Incourse 1 Flashcards
what are biological membranes?
Define the boundaries of cells as well as compartments within cells.
What is the primary function of biological membranes?
a) to define the boundaries of cells
b) to separate compartments within cells
c) to perform complex functions
d) all of the above
d) all of the above
What drives the formation of lipid micelles and bilayers?
A) Entropy
B) Hydrophobic effect
C) Hydrophilic interactions
D) Van der Waals forces
b) hydrophobic effect
What is the typical thickness of a biological membrane?
- A) 1-2 nm
- B) 5-10 nm
- C) 20-30 nm
- D) 50-100 nm
B) 5-10nm
Which type of proteins are embedded within the hydrophobic core of the lipid bilayer?
- A) Peripheral membrane proteins
- B) Lipid-anchored proteins
- C) Integral membrane proteins
- D) All of the above
C) integral membrane proteins
- What type of proteins are covalently attached to lipids embedded within the cell membrane?
- a. Transmembrane proteins
- b. Peripheral membrane proteins
- c. Lipid-anchored proteins
- d. Integral membrane proteins
C) lipid anchored proteins
- How are peripheral membrane proteins associated with the lipid bilayer?
- a. Covalent attachment
- b. Charge-charge interactions and hydrogen bonding
- c. Insertion into the hydrophobic core
- d. Association with integral membrane proteins
B) charge - charge interactions and hydrogen bonding
- Which class of membrane proteins spans the lipid bilayer completely?
- a. Transmembrane proteins
- b. Peripheral membrane proteins
- c. Lipid-anchored proteins
- d. Integral membrane proteins
A) transmembrane proteins
- What drives the formation of lipid micelles and bilayers?
- a. Hydrogen bonding
- b. Ionic interactions
- c. Hydrophobic effect
- d. Electrostatic repulsion
C) hydrophobic effect
- Which of the following lipids does not form bilayer membranes by itself?
- a. Phosphatidylcholine
- b. Phosphatidylserine
- c. Cholesterol
- d. Sphingomyelin
C) cholesterol
- What is the role of translocases in maintaining lipid asymmetry in biological membranes?
- a. Moving specific phospholipids between leaflets
- b. Stabilizing lipid micelles
- c. Facilitating hydrogen bonding between lipids
- d. Promoting lipid crystallization
A) moving specific phospholipids between leaflets
- What is the main function of peripheral membrane proteins?
- a. Spanning the lipid bilayer
- b. Associating with the lipid bilayer via charge-charge interactions and hydrogen bonding
- c. Covalently attaching to lipids embedded within the membrane
- d. Anchoring proteins to the cell membrane surface
b. Associating with the lipid bilayer via charge-charge interactions and hydrogen bonding
- What is the role of cholesterol in biological membranes?
- a. Forming bilayers by itself
- b. Promoting lipid asymmetry
- c. Facilitating hydrogen bonding between lipids
- d. Preventing membranes from crystallizing at low temperatures
D) preventing membranes from crystallizing at low temperatures
- What is the fluid mosaic model?
- a. A model describing the arrangement of lipids in biological membranes
- b. A model explaining the fluidity of phospholipid tails
- c. A model describing the dynamic structure of biological membranes with proteins and lipids
- d. A model illustrating lipid asymmetry in biological membranes
c. A model describing the dynamic structure of biological membranes with proteins and lipids
According to the second law of thermodynamics, which of the following statements is true?
a) Energy can be created or destroyed in a closed system
b) Energy tends to flow from areas of lower concentration to areas of higher concentration
c) The entropy of a system always decreases over time
d) Energy transformations are always 100% efficient
b) Energy tends to flow from areas of lower concentration to areas of higher concentration
Equation for spontaneous process
(△S (system) + △S (surroundings)) > 0
Which of the following describes a spontaneous reaction?
a) A reaction that requires an input of energy to occur
b) A reaction that releases energy and occurs without additional energy input
c) A reaction that does not involve any energy changes
d) A reaction that occurs at a constant rate
b) A reaction that releases energy and occurs without additional energy input
Which of the following is the definition of Gibbs free energy?
a) The energy required to initiate a chemical reaction
b) The energy released during a chemical reaction
c) The energy available to do useful work in a system at constant pressure and temperature
d) The energy stored in the bonds of molecules
c) The energy available to do useful work in a system at constant pressure and temperature
What is the first law of thermodynamics?
a) Energy cannot be created nor destroyed, only transferred or transformed
b) Energy always flows from areas of higher concentration to areas of lower concentration
c) The total energy of a closed system remains constant
d) Energy is released in the form of heat during chemical reactions
a) Energy cannot be created nor destroyed, only transferred or transformed
Which equation represents the first law of thermodynamics?
a) ΔS(system) + ΔS(surroundings) > 0
b) ΔG = ΔH - TΔS
c) ΔG’º = ΔG’º(products) - ΔG’º(reactants)
d) ΔE = q - w
d) ΔE = q - w
What does the term “reaction coupling” refer to in bioenergetics?
a. Combining two exergonic reactions
b. Combining two endergonic reactions
c. Combining an exergonic and an endergonic reaction
d. Combining two spontaneous reactions
c. Combining an exergonic and an endergonic reaction
In which direction does a reaction proceed under standard conditions when ΔG’º is positive?
a. Forward direction
b. Reverse direction
c. Both directions simultaneously
d. It remains at equilibrium
b. Reverse direction
When is a reaction considered to be at equilibrium?
a. When the rates of forward and reverse reactions are equal
b. When the reactants are completely consumed
c. When the temperature decreases
d. When the concentration of products is zero
a. When the rates of forward and reverse reactions are equal
Which equation is used to determine the Gibbs free energy (ΔG) of a reaction under standard conditions?
a. ΔG = ΔH - TΔS
b. ΔG = ΔE + PΔV
c. ΔG = ΔE - TΔS
d. ΔG = ΔH + TΔS
a. ΔG = ΔH - TΔS
In which type of reactions is the ΔG negative, indicating that the reaction is spontaneous?
a. Exergonic reactions
b. Endergonic reactions
c. Equilibrium reactions
d. Non-spontaneous reactions
a. Exergonic reactions
According to the First Law of Thermodynamics, what happens to the total amount of energy in the universe during physical or chemical changes?
a. It increases
b. It decreases
c. It remains constant
d. It becomes unpredictable
c. It remains constant
Which term is used to describe a reaction that requires an input of energy to proceed, and has a positive ΔG?
a. Exergonic
b. Endergonic
c. Equilibrium
d. Spontaneous
b. Endergonic
What is allosteric regulation of enzymes primarily based on?
a. Binding of substrates to the active site
b. Covalent modifications of the enzyme
c. Binding of effectors to allosteric sites
d. Changes in pH and temperature
c. Binding of effectors to allosteric sites
How do allosteric activators affect enzyme activity?
a. They inhibit the enzyme’s activity.
b. They stabilize the enzyme’s inactive conformation.
c. They reduce the enzyme’s affinity for its substrate.
d. They stabilize the enzyme’s active conformation.
d. They stabilize the enzyme’s active conformation.
Which type of enzyme regulation involves the addition or removal of chemical groups from specific amino acid residues?
a. Competitive inhibition
b. Non-competitive inhibition
c. Covalent modification
d. Allosteric regulation
c. Covalent modification
In feedback inhibition, what is the role of the end product of a metabolic pathway?
a. It activates the enzyme at the beginning of the pathway.
b. It enhances the enzyme’s affinity for its substrate.
c. It inhibits an enzyme earlier in the pathway.
d. It stabilizes the enzyme’s active conformation.
c. It inhibits an enzyme earlier in the pathway.
What is the primary function of competitive inhibitors?
a. They enhance enzyme activity.
b. They bind to allosteric sites.
c. They compete with substrates for the active site.
d. They stabilize the enzyme’s active conformation.
c. They compete with substrates for the active site.
Which type of enzyme regulation does not involve direct competition with substrates for the active site?
a. Allosteric regulation
b. Covalent modification
c. Competitive inhibition
d. Non-competitive inhibition
d. Non-competitive inhibition
How can extreme pH values or temperatures affect enzyme activity?
a. They have no effect on enzyme activity.
b. They activate enzymes.
c. They denature enzymes and lead to a loss of activity.
d. They stabilize the enzyme’s active conformation.
c. They denature enzymes and lead to a loss of activity.
What type of enzyme regulation involves the binding of regulatory proteins to activate or inhibit an enzyme?
a. Allosteric regulation
b. Feedback inhibition
c. Covalent modification
d. pH and temperature regulation
a. Allosteric regulation
Which mechanism of enzyme regulation is primarily based on changes in substrate concentration?
a. Allosteric regulation
b. Competitive inhibition
c. Non-competitive inhibition
d. Substrate concentration regulation
d. Substrate concentration regulation
What is the role of calmodulin in enzyme regulation?
a. It is an allosteric inhibitor.
b. It binds to substrates in the active site.
c. It binds to calcium ions and activates enzymes.
d. It stabilizes the enzyme’s inactive conformation.
c. It binds to calcium ions and activates enzymes.
