Chapter 4.1:4.2:4.3Energy and Life

What is energy?

Energy is the ability to do work!

Energy• Sunlight is the main energy source for life

on Earth.

1. Cells use chemical energy in the form of a chemical compound called ATP, or adenosine triphosphate.

a. ATP contains: i. A 5-carbon sugar called ribose ii. A nitrogenous base called adenineiii. Three phosphate groups

b. The bonds between the phosphate groups store and release energy

4.1 Chemical Energy and ATP TEKS 4B, 9A

phosphate removed

• ATP transfers energy from the breakdown of food molecules to cell functions.

– Energy is released when a phosphate group is removed.

– ADP is changed into ATP when a phosphate group is added.

4.1 Chemical Energy and ATP TEKS 4B, 9A

The chemical energy used for most cell processes is carried by ATP.

• Molecules in food store chemical energy in their bonds.

Starch molecule

Glucose molecule

3. ATP is the basic energy source of all cells

4.1 Chemical Energy and ATP TEKS 4B, 9A

Organisms break down carbon-based molecules to produce ATP.

• Carbohydrates are the molecules most commonly broken down to make ATP.

– not stored in large amounts– up to 36 ATP from one

glucose molecule

triphosphateadenosine

adenosine diphosphate

tri=3

di=2

ADP ATP

Energy

EnergyAdenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP)

Partiallychargedbattery

Fullychargedbattery

c. ATP is like a rechargable battery.

Chemical Energy and ATP: Storing Energy

• Energy is stored in ATP a. ADP, adenosine diphosphate, is similar to

ATP but has two phosphate groups instead of three

b. When a cell has energy available, it can store small amounts by adding a phosphate to ADP making ATP

Using the energy

1. When a chemical bond between the 2nd and 3rd phosphates of ATP is broken, energy is released

Chemical Energy and ATP: Releasing Energy

2. ATP has enough energy to power a variety of cellular activities

A. active transport across the selectively permeable cell membrane

B. protein synthesis

C. muscle contractions

D. Propels flagella

E. Produces light in fireflies

Firefly

Escherichia coli bacterium with flagella

4. ATP is a good short term energy storage that is recycled between ADP and ATP. Cells have only a small amount of ATP.

a. It is more efficient for cells to store energy as glucose.

b. When cells need energy they make ATP from ADP using energy from glucose.

4.1 Chemical Energy and ATP TEKS 4B, 9A

• Fats store the most energy.

– 80 percent of the energy in your body– about 146 ATP from a triglyceride

• Proteins are least likely to be broken down to make ATP.

– amino acids not usually needed for energy– about the same amount of energy as a carbohydrate

ADP vs. ATP

• http://www.phschool.com/atschool/phbio/activities/cbd-3081/simbase.htm

What is the name of the molecule above?

What is the name of the part of the molecule labeled:

A? ___________________________

B? ___________________________

C? ___________________________

A

B

C

adenine

ribose

3 phospates

How does a cell get energy from this molecule?

A

B

C

By breaking the bond between the 2nd and 3rd phosphate. This releases the energy!!

What is photosynthesis?

• The process in which plants use the energy of the sun to convert water and carbon dioxide into high-energy carbohydrates (sugars and starches) and oxygen (a waste product).

4.2 Overview of Photosynthesis TEKS 4B, 9B

• Chlorophyll is a molecule that absorbs light energy.

chloroplast

leaf cell

leaf

• In plants, chlorophyll is found in organelles called chloroplasts.

4.2 Overview of Photosynthesis TEKS 4B, 9B

Photosynthesis in plants occurs in chloroplasts.

• Photosynthesis takes place in two parts of chloroplasts.– grana (thylakoids)– stroma

chloroplast

stroma

grana (thylakoids)

4.2 Overview of Photosynthesis TEKS 4B, 9B

• The light-dependent reactions capture energy from sunlight.

– take place in thylakoids– water and sunlight are needed– chlorophyll absorbs energy– energy is transferred along thylakoid membrane then to

light-independent reactions– oxygen is released

4.2 Overview of Photosynthesis TEKS 4B, 9B

• The light-independent reactions make sugars.

– take place in stroma– needs carbon dioxide from atmosphere– use energy to build a sugar in a cycle of chemical

reactions

4.2 Overview of Photosynthesis TEKS 4B, 9B

• The equation for the overall process is:

6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6

granum (stack of thylakoids)

thylakoid

sunlight

1 six-carbon sugar

6H2O

6CO2

6O2

chloroplastchloroplast1

2

43

energy

stroma (fluid outside the thylakoids)

Light Energy

Chloroplast

CO2 + H2O Sugars + O2

Light and Pigments

• Photosynthesis requires:– water– carbon dioxide– light– chlorophyll (a pigment molecule in

chloroplasts; two types)• chlorophyll a• chlorophyll b

ROYGBIV• Sunlight is perceived as white light, but is really a

mixture of different wavelengths of light (like a rainbow). The visible light we can see is a very small portion of the electromagnetic spectrum.

• Red Orange Yellow Green Blue Indigo Violet

Red: Red: longlong wavelength, wavelength, lessless energy energy

Violet: Violet: ShortShort wavelength, wavelength, highhigh energyenergy

• Pigments are molecules that absorb light at different wavelengths.

– Chlorophyll absorbs light in the visible spectrum, except the green wavelengths.

– Green light is reflected by the leaves making plants look green.

• The high energy that is absorbed makes photosynthesis work.

Factors affecting photosynthesis– Shortage of water– Temperature (0-35 degrees Celsius)– Intensity of light

Inside a Chloroplast• Photosynthesis takes place inside chloroplasts.• Chloroplasts contain:

– thylakoids: saclike photosynthetic membranes containing pigments

– grana (singular: granum): stacks of thylakoids– stroma: region of chloroplasts outside of the

thylakoid membranes– inner membrane– outer membrane

4.3 Photosynthesis in Detail TEKS 4B, 9B

• Photosystem II captures and transfers energy.

– chlorophyll absorbs energy from sunlight

– energized electrons enter electron transport chain

– water molecules are split

– oxygen is released as waste

– hydrogen ions are transported across thylakoid membrane

Electron Carriers

• Sunlight excites electrons in chlorophyll, causing them to gain energy.

• An excited electron is like a hot coal, and cannot be easily carried from one place to another- a protein called an electron carrier is required to transport excited electrons.

Electron transport: An electron carrier molecule can accept a pair of high-energy electrons and transfer them to another molecule.

– Electron transport chain: Series of electron carriers

– Example: NADP+ (nicotinamide adenine dinucleotide phosphate)

NADP+ + 2 electrons + H + NADPH

• NADPH can carry high-energy electrons to other chemical reactions in the cell that need energy

4.3 Photosynthesis in Detail TEKS 4B, 9B

• Photosystem I captures energy and produces energy-carrying molecules.

– chlorophyll absorbs energy from sunlight

– energized electrons are used to make NADPH

– NADPH is transferred to light-independent reactions

Light Dependent Reactions

• The light-dependent reaction splits water, produce oxygen gas as waste, and converts ADP and NADP+ into ATP and NADPH.

4.3 Photosynthesis in Detail TEKS 4B, 9B

The second stage of photosynthesis uses energy from the first stage to make sugars.

• Light-independent reactions occur in the stroma and use CO2 molecules.

4.3 Photosynthesis in Detail TEKS 4B, 9B

• A molecule of glucose is formed as it stores some of the energy captured from sunlight.

– carbon dioxide molecules enter the Calvin cycle– energy is added and carbon molecules are rearranged– a high-energy three-carbon molecule leaves the cycle

4.3 Photosynthesis in Detail TEKS 4B, 9B

– two three-carbon molecules bond to form a sugar

– remaining molecules stay in the cycle

• A molecule of glucose is formed as it stores some of the energy captured from sunlight.

Light Dependent Reactions

1. Light hits Photosystem II in the thylakoid membranes. Two electrons are excited and these excited electrons are passed onto the electron transport chain

a. To replace the lost electrons, the thylakoid membrane obtains low-energy electrons by splitting water 2H2O 4H+ + O2 + 2 e-

• The O2 is released as waste

• The hydrogen ions (4H+) are released inside the thylakoid membrane

Light Dependent Reactions

2. Electron transport chain (ETC)a. Electrons are passed from Photosystem II to

Photosystem I from one electron carrier to the next until they reach Photosystem I

b. Energy from the electrons is used by the electron carriers in the ETC to force H+ ions from the stroma into the inner thylakoid space- build up of H+ will be used to drive ATP synthase

Light Dependent Reactions

3. Light hits Photosystem Ia. Pigments in Photosystem I use energy from

light to energize two electrons, making them high-energy

b. They are passed to NADP+ Reductase which catalyzes the reaction of NADP+ take combining with the high-energy electrons and hydrogen ions (H+) to become NADPH

Light Dependent Reactions

4. Hydrogen Ion Movement– The inside of the thylakoid membrane fills up

with positively charged hydrogen ions (H+) as electrons are passed from Photosystem II to I

– ATP synthesis• The thylakoid membrane contains a protein called

ATP synthase that spans the membrane and allows H+ ions to pass through it

• As H+ ions pass through ATP synthase, the protein rotates and binds ADP and a phosphate group to produce ATP.

Light-independent reactions (The Calvin Cycle)

• During the Calvin cycle, plants use ATP and NADPH from the light-dependent reactions to produce high-energy sugars for long-term storage.

• The Calvin cycle does NOT require light.

Chloroplast

H2O

O2

Sugars

CO2

Light-Dependent Reactions

CalvinCycle

NADPH

ATP

ADP + P

NADP+Chloroplast

Thylakoids

light

The Calvin Cycle: (4 Steps)

1. CO2 enters the cycle

– Six carbon dioxide molecules enter and combine with six 5-Carbon molecules.

– Result: 12 3-carbon molecules

The Calvin Cycle

• Energy input– The 12 3-carbon molecules are converted into

high energy forms using ATP and NADPH• During this process, 12 ATP 12 ADP• During this process, 12 NADPH 12 NADP+

The Calvin Cycle

• 6-carbon sugar produced from two 3-carbon molecules removed to produce sugar

• 5-carbon molecules regenerated– 10 remaining 3-carbon molecules converted

into six 5-carbon molecules– This requires 6 ATP 6 ADP– These 5-carbon molecules can be reused in

step A.

The Calvin CycleCO2 Enters the Cycle

Energy Input

6-Carbon SugarProduced

5-Carbon MoleculesRegenerated

Photosynthesis

includes

of

take place intakes place in uses

to produce to produce

use

Light-dependentreactions

Calvin cycle

Thylakoidmembranes Stroma NADPH

and ATPCO2

H2O and Energy from

sunlight

ATP NADPH O2 Chloroplasts High-energysugars

Photosynthesis

includes

of

take place intakes place in uses

to produce to produce

use

Light-dependentreactions

Calvin cycle

Thylakoidmembranes Stroma NADPHATPEnergy from

sunlight

ATP NADPH O2 Chloroplasts High-energysugars

Photosynthesis is important for almost all life on Earth because it —

A produces oxygen B uses simple elementsC is responsible for most decayD releases usable forms of nitrogen

1.What is this picture showing?

2.What is letter A? __________

3.What is letter B? __________

A

B

stroma

thylakoid

chloroplast

ChloroplastLight

O2

Sugars

CO2

Light-Dependent Reactions

CalvinCycle

NADPH

ATP

ADP + P

NADP+Chloroplast

Thylakoids

H2O

Light Dependent or Calvin Cycle?

• Occurs in the stroma• Needs CO2

• Produces ATP and NADPH• Occurs in the thylakoid membranes• Needs sunlight• Can occur in the dark• Uses ATP and NADPH• Produces a 6-Carbon Sugar

Light DependentLight DependentCalvin CycleCalvin Cycle

Light DependentLight Dependent

Light DependentLight DependentCalvin CycleCalvin CycleCalvin CycleCalvin Cycle

Calvin CycleCalvin Cycle

Calvin CycleCalvin Cycle