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Unit 3 – ENERGY Conversion. The Sun is the ultimate source of energy on Earth. Then what?. Plants convert the SOLAR ENERGY into CHEMICAL ENERGY (glucose and other high-energy carbs) Julius Mayer discovered this conversion in 1845. Energy flow through ecosystems.

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then what
Then what?
  • Plants convert the SOLAR ENERGY into CHEMICAL ENERGY (glucose and other high-energy carbs)
  • Julius Mayer discovered this conversion in 1845
energy flow through ecosystems
Energy flow through ecosystems
  • Autotrophs (Producers) – organisms that can make their own food (glucose)
  • Ex. Plants, algae
slide5
Heterotrophs (Consumers) – Organisms that obtain energy from the food they eat
  • Ex. Fungi, Animals… anything that has to EAT to get ENERGY
slide6

Why do plants and animals need energy?

  • Mechanical functions (muscle contractions – animals, turning toward the sun – plants)
  • Protein synthesis
  • Active transport
ps and cr chloroplasts and mitochondria
PS and CR: Chloroplasts and Mitochondria

Can PRODUCERS do both?

Can CONSUMERS do both?

atp energy currency of the cell
ATP = Energy Currency of the Cell
  • Adenosine TriPhosphate – most important energy storing compound used by every cell
  • Even used during PS to make glucose… which is used to make ATP!
question
Question

Why are eukaryotes able to be larger and more complex than prokaryotes?

Efficient energy

conversion

theory of endosymbiosis
Theory of Endosymbiosis
  • Lynn Margulies and many other scientists
  • The theory ofEndosymbiosis explains the origin of chloroplasts and mitochondria and their double membranes.
  • This concept postulates that chloroplasts and mitochondria are the result of years of evolution initiated by the endocytosis of bacteria and blue-green algae.
  • According to this theory, blue green algae and bacteria           were not digested; they became symbiotic instead.  
support for endosymbiotic theory
Support for Endosymbiotic Theory

Mitochondria and chloroplasts…

  • reproduce like bacteria do (binary fission)
  • have their own ribosomes that resemble bacterial ribosomes (70S)
  • are double membrane-bound
  • have their own DNA which is different than the DNA in the nucleus, but similar to bacterial DNA
photosynthesis
Photosynthesis
  • Involves the Use Of light Energy to convert Water (6H20) and Carbon Dioxide (6CO2) into Oxygen (6O2) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches
investigating photosynthesis
Investigating Photosynthesis
  • Many Scientists Have Contributed To Understanding Photosynthesis
  • Early Research: Overall Process
  • Later Researchers:Detailed Chemical Pathways
early questions on plants
Early Questions on Plants

Several Centuries Ago, The Question Was:Plants tend to grow… WHY?

Does the increase in mass of a plant come from the air? The soil? The Water?

van helmont s experiment 1643
Van Helmont’sExperiment 1643
  • Planted a seed into A pre-measured amount of soil and watered for 5 years
  • Weighed Plant & Soil.
  • Van Helmont dried and weighed the soil.
  • The plant gained approx. 74 kg of mass… but the dried soil weighed almost the same (lost ~2 ounces)
  • Concluded Mass Came From Water
priestley s experiment 1771
Priestley’s Experiment 1771
  • Burned Candle In Bell Jar Until It Went Out.
  • Placed Sprig Of Mint In Bell Jar For A Few Days.
  • Candle Could Be Relit And Burn.
  • Concluded Plants Released Substance (O2) Necessary For burning.
priestley o 2 is the burning gas and plants release it
Priestley = O2 is the burning gas and plants release it
  • Thinking questions:
  • Do all types of plants release the same amount of oxygen gas? How could you test that?
  • What factors, if any, might have an effect on the production of oxygen?
ingenhousz s experiment 1779
Ingenhousz’s Experiment 1779

Repeated Priestly experiment with & without sunlight

results of ingenhousz s experiment
Results of Ingenhousz’sExperiment
  • Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight.
  • Light Was Necessary For Plants To Produce The “Burning Gas” or oxygen
julius robert mayer 1845
Julius Robert Mayer 1845

Proposed That Plants can Convert Light Energy Into Chemical Energy

samuel ruben martin kamen 1941
Samuel Ruben & Martin Kamen1941

Used Isotopes To Determine That The Oxygen Liberated In Photosynthesis Comes From Water

RUBEN

KAMEN

melvin calvin 1948
Melvin Calvin 1948
  • First to trace the path that carbon (CO2) takes in forming Glucose
  • Used radioactive isotope Carbon-14
  • Does NOT require sunlight
  • Called the Calvin Cycle or Light Independent Reaction or Dark Reaction
rudolph marcus 1992
Rudolph Marcus 1992
  • Studied the Light Independent Reactions
  • First to describe the Electron Transport Chain
recap
Recap
  • Van Helmont = mass of a plant comes from water
  • Preistley = plants produce oxygen (the gas necessary for combustion)
  • Ingenhousz = plants only produce oxygen in the LIGHT (is a product of the light rnxs, NOT the calvin cycle)
  • Mayer = plants convert light into chemical energy
slide30

Ruben and Kamen = the O’s in oxygen gas comes from the O’s in water (breaking water molecules during light rxns). Used isotope of oxygen to trace its path.

  • Calvin = the C’s in glucose/ sugars comes from the C’s in carbon dioxide. Glucose/ sugars can be made in the absence of light. Used isotope of carbon.
  • Marcus = first to describe the ETC
photosynthesis1

SUN

photons

glucose

Photosynthesis
  • Anabolic (small molecules combined)
  • Light energy is converted into chemical energy.
  • Endergonic (stores energy)
  • Carbon dioxide (CO2) requiring process that uses light energy (photons-particles of light) and water (H2O) to produce organic macromolecules (glucose).

6CO2 + 6H2O  C6H12O6 + 6O2

question1
Question:

Where does photosynthesis take place?

plants

Chloroplast

Mesophyll

Cell

Stoma

Plants
  • Autotrophs – produce their own food (glucose)-Known as Producers. Examples plants, algae, and some bacteria.
  • Process called photosynthesis
  • Mainly occurs in the leaves:

a. stoma - pores

b. mesophyll cells

stomata stoma

Oxygen

(O2)

Carbon Dioxide

(CO2)

Stomata (stoma)

Pores in a plant’s leaves through which water and gases are exchanged between the plant and the atmosphere.

Found on the underside of leaves

adaptations
Adaptations
  • Why are stomata usually located on the bottom/ underside of a leaf?
  • Where would a water lily’s stomata probably be located?
  • How would desert plants adapt? They need to avoid losing water from stomata BUT need to open the stomata to allow CO2 in and O2 out…
mesophyll cell of leaf

Nucleus

Cell Wall

Chloroplast

Central Vacuole

Mesophyll Cell of Leaf

Photosynthesis occurs in these cells!!!

chloroplast

Stroma

Outer Membrane

Thylakoid

Granum

Inner Membrane

Chloroplast

Organelle where photosynthesistakes place.

Thylakoid stacks are connected together

Stroma is a solution surrounding thylakoids

question2
Question:

Why are plants green?

chlorophyll molecules
Chlorophyll Molecules

Pigment-Light absorbing molecule

Often stored in vacuoles

  • Plants are green because the green wavelength is reflected, not absorbed.
  • CHLOROPHYLL – reflects green light, absorbs light of other wavelengths. Found in chloroplasts
  • Carotenoids, Anthocyanins, Xanthophylls accessory pigments. Absorbs different wavelengths of light than chlorophyll
wavelength of light nm

Short wave

Long wave

(more energy)

(less energy)

Wavelength of Light (nm)
question3
Question:

During the fall, what causes the leaves to change colors?

fall colors
Fall Colors
  • In addition to the chlorophyll pigments, there are other pigments present
  • During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments
  • Carotenoids are pigments that are either red, orange, or yellow
light reactions
Light Reactions

1.Light Reaction or Light Dependent Reaction -

  • Occurs within the thylakoid membranes
  • Reactant: H2O
  • Product: O2 (and ATP)
remember ingenhousz
Remember Ingenhousz?

Plant + Light = OXYGEN!

dark reactions
Dark Reactions

2. Calvin Cycle or Light Independent Reaction

  • Also called Carbon Fixation or C3 Fixation
  • Reactant: CO2 (ATP is used)
  • Product: Glucose and other high-energy carbohydrates
remember calvin
Remember Calvin?
  • The 6 Carbons in Glucose comes from 6 molecules of CO2
  • How do plants get CO2?STOMATA = SITE OF GAS EXCHANGE IN PLANTS
cyclic electron flow during light rxns

e-

Primary

Electron

Acceptor

SUN

e-

ATP

produced

by ETC

e-

Photons

e-

P700

Accessory

Pigments

Photosystem I

Cyclic Electron Flow during Light RXNs

Pigments absorb light energy & excite e- of Chlorophyll a to produce ATP

slide52

. Energy stored in the bonds between

phosphate molecules is released when a

phosphate molecule breaks off.

chemiosmosis
Chemiosmosis
  • Powers ATP synthesis
  • Located in the thylakoid membranes
  • Uses ETC and ATP synthase (enzyme) to make ATP
  • Photophosphorylation: addition of phosphate to ADP to make ATP
chemiosmosis1

SUN

(Proton Pumping)

H+ H+

Thylakoid

E

T

PS I

PS II

C

high H+

concentration

H+ H+

H+ H+

H+ H+

Thylakoid

Space

H+

ATP Synthase

low H+

concentration

ADP + P

ATP

H+

Chemiosmosis
chloroplast1

STROMA– where Calvin Cycle occurs

Outer Membrane

Thylakoid

Granum

Inner Membrane

Chloroplast
rate of photosynthesis
Rate of Photosynthesis
  • What factors affect the rate of PS?
  • Temperature
  • Light Intensity
  • Amount of CO2