Lab Practical #2


Terms in this set (...)

Two major functions of enzymes
1. structural- provide cells and organisms with form and framework
2. functional- control the chemical reactions in a cell
Enzymes are composed of
amino acids
they are protein molecules and that makes them large, complex and varied
Proteins structure
composed of amino acids, carbon compounds containing an amino group and an acid group
-limitless variety - allows for adaptability to all sorts of cellular uses.
Examples - insulin, hemoglobin
amino acids
20 different amino acids differ only in the "R" group
3 structural levels of protein organization
Primary - specific sequence joined together by dehydration synthesis, 100 - 1000 amino acids long.

Secondary structure - coiling of amino acid into a helix - spiral staircase.
Hydrogen bonds between amino groups and acid groups.

Tertiary structure - Protein molecule folds due to positive and negative charges in the "R" groups. Results in a 3-D shape - give proteins especially enzymes their distinctive properties.
Enzymes function
as biocatalysts, manage chemical transformations that produce "life"
alter the rate of chemical change, not altered or destroyed in the process

Molecule is reusable.

Combines only with another molecule that "fits" properly, like a puzzle piece
Molecules that Brings chemical change
active site
part of enzyme involved with the substrate is the active site.
- Limited to catalyzing only one kind of reaction.
- Named for their substrate or the type of reaction they catalyze.
- Temperature or pH will alter the shape of the enzyme molecule and its activity.
- Destroyed = denatured
- Optimum temperature at which it works
- Decrease temp - decrease rate of reaction
- Freezing does not denature - stops activity.
=- Destroyed
heat, ph, Na concentration
stops activity
does not denature
Decrease temp
decrease rate of reaction
Temperature or pH
will alter the shape of the enzyme molecule and its activity
H ion concentration
affects enzyme activity.
Optimum pH, prefer near pH 7
enzymes are named for
their substates or the type of reaction they catalyze
usually end in -ase-
have proteins as substrates
hydrolyzes disaccharide maltose
catalyzes an oxidation
enzymes that cause dehydration synthesis
enzymes that hydrolyze or digest
bromelin and pepsin
enzymes that don't fit the ase pattern ending
saliva contains the enzyme
salivary amylase whose substrate is starch
starch is hydrolyzed or digested by
amylase and the sugar maltose is produced
benedicts test
tests for reducing sugars
enzyme common to plants and animals cells
plentiful in the liver and in blood
decomposes hydrogen peroxide into water
Factors that affect enzyme reaction rate
Enzyme concentration
Substrate concentration
Enzymes _____ be used again
all the chemical reactions that occur within a cell
molecules that undergo a change which results in the products
organic catalysts that speed metabolic reactions
type of enzyme that breaks down hyrogen peroxide and turns it unto water and oxygen.
the reactant in an enzymatic chemical reaction
are specific because they have a shape that accommodates the shape of their substrates
Enzyme formula
ES=enzyme substrate complex
Degradation reaction
the substrate is broken down to the products
synthesis reaction
the substrates are joined to form a product
Active site
the location where the enzyme and substrate form an enzyme substrate complex-the reaction occurs here
used over and over
involved in a degradation reaction. It speeds the breakdown of hydrogen peroxide in nearly all organisms
cellular organelle that contains catalase is present in every plant and animal organ-school laboratories use the potato as a source of catalase
Hydrogen peroxide
is a powerful oxidizer that can attack and denature cellular molecules like DNA
Catalase formula
is speeds the breakdown of hydrogen peroxide into water and oxygen
2H2O2(hydrogen peroxide)➝(catalase)➝2H20(water)+O2(oxygen)
Why does bubbling occur in a catalase reaction?
because oxygen is released
What is the reactant in a catalase reaction?
hydrogen peroxide
What is the substrate for catalase?
Hydrogen peroxide
What are the products of a catalase reaction?
Oxygen and water
What type of molecule is an enzyme
a protein
the optimum pH for catalase
pH of seven
Catalase with water and sucrose
catalase does not react because these are not the proper substrate for the enzyme
Temperatures of chemical reactions
cold temps slow chemical reactions while warm temps speed chemical reactions.
boiling causes an enzyme to do this, meaning its shape is altered in a way that inactivates it
Enzyme temperature experiments
no reaction between catalase and hydrogen peroxide when catalase was boiled. Slow reaction between catalase and HP when catalase was refrigerated. Best reaction between C and HP when catalase was placed in an incubator
Why doesnt catalase react with water and sucrose?
because they were lacking the correct substrate.
A higher enzyme or substrate concentration
results in faster enzyme activity-the amount of product per unit of time for any particular reaction will increase
Enzyme concentration experiment
if unlimited time was there the results would be the same, however the fastest reaction takes place in the tubes with the higher enzyme concentration
Function of an active site
is the part of the enzyme where substrates bind to the enzyme and undergo chemical reactions
Four conditions that maximize enzymatic activity
Temperature, pH, concentration of enzyme, and presence of the correct substrate
What happens during denaturization?
a molecule is broken down, changes shape, and can no longer be used
What happens to the rate of enzyme activity as you increase temperature?
enzyme activity increases
What happens to catalase when its boiled?
it becomes denatured
Why does more enzyme concentration increase activity?
more active sites
pH on enzyme activity
any higher or lower pH affects hydrogen bonding and the structure of the enzyme leading to reduced activity
pH experiment
(acid) HCl was added to catalase and HP, water was added to catalase and HP, and (base) NaOH was added to catalase and HP. Acid was reduced activity because it denatures the enzyme. Water had nice activity because it has a neutral pH. The base had reduced activity because it denatures the enzyme.
Temperatures that promote/inhibit enzyme activity
0 degrees celsius lowers enzyme activity, 38 degrees celsius promotes enzyme activity, 100 degrees celsius inhibits enzyme activity
Why optimum pH promotes enzyme activity
Enzymes are particles made of protein. They speed up chemical reaction within a cell. They work in the "lock and key" manner with a substrate. Each enzyme has it's own optimal Ph that allows it to lock in with the substrate and perform it's function as a catalyst.
The optimal pH allows this reaction between the enzyme and substrates to be continue. In other words the reaction can be reversible. The enzyme can continue locking with a substrate and continue it's catalysts activity. If the pH is too high or too low it can change the shape of the enzyme. The ionic bonds that hold the shape of the enzyme are broken changing the 3D shape of the enzyme. This causes the enzyme to be completely inactive and can not be restored again.
What conditions speed a chemical reaction
more enzyme because more active sites are available, more substrate because theres more chance of an interaction between enzyme and substrate
The amount of bubbling in the experiment corresponded with what?
the degree of enzyme activity and the presenese of its specific substrate.
How did temperature affect catalase?
at temperatures above 40°C, the enzyme catalase will become less effective, is proven to be true. Enzymes are made of proteins which will become unstable at higher temperatures. As the shape and structure of the catalase enzyme changes, its effectiveness as an enzyme is reduced.
Effect of pH on enzymes
Enzymes are affected by changes in pH. The most favorable pH value - the point where the enzyme is most active - is known as the optimum pH. xtremely high or low pH values generally result in complete loss of activity for most enzymes. pH is also a factor in the stability of enzymes. As with activity, for each enzyme there is also a region of pH optimal stability.The optimum pH value will vary greatly from one enzyme to another. For example pepsin needs a very low pH.
What happens at the active site of an enzyme?
Substrates are oriented to bring about the reaction
On the basis of the active site, explain why the following conditions speed a chemical reaction: More enzyme
There are more active sites available for substrates
On the basis of the active site, explain why the following conditions speed a chemical reaction: More substrate
It is more likely that a substrate molecule will encounter an active site. Enzymes are also not destroyed when undergoing catalytic reactions.
Name three other conditions (other than the ones mentioned in question 2) that maximize enzymatic
a. specific enzyme for a given substrate
b. optimum pH
c. optimum temperature
why is having the correct enzyme/substrate important for enzymatic reactions??
Enzyme is specific for the substrate.
Why is optimum pH important for enzymatic reactions?
Enzyme shape is pH
Why is optimum temperature important for enzymatic reactions?
Movement of molecules increases as temperature rises. Beyond optimum temperature, the enzyme may be degraded.
Lipase is a digestive enzyme that digests fat droplets in the basic conditions (NaHCO3 is present)
of the small intestine. Indicate which of the following test tubes would show digestion following
incubation at 37°C, and explain why the others would not.
Tube 1: Water, fat droplets
Tube 2: Water, fat droplets, lipase
Tube 3: Water, fat droplets, lipase, NaHCO3
Tube 4: Water, lipase, NaHCO3
Tube 1: Water, fat droplets No enzyme
Tube 2: Water, fat droplets, lipase Wrong pH
Tube 3: Water, fat droplets, lipase, NaHCO3 Digestion occurs
Tube 4: Water, lipase, NaHCO3 No substrate
Given the following reaction: Catalase working on hydrogen peroxide to turn into water and oxygen: Which substance is the substrate?
Hydrogen peroxide.
Given the following reaction: Catalase working on hydrogen peroxide to turn into water and oxygen: Which substance is the enzyme?
Given the following reaction: Catalase working on hydrogen peroxide to turn into water and oxygen: Which substances are the end products?
Water and oxygen.
Given the following reaction: Catalase working on hydrogen peroxide to turn into water and oxygen: Is this a synthetic or degradative reaction? How do you know?
Degradative. The larger molecule on the left becomes the two smaller molecules on the right.
Enzymes function by
lowering the activation energy of a reaction without being consumed.
The substance that an enzyme combines with is
the substrate
Enzyme specificity refers to
the fact that enzymes catalyze one particular substrate or small number of structurally similar substances
when an enzyme becomes denatured it
loses its ability to function
An enzyme may lose its ability to function because
of excessive temperature, a change in its #d structure or a large change in the pH of the encironment.
pH is a measure of
the hydrogen ion concentration
catalyzes the breakdown of hydrogen peroxide into water
the bubbling height used in the experiments of this exercise is
1) the production of oxygen and water
2) an index of enzymatic activity