Chapter 8 - Metabolism

Question 1

What is metabolism in simple terms?

Answer 1

The sum of all the chemical reactions that occured in your body;

Question 2

Which laws does the concept of metabolism follow?

Answer 2

The laws of Thermodynamics

Question 3

What do most metabolic reaction involve in terms of reactants and products? What do we call the process?

Answer 3

It starts with a molecule which is catalyzed each time in a series of steps resulting in an end product

Metabolic pathways

A to B to C = D

Question 4

Name the major subclasses of metabolic pathways

Answer 4

There are two major types of metabolic pathways -
Anabolic (build up)
Catabolic (break down)

Question 5

What are catabolic pathways?

Answer 5

In these pathways, the molecules are broken down structurally to release energy
(the energy is the end product)

Question 6

What are anabolic pathways?

Answer 6

In these pathways, smaller molecules are joint into a bigger structure by consuming energy
(the bigger structure = end product)

Question 7

Is cellular respiration anabolic or catabolic? Why?

Answer 7

Catabolic, because cellular respiration involves breaking down of glucose for energy

Question 8

Give one example of an anabolic pathway

Answer 8

Joining amino acids to make up different proteins

Protein sythesis

Question 9

Describe the laws of Thermodynamics

Answer 9

1. Energy cannot be created or destroyed therefore, it’s always transformed (also called Conservation of Energy)
2. The universe’s entropy is increasing
   3.

Question 10

What is entropy? Can events ever violate the law of entropy?

Answer 10

Entropy refers to disorder in the environment from a system. In the universe, we (our bodies) are the system and our actions cosntantly cause disorder in the environment due to the releasing heat and energy..
No, no events can ever violate the entropy.

Question 11

What is positive entropy? What is negative entropy?

Answer 11

Positive entropy = more disorder
Negative entropy = less disorder

Question 12

What is free energy?

Answer 12

Free energy refers to the energy that can catalyze reactions without energy extraction

Question 13

What is ΔG? Explain the context in which it’s used.

Answer 13

ΔG= Gibbs free energy
The unit ΔG is used as a currency of free energy
(to calculate the amount of energy used)

Question 14

Is lower ΔG favorable or unfavorable? What does lower G mean for a chemical reaction?

Answer 14

Favorable in a reaction because lower ΔG means lower amount of free energy needed for a reaction. So there would be lower chances of having to consume energy to carry out a reaction
As a result, the chemical reaction will be exergonic and energy is only used.

Question 15

Is higher/positive ΔG favorable or unfavorable?

Answer 15

Unfavorable because the chemical reaction would require energy extraction.
As a result, the reaction is endergonic and energy is consumed for it to be carried out.

Question 16

Are free energy reactions typically +ΔG or -ΔG

Answer 16

Typically +ΔG because some reactions need energy halfway through the process

Question 17

Where does the energy come from in a +ΔG reaction?

Answer 17

It comes from the molecule ATP, since ATP contains three phosphate groups, breaking one of them off releases a good amount of energy that fuels the reaction

Question 18

does ATP give permanent energy fuel to a chemical reaction?

Answer 18

No, instead ATP does energy coupling. Energy coupling is a process where energy produced by one reaction drives another. So when ATP is broken down for energy to create a new product, ATP becomes ADP + P (REACTION 1). When the product is made, H2O is released which bonds ADP+P into ATP back again making ATP (REACTION 2) reusable.

Question 19

How much energy does ATP have?

Answer 19

7.3kcal/mol

Question 20

is ATP a currency of energy?

Answer 20

Yes

Question 21

What is the process of ATP transferring its phosphate to another molecule in an endergonic reaction called?

Answer 21

Phosphorylated intermediate

Question 22

Is phosphoylation intermediate always the process that ATP uses to help fuel energy?

Answer 22

No, not always. ATP has other methods of fueling energy too.

Question 23

If ATP fuels a reaction with energy, what does an enzyme do then?

Answer 23

Enzymes don’t fuel energy, they speed up the time it takes for a chemical reaction

Question 24

What kind of protein is an enzyme? (think function wise)

Answer 24

Enzyme is a catalytic protein, it acts as a catalyst in a chemical reaction

Question 25

How exactly does an enzyme help speed up a reaction?

Answer 25

In a reaction, there’s an amount of free energy (called activation energy) that reactants must use in order to jumpstart the process. Enzyme lowers the activation energy so that the reactants can use less amount of free energy which results into a faster reaction time for reactants to turn into products.

Question 26

Do enzymes actually influence the free energy of reactants while catalyzing?

Answer 26

Yes, that’s how enzymes speed up reactions!

Question 27

Do enzymes use their entire structure to catalyze a reactants’ reaction time?

Answer 27

No, the reactants (substrate) actually only binds to a specific region of the enzyme called the active site.

Question 28

How do substrates (reactants) actually know to bind to an active site?

Answer 28

Active sites are regions where chemical reactions actually occur so all reactants bond there structurally.

Question 29

Does the enzyme and substrate fit together like lock and key? (aka do they perfectly fit like two pieces of puzzles)

What is the bonding mechanism between them called?

Answer 29

No, the active site of an enzyme is similarly shaped however it’s not EXACT to the substrate. When substrate bonds to the active site, the enzyme closes on it to fit more perfectly by moving it structure closer.

This is called **Induced fit **

Question 30

What is the name of the relationship between reactants and enzymes called when it binds?

Answer 30

Substrate-enzyme complex

Substrate = reactants

Question 31

When a substrate (reactant) binds to an enzyme, what does the enzyme actually do to reduce substrate’s activation energy?

Answer 31

The enzyme can do multiple things:
1. It can stretch the substrate’s bonds so the bonds needed to break for reactions easily break
2. orients susbtrates in correct position so reaction can occur
3. makes environment more suitable for substrate so it bonds (if substrates works in an acidic region, enzyme provides acidic molecules)
4. covalently bonds to the substrate for reactions to occur

Question 32

Do enzymes bond covalently with reactants when they perform an induced fit on substrates?

Answer 32

No, they bond through non covalent bonds such as Van Der Waals (electrostatistically) or hydrogen bonds etc.

Question 33

Are enzymes’ performances affected/influenced by any factors?

Answer 33

Yes mainly by two factors:
pH and temperature

Question 34

do enzymes have optimal conditions in which it can perform the best?

Answer 34

Yes, each enzyme in an organism has its own optimal pH and temperature under which it works best

Question 35

Do enzymes’ optimal conditions change over a long period of time?

Answer 35

Yes, enzymes’ optimal conditions under which it works best gradually change over a long period of time. This is called enzyme evolution.

Question 36

How does enzyme evolution occur exactly?

Answer 36

Enzyme evolution occurs when a specfic enzyme’s novel form (similar but not exact amino acid sequence) is preffered in a new environment. This leads to synthesis of the new version of the specific enzyme over time which eventually leads to evolution.

Question 37

during the process of enzyme evolution, does the body produce a new type of enzyme that would be favored?

Answer 37

No, enzymes exist in homologous pairs, also known as homologous enzymes. They have slightly different amino acid sequences but perform the same function. During evolution, one homologous enzyme is preffered over the other which eventually leads to more synthesis of that particular enzyme.

Question 38

what influences an enzyme to evolve?

Answer 38

change in environment of an organism

Question 39

Are cofactors enzymes? Are they organic or inorganic compounds?

Answer 39

Cofactors are not enzymes because they aren’t made up of proteins (non-protein structures).
They can be either organic or inorganic compounds.

Question 40

What is the relationship between cofactors and enzymes?

Answer 40

Cofactors are nonprotein structures that help enzymes (that need prosthetic groups) perform catalyzation with maximum efficiency and maintain protein structure.
This is done by cofactors binding to enzymes.

Question 41

what’s the difference between coenzymes and cofactors

Answer 41

coenzymes are cofactors that are organic compounds

Question 42

How are enzymes regulated? Name the most common method

Answer 42

There are a few methods but inhibiting them is the most common one.

Question 43

There are ____ types of major inhibitors

Answer 43

2

Question 44

List the most common types of inhibitors

Answer 44

1. Competitive inhibitors
2. Noncompetitive inhibitors

Question 45

What does inhibiting do to enzymes?

Answer 45

They inhibit enzymes from binding with the substrates to stop enzyme activities

Question 46

How does competitive inhibiting stop enzyme activity

Answer 46

An inhibitor binds to the active site which prevents the subtrates from binding; so the inhibitor directly competes with the substrate

Question 47

What are some examples of cofactors

Answer 47

Vitamins and ATP

Question 47

How does noncompetitive binding stop enzyme activity?

Answer 47

The inhibitors DONT bind to their active sites and instead bind to another region of the enzyme. This causes the enzyme to induce fit to the inhibitor and change its shape in a way that makes the substrate unable to bind to the enzyme.
This is more indirect.

Question 48

What are some examples of external inhibitors? (not natural to body)

Answer 48

poison, toxins, drugs
All of these inhibit enzyme functions

Question 49

What are other ways or regulating an enzyme?

Answer 49

There are 4 major methods other than inhibiting that regulates enzyme activity:
1. switching the on/off gene that encodes enzyme (stops enzyme production)
2. regulating enzyme activity through allosteric or cooperativity
3. feedback regulation (positive/negative)
4. enzyme localization

Question 50

What is the purpose of regulating enzymes?

Answer 50

It’s to control metabolism in the body. meaning, to start and stop processes in the body, it’s important to regulate enzymes

Question 51

How does the body stop/start enzyme processes? Describe the methods.

Answer 51

Through allosteric regulation or cooperative regulation.
In allosteric regulation - noncompetitive/competitive binding
cooperative - the regulatory molecule is the substrate

Question 52

What is a regulatoryu mechanism that works as a loop? Explain the mechanism.

Answer 52

Feedback regulation- in this regulation method, the cell’s process/pathway is blocked.
negative feeback - The end product of the pathway blocks the enzyme activity in order to stop over production and wastage of chemical resources.

positive feedback - the end products of the pathway speeds up the metabolic pathway

Question 53

How does enzyme localization work in regulating enzymes?

Answer 53

Enzyme localization is when substrates’ flow into enzyme locations are blocked by membranes or other processes. As a result, enzyme regions remain empty and substrates are only allowed in when needed by the cell. This controls overproduction and regulates enzymatic activity.