Energy and Chemical Reactions Thesis


Chapter 6

Lecture Outline

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Chapter 6

An Introduction to Energy, Enzymes, and Metabolism

Key Concepts:

• Energy and Chemical Reactions

• Enzymes and Ribozymes

• Overview of Metabolism

• Recycling of Organic Molecules



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Energy and Chemical Reactions

• Energy = ability to promote change or do work

• Two forms

Kinetic Energy – associated with movement

Potential Energy – due to structure or location

• Chemical energy, the energy in molecular bonds, is a form of potential energy



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Figure 6.1

a) Kinetic energy b) Potential energy

a: ©moodboard/Corbis; b: ©amanaimages/Corbis



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Table 6.1

Table 6.1 Types of Energy That Are Important in Biology

Energy type Description Biological example

Light Light is a form of electromagnetic radiation that is visible to the eye. The energy of light is packaged in photons.

During photosynthesis, light energy is captured by pigments in chloroplasts (described in Chapter 8). Ultimately, this energy is used to produce organic molecules.

Heat Heat is the transfer of kinetic energy from one object to another or from an energy source to an object. In biology, heat is often viewed as kinetic energy that can be transferred due to a difference in temperature between two objects or locations.

Many organisms, including humans, maintain their bodies at a constant temperature. This is achieved, in part, by chemical reactions that generate heat.

Mechanical Mechanical energy is the energy possessed by an object due to its motion or its position relative to other objects.

In animals, mechanical energy is associated with movement due to muscle contraction, such as walking.

Chemical potential Chemical potential energy is potential energy stored in the electrons of molecules. When bonds are broken and rearranged, energy may be released.

The covalent bonds in organic molecules, such as glucose and ATP, store large amounts of energy. When bonds are broken in larger molecules to form smaller molecules, the energy that is released can be used to drive cellular processes.

Electrical/ion gradient The movement of charge or the separation of charges can provide energy. Also, a difference in ion concentration across a membrane constitutes an electrochemical gradient, which is a source of potential energy.

During a stage of cellular respiration called oxidative phosphorylation (described in Chapter

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