Bellringer – April 4, 20141) Draw the following leaf and fill in the blanks

for the 5 arrows.

2) In what organelle does photosynthesis take place?

3) Try and write the FULL equation for photosynthesis

3

Photosynthesis:Life from Light and Air

Honors Biology

Photosynthesis

• Photo = “light”• Synthesis = “to make”• Photosynthesis = using light to make

something….• What needs to be made during

photosynthesis?

Photosynthesis is…

• When plants convert the energy of sunlight into chemical energy stored in the bonds of carbohydrates

• Examples of carbohydrates are: – Glucose– Fructose– Sucrose– Starch– Cellulose

2 Types Metabolic Pathways

• Catabolic pathways – Break down complex molecules into simpler

compounds– Release energy• Ex: Cellular Respiration

• Anabolic pathways (“add”)– Build complicated molecules from simpler ones– Sometimes called “biosynthetic pathways” – Consume energy• Ex: Building protein from amino acids

Real Life Examples…• Exergonic (Exothermic)– Cellular Respiration– Energy (ATP) is released when glucose is

broken down• Endergonic (Endothermic) – Photosynthesis– Energy (ATP) is NEEDED (consumed) to put

together glucose from CO2, H20 and sunlight– http://flightline.highline.edu/jbetzzall/BI100/animations/energy_changes.html

What is the chemical energy needed by cells?

• ATP (Adenosine Triphosphate)• When energy is needed, ATP is broken down• ATP is renewable • Energy is released and ATP becomes ADP + P

– ADP (Adenosine Di-phosphate) + PDRAW

ME!

P

Adenosine triphosphate (ATP)

H2O

+ Free Energy given off

Inorganic phosphate + Adenosine diphosphate (ADP)

PP

P PP i

Sometimes referred to as “high energy” phosphate bonds

–ATP an “energy currency”

Example of Energy Coupling

ADP and ATP• ADP stores energy by adding phosphates– Like a rechargeable battery

• ATP releases energy by breaking bonds between phosphates

Plants are energy producers• Like animals, plants need energy to live• Unlike animals, plants don’t need to eat

food to make that energy• Plants make both food & energy– animals are consumers– plants are producers

The Process That Feeds the Biosphere

Photosynthesisthe process that converts solar

energy into chemical energyWho or What?

Plants and other autotrophsThey are producers of the

biosphere

2 Types of Autotrophs1.Chemoautotrophs– Use chemosynthesis to make

“food” 2. Photoautotrophs– Use photosynthesis to make

“food”

Plants, some bacteria and algae are photoautotrophs Use energy of sun to make organic molecules

from H2O and CO2

Some worms and bacteria are chemoautotrophs Use energy from chemicals to make organic

molecules

Photosynthesis Occurs in plants, algae, certain other

protists, some prokaryotesThese organisms use light energy to drive the synthesis of organic molecules from carbon dioxideand (in most cases) water. They feed not onlythemselves, but the entire living world. (a) Onland, plants are the predominant producers offood. In aquatic environments, photosyntheticorganisms include (b) multicellularalgae, suchas this kelp; (c) some unicellular protists, suchas Euglena; (d) the prokaryotes clledcyanobacteria; and (e) other photosyntheticprokaryotes, such as these purple sulfurbacteria, which produce sulfur (sphericalglobules) (c, d, e: LMs).

(a) Plants

(b) Multicellular algae

(c) Unicellular protist10 m

40 m(d) Cyanobacteria

1.5 m(e) Pruple sulfur

bacteria

Figure 10.2

Autotrophs vs. Heterotrophs Heterotrophs

Obtain their organic material from other organisms

They are consumers of the biosphere

Using light & air to grow plants

6CO2 6H2O C6H12O6 6O2sunenergy

+ ++

glucose + oxygencarbondioxide

sunenergy+ water +

(ATP)

• Photosynthesis– using sun energy to make ATP– using carbon dioxide & water to make sugar– Takes place in chloroplast– allows plants to grows– makes a waste product

• oxygen

Chloroplasts: The Sites of Photosynthesis in Plants

The leaves of plants-THEY’RE GREEN!! major sites of photosynthesis

Chloroplasts Organelle where photosynthesis

occurs Stroma

Dense fluid within chloroplast Calvin Cycle (Dark reaction) occurs here

Thylakoids Membranous sac (or “coin”) in stroma Inside space called thylakoid space Light reactions occur here

Grana (granum = singular) Stack of thylakoids (“coins”)

Lumen-inside the thylakoid

****NOTE the difference between stroma and stoma (stomata)

The Equation for Photosynthesis Photosynthesis converts light energy

to the chemical energy of food Photosynthesis is summarized by this

Overall chemical equation

6 CO2 + 6 H2O + Light energy C6H12O6 + 6 O2

The Nature of Sunlight Light

a form of electromagnetic energy, which travels in waves and particles (called photons)

Wavelength distance between crests of waves Determines type of electromagnetic energy

(wavelength & energy are inversely proportionate)

The electromagnetic spectrum The entire range of

electromagnetic energy, or radiation

Gammarays X-rays UV Infrared

Micro-waves

Radiowaves

10–5 nm 10–3 nm 1 nm 103 nm 106 nm1 m

106 nm 103 m

380 450 500 550 600 650 700 750 nm

Visible light

Shorter wavelengthHigher energy

Longer wavelengthLower energy

Color we SEE = color most reflected by pigment; other colors (wavelengths) are absorbedBLACK all colors are reflected

Light

ReflectedLight

Chloroplast

Absorbedlight

Granum

Transmittedlight

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How is Energy Absorbed by Plants?!

• Pigment molecules– PHOTONS = packets of light energy that are absorbed

by pigments to energize electrons• Chlorophyll– 2 types

1) Chlorophyll a 2) Chlorophyll b– Differ b/c they absorb different wavelengths (colors)

Primary vs. Accessory Pigments

Primary PigmentChlorophyll a (most abundant)

Accessory (Antennae) Pigments

Chlorophyll bAnthocyaninsXanthophyllsCartenoids

Why are plants green?• Whatever color wavelength is reflected is the color

that the pigment appears to be– Plants do not absorb (aka reflect) green regions of visible

spectrum are therefore GREEN! • Chlorophyll a and chlorophyll b – Absorb red and blue (best colors for PS!)– What would the worst color be…?

GREEN!

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Carotenoids • Plant pigment• Often appear orange and yellow • Also found in green plants, too

• Can give flower petals their color!

Carotenoids

What happens to leaves in the fall?

• Days get shorter (less sunlight)• Temperature drops• Less chlorophyll is made, but is still broken

down at the same rate• Underlying red and orange pigments (which

were always there) are now seen

The Two Stages of Photosynthesis: A Preview

• The Light reactions•NEEDS LIGHT•Light Dependent Reactions

• The Calvin cycle•A.k.a- Dark Reactions or Light Independent Reactions •DOES NOT NEED LIGHT

The Light Reactions

Occur in the grana (& thylakoids)

Convert solar energy to chemical energy

Chlorophyll absorbs solar energy Splits water release O2 (a by-product) produce ATP (chemical energy)

The Calvin Cycle

Occurs in the stromaForms SUGAR from carbon dioxideCarbon fixation occurs (CO2

fixed carbon from C6H12O6) Uses ATP for energy and NADPH

for reducing power

An overview of photosynthesis

H2O CO2

Light

LIGHT REACTIONS

CALVINCYCLE

Chloroplast[CH2O](sugar)

NADPH

NADP

ADP+ P

O2

ATP

NADPH-Carries electrons that are needed to build molecules such as glucose.

Photosynthesis

This is the equation you are used to seeing, but this is not the whole story…

+ water + energy glucose + oxygencarbondioxide

6CO2 6H2O C6H12O6 6O2lightenergy

+ ++