Cell and Molecular Biology Ch. 1 pt 2

Question 1

Microscopy cont. What does centrifugation do?

Answer 1

Prepares sample for observ. or further experim. by spinning and separating liquified cell homogenates into layers based on density

Question 2

Order in which cell parts separate via centrifugation:

Answer 2

1. Most dense pelleting first
2. Least dense pelleting last

Question 3

Order in which cells separate via centrifugation starting from first component to pellet at the bottom and progressively spinning faster:

Answer 3

Nuclei layer –> mitochondria/chloroplasts/lysosomes –> microsomes/small vesicles –> ribosomes/viruses/larger macromolecules

Question 4

Centrifugation can be ________ centrifugation or density centrifugation.

Answer 4

Differential - relies on density, shape, and speed at which macromolecule travels
- Spin pattern is differential: spin, separate dense pellet, and repeat.

Question 5

What does differential centrifugation form?

Answer 5

Continuous layers of sediment, where insoluble proteins are found in the pellet while soluble proteins remain in the supernatant, liquid above the pellet.

Question 6

Characteristics of chemical rxns

Answer 6

The concentration of reactants and products determines which way the rxn will go.

Question 7

When a rxn is in equilibrium, the _____ of formation of reactants and products is equal and there is ___ net production.

Answer 7

Rate; 0

Question 8

Chemical rxns in which small molecules are assembled into larger molecules are ________ rxns.

Answer 8

Anabolic - Energy is required

Question 9

When large molecules are broken down into small molecules, it is a ________ process.

Answer 9

Catabolic - Energy is released

Question 10

What are globular proteins that act as ________.

Answer 10

Catalysts

Question 11

What lowers the activation energy of a rxn, thereby accelerating the rate of the overall rxn.

Answer 11

Catalysts

Question 12

Are enzymes substrate-specific?

Answer 12

Yes, they remain unchanged during the rxn, catalyze both forward and reverse directions of the rxn, have varying fxn based on pH and temp., and have an active site that binds substrates via induced fit.

Question 13

What are non-protein molecules that assist enzymes usually by donating or accepting some component of a rxn, such as electrons or functional groups.

Answer 13

Cofactors

Question 14

What are organic cofactors called?

Answer 14

Coenzymes, and they are commonly derived from vitamins

Question 15

True or False. Coenzymes usually donate or accept electrons.

Answer 15

True

Question 16

________ cofactors are usually metal ions like Fe2+ and Mg2+.

Answer 16

Inorganic

Question 17

If the cofactor binds tightly or covalent to the enzyme, it is referred to as a __________ group.

Answer 17

Prosthetic

Question 18

______ is a common source of activation energy, and the compound stores its potential energy in the form of _______ chemical energy.

Answer 18

ATP; chemical

Question 19

New ATP is formed via ____________, _______ and ___________ come together using energy from an energy rich molecule like glucose.

Answer 19

Phosphorylation; ADP and phosphate

Question 20

Why must enzymes be strictly regulated?

Answer 20

To ensure that they are only functional for specific use.

Question 21

Enzymes can be regulated using the following methods (6)

Answer 21

1. Km
2. Allosteric enzymes
3. Competitive inhibition
4. Noncompetitive inhibition
5. Uncompetitive/ anti-competitive inhibition
6. Cooperativity

Question 22

Regulation of Enzymes: What is Km

Answer 22

Michaelis constant which represents the substrate concentration at which the rate of rxn is half of the max velocity of the enzyme, or Vmax

Question 23

Regulation of Enzymes: Allosteric enzymes have both an ________ _______ for substrate binding and an __________ site for the binding of an allosteric effector (can be an activator or inhibitor)

Answer 23

Active site; allosteric

Question 24

Regulation of Enzymes: _________ inhibition: a substance that mimics the substrate and inhibits the enzyme by binding at the active site.

Answer 24

Competitive

Question 25

The effect of competitive inhibition can be overcome by increasing ________ concentration.

Answer 25

Substrate. Remember, Km is raised but Vmax is not.

Question 26

Regulation of Enzymes: Noncompetitive inhibition - substance inhibits enzyme by binding elsewhere than the active site, allowing the ______ to still bind, but the rxn is prevented from _______________.

Answer 26

Substrate; completing. Remember, Km is unchanged but Vmax is lowered.

Question 27

Regulation of Enzymes: Describe uncompetitive/ anti-competitive inhibition.

Answer 27

Occurs when an enzyme inhibitor binds only to the formed enzyme-substrate (ES) complex, preventing formation of product.

Question 28

In a way, Km inversely represents binding affinity: a small Km indicates that an enzyme requires a ______ amount of substrate to become saturated.

Answer 28

Small; hence, the max velocity is reached at relatively low substrate concentrations.

Question 29

A large Km indicates the need for _______ substrate concentrations to achieve max rxn velocity.

Answer 29

High; A higher Km equates to worse substrate binding, while a lowered Km equals better substrate binding.

Question 30

Review: __________ inhibitor - same Vmax, different Km

Answer 30

Competitive

Question 31

Review: _________ inhibitor - same Km, different Vmax

Answer 31

Non-competitive

Question 32

Regulation of Enzymes: Cooperativity

Answer 32

Phenomenon that occurs where an enzyme becomes more receptive to additional substrate molecules after one substrate molecule binds to the active site

Question 33

Example of cooperativity

Answer 33

Hemoglobin is a quaternary protein with 4 subunits that each has an active site for binding oxygen. As the first oxygen binds, the other active sites become increasingly likely to bind oxygen. Note: hemoglobin is NOT an enzyme.