Midterm 1-1

Question 0

What two hurdles do enzymes help reactions overcome?

Answer 0

Chemical reactions occur when molecules collide with the correct orientation and have enough kinetic energy to break and/or form chemical bonds despite the repulsion of the electrons involved in the bond.

Question 1

What are enzymes and what do they do?

Answer 1

Enzymes are catalysts; they facilitate reactions by physically bringing substrates together in orientations that help reactions occur.

Question 2

Where do enzymes bring substrates?

What are substrates?

Answer 2

Enzymes bring reactant molecules (substrates) together in the enzyme’s active site - usually a groove or cavity within the enzyme’s globular shape.

Question 3

What happens to enzymes once substrates bind to them? (Comes with an example)

Answer 3

Many enzymes change shape when reactants bind; this is called an induced fit. For example, glucokinase (an enzyme that phosphorylates glucose) binds ATP and glucose and then folds in over the active site to bring the substrates closer together.

Question 4

How do enzymes interact with substrates?

Answer 4

Initial binding of substrates to an active site often relies on hydrogen bonding and other weak interactions with exposed amino acids. Further interaction between the enzyme and the substrate creates an unstable intermediate called transition state.

Question 5

What is activation energy?

Answer 5

Activation energy is the kinetic energy necessary to strain chemical bonds enough to achieve this transition state. This activation energy is necessary even for spontaneous exergonic reactions.
US Army is legit! ;D

Question 6

How does kinetic energy relate to chemical reactions?

Answer 6

Kinetic energy depends on temperature, and reactions happen only when reactants have enough kinetic energy to reach the transition state.

Question 7

What does exergonic mean?

Answer 7

Chang in G is negative (the reactants have. Ore free energy than the products), so the reaction is exergonic and spontaneous.

Question 8

Why is the free energy high in the transition state?

Answer 8

Transition-state free energy is high because old substrate bonds are strained and unstable. The less stable the transition state, the higher the activation energy (Ea) and the slower the reaction.

Question 9

What do reaction rates depend on?

Answer 9

Reaction rates thus depend on 1) Ea and 2) the kinetic energy temperature of the reactants (which determine the likelihood of reaching the transition state by surmounting Ea).

Question 10

What do enzymes do to the transition state?

How do the react with the reactants?

Answer 10

In addition to brining substrates together, enzymes facilitate reactions by stabilizing the transition state, which lowers Ea. This speeds up reaction rates because when activation energy is lower, less kinetic energy is necessary for the reaction to proceed.

Question 11

How do enzymes stabilize transition states?

Answer 11

Enzymes stabilize transition states via interaction between reactants and amino acid R-groups at the active site.

Question 12

How do R-groups take part in the reaction?

Answer 12

R-groups may form temporary covalent bonds that help transfer atoms from one reactant to another or provide an acidic or basic micro environment that assists proton transfer.

Question 13

What do enzymes change in a reaction and what stays the same?

Answer 13

Enzymes do not change change in G or the energy of the reactants or products. Only Ea, the amount of free energy required to achieve the transition state is affected.

Question 14

How fast are enzymes?

Answer 14

Most biological reactions occur only at meaningful rates in the presence of an enzyme; many enzymes allow reactions to proceed millions of times faster than they would without the enzyme.
hella fast

Question 15

What happens to the enzyme after the chemical reaction?

Answer 15

Enzymes are not used or even changed when the catalyze a chemical reaction.

Question 16

What the 3 steps of enzyme action?

Answer 16

The three steps of enzyme action are:

1) Initiation - brining reactants together in the active site
2) Transition State Facilitation - chemical interactions that lower Ea
3) Termination - products do not fill well in the active site, so they live
* fun fact - the three steps in a radical addition reaction is initiation propagation and termination, but propagation can keep propagating the formation of radicals such that it can have a large expenditure of energy can occur leading to an explosion. H2O2 (hydrogen peroxide) reacts this way. Home H2O2 is only 2% H2O2. Rocket fuel is only 30%. In all don’t open old bottles of H2O2 because it was even higher that 30% :O so you will explode*

Question 17

How are reaction rates measured?

Answer 17

Reaction rates are measured as amount of product produced per second.

Question 18

How does does substrate concentration affect reaction rate in uncatalyzed substrates?

Answer 18

Without any enzyme, increases in substrate concentration cause gradual but steady increases in reaction rates, but the overall all reaction is very slow.

Question 19

Why does reaction rate level out

Answer 19

the leveling out of enzyme catalyzed reaction rates at high substrate concentrations (saturation kinetics) occurs when all active sites are filled with substrate. At this point, further increase in substrate availability does not impact reaction rate.

Question 20

Do enzymes work alone

Answer 20

Many enzymes require extra atoms or molecules that are not part of their primary structure to function normally. Cofactors, coenzymes, and prosthetic groups are found in active site, where they help stabilize the transition state

Question 21

What are cofactors

Answer 21

They are organic ions such as zinc ion, magnesium ion, or iron ion, that interact with enzymes. These ions may also have helped catalyze reactions early on in evolution

Question 22

What are coenzymes

Answer 22

They are organic molecules like NADH or FADH2 that reversably interact with enzymes

Question 23

What is the prosthetic group (enzymes)

Answer 23

They are molecules or atoms that permanently attach to enzymes

Question 24

Why do deficit disease form

Answer 24

Many vitamins are necessary because they are precursors for enzyme cofactors. Deficiency diseases occur when there are not enough enzyme cofactors to allow normal enzyme function

Question 25

What factors affect enzyme function

Answer 25

Enzyme function relies on enzyme shape. Thus, conditions that change an enzymes shape will change its function

Question 26

What is enzyme activity influenced by

Answer 26

Enzyme activity is strongly influenced by temperature (effect kinetic energy and enzyme folding and movement) and pH (effect on R-group charge and proton and electron transfer ability of the active sites)

Question 27

What information about activation can tell you about the enzymes environment

Answer 27

Most enzymes function best at some particular temperature and pH. Because natural selection favors organisms with enzymes that function efficiently, temperature and pH optima usually reflect an enzymes environment

Question 28

Is it possible for the same type of bacteria to have different optimas

Answer 28

Bacteria from cool, neutral pH environments have a version of chitinase (an enzyme that digests fungal cell walls) that works best at cool temperatures and a neutral pH. Bacteria that live in hot acidic environments have chitinase that works best at hot temperatures and an acidic pH

Question 29

What affects shape and movement of enzymes

Answer 29

Temperature, pH, and other factors that affect enzyme shape and movement affect rate of enzyme catalyzed reactions

Question 30

How do cells regulate enzyme activity

Answer 30

Control of enzyme function is critical to cells. Cells use several mechanisms for regulating enzyme activity, primarily using regulatory molecules that alter enzyme structure

Question 31

What do regulatory molecules do to enzymes

Answer 31

Many regulatory molecules activate or inactivate enzymes via noncovalent “reversible” binding

Question 32

What is competitive inhibition

Answer 32

Competitive inhibition occurs when a regulatory molecule has a similar size and shape to the substrate and can thus compete with th substrate for active site binding

Question 33

What is allosteric regulation

Answer 33

It occurs when a molecule changes enzyme conformation by binding at a location other than the active site. Allosteric regulation is more common than competitive inhibition and can either increase or decrease enzyme activity.

Question 34

What is competitive inhibition/allosteric regulation affected by

Answer 34

Both competitive and allosteric regulation are affected by the regulatory molecule’s concentration, which is typically tightly controlled within the cell

Question 35

What makes an irreversible chemical change

Answer 35

Enzyme activity can be changed by irreversible chemical changes, as when part of the protein must be removed to activate the enzyme

Question 36

What happens when a phosphate group is added to an enzyme

Answer 36

More commonly, phosphate groups are added. This phosphorylation may be catalyzed by the enzyme itself or by another enzyme. The negative charges of the phosphate