Ch 10 Photosynthesis

Why does chlorophyll look green to the human eye?

Chlorophyll reflects green light. Chlorophyll absorbs blue and red light and reflects green light. The reflected light is what becomes visible to the eye.

____________ are specialized organelles that act as the site for photosynthesis. Different chemical reactions occur in different parts of the ____________.

Chloroplasts

Photosynthesis in the leaves of plants involves many steps, but it can be divided into two stages: the _____-_________ _________ and the ______ _____.

light-dependent reactions; Calvin cycle

Plants are the most common autotrophs in terrestrial—land—ecosystems. All green plant tissues can photosynthesize, but in most plants, but the majority of photosynthesis usually takes place in the leaves. The cells in a middle layer of leaf tissue called the _________ are the primary site of photosynthesis.

mesophyll

Photosynthetic organisms, including plants, algae, and some bacteria, play a key ecological role. They introduce chemical energy and fixed carbon into ecosystems by using light to synthesize sugars. Since these organisms produce their own food—that is, fix their own carbon—using light energy, they are called _______________(literally, self-feeders that use light).

photoautotrophs

Small pores called _______ —singular, stoma—are found on the surface of leaves in most plants, and they let carbon dioxide diffuse into the mesophyll layer and oxygen diffuse out.

stomata

Photosynthesis

the process in which light energy is converted to chemical energy in the form of sugars.

The light-dependent reactions take place in the _________ membrane and require a continuous supply of light energy, which is taken from the sun. The Calvin cycle takes place in the ______ and does not directly require light.

thylakoid; stroma

During the light-dependent reactions, the energy from sunlight is absorbed by chlorophyll and converted into chemical energy, synthesizing ___ and _____.

ATP ; NADPH

The light-dependent reactions of photosynthesis take energy from sunlight and convert it into stored chemical energy. Which compounds are produced in the light-dependent reactions?

ATP and NADPH During the light-dependent reactions, the energy from sunlight is absorbed by chlorophyll and converted into chemical energy, synthesizing ATP and NADPH.

Photosynthesis can be divided into two steps: the light-dependent reactions and the Calvin cycle. Describe the overall process of the Calvin cycle.

ATP and NADPH produced by the light reactions are used by the Calvin cycle to make carbohydrates. In the first step of photosynthesis, ATP and NADPH are produced using the light-dependent reactions. The ATP is used to provide energy to the Calvin cycle, where carbon is reduced to make carbohydrates.

The thylakoid membrane becomes damaged, causing the inside of the thylakoid to mix with the stroma. What process is likely to be most affected by this damage?

ATP synthesis The leaking membrane would cause the diffusion of protons into stroma, destroying the proton gradient. Because ATP synthesis relies on the proton gradient, the damage prevents ATP from being produced.

The ______ _____, also called the _____-___________ _________ takes place in the stroma and does not directly require light. Instead, the Calvin cycle uses ATP and NADPH from the light-dependent reactions to fix carbon dioxide and produce three-carbon sugars—glyceraldehyde-3-phosphate, or G3P, molecules—which join up to form glucose.

Calvin cycle; light-independent reactions

What reaction occurs during the Calvin cycle?

Carbon fixation Carbon dioxide is fixed and reduced in order to form G3P. Carbon reduction Carbon dioxide is fixed and reduced in order to form G3P. RuBP regeneration Some G3P molecules that are produced go on to make glucose, and others must be recycled to regenerate the RuBP acceptor for the Calvin cycle to continue.

A mutation occurs in the chloroplasts of a lettuce plant, causing its thylakoid membranes to become more permeable to charged ions. How might this mutation affect the Calvin cycle?

Fewer carbohydrates would be produced by the Calvin cycle. Less carbon fixation would occur in the treated chloroplasts because less ATP would be created due to the weaker proton gradient across the thylakoid membrane.

What happens to oxygen produced by the light-dependent reactions?

It is released into the atmosphere. The light-dependent reactions produce oxygen, which diffuses out of the plant as a waste product and is released into the atmosphere.

A scientist suspects that a particular plant contains chloroplasts that lack photosystem II (PSII), even though it is able to live. How could the scientist determine if PSII is missing from the plant's chloroplasts?

Test for the presence of oxygen in light Oxygen is released in PSII, so if PSII is missing from the chloroplasts, no oxygen will be found.

The Calvin cycle is considered light-independent because it can occur in darkness. However, most often the Calvin cycle takes place in sunlight. Why?

The Calvin cycle requires ATP and NADPH, which require sunlight to be produced. The Calvin cycle can occur without sunlight if ATP and NADPH are available. However, more often than not, these energy sources are available only when light is available and the light-dependent reactions can occur to produce them.

Carbon from carbon dioxide—inorganic carbon—can be incorporated into organic molecules; this process is called ______ ________, and the carbon in organic molecules is also known as _____ ______. The carbon that's fixed and incorporated into sugars during photosynthesis can be used to build other types of organic molecules needed by cells.

carbon fixation; fixed carbon

The glucose molecules serve as fuel for cells: their chemical energy can be harvested through processes like ________ ___________ and ____________, which generate adenosine triphosphate—ATP, a small, energy-carrying molecule—for the cell's immediate energy needs.

cellular respiration; fermentation

Each mesophyll cell contains organelles called ____________, which are specialized to carry out the reactions of photosynthesis. Within each chloroplast, disc-like structures called __________ are arranged in piles like stacks of pancakes that are known as _____ —singular, granum. The membrane of each thylakoid contains green-colored pigments called ____________ that absorb light. The fluid-filled space around the grana is called the ______, and the space inside the thylakoid discs is known as the _________ _____. Different chemical reactions occur in the different parts of the chloroplast.

chloroplasts; thylakoids; grana; chlorophylls; stroma; thylakoid space

Humans, and other organisms that can't convert carbon dioxide to organic compounds themselves, are called ___________, meaning different-feeders. Heterotrophs must get fixed carbon by eating other organisms or their by-products. Animals, fungi, and many prokaryotes and protists are heterotrophs.

heterotrophs

The _____-_________ _________ take place in the thylakoid membrane and require a continuous supply of light energy. Chlorophylls absorb this light energy, which is converted into chemical energy through the formation of two compounds, ATP—an energy storage molecule—and NADPH—a reduced (electron-bearing) electron carrier. In this process, water molecules are also converted to oxygen gas—the oxygen we breathe!

light-dependent reactions