Chapter 8: Photosynthesis

Energy and Life

Rainy Day

• Suppose you earned extra money from a part-time job. You might be tempted to spend all the money, but instead, you decide to open a savings account.

• 1. What are the benefits to having a bank account?

• 2. What might you need to do if you need some of this money?

• 3. What might your body do if it has more energy than it needs to carry out its activities?

• 4. What would your body do if it needed more energy?

Energy and Life

A. Autotrophs and heterotrophs1. Autotrophs can make own food directly with aid of

the sunlight.

a. plants

2. Heterotrophs cannot make own food directly. Depends on others such as plants for food.

a. Humans

b. Mushrooms-need to decompose other organisms

Chemical NRG and ATP

• Energy=in the form of light, heat, electricity

• ATP (Adenosine Tri Phosphate)– Most important energy storing compound

ATP and ADP

• ATP (Adenosine Tri Phosphate)– Fully charged energy– Uses enzymes to break down to make energy– Energy is released when ATP breaks down to

ADP and a phosphate group

• ADP (Adenosine Di Phosphate)– Not fully charged energy– Needs enzymes to help add one more

Phosphate to make ATP

ATP and cells

• Cells use ATP when they move and during active transport

• Most cells have a little amount of ATP, enough to last for seconds.– ATP is not good at storing over a long period

of time but it is VERY efficient when used.

Glucose

• A monosaccharide sugar, C6H12O6, occurring widely in most plant and animal tissue. It is the principal circulating sugar in the blood and the major energy source of the body.

• Stores more than 90 times more chemical energy than ATP

• Cells can get ATP and ADP from carbs.

Photosynthesis

• Photosynthesis-plants use energy of the sun to make food such as, glucose.

Scientists

• van Helmont– How does a seed grow into a tree?

• Weighed a pot of soil and seed = 5 kg• Watered for 5 years• Seed gained about 75 kg• The soil was unchanged throughout• He concluded that water made the seed grow into

a tree.

Is that all that is needed to make plants grow?

NO!!! Plants need:

REACTANTS PRODUCTS

Scientists continued…

• Priestly– Joseph Priestly (1733 – 1804)

    Priestly was a Unitarian minister and chemist.  He did the following experiments:

– Summary:– burning candle + bell jar →  candle goes out +

add a mint plant  →  candle can be relit – mouse + bell jar →  dead mouse + add a mint

plant →  mouse lives

For the visual learner

Questions

• Why did the candle burn out when placed under bell jar?

• Why could the candle be relit after allowing it growth with a mint plant?

• Why does a mouse die when it is placed under a bell jar?

• Why was the mouse able to survive when placed in the jar with a mint plant?

• Assuming a supply of water was available to both mint plant and mouse; could the mouse and plant survive indefinitely under the jar?  Explain.

And yet…one more scientist

• Ingenhousz– Finds that aquatic plants produce oxygen

bubbles in the light but not in the dark. – Concludes that plants need SUNLIGHT to

produce OXYGEN

Light and Pigment

• Pigment is light absorbing material– Chlorophyll– 2 types of chlorophyll

• Chlorophyll a• Chlorophyll b• Chlorophyll absorbs light in the red and blue

regions• WHY are plants green?• Other plants contain different pigments to absorb

other parts of the spectrum…ex. carotene

8.3 Rxns of Photosynthesis

• Photosynthesis takes place in the chloroplast.

Thylakoid

• Contains photosynthetic membranes– Photosystems 1 and 2

Grana

• Stack of Thylakoids

2 Stages of Photosynthesis

• 1. Light Dependent Reaction• Energy is captured to make storing compounds.• Occurs inside the photosynthetic membrane

• Thylakoid membrane• 2. Light Independent Reaction

•Does not require light directly

•Can occur in the light

•Uses stored energy from Light Rxn to make glucose in the absence of light.

•Occurs outside the photosynthetic membrane

•Stroma

Light Dependent Rxn

• 4 processes– 1. Light Absorption- photosystems capture light in

membrane– 2. Electron Transport- NADP+ (enzyme carrier that

makes NADPH) NADPH helps build molecules in the cell.

– 3. O2 Production- takes electrons from H2O forms O2 gas (released into the air)

– 4. ATP Formation- H2O splits, inside the + charges collide with the – charges outside. Produces energy to attach P+ADP=ATP.

Light Independent Rxn(Calvin Cycle or Dark Rxn)

• Calvin Cycle uses 6 molecules of CO2 to make a single 6-carbon sugar

• Plants use the sugar to make more complex carbs like starches and cellulose.

• Uses ATP and NADPH from Light Rxn to carry on Dark Rxn.

Factors affecting Photosynthesis

• Shortage of water

• Temperature

• Intensity or amount of light

Plants

• Multicellular eukaryotes

• Carry out photosynthesis using green pigments…chlorophyll a & b

What is the advantage of two different chlorophylls?

What do plants need to survive?

• Water, carbon dioxide, sunlight

How plants get nutrients

• Xylem- vascular tissue that carries water UP from the roots to every part of the plant. (xy-hi)

• Phloem- vascular tissue responsible for transport of nutrients and the carbs produced by photosynthesis. (ploe-low)

Classification

• Gymnosperms-cone bearing – Most common are: spruce, pine, firs, cedars,

evergreens.

Reproduction of Gymnosperms

• Female-actual cone • Male-pollen cones

Classification

• Angiosperm- flowering plants (flowers or fruit bearing)

Reproduction of Angiosperms

Important Terms

• Annuals- plant yearly

• Biennials- 2 years

• Perennials- through the years