All living things need energy. Whether it’s the little field mouse or The big ole owl

Energy is needed for all of life’s functions for ALL forms of life. Remember life functions? Like reproduction, nutrition, transport, respiration, regulation, excretion, growth …

Most cells have only a small amount of ATP, enough to last for only a few seconds of activity. Why is this? Even though ATP is very efficient at transferring energy, it is not very good for storing large amounts of energy over the long term. In fact, a single molecule of the sugar glucose stores more than 90 times the chemical energy of a molecule of ATP. Therefore, it is more efficient for cells to keep only a small supply of ATP on hand. Cells can regenerate ATP from ADP as needed by using the energy in carbohydrates like glucose.

But where is that glucose coming from?????

Some organisms are able to use a source of energy, such as sunlight, to produce food directly from simple inorganic molecules in the environment. These organisms are called: AUTOTROPHS There are: photoautotrophs Those that use the sunlight as their energy source and chemoautotrophs Those that use inorganic chemicals for energy

PHOTOAUTOTROPHS Let’s examine how sunlight is used as an energy source. “White Light” is a mixture of all of the different wavelengths of light. Remember the visible spectrum??? That’s made up of light visible to our eyes. Like red, orange, yellow, green, blue, indigo and violet. The visible spectrum ranges from 380 nm (violet) to 700 nm (red)

Inside the plant, there are these structures called CHLOROPLASTS And inside the chloroplasts there are these colored PIGMENTS Which are colored substances that absorb or reflect light. The principal pigment of green plants is Chlorophyll Chlorophyll absorbs red and blue light but does not absorb light in the in the middle region of the spectrum Chlorophyll a is the main photosynthetic pigment in plants. Thus….we see GREEN

Before we begin, we must discuss the structure where photosynthesis occurs The Chloroplast Within each leaf there are many cells. Within the cells are many oval shaped organelles called chloroplasts. Each chloroplast contains all the necessary components needed for photosynthesis to take place.

Electron microgram of a chloroplast showing the granum and the thylakoid membrane

The sun’s energy (light) comes down on photosynthetic organisms, like plants

Although we always think of energy as waves, energy also travels as particles called photons. And, there are other pigments in plants besides chlorophyll a Like chlorophyll b and the carotenoids (the pigments that give us the oranges and yellows of fall) When photons of light strike pigments other than the main pigment, chlorophyll a They send that energy to chlorophyll a, the main pigment. By having other pigments, plants can use a broader spectrum of light for photosynthesis

And now the process begins! Photosynthesis is a two-step process. Step one is called the light reactions or the light dependent reactions. The light reactions take place in the thylakoid membrane of the chloroplast In the light reaction the energy of sunlight is captured and used to make energy-storing compounds. The light reactions use water, ADP and NADP+ (an electron carrier) They produce O 2 (which is of no help in photosynthesis but is of great use to us) and the energy-storing molecules ATP and NADPH.

1. Is absorbed The Light Reactions are so called because they require light to function. 2. A water molecule is taken in and then split 3. The oxygen from splitting water is released 4. High energy molecules are formed

But How is glucose formed?

Glucose is formed in the Dark Reactions (so called because they do not require light) from six molecules of carbon dioxide The dark reactions are fueled by the high energy molecules formed in the light reaction ATP and NADPH

The dark reactions take place in the stroma of the chloroplast

Plants require carbohydrates or sugars for survival and growth The Calvin Cycle is a means of converting CO 2, energy rich molecules from the light reactions and various intermediate molecules to produce these needed sugars such as GLUCOSE

CO 2 ATP NADPH Glucose

Let’s look at an overview of the process of photosynthesis.

Let’s examine the chemical equation for photosynthesis.

What Factors Affect Photosynthesis Because water is one of the raw materials of photosynthesis, a shortage of water can slow or even stop photosynthesis. Plants that live in dry conditions, such as desert plants and conifers, have a waxy coating on their leaves that reduces water loss Temperature is also a factor. Photosynthesis depends on enzymes that function best between 0°C and 35°C. Temperatures above or below this range may damage the enzymes, slowing down the rate of photosynthesis. At very low temperatures, photosynthesis may stop entirely.

The conifers can carry out photosynthesis only on sunny days The intensity of light also affects the rate at which photosynthesis occurs As you might expect, increasing light intensity increases the rate of photosynthesis. After the light intensity reaches a certain level, however, the plant reaches its maximum rate of photosynthesis. The level at which light intensity no longer affects photosynthesis varies from plant type to plant type

Some Quick Plant Biology Plant parts to remember for photosynthesis: LEAVES: Where photosynthesis takes place STOMATA: Located on the undersides of the leaves Allows CO 2 and O 2 to diffuse into and out of the leaf GUARD CELLS: Specialized cell in epidermis of plant that controls the opening and closing of stomata by responding to changes in water pressure

VASCULAR TISSUES: XYLEM: Carries water upward from the roots to every part of a plant PHLOEM: transports solutions of nutrients and carbohydrates produced by photosynthesis.

Transport in Plants Root pressure forces water into the xylem, but root pressure alone cannot account for the movement of water and dissolved materials in plants. ADHESION, COHESION AND CAPILLARITY. Water molecules are attracted to one another by a force called COHESION. ADHESION is the interaction between surfaces of DIFFERENT molecules The combination of cohesion and adhesion explains the phenomenon known as CAPILLARITY - the movement of water upward in a small solid tube.

TRANSPIRATION - Evaporation of water from plant leaves Most evaporation/transpiration takes place thru the STOMATES

SYMBIOTIC RELATIONSHIP MYCORRHIZAE – an association of roots and fungi The formation of mycorrhizae allows plants to receive nutrients from the fungi, while the fungi receive fixed carbon from the plant roots.