Biology Chap 5 & 6

The equation CH4 + 2 O2 → CO2 + 2 H2O represents _____.

a chemical reaction

What is the first stable organic molecule formed by the C4 cycle?

a four-carbon compound

Allosteric regulators bind to _____.

a site on the enzyme other than the active site

The speed of a reaction is determined by its _____.

activation energy

High temperatures inactivate enzymes by _____.

altering the enzyme's three-dimensional shape

To drive an endergonic reaction, _____.

an exergonic reaction must be coupled to it

Competitive inhibitors of enzymes work by _____.

blocking an enzyme's active site

The electrons lost from the reaction center of photosystem I are replaced by electrons from the _____.

bottom of the electron transport chain associated with photosystem II

Where does the Calvin-Benson cycle occur in C4 plants?

bundle-sheath cells

What plants reduces photorespiration by employing an alternative pathway known as crassulacean acid metabolism?

cacti

What are some examples of CAM plants?

cacti other desert spp (fleshy leaves)

Photosynthetic organisms obtain their carbon from _____

carbon dioxide

the initial steps in the cycle, in which carbon dioxide reacts with ribulose bisphosphate to form a stable organic molecule.

carbon fixation

a red, orange, or yellow pigment, found in chloroplasts, that serves as an accessory light-gathering molecule in thylakoid photosystems.

carotenoids

a process of ATP generation in chloroplasts and mitochondria. The movement of electrons down an electron transport system is used to pump hydrogen ions across a membrane, thereby building up a concentration gradient of hydrogen ions across the membrane; the hydrogen ions diffuse back across the membrane through the pores of ATP-synthesizing enzymes; the energy of their movement down their concentration gradient drives ATP synthesis.

chemiosmosis

a pigment found in chloroplasts that captures light energy during photosynthesis; absorbs violet, blue, and red light but reflects green light.

chlorophyll

In most green plants, chloroplasts are _____.

concentrated in the mesophyll of the leaf

Active transport of sodium into the cell is an example of what type of reaction?

coupled

The reaction ADP + P → ATP is endergonic, whereas the reaction ATP → ADP + P is exergonic. The two reactions are therefore said to be _____.

coupled

During the process of cellular respiration, glucose is broken down to release energy for cellular activities. The breakdown of glucose is _____.

exergonic

In organisms, the energy released by _____ reactions is used to drive _____ reactions

exergonic ... endergonic

Under hot, dry conditions, C4 plants are able to fix substantially more CO2 than C3 plants. This is because C4 plants _____.

fix the carbon in carbon dioxide to phosphoenolpyruvate (PEP) rather than ribulose bisphosphate (RuBP)

What are products of the light-independent reactions?

glucose, ADP, and NADP+

What are some examples of C4 plants?

grasses sugar cane maize (corn) sorghum

What color of light would be the least effective in stimulating photosynthesis in a green plant?

green

an adjustable opening in the epidermis of a leaf, surrounded by a pair of guard cells, that regulates the diffusion of carbon dioxide and water into and out of the leaf.

stomata

In plants, the light-independent reactions of photosynthesis take place in the _____.

stroma

the semi-fluid material inside chloroplasts in which the grana are embedded.

stroma

Which portion of the electromagnetic spectrum is used for photosynthesis?

visible light

Carotenoids are accessory pigments that reflect _____.

yellow and orange light

the cyclic series of reactions whereby carbon dioxide is fixed into carbohydrates during the light-independent reactions of photosynthesis

C3 cycle (Calvin-Benson cycle)

the series of reactions in certain plants that fixes carbon dioxide into oxaloacetic acid, which is later broken down for use in the cycle of photosynthesis.

C4 cycle

A substance that speeds up a chemical reaction without itself being permanently changed in the process; lowers the activation energy of a reaction.

Catalyst

A molecule that stores energy in "high-energy" chemical bonds and releases the energy to drive coupled endothermic reactions. In cells, ATP is the most common energy-carrier molecule.

Energy-carrier Molecule

A measure of the amount of randomness and disorder in a system.

Entropy

A protein catalyst that speeds up the rate of specific biological reactions.

Enzyme

What speeds up chemical reactions by lowering the activation energy?

Enzymes

The enzyme lactase catalyzes the conversion of lactose (a disaccharide) to glucose and galactose. Sucrose is also a disaccharide, but lactose cannot catalyze its breakdown. Why not?

Lactose fits into the active site of lactase; sucrose does not

The physical laws that define the basic properties and behavior of energy.

Laws of Thermodynamics

A sequence of chemical reactions within a cell, in which the produced of one reaction are the reactants for the next reaction.

Metabolic Pathway

The sum of all chemical reactions that occur within a single cell or within all cells of a multicellular organism.

Metabolism

What transports electrons from place to place within cells.

NAD+ and FAD

Some of the energy released as electrons flow down the electron transport chain after being ejected from photosystem I is used to synthesize _____.

NADPH

What is the first stable organic molecule formed by the C3 cycle?

PGA, a three-carbon compound

"Stored" energy, normally chemical energy or energy of position within a gravitation field.

Potential Energy

An atom or molecule that is formed from reactants in a chemical reaction.

Product

An atom or molecule that is used up in a chemical reaction to form a product.

Reactant

Photorespiration occurs because _____.

RuBP combines with O2 instead of CO2

The principle of physics that states that any change in an isolated system causes the quantity of concentrated, useful energy to decrease the amount of randomness and disorder (entropy) to increase.

Second Law of Thermodynamics

What allows oxygen to exit the leaf?

Stomata

The atoms ore molecules that are the reactants for an enzyme-catalyzed chemical reaction.

Substrate

How many molecules of CO2 must be fixed in the C3 cycle to produce one molecule of glucose?

6

The summary equation for photosynthesis is _____.

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

Some of the energy released as electrons flow down the electron transport chain toward photosystem I is used to generate _____.

ATP

All of the following compounds are required for the Calvin-Benson cycle to proceed: _____.

ATP, NADPH, RuBP, CO2

In a chemical reaction, the energy needed to force the electron shells of reactants together, prior to the formation of products.

Activation Energy

The region of an enzyme molecule that binds substrates and performs the catalytic function of the enzyme.

Active Site

A molecule composed of the sugar ribose, the base adenine, and two phosphate groups; a component of ATP.

Adenosine Diphosphate (ADP)

A molecule composed of the sugar ribose, the base adenine, and three phosphate groups.

Adenosine Triphosphate (ATP)

The process by which enzyme action is enhanced or inhibited by small organic molecules that act as regulators by binding to the enzyme and altering its active site.

Allosteric Regulation

The process that forms and breaks chemical bonds that hold atoms together.

Chemical Reaction

An organic molecule that is bound to certain enzymes and is required for the enzymes' proper functioning; typically, a nucleotide bound to a water-soluble vitamin.

Coenzyme

The process by which two ore more molecules that are somewhat similar in structure compete for the active site of an enzyme.

Competitive Inhibition

A pair of reactions, one exergonic and one endergonic, that are linked together such that the energy produced by the exergonic reaction provides the energy needed to drive the endergonic reaction.

Coupled Reaction

A molecule that can reversibly gain or lose electrons. Electrons carriers generally accept high-energy electrongs produced during a exergonic reaction and donate the electrons to acceptor molecules that use the energy to drive endergonic reactions.

Electron Carrier

Pertaining to a chemical reaction that requires an input of energy.

Endergonic

The capacity to do work.

Energy

Pertaining to a chemical reaction that liberates energy (either as heat or in the form of increased entropy); a "downhill" reaction.

Exergonic

T or F - Enzymes emerge changed from the reactions they catalyze.

False

In enzyme-mediated chemical reactions, the condition in which the product of a reaction inhibits one or more of the enzymes involved in synthesizing the product.

Feedback Inhibition

The principle of physics that states that within any isolated system, energy can be neither created nor destroyed but can be converted from one form to another.

First Law of Thermodynamics

What is the correct pathway for the flow of electrons in photosynthesis?

H2O → photosystem II → photosystem I → NADPH

The energy of movement; includes light, heat, mechanical movement, and electricity.

Kinetic Energy

If all matter tends toward increasing randomness and disorder, how can life exist?

There is a constant input of energy from the sun.

T or F - Activation energy is required for endergonic and exergonic reactions.

True

T or F - Energy is released when ATP gives up a phosphate.

True

T or F - In exergonic reactions the reactants contain more energy than the products

True

Enzymes are said to be "highly specific." This means that _____.

each enzyme catalyzes at most a few different reactions

a series of electron carrier molecules, found in the thylakoid membranes of chloroplasts and the inner membrane of mitochondria, that extract energy from electrons and generate ATP or other energetic molecules.

electron transport chain (ETC)

During the process of photosynthesis, energy from sunlight is used to synthesize glucose. The formation of glucose is _____.

endergonic

Energy from exergonic reactions is transferred from place to place in cells via _____.

energy-carrier molecules

In any system, the total energy includes usable and unusable energy. The unusable energy is a measure of disorder in the system and is referred to as _____.

entropy

Metabolic pathways are regulated by _____.

enzymes

The first law of thermodynamics is also known as the _____.

law of conservation of energy

the first stage of photosynthesis, in which the energy of light is captured as ATP and NADPH; occurs in thylakoids of chloroplasts.

light-dependent reactions

the second stage of photosynthesis, in which the energy obtained by the light-dependent reactions is used to fix carbon dioxide into carbohydrates; occurs in the stroma of chloroplasts.

light-independent reactions

In C4 plants, carbon fixation initially occurs in the chloroplasts of _____.

mesophyll cells

the smallest unit of light energy

photon

In most plants, closure of stomata results in _____.

photorespiration

a series of reactions in plants in which replaces during the cycle, preventing carbon fixation; this wasteful process dominates when plants are forced to close their stomata to prevent water loss.

photorespiration

the complete series of chemical reactions in which the energy of light is used to synthesize high-energy organic molecules, normally carbohydrates, from low-energy inorganic molecules, normally carbon dioxide and water.

photosynthesis

in thylakoid membranes, a light-harvesting complex and its associated electron transport system.

photosystems

Light energy is initially captured by "photosystems" within thylakoid membranes. Photosystems are organized arrays of _____.

proteins, chlorophylls, and accessory pigments

Substances that enter into a chemical reaction are called _____, and substances formed as a result of the reaction are known as _____.

reactants products

in the light-harvesting complex of a photosystem, the chlorophyll molecule to which light energy is transferred by the antenna molecules (light-absorbing pigments); the captured energy ejects an electron from the reaction center chlorophyll, and the electron is transferred to the electron transport system.

reaction center

Which wavelengths of light would be the most effective in stimulating photosynthesis in a green plant?

red & blue

When your cells break down glucose, the amount of usable energy (ATP) produced is much smaller than the total amount of energy in a glucose molecule. The "missing" energy was _____.

released as heat energy

CAM plants differ from C4 plants in that _____.

they fix carbon at night

a disk-shaped, membranous sac found in chloroplasts, the membranes of which contain the photosystems and ATP-synthesizing enzymes used in the light-dependent reactions of photosynthesis.

thylakoid

ATP is important in cells because it _____.

transfers energy from exergonic reactions to endergonic reactions