Chapter 8

Photosynthesis

Group 6: Hope Crawn, Olivia Katulka, Kayla

Perlis.

Energy and Life

• Energy-is the ability to do work.

Almost every activity and living thing needs energy.

When you sleep your cells are using energy to build new proteins and amino acids.

•Energy comes from light, heat, and electricity

•Energy can be stored in compounds.

•Ex: When a candle burns, carbon and hydrogen in the wax combine with oxygen from the air to produce water and carbon dioxide. This process releases heat to light energy.

•Living things get energy from what

they eat. • Plants and some other organisms are able to

use light energy from the sun to produce food.

.

•Autotrophs-plants and some other organisms make their own food

• Heterotrophs- they can not use the sun’s direct energy to make food, so they get their energy from what they consume.

Autotrophs and Heterotrophs

Impalas get their energy by eating grass ; (heterotroph) Leopard gets its

energy by eating impalas and other animals. (heterotroph)

Grass is an autotroph; it makes its own food.

http://www.ucmp.berkeley.edu/bacteria/nostoc.gif

ATP and ADP

ATP and ADP

ATP – chemical compound that stores energy; (adenosine triphosphate)• consist of nitrogen- containing compound, adenine, a 5-carbon sugar- ribose, and three phosphate groups. ADP- similar to ATP but one key difference- two phosphate groups instead of three. Key difference to energy storage in cells. When a cell has energy available, it will add a phosphate group, making ATP.

Releasing Energy ATPEnergy is released when ATP is

converted into ADP plus one phosphate group. By adding and subtracting a

phosphate group, it allows a cell to store and release energy.

• ATP- enough energy for cellular activities.

• ATP is also a good molecule for a basic energy source in many cells.

Biochemical EnergyHow Cells use ATP• active transport•“sodium- potassium pump” • enough energy to move three sodium ions and two potassium out in different directions.• movement within the cell. •Cell organelles move along microtubules that use the energy of ATP.

ATP and Glucose• ATP is not good for storing large amounts

of energy over time, which is why it only accounts for a few minutes of activity.

• Sugar glucose stores 90x more the energy than a molecule of ATP.

• Efficient for cells to keep a small supply of ATP, and use carbohydrates more

frequently.

Section 8-2 Photosynthesis- An overview

Key Concepts

What is photosynthesis?

Photosynthesis is a series of reactions that uses energy from the sun to convert water and carbon dioxide into sugars and oxygen.

Photosynthesis takes place in the chloroplast of a plant cell.

Photosynthesis is a series of reactions that uses energy from the sun to convert water and carbon dioxide into sugars and oxygen.

Photosynthesis takes place in the chloroplast of a plant cell.

Chloroplast

Investigating Photosynthesis

Jan van Helmont He concluded that trees gain most of their mass from water!

Investigating PhotosynthesisJan van Helmont

Biography: (1577 – 1644)Van Helmont is a Belgian Physician, he also was an alchemist because he believed in magic, but became a chemist with his belief in the

indestructibility of matter and his balance in chemical work. His work with gases made him “the real father of pneumatic chemistry.”

His willow tree experiment ‘proved’ that water could be converted into other forms of water.

Experiment: - Helmont wondered if plants would still grow if he took material out of the soil .

-First he determined the mass of a pot of dry soil and a small willow tree seedling. -Helmont then planted the seedling in the pot and watered the plant for five years.

After five years , the willow tree grew to 75 kg. However, the mass of the soil remained almost unchanged.

Conclusion: He proved that most of the mass that the plant gained came from the water, since it was the only thing he gave the plant over the 5 years.

*Helmont’s experiment accounted for the “hydrate” or water portion of the carbohydrate produced by photosynthesis. He did not realized at the time that the carbon dioxide in the air played a role in the growth and mass of the willow tree.

Priestly’s Experiment“I have discovered an air five or six times as good as common air.”

Biography: Joseph Priestly was an English minister who made an important discovery that was another important step

to discovering the process of photosynthesis. Priestly’s experiment came 100 years after Helmont’s. In fact his

experiment took place in 1771, just five years before the U.S. Declaration of Independence was signed!

Experiment: Priestley took a lit candle, placed it under a jar and watched the flame die out. Priestly realized that

something was needed to keep a candle flame burning. This was oxygen and when it ran out the candle would die out too. - Priestly then placed a live spring of mint under the jar for a

few days. -He discovered that the candle could be relighted and

remained lighted for awhile. The mint plant had produced oxygen, which the candle flame needed in order to continue

burning.

Conclusion: Plants release oxygen!!!

Other Important Scientists:

Julius Robert Mayer He proposes that plants convert light energy into chemical energy

Samuel Ruben and Martin Kamen Use isotopes to determine that the oxygen liberated in photosynthesis comes from water.

Melvin Calvin traces the chemical path that carbon uses to form glucose. Calvin Cycle!

Rudolph Marcus He wins the Nobel Prize in chemistry for describing, in detail, the transfer of electron process in the electron transport chain.

light6CO2 + 6H2O C6H12O6 + 6O2

lightcarbon dioxide + water sugar + oxygen

Photosynthesis’s final products:6-cabon sugars (C6 H12 O6).

The Photosynthesis Equation

• Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars. Plants then will use these sugars to produce complex carbs. Ex: starches. Plants also obtain carbon dioxide from the air or water where they grow.

• Stomata- carbon dioxide is gained and oxygen released through these pores.

• Water is obtained by the plant through the roots and is then delivered to the leaves through vascular plant tissue systems.

• Sunlight is absorbed through chlorophyll, a green pigment in the chloroplasts if a plant cell.

*Photosynthesis requires not just water and carbon dioxide, but light

and chlorophyll- a molecule in chloroplasts, as well.

Plants use these low-energy raw materials, water and CO2, to produce

high-energy sugars.

Sunlight is energy from the sun that travels in the form of light. Sunlight may

look “white” to the human eye, but it actually has a mixture of different

wavelengths of light. Visible Spectrum- wavelengths that are

visible to the eye; seen as different colors.

Pigments: light absorbing molecule A plant’s pigment is known as chlorophyll- principal pigment of plants and other photosynthetic organisms; captures light energy.

Two main types:• Chlorophyll a•Chlorophyll b

Chlorophyll

Chlorophyll a- structure is CH3

Chlorophyll b- structure is CHO

Both types of chlorophyll are associated with integral membrane proteins. Both absorb light strongly in the violet and red parts of the spectrum. Difference: the difference is in there structure!!! ( as seen above)

• Structure in chloroplasts. Pigments that contain red to yellow ranging colors.

• Absorb light the strongest in the blue portion of the spectrum. trap more energy

• carotenoids are a major pigment in flowers and fruits • ex: red tomato, orange carrot • In the autumn, when the amount of chlorophyll in a leave

decreases, the carotenoids become visible. This is why leaves turn red and yellow!

This is a diagram of beta-carotene, one of the most abundant carotenoids

• Chlorophyll absorbs light very well in the violet/blue and red region of the spectrum. Light is not absorbed well in the green region.

this is why plants are green!

When chlorophyll absorbs light, most of the energy is transferred directly to electrons, raising the electron’s energy level! High energy electrons- allow photosynthesis to work!

Action and Absorption SpectraAction spectrum - the rate of physiological activity of

something plotted against wavelengths of light. Absorption spectrum- spectrum of radiant energy that’s

intensity under wavelengths is a measurement of the amount of energy at that wavelength that is absorbed in an

absorbing substance. spectrophotometer- measures the amount of radiant

energy absorbed in a substance.

Action Spectrum

Absorption Spectrum

1800-1900 : biologists discovered the requirements of photosynthesis .

- allows plants to use the energy of sunlight to produce carbohydrates

- photosynthesis takes place inside the chloroplast- thylakoids - saclike photosynthesis membranes that are in chloroplast.-Thylakoids are arranged in stacks know as grana; thylakoids contain cluster of chlorophyll , other pigments , and proteins know as photosystems

Two stages that the reactions are broken down into- light-dependent reactions ( take place in the thylakoid membranes)- light- independent reactions also know as the Calvin cycleCalvin (takes place in the stroma- area outside of the thylakoid membranes.)

NADPH

ATP

Light-Dependent Reactions

Sugars

NADP+

ADP + P

Chloroplast

O2

Light CO2

electrons gain a lot of energy when sunlight excites the electrons from the chlorophyll - compound molecule - compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule

NADP+ (nicotinamide adenine dinucleotide phosphate)- hold 2 high-energy electrons and a H+ ion - NADP+ converts into NADPH when it takes the two electrons. - carries high-energy electrons produced by light absorption in chlorophyll to chemical reactions in the cell .- used to help build molecules that the cell needs (carbohydrates – such as glucose)

Light Department Reactions - produces oxygen gas and convert ADP and NADH into the energy carriers ATP and NADPH. Takes place in thylakoid membranes !•(A) Photosynthesis begins when the pigments in photosystems II absorb light energy from the light is absorbed by the electrons , which increases their energy. - electrons passed on electron transport chain *chlorophyll does not run out of electrons because thylakoid membrane breaks water molecules, H2O into 2 H+ ions and 1 oxygen atom. 2 electrons replace the high-energy ones that chlorophyll has lost to the electron transport chain.

•(B) high-energy electrons go on the electron transport chain from photosystem I- photosystem II - energy from electrons powers the electron transport chain so it can transport H+ ions from the stroma to the inner thylakoid.

Light- Dependent Reactions• (C.) Pigments in photosystem I reenergize the electrons. - NADP+ becomes NADPH when it picks up electrons and a H+ ion

• (D) When H+ ions are released, he outcome is the inside of the thylakoid membrane is positively charged and the outside is now negative.

- this allows there to be energy to make ATP

• (E) ATP synthase- proteins where H+ ions pass through because they cannot just pass through the membrane.

-H+ ions pass through this and the protein rotates. While rotating, it bind ADP and a phosphate group to form ATP.

InnerThylakoidSpace

ThylakoidMembrane

ATP Formation

Stroma

Photosystem IIHydrogenIon Movement

Electron Transport Chain Photosystem I

* Match the letters to those on the previous slides to better understand the diagram.

Calvin cycle was named after American scientist Melvin Calvin, who made the details of this cycle

The Calvin Cycle is the pathway found in the stroma of the chloroplast , where the carbon enters into the form of CO2

and leaves in the form of a sugar

- Does not contain light

• (A) The cycle begins when 6 carbon dioxide molecules + six 5- carbon molecules twelve 3-carbon molecules.

• (B) ATP and high energy electrons from NADHP give energy and allow twelve 3- carbon molecules to convert into higher energy substances.

• (C.) two of the twelve 3- carbon molecules are converted into similar 3- carbon molecules. This product will later be used to form 6- carbon sugars.

• (D) remaining ten 3-carbon sugars converted into 5- carbon molecules; used in the next cycle.

CO2 Enters the Cycle

5-CarbonMoleculesRegenerate

6-Carbon SugarProduced

* Use the letters in the previous slides and match them up with the letters in this slide to get a better understanding of the steps in the Calvin Cycle.

Calvin cycle uses six molecules of carbon dioxide that produces a single 6-carbon sugar molecule. - it then gets rid of the energy sugars and removes the carbon dioxide from the atmosphere - plants then use these sugars for the energy and also to build more complex carbohydrates , such as starches and cellulose.

- storage of water can slow down the or stop photosynthesis- temperature below or above 0oC and 35oC can damage the enzymes - very low temperatures may make it stop all the way- light can increase the rate of photosynthesis damage

plants, algae, phytoplankton, certain bacteria, and certain protists can all go through photosynthesis.

Review!1. Explain the difference between ATP and ADP. Include what

advantages ATP has over ADP.2. What are the reactants and products in photosynthesis.3. How are Priestly, Helmont, and Ingenhousz’s discoveries all

important to the discovery of the full photosynthesis reaction?4. Explain the similarities and differences between the two types of

chlorophyll.5. What are carotenoids? 6. Explain light dependent reactions and where they occur.7. Explain the Calvin Cycle and where it occurs. 8. What are some key organisms that go through photosynthesis.9. Draw a diagram with autotrophs and heterotrophs.

• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Chlorophyll.html

• http://mattson.creighton.edu/History_Gas_Chemistry/vanHelmont.html

• http://www.phschool.com • http://biology.about.com/od/plantbiology/a/aa050605a.htm• http://bioenergy.asu.edu/photosyn/education/photointro.html• http://www.biography.com/people/jan-ingenhousz-9349309 • http://www.phschool.com/webcodes10/index.cfm?

fuseaction=home.gotoWebCode&wcprefix=cbk&wcsuffix=9999 • http://www.ucmp.berkeley.edu/bacteria/cyanolh.html • http://earthobservatory.nasa.gov/Features/Phytoplankton/ *Prentice Hall Biology Book

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