Photosynthesis Energy & Life

Overview of Photosynthesis

Autotrophs Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food.

Autotrophs Autotrophs include organisms that make their own food Autotrophs can use the sun’s energy directly Euglena

Heterotrophs Heterotrophs are organisms that can NOT make their own food Heterotrophs can NOT directly use the sun’s energy

Candles release energy as HEAT & LIGHT Energy can be changed from one form to another Energy can be stored in chemical bonds & then released later Candles release energy as HEAT & LIGHT

ATP – Cellular Energy Adenosine Triphosphate Contains two, high-energy phosphate bonds Also contains the nitrogen base adenine & a ribose sugar

One phosphate bond has been removed ADP Adenosine Diphosphate ATP releases energy, a free phosphate, & ADP when cells take energy from ATP One phosphate bond has been removed

Importance of ATP Principal Compound Used To Store Energy In Living Organisms. Most energy stored between the last 2 phosphate bonds

Releasing Energy From ATP ATP is constantly being used and remade by cells ATP provides all of the energy for cell activities The high energy phosphate bonds can be BROKEN to release energy

Releasing Energy From ATP Adding A Phosphate Group To ADP stores Energy in ATP Removing A Phosphate Group From ATP Releases Energy & forms ADP Loose Gain

Cells Using Biochemical Energy Cells Use ATP For: Active transport Movement Photosynthesis Protein Synthesis Cellular respiration All other cellular reactions

Glucose is a monosaccharide C6H12O6 One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP

History of Photosynthesis & Plant Pigments

Photosynthesis Involves the Use Of light Energy to convert Water (H20) and Carbon Dioxide (CO2) into Oxygen (O2) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches

Investigating Photosynthesis Early Research Focused On The Overall Process Later Researchers Investigated The Detailed Chemical Pathways Many Scientists Have Contributed To Understanding Photosynthesis

Early Questions on Plants Several Centuries Ago, The Question Was: Does the increase in mass of a plant come from the air? The soil? The Water?

Van Helmont’s Experiment 1643 Planted a seed into A pre-measured amount of soil and watered for 5 years Weighed Plant & Soil. Plant Was 75 kg, Soil The Same. Concluded Mass Came From Water

A candle requires oxygen to burn A candle requires oxygen to burn. Can you think of an experimental design that would prove plants make oxygen?

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.

Repeated Priestly experiment with & without sunlight 1779 Repeated Priestly experiment with & without sunlight

Results of Ingenhousz’s Experiment Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight. Light Was Necessary For Plants To Produce The “Burning Gas” or oxygen

Melvin Calvin 1948 First to trace the path that carbon (CO2) takes in forming Glucose Does NOT require sunlight Called the Calvin Cycle or Light Independent Reaction Also known as the Dark Reaction

Rudolph Marcus 1992 Studied the Light Independent Reactions First to describe the Electron transport Chain

The Photosynthesis Equation

Pigments In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments Chlorophyll is the primary light-absorbing pigment in autotrophs Chlorophyll is found inside chloroplasts

Light and Pigments Energy From The Sun Enters Earth’s Biosphere As Photons Photon = Light Energy Unit Light Contains A Mixture Of Wavelengths Different Wavelengths Have Different Colors

The Biochemical Reactions

It Begins with Sunlight!

Photoautotrophs Absorb Light Energy

Inside A Chloroplast

Structure of the Chloroplast Double membrane organelle Outer membrane smooth Inner membrane forms stacks of connected sacs called thylakoids Thylakoid stack is called the granun (grana-plural) Gel-like material around grana called stroma

Thylakoid membranes Light Dependent reactions occur here

Photosynthesis Overview

Light Dependent Reactions Occurs across the thylakoid membranes Uses light energy Produce Oxygen from water Convert ADP to ATP

Light Dependent Reaction

Light Dependent Reaction

Oh it could get a whole lot more complicated folks!

Light Reaction Summary Reactants: H2O Light Energy Energy Products: ATP NADPH

The Calvin Cycle

Factors Affecting the Rate of Photosynthesis Amount of available water Temperature Amount of available light energy