Photosynthesis Process by which a plant cell captures sunlight and uses it to make food Introduction to the definition of photosynthesis

Nearly all living things obtain energy either directly or indirectly from the energy of sunlight captured during Photosynthesis Plants get their energy directly from the sun…other animals get their energy indirectly from the sun by eating other animals that have either eaten plants or eaten other animals that ate animals that ate plants.

Plants, such as grass, use energy from the sun to make it’s own food, and are called an autotroph Definition of autotrophs…organisms that get their energy directly from the sun

A caterpillar obtains energy from eating grass and the bird obtains energy by feeding on the caterpillar. These organisms cannot make their own food and are called heterotrophs. Definition of heterotrophs…organisms that get their energy by eating animals that either ate plants or animals that ate animals that eat plants.

During photosynthesis, autotrophs use the sun’s energy to convert carbon dioxide (CO2) and water (H2O) into oxygen (O2) and sugars (C6H12O6) Inputs and outputs of photosynthesis.

Oxygen CO2 Glucose Photosynthesis Sun’s Energy Have them make a diagram in their ISN. Glucose

Two Stages of “Photo” “synthesis” What does the term “photo” mean? (light). What does the term “synthesis” mean? (put together different substances to make something else…in this case put together light, water, and CO2 to make (synthesize) oxygen and sugars.

Stage 1: Capturing Sun’s Energy Process occurs mostly in leaves Chloroplasts in plant cells capture sun’s energy using photosynthetic pigments called chlorophylls Energy powers stage 2 Stage 1. Next slide is on Chlorophyll. Focus on inputs and outputs of capturing sun’s energy. Water in, light energy is captured.

Chorophyll Green pigment present in green plants Essential in the transformation of light energy to chemical energy. Chlorophyll absorbs light mostly in the blue and red ends of the visible spectrum, and very little in the green wavelengths. That green light is reflected, giving us the leaf color we see. Chlorophyll the light collecting pigments in plants. Tell students there are other light collecting pigments in plants that absorb and reflect light in different wavelengths of the absorption spectrum resulting in different color plants. The prism is an example of how the white light is absorbed and the colors of the light spectrum are reflected.

Stage 2: Using Energy to Make Food Cells need H2O and CO2 for this stage. CO2 enters leaves through stomata, H2O enters through roots CO2 and H2O undergo chemical reactions in chloroplasts to produce sugars (C6H12O6) and oxygen which exit the leaves through stomata. Stage 2: focus on inputs: CO2 enters through the stomatas (next slide covers their structure). Water enters through the roots and moves up to the leaves where they both undergo chemical reactions to produce oxygen and sugars (like glucose)

Stomata CO2 enters plants through the stomates on underside of leaf. Guard cells around stoma opening will open and close depending upon water concentration in leaf. Stomata’s on the underside of the leaf. Note that plants are adapted to different climates by their number of stomatas. The hotter, more dry a climate is, the less stomatas a leaf will have and the more often they will be closed and undergo a slower rate of photosynthesis. Leaf size will tend to be small (smaller surface area). The wetter, more humid a climate, the more stomatas a leaf will have and will undergo more rapid photosynthesis…leaf surface area will tend to be larger. Hot, dry climates with limited water  fewer stomates on underside of leaf Wet, humid climates with plenty of water available  greater number of stomates on underside of leaf

Stomata in mums

Stomata in four leaf clover