Chapter 4 Biology

What is potential energy?

Energy of position or stored energy. Ex. -Water behind dam -Concentration gradient -Chemical energy

Energy Movement Through Chlorophyll

1. Light energy bumps an electron in the chlorophyll molecule to a higher, excited energy level. 2. The excited electron generally has one of two different fates: Some energy is transferred to a nearby molecule, where it excites another electron. or The excited electron is transferred to a nearby molecule.

The Photosystem (Water Splitting)

1. Light energy excites electrons in a pigment molecule (such as a chlorophyll molecule). The energy from the excited electrons is transferred to a nearby molecule. 2. When transferred energy excites electrons in the chlorophyll a molecule, the primary electron acceptor grabs them and sends them to the electron transport chain. 3. To replace electrons sent to the electron transport chain, water molecules are split and oxygen and hydrogen are released as by-products.

Summary of "Photo" Reaction Components

1. Water Splitting Photosystem- Light energy is used to transfer electrons to the primary electron acceptor. Electrons are donated by water, releasing oxygen and hydrogen ions as by-products. 2. 1ST Electron Transport Chain- High energy electrons are used to pump hydrogen ions into the thylakoid. The kinetic energy from the release of these ions is used to build ATP. 3. NADPH-Producing Photosystem- The NADPH-producing photosystem is identical to the water-splitting photosystem, except that electrons are donated by the electron transport chain. 4. 2nd Electron Transport Chain- High-energy electrons are passed to NADP+, creating NADPH, a high energy electron carrier.

Calvin Cycle

3 Step Process 1.Fixation- First, using an enzyme called rubisco, plants pluck carbon from the air, where it occurs in the form of carbon dioxide, and then attach, or "fix," it to a visible organic (carbon-containing) molecule within the chloroplast. Not surprisingly, given its role as the critical chemical that enables plants to build food molecules, rubisco is the most abundant protein on earth. 2. Sugar Creation- The newly built molecule is chemically modified: a phosphate from ATP is added, and the molecule receives some high-energy electrons from NADPH. This product of the Calvin Cycle is a small sugar called glyceraldehyde 3-phosphate (G3P) Some of the G3P molecules are combined to make the six-carbon sugars and fructose. These sugars can be used as fuel by the plant, enabling it to grow. They can also be used as fuel by animals that eat the plant. 3. Regeneration- Not all of the G3P molecules are used to produce sugars. In the third and final phase of the Calvin Cycle, some G3P molecules are used to regenerate the original molecule in the chloroplast to which the carbon from CO2 is attached. This regeneration process requires energy from ATP produced in the "photo" reactions of photosynthesis. With this regeneration, the Calvin Cycle can continue to fix carbon and produce molecules of G3P. Ultimately, to synthesize one molecule of G3P, the Calvin Cycle must fix 3 atoms of carbon from carbon dioxide to initiate the organic molecule; this process consumes 9 molecules of ATP and 6 molecules of NADPH generated in the "photo" reactions of photosynthesis.

What is the third component that makes ATP so effective?

A chain of three negatively charged phosphate groups

What is at the center of the ATP molecule?

A small sugar molecule attached to a molecule called adenine.

How many components does ATP have?

ATP has 3 components

Carotenoids

Absorb blue-violet and blue-green wavelengths and reflect red, yellow, and orange wavelengths.

Chlorophyll B

Absorbs blue and red-orange wavelengths. Chlorophyll b reflects yellow-green wavelengths.

C3 Photosynthesis

Advantages -energy efficient Disadvantages -water lost to evaporation in hot climates

CAM Photosynthesis

Advantages -water loss is minimized in hot climates Disadvantages -requires more energy -slow growth

What is all life on earth dependent upon?

All life on earth is completely dependent on the continued excitation of electrons by sunlight.

Where does all of the Calvin Cycle reactions occur?

All the Calvin Cycle reactions occur in the stroma of the leaves' chloroplasts, outside the thylakoids.

What is kinetic energy?

Energy of movement. Ex. -flapping wings -heat energy -light energy

When plants grow, where does the new tissue come from?

Carbon dioxide from the atmosphere.

Where are Chlorophyll molecules found?

Chlorophyll molecules are embedded in the thylakoid membrane of chloroplasts.

How does ATP rebuild itself?

Each time a cell expends one of its ATP molecules to pay for an energetically expensive reaction, a phosphate is broken off and energy is released. What is left is a molecule with two phosphates called ADP, and a separate phosphate group. An organism can then use ADP, a free-floating phosphate, and an input of kinetic energy to rebuild its ATP stocks. The kinetic energy is converted to potential when the free phosphate group attaches to the ADP molecule and makes ATP.

How are electrons in Chlorophyll excited?

Electrons in a plant's chlorophyll can become excited by certain wavelengths of light and can capture a bit of this energy.

Why are leaves green?

Leaves are green because the cells near the surface are packed full of chloroplasts.

What are pigments?

Light absorbing molecules.

What are three inputs required for the process of photosynthesis?

Light energy (sun), carbon dioxide (from the atmosphere), and water (from the ground)

What is light energy and what is it made of?

Light energy is a type of kinetic energy made up little energy packets called photons.

Chloroplast

Light harvesting organelles, which make it possible for the plant to use the energy from sunlight to make sugars (their food) and other plant tissue (much of which animals use for food)

What happens in the "photo" segment of photosynthesis?

Light is captured.

Where are most chloroplast located?

Located within the cells in a plant's leaves.

Thylakoid

Location of "photo" reactions, where light energy is converted to chemical energy.

Stroma

Location of "synthesis" reactions where chemical from the "photo" reactions is used to synthesize sugars.

What is one way of combating water loss for plants?

One way for plants to reduce water loss through evaporation is for plants to close their stomata.

What do photons do?

Photons hit chlorophyll and other light-absorbing molecules near the green surfaces of plants. These molecules capture some of the light energy and harness it to build sugar from carbon dioxide and water.

What is photosynthesis powered by?

Photosynthesis is powered by light energy.

Stomata

Small pores usually on the underside of leaves. These openings are the primary sites for gas exchange in plants: carbon dioxide for photosynthesis enters through these openings and oxygen generated as a by-product in photosynthesis exits through them.

What does the second law of thermodynamics state?

States that every conversion of energy is not perfectly efficient and invariably includes the transformation of some energy into heat.

What does the first law of thermodynamics state?

States the energy can never be created or destroyed. It can only change from one form to another.

What gets produced from the three inputs?

Sugar and Oxygen.

What happens in the "synthesis" segment of photosynthesis?

Sugar is built.

What is sugar used for by plants?

Sugar used to produce plant structures.

Where does the "synthesis" part of photosynthesis take place?

The "synthesis" part of photosynthesis takes place in a series of chemical reactions called the Calvin Cycle.

Passing of Electrons

The passing of electrons from molecule to molecule is one of the chief ways that energy moves through cells. Many molecules carry or accept electrons during cellular activities. All that is required is that the acceptor must have a greater attraction for them. This receiver molecule, in turn, hands off electrons to another acceptor with an even greater attraction fort them. A molecule that gains electrons always carries greater energy than it did before receiving the electrons.

C4 Photosynthesis

The plants produce an enzyme that functions like the ultimate "CO2-sticky tape." This enzyme has a tremendously strong attraction for carbon dioxide; it can find and bind carbon even when CO2 concentration is very low Advantages: -water loss is minimized in warm climates Disadvantages: -requires more energy

What is the primary photosynthetic pigment and what does it absorb?

The primary photosynthetic pigment, chlorophyll a, absorbs red and blue-violet wavelengths of light. Because chlorophyll a cannot effectively absorb green light and instead reflects those wavelengths.

Chlorophyll

The special molecule found in chloroplast that makes the capture of light energy possible.

What happens when the stomata is shut?

With the stomata shut, oxygen from the "photo" reactions of photosynthesis cannot be released from the chloroplasts, and carbon dioxide cannot enter.

Calorie

amount of energy that raises temperature of 1g of water by 1 degree Celsius.

Biofuels, Fossil Fuels and Food Fuels

i. chains of carbon and hydrogen atoms ii. energy is stored in the bonds

What is Photosynthesis?

plants capture energy from the sun and store it the chemical bonds of sugar and other food molecules.

What is Cellular Respiration?

plants, animals, and fungi release the energy stored in the chemical bonds of food molecules and use it as fuel.