Bio 101 Test 1: Chapter 8 (Photosynthesis)

Why are carbon sinks important for Americans to understand?

- 1/3 of the CO2 released from burning fossil fuels is "soaked up" by forests. - Tropical forests = 55% of the carbon stored in forests - Tropical forests are being cleared at alarming rates in Indonesia and Brazil and other places.

What kind of visible light do plants NOT absorb well? Why do plants have various pigments in the chloroplast?

- Green, because it is mostly transmitted and reflected—not absorbed—by photosynthetic pigments. - Multiple pigments absorb different wavelengths of light, allowing the plant to capture the maximum amount of energy from the sun. - Different pigments absorb light of different wavelengths, and chloroplasts contain more than one type of pigment. - Chlorophyll a, which participates directly in the light reactions, absorbs mainly blue-violet and red light. - A very similar molecule, chlorophyll b, absorbs mainly blue and orange light. Chlorophyll b broadens the range of light that a plant can use by conveying absorbed energy to chlorophyll a, which then puts the energy to work in the light reactions.

Describe what light does in a photosystem

- Light enters the chloroplast and is absorbed by the pigment molecules. - The transfer of energy within photosystem sends electrons to an excited state

Electrons in photosystem II would eventually be used up if not replaced. Water plays a role in replacing electrons. How? What part of the water molecule is used in the process and what part diffuses away?

- Water is split and its electrons are passed onto photosystem 2 - The hydrogen ions and electrons are used in the process and the oxygen that is produced is released out of the stomata of the cell

•How does photophosphorylation compare with oxidative phosphorylation?

-Mitochondria use oxidative phosphorylation to transfer chemical energy from FOOD into the chemical energy of ATP. -Chloroplasts use photophosphorylation to transfer LIGHT energy into the chemical energy of ATP.

Describe in words what happens in the light reaction of photosynthesis:

-The light reactions, which occur in the thylakoids, include the steps that convert light energy to chemical energy and release O2 - Water is split, providing a source of electrons and giving off O2 as a by-product. - Light energy is absorbed by chlorophyll molecules built into the thylakoid membranes. - This energy is used to drive the transfer of electrons and H+ from water to the electron acceptor NAD+, reducing it to NADPH. - NADPH is first cousin to NADH, which transports electrons in cellular respiration; the two differ only in the extra phosphate group in NADPH. - NADPH temporarily stores electrons and provides "reducing power" to the Calvin cycle. The light reactions also generate ATP from ADP and a phosphate group.

Calvin cycle: How many ATP total are needed to make one gluclose? How many NADPH are needed to convert total to make one glucose How can the chloroplast get more ATP and NADPH?

18,12,Cycle back through the light reactions

Photosynthesis equation what aspects are part of the calvin cycle? light?

6CO2 + 6H2O ------> C6H12O6 + 6O2 (BOLD = CALVIN)

What product of the light reaction has just been made as a result of the H+ gradient?

ATP

In the chloroplast, the name of the enzyme that performs cyclic phosphorylation process is called

ATP synthase

These H+ then flow through what protein as they follow their concentration gradient?

ATP synthase

What happens to the oceans as they absorb more and more CO2?

As C02 is dissolved in water, it becomes carbonic acid. Measurable decreases in ocean pH have raised concern among biologists

Just like in aerobic respiration the electrons lose small amounts of energy as they "bounce" from one electron carrier to the next. That released energy is used to do what cellular work?

As electrons pass down the electron transport chain, hydrogen ions are pumped from the stroma into the thylakoid space, against its concentration gradient, creating ATP.

What is the chemical formula for gluclose? So, how many carbons are in the molecule? Therefore, how many carbon dioxide molecules will be needed from the atmosphere?

C6H1206 6 6

List things that increase CO2 in the atmosphere.

Combustion of Fossil Fuels Cellular Respiration Combustion of wood Microbial Decomposition

A carbon sink is anything that absorbs more carbon than it releases. How are trees "carbon sinks"?

Hold onto carbon for as long as they are alive

Both cellular respiration and photosynthesis rely on electron transport chains embedded in membranes to produce ATP molecules. Describe the difference

In cellular respiration, the electron source originates in energy rich food; In photosynthesis the electron source is water (It is why we need to water plants to grow!)

What is the global consequence for the atmosphere if CO2 output by respiration exceeds its intake by photosynthesis and absorption into the ocean?

Increasing and rising concentrations of greenhouse gases leads to climate change

List things that remove CO2 from the atmosphere.

Photosynthesis Intake from oceans

The Calvin cycle takes place where in the chloroplast?

Stroma

Before looking at the details of electron transport and chemiosmosis of module 7.9, describe Figure 7.8—a mechanical analogy. What is the big picture relative to electrons?

The coupling of two photosystems and an electron transport chain can transform the energy of light to the chemical energy of ATP and NADPH

How is the Calvin cycle linked to the light reaction?

The products of light reactions are used as reactants in the Calvin cycle (along with C02)

Similar to mitochondria during aerobic respiration, a H+ gradient is generated across membranes (meaning there are more H+ on one side than the other). In the chloroplast, in what compartment do more H+ build up in?

Thylakoid space

Let's consider the last output: NADPH. After electrons bounce through the electron transfer chain following photosystem II, they have lost considerable energy. They get re-excited at photosystem I and get passed to another electron transfer chain. What is the terminal electron acceptor in this reaction? _NADP_+ What is it called once it is reduced? ___NADPH_. Is it useful to the cell? Why?

Yes, NADPH temporarily stores electrons and provides "reducing power" to the Calvin cycle.

Where does the mass of a tree come from?

carbon dioxide from the air

Taking carbon from the carbon dioxide in the air (called an inorganic molecule) and attaching the carbon to an organic molecule is called

cyclic phosphorylation

Electrons flow from ____ ultimately to ______, which is reduced to ___.

h20, NADP. NADPH

What are the inputs of the light reactions? What are the outputs of the light reactions?

light, water, ADP, NADP+ ATP, NADPH, O2

An electron is energized and transferred to a primary electron acceptor. This creates an electron "hole." From what is the missing electron replaced?

water

What causes carbon dioxide to be released into the atmosphere?

•Cellular respiration from producers, consumers, and decomposers. •Burning of wood and fossil fuels (combustion reactions)