Clase

Lecture 4 2.4 Biomolecules Metabolic and Ecological Context
Book Chapters: 8, 27, 54 Campbell7 , 8, 27, 55 Campbell9

Overview: The Energy of Life
• • The living cell is a miniature chemical factory where thousands of reactions occur The cell extracts energy and applies energy to perform work

Concept 2.4.1: An organism’s metabolism transforms matter and energy, subject to the laws ofthermodynamics
• Metabolism is the totality of an organism’s chemical reactions • Metabolism is an emergent property of life that arises from interactions between molecules within the cell

Organization of the Chemistry of Life into Metabolic Pathways
• • A metabolic pathway begins with a specific molecule and ends with a product Each step is catalyzed by a specific enzyme
Enzyme 1 A Reaction 1Starting molecule B Reaction 2 Enzyme 2 C Reaction 3 Product Enzyme 3 D

• • •

Catabolic pathways release energy by breaking down complex molecules into simpler compounds Anabolic pathways consume energy to build complex molecules from simpler ones Bioenergetics is the study of how organisms manage their energy resources

Forms of Energy
• Energy is the capacity to cause change • Energyexists in various forms, some of which can perform work (e.g. kinetic enegy, potential energy, …) • Chemical energy is potential energy available for release in a chemical reaction • Energy can be converted from one form to another

The Laws of Energy Transformation
• • • • Thermodynamics is the study of energy transformations A closed system, such as that approximated by liquid in a thermos,is isolated from its surroundings In an open system, energy and matter can be transferred between the system and its surroundings Organisms are open systems

The First Law of Thermodynamics
• According to the first law of thermodynamics, the energy of the universe is constant – – • Energy can be transferred and transformed Energy cannot be created or destroyed

The first law is also called theprinciple of conservation of energy

The Second Law of Thermodynamics
• • During every energy transfer or transformation, some energy is unusable, often lost as heat According to the second law of thermodynamics, every energy transfer or transformation increases the entropy (disorder) of the universe

Chemical energy

Heat

CO2 H2O

First law of thermodynamics

Second law ofthermodynamics

• • •

Living cells unavoidably convert organized forms of energy to heat Spontaneous processes occur without energy input; they can happen quickly or slowly For a process to occur without energy input, it must increase the entropy of the universe

Biological Order and Disorder
• • • • Cells create ordered structures from less ordered materials Organisms also replace ordered formsof matter and energy with less ordered forms The evolution of more complex organisms does not violate the second law of thermodynamics Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases

Overview: Life Is Work
• Living cells require energy from outside sources • Energy flows into an ecosystem as sunlight and leaves as heat • Photosynthesis generatesoxygen and organic molecules, which are used in cellular respiration • Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work

LE 9-2 Light energy ECOSYSTEM

CO2 + H2O

Photosynthesis in chloroplasts Cellular respiration in mitochondria

Organic + O molecules 2

ATP powers most cellular work Heat energy

Concept 2.4.2: A great diversity of nutritionaland metabolic adaptations have evolved in prokaryotes
• All four models of nutrition are found among prokaryotes: Photoautotrophy, Chemoautotrophy, Photoheterotrophy, Chemoheterotrophy

Metabolic Relationships to Oxygen
• Prokaryotic metabolism varies with respect to oxygen: – – – Obligate aerobes require oxygen Facultative anaerobes can survive with or without oxygen Obligate anaerobes...