UNIT 2Lecture 6

Metabolism

Unit 2:Life’s Energy Sources and Conversions

• Metabolism• Cellular Respiration: Sugar ATP• Photosynthesis: Light Sugar

Key Themes

• Energy acquisition & conversions in metabolism

The Molecules of Life

Structure-Function Relationship

Life’s Energy Conversions

An organism’s metabolism is the total of the organism’s chemical reactions

•Two types of reactions:

– Big molecule Several small molecules• Releases energy

– Small molecules Big molecule • Requires energy

Metabolism

An organism’s metabolism is total of the organism’s chemical reactions

•Two types of reactions:– Big molecule Several small molecules

• Releases energy

• This sounds like:a) Cellular respiration

b) Photosynthesis

c) Neither

Metabolism

Order and Chaos

Nature “wants” to be random/chaotic

Mydesigningsolutions.com; bedroomdisaster.blogspot.com; fritolay.com; slashfood.com

Energy

Energy

Order and Chaos

Nature “wants” to be random/chaotic

Mydesigningsolutions.com; bedroomdisaster.blogspot.com; fritolay.com; slashfood.com

Energy

Energy

A complex, ordered molecule

Several small, disordered molecules

A complex, ordered molecule

Several small, disordered molecules

Newenergyandfuel.com; ualberta.ca; all-water.org

Energy

Requires

Releases

GlucoseCO2 H2O

Fig. 8-6Reactants

Energy

En

erg

y

Products

Amount ofenergy

released

Progress of the reaction

(a) Energy-releasing reactions

Products

ReactantsEnergy

En

erg

y

Amount ofenergy

required

(b) Energy-requiring reactions

Progress of the reaction

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 + H2OCellular respiration

in mitochondria

Organicmolecules+ O2

ATP then powers cellular work

Heatenergy

ATP

Fig. 9.2Ecosystem energy flow 1. Be able to

link producers and consumers via cycles of energy and carbon flow

ATP

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 + H2OCellular respiration

in mitochondria

Organicmolecules+ O2

ATP then powers cellular work

Heatenergy

ATP

Fig. 9.2Energy flowin ecosystems

1. Be able to link producers and consumers via cycles of energy and carbon flow

ATP

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 + H2OCellular respiration

in mitochondria

Organicmolecules+ O2

ATP then powers cellular work

Heatenergy

ATP

Fig. 9.2Energy flowin ecosystems

ATP

Newenergyandfuel.com; ualberta.ca; all-water.org

Energy

Requires

Releases

GlucoseCO2 H2O

Chaos = Entropy

Low Entropy System(less random, more ordered) High Entropy System

(more random, less ordered)

Newenergyandfuel.com; ualberta.ca; all-water.org

Energy

Requires

Releases

GlucoseCO2 H2O

Potential energy is stored in chemical bonds (C-H especially)

Chemicalenergy

Heat CO2

H2O

+

Cells’ ability to store energy in chemical bonds is what makes organisms and ecosystems function

Chemicalenergy

Heat CO2

H2O

+

Cells’ ability to store energy in chemical bonds is what makes organisms and ecosystems function

Without photosynthesis…

There is no way to convert light

energy into chemical energy

What about cellular respiration?

Chemicalenergy

Heat CO2

H2O

+

Without cellular respiration:A. Nothing could liveB. No animals could liveC. Nothing non-

photosynthetic could liveD. Everything could live

Where does energy go?

Where does energy go in an ecosystem?

• Heat, growth, reproduction, etc.

Heat Heat Heat

Heat

Trophic levels: Energy Flow Through Ecosystem

http://www.britannica.com/EBchecked/media/15/Transfer-of-

energy-through-an-ecosystem

5 minute break

Energy for all cellular work is provided by the same energy-rich compound:

ATP (adenosine triphosphate)

A cell (in any organism) constantly performs work that requires energy:

ATP

Fig. 8.8

ATP consists of three phosphate groups, a sugar, and a nitrogenous base.

What does that sound like?A) a triglycerideB) a nucleotideC) a phospholipidD) a trisaccharide

A = adenineA + Ribose = adenosine

adenosine mono-phosphate (AMP)

adenosine di-phosphate (ADP)adenosine tri-phosphate (ATP)

Each nucleotide is composed of: a monosaccharide sugar, a phosphate group,

and a (N-containing) nitrogenous base

(b) Nucleotide

Nitrogenousbase

Phosphategroup Sugar

Fig. 5.27

Fig. 8.8

ATP takes the energy released from the breakdown of energy-rich food molecules

and does cellular work

P iADP+

Energy frombreakdown ofenergy-rich molecules

Energy for cellularwork

ATP + H2OEnergy loaded onto

ATPEnergy released from

ATP

Fig. 8.12

Fig. 8-9

Inorganic phosphate

Energy

Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)

P P

P P P

P ++

H2O

i

Fig. 8.8

ATP: Energy carrier

“Phosphorylated” (=energized!)

molecule+ Lower

Energy

Higher Energy

Fig. 8.11 (b)See Campbell Figures 50.27 & 50.29 for additional details on muscle contraction.

ATP transfers phosphate group to motor protein(phosphorylated motor protein = energized)

Pi

ADP

+

Vesicle Cytoskeletal track

Motor protein Protein moved

ATP

ATP

High-energy P transferred to motor proteins for mechanical work

High-energy P transferred to transport proteins for transport work

Membrane protein (Na+/K+ pump)

Pi

ADP

+

P

Na+ Na+ moved uphill

Pi

ATP Fig. 8.11 (a); see also Fig. 7.16 for more detail

Na+/K+ Pump

• Cells want to pump Na+ out

• Cells want to pump K+ in

K+

Na+

ATP

Active transport and the sodium-potassium pump

Both Na+ and K+ are moved AGAINST their concentration gradient

http://www.colorado.edu/ebio/genbio/07_16ActiveTransport_A.html

See Fig. 7.16 for a six panel, blow-by-blowdescription of the sodium-potassium pump.

8. Be able to apply the principal features and functions of an ATP-fueled ion pump to the Na+/K+ pump

http://onlinephys.com/circuit1.html

Fig.8.7

http://onlinephys.com/circuit1.html

ATP fuels the Na+/K+ pumpNa+ accumulates “on top of the hill” (against its concentration gradient)

Na+ flows downhill again

Releasing useful energy

Cotransport: Using potential energy

ATP

Na+

ATP fuels the Na+/K+ pumpNa+ accumulates “on top of the hill” (against its concentration gradient)

Na+ flows downhill again

Releasing useful energy

Cotransport: Using potential energy

ATP

Na+

POTENTIAL ENERGY

35

Cotransport: Using potential energy

This potential energy can be used… To transport other molecules

AGAINST their concentration gradient

The Na+ gradient built up by the Na+/K+ pump also fuels the secondary active transport

of glucose (& other substances) AGAINST their concentration gradient

In Na+/glucose co-transport, Na+ flows back downhill & drags glucose

uphill AGAINST its concentration gradient

What provides the energy for the uphill transport of Na+ against its concentration gradient?A)No energy is needed.B)the Na+/K+ transport protein itselfC)ADP and PiD)ATP

What provides the energy for the Na+/glucose cotransporter?A)No energy is needed.B)the Na+ gradientC)ATP as a direct energy sourceD)ATP as an indirect energy sourceE)B and D

High-energy P transferred to transport proteins for transport work

Membrane protein (Na+/K+ pump)

Pi

ADP

+

P

Na+ Na+ moved uphill

Pi

ATP Fig. 8.11 (a); see also Fig. 7.16 for more detail41

High-energy P transferred to reactant molecules for chemical work

Fig. 8.10 (b)

(Ammonia displacesphosphate group,forming the amino acidglutamine.)

PP

GluNH3

NH2

Glu i

GluADP+

P

ATP+

+

Glu

(ATP adds phosphategroup to glutamic acid,making it less stable.)

+

1. Mechanical work

2. Transport work

3. Chemical work

Energy for all 3 types of work provided by:

ATP (adenosine triphosphate)

Summary: To stay alive, living cell performs 3 kinds of work that require energy:

• ATP is too unstable to serve as an actual

storage form of energy.

• Therefore, C-H bonds in macromolecules (e.g. sugars) are instead used for energy storage.

Photosynthesis:

Respiration:

ATP

Since ATP is too unstable,

C-H bonds in sugars are used for energy storage.

Converts solar energy

to ATP and uses ATP to make sugars

Converts the energy of sugars back to ATP as needed.

Sugar [CH2O]x + O2CO2 + H20

ATPLight (energy)

http://www.youtube.com/watch?v=00jbG_cfGuQ&feature=relmfu

Hank’s crash course in ATP0-3:30

Key Themes

(2) “Think Like a Biologist”: Understand What Life Is.“Unity” of life: What are common features of eukaryotes?

Energy conversions: Sugar breakdown & mitochondrial ATP formation

Food-to-Energy

Fig. 9.1

Fig. 8.3

Respiration

Cellular respiration breaks down energy-rich molecules to CO2 & water, extracting their energy.

Fig. 9.2

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 + H2OCellular respiration

in mitochondria

Organicmolecules+ O2

ATP powers most cellular work

Heatenergy

ATP

High energy

Low energy

C-H bond!

“burned” with O2 to formH2O + CO2

Photosynthesis:

Respiration:

ATP

Since ATP is too unstable,

C-H bonds in sugars are used for energy storage.

Converts solar energy

to ATP and uses ATP to make sugars

Converts the energy of sugars back to ATP as needed.

Sugar [CH2O]x + O2CO2 + H20

ATPLight (energy)

Today’s Exit Ticket

• In a few sentences:– Describe energy-releasing and energy-

requiring reactions. – Use the creation and use of ATP for cellular

work as examples of these reactions.– Be sure to use the word “entropy.”