Unit 3 - Enzymes

Question 1

enzyme

Answer 1

• A protein made of amino acids
• The shape/structure of the active site makes each enzyme different
• Enzymes increase the rate of chemical reactions by decreased the energy required for the reaction to perform (activation energy)

Question 2

how is each enzyme differentiated from each other?

Answer 2

Specific amino acids and their R groups have different properties which affects the shape of the protein and how it folds, leading to a different enzyme being formed. This created different active sites too.

Question 3

what is saturation point?

Answer 3

when enzyme number is constant and there is a maximum number of enzymes interacting with substrates.

Question 4

How do you increase the rate of reaction at the saturation point?

Answer 4

If you wanted to increase the rate of reaction at the saturation point you would need to add enzymes. However, if all the substrates have been turned into products then adding enzymes would do nothing.

Question 5

How does temperature affect the rate of reaction?

Answer 5

Increasing temperature initially affects enzyme activity because this initial increase causes more enzyme activity because molecules are moving around faster so it increases the chances of enzyme and substrate collisions. The enzyme goes through denaturation if temperature is increased too high from the optimum temperature. Lowering the temperature generally decreases enzyme activity because molecular movement slows down, resulting in fewer collisions between enzymes and substrates.

Question 6

How does pH affect the rate of reaction?

Answer 6

Each enzyme has an optimal pH at where the reaction rate is the highest. Changing from this optimal pH too much can lead to denaturation, where the enzyme’s structure breaks down, reducing or entirely halting its activity. Maintaining the optimal pH range is crucial for ensuring the highest efficiency in enzyme reactions, while too high or too low pH values can significantly slow the reaction or stop it altogether. Larger numbers of H+ & OH- ions distort the active site.

Question 7

Lipase

Answer 7

catalyzes digests triglycerides into glycerol and fatty acids

Question 8

Pepsin

Answer 8

catalyzes digests large polypeptides into smaller polypeptides and amino acids. In the stomach. Optimum temp is 37 degrees celsius or 98.6 degrees fahrenheit which is the normal human body temp.

Question 9

Amylase

Answer 9

catalyzes digests of carbohydrates into simple sugars

Question 10

Induced Fit Model

Answer 10

Shows the enzyme structure as more flexible and is complementary to the substrate only after the substrate is bound.

Question 11

Competitive Inhibitor

Answer 11

attaches to an enzyme’s active site but it produces no reaction. Competes with the substrate to bind to the active site. Effects reduced when substrate concentration increases

Question 12

Noncompetitive Inhibitor

Answer 12

Also called allosteric. Allosteric inhibitor molecules are described as noncompetitive because it doesn’t bind to the active site of the substrate. Can reduce the function of the enzyme/no reaction takes place because the enzyme changes shape.

Question 13

Endergonic reaction

Answer 13

requires an input of energy

Question 14

Exergonic reaction

Answer 14

energy is released

Question 15

what happens to energy when bonds are formed and when bonds are broken?

Answer 15

All bonds require energy to break
Energy is released when bonds are formed
Energy is absorbed when bonds are broken

Question 16

Anabolic reactions

Answer 16

bonds are being synthesized between substrates, requires input of energy (endergonic)
coupled with catabolic

Question 17

Catabolic reactions

Answer 17

bonds are being hydrolyzed, releases energy (exergonic)
coupled with anabolic

Question 18

what is adenine triphosphate and how is it used in cells?

Answer 18

Adenosine triphosphate (ATP) is used as “energy currency” in cells, Used for coupling exergonic and endergonic reactions

Question 19

hydrolysis of ATP

Answer 19

The hydrolysis of ATP results in net output of energy because you break the phosphate off of the ATP so it is a catabolic reaction, and catabolic reactions are exergonic reactions. Exergonic reactions are when energy is released. This energy is used for cellular processes that require energy like active transport, cell movements, anabolism

Question 20

why does the hydrolysis of ATP release energy even though bonds are being broken?

Answer 20

During ATP hydrolysis, the bond between the terminal phosphate and the rest of the molecule is broken, producing ADP (adenosine diphosphate) and an inorganic phosphate (Pi). Breaking this bond does require energy input.

After the bond is broken, new bonds form in the products: the ADP molecule, the free phosphate ion (Pi), and the water molecules involved. The formation of these new bonds releases more energy than was required to break the original ATP bond.

The combination of bond-breaking and bond-forming results in a significant net release of energy.

Note: we don’t necessarily have to know this for the test, this is just for understanding of why ATP hydrolysis releases energy instead of absorbs energy

Question 21

Phosphorylation

Answer 21

addition of phosphate onto ADP to form ATP. Endergonic because phosphate is added onto ADP which requires energy

Question 22

substrate-level phosphorylation

Answer 22

Direct transfer of a phosphate group to ADP. Happens in the cytoplasm during Glycolysis and in the mitochondrial matrix during the Krebs Cycle.

Question 23

electron transfer (oxidative phosphorylation)

Answer 23

Energy from the movement of electrons from one molecule to another, via electron carriers like NAD+ and FAD, is used to synthesize ATP. Most cellular ATP is synthesized by electron transfer in the mitochondria.

Question 24

Oxidation

Answer 24

A molecule loses electrons (and often hydrogen atoms)
LEO - Loss of Electrons is Oxidation

Question 25

Reduction

Answer 25

Reduction: A molecule gains electrons (and often hydrogen atoms)
GER - Gain of Electrons is Reduction

Question 26

Redox Reactions

Answer 26

Oxidation and reduction are coupled with each other. Electrons are passed from one substance to another - as one substance loses electrons, the other gains electrons. Can think of it in gain or loss of hydrogen atoms
Transfers of hydrogen atoms involve transfers of electrons (H = H+ + e–)
When a molecule loses a hydrogen atom, it becomes oxidized.
Use NAD+ and FAD to transport electrons (and hydrogen)

Question 27

How does hydrogens indicate stored energy?

Answer 27

The more reduced a molecule is (has electrons/hydrogen), the more stored energy it has. This is because when NAD+ or FAD take hydrogen from a molecule, it releases energy. Reduced molecules, such as glucose or fatty acids, have many electrons that can be transferred to electron carriers like NAD⁺ and FAD. As electrons move through these carriers, energy is released and used for processes like ATP synthesis.

Question 28

Hydrogen Acceptors

Answer 28

NAD+ and FAD: job is to take hydrogens from organic molecules and hold on to them ​to be used in later reactions (electron transfer phosphorylation/oxidative phosphorylation)
NAD → accepts electrons and becomes NADH.
FAD → accepts electrons and becomes FADH₂

Question 29

Reduction of NAD+ and FAD

Answer 29

highly endergonic. electrons do not remain with NADH or FADH2

NAD⁺ + 2H⁺ + 2e⁻ → NADH + H⁺

FAD + 2H⁺ + 2e⁻ → FADH₂
FAD, in its oxidized state, accepts two electrons (2e⁻) and two protons (2H⁺) to form FADH₂

Question 30

Oxidation of NADH and FADH2

Answer 30

Exergonic. Due to oxygen’s high electronegativity, it readily accepts electrons from the reduced NADH or FADH2 molecule. Oxidation of NADH or FADH2 releases more energy than hydrolysis of ATP. Oxidation of NADH releases more energy than the oxidation of FADH2 so in terms of energy release, (oxidation of NADH > oxidation of FADH2 > ATP hydrolysis)

Oxidation:
NADH + H+ + ½ O2 —> NAD+ + H2O

Question 31

reaction specificity

Answer 31

The ability of an enzyme to selectively catalyze a particular chemical reaction among many possible reactions that a substrate molecule could undergo

This goes beyond substrate recognition. Once bound to a substrate, the enzyme ensures that only a specific reaction occurs, even if the substrate could theoretically undergo several different transformations. Reaction specificity is due to the precise arrangement of amino acids in the enzyme’s active site, which creates a unique environment that favors only one reaction pathway.

Ex: the enzyme hexokinase specifically catalyzes the phosphorylation of glucose, even though glucose could participate in other types of reactions.