chapter 6 - an introduction to metabolism + practical lab 2

what are enzymes? which type of macromolecule are enzymes usually?

biological catalysts that speed up biological reactions. enzymes are usually proteins.

how do enzymes work?

they lower the activation energy (Ea), which is the initial energy required to start a chemical reaction

a __ is the substance(s) on which the enzyme acts. the substance(s) resulting from this reaction are known as __.

reactants or substrate, products

why are enzymes so important?

in order for reactions within the cell to occur at the necessary rate, the amount of energy required would cause the cell to boil. because of this, we have enzymes, which lower the amount of energy required for the reaction to occur (to increase rate) without requiring so much heat

do enzymes..?

1. change the equilibrium concentrations for a reaction?

2. affect free energy changes? (🔺G)

3. emerge from reactions altered, and cannot be reused?

4. react with specific substrates based on the specific enzyme?

1. no

2. no

3. no, enzymes emerge from reactions unaltered and can be reused again and again

4. yes, specific enzymes react with specific substrates

order the following steps of the enzyme process

a) products are released

b) substrates bind to the active site

c) active site is now available, enzyme is unaltered and can now be reused

d) active site changes shape very slightly, enfolding the substrate (induced fit)

e) substrates are held in the active site, which lowers the activation energy, increasing reaction rate

f) substrates/reactants are converted to products

1. b) substrates bind to the active site

2. d) active site changes shape very slightly, enfolding the substrate (induced fit)

3. e) substrates are held in the active site, which lowers the activation energy, increasing reaction rate

4. f) substrates/reactants are converted to products

5. a) products are released

6. c) active site is now available, enzyme is unaltered and can now be reused

what analogy is used to describe the relationship between enzyme and substrate? why?

an analogy of a lock and key is used to explain the relationship between an enzyme and its substrate. this is because the active site of an enzyme is complementary to only one type of substrate. when the lock and the key connect, it represents the enzyme-substrate complex

what is the enzyme-substrate complex? (2)

• the enzyme and substrate join briefly and form a complex.

• one the enzyme-substrate complex has formed, chemical bonds are made or broken between atoms of the substrate, resulting in the formation of products.

what is the point of an enzyme having an active site?

the shape of the active site makes it possible for an enzyme to interact with only a specific substrate and no other

name the enzyme, substrate and product for each point

1. shortened amino acid chain, individual amino acids, trypsin (in small intestine)

2. benzoquinone, catechol oxidase, catechol

3. fructose and glucose, sucrose, sucrase

4. shortened amino acid chains, pepsin (in stomach), protein macromolecule

1. substrate, product, enzyme

2. product, enzyme, substrate

3. product, substrate, enzyme

4. product, enzyme, substrate

1. what are activators?

2. what are cofactors?

3. what are coenzymes?

4. would metal ions be coenzymes or cofactors?

1. activators are chemicals that must bind for the enzyme to be active

2. non-protein substances that bind to the active site of the enzyme and are essential for the enzyme’s functioning

3. organic cofactors

4. metal ions are sometimes cofactors

what are inhibitors? provide 4 examples of inhibitory substances. what are the two types of inhibitors?

• inhibitors are chemicals that interfere with enzyme activity

• pesticides, toxins, poisons and antibiotics can all inhibit enzyme activity

• the two types of inhibitors are competitive and non competitive

1. what are the two ways of measuring enzyme activity?

2. how did we measure enzyme activity in the lab?

1. by determining rate of disappearance of the substrate or by determining the rate of product appearance

2. we used a spectrophotometer to measure absorbency values, because our product benzoquinone is pigmented, allowing us to measure product appearance

competitive inhibition (3)

• a molecule structurally similar to the substrate for a certain reaction competes with the substrate for the enzyme’s active site

• enzyme is occupied and is unavailable to the substrate as a result

• can be reversed by adding additional substrate to increase substrate concentration (increases likelihood of the substrate bonding to the enzyme’s active site over the inhibitor)

non-competitive inhibition (2)

• inhibitors can block the active site or bind somewhere else on the enzyme that changes the shape of the active site so that it can no longer fit the substrate

• non-competitive inhibition is irreversible

is PTC a competitive or non competitive inhibitor of catechol oxidase? how do we know?

PTC is a non competitive inhibitor of catechol oxidase. we know this because the absorbency values did not change when we added additional substrate, the inhibition was irreversible. if the absorbency values changed after adding more substrate, the inhibitor would be competitive.

what are some factors that can affect an enzymes activity? what is it called when an enzyme becomes inactive?

some factors that can affect enzyme activity are temperature and pH. if factors like these are too far beyond the optimum range the enzyme operates in, it can be denatured (inactive)

what is metabolism?

the totality of an organism’s chemical reaction

metabolic pathways (2), and the 2 types of metabolic pathways

• begins with a specific molecule and ends with a product

• each step is catalyzed by a specific enzyme

• two types of metabolic pathways are catabolic and anabolic

catabolic pathways +1 example

break complex molecules into simpler molecules, ex. cellular respiration

anabolic pathways +1 example

consume energy to build complex molecules from simpler ones, ex. protein synthesis

state the first law of thermodynamics

the energy of the universe is constant- it can be transferred or change forms but cannot be destroyed

state the second law of thermodynamics

during any energy transfer/transformation of energy, some energy is unusable and is lost to the environment, often as heat

1. what does ATP stand for?

2. what are the three types of cellular work powered by ATP?

3. what is ATP hydrolyzed into?

4. how is ATP reused?

1. adenosine triphosphate

2. transport, chemical and mechanical

3. ADP (adenosine diphosphate) and a phosphate group

4. a phosphate group is re-attached to ADP, forming ATP