Photosynthesis

Question 1

How do plants convert light energy to chemical energy?

Answer 1

1. light energy forces electrons to a higher energy level in the two chlorophyll a molecules of photosystem II. These energized are said to be “excited”. The excited electrons have enough energy to leave the chlorophyll a molecules. Because they have lost electrons, the chlorophyll a molecules have undergone an oxidation reaction. These substances must accept the electrons that the chlorophyll a molecules have lost. 2. The acceptor of the electrons lost from chlorophyll a is a molecule in the thylakoid membrane called the primary electron acceptor. 3. The primary electron acceptor donates the electrons to the first of a series of molecules located in the thylakoid membrane. These molecules are called an electron transport chain because they transfer electrons from one molecule to the next. As the electrons pass from molecule to molecule in the chain, they lose most of the energy that they acquired when they were excited. The energy they lose is used to move protons (H+) into the thylakoid. 4. Light is absorbed by photosystem II. Electrons move from a pair of chlorophyll a molecules in photosystem I to another primary electron acceptor. The electrons lost by these chlorophyll a molecules are replaced by the electrons that have passed through the electron transport chain from photosystem II. The primary electron of photosystem I donates electrons to a different electron transport chain. This chain brings the electrons to the side of the thylakoid membrane that faces the stroma. There the electrons combine with a proton and NADP+, an organic molecule that accepts electrons during oxidation/ reduction reactions. 5. this reaction causes NADP+ to be reduced to NADPH.

Question 2

Chemiomosis

Answer 2

The synthesis of ATP through this process.

Question 3

Calvin Cycle

Answer 3

Is a series of enzyme-assisted chemical reactions that produces a three-carbon sugar.

Question 4

What are the steps in the Calvin Cycle?

Answer 4

1. CO2 diffuses into the stroma from the surrounding cytosol. An enzyme each CO2 molecule with a five-carbon molecule called ribulose biphosphate (RuBP). The six-carbon molecules that result are very unstable, and they each immediately into two three-carbon molecules. These three-carbon are called 3-phophoglycerate (3-PGA). 2. Each molecule of 3-PGA is converted into another three-carbon molecule, gyceraldehyde 3-phosphate (G3P), in a two-part process. First, each 3-PGA molecule receives a phosphate group from a molecule of ATP. The resulting compound then receives a proton (H+) from NADPH and releases a phosphate group, producing G3P. The ADP, NADP+, and phosphate that are also produced can be used again in the light reactions to make more ATP and NADPH. 3. One of the G3P molecules leaves the Calvin Cycle and is used to make organic compounds (carbohydrates) in which energy is stored for later use. 4. the remaining G3P molecules are converted back into RuBP through the addition of phosphate groups from ATP molecules. The resulting RuBP molecules then enter the Calvin cycle again.

Question 5

pigment

Answer 5

molecule that absorbs certain wavelengths of light and reflects or transmits others.

Question 6

chlorophyll

Answer 6

most common and most important photosynthetic pigment in plants and algae.

Question 7

chloroplasts

Answer 7

organelles that contain chlorophyll.

Question 8

Stroma

Answer 8

gel-like material that surrounds the thylakoids.

Question 9

Grana

Answer 9

stacks of disk-shaped structures that contain chlorophyll.

Question 10

Photosystems

Answer 10

light-collecting units of the chloroplast.

Question 11

is H2O light dependent or independent? in the thylakoid disc or in the stroma?

Answer 11

dependent, thylakoid disc

Question 12

Light energy is initially captured by “photosystems”. Photosystems are organized arrays of?

Answer 12

Pigment Molecules

Question 13

Why is carbon dioxide a key molecule in the light-molecule in the light-independent reactions of photosynthesis?

Answer 13

Carbon dioxide is the raw material for the synthesis of sugars.

Question 14

Oxygen is used by mitochondria to generate ATP from sugars and other foods molecules.

Answer 14

The oxygen in the air is generated by the splitting of water during the light dependent reactions of photosynthesis.

Question 15

The energy that is used to establish the proton gradient across the thylakoid membrane comes from the.

Answer 15

Passage of electrons along the electron transport chain in photosystem II.

Question 16

What product of the light reactions of photosynthesis is released and does not participate further in photosynthesis?

Answer 16

Oxygen

Question 17

Disk-shaped structures with photosynthetic pigments are known as a.

Answer 17

Thylakoids

Question 18

Water participates directly in the light reactions of photosynthesis by

Answer 18

Donating electrons to photosystem II.