Chapter 8 Cellular Energy

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Chapter 8 Cellular Energy

Section 1: How Organisms Obtain Energy

Section 2: Photosynthesis

Section 3: Cellular Respiration

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• Big Idea– Photosynthesis converts the Sun’s energy into

chemical energy, while cellular respiration uses chemical energy to carry out life function.

All living organisms use energy to carry out all biological processes

Macromolecules are assembled and broken down, substances are transported across cell membranes, and genetic instructions are transmitted.

All of these cellular activities require energy.

8.1 How Organisms Obtain Energy

Cellular EnergyChapter 8

Transformation of Energy

Energy is the ability to do work.


Cellular Energy

Thermodynamics is the study of the flow and transformation of energy in the universe.

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Laws of Thermodynamics

First law— (Law of conservation of energy)energy can be converted from one form to another, but it cannot be created nor destroyed.


Cellular Energy

Examples:Food is converted to chemical energy when you eatMechanical energy when you run or kick a ball

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Cellular Energy

Second law—energy cannot be converted without the loss of usable energy.“loss” energy is generally converted to thermal energyIncreases Entropy

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Cellular Energy

Entropy – The measure of disorder (or unusable energy) in a system

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Autotrophs and Heterotrophs

Nearly all the energy for life comes from the Sun




Autotrophs are organisms that make their own food.




Autotrophs are organisms that make their own food.

Examples:Chemoautotrophs use inorganic substances such as hydrogen sulfide as a source of energyPhotoautotrophs (like plants) convert light energy from the Sun into chemical energy.





Cellular Energy

Heterotrophs are organisms that need to ingest food to obtain energy.

Examples:AphidLady bug

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Metabolism

All of the chemical reactions in a cell


Cellular Energy

Photosynthesis—light energy from the Sun is converted to chemical energy for use by the cell

Cellular respiration—organic molecules are broken down to release energy for use by the cell

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Metabolism

Metabolic Pathway – Series of chemical reactions in which the product of one reaction is the substrate for the next reactionExamples:

Catabolic pathwaysAnabolic pathways



Metabolism

Metabolic Pathway – Examples:

Catabolic pathwaysRelease energy by breaking down larger molecules into smaller molecules



Metabolism

Metabolic Pathway – Examples:

Anabolic pathwaysUse the energy released by catabolic pathways to build larger molecules from smaller molecules



Photosynthesis

Photosynthesis is the anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell.Autotrophs use light energy, carbon dioxide, and water to form glucose and oxygen

Cellular Energy


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Cellular Respiration

Cellular Respiration is the catabolic pathway in which organic molecules are broken down to release energy for use by the cell.Oxygen is used to break down organic molecules, resulting in the production of carbon dioxide and water

Cellular Energy


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ATP: The Unit of Cellular Energy

ATP (Adenosine Triphosphate) releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate group.




ATP structureA nucleotide made of an adenine base, a ribose sugar, and three phosphate group




ATP functionATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate group



Main Idea: light energy is trapped and converted into chemical energy during photosynthesis

• Photo – means “light”• Synthesis – means “to create”

Cellular Energy

8.2 Photosynthesis

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Most autotrophs – including plants – make organic compounds, such as sugars, by a process called photosynthesis

Cellular Energy

8.2 Photosynthesis

Chapter 8

Overview of Photosynthesis

Photosynthesis occurs in two phases.

Cellular Energy

Light-dependent reactions

Light-independent reactions

8.2 Photosynthesis

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Phase One: Light Reactions (Light – Dependent Reaction)

The absorption of light is the first step in photosynthesis.

Light energy is absorbed and then transformed into chemical energy in the form of ATP and NADPH

Cellular Energy

8.2 Photosynthesis

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Cellular Energy

Chloroplasts large organelles that capture light energy.

8.2 Photosynthesis

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Cellular Energy

Chloroplasts are mainly found in the cells of leaves in plants.

8.2 Photosynthesis

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Cellular Energy

Thylakoids are flattened saclike membranes that arranged in stacks called grana.

8.2 Photosynthesis

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Cellular Energy

Stroma is the fluid- filled space outside the grana

8.2 Photosynthesis

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Cellular Energy

Pigments are light-absorbing molecules found in the thylakoid membranes of chloroplasts

8.2 Photosynthesis

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Cellular Energy

Chlorophyll is the major light – absorbing pigment in plants.

Two types of chlorophyll:Chlorophyll aChlorophyll b

Accessory pigments called carotenoids produce the color of carrots and sweet potatoes

8.2 Photosynthesis

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Electron Transport

Light energy excites electrons in photosystem II and also causes a water molecule to split, releasing an electron into the electron transport system, H+ into the thylakoid space, and O2 as a waste product.

Cellular Energy

8.2 Photosynthesis

Chapter 8

The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane.

The electron-acceptor molecule transfers the electrons along a series of electron-carriers to photosystem I.

Cellular Energy

8.2 Photosynthesis

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Cellular Energy

8.2 Photosynthesis

Photosystem I transfers the electrons to a protein called ferrodoxin.

Ferrodoxin transfers the electrons to the electron carrier NADP+, forming the energy-storing molecule NADPH.

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The Light Reaction

Light Reactions

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8.2 Photosynthesis

Phase Two: The Calvin Cycle (Light – Independent Reaction)

In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose.

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Cellular Energy

8.2 Photosynthesis


The ATP and NADPH that were formed in phase one are used to make glucose

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Cellular Energy

8.2 Photosynthesis


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Cellular Energy

8.2 Photosynthesis

1st Step (Carbon Fixation) - Six CO2 molecules combine with six 5-carbon compounds to form twelve 3-carbon molecules called 3-PGA.

2nd Step (Reduction) - The chemical energy stored in ATP and NADPH is transferred to the 3-PGA molecules to form high-energy molecules called (glyceraldehyde 3- phosphate) G3P.

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Cellular Energy

8.2 Photosynthesis

3rd Step - Two G3P molecules leave the cycle to be used for the production of glucose and other organic compounds.

Final Step (Regeneration of RuBP)- An enzyme called rubisco converts the remaining ten G3P molecules into 5-carbon molecules called RuBP. These molecules combine with new carbon dioxide molecules to continue the cycle.

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Cellular Energy

8.2 Photosynthesis

Alternative Pathways

C4 plants

CAM plants

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Overview of Cellular Respiration

Organisms obtain energy in a process called cellular respiration.

8.3 Cellular Respiration

Cellular Energy

The equation for cellular respiration is the opposite of the equation for photosynthesis.

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Cellular Energy

Cellular respiration occurs in two main parts.

Glycolysis

Aerobic respiration

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Glycolysis

Glucose is broken down in the cytoplasm through the process of glycolysis.



Glycolysis


Cellular Energy

Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down.

Two molecules of ATP are required to start the reactions that will produce energy for the cell

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Glycolysis8.3 Cellular Respiration

Cellular Energy

• 2 phosphate groups are joined to glucose (the 2 Phosphate groups are derived from 2 molecules of ATP)

• The 6-Carbon molecule of Glucose is broken into two 3-Carbon compounds

• Two Phosphate groups are added and electrons and hydrogen ions (H+) combine with two NAD+ molecules to form NADH molecules

• Keep in mind that NAD+ is an electron carrier that is similar to NADP (an electron carrier used during photosynthesis)

• The two 3-Carbon compounds are converted into two molecules of pyruvate

• At the same time 4 molecules of ATP are produced

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Glycolysis

Glycolysis has a net result of two ATP and two pyruvate.



Krebs Cycle


Cellular Energy

Also known as the tricarboxylic acid (TCA) cycle

Also known as the citric acid cycle

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Krebs Cycle


Cellular Energy

Most of the energy from the glucose is still contained in the pyruvate.

The series of reactions in which pyruvate is broken down into carbon dioxide is called the Krebs cycle.

When oxygen is present, pyruvate is transported into the mitochondrial matrix

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Cellular Energy

• Begins with acetyl CoA combining with a 4-Carbon compound to form a 6 – Carbon compound known as citric acid

• Citric acid is then broken down in the next series of steps, releasing 2 molecules of carbon dioxide and generating one ATP, three NADH, and one FADH2. FAD is another electron carrier similar to NAD+ and NADP+

• Acetyl CoA and citric acid are generated and the cycle continues.

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Before the Krebs Cycle


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Pyruvate first reacts with coenzyme A (CoA) to form a 2-Carbon intermediate called acetyl CoA.

At the same time NAD+ is converted to NADH and carbon dioxide is released.

Acetyl CoA then moves to the mitochondria matrix. 2 CO2 and 2NADH are produced.

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Cellular Energy

Two molecules of pyruvate are formed during glycolysis. This means that there are two “turns” of the Krebs Cycle for each glucose molecule.

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Cellular Energy

The net yield from the Krebs cycle is six CO2 molecules, two ATP, eight NADH, and two FADH2.

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Cellular Energy

Electron Transport

Final step in the breakdown of glucose

Point at which ATP is produced

Produces 24 ATP

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Cellular Energy

Electron Transport

• The final step in the breakdown of glucose.• Point where most ATP is produced• Electrons and hydrogen ions from NADH and FADH2

produced in Krebs Cycle are used to convert ADP to ATP.

• Electrons move along mitochondrial membrane from one protein to another.

• H+ ions are pumped into the mitochondrial matrix across the inner mitochondrial membrane.

• Those H+ ions then diffuse through ATP synthase into the mitochondrial matrix. This process converts ADP to ATP in a process called chemiosmosis

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Cellular Energy

Electron Transport

• Similarities and Differences in Electron Transport in Photosynthesis and Cellular Respiration

Photosynthesis Cellular Respiration

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Cellular Energy

Some Prokaryotes

• Aerobic organisms that undergo aerobic respiration, but because they do not have mitochondria, they use the plasma membrane as the location of the electron transport.

• Anaerobic organism that grow and reproduce without oxygen.• ATP is produced through glycolysis

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Cellular Energy

Anaerobic Respiration

The anaerobic pathway that follows glycolysis One type is fermentation

Two main types Lactic acid fermentation

Alcohol fermentation


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Cellular Energy

Fermentation

Two main types Lactic acid fermentation – enzymes convert

the pyruvate in glycolysis to lactic acid

Alcohol fermentation – type of fermentation in which pyruvate is converted to ethyl alcohol and carbon dioxide


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Cellular Energy

How are photosynthesis and cellular respiration related?


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1. A2. B3. C4. D

CDQ 1

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A. Energy cannot be converted or destroyed.

B. Energy can be converted and destroyed.

C. Energy can be converted but not destroyed.

D. Energy can be destroyed but not converted.

Which statement describes the law of conservation of energy?

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Chapter Diagnostic Questions

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1. A2. B3. C4. D

CDQ 2

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A. photosynthesis

B. cellular respiration

C. homeostasis

D. fermentation

In which metabolic process are molecules broken down to produce carbon dioxide and water?

1. A2. B3. C4. D

CDQ 3

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Cellular Energy


Chapter 8

A. NADPH

B. ATP

C. chloroplast

D. glucose

At the end of the Calvin cycle, where is energy stored?

1. A

2. B

FQ 1


Which law of thermodynamics explains why the ladybug receives the least amount of usable energy?

A. the first law of thermodynamics

B. the second law of thermodynamics

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8.1 Formative Questions

1. A

2. B

FQ 2


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All of the energy from the food you eat comes from the sun.

A. true

B. false

1. A

2. B

3. C

4. D

FQ 3



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Why is cellular respiration a catabolic pathway?

A. Energy is used to form

glucose and oxygen.

B. Energy is converted from

water to carbon dioxide.

C. Energy that is lost is

converted to thermal energy.

D. Energy is released by the

breakdown of molecules.

1. A

2. B

3. C

4. D

FQ 4



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A. It captures light energy from the sun.

B. It is produced in anabolic pathways.

C. It stores and releases chemical energy.

D. It converts mechanical energy to thermal energy.

Why is adenosine triphosphate (ATP) such an important biological molecule?

1. A

2. B

3. C

4. D

FQ 5


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A. chloroplasts

B. Golgi apparatus

C. mitochondria

D. vacuoles

Where in the plant cell does photosynthesis take place?


1. A

2. B

3. C

FQ 6



A. 400-500 nm

B. 500-600 nm

C. 600-700 nm

Which range of wavelengths is reflected by chlorophylls a and b?

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1. A

2. B

3. C

4. D

FQ 7



A. absorption

B. chemiosmosis

C. electron transport

D. C2 pathway

Which mechanism of photosynthesis uses the movement of hydrogen ions (H+) across a concentration gradient to synthesize ATP?

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1. A

2. B

3. C

4. D

FQ 8



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A. They accelerate photosynthesis.

B. They release more oxygen.

C. They help the plant conserve water.

D. They reduce the requirement for ATP.

How are the C4 pathway and the CAM pathway

an adaptive strategy for some plants?

1. A

2. B

3. C

4. D

FQ 9


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A. to make ATP

B. to process H2O

C. to store glucose

D. to deliver oxygen

What is the overall purpose of cellular respiration?


1. A

2. B

3. C

4. D

FQ 10


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Which represents the general sequence of cellular respiration?

A. TCA cycle chemiosmosis glycolysis

B. glycolysis Krebs cycle electron transport

C. electron absorption catalysis phosphorylation

D. aerobic pathway anaerobic pathway fermentation


1. A

2. B

3. C

FQ 11


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A. glycolysis

B. Krebs cycle

C. electron transport

Which stage of cellular respiration is the anaerobic process?


1. A

2. B

3. C

4. D

FQ 12


A. CoA

B. CO2

C. FADH2

D. NADH

Which molecule generated by the Krebs cycle is a waste product?

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1. A

2. B

3. C

4. D

CAQ 1


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Look at the following figure. Which part of the chloroplast is a sac-like membrane arranged in stacks?

A. grana

B. stroma

C. thylakoids

D. Golgi apparatus

Chapter Assessment Questions

1. A

2. B

3. C

4. D

CAQ 2


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During the Krebs cycle, pyruvate is broken down into what compound?

A. H2O

B. O2

C. CO

D. CO2

1. A

2. B

3. C

4. D

CAQ 3


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Look at the following figure. Which molecule is released when ATP becomes ADP?

A. phosphate group

B. water molecule

C. ribose sugar

D. energy cells

1. A

2. B

STP 1


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Which metabolic process is photosynthesis?

A

B

Standardized Test Practice

1. A

2. B

3. C

4. D

STP 2


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At the beginning of photosynthesis, which molecule is split to produce oxygen (O2) as

a waste product?

A. CO2

B. H2O

C. C6H12O6

D. 3-PGA

1. A

2. B

3. C

4. D

STP 3


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Which molecule helps provide the energy that drives this cycle?

A. 3-PGA

B. CO2

C. NADPH

D. rubisco

1. A

2. B

3. C

4. D

STP 4


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Which product of the Calvin cycle is used for the production of glucose and other organic compounds?

A. ADP

B. CO2

C. G3P

D. NADP+

1. A

2. B

3. C

4. D

STP 5


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What is the final step of cellular respiration?

A. O2 and H+ form H2O.

B. Electrons and H2O generate ATP.

C. C6H12O6 is broken down into CO2.

D. NADH and FADH2 gain electrons.

1. A

2. B

3. C

4. D

STP 6


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What prevents pyruvate from entering the Krebs cycle and instead results in this pathway?

A. a buildup of CO2

B. a lack of oxygen

C. an excess of glucose

D. an increased demand for ATP

1. A

2. B

3. C

4. D

STP 7


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Which is not a process that occurs in both cellular respiration and glycolysis?

A. chemiosmosis

B. electron transport

C. glycolysis

D. production of G3P

Cellular Energy

Glencoe Biology Transparencies

Chapter 8

Cellular Energy

Image Bank

Chapter 8

energy

thermodynamics

metabolism

Photosynthesis

cellular respiration

adenosine triphosphate (ATP)


Vocabulary

Section 1

thylakoid

granum

stroma

pigment

NADP+

Calvin cycle

rubisco


Vocabulary

Section 2

anaerobic process

aerobic respiration

aerobic process

glycolysis

Krebs cycle

fermentation


Vocabulary

Section 3

Cellular Energy

ATP

The Calvin Cycle

Visualizing Electron Transport

The Krebs Cycle (Citric Acid Cycle)

Animation

Chapter 8




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Chapter 8 Cellular Energy