BIO Chap 6 Questions

In what form do plants need nitrogen?

As nitrate (NO3-).

Why are carnivores, such as lions, dependent on photosynthesis to survive?

Because lions eat animals that eat plants.

Has rain and snowfall increased or decreased as the result of a warmer climate?

Both have actually increased, on average, when the entire world is taken into account. Some places, however, have become much drier due to climatic shifts.

In what way is a chloroplast structurally similar to a mitochondrion.

Both have inner and outer membranes with a space in between.

How are the light reactions similar to aerobic cellular respiration?

Both occur in a membrane and involve hydrogen ions being actively pumped through protein channels, electrons jumping from protein to protein in an electron transport chain, and ATP synthase making ATP by a passive process.

What are some things that you can do to reduce your carbon dioxide emissions?

Buy a more fuel efficient car, drive less, use energy efficient bulbs, and adopt the lifestyle that includes reusing things, recycling whenever you can, and producing less waste, including not using throw-away plastic bottles and bags. Anything that you can do to burn less fossil fuel and use less energy will not only help the climate change problem, but also many other environmental problems that have been around for decades, and are only getting worse.

When the cooler fall weather begins to occur, what happens to cause leaves to change their colors?

Cooler temperatures cause the green chlorophyll in leaves to break down. Thus, we can only see the orange, red, and yellow colors as the chlorophyll disappears.

What molecule leaves the Calvin cycle to be converted into glucose?

G3P.

Which color(s) of light does chlorophyll reflect?

Green is reflected, and given that plants have a lot of it, that is why plants are green. In the fall, chlorophyll breaks down in leaves, causing them to turn red, orange, and yellow as the other pigments, including the carotenoids, begin to dominate. Eventually, as the leaves start to freeze, the other pigments will be broken down as well, resulting in death for the leaves.

What is a heterotroph? Can heterotrophs do photosynthesis?

Heterotrophs cannot make their own food. They do not have chloroplasts or chlorophyll, so they cannot do photosynthesis. They get their energy by eating other organisms. Humans and other animals are examples of heterotrophs.

In what ways are the light reactions different than aerobic cellular respiration?

In the light reactions of photosynthesis water is consumed, whereas in aerobic cellular respiration water is produced. Aerobic cellular respiration consumes oxygen, whereas photosynthesis produces it, and photosynthesis consumes carbon dioxide, whereas aerobic cellular respiration produces it. In terms of energy carriers, plants use NADPH instead of NADH. NADPH phosphorus (P). ATP also serves as an energy carrier in plants.

What happens during carbon fixation?

Inorganic CO2 is converted to an organic compound. Three molecules of CO2 combine with RuBP, and RuBisCO catalyzes a reaction between CO2 and RuBP, which forms a six-carbon compound that is immediately converted into two three-carbon compounds called 3-PGA.

What is the energy of a photon first used to do in photosynthesis?

It energizes an electron. In photosystem II, a photon of light hits chlorophyll, causing an electron to be energized.

What is eutrophication? What causes it and what does it do to the oxygen supply where it occurs?

It involves the excessive growth of algae in aquatic habitats, mainly freshwater ones, such as lakes. Both nitrogen and phosphorus from fertilizers in runoff can lead to this problem. As algae blooms take over, oxygen is depleted from the environment, causing huge die offs of fish and other organisms.

On a hot, dry day, plants close their stomata to conserve water. What impact will this have on photosynthesis?

Levels of carbon dioxide (one of the reactants) will fall, and levels of oxygen (a product) will rise. As a result, the rate of photosynthesis will slow down.

Are most plants C3, C4, or CAM? What about a cactus? Corn?

Most plants are C3. A cactus uses CAM and corn is C4.

What two nutrients are most limiting to plants?

Nitrogen (N) and phosphorus (P). There is plenty of carbon dioxide in the air!

Is the greenhouse effect a human-caused phenomenon?

No. It has been around ever since the Earth formed and there were greenhouse gases, such as carbon dioxide and methane, in the air. Humans have added greenhouse emissions, however, which has made the greenhouse effect more dramatic, thus making the climate warmer.

Have Republicans always been completely skeptical of "global warming?"

No. When he was president, George W. Bush, along with Newt Gingrich and other high ranking Republicans were actually working collaboratively with many Democrats in congress to begin addressing the climate change problem. However, by 2012, members of both political parties were avoiding the issue altogether. Although nothing had changed in terms of the science, with the vast majority of the world's climate scientists still finding overwhelming evidence pointing at climate change, well-funded skeptics made it a political liability to even talk about the subject.

Which part of the Calvin cycle would be affected if a cell could not produce the enzyme RuBisCO?

None of the cycle could take place, because RuBisCO is essential in fixing carbon dioxide. Specifically, RuBisCO catalyzes the reaction between carbon dioxide and RuBP at the start of the cycle.

In what form is most phosphorus in nature?

Phosphate (PO43-).

How do we define a photoautotroph? What are three examples of this type of organism?

Photoautotrophs, including plants, algae, and some bacteria (e.g. cyanobacteria) can us the energy of the sun to make their own food by the process of photosynthesis.

What structure within the chloroplast contains the pigment chlorophyll? What is a stack of these structures called?

The thylakoid contains the chlorophyll. A stack of thylakoids is called a granum.

Which has more energy, a short wavelength or a long wavelength?

Shorter wavelengths have more energy. This is why UV rays and X-rays are dangerous to humans. They are short, high-energy waves.

What organisms can fix nitrogen and where are they found?

Some bacteria in the soil and bacteria living in root nodules of legumes (e.g. beans, peanuts, and pea plants) can do this.

In what ways have humans altered the carbon cycle, leading to higher amounts of carbon dioxide in the atmosphere?

The combustion of fossil fuels, including coal, oil, and gas, and burning of plant biomass (e.g. trees) has added large amounts of carbon dioxide to the atmosphere, while at the same time the loss of plants (e.g. through deforestation) has reduced the amount of photosynthesis that removes carbon dioxide from the atmosphere.

Describe the pathway of energy in light-dependent reactions.

The energy is present initially as light. A photon of light hits chlorophyll, causing an electron to be energized. The free electron travels through the electron transport chain, and the energy of the electron is used to pump hydrogen ions into the thylakoid space, transferring the energy into the electrochemical gradient. The energy of the electrochemical gradient is used to power ATP synthase, and the energy is transferred into a bond in the ATP molecule. In addition, energy from another photon can be used to create a high-energy bond in the molecule NADPH.

Plants produce oxygen when they photosynthesize. Where does the oxygen come from?

The splitting of water molecules.

Where in plant cells does the Calvin cycle take place?

The stroma of the chloroplast.

What is the ultimate source of energy for photosynthesis? What are the two products of photosynthesis?

The sun provides the energy source for all photoautotrophs. Photosynthesis produces glucose and oxygen.

In what way can the oceans help to reduce the effects of climate change.

They are a huge reservoir of both carbon dioxide and heat. This allows them to absorb some of the excess carbon and heat, but not enough to prevent climate change from occurring over the long term.

According to NASA, how much has the world warmed, on average, over the last 100 years or so?

They found that it had warmed 0.5 degrees Celsius, or 1 degree Fahrenheit, by the beginning of the 21st century. Some places, such as the poles and southwestern U.S., have warmed by much more.

What is the overall purpose of the light reactions in photosynthesis?

To convert solar energy into chemical energy that cells can use to do work. Energy carriers are created to be used in the Calvin cycle, where glucose is actually made.

What are the most common greenhouse gas emissions that humans are adding to the atmosphere? Which is the most abundant emission and where does it mostly come from?

We are adding carbon dioxide (the most abundant; mainly from fossil fuel use), methane, nitrous oxide, and chlorofluorocarbons to the atmosphere through various activities.