Photosynthesis

Energy & Life Energy is the ability to do work. – It comes in many forms: light, heat, electricity. – Can be stored in chemical compounds, used to build new molecules, contract muscles and carry out active transport. – Without the ability to obtain and use energy, life wouldn’t exist.

Chemical Energy & ATP –One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP). – 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 consists of adenine (nucleotide), a 5-carbon sugar (ribose), and three phosphate groups.

Storing and Releasing Energy –Storing Energy Adenosine diphosphate (ADP) looks almost like ATP, except that it has two (di) phosphate groups instead of three (tri). ADP doesn’t contain as much energy as ATP When energy is available, small amounts are stored by adding phosphate groups to ADP making ATP. ADP is like a rechargeable battery that powers the machinery of the cell –Releasing Energy Cells release the energy stored in ATP by breaking the bonds between the second and third phosphate groups. Adding and subtracting phosphate groups is an efficient way of storing and releasing energy as needed.

Using this Energy Active transport is carried out by ATP. – Sodium-potassium pumps work and help maintain homeostasis by ATP ATP powers movement – Contracting muscles, power cilia and flagella ATP powers synthesis of proteins and responses of chemical signals at cell surface ATP is NOT good for storing large amounts of energy for long periods of time. ADP easily makes ATP from foods like glucose

Autotrophs –Organisms that make their own food are called autotrophs. –Plants, algae, and some bacteria are able to use light energy from the sun to produce food. The process by which autotrophs use the energy of sunlight to produce high-energy carbohydrates that can be used for food is known as photosynthesis.

Heterotrophs –Organisms that obtain food by consuming other living things are known as heterotrophs. Some get food by eating plants. –Others, such as a cheetah, obtain food from plants indirectly by feeding on plant- eating animals. –Others, such as mushrooms, obtain food by decomposing other organisms

Light The sun’s energy travels to Earth in the form of light with varying wavelengths many of which we can see making up the visible light spectrum Plants absorb the sun’s energy with light absorbing molecules called pigments.

Absorbing Light Chlorophyll is the main pigment plants use to absorb light. – chlorophyll a and chlorophyll b which absorb light in the blue and red region of the light spectrum. – Plants reflect green light which is why they look green.

Leaves There are other pigments that absorb other colors of light in the spectrum, but they are not as strong. The green chlorophyll pigments overwhelm the rest of the plant, but when temps. Drop chlorophyll breaks down allowing other colors to be seen. (Fall leaves)

Chloroplasts Chlorophyll is located in the chloroplasts on the thylakoid membrane. (light reaction) The fluid portion outside the thylakoid are called the stroma. (Calvin cycle)

Chloroplasts Light is a form of energy, so chloroplasts absorb energy. This energy gets transferred to electrons which make photosynthesis work. These electrons need to be carried to other parts of the chloroplast to carry out photosynthesis.

High-Energy Electrons –NADP + (nicotinamide adenine dinucleotide phosphate) is a carrier molecule. –NADP + accepts and holds two high-energy electrons, along with a hydrogen ion (H + ). In this way, it is converted into NADPH. –The NADPH can then carry the high-energy electrons to chemical reactions elsewhere in the cell.

Photosynthesis –Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high- energy sugars and oxygen. –In symbols: 6 CO H 2 O  C 6 H 12 O O 2 –In words: Carbon dioxide + Water  Sugars + Oxygen These simple sugar products combine to make complex sugars like starch and cellulose.

Two Reactions Light Dependent Light Independent