Chapter 6: Energy and Metabolism Flashcards
____________ are proteins or RNA molecules that act as catalysts to speed up reactions in living organisms.
Enzymes
What is a substrate?
A reactant molecule that binds to the active site of an enzyme
What are enzymes?
Proteins or RNA molecules that act as catalysts.
Where does a substrate bind on an enzyme in order for a chemical reaction to take place?
Active site
______________, or reactants, are molecules that bind to an enzyme at the active site and are converted to products in chemical reactions.
substrates
What is produced by the binding of enzyme and substrate?
Enzyme-substrate complex
Which of the following describes the active site of an enzyme?
It is the part of the enzyme where the substrate fits.
When several enzymes that catalyze different steps of a sequence of reactions are associated with one another in a noncovalently bonded assembly, they form a(n)
complex.
multienzyme
What is the optimal pH range for most human enzymes?
6 to 8
Changes in pH affect an enzyme because the interaction of charged amino acid residues in the enzyme are affected by
hydrogen ion concentrations.
What are competitive inhibitors?
competitive inhibitors?
Competitive inhibitors bind to the active site of an enzyme and prevent substrates from binding.
The ____________ site is a specific region of an enzyme to which non-competitive inhibitors bind in order to regulate enzyme activity.
Allosteric
___________ inhibitors bind to the active site of an enzyme and prevent the substrate from binding.
Competitive
Temperature affects chemical reactions in the following way: increasing the temperature of an uncatalyzed reaction __________ the rate of that reaction.
increases
__________ enzymes are enzymes that can exist in either an active or inactive conformation.
Allosteric
How can the functioning of an enzyme be affected by the external environment?
Temperature and pH can greatly affect the function of some enzymes by causing denaturation.
The optimum pH of most enzymes is 6 to ___.
8
How can some enzymes function well at a very low pH?
They maintain their three dimensional shape even at a very low pH.
__________ are small chemical components, usually inorganic ions, such as Zn2+, Cu2+, and Mn2+, that are often found in the active site participating directly in catalysis.
Cofactors
What type of reactions are involved in the synthesis of larger molecules from smaller precursor molecules?
Anabolic
Metabolic reactions are broken down into two main categories. Of those two main categories, what type of reactions are involved in the harvest of energy by breaking down larger molecules into smaller molecules?
Catabolic
Heat is a measure of the random motion of molecules, a form of ___ energy.
Kinetic
Work in the cell or in the physical world can only be done with expenditure of ___; it is defined as the capacity to do work.
Energy
Cells use ____ hydrolysis to drive endergonic reactions
ATP
A reaction that requires an input of energy is said to be a(n) ____ reaction
endergonic
What occurs during a redox reaction?
When an atom or molecule is oxidized, the electron that is removed is transferred to another atom or molecule, which is thereby reduced.
During a chemical reaction, which molecules become oxidized?
Molecules that have an electron removed.
Chemical reactions are ___, which means that they can proceed in either direction (reactants to products to reactants)
Reversible
ATP hydrolysis has a ______ ΔG
negative
Which of the ATP’s phosphate bonds is hydrolyzed in most cellular reactions?
The outermost
Select the three components of ATP
Adenine
Ribose
A chain of 3 phosphates
Phosphate bonds in ATP are high energy bonds, because they are
unstable
What cause the rate of some chemical reactions to be very slow?
Large activation energy
______ energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction
activation
Which characteristic of ATP is responsible for its high energy?
the repulsion of the negative phosphate groups
What is the 1st law of thermodynomics?
Energy cannot be created or destroyed it can only change from one form to another
What is the 2nd law of thermodynomics?
Energy cannot be transformed from one form to another with 100 % efficiency some energy is always unavailable
Entropy
A measure of randomness or disorder of a system; measure of how much energy in a system has become so dispersed it is no longer available to do work
