C1.1 Enzymes Flashcards
Define catalyst
A catalyst is a substance that speeds up a reaction without being used up or altered
state the role of enzymes in the chemical reactions on which life is based
Enzymes speed up chemical reactions that would normally be too slow to happen without them
State that enzymes speed up chemical reactions _____, so can be _____
enzymes speed up chemical reactions without being altered, so can be reused
define metabolism
- Metabolism is the complex network of interdependent and interacting chemical reactions occurring in living organisms
- Most of these reactions are enzyme controlled
- These reactions can often have multiple steps and be quite complex
define specificity (in relation to enzyme structure and function)
Each enzyme will only catalyze one specific reaction or one type of reaction due to the structure and properties of its active site
Outline how control of metabolism is regulated by enzymes
By making more or less of an enzyme, cells are able to control the rate of reaction
There are also mechanisms that temporarily stop enzymes when they aren’t needed
Contrast anabolic and catabolic reactions
Anabolic reactions build up molecules and require energy
Catabolic reactions break down molecules and release energy
(cats break stuff! ants build stuff!)
List three examples of anabolic processes
- Synthesis of complex carbohydrates
- DNA synthesis
- Protein synthesis
List three examples of catabolic processes
- Digestion of complex carbon compounds
- Digestion of food
- Cell respiration
Outline properties of globular proteins
Globular proteins have very specific confirmations and structures
globular proteins will have tertiary and quaternary structure
- enzymes are globular proteins
(ex. enzymes have a specifically shaped active site – allowing them to bind with only certain substrates)
Explain the relationship between enzyme structure and enzyme specificity, including the structure and function of the active site
- Enzymes = large molecules, but only the active site is involved in catalysis
- Substrates = the reacting molecules
- Substrates and enzymes move and randomly collide
- Many molecules can enter the active site, but if they are not the right shape or alignment, no reaction will happen.
- If the shape and alignment are correct: the substrate will BIND to the active site, forming an enzyme-substrate complex
- Enzymes have specificity (they can catalyse only one type of reaction because an enzyme can only react with a specific substrate molecule)
Outline the stages of enzyme catalysis of a chemical reaction
-The substrate gets closer to the enzyme by random collisions
-The chemical properties of the active site attracts the subsrate
-The substrate binds to the active site
-The active site and substrate change shape to fit perfectly
-If a second substrate is present, it binds to another part of the active site
-The enzyme makes it easier for the substrate to make or break bonds, forming products
-The products detach
Describe the induced fit model of enzyme binding
The enzyme and substrates alter their bond lengths and angles to fit together perfectly
Explain the role of random collisions in the binding of the substrate with the enzyme active site
The substrate will get closer to an enzyme by random molecular motion and collisions before it is attracted by the active site
Compare enzyme substrate movement involved in reactions that occur in the cytoplasm, with large substrates and with immobilized enzymes
The substrate moves to the enzyme since it tends to be smaller, or if the enzyme is immobilized. If the substrate is large, the enzyme moves to the substrate.
Discuss variation in the specificity of different enzymes
The specificity of an enzyme depends on the shape of the enzyme formed by the relatively weak bonds between amino acids.
Some enzymes are very specific, only accepting one substrate, while some accept a group of substrate, like hexoses.
Define denaturation
Denaturation is when a protein loses its structure when its intermolecular bonds are broken due to extreme heat or pH
Outline the causes and effects of denaturation on enzyme structure and function
CAUSES:
Temperature: Extremely high temperature causes the particles to vibrate, increasing the chance of the intermolecular bonds breaking.
pH: Extreme pH alters ionic bonds between molecules
EFFECT:
The enzyme loses its shape and specificity.
Explain the effects of:
- temperature
- pH
- substrate concentration
on enzyme structure and function with reference to collision theory, temporary, and permanent denaturation
Temperature: Increasing temperature increases rate of reaction (by increasing chances of collision) until the point of denaturation
pH: Optimum pH gives the highest rate of reaction
Substrate Concentration: Increases the rate of reaction until a maximum point where the rate will become constant
Draw + interpret graph of pH on enzyme activity
A change to pH from the optimum affects enzymes and their activity.
Extreme pH values can denature an enzyme by altering the three-dimensional structure of its active site.
The shape of the enzyme, along with its active site, will change.
If pH is lower or higher than the optimal, the rate of reaction gradually decreases.
Draw + interpret graph of temperature on enzyme activity
As the temperature increases, so does the rate of reaction, since there is more kinetic energy
There are more successful collisions and more ESC forms, so rate of reaction increases, up to the optimum temperature
As the temperature continues to rise, the rate of reaction falls rapidly
Increasing temperature causes the enzyme molecule to vibrate. At high temperatures there is too much vibration and the hydrogen bonds within the enzyme break. + The active site changes shape. ESC can no longer form and the enzyme is denatured
Draw + interpret graph of substrate concentration on enzyme activity
Identify the manipulated, responding and controlled variables in experiments of enzyme catalyzed reactions
Independent: Temp, pH, Sb. Concentration
Dependent: Enzyme activity
Control: Light intensity, volume, etc.
State the unit for enzyme reaction rate
Amount of chemical divided by time
State two methods for determining the rate of enzyme reaction rates
- Add a certain amount of chemical and measure the time it takes for all of the reactants to turn into products
2.Let the reaction happen for a fixed amount of time and measure the amount of product formed or remaining substrate
measuring the activity of catalase and hydrogen peroxide
one investigative technique for measuring the activity of an enzyme
Catalase and hydrogen peroxide:
MEASURE the volume of oxygen generated in a set time
measuring the activity of a amylase and starch
one investigative technique for measuring the activity of an enzyme
Amylase and starch:
Starch forms a blue-black colour with this solution, SO measure the time taken for starch to be broken down
How do you conduct enzyme-controlled experiments?
- Choose an enzyme
- Determine the substrate
- Decide what you are measuring (rate of product production or rate at which reactant is used up)
- Choose your independent variable (what you will change)
- Identify your control variables
How do you calculate the rate of reaction?
Define activation energy
Activation energy is the minimum amount of energy required to start a chemical reaction
activation energy is used to?
Activation energy is used to break or weaken bonds in the substrate so the reaction can occur
how do enzymes lower the activation energy of a reaction?
Enzymes lower activation energy by
- forming an enzyme-substrate complex (bringing the reactants together + putting strain on the substrate to weaken specific bonds, so they’re more likely to break during the reaction)
- providing an alternative reaction pathway with a lower energy requirement
interpret graphs showing the effect of lowering the activation energy by enzymes
In anabolic reactions, the enzyme ___?
holds the substrates close to one another, reducing repulsion and allowing them to bond more easily
In catabolic reactions, fitting the substrate into the active site puts ____?
strain on the bonds, making them easier to break
Compare the location of synthesis of enzymes used within and outside of a cell
Enzymes are synthesized in different locations depending on whether they are used inside or outside of a cell
Inside the cell:
- Enzymes are generally synthesized in the cell cytoplasm on ribosomes
(Some enzymes are also located within organelles like lysosomes and mitochondria)
Outside the cell:
- enzymes are synthesized in the rough endoplasmic reticulum (RER) of the exocrine pancreas
State an example of an intracellular metabolic reaction and an extracellular
metabolic reaction
intracellular:
- glycolysis
- Krebs cycle
extracellular:
- chemical digestion
intracellular?
within cells
(ex. catalase)
extracellular?
outside cells
(ex. trypsin and amalyse)
