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 contract Move ions & molecules across membranes Heart to pump blood Making new molecules  growth & repair

ATP Packs Energy Carbohydrates, 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 Energy Food  Energy Released  Stored in ATP Low Energy Waste ATP

Adenosine Tri Phosphate ATP = Adenosine tri phosphate When phosphate bond is broken  energy is released

ATP & Cellular Work Chemical Rxn  Phosphate bond in ATP is broken & transferred to another molecule Work in a cell  Transport  Mechanical  Chemical

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)

Photosynthesis The 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  CO 2 enters and O 2 exits

Structure of Chloroplasts Stroma  thick fluid in the inner membrane Thylakoids  disc 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)

Pigments Absorb 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 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 Overview of Photosynthesis

Photosynthesis Stages: 1. Light reaction  takes place in the thylakoid membrane 2. Calvin cycle  takes place in the stroma

Light Reactions Photosystems  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 Center Chlorophyll a  traps energy  makes ATP & NADPH ATP & NADPH  used in Calvin Cycle

Calvin Cycle Like a sugar factory Uses NADPH & ATP form the light rxn to fix CO 2 3 CO 2 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 6CO H 2 O Products C 6 H 12 O 6 + 6O 2

Factors Affecting Photosynthesis Temperature  best between 0 o C- 35 o C 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

C 4 Plants Have a specialized pathway to capture low levels of CO 2 and pass it to the Calvin cycle Rxn takes place that incorporates CO 2 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 CO 2  organic acids (in vacuoles) During the day these organic acids release CO 2  Calvin cycle takes place

C 4 and CAM Plants