Photosynthesis

Chapter 8 (M)

Energy and Life

Section 8.1

Chemical Energy and ATP Energy ability to do work All life depends on the ability to obtain and

use energy Energy

Light Heat Chemical

Living organisms use the energy stored in chemical bonds of compounds

ATP Adenosine Tri-phosphate Provides Energy for Cellular Work

Energy Needed For

Muscle cells to contractMove ions & molecules across membranes

Heart to pump bloodMaking new molecules growth & repair

ATP Packs EnergyCarbohydrates, fats, proteins

from food do not drive work in cells directly

The chemical energy stored in these must be converted into a more usable form

ATP Energy Molecule

High EnergyFood Energy Released Stored in ATP

Low Energy Waste

ATP

ATP

ATP

Adenosine Tri PhosphateATP = Adenosine tri phosphateWhen phosphate bond is broken energy is released

ATP & Cellular WorkChemical Rxn Phosphate

bond in ATP is broken & transferred to another molecule

Work in a cellTransportMechanicalChemical

ATP converted to ADP ATP

recyclable Work consumes

ATP, ATP regenerated from ADP +P

Working muscle need 10 million ATP / second

Energy Flow in Ecosystems

Organisms require a constant source of energy to survive

Producers/Autotrophs

Producer: an organism that makes its own food

Producer = Autotroph (gets energy directly from the sun)Ex. Plants, Algae, some bacteria

Consumers/ Heterotrophs

Consumer: an organism that gets its energy by eating other organisms

Consumer = Heterotroph (gets energy indirectly from the sun)Ex. all other organisms except autotrophs

“I MUST BE A HETEROTROPH I CAN'T MAKE THESE !!"

LIFE depends on the SUN

The SUN provides light energy

Plants, algae, & some bacteria capture this energy and store it as food (Photosynthesis)

PhotosynthesisThe use of sunlight to make food

Takes place in the chloroplast of leaves

Chloroplasts

Special organelles that can capture the energy of the sun

Present in the mesophyll layer of leaves

Stomata tiny pores also present in leaves CO2 enters and O2 exits

Structure of Chloroplasts Stroma thick fluid in

the inner membrane Thylakoidsdisc

shaped sac suspended in the stroma

Grana stacks of thylakoids

Chlorophylls pigments that give the leaves color

Light Energy and Pigments

Sunlight is a form of electromagnetic energy

Electromagnetic energy travels in waves

Wavelength distance between two adjacent waves

Electromagnetic Spectrum Range very short (gamma) to

long (radio waves)

PigmentsAbsorb and reflect light resulting in the color of the leaves

Green wave length of light is not absorbed, it is reflected back hence leaf appears green

Why leaves are green: interaction of light with chloroplasts

Absorption Spectrum

Action & Absorption Spectra photosynthesis is greatest in the blue and red end

Pigments and Chromatography Paper chromatography technique used

to separate a mixture into its component molecules.

The molecules migrate, or move up the paper, at different rates because of differences in solubility, molecular mass, and hydrogen bonding with the paper

In paper chromatography the pigments are dissolved in a solvent that carries them up the paper.

Chromatography

Retention Factor

Rf = distance traveled by spot/ distance traveled by solvent

If the for an unknown is close to or same as that for a known compound, the two are most likely similar or identical

Sample origin

Solute front

Solvent Front

Plants take CO2 from the air

Veins carry water and nutrients from the plants roots to the leaves

6CO2 + 6H2O C6H12O6 + 6O2

Overview of Photosynthesis

PhotosynthesisStages:1. Light reaction takes

place in the thylakoid membrane

2. Calvin cycle takes place in the stroma

Light ReactionsPhotosystems present within

the thylakoid membrane, contain chlorophylls (a,b) and other pigments (carotenoids)

Pigments act as a light gathering panel

Light pigment absorbs energy energy transferred to Reaction center

Reaction CenterChlorophyll a traps energy

makes ATP & NADPHATP & NADPH used in Calvin

Cycle

Calvin Cycle Like a sugar factory Uses NADPH & ATP form the light

rxn to fix CO2

3 CO2 enters the cycle and joins with RuBP (ribulose bisphosphate)

G3P is formed that exits the cycle, RuBP is regenerated

G3P is used by the plant to make sugar

Calvin Cycle

Rubisco most abundant enzyme in the world Why?

Adds CO2 to RuBP to form a six carbon compound that breaks down into G3P

Calvin Cycle

Overview of Photosynthesis

Photosynthesis

Reactants 6CO2 + 6 H2OProducts C6H12O6 + 6O2

Factors Affecting Photosynthesis Temperature best between 0oC-

35oC Light Intensity high intensity

increase photosynthesis maximum is reached

Water raw material, shortage can slow down or stop photosynthesis

Photosynthesis Under Extreme Conditions Under hot dry, bright condition stomata

close, plant conserves water Decreases the photosynthetic output Certain species of plants have evolved

alternate modes of carbon fixation to minimize photorespiration

C4 Photosynthesis CAM Plants

C4 Plants

Have a specialized pathway to capture low levels of CO2 and pass it to the Calvin cycle

Rxn takes place that incorporates CO2 into 4C compounds

Occurs in corn, sugar cane, crabgrass, at least 19 plant families use this

CAM Plants

Crassulaceae Acid Metabolism Aloe , Jade , Cacti Keep in as much water as possible by

opening stomata only at night Store CO2 organic acids (in vacuoles) During the day these organic acids

release CO2 Calvin cycle takes place

C4 and CAM Plants