Exam 2 Flashcards
At very high temperatures (e.g., above 100°C), enzymes cease to perform their function. This happens because the high temperature
A. causes the substrate to move so fast the enzyme cannot bind to it
B. denatures the cofactor
C. converts the enzyme into product molecules
D. destroys the shape of the enzyme
D. destroys the shape of the enzyme
Which of the following statements is FALSE?
A. The lock and key model refers to the specificity of an enzyme for its substrate
B. Cofactors bind to substrate molecules and prevent enzymatic reactions from occurring
C. Temperature and pH have significant effects on the activity of an enzyme
D. Enzymes are proteins that are synthesized by ribosomes
B. Cofactors bind to substrate molecules and prevent enzymatic reactions from occurring
In the “lock and key model” of enzyme activity, which molecule is described as the “key”. The enzyme, substrate or product.
A. Enzyme
B. Substrate
C. Cofactor
D. Inhibitor
B. Substrate
Lactase is an enzyme that converts lactose to glucose and galactose. A scientist measured the time it took lactase to convert the lactose in different pH environments. His results are represented in the following table.
PH. - Avg. time for conversion (secs) 4- 105 5- 95 6- 82 7- 89 8- 110
What is the optimal pH for the lactase reaction?
6
What organelle found in cells produces or synthesizes enzymes?
Ribosome
Cyclooxygenase (COX) promotes the conversion of Arachidonic acid to Prostaglandins. Prostaglandins is a hormone that functions in activating pain signals and inducing inflammation. Pain killers such as Aspirin work by inhibiting the activity of Cyclooxygenase.
- Which of the bolded words is the molecule with an active site?
- Which of the bolded words is the substrate?
- Cyclooxygenase (COX)
2. Arachidonic acid
When your cells produce carbon dioxide (CO2) as a waste product, it is immediately converted to carbonic acid (H2CO3) in the following reaction:
CO2 + carbonic anhydrase + zinc —> H2CO3 + carbonic anhydrase + zinc
- Which of the molecules is the enzyme?
- What is the cofactor in this reaction?
- Carbonic anhydrase
2. zinc
An enzyme is an example of which macromolecule?
protein
What is the function of a catalyst? Are enzymes catalysts?
To speed up reaction, yes
Is the substrate/reactant of the left or right side of an equation? Product?
substrate- left
product- right
How do enzymes affect the activation energy needed for a chemical reaction?
enzymes reduce activation energy which causes the reaction requires less energy to get started. If an enzyme is present, the AE is reduced significantly and it will be faster bc requires less energy.
Will a chemical reaction occur when an enzyme is not present? What is the difference in activation energy when an enzyme is not present?
Yes, Chemical reactions occur too slowly without enzymes so you would already be dead.
What name is given to the region or site on an enzyme where a substrate binds?
Active site
Name and describe the 3 properties of enzymes.
- Biological catalyst: speeding up chemical reactions. That is, they are catalytic
- Recyclable: They do not become a part of the chemical reaction. They catalyze a chemical reaction and once the products are formed and released, they move on unchanged to catalyze another reaction
- Highly specific: for the substrates they bind. Only a substrate with the exact shape as the shape of the binding region of the enzyme will bind to that enzyme
What happens to the activation energy once the substrate binds to an enzyme at the binding region?
The activation energy is then reduced and the chemical reaction can occur quickly.
What are examples of cofactors? Do they bind to enzymes or substrates? How do they help the molecules to which they bind?
Cofactors: a mineral/vitamin (iron, mg, zinc) that is necessary to maintain the 3d shape of an enzyme.
They bind to enzymes by filling in empty space the substrate can’t fill so it’s a perfect fit.
They are specific accessory molecules required for enzymes to function.
3 Factors that affect enzyme function?
Temp, pH, Inhibitors
Do warm or cold temp. cause peak activity of enzymes?
warm
the higher temp, the ___ reaction rate unit a certain point where the enzyme becomes ____.
faster, denatured
What are irreversible inhibitors? Give examples.
Inhibitors that bind to enzymes at the binding region and cause permanent damage to enzyme shape which leads to loss of enzyme function.
Heavy metal ions (mercury and lead), nerve gas poisons (cyanide), some insecticides
what are reversible inhibitors? what are the two types?
Reversible inhibitors cause temporary loss.
Competitive inhibitors: inhibitor and substrate both bind to the active site of the enzyme. Binding of an inhibitor prevents substrate binding, thereby inhibiting enzyme activity. They compete for active site bc they have the same site
Noncompetitive inhibitors: Inhibitor and substrate bind to different sites. There is an active site and inhibitor site so they aren’t competing for the active site. When it binds, it changes the shape of the enzyme and they mess up the active site.
what is a polypeptide bond?
individual covalent bonds that link amino acids in polypeptide chains
What is the ultimate source of energy?
Solar energy/ energy from sun
What are autotrophs? What do they do?
they are plants and other photosynthetic organisms. They capture solar energy (form sun) in the form of light energy which is converted into chemical energy.
