Lecture 2 - Energy & Enzymes (Ch 4)

Question 1

what are bioenergetics?

Answer 1

the study of the transformation of energy in living organisms

Question 2

what is a chemical reaction?

Answer 2

a transformation of substances by forming or breaking covalent bonds. (Chemical reactions occur when chemical bonds between atoms are formed or broken.)

Question 3

what happens when bonds are formed or broken?

Answer 3

when bonds are formed, covalent bond energy is stored.
when bonds or broken, covalent bond energy is released

Question 4

are chemical reactions usually spontaneous?

Answer 4

no, they are usually not spontaneous

Question 5

what are the reactants of chemical reactions?

Answer 5

they are also called substrates; reactants are substances that go into chemical reactions. Substrates are reactants that bind to the enzyme to create a product.

Question 6

what are the products in chemical reactions?

Answer 6

they are the substances produced at the end of the reaction

Question 7

what is activation energy?

Answer 7

the minimum energy input to start a reaction. the higher the activation energy, the harder it is to start the reaction.

Question 8

what is an exergonic reaction?

Answer 8

it is one of two types of chemical reactions; it is a net release of bond energy because it breaks a covalent bond. (the products have less energy than the reactions)

Question 9

what is an endergonic reaction?

Answer 9

the other type of a chemical reaction, it is the net input of bond energy because it forms bonds. (the products have more energy than the reactants)

Question 10

what is a coupling reaction?

Answer 10

when energy is released (from an exergonic reaction) and when the energy drives the endergonic reactions.

Question 11

what happens to released energy from exergonic reactions?

Answer 11

The energy released by exergonic reactions is used for the input of endergonic reactions. The energy released can be trapped in the high-energy electrons of NADH, FADH2, and NADPH.

Question 12

give an example of the formula for exergonic and endergonic reactions

Answer 12

exergonic: A + B —-> C + D + energy
endergonic: energy + A + B —-> C + D
*the arrow represents enzymes

Question 13

In exergonic reactions, what happens to the remaining energy that isn’t trapped?

Answer 13

The remaining energy is given off as heat, which is the majority of the energy.

Question 14

what is the processing of coupling?

Answer 14

The energy released from exergonic reactions becomes the majority of heat energy (we don’t use that) and the remaining high-energy electrons. The high-energy electrons are captured by nucleotides and the nucleotides transfer energy and electrons. The high-energy electrons become NADPH, NADH, and FADH2 which all become energy that is utilized. NADH and FADH2 become ATP which becomes energy utilized as well. The energy utilized will go into an endergonic reaction.

Question 15

explain the slide on ATP, NADH, and FADH2

Question 16

what are enzymes made of?

Answer 16

all enzymes are made of proteins

Question 17

what are the characteristics of enzymes?

Answer 17

1. The structure cannot be changed in a reaction = it is the catalyst (what speeds up the chemical reaction)
2. It is not consumed in a reaction
3. There is a low activation energy to speed up the reaction rate (the enzymes lower the activation energy)
4. There is limited amount produced by the cell (we make enzymes in limited amount)

Question 18

what are the pockets in enzymes for?

Answer 18

so that the substrate can bond to the enzyme

Question 19

what are the 3 properties of enzymes?

Answer 19

1. Specificity: enzymes are really specific; substrate’s shape fits snuggly with the enzymes active site.
2. Competition: Substrates with similar structures compete for the enzymes active site
3. Saturation: When the concentration of the substrate is more than the concentration of the enzyme; all enzymes are occupied. (The enzymes are working at their max reaction rate, so the reaction rate/saturation point is high)

Question 20

what is an enzymes active site?

Answer 20

where the substrate bonds to the enzyme

Question 21

what are isozymes? + an example?

Answer 21

they are enzymes that catalyze the same reactions but under different conditions/tissues/locations.
example: lactate dehydrogenase (LDH)

Question 22

how does ATP work in a coupling reaction? + what does it stand for?

Answer 22

Adenosine Triphosphate.
ATP + H2O —-> (output of energy) ADP + Pi

Question 23

how does NADH work in a coupling reaction?

Answer 23

NAD+ has energy incoming and 2H+ is added. This is endergonic. Then it becomes NADH.
NADH releases energy and 2H+ and it becomes NAD+. This is exergonic. This keeps going.

Question 24

How does FADH2 work in a coupling reaction?

Answer 24

FAD+ has an input of energy and 2H+ which becomes FADH2. Then 2H+ and energy is taken out (utilized) and becomes FAD+.

Question 25

What are the ways an enzyme goes through activation?

Answer 25

Through proteolytic activation and addition of cofactors.

Question 26

What is proteolytic activation?

Answer 26

It is when a part of the protein structure (part of the enzyme) is cut out.

Question 27

What is a zymogen or proenzyme?

Answer 27

These are the names for the inactive enzymes

Question 28

what is the addition of cofactors in the activation of enzymes?

Answer 28

It is when the enzyme adds and creates binding/active sites in order to start the chemical reaction. These come from our diet.
Cofactors complete the missing active site.

Question 29

What are the two types of cofactors?

Answer 29

1. Inorganic cofactors: made of inorganic material. Example: Ca++, Mg++
2. Coenzymes: these are the organic cofactors made of organic material. Example: Vitamin B complex; B12.

Question 30

What are the ways enzymes go through inactivation?

Answer 30

Through inhibitors and denaturation.

Question 31

What do inhibitors do?

Answer 31

They block the active site which prevents the substrate from binding. You can add another inhibitor to an enzyme as well.
Inhibitors can be competitive.

Question 32

what does denaturation do?

Answer 32

Denaturation causes enzymes to lose their 3D shape and function. Example: turning it from quaternary to tertiary. It is usually permanent. It looses its shape by breaking the bonds.

Question 33

What are two ways that denaturation happens?

Answer 33

1. Temperature: Every enzyme has its own desired temperature. When the temperature is outside of the desirable range, it can cause denaturation.
2. pH: Outside of the safe range of pH can cause denaturation.

Question 34

What is metabolism of energy and enzymes?

Answer 34

All of the chemical reactions happening in an organism are from metabolism

Question 35

What are the three types of metabolism?

Answer 35

1. Catabolism
2. Anabolism
3. Pathways

Question 36

what is catabolism?

Answer 36

Catabolism: It is the breaking down of large molecules (biological macromolecules). This releases energy. Example: breaking down starch and therefore breaking bonds. This is an exergonic reaction.

Question 37

what is anabolism?

Answer 37

Anabolism: This synthesizes (forms) large molecules. This utilizes energy. Example: creating starch by forming bonds.

Question 38

what are pathways of metabolism?

Answer 38

Some metabolism requires multiple steps which are called pathways.
Pathways: Require enzymes between each step of metabolism.
They convert a substrate molecule or molecules through a series of metabolic intermediates, eventually yielding a final product or products.

Question 39

what is the word for anything in between the substrates and products?

Answer 39

intermediates. (it is called this because it is temporary)

Question 40

what happens in pathways of metabolism? what is end-product/feedback inhibition?

Answer 40

end product/feedback inhibition is when there is too much production of product, so we inhibit the enzyme in the beginning.
ex: the high levels of Z (end product) will inhibit enzyme #1 at the very beginning of the pathway.