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BSC 2010 - Biology I > Exam #3 > Flashcards

Flashcards in Exam #3 Deck (183)
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151

Enzyme function also depends on __.

pH. Important for enzyme conformation

152

The enzyme that functions in your stomach has an optimum pH of __.

2. That's where it's most active

153

Why does the stomach become acidic during digestion?

It's all about the digestion of protein. The stomach is for the digestion of protein. Which is typically in a globular form. A globular form is hard to digest. So you change the pH drastically so the enzyme denatures...and now the hydrolyses can now cut the protein because it's vulnerable.

154

The situation when a molecule is blocking the active site is called _________ _________.

competitive inhibition

155

If a molecule binds to an allosteric site, it changes the shape of the enzyme, which...

turns the enzyme off. It changed the shaped. Structure determines function.

156

Competitive inhibition involves an _______ site.

active

157

Noncompetitive inhibition involves an _________ site.

allosteric, means "other shape"

158

Allosteric regulation can either work _______ OR _______.

positively or negatively

159

If it's negative, we call that __________ __________.

noncompetitive inhibition

160

Which one may be countered by increasing substrate concentration? Competitive inhibition or noncompetitive inhibition?

Competitive inhibition. If the inhibition is working this way...**adding more substrate can outcompete the inhibitor.**

161

In biology, when we say "two molecules bind,"...they also _____ _____. Remember, weak interactions are ________. Bind, come apart, bind, come apart. Yes, the inhibitor is binding and blocking the active site, but a moment later it will come off. And if there's more substrate, guess who's going to bind next? Substate and not the inhibitor. It is possible to outcompete the inhibitor by adding more substrate.

come apart, reversible

162

Do all enzymes have active sites?

Every enzyme has an active site, it's not an enzyme without an active site

163

Do all enzymes have allosteric sites?

NO, that's going to depend on the enzyme.

164

What is the regulatory molecule?

You get a snake bite and the poison might be the inhibitor.
The inhibitor might be something that's already in your body that's blocking the active site.

165

Is it necessary to regulate all the enzymes of a pathway?
Lets say we have a pathway with 5 enzymes...if we want to shut this pathway off, must we inactivate all 5 enzymes? How could we do this in a more efficient way?

There's a mechanism to shut off a pathway. An entire pathway...using the final product of the pathway. Shut off a pathway using the final product. This is referred to as *FEEDBACK INHIBITION.*

166

Isoleucine is made from threonine in __ steps.

5

167

It takes 5 steps to make isoleucine.
Enzyme #1 has an ________ site. The allosteric site is complementary to the shape of isoleucine. So isoleucine can bind to that enzyme, and inhibit it. What's the effect on that binding inhibition?

allosteric. You turn off the enzyme.

168

What happens if you shut off enzyme one?

You no longer make your product.

169

So we've shut off an entire pathway through the _______ of that pathway, which ______ back either the first enzyme or a very early enzyme in the pathway. This is called _______ inhibition.

product, feeds, feedback

170

By turning off key enzymes, you can shut down entire _______.

pathways

171

Where an enzyme is ________ can affect the rate of an enzyme catalyzed reaction

located

172

Describe three ways that cells localize their enzymes for more efficient functioning in metabolic pathways

1) In organelles
2) As membrane proteins
3) In multi-enzyme complexes

173

ATP hydrolysis can be COUPLED to an endergonic reaction to make that reaction happen. For example, an unfavorable reaction with a delta G of ____ could be driven (or fueled) by a mole of ATP.
a) +5.5 kcal/mole
b) +8.0 kcal/mole
c) -14.6kcal/mole
d) -7.3 kcal/mole
e) 0 kcal/mole

+5.5 kcal/mole. The delta g of ATP hydrolysis - an exergonic reaction - is -7.3 kcal/mole. ATP hydrolysis can be used to fuel an endergonic reaction - one with a positive delta G - that requires LESS THAN 7.3 kcal/mole

174

During coupling, HOW is ATP actually used to make a reaction happen?

A phosphate is transferred from ATP to a reactant.

175

_________ is the basic mechanism by which ATP is used to do work.

Phosphorylation

176

Either a _______ or a ______ may be phosphorylated.

reactant or a protein

177

In steps _ and _ of glycolysis, phosphorylation is used to boost the energy of metabolic intermediates.

1 and 3

178

How exactly does ATP drive the sodium-potassium pump?

A phosphate is transferred from ATP to the pump

179

Does allosteric regulation STIUMULATE or INHIBIT an enzyme's activity?

Either stimulates or inhibits

180

Isoleucine biosynthesis is regulated by FEEDBACK INHIBITION; an early step of its metabolic pathway is blocked at high concentrations of _________.

isoleucine