Bio: Chapter 6 - Photosynthesis

The components of the light reactions, like the photosystems, electron transport chain, and ATP synthase, are all located near each other on the thylakoid membrane in order to minimize the amount of energy that the cell must use to transport the electrons and other materials throughout the chloroplast.

What is the advantage of having these components confined to the same membrane rather than dissolved in the stroma or the cytosol?

The primary electron acceptor is the original molecule that is the electron donor for both systems.

What is the original molecule that is the electron donor for the both of these systems?

The organic compounds used in photosynthesis would eventually run out, resulting in photosynthesis not being as productive because it doesn't have the necessary materials to perform its task.

What would happen to photosynthesis if all the three-carbon sugars produced in the Calvin cycle were used to make organic compounds?

ATP synthase

an enzyme that makes ATP by adding a phosphate group to ADP

ATP

an inorganic molecule that acts as the main energy source fir cell processes; composed of a nitrogenous base, a sugar, and three phosphate groups

heterotroph

animals and other organisms that must get energy from food instead of directly from the sunlight or inorganic substances

respiration

the process in which organisms USE energy; reactants: sugars (glucose) and oxygen products: carbon dioxide and water

photosynthesis

the process of converting light energy from the sun into chemical energy in the form of organic compounds, primarily carbohydrates

An increase in temperature increases the rate of photosynthesis. However, the rate peaks at a certain temperature and many enzymes become ineffective. The stomata begins to close, limiting water loss and carbon dioxide entry, and it causes the rate of photosynthesis to then decreases as the temperature further increases.

Explain how a global temperature increase could affect plants.

If there was no concentration gradient of proteins, light reactions, then, would be in a state of equilibrium and the two sides would be moving molecules at the same pace. If that happened, they wouldn't be trying to diffuse different substances to help the light reactions because it already reached the state it was eager to become.

Explain how the light reactions would be affected if there were no concentration gradient of protons across the thylakoid membrane.

In plants, the color is shown because of how much light is reflected or absorbed. However, in something like clothes, it is a specific color, and based on how light or dark the color is, determines how strong or how much light is absorbed into the object.

Explain how the pigments in color objects differ from plant pigments.

It might not because the system can only perform so quickly, and also even though you have an increased amount of light, you may not have enough other reactants. All the available electrons can then also be excited and the maximum rate of photosynthesis achieved.

Explain why increased light intensity might not result in an increased rate of photosynthesis.

Photosynthesis and the Calvin cycle are dependent upon each other because the organic substances made in photosynthesis are then used in the Calvin cycle and that goes for many other substances as well. Also, they happen on opposite sides of each other, so the product of one is used in the next.

Explain why the light reactions and the Calvin cycles are dependent on each other.

During photosynthesis, the proton concentration in the thylakoid becomes high. The protons diffuse outward, and powers the ATP synthase protein which has ADP go up, and goes through its processes to add a phosphate and it becomes ATP

How is ATP made during photosynthesis?

light, energy, carbon dioxide, and water are used in it. glucose (carbohydrate) and oxygen gas are produced. The products of photosynthesis are reactants in cellular respiration. Products in cellular respiration are reactants in photosynthesis.

Overview of Photosynthesis

Step 1: Light is absorbed by chlorophyll within the chloroplasts Step 2: The light absorbed excites electrons in photosystem II Step 3: electrons are passed down the electron transport chains Step 4: The proton concentration in the thylakoid is HIGH, and the diffusion of protons outward powers the ATP synthase protein Step 5: the second electron transport chain (beginning with photosystem I) - high energy, like ATP Step 6: water molecules are broken down in the photosystem, oxygen is released, electrons replace those used in light reactions, and some energy is used to pump additional H+ into thylakoid

Steps of Light Reactions

Step 1: carbon dioxide diffuses into stromas and is added to five-carbon compound called RuBP (happens three times - catalyzed by Rubisco enzyme) Step 2: six-carbon sugars split in half, and phosphates from NADPH and ATP are added to create glyceraldehyde-3-phosphate (G3P) - NADPH and ATP are recycled into their low-energy forms (NADP+ and ADP) to be re-used Step 3: one three-carbon G3P used to makes an organic molecule (like glucose) Step 4: remaining 5 G3P molecules are converted back to RuBP through the use of more energy from ATP - cycle "turns" three times (3 carbon dioxide molecules) to make one G3P

Steps of the Calvin Cycle

If the sun's rays are blocked, photosynthesis cannot be performed or at least performed as often because the plant gets no or little sunlight. So, it can't perform its tasks as it usually would without the required reactants.

When the sun's rays are blocked by a thick forest, clouds, dust from a volcanic eruption, or smoke from a large fire, what effect do you think this has on photosynthesis?

photosystem

a cluster of chlorophyll and other pigment molecules that harvest light energy for the light reactions of photosynthesis

chlorophyll

a green pigment that gives plants their green color, and that reacts with sunlight, carbon dioxide, and water to form carbohydrates

electron transport chain

a series of molecules through which electrons pass in a process that causes proteins to build up on one side of the membrane

electrons

a subatomic particle that has a negative charge

carbon fixation takes carbon from inorganic molecules and puts it into organic molecules

explain what is meant by the term carbon fixation.

thylakoid

flattened sacs inside of chloroplasts

NADPH

higher energy molecule over NADP+ that is made at the end of the electron transport chain of photosystem 1

light reactions

light energy is converted to chemical energy, which is temporarily stored in ATP and energy carrier NADPH

RuBisco

one of the only enzymes to change inorganic carbon to organic (Ribulose - 1,5 biphosphate carboxylase oxygenase

chloroplast

organelles found in the cells of plants and algae

autotroph

organisms that use energy from sunlight to make organic compounds

products of photosynthesis

oxygen and sugars (glucose)

Calvin Cycle

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

stroma

surrounds the grana (thylakoids connected and layered to form sacs) in the chloroplast

carbon cycle

the movement of carbon from the nonliving environment into living things and back

reactants of photosynthesis

water, light, and carbon dioxide

(C) carbon fixation

what is NOT part of the light reactions? (A) splitting of water (B) electron transport (C) carbon fixation (D) absorption of the light energy

a biochemical pathway is a sequence in which the product of one step is used in the next

what is the biochemical pathway?

on the thylakoid membrane

where do the light reactions take place?