PhotosynthesisSection 1: Energy and Life

Botany is the study of plants.

What characteristics would define a plant?

8.1 Energy and Life

Energy – the ability to do work

All living things need chemical energy to survive.

The most important molecule cells use to store and release energy is ATP (adenosine triphosphate)

Chemical Energy and ATP• When an organism uses the energy

from ATP, the ATP is converted into ADP– ADP (Adenosine Diphosphate ) has

only 2 phosphate groups.– Cells can add a phosphate to ADP to

make ATP to store energy.(This requires energy)

– How is ATP and ADP similar to rechargeable batteries?

– Where do YOUR cells get the energy to convert ADP into ATP?

How could a small seed gain enough energy to grow into seed a giant tree?

Heterotroph – obtains energy from food it consumes

Autotroph – uses energy from the sun to produce food

Chemical Energy and ATP

Chemical Energy and ATP

Overall Photosynthesis Equation

6CO2 + 6H2O C6H12O6 + 6O2

LIGHT

Carbon Dioxide Water

Glucose Oxygen

Photosynthesis: the process where plants convert energy from the sun into chemical energy stored in the bonds of carbohydrates.

Chemical Energy and ATP

Light and Pigments

Light Speed, c = 2.9979 x 108 m/s

Or 670.6 million mph

How are the two types of light different? How are they similar?

Electromagnetic Spectrum

Wave length and energy are inversely proportional

The smaller the wave length, the more energy

Which type of light has more energy, the blue or the red? Explain.

Light and Pigments

Light and Pigments• What colors of light

are being absorbed?

• What colors of light are being reflected?

• What color would the object appear if there was no blue light?

• Why are plants usually green?

Spectroscope Lab

• Pigments – light absorbing molecules

• Chlorophyll – the most abundant pigment in plants, that absorbs blue and red light.– Chlorophyll a - a blue-green

pigment – Chlorophyll b - a yellow-

green pigment

Light and Pigments

• Accessory Pigments: pigments other than chlorophyll.– Carotene: orange– Xanthophyll: yellow– Anthocyanin: red

• Why do plants need accessory pigments?– They absorb light in other

regions of the spectrum

• The accessory pigments are always present in most plants but masked by the chlorophyll.

Light and Pigments

Why do leaves change color in the fall?

Answer: Shorter day lengths stop chlorophyll production, and expose accessory pigments

Light and Pigments

Photosynthesis: An Overview

• Photosynthesis takes place in the chloroplast– Thylakoids – saclike photosynthetic

membrane in the chloroplast– Grana – stacks of thylakoids– Stroma - the region outside of the

thylakoid membranes

High Energy Electrons• High energy electrons produced

by the chlorophyll are highly reactive and need a special carrier

• NADP+ accepts a pair of high energy electrons and a hydrogen ion (H+) and carriers them to a chemical reactions elsewhere in the cells.

• NADP+ NADPH

Photosynthesis: An OverviewPhotosynthesis is a complex process that can be broken

down into 2 steps:

Light-Dependent Reactions• Occurs in the thylakoid

membranes of the chloroplast.• Light energy breaks apart a

molecule of H2O– Electrons are energized and

used to convert NAD+ into NADH.

– Hydrogen ions are used to convert ADP into ATP.

– Oxygen is released as a waste product.

Light-Independent Reactions• The NADH and ATP from the

light reaction move to the stroma.

• The leaf absorbs CO2 from the atmosphere.

• The energy from the NADH and ATP is used to convert CO2 into carbohydrates.

• What is the main function of carbohydrates?

Light-Independent Reactions

• Each molecule of glucose contains enough energy to produce 36 ATP’s.

• Plants produce starch when they need to store energy.

• Starch is a long chain of glucose.

Photosynthesis and Cell Respiration• Cell Respiration is the opposite of

photosynthesis.– What is the equation for

photosynthesis?

– What is the equation for respiration.

– Respiration breaks down carbohydrates into ATP.

Photosynthesis and Cell Respiration• Plants perform both

photosynthesis and respiration.– Think: It would pointless to

make carbohydrates if you did not break them down into energy.

Factors Affecting Photosynthesis• Water– No enough water means that their will

not be enough electrons and H+ to make ATP and NADPH.

– Can too much water harm a plant?• Temperature– Too cold: photosynthesis occurs slowly– Too hot: the enzyme that control

photosynthesis break down.• Light Intensity– Light is needed to energize the electron

from the H2O molecule.– Light that is the wrong color or not

intense will slow down photosynthesis.

Short Answer Questions

• Explain how the ATP molecule functions similar to rechargeable batteries? (4 points)

• Write the overall equation for photosynthesis. (2 points)

• Explain why leaves of deciduous trees change color in the fall? (3 points)

Photosynthesis

includes bothconverts

in which in which

(b) (c)

light-excitedelectrons ofchlorophyll

CO2 is fixed toRuBP

and then

(h)reduceNADP+ to

using

to produce

sugar(G3P)

(f)

chemiosmosis

(e)

(g)

by

producing

are passeddown

(d)

and

to

chemicalenergy

H2O is split

(a)

Green Solar Cells1. What is responsible for the various shades

of green in plants?2. What is the function of the stroma

lamellae?3. What evidence supports the theory that

chloroplast were once invasive cells?4. How is excess food stored? 5. How does the author define

photosynthesis?