Energy and Life: An overview of Photosynthesis

Objectives Compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter (TEKS 9B) Where do plants get the energy they need to produce food? What is the role of ATP in cellular activities? What is the equation for photosynthesis? What is the role of light and chlorophyll in photosynthesis?

Without a constant input of energy, living systems cannot function. Sunlight is the main energy source for life on Earth.

Autotrophs Autotrophs - organisms that produce their own food. Plants, algae, and certain bacteria are able to use light energy from the sun to produce food in a process called photosynthesis. Autotrophs are also called producers

Heterotrophs Many organisms cannot harness energy directly from the physical environment. Organisms that rely on other organisms for their energy and food supply are called heterotrophs. Heterotrophs are also called consumers.

Objectives Compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter (TEKS 9B) Where do plants get the energy they need to produce food? What is the role of ATP in cellular activities? What is the equation for photosynthesis? What is the role of light and chlorophyll in photosynthesis?

Chemical Energy and ATP Energy comes in many forms (Ex. light, heat, electricity). Energy can also be stored in chemical compounds. Don’t forget, photosynthesis captures energy from the sun and converts it to chemical energy. Why do we need this chemical energy?

Chemical Energy and ATP Homeostasis (internal stability) is hard work. Organisms and the cells within them have to grow and develop, move materials around, build new molecules, and respond to environmental changes. Chemical energy in cells is what powers all these activities.

Chemical Energy and ATP An important chemical compound that cells use to store and release energy is adenosine triphosphate, abbreviated ATP. ATP is used by all types of cells as their basic energy source. ATP consists of: adenine ribose (a 5-carbon sugar) 3 phosphate groups

ATP: Storing and Releasing Energy ATP can easily release and store energy by breaking and re-forming the bonds between its phosphate groups. This characteristic of ATP makes it exceptionally useful as a basic energy source for all cells.

ATP: Storing Energy Adenosine diphosphate (ADP) looks almost like ATP, except that it has two phosphate groups instead of three. ADP contains some energy, but not as much as ATP. When a cell has energy available, it can store small amounts of it by adding phosphate groups to ADP, producing ATP. ADP is like a rechargeable battery that powers the machinery of the cell.

ATP: Releasing Energy Cells can release the energy stored in ATP by breaking the bonds between the second and third phosphate groups. Because a cell can add or subtract these phosphate groups, it has an efficient way of storing and releasing energy as needed.

Using Biochemical Energy Energy from ATP can do many things including powering the synthesis of proteins and responses to chemical signals at the cell surface. ATP is not a good molecule for storing large amounts of energy over the long term, however. WHY?

Using Biochemical Energy A single molecule of glucose stores more than 90 times the chemical energy of a molecule of ATP. 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 foods like glucose.

Objectives Compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter (TEKS 9B) Where do plants get the energy they need to produce food? What is the role of ATP in cellular activities? What is the equation for photosynthesis? What is the role of light and chlorophyll in photosynthesis?

Photosynthesis: An Overview Photosynthesis - autotrophs use light energy to convert carbon dioxide and water into oxygen and energy-rich carbohydrates. -This process is responsible for adding O2 to atmosphere and removing CO2

Photosynthesis: An Overview The equation for photosynthesis is: 6CO2 + 6H2O C6H12O6 + 6O2 carbon dioxide + water glucose + oxygen LIGHT LIGHT

Photosynthesis: An Overview Remember: A chemical reaction is a process that changes one set of chemicals into another set of chemicals

Photosynthesis: An Overview The elements or compounds that enter into a chemical reaction are known as reactants. The elements or compounds produced by a chemical reaction are known as products.

Objectives Compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter (TEKS 9B) Where do plants get the energy they need to produce food? What is the role of ATP in cellular activities? What is the equation for photosynthesis? What is the role of light and chlorophyll in photosynthesis?

How DO plants capture the energy of sunlight? Light and Pigments How DO plants capture the energy of sunlight?

Light and Pigments Plants gather the sun's energy with light-absorbing molecules called pigments. The main pigment in plants is chlorophyll. There are two main types of chlorophyll: chlorophyll a chlorophyll b

Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum Chlorophyll does NOT absorb light well in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green.

Light and Pigments Light is a form of energy, so any compound that absorbs light also absorbs energy from that light. When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons are what make photosynthesis work.