Chapter 10

Front 1

Autotroph

Back 1

Any organism that can synthesize reduced organic compounds from simple inorganic sources such as CO2 or CH4. Most plants and some bacteria and archaea are autotrophs. Also called a primary producer.

Front 2

Heterotroph

Back 2

Any organism that cannot synthesize reduced organic compounds from inorganic sources and that must obtain them by eating other organisms. Some bacteria, some archaea, and virtually all fungi and animals are heterotrophs. Also called a consumer.

Front 3

Calvin Cycle

Back 3

In photosynthesis, the set of light independent reactions that use NADPH and ATP formed in the light-dependent reactions to drive the fixation of atmospheric CO2 and the reduction of the fixed carbon, ultimately producing sugars. Requires the products of the light capturing reactions.

Front 4

NADP+/NADPH

Back 4

Oxidized and reduced forms, respectively, of nicotinamide adenine dinucleotide phosphate. A nonprotein electron carrier that is reduced during the light-dependent reactions in photosynthesis and extensively used in biosynthetic reactions.

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Pigment

Back 5

Any molecule that absorbs certain wave lengths of visible light and reflects or transmits other wavelengths. We see the wavelengths that they do not absorb.

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Wavelength

Back 6

The distance between two successive crests in any regular wave, such as light waves, sound waves, or waves in water. Determines the type of electromagnetic radiation.

Front 7

Electromagnetic Spectrum

Back 7

The entire range of wavelengths of radiation extending from short wavelengths (high energy) to long wavelengths (low energy). Includes gamma rays, Xrays, ultraviolet, visible light, infrared, microwaves, and radio waves (from short to long).

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Visible Light

Back 8

The range of wavelengths of electromagnetic radiation that humans can see, from about 400 to 700 nanometres.

Front 9

Absorption Spectrum

Back 9

The amount of light of different wavelengths absorbed by a pigment. Usually depicted as a graph of light absorbed versus wavelength.

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Chlorophyll

Back 10

Any of several closely related green pigments, found in chloroplasts and photosynthetic protists, that absorb light during photosynthesis.

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Carotenoid

Back 11

Any of a class of accessory pigments, found in chloroplasts, that absorb wavelengths of light not absorbed by chlorophyll; typically appear yellow, orange, or red. Includes carotenes and xanthophylls. Extend photosynthesis, stabilize unpaired electrons to protect cholorphyll molecules.

Front 12

Action Spectrum

Back 12

The relative effectiveness of different wavelengths of light in driving a light dependent process such as photosynthesis. Graph of some measure of the process versus wavelength. Blue and red photons are the most effective at driving photosynthesis, because they have high oxygen levels. Therefore, chlorophylls are the main photosynthetic pigments.

Front 13

Flavonoid

Back 13

An accessory pigment that protects plants from high energy radiation. Found in vacuoles of leaf cells. Act as sunscreen for leaves and stems.

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Fluoresence

Back 14

The spontaneous emission of light from an excited electron falling back to its normal (ground) state.

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Photosystem

Back 15

One of two types of units, consisting of a central reaction centre surrounded by antenna complexes, that is responsible for the lightdependent reactions of photosynthesis.

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Antenna Complex

Back 16

Part of a photosystem, containing an array of chlorophyll molecules and accessory pigments, that receives energy from light and directs the energy to a central reaction centre during photosynthesis.

Front 17

Reaction Centre

Back 17

Centrally located component of a photosystem containing proteins and a pair of specialized chlorohyll molecules. Is surrounded by antenna complexes and receives excited electrons from them.

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Photosystem II

Back 18

A photosystem that contains a pair of P680 chlorophyll molecules and uses absorbed light energy to split water into protons and oxygen and to produce ATP.

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Photosystem I

Back 19

A photosytem that contains a pair of P700 chlorophyll molecules and uses absorbed light energy to produce NADPH.

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Pheophytin

Back 20

In photosystem II, a molecule that accpets excited electrons from a reaction centre chlorophyll and passes them to an electron transport chain.

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Plastoquinone (PQ)

Back 21

A nonprotein electron carrier in the chloroplast electron transport chain. Receives excited electrons from pheophytin and passes them to more electronegative molecules in the chain. Also carries protons to the lumen side of the thylakoid membrane, generating a proton-motive force.

Front 22

Photophosporylation

Back 22

Production of ATP molecules using the energy released as light-excited electrons flow through an electron transport chain during photosynthesis. Involves generation of a proton-motive force during electron transport and its use to drive ATP synthesis. Depends on chemiosmosis.

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Oxygenic

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Referring to any process or reaction that produces oxygen. Photosynthesis in plants, algae, and cyanobacteria, which involves photosystem II, is oxygenic.

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Anoxygenic

Back 24

Referring to any process or reaction that does not produce oxygen. Photosynthesis in purple sulphur and purple nonsulphur bacteria, which does not involve photosystem II, is anoxygenic.

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Ferredoxin

Back 25

In photosynthetic organisms, an iron and sulphur-containing protein in the electron transport chain of photosystem I. Can transfer electrons to the enzyme NADP+ reductase, which catalyzes formation of NADPH.

Front 26

Z-scheme

Back 26

Noncyclic electron flow. Path of electron flow in which electrons pass from photosystem II and photosystem I and ultimately to NADP+ during the light-dependent reactions of photosynthesis.

Front 27

Plastocyanin

Back 27

A small protein that shuttles electrons from photosystem II to photosystem I during photosynthesis.

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Cyclic Photophosphorylation

Back 28

Path of electron flow during the light-dependent reactions of photosynthesis in which photosystem I transfers excited electrons back to the electron transport chain of photosystem II, rather than to NADP+. Also called cyclic electron flow.

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Carbon Fixation

Back 29

Calvin Cycle

Front 30

Ribulose Bisphosphate (RuBP)

Back 30

A five-carbon compound that combines with CO2 in the first step of the Calvin cycle during photosynthesis.

Front 31

The Calvin Cycle

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1. Fixation phase

2. Reduction phase

3. Regeneration phase

These steps occur in a cycle. Takes place in the stroma of chloroplasts.

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Fixation Phase

Back 32

Calvin cycle begins when CO2 reacts with RuBP. Fixes carbon and produces two molecules of 3-phosphoglycerate.

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Reduction Phase

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3-phosphoglycerate is phosphorylated by ATP and then reduced by electrons from NADPH. The product is G3P, one of which is used to manufacture glucose and fructose.

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Regeneration Phase

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The remaining G3P keeps the cycle going by serving as a substrate for the third phase. Regenerates RuBP.

Front 35

glyceraldehyde-3-phosphate (G3P)

Back 35

The phosphorylated three carbon compound formed as the result of carbon fixation in the first phase of the Calvin cycle.

Front 36

Rubisco

Back 36

The enzyme that catalyzes the first step of the Calvin cycle during photosynthesis.

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Maladaptive

Back 37

A trait that lowers fitness.

Front 38

Photorespiration

Back 38

A series of light driven chemical reactions that consumes oxygen and releases carbon dioxide, basically reversing photosynthesis. Occurs when there are high O2 and low CO2 concentrations inside plant cells, often in bright, hot, dry environments when stomata must be kept closed. Happens in the chloroplasts.

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Guard Cell

Back 39

One of two specialized, crescent shaped cells forming the border of the plant stoma. Can change shape to open or close the stoma.

Front 40

Stoma

Back 40

A microscopic pore on the surface of a leaf or stem through which gas exchange occurs.

Front 41

C3 Photosynthesis

Back 41

The most common form of photosynthesis, in which atmospheric CO2 is used to form 3-phosphoglycerate, a three-carbon sugar.

Front 42

C4 Photosynthesis

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A variant type of photosynthesis in which atmospheric CO2 is first fixed into four-carbon sugars. Enhances photosynthetic efficiency in hot, dry environments by reducing loss of oxygen due to photorespiration.

Front 43

PEP Carboxylase

Back 43

An enzyme that catalyzes the addition of CO2 to phosphoenol pyruvate, a three carbon compound, forming a four carbon organic acid. Found in the mesophyll cells of plants that perform C4 photosynthesis.

Front 44

Mesophyll Cell

Back 44

A type of cell, found near the surfaces of plant leaves, that is specialized for the light-dependent reactions of photosynthesis.

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Bundle-sheath Cell

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A type of cell found around the vascular tissue of plant leaves.

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Vascular Tissue

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In plants, tissue that transports water, nutrients, and sugars. Made up of the complex tissues xylem and phloem.

Front 47

Crassulacean Acid Metabolism (CAM)

Back 47

A variant type of photosynthesis in which CO2 is stored in organic acids at night when stomata are open and then released to feed the Calvin cycle during the day when stomata are closed. Helps reduce water loss and oxygen loss by photorespiration in hot, dry environments because water evaporates from the stomata if it is open during the day.

Front 48

Sucrose

Back 48

A disaccharide formed from glucose and fructose. One of the two main products of photosynthesis, along with starch.