Energy and Living ThingsEnergy and Living Things

Section 5-1Section 5-1

Energy Flows Between Energy Flows Between Organisms in Living Organisms in Living

SystemsSystems Almost all energy in living systems Almost all energy in living systems

needed for metabolism comes from the needed for metabolism comes from the sun.sun.

Energy from the sun enters living systems Energy from the sun enters living systems when plants, algae, and certain bacteria when plants, algae, and certain bacteria absorb sunlight.absorb sunlight.

Some of the energy from the sun is Some of the energy from the sun is captured and used to make organic captured and used to make organic compounds.compounds.

Organic compounds store chemical Organic compounds store chemical energy and can serve as food for energy and can serve as food for organisms.organisms.

Building Molecules that Building Molecules that Store Chemical EnergyStore Chemical Energy

Metabolism involves either using energy to Metabolism involves either using energy to build molecules or breaking down build molecules or breaking down molecules in which energy is stored.molecules in which energy is stored.

PhotosynthesisPhotosynthesis – process by which light – process by which light energy is converted to chemical energy energy is converted to chemical energy

AutotrophsAutotrophs – organisms that use energy – organisms that use energy from sunlight or inorganic substances to from sunlight or inorganic substances to make organic compounds (food).make organic compounds (food).

Building Molecules that Building Molecules that Store Chemical Energy Store Chemical Energy

(con’t)(con’t) Most autotrophs are photosyntheticMost autotrophs are photosynthetic Some autotrophs use chemical energy Some autotrophs use chemical energy

from inorganic substances to make from inorganic substances to make organic compoundsorganic compounds

Breaking Down Food for Breaking Down Food for EnergyEnergy

Chemical energy in organic Chemical energy in organic compounds can be transferred to compounds can be transferred to other organic compounds or to other organic compounds or to organisms that consume food.organisms that consume food.

HeterotrophsHeterotrophs – organisms that must – organisms that must get energy from food instead of get energy from food instead of directly from sunlight or inorganic directly from sunlight or inorganic substances.substances.ExampleExample: humans, animals – get : humans, animals – get energy from food through process of energy from food through process of cellular respirationcellular respiration

Cellular RespirationCellular Respiration

Metabolic process similar to burning Metabolic process similar to burning fuel.fuel.

Releases much of the energy found Releases much of the energy found in food to make ATP.in food to make ATP.

Cells transfer energy from Cells transfer energy from food to ATPfood to ATP

Chemical energy that is stored in food Chemical energy that is stored in food molecules is released gradually in a series molecules is released gradually in a series of enzyme-assisted chemical reactions.of enzyme-assisted chemical reactions.

When cells break down food molecules, When cells break down food molecules, some of the energy is released as heat. some of the energy is released as heat. Much of the remaining energy is stored Much of the remaining energy is stored temporarily in molecules of ATP.temporarily in molecules of ATP.

ATP – the energy currency inside cells. ATP – the energy currency inside cells. Delivers energy where needed.Delivers energy where needed.

Cells transfer energy from Cells transfer energy from food to ATP (con’t)food to ATP (con’t)

The energy released from ATP can be The energy released from ATP can be used to power other chemical used to power other chemical reactions.reactions.

Most chemical reactions require less Most chemical reactions require less energy than is released from ATP, so energy than is released from ATP, so enough energy is released from ATP enough energy is released from ATP to drive most of a cell’s activities.to drive most of a cell’s activities.

ATP Stores and Releases ATP Stores and Releases EnergyEnergy

ATP is a nucleotide with two phosphate ATP is a nucleotide with two phosphate groups.groups.

The phosphate groups store energy.The phosphate groups store energy. The “phosphate tail” of ATP is unstable The “phosphate tail” of ATP is unstable

because the phosphate groups are because the phosphate groups are negatively charged and repel one negatively charged and repel one another. The phosphate groups store another. The phosphate groups store energy like a spring that is compressed. energy like a spring that is compressed. The energy is released when the bonds The energy is released when the bonds that hold the phosphate groups together that hold the phosphate groups together are broken.are broken.

Cells transfer energy from Cells transfer energy from food to ATP (con’t)food to ATP (con’t)

Breaking the outer phosphate bond Breaking the outer phosphate bond requires input of energy, but much requires input of energy, but much more energy is released during the more energy is released during the reaction.reaction.

ATP minus 1 phosphate (POATP minus 1 phosphate (PO44) group ) group is ADPis ADP

ATP ATP → ADP + P + energy→ ADP + P + energy The cell can readily use the energy The cell can readily use the energy

released from this reaction.released from this reaction.

Cells transfer energy from Cells transfer energy from food to ATP (con’t)food to ATP (con’t)

The energy released from this The energy released from this reaction is used to power reaction is used to power metabolism.metabolism.

In some reactions, two phosphates In some reactions, two phosphates are cleaved and AMP is made.are cleaved and AMP is made.