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AP Biology - Mrs. Unger 24-25 > Unit 4: Bioenergetics, ATP, and Enzymes > Flashcards

Unit 4: Bioenergetics, ATP, and Enzymes Flashcards

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1
Q

State the laws of thermodynamics

A

First: Energy can’t be created or destroyed
Second: Energy transformations always result in an increase in entropy

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2
Q

Describe

Entropy

A

Chaos
Randomness
Unusable energy
The opposite of free energy

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3
Q

Describe

Free energy

A

Measure of instability
Usable energy
The opposite of entropy

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4
Q

Explain

ΔG

A

Changes in free energy that occurs over the course of a chemical reaction
-ΔG = the system (molecules in the reaction) has LOST free energy == exergonic
+ΔG = the system has GAINED free energy == endergonic

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5
Q

What is a positive ΔG?

A

Increase in free energy in a system
More energy in PRODUCTS than REACTANTS
Endergonic == Energy absorbed into system

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6
Q

What is negative ΔG?

A

Decrease in free energy in a system
More energy in REACTANTS than PRODUCTS
Exergonic == Energy released into environment

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7
Q

Define / briefly describe

Spontaneous

A

Exergonic
Reactions that are energetically favorable

NOT THE SAME AS “FAST”!!!

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8
Q

How can endergonic reactions happen?

A

Endergonic reactions REQUIRE energy from another source
Often “coupled” with exergonic reactions
So long as exergonic reaction RELEASES more energy than endergonic ABSORBS, the pair of reactions will still be possible

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9
Q

What are the types of activities cells do that require energy?

A

Chemical work: Coupling an exergonic reaction with an endergonic one to allow the endergonic reaction to happen
Transport: Establishing concentration gradients (which increases order / decreases entropy)
Mechanical: Moving cell parts / cytoskeleton

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10
Q

Describe

Energy coupling

A

Pairing of an exergonic reaction (releases energy!) with an endergonic one (which couldn’t happen without an input of energy from environment)

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11
Q

What is this molecule?

A

Adenosine triphosphate (ATP)

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12
Q

What is this part of ATP called?

A

A phosphate group

Specifically, the third phosphate, which is broken off when ATP -> ADP

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13
Q

What is this part of ATP called?

A

Phosphate

This is the 2nd phosphate (counting from sugar); still present in ADP

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14
Q

What is this part of ATP called?

A

Ribose
Reminder: Nucleotides contain a pentose / 5-carbon sugar, which is ribose here

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15
Q

What is this part of ATP called?

A

Adenine
Reminder: Nucleotides contain a nitrogenous base, which is adenine here

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16
Q

What is this part of ATP called?

A

Adenosine
(Ribose + Adenine)

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17
Q

How is ATP “used”?

A

ATP → ADP + Pi
The last phosphate breaks off, leaving ADP behind.
ADP and Pi contain WAY less free energy (are more stable / less reactive)
This energy is released, which can be used to do cell work

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18
Q

How is ATP made?

General - *not specifically asking what mechanisms are used to make ATP!

A

ADP + Pi → ATP
Energy must be supplied to build ATP, which has more free energy than ADP and phosphate do separately

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19
Q

What processes can provide the energy necessary for regenerating ATP?

A

Cellular respiration and photosynthesis

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20
Q

Define

Reaction Rate

A

The speed at which reactants are converted to products

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21
Q

Define

Catalyst

A

A chemical that:
1. Speeds up the rate of a chemical reaction
2. Is not used up during the reaction

22
Q

Can catalysts alone make endergonic reactions happen?

A

NO!
Catalysts speed up reactions that would otherwise happen more slowly
BUT they don’t make reactions happen that otherwise wouldn’t be able to

23
Q

Define

Enzyme

A

Biological molecules that act as catalysts
- Usually (but not always) proteins
- Encoded by our cells’ DNA

24
Q

Define

Activation Energy

A

The energy that is required to break reactants / make them enter an unstable state so that they are able to react / form products

25
Q

Define

Transition state

A

Molecular structure that is highly unstable (and thus can react)

26
Q

How does activation energy limit the rate of reactions?

A

High activation energy: Requires system to absorb a LOT of energy, making the reaction less likely to occur -> SLOWER

27
Q

What do enzymes do to the rate of reactions?

A

-Increase rate (more product / faster) by
-Lowering activation energy

28
Q

Define

Substrate

A

A molecule that binds to the enzyme’s active site
The reactant of an enzyme-catalyzed reaction

29
Q

Describe

Enzyme Structure

A

Protein (usually)
Folded polypeptide, which has an ACTIVE SITE (area where substrate bind), and potentially other sites (ALLOSTERIC SITES) for other molecules to bind

30
Q

How do enzymes increase activation energy?

A

They don’t.
They lower them.

haha. i tricked you. or not.

31
Q

How do enzymes lower activation energy?

A

Possible ways:
* Stress bonds, making them more likely to reach transition state
* Act as a template to place substrates together and in correct orientation
* Produce a small microenvironment where the reaction is more suitable to react

32
Q

How do enzymes affect ΔG of a reaction?

A

They don’t.

33
Q

What type of reaction?

A

Exergonic
-ΔG

34
Q

Identify letters a through e

A

a: energy in the reactants
b: activation energy without enzyme
c: activation energy with an enzyme
d: ΔG
e: energy in the products

35
Q

Identify letters a through e

A

a: energy in the reactants
b: activation energy without enzyme
c: activation energy with an enzyme
d: ΔG
e: energy in the products

36
Q

What kind of reaction is this?

A

Endergonic (+ΔG)

37
Q

Define

Denaturation

A

The permanent loss of 3D shape of a molecule
In proteins/enzymes: Loss of tertiary and quaternary structure

38
Q

How does denaturation affect an enzyme’s ability to catalyze reactions?

A

Small changes to shape: slight lessening of catalytic ability
Complete denaturation: enzyme does not function

39
Q

What conditions may cause an enzyme to denature?

A

Very high temperatures (above optimal)
Acidic conditions (below optimal pH)
Basic conditions (above optimal pH)

40
Q

T/F: All enzymes have the same optimal conditions

A

FALSE!!!
Each enzyme has a specific optimal temp, pH, etc and range at which it will work
Each enzyme is best suited for the environment in which it evolved

41
Q

Describe the effect of cold temperatures on enzyme-catalyzed reactions, and why.

A

Low temp = low molecular motion = fewer collisions
Reactions slow in cold reactions

42
Q

Describe the effect of high temperatures on enzyme-catalyzed reactions, and why.

A

High temp = high molecular motion = more collisions
BUT
high temperatures and excess thermal energy can cause hydrogen bonds (in tertiary and quaternary structure of protein) to break
If the enzyme denatures, then the enzyme-catalyzed reaction rate plummets/stops

43
Q

Describe the effect of pH variations on enzyme-catalyzed reactions, and why.

A

Proteins are stabilized by hydrogen and ionic bonds (among others)
These bonds are influenced by proton (H+) concentration
Very low pH = high concentration of H+
Very low pH = low concentration of H+
If pH strays from optimal, the enzyme can denature and stop functioning

44
Q

Define

Cofactors

A

Nonprotein structures (atoms, ions, or molecules) that bind to enzymes and are necessary for proper catalytic function

45
Q

Two types of cofactors

A

Vitamins (organic molecules) and minerals (inorganic, usually ions)

46
Q

Define

Active Site

A

Part of enzyme where substrate binds
* Lock and key model describes active site as perfectly complementary to substrate
* Induced fit model describes active site and substrate as somewhat complementary, but binding leads to a better fit

47
Q

Define

Enzyme inhibition

A

Methods of irreversibly or reversibly stopping or slowing an enzyme’s activity

48
Q

What is the importance of enzyme inhibition?

A

It ensures only necessary enzymes are functioning
Ex: If one enzyme is involved in polymerizing amino acids into proteins, while another was involved in hydrolyzing proteins into amino acids, it’d be kind of stupid to have them both functioning simultaneously!

49
Q

Describe

Competitive Inhibition

A

A molecule (not the substrate) binds to active site of enzyme, blocking correct substrate from binding
Increasing concentration of substrate can reduce effect of competitive inhibitor

50
Q

Describe

Noncompetitive inhibition

A

A molecule (not the substrate) binds to an area other than the substrate, causing a change to the enzyme that prevents binding to the substrate
Increasing the substrate concentration does NOT reduce the effect of the noncompetitive inhibitor
A type of allosteric regulation

51
Q

Define

Allosteric regulation

A

Controlling an enzyme’s function by having a molecule attached to a part of the enzyme other than the active site

52
Q

Define

Allosteric site

A

A part of an enzyme (other than the active site) where a molecule can bind, which changes the shape of the active site

AP Biology - Mrs. Unger 24-25 (21 decks)

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