General Enzyme Knowledge
This location is where substrates bind to enzymes
What is the active site?
What is activation energy?
What is anabolic?
What is an active site?
This factor describes how acidic/basic an environment is, and can affect enzyme activity.
What is pH?
These types of enzymes function inside the cell, attached to membranes.
What is intracellular immobile?
This high-energy, extremely unstable coupling of an enzyme/substrate only exists for a split second, and has the most amount of energy relative to the rest of the reaction.
What is a transition state (or an enzyme-substrate complex)?
This word describes many metabolic reactions - the products produced in one reaction become the reactants in another reaction, forming cycles.
What is interdependent?
This is the reason that your body has controls in place to regulate how much enzyme activity is occuring.
What is conserving energy?
Enzyme and substrates must _______ to react, meaning there has to be molecular motion.
What is collide?
These are the organelles, in order, that an extracellular enzymes visits before being transported outside the cell and reaching its destination
What is rough ER/ribosome, golgi body, and cell membrane?
Anabolic reactions will feel ______ to the touch because the amount of heat has ________ from reactants to products
What is cold & increased
This part of metabolism is best illustrated by cellular respiration and lipolysis.
What is catabolism?
Cytochrome oxidase is an enzyme involved in the production of ATP. It binds to the substrate, cytochrome, during one of the steps. ATP acts as its inhibitor, even though ATP is not similar in shape at all to cytochrome. This is an example of what kind of inhibition?
What is noncompetitive?
This factor increases enzyme activity up to a point, and then begins to level off as the enzymes become saturated.
What is substrate concentration?
IB STYLE:
A) Describe how the "induced fit model" differs from the "lock and key model" of enzymes [2].
1 mark - describes lock and key model as "substrates fit perfectly into enzymes"
1 mark - describes induced fit model as enzymes changing shape slightly to mold around substrates
IB STYLE:
A student asks, "If all reactions require energy to get started, aren't they all endothermic?"
Respond to their question. [3]
1 mark - identifies that the answer is "no"
1 mark - description of activation energy as different from overall reaction energy (H)
1 mark - identification that while activation energy is needed to start, endothermic reactions are defined by an increase in energy from reactants to products, not by what happens in between
Describe what is meant by the phrase "mammal metabolism is intentionally inefficient". [3]
1 mark - description of "inefficient" meaning "produces a lot of waste heat"
1 mark - identifies that this waste heat results from exothermic metabolic processes
1 mark - describes how mammals use this waste heat to warm their bodies and maintain optimal internal temperatures
IB STYLE:
Your body sometimes controls enzymes by physically "turning off" certain genes. Explain why this works as a control mechanism. [2]
1 mark - identifies that genes code for proteins AND that enzymes are proteins
1 mark - explains that turning off the genes will cease production of the proteins making up the enzyme
IB STYLE:
The enzyme lipase operates at an optimal temperature of about 38o C. Draw the expected results of an experiment measuring enzyme activity as a reaction is heated from 0-100o C. [2]
1 mark - graph has axis labels (temperature on x and enzyme activity on y)
1 mark - graph is bell curve-shaped with the peak around 38o C.
IB STYLE:
During synthesis of the lactase enzyme, a translation error was made, causing three amino acids to be swapped out incorrectly.
A) Describe how this change would affect the breakdown of lactose. [3]
1 mark - a change in the amino acid sequence causes a change in the folding pattern and therefore shape of the enzyme
1 mark - a change in the shape of the enzyme means the active site's shape changes, and lactose may not be able to bind
1 mark - therefore, lactose would break down slower due to the absence of a catalyst
IB STYLE:
A) Catalase breaks down H2O2 into O2 and H2. Draw and label a reaction coordinate diagram for the uncatalyzed reaction [3].
B) Draw a dotted line on the same diagram to represent the pathway of the catalyzed reaction [2].
1 mark - reaction shows a "hill" shape in the middle for activation energy
1 mark - diagram shows the reactants higher than the products
B) 1 mark - dotted line places the overall activation energy below the uncatalyzed line
1 mark - dotted line does not alter the original placement of the product/reactants
IB STYLE:
When snakes eat food, they eat a massive meal all at once. They often wait until their surroundings temperature is high to hunt and eat food, even though the breakdown of food is generally a exothermic process. Describe the metabolic reason for this behavior. [3]
1 mark - discusses that even exothermic reactions require activation energy to start
1 mark - identifies that snakes are endotherms (cold-blooded), and therefore do not produce their own body heat, meaning they require heat input from their surroundings to warm themselves
1 mark - connects the energy cost of metabolism to the danger of digesting a large meal with low energy
IB STYLE:
A particular enzyme, Hexokinase, catalyzes the first step of glycolysis by breaking down glucose into glucose-6-phosphate. Glucose-6-phosphate is capable of binding to the active site of Hexokinase, preventing it from catalyzing more reactions.
A) State what kind of inhibitor is glucose-6-phosphate acting as.
B) Give two reasons why this type of inhibition using the product of the catalyzed reaction is more energy efficient for cells compared to other types of enzyme control
A) 1 mark - identifies this as "competitive inhibition"
B) ANY TWO OF THE FOLLOWING
1 mark - identifies that noncompetitive inhibition requires production of an entirely new molecule, so using the product that is already there is more efficient
1 mark - identifies that gene control requires extra molecules/DNA editing, which is also energetically expensive compared to using a product
1 mark - discusses that using the product removes the need to transport other molecules to the enzyme to break it down/disable it
During an enzyme lab, students measured the activity of catalase by mixing potatoes (which contain catalase) in different H2O2 solutions.
One group of students were struggling to see any bubbles at all, and concluded their reaction had failed due to some error. Suggest and explain three plausible reasons that their reaction did not work. [3]
ANY THREE OF THE FOLLOWING:
1 mark - the students heated the potatoes too high, or left them in a warm place THEREFORE the catalase was denatured
1 mark - the reaction was not warm enough THEREFORE collisions did not occur at a high enough rate
1 mark - there was not sufficient concentrations of H2O2 in their solution THEREFORE collisions did not occur at a high enough rate
1 mark - the potatoes were not peeled/crushed, THEREFORE the catalase was not exposed to the substrate
1 mark - that particular potato had a genetic mutation causing catalase to not be present at all