Photosynthesis Photosynthesis Photosynthesis is the way that plants

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Photosynthesis

Photosynthesis

Photosynthesis • Photosynthesis is the way that plants make food from sunlight – You

Photosynthesis • Photosynthesis is the way that plants make food from sunlight – You take in food which is digested and then transferred to cells for use by mitochondria – Plants can’t “eat” so they make food which is then transferred to the mitochondria – Mitochondria then transform the “food energy” into chemical energy

Photosynthesis • Why does it matter? – Source of nearly all the energy on

Photosynthesis • Why does it matter? – Source of nearly all the energy on Earth – Process by which atmospheric gases are maintained in the ratios we need to survive

Photosynthesis • Who photosynthesizes? Some bacteria

Photosynthesis • Who photosynthesizes? Some bacteria

Photosynthesis • Who photosynthesizes? Some bacteria Some protists

Photosynthesis • Who photosynthesizes? Some bacteria Some protists

Photosynthesis Most plants

Photosynthesis Most plants

Photosynthesis • Heterotroph: organism that must consume food • Autotroph: organism that makes its

Photosynthesis • Heterotroph: organism that must consume food • Autotroph: organism that makes its own food (photosynthesis)

Photosynthesis 6 CO 2 + 6 H 2 O + light energy → C

Photosynthesis 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 Carbon dioxide Water Carbohydrate Oxygen

Photosynthesis 6 CO 2 + 6 H 2 O + light energy → C

Photosynthesis 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 Carbon dioxide Water Carbohydrate Oxygen

Epidermis Mesophyll Guard cells Epidermis Vein Stoma

Epidermis Mesophyll Guard cells Epidermis Vein Stoma

Photosynthesis • Vein: water delivery

Photosynthesis • Vein: water delivery

Photosynthesis • Epidermis: water-proof covering of the surface of the leaf – Prevents unwanted

Photosynthesis • Epidermis: water-proof covering of the surface of the leaf – Prevents unwanted loss of water and gases

Photosynthesis • Stoma: Opening in the leaves – water exits – O 2 exits

Photosynthesis • Stoma: Opening in the leaves – water exits – O 2 exits – CO 2 enters

Photosynthesis • Stoma: Opening in the leaves – water exits – O 2 exits

Photosynthesis • Stoma: Opening in the leaves – water exits – O 2 exits – CO 2 enters Transpiration

Photosynthesis • Guard cells: surround stoma – Open and close stoma

Photosynthesis • Guard cells: surround stoma – Open and close stoma

Photosynthesis • Mesophyll: central layer of cells – contains chloroplast-rich cells – site where

Photosynthesis • Mesophyll: central layer of cells – contains chloroplast-rich cells – site where most photosynthesis occurs

Photosynthesis

Photosynthesis

Photosynthesis • 2 sets of reactions:

Photosynthesis • 2 sets of reactions:

Photosynthesis • 2 sets of reactions: – LIGHT DEPENDENT REACTIONS

Photosynthesis • 2 sets of reactions: – LIGHT DEPENDENT REACTIONS

Photosynthesis

Photosynthesis

Photosynthesis • 2 sets of reactions: – LIGHT DEPENDENT REACTIONS – LIGHT INDEPENDENT REACTIONS

Photosynthesis • 2 sets of reactions: – LIGHT DEPENDENT REACTIONS – LIGHT INDEPENDENT REACTIONS (Calvin cycle)

Photosynthesis

Photosynthesis

Light Dependent Reactions

Light Dependent Reactions

Light Dependent Reactions • Thylakoids contain pigments

Light Dependent Reactions • Thylakoids contain pigments

Light Dependent Reactions • Pigments: molecules that absorb light energy

Light Dependent Reactions • Pigments: molecules that absorb light energy

Light Dependent Reactions • Pigments: molecules that absorb light energy – Electrons are energized

Light Dependent Reactions • Pigments: molecules that absorb light energy – Electrons are energized by absorbing energy and “jumping” energy levels

Light Dependent Reactions • Pigments: molecules that absorb light energy – Electrons are energized

Light Dependent Reactions • Pigments: molecules that absorb light energy – Electrons are energized by absorbing energy and “jumping” energy levels – A specific amount of energy is required in order for the electron of a specific atom to jump and land in another energy level • Ex. Long jumping versus hopscotch

Light Dependent Reactions • Thylakoids contain the pigment chlorophyll – Chlorophylls a and b

Light Dependent Reactions • Thylakoids contain the pigment chlorophyll – Chlorophylls a and b • Absorb light on opposite ends of the visible light spectrum • Between 500 and 600 nm light is reflected • Why chlorophyll appears green

Light Dependent Reactions • Thylakoids contain the pigment chlorophyll Absorbed Reflected Absorbed

Light Dependent Reactions • Thylakoids contain the pigment chlorophyll Absorbed Reflected Absorbed

Light Dependent Reactions • Thylakoids contain pigments called carotenoids – Absorb light below 550

Light Dependent Reactions • Thylakoids contain pigments called carotenoids – Absorb light below 550 nm – Appear red, orange, and yellow

Light Dependent Reactions • Thylakoids contain pigments called carotenoids Absorbed Reflected

Light Dependent Reactions • Thylakoids contain pigments called carotenoids Absorbed Reflected

Light Dependent Reactions • Thylakoids contain pigments – Which pigment is dominant in deciduous

Light Dependent Reactions • Thylakoids contain pigments – Which pigment is dominant in deciduous trees right now?

Light Dependent Reactions • Pigment in the thylakoids form Photosystems – Network of pigments

Light Dependent Reactions • Pigment in the thylakoids form Photosystems – Network of pigments held together within a protein matrix – Channel energy absorbed from light to a specific pigment molecule: reaction center chlorophyll

Light Dependent Reactions • Pigment in the thylakoids form Photosystems – Reaction center chlorophyll

Light Dependent Reactions • Pigment in the thylakoids form Photosystems – Reaction center chlorophyll passes the energy (via an energized electron) to a primary electron acceptor: Ferredoxin

Light Dependent Reactions • Process of replacing the electrons that follows this step depends

Light Dependent Reactions • Process of replacing the electrons that follows this step depends on the organism: – Bacteria: cyclic – Algae and plants: non-cyclic

Light Dependent Reactions • Cyclic phosphorylation – Bacteria – Contain only 1 photosystem: Photosystem

Light Dependent Reactions • Cyclic phosphorylation – Bacteria – Contain only 1 photosystem: Photosystem I – From electron acceptor, electrons go through electron transport system from which ATP is produced – Electrons then return to Photosystem I

Light Dependent Reactions • Non-cyclic phosphorylation – Algae and plants – Contain 2 photosystems:

Light Dependent Reactions • Non-cyclic phosphorylation – Algae and plants – Contain 2 photosystems: Photosystem I, and Photosystem II – PS II acts first

Light Dependent Reactions • Non-cyclic phosphorylation – Photon of light energy excites electron which

Light Dependent Reactions • Non-cyclic phosphorylation – Photon of light energy excites electron which is passed from PS II to electron transport chain and then to PS I – Another photon of light re-excites the electron now in PS I which passes the electron to the primary electron acceptor and through a series of reactions

Light Dependent Reactions • Non-cyclic phosphorylation – Electrons lost from PS II must be

Light Dependent Reactions • Non-cyclic phosphorylation – Electrons lost from PS II must be replaced • PS II takes an electron from protein Z • Protein Z then takes an electron from water by splitting a water molecule into H+ ions and O • H+ ions are used later, O forms O 2 and is “exhaled”

Light Dependent Reactions • Electron transport chains – Series of enzymes embedded in membrane

Light Dependent Reactions • Electron transport chains – Series of enzymes embedded in membrane called the cytochrome complex – Receive excited electrons from PS II and PS I – Electrons are passed from 1 molecule to the next

Light Dependent Reactions • Electron transport chains – Energy from the electrons energized in

Light Dependent Reactions • Electron transport chains – Energy from the electrons energized in PS II powers a proton pump – Proton pumps protons into the thylakoid space – Results in high concentration of protons in the thylakoid space – Concentration gradient powers ATPase

Light Dependent Reactions • Electron transport chains – ATPase allows protons back out of

Light Dependent Reactions • Electron transport chains – ATPase allows protons back out of membrane – Rush of protons provides enough energy to attach a phosphate to an ADP forming ATP – This process is called chemiosmosis

Light Dependent Reactions • Electron transport chains – Energy from the electrons energized in

Light Dependent Reactions • Electron transport chains – Energy from the electrons energized in PS I is passed to a reduction complex – At the reduction complex NAD+ is transformed into NADH

Light Dependent Reactions • Electron transport chains – NAD+ is an electron acceptor: it

Light Dependent Reactions • Electron transport chains – NAD+ is an electron acceptor: it holds on to the energy from the electrons until it can be used to bind a phosphate group to an ADP

Light Dependent Reactions • Electron transport chains – ATP and NADH produced leave thylakoid

Light Dependent Reactions • Electron transport chains – ATP and NADH produced leave thylakoid to participate in the next set of reactions: the light independent reactions or Calvin cycle

Light Dependent Reactions Ferredoxin

Light Dependent Reactions Ferredoxin

Light Dependent Reactions Ferredoxin Z

Light Dependent Reactions Ferredoxin Z

Light Dependent Reactions Ferredoxin Z Energy is taken from the electrons and is used

Light Dependent Reactions Ferredoxin Z Energy is taken from the electrons and is used to make ATP from ADP

Light Dependent Reactions Ferredoxin Feredoxin Z Energy is taken from the electrons and is

Light Dependent Reactions Ferredoxin Feredoxin Z Energy is taken from the electrons and is used to make ATP from ADP

Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to

Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to make NADPH from NADP Z Energy is taken from the electrons and is used to make ATP from ADP

Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to

Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to make NADPH from NADP Z Energy is taken from the electrons and is used to make ATP from ADP ATP and NADPH leave thylakoid and enter the stroma where they are used in the Calvin cycle

Light Dependent Reactions Ferredoxin Ele ctr on 2 H+ Oxygen is + released as

Light Dependent Reactions Ferredoxin Ele ctr on 2 H+ Oxygen is + released as a by-product O Tra ns 2 e- Water molecule is split by protein Z 2 e- po Cytochrome complex rt S ys te Ele c tro n Sy Tra ste ns m por t NADPH reductase m 2 e- NADP+ + 2 H+ NADPH + H+ H 2 O Z 2 e- 2 e. Energy is removed from the electrons as they move down the ETC. The energy is used to pump p+ into thylakoid. p+s power ATPase which converts ADP to ATP Light Photosystem II ADP + Pi + Energy → ATP Light ATP and NADPH leave thylakoid and enter stroma to be used in the Calvin cycle

Light Independent Reactions (Calvin cycle)

Light Independent Reactions (Calvin cycle)

Calvin cycle • Uses ATP and NADPH produced in the light-dependent reactions • Also

Calvin cycle • Uses ATP and NADPH produced in the light-dependent reactions • Also uses CO 2 taken in through stoma • Requires no sunlight • Produces carbohydrate which is used by mitochondria in respiration

Calvin cycle (3 PGA) (From light dependent reactions)

Calvin cycle (3 PGA) (From light dependent reactions)

Calvin cycle (3 PGA) (From light dependent reactions)

Calvin cycle (3 PGA) (From light dependent reactions)

Calvin cycle (PGA) (From light dependent reactions)

Calvin cycle (PGA) (From light dependent reactions)

Calvin cycle CO 2 CARBON FIXATION Rubisco Ru. BP 3 PGA ATP ADP ATP

Calvin cycle CO 2 CARBON FIXATION Rubisco Ru. BP 3 PGA ATP ADP ATP REGENERATION OF Ru. BP 1, 3 Bisphoglycerate NADPH NADP+ Pi G 3 P (carbohydrate) REDUCTION Output for use by mitochondria in respiration

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA ↓ Rubisco

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA ↓ Rubisco

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA → →

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P ↓ Rubisco

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA → →

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P ↓ ↓ Rubisco 6 ATP

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA → →

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P ↓ ↓ ↓ Rubisco 6 ATP 6 NADPH

Calvin cycle output ↓ ↓ ↓ Rubisco 6 ATP 6 NADPH ↓ 3 CO

Calvin cycle output ↓ ↓ ↓ Rubisco 6 ATP 6 NADPH ↓ 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P

Calvin cycle output ↓ 3 CO 2 + 3 Ru. BP → 6 PGA

Calvin cycle output ↓ 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P → 3 Ru. BP ↓ ↓ ↓ Rubisco 6 ATP 6 NADPH

Calvin cycle output ↓ 3 CO 2 + 3 Ru. BP → 6 PGA

Calvin cycle output ↓ 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P → 3 Ru. BP ↓ ↓ 6 ATP 6 NADPH ↓ ↓ Rubisco ATP

Calvin cycle output ↓ 3 CO 2 + 3 Ru. BP → 6 PGA

Calvin cycle output ↓ 3 CO 2 + 3 Ru. BP → 6 PGA → → 6 G 3 P → 3 Ru. BP ↓ ↓ 6 ATP 6 NADPH ↓ ↓ Rubisco ATP

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA

Calvin cycle 3 CO 2 + 3 Ru. BP → 6 PGA

Photosynthesis

Photosynthesis

Calvin cycle

Calvin cycle