chpt 3

Stored energy is described as potential energy

True

The energy of motion is known as__________ energy.

Kinetic

The sodium level inside and outside of a resting cell is an example of the

potential energy of a concentration gradient, because sodium is more abundant outside the cell.

The energy stored in a molecule's chemical bonds is a form of kinetic energy

False

As a runner sprints down a track, her movement is an example of

mechanical energy

______________ is a monomer that is stored as the polymer glycogen within the liver and muscle

Glucose

Compare and contrast chemical energy and radiant energy. Into which board category of energy (kinetic or potential) does each fit? What are two examples of each type of energy that relate to human physiology?

Chemical energy is potential energy and radiant energy is kinetic energy. Two examples of chemical energy are triglycerides and complex carbohydrates such as glycogen. Two examples of radiant energy are UV light (a DNA mutagen) and visible light (sensed by the visual system)

Three molecules that are important energy storage locations in the body are

ATP, glycogen, and triglyceride.

The propagation of an impulse along the axon of a neuron is considered electrical energy, a form of kinetic energy

True

The form of kinetic energy that refers to the movement of electromagnetic waves is _________ energy.

Radiant

Which is a form of energy that is generally unavailable to do any work?

Heat

The first law of thermodynamics states that once energy is consumed, it can no longer be converted to any other form of energy

False

According to the second law of thermodynamics, when energy is transformed from one kind to another.

some of it is converted to heat.

When we shiver on a cold day, the heat produced by muscle tissue is a demonstration of

second law of thermodynamics

When a car burns gasoline, the majority of the gasoline's chemical energy is transformed to sound and heat

True

When our inner ears convert sound energy into neural impulses or our retinas convert light into neural impulses

the conversion is consistent with both laws of thermodynamics.

Typically, synthesis reactions are endergonic

True

Chemical reactions that release energy are called ______________ reactions

exergonic

The reaction in which water and carbon dioxide combine to form carbonic acid is

reversible, and can proceed in either direction depending on the concentrations of the molecules.

The building of complex molecules from simpler ones is described as

anabolism

When the body's digestive system breaks down starch, a complex carbohydrate, into simpler carbohydrates, the reaction is

Catabolic and exergonic

Which one of the following choices includes 3 descriptions that are consistent with each other (that is, that describe the same type of chemical reaction)?

Anabolic, dehydration, endergonic

The exchange of a phosphate group between creative phosphate and adenosine diphosphate is categorized as a catabolic (rather than anabolic) reaction

False

The term metabolism refers to

all chemical reactions in the body

When NAD+ becomes NADH, it is being

reduced and gaining chemical energy

In a chemical reaction where an electron is exchanged from one reactant to another, the structure that loses an electron is

oxidized

In a redox reaction, when one reactant is oxidized, the other

is reduced

Generally, a cell stores ATP to meet the energy requirements of a few

Seconds

ATP formation

is endergonic and requires the presence of fuel molecules such as glucose.

In a lab setting, heating a vessel full of reactants will generally

increase the kinetic energy of the molecules and increase the reaction rate

In order for a reaction to occur, energy is needed to break the bonds that already exist in the reactant molecules; that energy is called the ____________ energy.

Activation

Explain the relationship between activation energy and reaction rate. For example, how would an increase in activation energy affect reaction rate? How do biological systems differ from lab settings when considering these chemical variables?

Higher activation energy requirements would be associated with slower reaction rates. Biological systems generally rely on protein enzymes to serve as catalysts that lower activation energy, whereas lab settings can employ high temperatures to increase the kinetic energy of the reactants to overcome the required energy input

The term activation energy refers to the amount of energy

required to initiate any chemical reaction.

A reaction with a very high activation energy should have a very high reaction rate

False

The presence of an enzyme within a chemical system

decreases activation energy

Enzymes are biological catalysts that are crucial for normal human metabolism

True

Exergonic reactions do not require activation energy

False

In the absence of the enzyme carbonic anhydrase, the combination of water and carbon dioxide to form carbonic acid does not occur

False

Structurally, enzymes are generally

globular proteins

The region of an enzyme into which the substrate fits is a

highly specific active site

The enzyme-substrate complex is

the chemical structure formed when the substrate binds to the active site.

Pancreatic amylase serves its function when it is located in the

small intestine

Lactose intolerance is caused by the lack of enzyme lactase, which is normally found in the

membranes of cells in the small intestine.

The enzyme DNA polymerase is synthesized

at a ribosome, and it remains within the cell.

Which answer lists the steps of enzyme action in correct order

Formation of enzyme-substrate complex, induced fit, formation or breakage of chemical bonds, release of product

When an enzymes conformational change results in the enzyme Hugging the substrate in its active site, the action is referred to as the _________ model of enzyme function

induced fit

When an enzyme catalyzing a catabolic reaction changes conformation to an induced fit with the substrate

it stresses chemical bonds in the substrate, making it easier to break them.

In the final step of enzymatic catalysis

the products are released and the enzyme is free to bind other substrates.

Cofactors are generally proteins

False

In performing its enzymatic function, carbonic anhydrase

requires the inorganic coenzyme zinc.

Which enzyme class splits a chemical bond in the absence of water

lyase

Which enzyme class transfers electrons from one substance to another

oxidoreductase

An enzyme that is described as a protein kinase is an

Transferase that transfers a phosphate group to a protein substrate

Lactase in an enzyme that digests lactose

True

Briefly describe how enzyme are named. What is generally used for the root of the name, and what is generally used as the suffix? Provide one example

The root is usually the substrate (or product) and the suffix is generally "-ase". An example is lactase, which digests lactose

An isomerase bonds two similar molecules together to form a larger one

False

Both pepsin and trypsin are proteins that digest proteins

True

Which statement accurately describes the effects the substrate and enzyme concentrations on reaction rate

An increase in either substrate or enzyme concentration will increase the reaction rate.

Saturation occurs when

all enzymes are busy and further increases in substrate concentration will not increase reaction rate.

Generally, a decrease in substrate concentration leads to an increase in reaction rate

False

Enzyme saturation occurs when substrate levels are so high that all enzyme molecules are actively engaged in the chemical reaction, and so further increases in substrate concentration do not increase reaction rate

True

At temperatures above 40C in the human body

Enzymes denature and reaction rates decrease

A fever of 101F causes most enzymes in the human body

To be more flexible and efficient

Extremely high temperatures break intramolecular interactions and _____________ an enzyme, resulting in a loss of its functions

Denature

Cold temperatures denature proteins, which is why biochemistry labs never freeze enzymes

False

The optimal pH range for most human enzymes is

6-8

The optimal pH range for the stomach enzyme pepsin is

2-4

The less acidic (more basic) the environment is, the more efficient an enzyme will be

False

A large decrease in pH results in increased H+ binding to an enzyme, which can disrupt electrostatic interactions within the molecule

True

A substance that binds to the active site of an enzyme and turns it off is called an ___________ inhibitior

Competitive

Noncompetitive inhibition of an enzyme occurs when the inhibitor binds to the

allosteric site, and its effectiveness is not influenced by substrate concentration.

Allosteric inhibitors are also called noncompetitive inhibitors

True

When multiple enzymes are organized in a metabolic pathway, each enzyme catalyzes one reaction and then releases the product

True

A group of enzymes that are physically attached to one another is referred to as an

Multienzyme complex

Which enzyme system allows the regulation at a single site and also diminishes the chance that a needed substrate will diffuse away from a catalyst

Multienzyme complex

To prevent depletion of a substrate, the product of a metabolic pathway will

turn off an enzyme early in the pathway.

In the regulation of enzymes, negative feedback ensures that a lot of product can be made from only a little bit of substrate

False

Enzymes that remove phosphate groups from their substrates are called

phosphatases or phosphatase

Enzyme regulation by negative feedback involves

allosteric inhibition of an enzyme by a product of its metabolic pathway.

A protein kinase is an enzyme that adds a phosphate to its substrate

True

Phosphorylation is carried out by a

kinase, and it may activate some enzymes and inhibit others.

Imagine that you discovered an enzyme in the human stomach that turned the substrate ABC into the product XYZ. Name this enzyme (using the standard convention) and describe its chemical characteristics. Under what conditions would it be an effective catalyst? How might its activity be regulated?

The enzyme ABC case would work best at or near human body temperature and at the acidic pH of the stomach. The enzyme is a globular protein that acts as a catalyst. It's activity might be regulated in a variety of fashions described in section 3.3 of the book.

When one glucose molecule is fully oxidized, how many molecules of CO2 result

6

During cellular respiration, when glucose is fully disassembled to carbon dioxide and water, the other reactant (with glucose) in the chemical equation is _____________

Oxygen

Glucose oxidation is exergonic

True

In substrate-level phosphorylation, energy is first released to coenzymes and then transferred to form ATP

FALSE

The indirect method of ATP production involves coenzymes such as FAD and is referred to as ____________ phosphorylation

Oxidative

The more common way that ATP is produced in cells is

the indirect pathway known as oxidative phosphorylation.

Which of the following choices lists the order of stages of cellular respiration in proper order

Glycolysis, intermediate stage, citric acid cycle, and the electron transport system

The first stage of cellular respiration is

glycolysis, and it occurs in the cytosol.

Glycolysis requires oxygen

False

The intermediate stage of cellular respiration

produces carbon dioxide and occurs in the mitochondria.

Hexokinase is an enzyme involved in cellular respiration and its substrate is glucose. Considering this information, hexokinase must be located

cytosol of cells

In the process of glycolysis

ten enzymes are involved in breaking glucose down to two pyruvate molecules.

Glycolysis results in the breakdown of a glucose molecule and the net production of 4 ATP molecules

False

During the early steps of glycolysis, glucose is converted to glucose 6-P and then converted directly to

Fructose 6-P

The binding of ATP to phosphofructokinase inhibits the glycolytic pathway

True

If insuffiencient oxygen is available for the anaerobic breakdown of pyruvate, it is converted to _____________

Lactate

Pyruvate dehydrogenase is located in the

the matrix of the mitochondrion

Which stage of cellular respiration is catalyzed by pyruvate dehydrogenase

intermediate stage