Photosynthesis

Chapter 6 Biology

Energy and Life All living things need a source of energy to

live All energy originates from the sun…. Ex.) What do you plan on having for lunch

today?

Autotrophs and Heterotrophs

“Auto”- make their own food and trap energy from the sun

“Hetero”- get their energy by eating autotrophs or other heterotrophs

Energy and Life

Energy come in many forms (motion, heat, etc.)

Energy is stored in chemical bonds as potential energy…

When bonds between atoms are broken energy is released…because electrons shift from higher to lower energy levels

ATP

Cells use ATP to store energy (Adenosine Tri-phosphate)

Storing Energy? Add a phosphate group to ADP to make ATP

Release Energy? Take ATP and remove a Phosphate group, and energy is released

This energy is used for… active transport, protein synthesis, and muscle contraction

The Photosynthesis Equation

Law of conservation of matter: Matter is neither created nor destroyed…rearranged

Let’s balance this equation, why? Balancing Equations Practice…

XRAY: eggs2/ flour6/ bakingpowder2/ oil1 / water3

Go to the store

Water Oil Baking aisle: The cake mix (egg1 / flour3 /

bakingpowder1)

Now write the equation and figure out how much you need of each ingredient…

H and O makes water Write out the equation…and then balance

it –

Write out and balance the photosynthesis equation

Come to some conclusion about it…

8-2 An Overview of Photosynthesis

Plants use energy from sunlight, water and carbon dioxide, to convert it to Carbs (sugars and starches) and oxygen.

The History

Early scientists asked this question:A tiny seedling grows into a large tree- The amount of soil is the sameAnd water is the only thing that is addedWhere does all the tree’s MASS come from

then?

Van Helmont 1600’s

Grew a seedling for 5 years and kept careful records

…it gained 75kg Conclusion? All the mass came from water

Priestley 1700’s

I know : Candles can’t burn without oxygen

But…. If I place a candle under a jar with a mint sprig (plant), will the candle remain lit?

Hypothesis: Conclusion:

Ingenhousz

Improved upon Priestley’s findings Proves that this (photosynthesis) only

works in the presence of light!

Photosynthesis requires..

______ and ________ It also requires light and chlorophyll Chlorophyll absorbs light & is a pigment Light is energy… so when light is

absorbed …so is energy

Light energy’s effect on chlorophyll molecule… When chlorophyll, located inside the

chloroplasts of the leaf, traps energy from sunlight….

That energy is transferred to the electrons in the atoms of chlorophyll molecule, raising energy levels of the electrons and starting the process-

Review of Light concepts

Review of Light concepts White light contains all the colors of the

rainbow Prism can break it apart so you can see it You see because light bounces off and

object and to your eyes…in a straight line How do you see green? Red? White? Black?

(is the color being absorbed or reflected)

8-3 Light dependent vs Light independent Reactions photosynthesis includes the light-

dependent reactions as well as the Calvin cycle (light independent).

The light-dependent reactions

Split water and produce oxygen gasuse trapped sunlight energy to convert

ADP into ATPand NADP+ into NADPH

occur in the thylakoid membrane of the choloroplast

The light independent reactions use energy (ATP and NADPH) made during light-dependent reactions to produce high-energy sugars.

(ATP and NADPH can only hold energy for a few minutes, it must be stored as a sugar long term)

The Calvin cycle is also known as the light-independent reactions.

LI reactions occur in the stroma (outside the thylakoid)

American Scientist Melvin Calvin worked out the details of this cycle…

Factors that Affect Rate of Photosynthesis ….

Shortage of water (slow or stop) Ideal temp for enzymes 0-35deg C

Too cold? ph can cease Intensity of Light (winter months)

Surviving in adverse conditions Desert plants adapted- waxy covering

in order to retain water, curled leaves, etc

Surviving in adverse conditions Christmas trees (conifers) only

occasionally carry out ph in the winterThey stay green but are not

growing in the winterThe photosynthesis of most trees

is completely shut down and they are living off of the stored sugars from the summer-

http://www.cnr.vt.edu/DENDRO/forestbiology/photosynthesis.swf