competitive and non-competitive inhibitors through illustrative sketches.

Biochemistry Chapter: Enzymes and Activation Energy

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Questions and Answers

What is the term for the energy required to start a chemical reaction?

An enzyme is a type of reaction product.

What does it mean if an enzyme is referred to as a 'catalyst'?

The process of converting glucose into energy in the absence of oxygen is called ______.

Match the following metabolic processes with their characteristics:

Which of the following correctly describes a competitive inhibitor?

Buffers help maintain pH stability in a solution.

The organelle referred to as the powerhouse of the cell is the ______.

What occurs during the light-dependent reactions of photosynthesis?

Acidic solutions have a pH level: