Chapter4 Energy of Life
Chapter Overview
Energy of Life: Focus on the role of energy in cellular processes and metabolism.
Membrane Structure and Function
Eukaryotic Cells: Compartmentalized by membranes, which function as fluid mosaics.
Chemical Reactions: Membranes provide organized sites where enzymes facilitate energy reactions.
Defining Energy
Energy: Capacity to cause change or do work.
Importance: All organisms require energy for survival; it's essential for chemical reactions and growth.
Energy in Action
Examples of Energy Use:
Boiling water with energy from peanuts.
Usain Bolt used over 100 million energy molecules for speed.
Energy Efficiency in Systems
Automotive Example: Cars lose about 75% of energy as heat.
Human Metabolism: Consuming energy from food (e.g., running after a pizza).
Types of Energy
Kinetic Energy: Energy of motion.
Potential Energy: Stored energy related to position or structure.
Thermal and Light Energy: Forms of energy reflecting movement and radiation.
Energy Cycles in Living Systems
Energy transitions between kinetic and potential forms.
Continuous conversion is crucial for maintaining life processes.
Thermodynamics and Energy Conversion Laws
First Law: Energy can be transformed but not created or destroyed.
Second Law: Energy conversions are inefficient; increase in entropy with energy loss as heat.
Energy Conversion Processes
Automobiles vs. Cells: Similar processes in energy conversion using fuel combustion (gasoline) and cellular respiration (glucose).
Automobile Energy Flow: Chemical (gasoline) -> Kinetic (movement) + Waste (CO2, water).
Cellular Respiration: Food -> Energy for cellular work + Waste (CO2, water).
ATP: The Energy Currency
Composition: Adenosine + 3 phosphate groups.
Functionality: ATP breaks down to ADP for energy release; essential for cellular tasks.
Energies chemical reactions through phosphate transfer.
Metabolism and Enzymatic Reactions
Metabolism: All chemical reactions in cells, dependent on enzymes for efficiency.
Enzymatic Control: Enzymes are produced or not based on the need to turn reactions on or off.
Activation Energy (EA)
Energy Barrier: Reactants must absorb energy (EA) to initiate chemical reactions.
Role of Enzymes: Lower EA, increasing reaction rate and cellular control.
Characteristics of Enzymes
Highly selective, functioning like a lock-and-key mechanism.
Operate only when the enzyme and substrate are present; enzymes can be reused.
Enzyme Inhibition
Competitive Inhibitors: Fill the active site, preventing substrate binding.
Noncompetitive Inhibitors: Alter enzyme structure by binding elsewhere.
Negative Feedback: End products inhibiting enzyme function.
Environmental Factors Affecting Enzymes
Influences include temperature, salt concentration, and pH; extremes can denature enzymes.
Membrane Transport Mechanisms
Passive Transport: Molecules move across membranes without energy (diffusion and osmosis).
Osmosis Types:
Hypotonic, Hypertonic, and Isotonic solutions affect cell water balance.
Active Transport: Requires energy to move substances against concentration gradients.
Bulk Transport Mechanisms
Exocytosis: Export of substances from cells.
Endocytosis: Import of substances into cells through cell membrane engulfing.
Types: Phagocytosis (cell eating), Pinocytosis (cell drinking), and Receptor-mediated endocytosis.
Cellular Communication
Signal Molecules: External signals can alter cell surface protein structures, triggering internal responses.
Signal Transduction Pathway: Relay signals for cellular response.
Understanding Food Energy
Calorie Definition: Energy required to raise temperature of 1 gram of water by 1 degree Celsius.
Food Calories Measurement: Listed in kilocalories (1 kcal = 1000 cal), impacting daily energy expenditure.