METABOLISMThe sum of all chemical

reactions in an organism.

A. ANABOLIC = Involves building larger molecules from smaller ones (these are endergonic)

2 Kinds of Metabolic Reactions

Amino Acid + Amino Acid + Amino Acid Protein

B. CATABOLIC = Involves breaking down larger molecules into smaller ones (these are typically exergonic)

Protein Amino Acid + Amino Acid + Amino Acid

ENERGY FOR LIFEENERGY is defined as, The ability to do

WORK2 Kinds of energy

1. POTENTIAL ENERGY- Stored energy eg. Energy stored in food

2. KINETIC ENERGY- Energy of Motion eg. Moving organism

Did you see evidence of Kinetic Energy?

Time Lapse of Raddish Seed Germination

What is the source of the Kinetic Energy?

Exergonic and Endergonic Reactions in Metabolism

• An exergonic reaction proceeds with a net release of free energy and is spontaneous

• An endergonic reaction absorbs free energy from its surroundings and is nonspontaneous

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Exergonic Reaction

Exergonic Reaction

Endergonic Reaction

Where Does the Energy Come From For Activation And To Drive Endergonic Reactions?

ATPAdenosine Triphosphate

Where Does ATP Come From?

It’s Made By Cells Using one of Two Methods

A. PHOTOSYNTHESIS

and B. RESPIRATION

Energy Processes

• In photosynthesis, the products of one reaction get consumed in the next reaction. This series of reactions is called a biochemical pathway.

– Almost like many assembly lines connected together

• Equation for photosynthesis Carbon Dioxide + Water -> Oxygen + Biomolecules

(carbos. )

Algae changes the world

• Early Earth had an atmosphere with no oxygen in it

• The only living things emitted oxygen as a waste product

• This changed the atmosphere

• Ironically, those species died

chloroplasts

• Chloroplasts absorb light

• Flattened discs inside are called thylakoids

• Stacks of thylakoids = granum

• Fluid that all this is sitting in = stroma

Lights, Chlorophyll, Action

• We see energy of different wavelengths as different kinds of color

• Pigments are compounds that absorb light

• If a color is absorbed it doesn’t reflect

• The color black absorbs most of the colors

Pigments

• Chlorophyll is a pigment– It comes in two kinds a and b

• a absorbs more red light than b• b only helps a so its an accessory pigment• Green light is reflected from chlorophylls so

plants appear green

absorption spectra of photosynthetic pigments

Other pigments

• Carotenoids absorb other colors and reflect earth tones

• You don’t normally see it until chlorophyll dies• When does that happen during the year?

Converting light Chemical Energy

• Pigments capture light• We’re going to store it in ATP & NADPH

– Oxygen is a waste product of this reaction

• Pigments are clustered in photosystems

Steps of photosynthesis1. Electrons get excited in photosystem II, and they

want to leave.2. Primary electron acceptor is sitting next to

photosystem II, waiting to take those electrons3. There’s a chain of molecules waiting to grab these

electrons. Together, they’re all called the electron transport chain.

• Energy from this is used to make a concentration gradient of H+

4. More light comes into another photosystem, photosystem I, another set of electrons start getting passed along

5. Finally energy from the electrons getting passed along is used to put a hydrogen on NADP+ making it NADPH

Electron transport, simplified a little

All going on in a thylakoid1. Chlorophyll a molecules in Photosystem II get

excited from light2. e- are passed to the primary e- acceptor3. e- go down an electron transport chain4. These e- come into Photosystem I because

Photosystem I just gave away a pair5. Another electron transport chain combines NADP+

with a Hydrogen atom to get NADPHNote where water gets split in all of this

CHEMIOSMOSISCreating ATP using a membrane protein

Chemiosmosis

• Part of the light reactions is the creation of ATP

• The energy for this comes from the concentration gradient of Hydrogen protons (H+)

• There are more H+ inside the cell than outside• ATP Synthase lets H+ out and harnesses energy

from that to make ATP

We can’t let the plants get away with it

• The opposite of photosynthesis is cellular respiration

• Equation for cellular respirationBiomolecules + Oxygen -> Carbon Dioxide + Water

Now You Should Be Able To:• Define Metabolism and give examples of 2 contrasting types of

metabolic reactions

• Give an example of organisms doing work • Explain how ATP performs cellular work

• Explain why an investment of activation energy is necessary to initiate the spontaneous reaction

• Describe the mechanisms by which enzymes lower activation energy

• Explain where plants get the energy they need to do their work

• Explain the role of light and pigments in photosynthesis

• Explain the role of electron carrier molecules in photosynthesis

• State the overall equation for photosynthesis

• Identify factors that affect the rate at which photosynthesis occurs