C1.1 enzymes and metabolism

Question 1

What is a catalyst?

Answer 1

A substance that increase the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy, without being consumed in the reaction

Question 2

what are organic catalysts known as?

Answer 2

enzymes -> they are organic catalysts, usually proteins, that speed up the rate of biochemical reactions by providing an alternative reaction pathway with a lower activation energy, without being consumed in the reaction

Question 3

compare and contrast catalysts and enzymes

Answer 3

• all enzymes are catalysts, but **not all ** catalysts are enzymes
  - Differences:
  enzymes = naturally occurring + catalysts can be organic/inorganic,
  enzymes = complex proteins + catalystis = simple,
  catalysts = non specific + enzymes = highly specific,
  enzymes = biological/metabolic reactions + catalysts = chemical/industrial reactions
  - similarities: both increase rate of reactions, neither is consumed in the reaction, can be inhibited, both provide an alternative reaction pathway, do not alter the overall chemical equilibrium

Question 4

what is metabolism?

Answer 4

this includes all the chemical reaction that occur in an organism. These reactions may be independent of one another or interact with other reactions. each chemical reaction is controlled by a specific enzyme.

Question 5

What do all chemical reactions require?

Answer 5

- reactants -> are the substances that participate in a reaction
- products -> are the substances that are formed
- A + B (reactants) -> C + D (products)

Question 6

what are anabolic reactions?

Answer 6

this is a **metabolic ** reaction that uses energy to build complex organic molecules from simpler organic molecules. This process is called an anabolism
Traits
- require energy input to occur
- ex-> photosynthesis, protein synthesis, and glycogen formation
- build macromolecules (and release water) from monomers by condensation reactions

Question 7

what are catabolic reactions?

Answer 7

These are metabolic reactions that break down complex organic molecules, wit the release of energy. This process is called a catabolism .
Traits
- release energy as they occur
- ex-> digestion and the oxidation of substrates in respiration
- break down macromolecules into monomers by hydrolysis (the splitting of molecules by adding water)

Question 8

What are the different forms of energy?

Answer 8

• kinetic energy
• potential energy
• chemical energy
• thermal energy

Question 9

What is kinetic energy?

Answer 9

energy of motion, including movement of molecules within objects

Question 10

What is potential energy?

Answer 10

This is stored energy or energy in a form that is not being used at a point of time

Question 11

What is chemical energy?

Answer 11

A form of potential energy that is available for release when a chemical reaction occurs. All orgnanisms maintain their structure and function through chemical energy.

Question 12

What unit is used to measure heat in biology?

Answer 12

Kilocalorie (kcal)
- 1 kcal = 1000 calories

Question 13

What are some functions of ATP?

Answer 13

It is the energy currency of a cell
- supplying the energy needed to synthesize large molecules called macromolecules
- supplying the energy necessary for mechanical work, such as muscle action, chromosome movement and cilia or flagellum motion
- providing energy to move substances across the cell membrane, such as the sodium-potassium pump

Question 14

What are rybozymes?

Answer 14

is a ribonucleic acid (RNA) molecule that acts as an organic catalyst. Ribozymes are often able to catalyse their own assembly.

Question 15

what are enzymes made of?

Answer 15

Almost all enzymes are proteins, made of long chains of amino acids folded into a specific 3D shape (globular)

Question 16

What is the shape of an enzyme called?

Answer 16

Enzymes have a globular shape, which is a specific 3D structure

Question 17

What is the active site of an enzyme?

Answer 17

the active site is a specific region of the enzyme that matches the shape of the substrate and allows catalysis to occur

Question 18

What determines the shape oof the active site?

Answer 18

the shape is determined by **a few ** amino acids within the enzyme and the overall 3D structure of the protein

Question 19

What happens if the enzyme’s shape changes?

Answer 19

the enzyme becomes denatured and can no longer function as a catalyst, this affects the rate at which the enzyme works
**denaturation **-> is the structural change in a protein (such as an enzyme) that results in the loss of its biological properties, usually caused by factors such as extreme temperature of pH

Question 20

What causes enzyme denaturation?

Answer 20

changes in condition (eg, temperature and pH) that affect the chemical bonds between amino acids

Question 21

What is the lock-and-key model, and what has it changed into?

Answer 21

This model proposed by Emil Fisher has been modified into what is now known as the induced-fit model.
- is a theory of enzyme action that proposed that the enzyme’s active site has a specific shape that exactly matches the shape of its substrate, ‘like a key fitting into a lock’. Only the correctly shaped substrate can bind to the active site and be converted into product

Question 22

What is the induced-fit model?

Answer 22

Theory of enzyme action which proposes that the enzyme’s active site is flexible and changes shape slightly to fit the substrate when it binds. This improves the fit between enzyme and substrate and enhances the enzyme’s ability to catalyze the reaction.

Question 23

compare and contrast induced-fit model and lock-in-key model

Answer 23

- Lock-and-key model
-the enzymes active site has a fixed, rigid shape
- the substrate must fit exactly, like a key in a lock
- explains specifity through perfect shape matching
- the enzyme does not change shape when binding the substrate
- binding is passive, the active site is already perfectly shaped
- Induced-fit model
- the enzyme’s active site is flexible
- the substrate does not need to fit perfectly at first
- the enzyme changes shape slightly to fit the substrate better
- explains specifity through structural adjustment
- binding is active, the enzyme helps facilitate the reaction more effectively

Question 24

What is activation energy?

Answer 24

is the minimum energy required to destabilize the bonds of a substrate so that a chemical reaction can occur

Question 25

What do enzymes do to activation energy?

Answer 25

Enzymes **lower the activation energy** needed for a reaction to occur, making reactions happen more easily and quickly

Question 26

Do enzymes provide energy for a reaction?

Answer 26

**NO**, enzymes do not supply energy. They just reduce the amount of energy needed to start the reaction

Question 27

Are enzymes **reactants** in a reaction?

Answer 27

**NO**, enzymes are not reactants and are not consumed in the reaction. They can be reused many times

Question 28

What are two ways to **overcome the activation energy barrier**?

Answer 28

1. Increase energy of reactants (eg by heating) 2. lower the activation energy (eg using a catalyst or enzyme)

Question 29

Why are enzymes **essential** in living systems?

Answer 29

enzymes allow reactions to occur at **lower temperatures**, which protects cells from damage caused by heat

Question 30

How do catalysts affect reversible reactions?

Answer 30

catalysts **lower the activation energy in both directions**, increasing the rate of **both forward and reverse ** reactions

Question 31

Do enzymes change the position of equilibrium in a reaction?

Answer 31

**NO**, enzymes do not alter the equilibrium, they only help the system reach it **faster**

Question 32

What is the difference between **exergonic** and **endergonic** reactions?

Answer 32

- **exergonic** reactions release energy; products have *less energy* than reactants because energy has been given off (common in catabolic processes) - **endergonic** reactions absorb energy; products have *more energy * than reactants because energy is taken in during the reaction. (Common in anabolic processes) -both of these reactions release energy when they occur.

Question 33

why is movement important in enzyme action and control of chemical reactions?

Answer 33

In order for substrates to react, they need to collide and they need to find the enzyme's active site. Molecules therefore need enough energy to move and collide.

Question 34

Why are actives sites important in enzyme action and control of chemical reactions?

Answer 34

Active sites are important because the active site must join with the substrate based on shape.

Question 35

Why are enzymes or substrates often immobilized in membranes?

Answer 35

immobilizing the enzyme or substrate in a membrane allows a more efficient joining of the substrate and active site, helping reactions happen more effectively

Question 36

summarize the mechanism/steps of enzyme action

Answer 36

1. the surface of the substrate makes contact with the active site of the enzyme 2. the enzyme and substrate change change shape to provide a fit 3. a temporary complex called the enzyme-substrate complex forms 4. the activation energy is lowered, and the substrate is altered by the reaarangement of the existing atoms 5. the transformed substrate, the product, is released from the active site 6. the unchanged enzyme is then free to combine with other substrate molecules Enzyme action can also be summarized by the following equation: E + S -> ES -> E + P

Question 37

How does **Temperature** affect enzyme activity?

Answer 37

As temperature increases, molecules move faster due to more kinetic energy, leading to more frequent and energetic collisions, which increases the rate of enzyme reactions. However, at high temperatures, the enzyme may lose its 3D shape as bonds break (denaturation). Denaturation can be temporaty if conditions return to norma;, but becomes permanent if the enzyme cannot regain its original shape

Question 38

How does pH affect enzyme activity and what happens when pH changes too much?

Answer 38

The **charged areas** of a substrate must match the charged amino acids in the enzyme's active site for proper binding. If the pH becomes too acidic or too basic, these ions can interfere with charge matching by binding to opposite charges on the enzyme or substrate. This prevents proper interaction and reduces enzyme efficiency. If the pH changes too much, bonds withint the enzyme break, causing the enzyme to lose its shape and become denatured

Question 39

What is the **collision theory**?

Answer 39

Collision theory states that for a reaction to occur, reactant particles (like enzymes and substrates) must collide with sufficient energy and correct orientation. Enzymes help by lowering activation energy and increasing the likelihood of successful collisions.

Question 41

How does substrate concentration affect enzyme activity?

Answer 41

as substrate concentration increases, the **rate of reaction increases** because there are more collisions between substrates and enzymes (explained by collision theory). However, the rate reaches a maximum when all active sites are occupied. Beyond this point, adding more substrate will not increase the rate further.

Question 42

What are intracellular enzymes?

Answer 42

- enzymes that occur within a cell - glycolysis and the krebs cycle are examples of reactions catalysed by intracellular enzymes. - Glycolysis takes place in the cytoplasm of the cell. The krebs cycle takes place in the matrix of the mitochondria

Question 43

What are extracellular enzymes?

Answer 43

- Enzymes that occur outside a cell - chemical digestion within the gut/digestive system is an example of reactions catalyzed by extracellular enzymes

Question 44

What are multienzyme complexes and what is their role in cells?

Answer 44

Multienzyme complexes are groups of enzymes that work together to catalyze essential life reactions in incremental steps. Some enzymes float freely in the cell, while others are part of organelles or membranes. These complexes imrpove efficiency by carrying out sequential reactions inside or outside the cell

Question 46

what are metabolic (or biochemical) pathways?

Answer 46

they are sequences of enzyme-catalyzed reactions where the product of one reaction becomes the substrate for the next

Question 47

What is a linear metabolic pathway?

Answer 47

A pathway where reactions occur in a straight chain from initial substrate to a **different final product**

Question 48

What is a cyclic metabolic pathway?

Answer 48

A pathway that starts and ends with the same compound, repeating through a cycle of intermediate reactions

Question 49

What does each arrow in a metabolic pathway represent?

Answer 49

A specific enzyme-catalyzed reaction converting one substrate to the next product

Question 50

Why are metabolic pathways rarely simple in real cells?

Answer 50

they are often branched and interconnected, allowing interactions between different pathways

Question 51

Why is regulation of metabolic pathways important?

Answer 51

It allows fine control of energy use and release, preventing too much energy from being used or released at once, which could harm the cell

Question 52

What is glycolysis and what kind of pathway is it?

Answer 52

Glycolysis is a linear metabolic pathway in cellular respiration that starts with glucose and produces 3-carbon compounds

Question 53

What is the krebs cycle and what kind of pathway is it?

Answer 53

the krebs cycle is a cyclic metabolic pathway in cellular respiration that begins and ends with the same 4-carbon compound

Question 54

What is the calvin cycle and where does it occur?

Answer 54

The calvin cycle is a cyclic metabolic pathway in photosynthesis that begins and ends with the same 5-carbon compound

Question 55

When does enzyme inhibition occur?

Answer 55

occurs when a molecule, an **inhibitor**binds to an enzyme and decreases the enzyme's activity by altering the active site

Question 56

What is **non-competitive inhibition**?

Answer 56

This involves an inhibitor that does not compete for the enzyme's activ site. in this case, the inhibitor interacts with another site on the enzyme. Non-competitive inhibition is also referred to as **allosteric inhibition**, and the site the inhibitor binds to is called the **allosteric site**, this is *not* a active site.

Question 57

What does binding at the **allosteric site** cause?

Answer 57

Causes a change in the shapeof the enzyme's active site, making it non-functional. Normally, the effects of allosteric inhibitors are reversibale and the enzyme is not damaged. These inhibiotrs are not influence by the concentration of the substrate

Question 58

What is **competitive inhibition**?

Answer 58

here, a molecule (**competitive inhibitor**) competes directly with the usual substrate for the active site. If the competitive inhibitor occupies the active site instead of the substrate, the rate of the chemical reaction will be decreased. The competitive inhibitor must have a structure similar to the substrate in order to function in this way. This is affected by substrate concenctration and can be overcome by increasing the substrate concentration. Increasing substrate concentration allows more substrate molecules to bind with the active sites as the become available, and the chemical reaction may proceed more rapidly.

Question 59

Explain end-product inhibition | this is a regulatory process in metabolism

Answer 59

- When too much end product builds up, it binds to enzyme 1. - This prevents enzyme 1 from working, stopping the entire pathway at the start. - As a result, no more intermediate A, B, or product are made. - This is called negative feedback because the product of the pathway inhibits the pathway itself.

Question 60

Is feeback inhibition harmful to the cell? Why or why not?

Answer 60

NO, feedback inhibition is beneficial. It prevents the overproduction of a final product by temporarily shutting down the metabolic pathway when enough product is present. This helps the cell save energy, conserve resources, and maintain balance (**homeostasis)** the inhibition is reversible, when product levels drop, the pathway restarts.

Question 61

What is mechanism-based inhibition?

Answer 61

it's a form of inhibition where a molecule irreversibly binds to an active site of an enzyme, causing permanent inactivation through chemical changes at that site

Question 62

How does penicillin work as a mechanism-based inhibitor?

Answer 62

Penicillin irreversibly binds to the bacterial enzyme **transpeptidase**, which is needed to build bacterial cell walls. This inactivates the enzyme and prevents cell wall formation, leading to bacterial death

Question 63

Why does penicillin not affect human cells?

Answer 63

because human cells do not have cell walls, so they do not use transpeptidase, the enzyme that penicillin targets

Question 64

How do some bacteria become resistant to penicillin?

Answer 64

1. Some produce an enzyme called **penicillinase**, which breaks down penicillin 2. others have **mutated transpeptidase enzymes**, so penicillin can no longer bind to the active site

Question 65

How are scientiest addressing penicillin resistance?

Answer 65

by modigying the structure of penicillin to avoid breakdown by penicillinase, and by researching ways to restore binding to mutated transpeptidase enzymes.