Photosynthesis

Involves concepts from Biology PhysicsChemistry

Organisms exist because of chemical reactions occurring within cells. Chemical reactions occur in all cells, tissues, organs, and organ systems. Digestive System

What is a chemical reaction? Atoms or ions are joined together by chemical bonds (forming a compound) OR compounds are broken apart All chemical reactions involve a rearrangement of atoms or ions AND

Energy

Chemical Reactions Example of a reaction: 2H 2 + O 2  2H 2 O A molecule of hydrogen is made up of 2 hydrogen atoms held together by high energy bonds. A molecule of oxygen is made of 2 oxygen atoms held together by high energy bonds.

Chemical Reactions 2H 2 + O 2  2H 2 O Water is formed when molecules of hydrogen and molecules of oxygen are broken AND Atoms rearrange themselves into molecules of water held together with low energy bonds.

Chemical Reactions HIGH ENERGY BONDSLOW ENERGY BONDS REACTANTS PRODUCTS + 2H 2 + O 2  2H 2 O All of the extra energy found on the reactant side of the equation is released with the product as heat or light. Energy

Law of Conservation of Energy Energy cannot be created or destroyed, however it can change forms. In our example: If the reaction is reversed… Energy must be added to water to break it down. This added energy ends up stored in chemical bonds of hydrogen and oxygen molecules. 2H 2 O + Heat ENERGY  2H 2 + O 2 Energy can be stored for later use. Worksheet: chemical reactions and energy

Chemical Reaction-Formation of Water +

Forms +

Physics White light is made up of a spectrum of colors.

Physics The spectrum is seen when the white light is broken up into its components by prisms or raindrops*raindrops*

Light When all colors within white light are reflected back to our eyes  we see WHITE! When all colors within white light are absorbed by an object  we see BLACK! A surface appears a particular color because it contains a "pigment" that reflects that particular color and absorbs all other colors. Pigment = light absorbing colored molecule

Name the color What is the color of a sweater that absorbs blue, green and yellow light?

What colors are absorbed by Green Plants?

Green Plants Reflect green light Absorb all other colors of light

Green Plants

Biology Organisms make their own food and are called autotrophs

Or Organisms EAT plants or animals and are called __________________________________ heterotrophs

Biology Autotrophs use light energy from the sun (or chemical energy) to produce energy rich sugars/carbohydrates. Examples of autotrophs: _____________________,________________, ____________________________ some protistagreen plants some bacteria Energy in most ecosystems on earth comes from

Early Scientific Research on Photosynthesis 1643 – Belgium Jan van Helmont With your group: analyze van Helmont’s experiment

Conclusions from van Helmont’s experiment “…164 pounds of wood, bark, and roots had arisen from water alone.” The mass of the tree did NOT come from the soil. Was van Helmont correct? _____________________ Partially correct The mass of a plant comes in part from water…NOT from soil (except for a tiny fraction) Plants are made of carbohydrates. The term “hydrate” = water.

Late 1700’s England Joseph Priestley Joseph Priestley discovered oxygen in 1774 He continued to experiment with gases, plants and animals. With your group analyze Priestley’s experiment!

Priestley’s Photosynthesis Experiment Priestley concluded green plants produce the substance “oxygen” necessary for a fire to burn and for animal’s to breathe.

Late 1700’s Jan Ingenhousz’s Jan Ingenhousz was born in 1730 in the Netherlands. He trained as a medical doctor. In 1779, Ingenhousz took a position in the same laboratory as Joseph Priestley. Ingenhousz carried out research on photosynthesis.

Ingenhousz’s Photosynthesis Experiment Ingenhousz placed a pond plant in a jar filled with water He placed the jar in bright sunlight and observed bubbles produced by the plant He placed the jar in low light conditions and observed no bubbles produced by the plant

Ingenhousz’s Conclusion Green plants only produce oxygen in the presence of _______________. Sunlight

Photosynthesis By the mid-1800’s, it was understood that plants use carbon dioxide and water to produce glucose and oxygen using light energy from the sun. Photosynthesis Reaction: 6CO 2 + 6H 2 O +  C 6 H 12 O 6 + 6O 2 Reactants energy sourceProducts

Photosynthesis CO 2 enters plants through stomata (singular = stoma) in leaves and stem. O 2 and water exit the stomata* stomata

Carbon Dioxide

Water H 2 O enters plants through roots and is carried by the veins to leaves Water travels through the plant’s xylem (upward veins) from the roots to the leaves

Products of Photosynthesis Glucose and Oxygen Glucose is carried from the leaves of the plant in phloem (downward veins) to the parts of the plant where photosynthesis does not occur (roots, flowers). Glucose is stored in fruits (apples, oranges, etc.) and roots (onions, potatoes, etc.) Oxygen is released from stomata.

Photosynthesis Complete worksheet on Green Plants!

What else is needed for Photosynthesis? Photosynthesis occurs in the chloroplasts of plant cells.

Chloroplasts are made of thylakoids – sac-like membranes containing molecules of chlorophyll, a pigment, which absorbs red and blue light. stroma – space outside of the thylakoids

If plants contain chlorophyll why do they turn color in the fall? Some plants have leaves with multiple pigments for maximum absorption of light at different wave lengths. In the fall, the pigments begin to break-down. Chlorophyll breaks down first, revealing the other pigments below.

Processes of Photosynthesis Two Stage process: Light DEPENDENT reaction and Light INDEPENDENT reaction or CALVIN CYCLE

LIGHT DEPENDENT REACTION 1. Occurs only in light! 2. Takes place in thylakoid (Overview) H 2 O enters chloroplast (through xylem) Bonds holding H 2 O together are broken and H + ions and oxygen atoms are produced H + ions are used in making glucose. O 2 (waste product) is released through stomata. This is the oxygen we breathe.

Light Dependent Reaction (cont) 3. Light energy enters the thylakoid in the plant’s chloroplasts. 4. This energy is converted into chemical energy and is stored in two chemical compounds through electron transport chains. ATP (Adenosine Triphosphate) NADPH (Nicotinamide Adenine Trinucleotide Phosphate) 5. Electron transport chains are used for extracting energy from sunlight

Light Dependent Reaction The light energy hasn’t been created or destroyed by the plant, but it has changed form.*form.* Light energy transformed into Chemical Energy (energy stored in the chemical bonds of ATP and NADPH) ADP + P  ATP NADP + H  NADPH

Fact Check – Light Dependent Reaction 1. In which part of the chloroplast does the light dependent reaction occur? 2. Which two high energy molecules are produced using the light energy from the sun? 3. What is the “waste product” of the light dependent reaction? 4. How does this waste product exit the plant cells? 5. Which part of the water molecule is used to make a molecule of glucose? 6. What is the role of sunlight in the process of photosynthesis?

Light Independent Reaction or Calvin Cycle 1. Occurs in stroma – the space surrounding the thylakoid membranes 2. Takes place in light OR dark

Light Independent Reaction or Calvin Cycle 3. CO 2 enters chloroplasts through stomata. 4. Energy stored during the light dependent reaction (ATP and NADPH) is used to convert carbon dioxide and H + ions (from water) into glucose.

Light Independent Reaction or Calvin Cycle Chemical Energy in ATP + NADPH H + + CO 2  Glucose Low energy bonds in CO 2 High energy bonds in glucose Low energy ADP + NADP + (Available for light dependent reaction)

Photosynthesis Equation! 6CO 2 + 6H 2 0  C 6 H O 2 Reactants Products

Fact Check – Light Independent Reaction 1. In which part of the chloroplast does the light independent reaction occur? 2. What is another name for the Light Independent Reaction? 3. Why is it called the Light Independent Reaction? 4. Which molecule is added to H - (from the light dependent reaction) to make glucose? 5. How does the molecule referred to in #4 enter the chloroplast? 6. Which molecule is used to provide the chemical energy for the high energy bonds holding glucose molecules together?

Factors affecting Photosynthesis  Light - Absence of light  no photosynthesis  Increase in light intensity increases rate of reaction (up to a point—this point is dependent on the particular species of plant)  Water - Absence of water slows or stops the process  Temperature – Occurs at  0  C   35  C (dependent on the ecosystem) Would you expect a shortage of CO 2 to be a problem for plant growth on earth? Why or why not?

Factors Affecting Photosynthesis