Photosynthesis

What are autotrophs? Why are they important?

 Energy for Life AUTOTROPHS are organisms that can make their own food. Also called PRODUCERS. Ex. PLANTS, ALGAE

 Energy for Life HETEROTROPHS are organisms that depend on other organisms for food. Also called CONSUMERS. Ex. ANIMALS, BACTERIA

 Energy for Life TWO biological processes are needed to create usable energy for organisms. Photosynthesis – the process that converts sunlight into sugar. (autotrophs only) Respiration – process that releases energy in sugar into usable energy for cells. (autotrophs and heterotrophs)

ATP  Adenosine triphosphate (ATP) – energy storage molecule. Adenine (nitrogen base) Ribose (sugar) 3 Phosphate groups

ATP  ATP is the universal currency for energy ATP stores energy in the BONDS BETWEEN THE PHOSPHATE GROUPS. When a BOND IS BROKEN energy is released. ATP (tri) ADP (di) + phosphate energy +

Structure of a Chloroplast  Structure of a Chloroplast A chloroplast is the structure in a plant cell where photosynthesis occurs. Internal Structure: Thylakoid membrane – internal membrane, look like stacks of pancakes. Lumen – space inside thylakoid membrane. Grana – stacks of thylakoids. Stroma – solution that thylakoids are embedded in.

Structure of a Chloroplast

Pigments  Pigments are light absorbing molecules. Each pigment absorbs and reflects different wavelengths of light. (we see the reflected color)

Pigments  CHLOROPHYLL is the primary pigment in photosynthesis. Gives plants their GREEN color. CAROTENOIDS are accessory pigments that absorb light that chlorophyll cannot. They are YELLOW, ORANGE, AND BROWN.

Checkpoint Why do leaves turn yellow, orange and brown in the fall? Production of chlorophyll is slowed down in the fall due to lower temperatures and less sunlight!

Pigments

Photosynthesis  6 CO2 + 6 H2O + sunlight C6H12O6 + 6O2 Glucose Carbon Dioxide Oxygen Water  6 CO2 + 6 H2O + sunlight C6H12O6 + 6O2 Photosynthesis song :)

 Van Helmont Measured plant mass and soil mass before and after 5 years of growth Most of gain in mass came from water

Priestly Candle with a jar over it would die out Required oxygen Sprig of mint plus candle caused candle to last longer Plant produced oxygen

Ingenhousz Effect showed by Priestly occurred only in the presence of light

Photosynthesis There are two stages to photosynthesis, the light-dependent reactions and light-independent (dark) reactions.

Light-dependent Reactions  Light-dependent Reactions Occur in the THYLAKOID MEMBRANES. Light is absorbed by chlorophyll in Photosystem II and electrons are excited. The excited electrons move through a series of reactions – the electron transport chain.

Light-dependent Reactions

Light-dependent Reactions The light energy splits water molecules into H and O2 The O2 is released into the atmosphere and the H bonds to a carrier molecule (NADPH) to be carried to the Dark Reactions. Splitting the water also creates ATP.

 Light Reactions Sunlight, water, and CO2 Chloroplast Light- dependent Reactions Chloroplast Light Reactions ATP ATP ATP NADPH NADPH NADPH O2 The end products of the light reactions are NADPH, ATP, and O2

Light-independent Reactions  Light-independent Reactions Don’t Require LIGHT Also called the DARK REACTIONS OR THE CALVIN CYCLE. Occur in the STROMA Melvin Calvin

Light-independent Reactions  Light-independent Reactions Carbon dioxide enters the plant and attaches to a sugar molecule. This is called carbon fixation Carbon Dioxide, NADPH, and ATP combine with enzymes to make glucose (C6H12O6) and more CO2.

Dark Reactions  Light, water, and CO2 CO2 NADP+ Carbon Fixation Chloroplast Chloroplast NADP+ Carbon Fixation ADP + P Light- dependent Reactions Light- independent Reactions NADPH+H ATP Glucose

Factors Affecting Photosynthesis  Factors Affecting Photosynthesis Light Intensity – the more light the faster the rate of photosynthesis. CO2 Concentration – the more CO2, the faster the rate of photosynthesis. Temperature – rate of photosynthesis slows down at extremes of hot or cold. Photosynthesis video