9/11/19

Question 1

humans produce billions of different antibodies, each with a different

Answer 1

binding site

Question 2

antibodies are immunoglobulin proteins produces by the immune system in response to

Answer 2

foreign molecules

Question 3

an antibody recognizes its

Answer 3

target molecule

Question 4

light blue region, hypervariable loops

Answer 4

bind antigen

Question 5

Antibodies are

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Y-shaped molecules with 2 identical antigen-binding sites, each of which is complementary to a small portion of the surface of the antigen molecule

Question 6

An enormous diversity of antigen-binding sites can be generated by

Answer 6

changing the length and amino acid sequence of the “hypervariable loops”, which is how the wide variety of different antibodies is formed.

Question 7

Antibodies are also invaluable in the laboratory, where they can be used to identify, purify, and study other molecules.

Answer 7

?

Question 8

using antibodies as molecular tags

Answer 8

for this class

Question 9

powerful and high specific catalysts

Answer 9

enzymes

Question 10

substrates

Answer 10

one or more ligands

Question 11

Enzymes bind to substrates, and convert them into

Answer 11

chemically modified products, doing this over and over again without themselves being changed.

Question 12

Enzymes act as catalysts that

Answer 12

permit cells to make or break chemical bonds.

Question 13

Enzyme provides a _ in which substrate bind in an arrangement that brings reactive portions of molecules into close juxtaposition to facilitate their productive interactions.

Answer 13

surface

Question 14

Enzymes can speed up the rate of a chemical reaction by

Answer 14

a factor of a million or more

Question 15

Enzymes can be grouped into _ based on the chemical reactions they catalyze

Answer 15

functional classes

Question 16

Enzymes greatly accelerate

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the speed of chemical reactions

Question 17

To study the enzyme-catalyzed reaction

Answer 17

purified enzyme and substrate are mixed together in a test tube and the speed at which an enzyme can convert its substrate to product is monitored.

Question 18

If the concentration of substrate added is large enough

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all of the enzyme molecules will be filled with substrate

Question 19

The rate of the reaction is limited by the

Answer 19

rate of the catalytic process on the enzyme active site. At this point, the enzyme is working at its maximum speed (Vmax)

Question 20

To determine how tightly an enzyme interacts with its substrate

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a value KM (Michaelis constant) is used

Question 21

KM is the concentration of substrate at which an

Answer 21

enzyme works at half of its maximum speed

Question 22

If a large amount of substrate is needed to achieve Vmax (large KM), this is an indication of

Answer 22

weak bindingc

Question 23

Lysozyme is an enzyme that acts as a

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natural antibiotic in egg white, saliva, tears, and other secretions

Question 24

Lysozyme severs the polysaccharide chains that form the cell walls of bacteria and causes

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cell wall to rupture and therefore bursting of bacteria

Question 25

Lysozyme catalyzes the hydrolysis reaction:

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the enzyme adds a molecule of water to a single bond between two adjacent sugar groups in the polysaccharide chain, thereby causing the bond to break

Question 26

Without lysozyme, polysaccharides can sit in water for years without being hydrolyzed. This is because

Answer 26

there is an energy barrier called activation energy that needs to be overcome.

Question 27

For a colliding water molecule to break a bond linking two sugars, the polysaccharide molecule has to

Answer 27

be distorted into a particular shape- the transition state- in which the atoms around the bond have an altered geometry and electron distribution. To distort the polysaccharide in this way requires a large input of energy.

Question 28

where the catalytic event happens

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active site of an enzyme

Question 29

The cell controls the amount of each protein it contains by

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controlling the expression of the gene that encodes that protein. It can also regulate the rate at which the protein is degraded

Question 30

The cell also controls protein activity by

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confining the participating proteins to particular subcellular compartments.

Question 31

the activity of an individual protein can be rapidly adjusted at

Answer 31

the level of the protein itself.

Question 32

A common type of control occurs when a molecule other than a substrate specifically binds to an enzyme at a special regulatory site,

Answer 32

altering the rate at which the enzyme converts its substrate to product.

Question 33

in _ ,an enzyme acting early in a reaction pathway is inhibited by a molecule produced later in that pathway. Thus whenever large quantities of the final product begin to accumulate, the product binds to an earlier enzyme and slows down its catalytic action.

Answer 33

feedback inhibition

Question 34

Allosteric enzyme have two or more binding sites that influence one another. Many enzymes contain at least 2 different binding sites:

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an active site that recognizes the substrate and one or more sites that recognize regulatory molecules

Question 35

Aspartate transcarbamoylase from E. coli catalyzes an important reaction to synthesize the pyrimidine ring of C, U, and T nucleotides. One of the final products of this pathway, cytidine triphosphate (CTP) binds to the enzyme to trigger a

Answer 35

conformational change, which turn it off whenever CTP is plentiful.

Question 36

Another method that eukaryotic cells use to regulate protein activity involves attaching a

Answer 36

phosphate group covalently to one or more of the protein’s amino acid side chains.

Question 37

Because each phosphate group carriers two negative charges, the enzyme-catalyzed addition of a phosphate group can cause a

Answer 37

conformational change by, for example, attracting a cluster of positively charged amino acid side chains from somewhere else in the same protein.

Question 38

The general reaction, shown here, entails transfer of a phosphate group from ATP to an amino acid side chain of the target protein by a protein kinase. Removal of the phosphate group is catalyzed by a second enzyme,

Answer 38

a protein phosphatase

Question 39

These proteins act as molecular switches: they are in their active conformation when GTP is bound, but they can hydrolyze this GTP to GDP, which releases

Answer 39

a phosphate and turns the protein to its inactive conformation.

Question 40

Cells have a second way to regulate protein activity by

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phosphate addition and removal. In this case, however, the phosphate is not enzymatically transferred from ATP to the protein. Instead, the phosphate is part of the guanosine triphosphate (GTP) that binds tightly various types of GTP-binding proteins

Question 41

Proteins can be purified from The purification procedure involves

Answer 41

cells or tissues breaking open the cells to release their contents. The resulting slurry is called a cell extract or lysate. The physical disruption is followed by an initial fractionation procedure to separate out the class of molecules of interest- for example, all the soluble proteins in the cell

Question 42

With this collection of proteins in hand, the job is then to isolate the desire protein. The standard approach involves purifying the protein through a series of chromatography steps. Chromatography uses different materials to separate the individual components of a complex mixture into proteins, or fractions, based on the properties of the protein- such as size, shape, or electrical charge. After such separation step, the fractions are examined to determine which ones contain the protein of interest. These fractions are then pooled and subjected to additional chromatography steps until the desired protein is obtained in pure form

Answer 42

know