AP Biology

Photosynthesis

AP Biology

Redox Reactions

break bonds & move electrons from one

molecule to another

as electrons move they “carry energy” with them

that energy is stored in another bond,

released as heat or harvested to make ATP

e-

+ +e-

+ –loses e- gains e- oxidized reduced

oxidation reduction

redox

e-

AP Biology

How do we move electrons in biology?

Moving electrons in living systems

electrons cannot move alone in cells

electrons move as part of H atom

move H = move electronsp

e

+

H

+H

+ –loses e- gains e- oxidized reduced

oxidation reduction

AP Biology

Redox in biology

The atoms that H tends to bond with in

biology attract electrons more (more

electronegative)

Essentially moving H is moving

electrons

Oxidation is losing hydrogen atoms

Reduction is gaining hydrogen atoms

AP Biology

Energy for life

The energy captured through

photosynthesis forms the basis of the

ecological pyramid.

AP Biology

Energy needs of Life

Autotrophs (Plants)

produce their own energy (from

“self”)

convert energy of sunlight

build organic molecules (CHO)

from CO2

make energy & synthesize sugars

through photosynthesis

producers

AP Biology

Energy needs of life

All life needs a constant input of energy

Heterotrophs (Animals)

get their energy from “eating others”

eat food = other organisms =

organic molecules

make energy through respiration

consumers

AP Biology 2007-2008

AP Biology

How are they connected?

glucose + oxygen carbon + water + energydioxide

C6H12O6 6O2 6CO2 6H2O ATP+ + +

Cellular Respiration

+ water + energy glucose + oxygencarbondioxide

6CO2 6H2O C6H12O6 6O2light

energy+ ++

Photosynthesismaking energy & organic molecules from light energy

making energy & organic molecules from ingesting organic molecules

exergonic

endergonic

AP Biology

N

PK…

H2O

What does it mean to be a plant

Need to…

collect light energy transform it into chemical energy

need to get building block atomsfrom the environment C,H,O,N,P,K,S,Mg

produce all organic moleculesneeded for growth

ATP

glucose

CO2

AP Biology

Plant structure

Obtaining raw materials

sunlight

leaves = solar collectors

CO2

stomata = gas exchange

H2O

uptake from roots

nutrients

N, P, K, S, Mg, Fe…

uptake from roots

AP Biology

stomata

transpiration

gas exchange

AP Biology

Chloroplasts

chloroplastsin plant cell

cross sectionof leafleaves

chloroplast

absorb

sunlight & CO2

make

energy & sugar

chloroplastscontain

chlorophyll

CO2

AP Biology

Chloroplasts

double membrane

stroma

fluid-filled interior

thylakoid sacs

grana stacks

Thylakoid membrane

contains

chlorophyll molecules

electron transport chain

ATP synthase

H+ gradient built up within

thylakoid sac

Plant structure H+H+

H+

H+

H+H+

H+H+

H+H+

H+

outer membrane inner membrane

thylakoidgranum

stroma

thylakoid

chloroplast

ATP

AP Biology

Photosynthesis

Light reactions

light-dependent reactions

energy conversion reactions

convert solar energy to chemical energy

ATP & NADPH

Calvin cycle

light-independent reactions

sugar building reactions

uses chemical energy (ATP & NADPH) to

reduce CO2 & synthesize C6H12O6

AP Biology

Things that happen in the Light

Reaction Light absorbed by chlorophyll

This drives the transfer of H to an electron

acceptor called NADP+ which temporarily

stores energized electron.

ADP ATP (phosphorylation)

O2 is given off as a byproduct because

water is split

Two forms of compounds hold chemical

energy: NADPH and ATP

AP Biology

Calvin Cycle

CO2 gets incorporated into organic

compounds in plant (C6H12O6)

Carbon-fixation

NADPH gives H atoms to CO2 (requires

ATP)

AP Biology

I see the Light!

Light is a flow of energy called

electromagnetic energy/radiation and

travels in waves

Photons are fixed energy in light

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Pigments of photosynthesis

Chlorophylls & other pigments

embedded in thylakoid membrane

arranged in a “photosystem” collection of molecules

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A Look at Light The spectrum of color

ROYGBIV

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Excitation of Chlorophyll by Light

When hit with a photon, an electron is

elevated to the next orbital. It is

“excited” and unstable.

If the electron has no where to go, it

emits light and heat when it falls back

to its original state.

AP Biology

Diagram

Using your notes and the book, draw a

detailed diagram of the light reaction

and Calvin cycle in the chloroplast.

Include what is used at each stage,

what is produced and what moves on.