Chapter 8 Photosynthesis UNIT III Chapter 8 Photosynthesis

I. Energy and Life A. Autotrophs 1. Organisms that make their own food. (includes plants and certain chemosynthetic organisms) 2. Plants (and some other organisms) use light energy from sun and turn it into chemical energy (food)

B. Heterotrophs-organisms that obtain energy from foods they consume by releasing the energy in sugars and other compounds

C. Chemical Energy and ATP 1. Energy comes in many forms. E.g. Light, heat, electricity, chemical compounds, sound, etc.

2. ATP and ADP- chemical fuels that power activities of the cell a. Adenosine triphosphate (ATP)- stores energy in phosphate bonds. Powers all of cells activities

ATP  ADP + P + Energy ADP  AMP + P + Energy AMP + P + Energy  ADP b. Adenosine diphosphate (ADP)- ATP gives up some energy and a phosphate group. ADP becomes AMP when gives up more energy and another phosphate group. ATP  ADP + P + Energy ADP  AMP + P + Energy AMP + P + Energy  ADP ADP + P + Energy  ATP

II. Photosynthesis: An Overview A. Investigating Photosynthesis 1. Van Helmont’s Experiment- devised experiment to find out if plants grew by taking material out of soil. a. Determined mass of pot of dry soil and small seedling b. Watered it regularly for 5 years c. After five years weighed the small tree- 75 kg. Mass of soil remained unchanged d. Concluded that mass of tree came from water (experiment accounts for “hydrate portion of carbohydrate

2. Priestley’s experiment- 100 years after Helmont’s experiment. a. Put candle with glass jar over it- flame died out. Said something in air necessary for candle (oxygen) b. Put live sprig of mint under jar for a few days and the candle could be relighted and would remain lighted for a while c. Concluded mint plant produced substance required for burning (oxygen)

3. Jan Ingenhousz- showed that Priestley’s experiment only occurred when the plant was exposed to light. Proved that light is necessary for plants to produce oxygen

B. The Photosynthesis Equation 1. Energy from sunlight converts water and carbon dioxide into oxygen and high-energy sugars. light 6CO2 + 6H2O C6H12O6 + 6O2 2. Takes place in Chlorplasts

C. Light and Pigments 1. Plants use chemicals called pigments to trap light energy 2. Plants principle pigment is chlorophyll (two types, a and b)

3. Each type of pigment absorbs different wavelengths of light (white light is made up of all colors of spectrum) 4. Accessory Pigments- absorb light energy in other portions of the light spectrum (e.g. Carotene- red/orange pigment) 5. Light energizes electrons in chlorophyll molecules (raising energy level of electrons

III. The Reactions of Photosynthesis A. Inside the Chloroplast 1. Photosynthesis takes place in chloroplasts

2. Contain saclike membranes called thylakoids

a. Arranged in stacks called grana (singular: granum)

b. Thylakoids contain clusters of chlorophyll and other pigments and proteins known as photosystems- can capture light energy

B. NADP+ (molecules that transfer excited electrons energy from chlorophyll molecule) nicotinamide adenine dinucleotide phosphate 1. Transfers high energy electrons (like “hot coals” from fire) from chlorophyll to other molecules 2. Takes NADP+ + 2 high-energy electrons + H+ and converts it to NADPH (think of this as a pan or bucket to carry “hot coals”) 3. NADPH can then carry energy to other places in cell to help build a variety of molecules like glucose

C. Light-Dependent Reaction (requires light) 1. Uses energy from light to convert ADP and NADP+ to ATP and NADPH 2. Produces oxygen gas as a by product 3. Takes place in the thylakoid membrane of the chloroplasts

D. The Calvin Cycle- does not require light D. The Calvin Cycle- does not require light. Also called light-independent reaction 1. Calvin cycle uses ATP and NADPH from light-dependent reaction to produce high-energy sugars 2. Carbon dioxide molecules turned into 6-carbon sugars (glucose) and other compounds (starches, cellulose) 3. Takes place in stroma of chloroplasts

E. Factors Affecting Photosynthesis- many factors affect rate at which photosynthesis occurs 1. Shortage of water- can slow or stop process 2. Temperature is factor- photosynthetic enzymes work best between 0° and 35°C. 3. Intensity of light- plants adapted for different levels of light (e.g. shade plants, red algae, ferns, etc.

Which of the graphs represents the effect of light intensity on the rate of photosynthesis?

Which of the graphs represents the effect of light intensity on the rate of photosynthesis?

Which of the graphs represents the effect of temperature on the rate of photosynthesis?

Which of the graphs represents the effect of temperature on the rate of photosynthesis?

Summary of Photosynthesis

Equation of Photosynthesis light C6H12O6 + 6O2 6CO2 + 6H2O

Equation of Light Reaction NADPH + O2 + H+ + ATP H2O + NADP+ + ADP + P Takes place in thylakoids

Equation of Calvin Cycle (Light Independent Reaction) C6H12O6 + ADP + NADP+ +H2O NADPH + ATP + CO2 Takes place in the Stroma

Photosynthesis Review

Organisms, such as plants, that make their own food are called a. autotrophs. b. heterotrophs. c. thylakoids. d. pigments.

Organisms, such as plants, that make their own food are called a. autotrophs. b. heterotrophs. c. thylakoids. d. pigments.

Organisms that cannot make their own food and must obtain energy from the foods they eat are called a. autotrophs. b. heterotrophs. c. thylakoids. d. plants.

Organisms that cannot make their own food and must obtain energy from the foods they eat are called a. autotrophs. b. heterotrophs. c. thylakoids. d. plants.

Which of the following is an autotroph? a. mushroom b. dog c. monkey d. tree

d. tree Which of the following is an autotroph? a. mushroom b. dog c. monkey d. tree