PHOTOSYNTHESISPHOTOSYNTHESISEnergy & LifeEnergy & Life

Biology IBiology I

Energy & LifeWhere does the energy that living things need

come from?

Plants & other organisms are able to use light energy from the sun to produce food.Organisms such as plants make their own food & are called______.Organisms such as animals can’t make their own food & are called___.

Chemical Energy & ATP

Energy comes in many forms, including light, heat, & electricity.The activities of the cell are powered by chemical fuels.One of the major chemical compounds is adenosine triphosphate (ATP.The molecule consists of a nitrogen containing compound called adenine, a 5-carbon sugar, and three phosphate groups

The ATP molecule is composed of three components. At the centre is a sugar molecule, ribose (the same sugar that forms the basis of DNA). Attached to one side of this is a base (a group consisting of linked rings of carbon and nitrogen atoms); in this case the base is adenine. The other side of the sugar is attached to a string of phosphate groups. These phosphates are the key to the activity of ATP.

The Structure

Chemical Energy cont…

ADP (adenosine diphosphate) has a similar structure to ATP, but with some differences. It has two phosphate groups.The energy storage is also differentBoth ATP & ADP both contain stored energyComparing ATP to ADP….ATP is like a fully charge battery with energy ready to be used and ADP is like a partially charged batteryEnergy stored in ATP is released when ATP is converted into ADP & a phosphate group.

Releasing Energy

Cells may use the energy for activities such as:Active transportMovement of organellesCells may regenerate ATP from ADP as needed by using energy in carbohydrates like glucose.

What is What is Photosynthesis?Photosynthesis?

It’s a series of reactions that uses light energy (photons)light energy (photons) and water (Hwater (H22O)O) to produce organic macromolecules organic macromolecules (glucose).(glucose).

6CO2 + 6H2O C6H12O6 + 6O2

Sunlight

Glucose

Where does Where does photosynthesis take photosynthesis take

place?place?

Occurs in all Occurs in all autotrophicautotrophic organisms that contain organisms that contain the green pigment the green pigment chlorophyllchlorophyll

Algae, blue-green Algae, blue-green bacteria, phytoplankton bacteria, phytoplankton ……

Leaves of plantsLeaves of plants

Chloroplasts in Chloroplasts in LeavesLeaves

ChlorophyllChlorophyll traps sunlightsunlight, the energy for photosynthesisphotosynthesis

Where in plants does Where in plants does photosynthesis photosynthesis

occur?occur?Most photosynthesisphotosynthesis takes place in mesophyll cellsmesophyll cells in the leaves of plants

Stomata(opening)

MesophyllCell

Chloroplast

Mesophyll Cells of Mesophyll Cells of LeafLeaf

Palisade Mesophyll

Spongy Mesophyll

What is the job of What is the job of Stomata (stoma)?Stomata (stoma)?

PoresPores in a plant’s cuticle through which waterwater and gasesgases are exchanged between the plant and the atmosphere. Guard

CellGuard Cell

Carbon Dioxide (CO2)

Oxygen 02

Job of the Job of the ChloroplastChloroplast

OrganelleOrganelle where photosynthesisphotosynthesis takes place.

GranumThylakoid

Stroma

Outer Membrane

Inner Membrane

Interior of a Interior of a ChloroplastChloroplast

ThylakoidsThylakoids

Thylakoid Membrane

Thylakoid SpaceGranum

Thylakoids form stacks called Granum Thylakoids form stacks called Granum which are connected to each otherwhich are connected to each other

Light & Pigments

Plants, humans, and leaves gather the sun’s energy with light absorbing molecules called pigments.Light is made of particles called photons that move in waves.Sunlight is visible as white light; you can separate white light into it’s component colors by passing the light through a prism.

Why are plants Why are plants green?green?

Chlorophyll Chlorophyll is theis the green green coloration coloration in leavesin leavesChlorophyll Chlorophyll is the molecule is the molecule that absorbsthat absorbs sunlight sunlight and and uses its energy to synthesizeuses its energy to synthesize carbohydrates from COcarbohydrates from CO22 and and waterwaterThis process is known asThis process is known as photosynthesisphotosynthesis

Chlorophyll Chlorophyll MoleculesMolecules

Located in the thylakoid membranesthylakoid membranesChlorophyll have MgMg++ in the centerChlorophyll pigmentsChlorophyll pigments harvest energy (photons) by absorbingabsorbing certain wavelengthswavelengths (blue-420 nmblue-420 nm and red-660 nm are most important)PlantsPlants are greengreen because the green wavelengthwavelength is reflectedreflected, not absorbednot absorbed

During the fall, During the fall, what causes the what causes the leaves to change leaves to change

colors?colors?As the chlorophyll in leaves As the chlorophyll in leaves decays in the autumndecays in the autumn, the , the green color green color fades and is fades and is replaced by thereplaced by the oranges oranges and reds of and reds of carotenoidscarotenoids

Photosynthetic Photosynthetic ReactionsReactions

TwoTwo main parts (reactions) main parts (reactions)Light ReactionLight Reaction or Light or Light Dependent Reaction produces Dependent Reaction produces energy from sunlight in the form energy from sunlight in the form of of ATP & NADPHATP & NADPH

Photosynthesis is a complex reaction that can be broken down

into the two following reaction systems:

light dependent & light independent or dark reactions

Light Dependent Reaction: H2O O2 + ATP + NADPH2

Water is split, giving off oxygen. This system depends on sunlight for activation energy. Light is absorbed by chlorophyll a which "excites" the electrons in the chlorophyll molecule. Electrons are passed through a series of carriers and adenosine triphosphate or ATP (energy) is produced. Takes place in the thylakoids.

Dark Reaction:         ATP + NADPH2 + CO2 C6H12O6

Carbon dioxide is split, providing carbon to make sugars. The ultimate product is glucose. While this system depends on the products from the light reactions, it does not directly require light energy. Includes the Calvin Cycle. Takes place in the stroma.

Factors Affecting Photosynthesis

Water~ major componentTemperature~ depends on enzymes that function at optimal temps.Light intensity~ increasing light will increase rate of photosynthesis