Chapter 8 Cellular Chapter 8 Cellular EnergyEnergy

BiologyBiology

Section 8.1 Section 8.1 How Organisms Obtain EnergyHow Organisms Obtain Energy

Main idea – All living organisms use Main idea – All living organisms use energy to carry out all biological energy to carry out all biological processesprocesses

ObjectivesObjectivesSummarize the two laws of Summarize the two laws of

thermodynamicsthermodynamicsCompare and contrast autotrophs and Compare and contrast autotrophs and

heterotrophsheterotrophsDescribe how ATP works in a cellDescribe how ATP works in a cell

Transformation of EnergyTransformation of Energy

All cellular activities require energy; All cellular activities require energy; the ability to do workthe ability to do work

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

Laws of ThermodynamicsLaws of Thermodynamics

The 1The 1stst Law – “Law of conservation of Law – “Law of conservation of energy” – Energy can be converted energy” – Energy can be converted from one form to another, but it from one form to another, but it cannot be created nor destroyedcannot be created nor destroyed

The 2The 2ndnd Law – Energy that is “lost” is Law – Energy that is “lost” is generally converted to thermal generally converted to thermal energy – “entropy increases”energy – “entropy increases”

Entropy – measure of disorder or Entropy – measure of disorder or unusable energy, in a system. unusable energy, in a system.

Autotrophs & HeterotrophsAutotrophs & Heterotrophs Autotrophs – organisms that make their Autotrophs – organisms that make their

own foodown food Chemoautotrophs – uses chemicals as a Chemoautotrophs – uses chemicals as a

source of energysource of energy Photoautotrophs – convert light energy from Photoautotrophs – convert light energy from

the Sun into chemical energythe Sun into chemical energy Heterotrophs – organisms that need to Heterotrophs – organisms that need to

ingest food to obtain energyingest food to obtain energy

MetabolismMetabolism All of the chemical reactions in a cell are All of the chemical reactions in a cell are

referred to as the cell’s metabolismreferred to as the cell’s metabolism Metabolic pathway is a series of chemical Metabolic pathway is a series of chemical

reactions in which the product of one reactions in which the product of one reaction is the substrate for the next reaction is the substrate for the next reactionreaction Catabolic pathwaysCatabolic pathways – releases energy by – releases energy by

breaking down larger molecules into smaller onesbreaking down larger molecules into smaller ones Anabolic pathwaysAnabolic pathways –uses the energy released by –uses the energy released by

catabolic pathways to build larger molecules catabolic pathways to build larger molecules from smaller moleculesfrom smaller molecules

The continual flow of energy within an The continual flow of energy within an organism is the result of the relationship of organism is the result of the relationship of catabolic and anabolic pathwayscatabolic and anabolic pathways

PhotosynthesisPhotosynthesis

Photosynthesis is the anabolic Photosynthesis is the anabolic pathway in which light energy from pathway in which light energy from the Sun is converted to chemical the Sun is converted to chemical energy for use by the cellenergy for use by the cell

6CO6CO22 + 6H + 6H22O O C C66HH1212OO66 + 6O + 6O22

Cellular RespirationCellular Respiration

Cellular Respiration is the catabolic Cellular Respiration is the catabolic pathway in which organic molecules pathway in which organic molecules are broken down to release energy are broken down to release energy for use by the cellsfor use by the cells

CC66HH1212OO6 6 + 6O+ 6O22 6CO 6CO22 + 6H + 6H22O + ATPO + ATP

Photosynthesis & Cellular Photosynthesis & Cellular Respiration Form a CycleRespiration Form a Cycle

ATP: The Unit of Cellular ATP: The Unit of Cellular EnergyEnergy

Adenosine Triphosphate (ATP) is the most Adenosine Triphosphate (ATP) is the most important biological molecule that provides important biological molecule that provides chemical energychemical energy

ATP is made of an adenine base, a ribose ATP is made of an adenine base, a ribose sugar, and three phosphate groupssugar, and three phosphate groups

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

Energy is stored in the phosphate bond Energy is stored in the phosphate bond formed when ADP receives a phosphate formed when ADP receives a phosphate group and becomes ATPgroup and becomes ATP

ATP: The Unit of Cellular ATP: The Unit of Cellular EnergyEnergy

Section 8.2 PhotosynthesisSection 8.2 Photosynthesis

Main idea – Light energy is trapped Main idea – Light energy is trapped and converted into chemical energy and converted into chemical energy during photosynthesisduring photosynthesis

ObjectivesObjectivesSummarize the two phases of Summarize the two phases of

photosynthesisphotosynthesisExplain the function of a chloroplast Explain the function of a chloroplast

during the light reactionsduring the light reactionsDescribe and diagram electron transportDescribe and diagram electron transport

Overview of PhotosynthesisOverview of Photosynthesis

Photosynthesis is a process in which light Photosynthesis is a process in which light energy is converted into chemical energyenergy is converted into chemical energy

6CO6CO22 + 6H + 6H22O O C C66HH1212OO66 + 6O + 6O22

Photosynthesis occurs in two phasesPhotosynthesis occurs in two phases Phase 1-Light-dependent reactions-light energy Phase 1-Light-dependent reactions-light energy

is absorbed and then converted into chemical is absorbed and then converted into chemical energy in the form of ATP and NADPHenergy in the form of ATP and NADPH

Phase 2-Light-independent reactions-the ATP Phase 2-Light-independent reactions-the ATP and NADPH formed in phase 1 is used to make and NADPH formed in phase 1 is used to make glucoseglucose

Phase 1: Light ReactionsPhase 1: Light Reactions

Chloroplasts – capture light energy in Chloroplasts – capture light energy in photosynthetic organisms; disc-photosynthetic organisms; disc-shaped organelles that contain two shaped organelles that contain two main compartmentsmain compartmentsThylakoids are flattened saclike Thylakoids are flattened saclike

membranes that are arranged in stacks membranes that are arranged in stacks (grana) and are the location of light-(grana) and are the location of light-dependent reactionsdependent reactions

Stroma are the fluid spaces outside the Stroma are the fluid spaces outside the grana and are the location of light-grana and are the location of light-independent reactionsindependent reactions

Phase 1: Light ReactionsPhase 1: Light Reactions

PigmentsPigments

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

Chlorophylls are the major light-Chlorophylls are the major light-absorbing pigments in plants; absorbing pigments in plants; reflecting green lightreflecting green light

Accessory pigments allow plants to Accessory pigments allow plants to trap additional light energy trap additional light energy Carotenoids – reflect yellow, orange and Carotenoids – reflect yellow, orange and

red lightred light

Electron TransportElectron Transport

Activated electrons are passed from Activated electrons are passed from one molecule to another along the one molecule to another along the thylakoid membrane in a chloroplast. thylakoid membrane in a chloroplast. The energy from electrons is used to The energy from electrons is used to form a proton gradient. As protons form a proton gradient. As protons move down the gradient, a move down the gradient, a phosphate is added to ADP, forming phosphate is added to ADP, forming ATPATP

Electron Transport (cont.)Electron Transport (cont.) Light energy absorbed by photosystem II is Light energy absorbed by photosystem II is

used to split a molecule of water. When used to split a molecule of water. When water splits, oxygen is released from the water splits, oxygen is released from the cell, protons (Hcell, protons (H++; hydrogen ions) stay in ; hydrogen ions) stay in the thylakoid space and an activated the thylakoid space and an activated electron enters the electron transport electron enters the electron transport chainchain

As electrons move through the membrane, As electrons move through the membrane, protons are pumped into the thylakoid protons are pumped into the thylakoid spacespace

At photosystem I, electrons are re-At photosystem I, electrons are re-energized and NADPH is formedenergized and NADPH is formed

Electron Transport (cont.)Electron Transport (cont.)

Chemiosmosis: Protons accumulate Chemiosmosis: Protons accumulate in the thylakoid space, creating a in the thylakoid space, creating a concentration gradientconcentration gradient

When protons move across the When protons move across the thylakoid membrane through ATP thylakoid membrane through ATP synthase, ADP is converted to ATPsynthase, ADP is converted to ATP

Phase 2: Calvin Cycle Phase 2: Calvin Cycle Light-independent ReactionsLight-independent Reactions

Calvin Cycle – Calvin Cycle – the second the second phase of phase of photosynthesiphotosynthesis in which s in which energy is energy is stored in stored in organic organic molecules molecules such as such as glucose glucose

Calvin Cycle (cont.)Calvin Cycle (cont.)

First step – carbon fixation - 6COFirst step – carbon fixation - 6CO2 2 + 6 + 6 RuBP (ribulose 1,5-biphosphate a 5-RuBP (ribulose 1,5-biphosphate a 5-carbon compound) to form 12 3-PGA carbon compound) to form 12 3-PGA (3-phosphoglycerate, a 3-carbon (3-phosphoglycerate, a 3-carbon molecule)molecule)

Second step – the chemical energy Second step – the chemical energy stored in 12 ATP and 12 NADPH is stored in 12 ATP and 12 NADPH is transferred to the 12 3-PGA to form transferred to the 12 3-PGA to form 12 G3P (glyceraldehyde 3-phosphate, 12 G3P (glyceraldehyde 3-phosphate, high energy molecules)high energy molecules)

Calvin Cycle (cont.)Calvin Cycle (cont.)

Third step – 2 G3P leave the cycle to form Third step – 2 G3P leave the cycle to form glucose and other organic compoundsglucose and other organic compounds

Final step – An enzyme called rubisco Final step – An enzyme called rubisco converts the remaining 10 G3P into RuBP.converts the remaining 10 G3P into RuBP.

Plants use the sugars formed during the Plants use the sugars formed during the Calvin Cycle both as source of energy and Calvin Cycle both as source of energy and as building blocks for complex as building blocks for complex carbohydrates, including cellulose, which carbohydrates, including cellulose, which provides structural support for the plantprovides structural support for the plant

Alternative PathwaysAlternative Pathways Many plants in extreme climates have Many plants in extreme climates have

alternative photosynthesis pathways to alternative photosynthesis pathways to maximize energy conversionmaximize energy conversion

CC4 4 plants minimize water loss by closing stoma in hot days as they fix carbon dioxide into 4-carbon compounds instead of the 3-carbon molecules during the Calvin Cycle

CAM plants (crassulacean acid metabolism) occurs in water-conserving plants as CO2

enters leaves at night fixing it into organic molecules. During the day, CO2 is released and enters the Calvin Cycle

8.3 Cellular Respiration8.3 Cellular Respiration

Main idea – Living organisms obtain Main idea – Living organisms obtain energy by breaking down organic energy by breaking down organic molecules during cellular respirationmolecules during cellular respiration

ObjectivesObjectivesSummarize the stages of cellular Summarize the stages of cellular

respirationrespirationIdentify the role of electron carriers in each Identify the role of electron carriers in each

stage of cellular respirationstage of cellular respirationCompare alcoholic fermentation and lactic Compare alcoholic fermentation and lactic

acid fermentationacid fermentation

Overview of Cellular Overview of Cellular RespirationRespiration

Organisms obtain energy in a Organisms obtain energy in a process called cellular respirationprocess called cellular respiration

The function of cellular respiration is The function of cellular respiration is to harvest electrons from carbon to harvest electrons from carbon compounds, such as glucose, and compounds, such as glucose, and use that energy to make ATPuse that energy to make ATP

CC66HH1212OO6 6 + 6O+ 6O22 6CO 6CO22 + 6H + 6H22O + ATPO + ATP

Cellular Respiration (cont.)Cellular Respiration (cont.)

Two main partsTwo main parts GlycolysisGlycolysis

Anaerobic process – do not require oxygenAnaerobic process – do not require oxygen Aerobic RespirationAerobic Respiration

Krebs cycle & electron transportKrebs cycle & electron transportAerobic process – requires oxygenAerobic process – requires oxygen

GlycolysisGlycolysis Glucose is broken down in the cytoplasm Glucose is broken down in the cytoplasm

through the process of glycolysis, refer to through the process of glycolysis, refer to Figure 8.12 on p. 229Figure 8.12 on p. 229

First, 2 phosphate groups are joined to glucoseFirst, 2 phosphate groups are joined to glucose Second, the 6-carbon molecule is broken down Second, the 6-carbon molecule is broken down

into 2 G3Pinto 2 G3P Next, two phosphates are added and electrons Next, two phosphates are added and electrons

and hydrogen ions combine to produce 4 ATP and hydrogen ions combine to produce 4 ATP and 2 NADH, respectfullyand 2 NADH, respectfully

Last, the 2 G3P are converted into 2 pyruvate Last, the 2 G3P are converted into 2 pyruvate moleculesmolecules

Glycolysis has a net yield of 2 ATP moleculesGlycolysis has a net yield of 2 ATP molecules

Krebs CycleKrebs CycleThe series of reactions in which The series of reactions in which

pyruvate is broken down into carbon pyruvate is broken down into carbon dioxide is called the Krebs cycle or dioxide is called the Krebs cycle or tricarboxylic acid (TCA) cycle.tricarboxylic acid (TCA) cycle.

This cycle is known as the citric acid This cycle is known as the citric acid cycle, toocycle, too

The Krebs cycle occurs inside the The Krebs cycle occurs inside the mitochondria of cells.mitochondria of cells.

Krebs Cycle (cont.)Krebs Cycle (cont.)

Prior to the Krebs cycle, pyruvate reacts Prior to the Krebs cycle, pyruvate reacts with coenzyme A (CoA) to form acetyl with coenzyme A (CoA) to form acetyl CoACoA

At the same time COAt the same time CO22 is released and is released and NADNAD++ is converted into NADH is converted into NADH

The reaction results in the production of The reaction results in the production of 2 CO2 CO22 molecules and two NADH molecules and two NADH

The cycle begins with acetyl CoA The cycle begins with acetyl CoA combining with a 4-carbon compound to combining with a 4-carbon compound to form citric acid, a 6 carbon compoundform citric acid, a 6 carbon compound

Krebs Cycle (cont.)Krebs Cycle (cont.) Then, citric acid is broken down in the next Then, citric acid is broken down in the next

series of steps, releasing 2 molecules of COseries of steps, releasing 2 molecules of CO22 and generating one ATP, three NADH, and and generating one ATP, three NADH, and one FADHone FADH22. FAD is another electron carrier . FAD is another electron carrier similar to NADsimilar to NAD++ and NADP and NADP++

Finally, acetyl CoA and citric acid are Finally, acetyl CoA and citric acid are generated and the cycle continuesgenerated and the cycle continues

The net yield from the Krebs cycle is 6 COThe net yield from the Krebs cycle is 6 CO22 molecules, 2 ATP, 8 NADH, and 2 FADHmolecules, 2 ATP, 8 NADH, and 2 FADH2. 2.

NADH and FADH move on to play a NADH and FADH move on to play a significant role in the next stage of aerobic significant role in the next stage of aerobic respirationrespiration

Krebs CycleKrebs Cycle

Electron TransportElectron Transport Refer to Figure 8.14 on p. 231Refer to Figure 8.14 on p. 231 Electrons move along the mitochondrial Electrons move along the mitochondrial

membrane from one protein to anothermembrane from one protein to another Electrons are transported to oxygen to Electrons are transported to oxygen to

form waterform water Electron transport produces 24 ATPElectron transport produces 24 ATP

Each NADH molecule produces 3 ATPEach NADH molecule produces 3 ATP Each group of 3 FADHEach group of 3 FADH2 2 produces 2 ATPproduces 2 ATP In eukaryotes, one molecule of glucose yields In eukaryotes, one molecule of glucose yields

36 ATP36 ATP In prokaryotes, one molecule of glucose In prokaryotes, one molecule of glucose

produces 38 ATPproduces 38 ATP

Anaerobic RespirationAnaerobic Respiration

The anaerobic pathway that follows The anaerobic pathway that follows glycolysis is anaerobic respiration, or glycolysis is anaerobic respiration, or fermentationfermentation

Fermentation occurs in the cytoplasm Fermentation occurs in the cytoplasm and regenerates the cell’s supply of and regenerates the cell’s supply of NADNAD++ while producing a small amount while producing a small amount of ATPof ATP

Two typesTwo typesLactic acid fermentationLactic acid fermentationAlcohol fermentationAlcohol fermentation

Lactic acid fermentation & Lactic acid fermentation & Alcohol fermentationAlcohol fermentation

Lactic acid fermentationLactic acid fermentationEnzymes convert the pyruvate made Enzymes convert the pyruvate made

during glycolysis to lactic acidduring glycolysis to lactic acidWhen oxygen is absent or in limited When oxygen is absent or in limited

supply, fermentation can occursupply, fermentation can occurSkeletal muscles during strenuous exerciseSkeletal muscles during strenuous exerciseMicroorganisms to produce cheese, yogurt & Microorganisms to produce cheese, yogurt &

sour creamsour cream

Alcohol fermentationAlcohol fermentationOccurs in yeast and some bacteria when Occurs in yeast and some bacteria when

pyruvate is converted to ethyl alcohol and pyruvate is converted to ethyl alcohol and COCO22

Photosynthesis & Cellular Photosynthesis & Cellular RespirationRespiration

Processes cells use to obtain energyProcesses cells use to obtain energyMetabolic pathways that produce and Metabolic pathways that produce and

break down simple carbohydratesbreak down simple carbohydratesThe products of Photosynthesis are The products of Photosynthesis are

oxygen and glucose – the reactants oxygen and glucose – the reactants needed for cellular respirationneeded for cellular respiration

The products of cellular respiration – The products of cellular respiration – carbon dioxide and water – are the carbon dioxide and water – are the reactants for photosynthesisreactants for photosynthesis