Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy in Living Systems Directly or indirectly, almost all of the.

Copyright © by Holt, Rinehart and Winston. All rights reserved.

ResourcesChapter menu

Energy in Living Systems• Directly or indirectly, almost all of the energy in living systems

needed for metabolism comes from the _______________.

Section 1 Energy and Living ThingsChapter 5



Energy in Living Systems, continued

Building Molecules That Store Energy

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

• Photosynthesis is the process by which ____________ energy is converted to chemical energy.

• Organisms that use energy from sunlight or from chemical bonds in inorganic substances to make organic compounds are called __________________________.





Breaking Down Food for Energy

• The chemical energy in organic compounds can be _____________________ to other organic compounds or to organisms that consume food.

• Organisms that must get energy from food instead of directly from sunlight or inorganic substances are called ________________________________.

• Cellular respiration is a metabolic process similar to burning _________________.





Transfer of Energy to ATP

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

• Like money, ATP is a portable form of energy “currency” inside cells. ATP delivers ____________________ wherever energy is needed in a cell.




ATP

• ATP (adenosine triphosphate) is a nucleotide with two extra energy-storing ____________________ groups.

• Energy is released when the bonds that hold the phosphate groups together are _______________.

• The removal of a phosphate group from ATP produces adenosine diphosphate, or ADP:

H2O + ATP ADP + P + energy




Using the Energy in Sunlight

The Stages of Photosynthesis

• Stage 1 Energy is captured from _______________.

• Stage 2 Light energy is converted to chemical energy, which is temporarily ___________________ in ATP and the energy carrier molecule NADPH.

• Stage 3 The chemical energy stored in ATP and NADPH powers the formation of ________________ compounds, using carbon dioxide, CO2.

Section 2 PhotosynthesisChapter 5



Using the Energy in Sunlight

The Stages of Photosynthesis

• Photosynthesis can be summarized by the following ___________________________________:

6CO2 + 6H2O C6H12O6 + 6O2

Carbon dioxide water sugars oxygen gas




Stage One: Absorption of Light Energy

• Sunlight contains a mixture of all the __________________ (colors) of visible light. When sunlight passes through a prism, the prism separates the light into different colors.




Stage One: Absorption of Light Energy, continuedPigments

• How does a human eye or a leaf absorb light? These structures contain light-absorbing substances called ______________________________.

• Chlorophyll the primary pigment involved in photosynthesis, absorbs mostly blue and red light and reflects _______________________ and yellow light.

• Plants contain two types of chlorophyll, chlorophyll a and chlorophyll b.




Stage One: Absorption of Light Energy, continuedPigments

• The pigments that produce yellow and orange fall leaf colors, as well as the colors of many fruits, vegetables, and flowers, are called _________________________________.

• Carotenoids absorb wavelengths of light different from those absorbed by chlorophyll, so having ____________ pigments enables plants to absorb more light energy during photosynthesis.




Stage One: Absorption of Light Energy, continued

Production of Oxygen

• Clusters of pigments are embedded in the membranes of disk-shaped structures called _____________________.

• When light strikes a thylakoid in a chloroplast, energy is transferred to electrons in _______________________.

• This energy transfer causes the electrons to jump to a higher energy level. This is how plants first capture energy from sunlight.




Stage One: Absorption of Light Energy, continued

Production of Oxygen

• The excited electrons that leave chlorophyll molecules must be replaced by other electrons.

• Plants get these replacement electrons from ___________ molecules, which are split by thylakoid.

• The oxygen atoms, O, from the _________________ water molecules combine to form oxygen gas, O2.




Stage Two: Conversion of Light Energy

• Excited electrons that leave chlorophyll molecules are used to produce new molecules that temporarily store chemical _________________.

• First an excited electron jumps to a nearby molecule in the thylakoid membrane. Then the electron is _____________ through a series of molecules along the thylakoid membrane.

• The series of molecules through which excited electrons are passed along a thylakoid membrane are called electron transport _______________________.




Stage Two: Conversion of Light Energy, continuedElectron Transport Chains

• While one electron transport chain provides energy used to make ATP, a second electron transport chain provides energy used to make __________________.

• NADPH is an electron _______________ that provides the high-energy electrons needed to make carbon-hydrogen bonds in the third stage of photosynthesis.

• In this second chain, excited electrons combine with _______________ ions as well as an electron acceptor called NADP+, forming NADPH.




Stage Three: Storage of Energy

• In the third (final) stage of photosynthesis, carbon atoms from __________ ______________ in the atmosphere are used to make organic compounds in which chemical energy is stored.

• The transfer of carbon dioxide to organic compounds is called carbon dioxide fixation.




Stage Three: Storage of Energy, continuedCalvin Cycle

• The Calvin cycle is a series of enzyme-assisted chemical reactions that produces a three-carbon _____________:

Step 1 Each molecule of carbon dioxide is added to a five-carbon compound by an enzyme.

Step 2 The resulting compound splits into two three-carbon compounds. ___________________________ groups and electrons are added to the compounds.

Step 3 ____________ of the resulting three-carbon sugars is used to make organic energy-storing compounds.


Step 4 The other three-carbon sugars are used to _______________________________ the initial five-carbon compound, thereby completing the cycle.



Stage Three: Storage of Energy, continued

Factors that Affect Photosynthesis

• Photosynthesis is directly affected by various environmental factors.

• In general, the rate of photosynthesis increases as light _________________ increases until all the pigments are being used.

• Photosynthesis is most efficient within a certain range of _____________________________.




Cellular Energy

• Oxygen in the air you breathe makes the production of ATP more _____________________, although some ATP is made without oxygen.

• Metabolic processes that require oxygen are called ______________________________.

• Metabolic processes that do not require oxygen are called _________________________________, which means “without air.

Section 3 Cellular RespirationChapter 5



Cellular Energy, continued

The Stages of Cellular Respiration

• Cellular respiration is the process cells use to harvest the energy in organic compounds, particularly ________________________________. The breakdown of glucose during cellular respiration can be summarized by the following equation:

C6H12O6 + 6O2 6CO2 + 6H2O + energyglucose oxygen gas carbon dioxide water ATP




Cellular Energy, continued

The Stages of Cellular Respiration

• Cellular respiration occurs in two stages:

Stage 1 Glucose is converted to _______________, producing a small amount of ATP and NADH.

Stage 2 When oxygen is present, pyruvate and NADH are used to make a ________ amount of ATP. When oxygen is not present, pyruvate is converted to either lactate or ethanol and carbon dioxide.




Stage One: Breakdown of Glucose

Glycolysis

• In the first stage of cellular respiration, glucose is broken down in the cytoplasm during a process called ______________________________.

• As glucose is broken down, some of its hydrogen atoms are _________________________________ to an electron acceptor called NAD+. This forms an electron carrier called NADH.




Stage One: Breakdown of Glucose, continuedGlycolysis

• Glycolysis occurs in four steps:

Step 1 Phosphate groups from _____________ ATP molecules are transferred to a glucose molecule.

Step 2 The resulting six-carbon compound is ________________ down to two three-carbon compounds.

Step 3 Two NADH molecules are produced, and each compound _______________ one more phosphate group.

Step 4 Each three-carbon compound is converted to a three-carbon pyruvate, producing _______________________ ATP molecules in the process.




Stage Two: Production of ATP

• When oxygen is present, pyruvate produced during glycolysis enters a _________________________ and is converted to a two-carbon compound.

• This reaction produces one _________________ dioxide molecule, one NADH molecule, and one two-carbon acetyl group.

• The acetyl group is attached to a molecule called coenzyme A (CoA), forming a _________________ called acetyl-CoA.




Stage Two: Production of ATP, continued

Krebs Cycle

• Acetyl-CoA enters a series of enzyme-assisted reactions called the ____________ cycle, which follows five steps:

Step 1 Acetyl-CoA combines with a four-carbon compound, forming a six-carbon compound and releasing coenzyme A.

Step 2 _________ dioxide is released from the six-carbon compound, forming a five-carbon compound. Electrons are transferred to NAD+, making a molecule of NADH.





Krebs Cycle

Step 3 Carbon dioxide is released from the compound. A molecule of __________ and a molecule of NADH are made.

Step 4 The existing four-carbon compound is converted to a new four-carbon compound. __________________________ are transferred to an electron acceptor called FAD, making a molecule of FADH2, another type of electron carrier.

Step 5 The new four-carbon compound is then converted to the four-carbon compound that began the cycle. Another molecule of _____________________________ is produced.





Electron Transport Train

• In aerobic respiration, electrons _______________ by NADH and FADH2 pass through an electron transport chain.

• In eukaryotic cells, the electron transport chain is located in the inner membranes of _______________________________.

• At the end of the electron transport chain, hydrogen ions and spent electrons combine with oxygen molecules forming ______________________________ molecules.




Respiration in the Absence of Oxygen

• When oxygen is not present, NAD+ is recycled in another way. Under anaerobic conditions, electrons carried by NADH are transferred to pyruvate produced during __________________________.

• This process _________________ NAD+ needed to continue making ATP through glycolysis.

• The recycling of NAD+ using an organic hydrogen acceptor is called fermentation.




Respiration in the Absence of Oxygen, continuedLactic Acid Fermentation

• In some organisms, a three-carbon pyruvate is converted to a three-carbon _______________ through lactic acid fermentation.

• Fermentation enables glycolysis to continue producing ATP in muscles as long as the glucose supply lasts.




Respiration in the Absence of Oxygen, continuedAlcoholic Fermentation

• In some organisms, the three-carbon pyruvate is broken down to ____________ (ethyl alcohol), a two-carbon compound, through alcoholic fermentation.

• As in lactic acid fermentation, NAD+ is recycled, and glycolysis can continue to produce ATP.




Respiration in the Absence of Oxygen, continuedLactic Acid and Alcoholic Fermentation

• When oxygen is not present, cells recycle NAD+ through ______________________________.




Respiration in the Absence of Oxygen, continuedProduction of ATP

• When oxygen is present, ___________________ respiration occurs to produce ATP. When oxygen is not present, fermentation occurs instead.


Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy in Living Systems Directly or indirectly, almost all of the.

Documents

energy section

chemical energy

energy transfer

energy metabolism

extra energy

remaining energy

resourceschapter menu

continued transfer of