Sheldon: Revised 2011 CHAPTER 8 Photosynthesis

PLANTS USE •

SUNLIGHT ENERGY

OWN FOOD TO MAKE THEIR • You Tube Plants and Sunlight

Where does your energy come from?

•

Autotrophs

• Plants use sunlight to make their own food •

Heterotrophs

• Obtain energy from foods they consume (plants and animals)

Energy in Chemical Bonds •

EXOTHERMIC

: When a bond is broken, energy is released. •

ENDOTHERMIC

: It takes energy in to hold bonds together.

Endothermic or Exothermic?

• • Endothermic Video (digital Thermometer) Barium Hydroxide Octahydrate with Ammonium Thiocyanate (teacher) • • • • • Exothermic Video (Fe2O3 + sugar) Sodium and Water in Trash Can Exothermic Thermite Myth Busters Thermite Exothermic Make an Instant Cold Pack from Sodium Acetate • (Nurd Rage) Supernova Make Glow Sticks - The Science

Cell’s Batteries

• ATP

•

A denosine T ri P hosphate

VIDEO: howstuffworks (ATP)

ATP

How are they different?

• Adenosine

tri

phosphate • Adenosine

di

phosphate

Third Phosphate

• Acts as an energy shuttle • Lose a phosphate = adenosine diphosphate ADP • Gain a phosphate = become adenosine triphosphate ATP

CHARGED UNCHARGED

The ATP cycle

“Phosphorylation” •

• Adding of a phosphate group to a molecule

Phosphorylation You Tube ATP ADP

Where might ATP be used?

•

Used directly for:

– – – – –

Muscle movement Synthesis of protein Firefly flash Sperm swimming White blood cells moving

Y ouTube Macrophage

Photosynthesis is the most important chemical process on earth because: •It provides food for virtually all organisms

Overall Equation for Photosynthesis

LIGHT AND PIGMENTS

We see reflected wavelengths We don’t see absorbed wavelengths

Chlorophyll •

The green pigment (light-absorbing molecules) in plants in their chloroplasts

Light Spectrum From Sun

Chlorophyll a and b • •

Chlorophyll a

• Absorbs 430 + 662 nm

Absorbs Blue violet and red

• •

Chlorophyll b

• Absorbs 460 + 642 nm

Absorbs Blue orange-red and

Chlorophyll absorbs light well in these colors.

Plants Reflect Green

Also plants have other pigments: • • •

Carotenoids (orange) Phycoerythrin (red) Flavins (orange-yellow) Anthocyanin – blue-purple

FYI Why do leaves change color?

• As fall comes there are shorter days of sunlight • Less photosynthesis means less food for plants.

• Chlorophyll breaks down and exposes the other colors that were there all along, but were masked by the green chlorophyll.

The Beginning of Photosynthesis Experiments What do you see?

Photosynthesis History Video

Photosynthesis History • • • 1580-1644

Van Helmont Plants gain most of their mass from H 2 O

• Priestley’s Experiment:

Plants release O

2

Collected oxygen sprig of mint 1733- 1804

Jan Ingenhousz

1730-1799 physician

•

Light is necessary for plants to produce O 2 NO LIGHT-no oxygen

LEAF INTERNAL STRUCTURE

4 7

Cross Section of Leaf

5 6 9 2 10 3 8 1

Leaf CS

2. Upper Epidermis (protection) 4. Mesophyll

-contains chloroplasts

3. Lower epidermis-see stoma (protection)

4. Mesophyll = middle leaf • • •

Made of: 6. Palisade Layer + 7. Spongy Layer (vertical, tightly packed) (has air spaces)

•

Is where photosynthesis takes place

6. Palisade Layer •

Tightly packed columns of plant cells

Palisade Layer has lots of chloroplasts

10. Air Space: Houses Gases in 7. Spongy Layer

5. Cuticle •

Waxy covering of epidermis (reduces water loss)

1. Stomata (pl.) (sing.= stoma) •

Opening to let gases and water vapor in and out

•

Controlled by guard cells

•

In lower epidermis

8. Guard Cells •

Control the opening of the stoma Stoma LabBench

LE 36-14 Which stoma is open and which is closed?

You Tube Guard Cells

20 µm

LE 36-15a

Cells turgid/Stoma open Radially oriented cellulose microfibrils Cell wall Cells flaccid/Stoma closed Vacuole Guard cell Changes in guard cell shape and stomatal opening and closing (surface view)

K +

LE 36-15b

Cells turgid/Stoma open H 2 O H 2 O H 2 O Cells flaccid/Stoma closed H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O Role of potassium in stomatal opening and closing H 2 O

9. Vein • •

Xylem - tubes carrying water Phloem - tubes carrying food

Leaf Cross Section Review

Photosynthesis Intro VIDEO • howstuffworks photosynthesis

CHLOROPLASTS The photosynthesizing organelle

Thylakoids • Disks containing chlorophyll

Grana (pl.) Granum (sing.) •

Stacks of thylakoid disks

Stroma • •

Cytoplasm of the chloroplast Where LIR (light independent reaction) occurs

Light Dependent Reaction • Occurs: thylakoid membrane • Produce ATP and NADPH

Vocabulary • ATP production is called “ photo phosphorylation” • (uses light) (adds P to ADP)

Get Colored Pencils LDR and ILR Diagrams

First LEO goes GER • LEO = loss of electrons is

oxidation

• GER = gain of electrons is

reduction

Redox Reactions

oxidized

Lose H Gain H

reduced

LDR • L ight D ependent R eaction

Vocabulary

PHOTOSYSTEM

(or Reaction Center) uses light to • energize molecules (electrons)

PSI

•

PSII

• P700 • P680 (Absorb sunlight)

1. Photon of light hits chlorophyll • Excites an electron • e- jumps around pigments until it hits chlorophyll a (reaction center) Demo with ping-pong balls!

LIGHT ABSORBTION AND TRANSFER TO THE REACTION CENTERS To ETC

ETC (Electron Transport Chain) • Accepts

high

them to

low

energy electrons and moves energy electrons • The energy lost is given to an

electron carrier

(

NADP+)

Virtual Cell: Photosynthesis

e- flow to NADP+ to form NADPH • NADPH is an electron carrier • Nicotinamide Adenine Dinucleotide Phosphate.

2. Water is Split • • • • Oxygen is released • H+ ions build up in thylakoid interior Light reactions PS II (click on the four steps) Kid Like Animation PSI

3. H+ ions pumped through the thylakoid membrane • H+ ions in chemiosmosis

4. Chemiosmosis • Build-up of H+ ions pumped through the ATP synthase to make ATP (P joins ADP)

Summary of Energy transformation in the light reactions

• Light energy starts the process • Flow of Electrons – Splitting of water molecules provides electrons – Release of oxygen molecules from water – Accumulation of H+ in thylakoid spaces – LDR Video

• Reduction of NADP to NADPH by adding electrons and H+ • Production of ATP using the H+ in thylakoid spaces – ATP synthase enzyme – Powered by flow of H+ from the thylakoid spaces – ADP + Phosphate (Pi) ---> ATP – McGraw-Hill ETC and ATP Synthesis

• • PSI and PSII Animation You Tube PS II Photosynthesis AnimationVCAC: Cellular

LIR (Light Independent Reaction) aka Calvin Cycle • Calvin Cycle

LIR (Light Independent Reaction) aka Calvin Cycle • Found: in the stroma of the chloroplast • Does not need sunlight but is run by ATP and NADPH made in the LDR • Here is where the carbohydrates are actually assembled • McGraw-Hill Calvin Cycle

Summary of the Calvin Cycle • Addition (

fixing) of gaseous CO 2 to RUBP

, a 5 carbon compound in the stroma of chloroplasts. • Energy input from

ATP

(ATP from the light reactions ---> ADP + Phosphate back to the light reactions) • Addition of H+ and energy from

NADPH

Summary (cont.) • • (NADPH from the light reactions --->

NADP+

back to the light reactions • Production of

carbohydrates

for storage, transport, and biosynthesis

Recycling

of 5 carbon compound ( to fix more CO 2

RUBP

)

Rubisco

Ribulose-1,5-bisphosphate carboxylase oxygenase

, • Most abundant protein in the world!

• Recyclable!

• Used in the first step of fixing (making useable) atmospheric CO 2 • Attqaches 5-c sugar to CO 2

Light Independent Reaction • • YouTube - The Calvin Cycle or and narrated) (animated YouTube - Calvin Cycle Video overview-animated diagram) (simple • YouTube - Photosynthesis-Calvin Cycle and Cyclic Electron Flow singer) (your fav science

Now Sing Along • • • YouTube - Photosynthesis - The Light Reactions YouTube - MY FAVE SONG: THE PHOTOSYNTHESIS SONG YouTube - Photosynthesis Song (with subtitles) • EXTRA CREDIT- 5 points • You write the lyrics to a common song about photosynthesis.

• Must have at least 5 stanzas.

OR • Make a model of either the LDR or LIR or chloroplast • Each must include at least 5 labeled items

Label the thylakoid disk

Label the thylakoid disk

PSII

PSI

stroma Thylakoid interior ETC stroma ATP Synthase

Chloroplast

Chloroplast

D A E C B

Chloroplast

D A E C B

F E D

G

C B H A

Summary: From Leaf to Molecules • Photosynthesis: The Movie Processes: Photosynthesis: The Movie

What runs the LDR?

What runs the LIR?

What runs the LDR?

sunlight

What runs the LIR?

ATP

and

NADPH

Overview of Photosynthesis