Copyright © 2006 Pearson Prentice Hall, Inc. Intro to Biology Week 2 Energy in Cells, Capturing Energy and Harvesting Energy – Glycolysis, and Cellular

Copyright © 2006 Pearson Prentice Hall, Inc.

Intro to BiologyWeek 2

Energy in Cells, Capturing Energy and Harvesting Energy –

Glycolysis, and Cellular Respiration – Athletes.

Chapter 5

• Energy Flow in the Life of a Cell


What Is Energy?

• From potential energy to kinetic energy

• Potential – energy not yet released

• Kinetic – energy in motion


Potential Energy

Kinetic Energy


Laws of ThermodynamicsLaws of Thermodynamics

First Law (ConservationFirst Law (Conservation of Energy)of Energy)Energy is neither created nor destroyed; it Energy is neither created nor destroyed; it is always conserved.is always conserved.

Second LawSecond LawEnergy always tends to go from a more Energy always tends to go from a more usable form to a less usable form, so the usable form to a less usable form, so the amount of energy available to do work amount of energy available to do work decreases (entropy occurs). decreases (entropy occurs).



Consequence Of Laws Of Thermodynamics For Living

Organisms

Organisms require a constant input Organisms require a constant input of energy to maintain a high level of of energy to maintain a high level of

organization.organization.

““Feed Me Seymour!” Feed Me Seymour!”


Types of Energy SystemsTypes of Energy SystemsThis Slide is Yellow


What Is Energy?• Energy Cannot Be Created or Destroyed (1st

Law)• Energy Tends to Become Distributed Evenly

(2nd Law)• Matter Tends to Become Less Organized (2nd

Law)• Living Things Use the Energy of Sunlight to

Create Low-Entropy Conditions– We can see “opposite of entropy” flow when a

tremendous amount of energy is used…


How Does Energy Flow in Chemical Reactions?

• Exergonic reaction (p. 75)

• “Exit” – energy is released

• Sugar is burned in a flame or consumed in the body, it reacts with oxygen and produces CO2 and H2O + energy


Exergonic reaction

reactants

products

energyreleased


The other way…

• Endergonic reaction (p. 75)

• Takes in energy – saves it (“Engender”)

• CO2 + Water + energy = sugar and oxygen


reactants

products

energyused

Endergonic reaction



• (Again) Exergonic Reactions Release Energy

• The specifics: Burning glucose (sugar)


Burning glucose

glucose oxygen

carbondioxide

water

energyreleased



• Endergonic Reactions Require an Input of Energy

– The specifics:• Photosynthesis (p. 76)


Photosynthesis

glucose oxygen

carbondioxide

water

energy



• Important Part: All Reactions Require an Initial Input of Energy– Things don’t burst into flame without some

kick – even exergonic ones– Think of it as a blasting cap or fuse needed

to kick off the stick of dynamite– Energy relations in exergonic and

endergonic reactions (p. 76)


Burning glucose (sugar): an exergonic reaction Photosynthesis: an endergonic reaction

high

energycontent

of molecules

low

high

energycontent

of molecules

low

progress of reaction progress of reaction

activation energy neededto ignite glucose

activation energy from

light capturedby photosynthesis

glucose

glucose + O2

CO2 + H2O CO2 + H2O

energy releasedby burning glucose

net energy captured bysynthesizing

glucose


Burning glucose (sugar): an exergonic reaction

high

energycontent

of molecules

low

energy releasedby burning glucose

progress of reaction

activation energy neededto ignite glucose

glucose + O2

CO2 + H2O


Photosynthesis: an endergonic reaction

high

low


activation energy from

light capturedby photosynthesis

glucose

CO2 + H2O

net energy captured bysynthesizing

glucose

energycontent

of molecules



• Exergonic Reactions May Be Linked with Endergonic Reactions

• Called a coupled reaction, the exergonic reaction provides the input energy needed for the endergonic reaction:

• An ATP reaction creates energy


How Is Energy Carried between Coupled Reactions?

• ATP Is the Principal Energy Carrier in Cells adenosine triphosphate

– ATP synthesis: Energy is stored in ATP– It is the ‘big one’ we will hear about again

and again

ENERGY IN!


ATP synthesis: Energy is stored in ATP

energy

ADP phosphate

ATP


Energy Out

– ATP breakdown: Energy of ATP is released (p. 77)


ATP breakdown: Energy of ATP is released

energy

ATP

phosphateADP


And things can get more complex…

– A coupled reaction (p. 77) (first figure)

Storage and release processes can work together to make the body work!

– Figure 5.4 Coupled reactions give off heat (p. 78) (second figure)


Exergonic reaction:

Endergonic reaction:

Coupled reaction:

relaxedmuscle

relaxedmuscle

20 unitsenergy

contractedmuscle

100 unitsenergy released

80 units energyreleased as heat

contractedmuscle


Coupled reaction: glucose breakdown and protein synthesis

glucose

exergonic(glucosebreakdown) endergonic

(ATP synthesis)

exergonic(ATP breakdown)

endergonic(protein synthesis)

net exergonic“downhill” reaction

ADP + heat

protein

aminoacids

CO2 + H2O + heat


How Is Energy Carried between Coupled Reactions?

• Subtitle- when complex reactions work together…

• Electron Carriers Also Transport Energy within Cells– Electron carriers (p. 78)

– This is just to show you how things begin to build from the microscopic up to the gigantic (your muscles).


Electron carrier molecules transport energy

endergonicreaction

net exergonic“downhill” reaction

(energizedcarrier)

(depletedcarrier)

exergonicreaction


How Do Cells Control Their Metabolic Reactions?

(or how to not have spontaneous human combustion)

• The cell is a tiny chemical factory. As it works, this production of chemicals is called it’s metabolism

• Many chemical reactions linked together make up a metabolic pathway

• (next slide) Simplified view of metabolic pathways (p. 79)


Initial reactant Intermediates Final products

PATHWAY 1

enzyme 1 enzyme 2 enzyme 3 enzyme 4

enzyme 5 enzyme 6

PATHWAY 2



• At Body Temperatures, Many Spontaneous Reactions Proceed Too Slowly to Sustain Life, something is needed to make them happen easier…

• Catalysts Reduce Activation Energy– Figure 5.7 Catalysts reduce activation

energy (p. 79)


high

low

energycontent

ofmolecules reactants

products


activation energywith catalyst

activation energywithoutcatalyst



• Enzymes Are Biological Catalysts (you’ve heard of enzymes before… now you know what they do)

• The Structure of Enzymes Allows Them to Catalyze Specific Reactions– The cycle of enzyme-substrate interactions

(p. 80)


substrates

active siteof enzyme

enzyme



• The Activity of Enzymes Is Influenced by Their Environment

• The 3-D structure (like proteins last year)

• i.e. the salty brine in pickles keeps the enzymes in bacteria working – so they can’t attack and break down the cucumbers.


Chapter 6

• Capturing Solar Energy: Photosynthesis

• Remember…sunlight is the source of all (>99%)

• (look at solar spectra graph pg 88.)


• Everything from Gamma rays to Radio waves come out of the sun, but we are most interested in the peak of this energy… which is in the visible light portion of the electromagnetic spectrum


What Is Photosynthesis?

• Photosynthesis Converts Carbon Dioxide and Water to Glucose (simple sugars)

• Remember – trees/grass etc. are solidified air…CO2 !

• Plant Photosynthesis Takes Place in Leaves– Figure 6.1 An overview of photosynthetic

structures (p. 86) – Stomata (stoma cingular) = holes or breathing– mesophyll where photosynthesis occurs


internal leaf structure

mesophyllcells

chloroplasts

vein

stoma

channelinterconnectingthylakoids

stroma

outer membrane

inner membrane

thylakoid

chloroplast in mesophyll cell



internal leaf structure

mesophyllcells

chloroplasts

vein

stoma


channelinterconnectingthylakoids

stroma

outer membrane

inner membrane

thylakoid

chloroplast in mesophyll cell


What Is Photosynthesis?• Leaf Cells Contain Chloroplasts – these are the organelles in

which photosynthesis occurs.• Photosynthesis Consists of Light-Dependent and Light-

Independent Reactions – light dependent reactions – thylakoids capture sunlight energy and convert

some of it into chemical energy • these molecules = ATP (adenosine triphosphate (ATP))• and the electron carrier NADPH (nicotinamide adenine dinucleotide

phosphate)• Oxygen is producted

– light independent reactions – enzymes in the stroma use the chemical energy above to make glucose (sugars/starch) or other organic molecules


LIGHT-DEPENDENTREACTIONS(thylakoids)

depletedcarriers

(ADP, NADP+)

energizedcarriers

(ATP, NADPH)

LIGHT-INDEPENDENTREACTIONS

(stroma)glucoseCO2 + H2O

H2O O2


How Is Light Energy Converted to Chemical

Energy?• Light, chloroplast pigments, and

photosynthesis (p. 88) • (next image) Chlorophyll strongly absorbs

violet, blue and red light (reflects green -looking green)

• Carotenoids absorb blue and green (reflects orange looking orange –visible in the fall when the leaves die, the green fades first)


Visible light (“rainbow colors”)

Absorbance of photosynthetic pigments

Gamma rays X-rays UV Infrared Micro-waves

Radiowaves

Visible light

carotenoids

chlorophyll


Visible light (“rainbow colors”)

Gamma rays X-rays UV InfraredMicro-waves

Radiowaves

Visible light


Absorbance of photosynthetic pigments

carotenoids

chlorophyll



Energy?• Light Energy Is First Captured by Pigments

in Chloroplasts• The Light-Dependent Reactions Generate

Energy-Carrier Molecules– Light, chloroplast pigments, and photosynthesis

(p. 88) – PS I= photosynthesis process 1– PSII= photosynthesis process 2– ETC = Electron Transport Chain


thylakoids

chloroplast

within thylakoid membrane

ETCPS IETCPS II

reaction centers



Energy?– Photosystem II Generates ATP (one of our

energy carriers)


Photosystems – away!

• Photosystem I Generates NADPH (another one of our energy transport chemicals)

• Splitting Water Maintains the Flow of Electrons through the Photosystems

(The electrons that move through the chemical reactions have to be restored somehow…water does it)


sunlight

ene

rgy

leve

l of

elec

tron

sw

ithin thylak oid

mem

branephotosystem I

photosystemII

synthesisreactioncenter

energy to drive

electron transport chain


How Is Chemical Energy Stored in Glucose Molecules?• So we have energy now… storage?• Sugars! Starches! Glucose• The Cycle Captures Carbon Dioxide

– In through the stomata (breathing)– Figure 6.4 The C3 cycle of carbon fixation (p. 90) – The output is glucose!– Memorize? No just know it exists. It’s a cycle

that takes in CO2 and outputs glucose (C6H12O6)

• RuBP step = ribulose bisphospate


6 CO26 H2O

612

RuBPPGA

C3

cycle

6

612

12

12

12

12G3P

glucose(or other organic

compounds)


What Is the Relationship between Light-Dependent and Light-Independent Reactions?

• Figure 6.5 Two sets of reactions are connected in photosynthesis (p. 91)

• Photo = light capturing part

• Synthesis = light independent part glucose


energy fromsunlight

chloroplast

glucose

Light-independentreactions(C3 cycle) occurin stroma.

Light-dependentreactions occurin thylakoids.


CO2 in and out of the forest…

• Forests both consume and emit carbon dioxide (p. 92)



How Does the Need to Conserve Water Affect

Photosynthesis?• Photosynthesis needs CO2

• But too many pores = water loss!• So stomata can open and close• = Regulation!• But…When Stomata Are Closed to Conserve

Water, Wasteful Photorespiration Occurs– Figure 6.6 Comparison of C3 and C4 plants

(p. 93) RuBP step CAN use O2 when CO2 is not available. Not good for glucose making!


C3 and C4 Plant primer

• Named by which Carbon cycle they use during photosynthesis.


C3 plants use the C3 cycle

C4 plants use the C4 pathway

within chloroplast in mesophyll cell

within chloroplast in mesophyll cell

bundle-sheathcells

bundle-sheathcells

glucose

C3

CYCLE

CO2

PGA

G3P

O2

CO2

RuBP

RuBP

C4

Pathway

CO2

CO2

CO2 O2

C3

CYCLE

glucose

PGA

G3P

pyruvate

PEP

4-carbonmolecule

within chloroplast in bundle-sheath cell


C3 plants use the C3 cycle within chloroplast in mesophyll cell

bundle-sheathcells

glucose

C3

CYCLE

CO2

PGA

G3P

O2

CO2

RuBP


C4 plants use the C4 pathway within chloroplast in mesophyll cell

within chloroplast in bundle-sheath cell

bundle-sheathcells

RuBP

C4

Pathway

CO2

CO2

C3

CYCLE

glucose

PGA

G3P

pyruvate

PEP

4-carbonmolecule

CO2 O2


How Does the Need to Conserve Water Affect Photosynthesis?• An Alternative Pathway Reduces Photorespiration in

Plants• C3 and C4 Plants Are Each Adapted to Different

Environmental Conditions• During warm dry weather can make plants open their

stoma but not be able to capture enough energy to live.

• C3 best in low light high water environments (pole-ward forests) and C4 abundant light but water is scarce (deserts)


Chapter 7 Show me the glucose!

• Harvesting Energy: Glycolysis and Cellular Respiration

• To power chemical reactions in the cell, the most common energy-carrier is ATP (adenosine triphosphate).


What Is the Source of a Cell’s Energy?

• Glucose Is a Key Energy-Storage Molecule (other chemicals work, but glucose it’s the main player)

• Photosynthesis Is the Ultimate Source of Cellular Energy

• Glucose Metabolism and Photosynthesis Are Complementary Processes– Energy+water+carbon dioxide glucose + oxygen

Photosynthesis– glucose + oxygen energy + water + carbon dioxide

Glucose Metabolism


How Do Cells Harvest Energy from Glucose?

• An overview of glucose metabolism (p. 101)

• Step 1 = Glycolysis (w/ or w/o oxygen) makes pyruvate (releases chemical energy -ATP)

• Step 2 = Cellular respiration (w/oxygen) or Fermentation (w/o oxygen)

• Step 3 = w/oxygen pyruvate enters the mitochondria CO2 and water + lots of ATP

w/o oxygen, doesn’t enter the mitochondria and is made into lactate or ethanol and no ATP


(cytoplasm)

glucose

Glycolysis 2

2

2

2 2

2

2

2

lactateor

ethanolFermentation

Cellular respiration

CO2CO2

CO24

32 or 34

acetyl CoA

electroncarriers

Krebscycle

Electrontransport chain

(mitochondrion)

intermembranecompartmentH2O

O2

pyruvate


What Happens During Glycolysis?

• The essentials of glycolysis (p. 101)

• Glycolysis makes only 2 ATP (energy transporters) and two NADH (energy transporters using the electron carrier)

(NADH = nicotinamide adenine dinucleotide)

• (The next image is a expansion of Step 1 above)


2 2

2 2

2

4 4

2

glucose fructosebisphosphate

pyruvateG3P

Glucose activation Energy harvest1 2


7.3 What Happens During Glycolysis?

• Activation Consumes Energy– The first part of the reaction

• Energy Harvest Yields Energy-Carrier Molecules– The second part of the reaction– Essential for life


What Happens During Cellular Respiration?

• Cellular respiration (p. 103) Step 2 above.

• When you break it down… it is a bit complex

• Look for the parts you recognize…

• (Follow 1 8)


mitochondrion

innermembrane

outermembrane

intermembranecompartment

matrix

cristae

glucose

2 pyruvate

(cytoplasm)

(intermembranecompartment)

(inner membrane)

coenzyme A

acetyl CoA

(matrix)

Krebscycle

energizedelectroncarriers

depleted carriers(outer membrane)

Electrontransportchain

CO2

CO2

H2O

H+

2 H+

H+

H+

H+

H+

H+

H+

H+

2e–

2e–

1/2 O

Glycolysis

1

8

6

43

5

7

2



• The Krebs Cycle Breaks Down Pyruvate (from Step 1) in the Mitochondrial Matrix– The reactions in the mitochondrial matrix

(p. 104) – The Krebs cycle is also called the citric-acid

cycle since citrate is formed first…– (More detail than we’ll quiz on)


Formation ofacetyl CoA

pyruvate

coenzyme Acoenzyme A

Krebscycle

3

3

2 CO2

CO2

acetyl CoA

1

2



• Energetic Electrons Are Carried to Electron Transport Chains– Table 7.1 Summary of Glycolysis and

Cellular Respiration (p. 105) – Remember, we are looking for ways to

make the life important energy transporters– Figure 7.5 The electron transport chain in

the inner mitochondrial membrane (p. 104)



(matrix)

(innermembrane)

synthesisenergy to drive

electroncarriers

(intermembrane compartment)

2e–

2e–

H+H+H+

1/2 O2 + 2H+

H2O

2

1

3



• Notice that there is Hydrogen (freed from the water) moving out at different steps of this respiration process (image back a slide)

• The cell gets more energy from a Hydrogen-Ion Gradient which Is Used to Produce yet more ATP


What Happens During Fermentation?

• We don’t have oxygen (or enough oxygen) present.

• Some Cells Ferment Pyruvate to Form Alcohol (woo hoo)– Glycolysis followed by alcoholic

fermentation (p. 106) – Don’t get enough oxygen (in bread for

instance) and you get Fermentation (p. 107) byproducts


Glycolysis followed byalcoholic fermentation

glucose pyruvate ethanol(glycolysis) (fermentation)

2 2 2

2 2

CO2

regeneration




What Happens During Fermentation?

• Other Cells Ferment Pyruvate to Lactate– You also get lactic acid as a byproduct– Glycolysis followed by lactate fermentation

(p. 106)



Glycolysis followed bylactate fermentation

glucose pyruvate lactate(glycolysis) (fermentation)

2 2

2 2

regeneration


Next time…

• Chapters 8,9,10,11,12

• DNA• Gene expression and regulation• How cells reproduce• Patterns of Inheritance• Biotechnology

Documents

Copyright © 2006 Pearson Prentice Hall, Inc. Intro to Biology Week 2 Energy in Cells, Capturing Energy and Harvesting Energy – Glycolysis, and Cellular