Incourse 1

Question 1

what are biological membranes?

Answer 1

Define the boundaries of cells as well as compartments within cells.

Question 2

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

Answer 2

d) all of the above

Question 3

What drives the formation of lipid micelles and bilayers?

A) Entropy
B) Hydrophobic effect
C) Hydrophilic interactions
D) Van der Waals forces

Answer 3

b) hydrophobic effect

Question 4

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

Answer 4

B) 5-10nm

Question 5

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

Answer 5

C) integral membrane proteins

Question 6

8. 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

Answer 6

C) lipid anchored proteins

Question 7

7. 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

Answer 7

B) charge - charge interactions and hydrogen bonding

Question 8

6. 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

Answer 8

A) transmembrane proteins

Question 9

4. What drives the formation of lipid micelles and bilayers?
   
   • a. Hydrogen bonding
   • b. Ionic interactions
   • c. Hydrophobic effect
   • d. Electrostatic repulsion

Answer 9

C) hydrophobic effect

Question 10

1. Which of the following lipids does not form bilayer membranes by itself?
   
   • a. Phosphatidylcholine
   • b. Phosphatidylserine
   • c. Cholesterol
   • d. Sphingomyelin

Answer 10

C) cholesterol

Question 11

3. 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

Answer 11

A) moving specific phospholipids between leaflets

Question 12

4. 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

Answer 12

b. Associating with the lipid bilayer via charge-charge interactions and hydrogen bonding

Question 13

6. 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

Answer 13

D) preventing membranes from crystallizing at low temperatures

Question 14

7. 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

Answer 14

c. A model describing the dynamic structure of biological membranes with proteins and lipids

Question 15

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

Answer 15

b) Energy tends to flow from areas of lower concentration to areas of higher concentration

Question 16

Equation for spontaneous process

Answer 16

(△S (system) + △S (surroundings)) > 0

Question 17

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

Answer 17

b) A reaction that releases energy and occurs without additional energy input

Question 18

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

Answer 18

c) The energy available to do useful work in a system at constant pressure and temperature

Question 19

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

Answer 19

a) Energy cannot be created nor destroyed, only transferred or transformed

Question 20

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

Answer 20

d) ΔE = q - w

Question 21

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

Answer 21

c. Combining an exergonic and an endergonic reaction

Question 22

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

Answer 22

b. Reverse direction

Question 23

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

Answer 23

a. When the rates of forward and reverse reactions are equal

Question 24

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

Answer 24

a. ΔG = ΔH - TΔS

Question 25

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

Answer 25

a. Exergonic reactions

Question 26

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

Answer 26

c. It remains constant

Question 27

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

Answer 27

b. Endergonic

Question 28

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

Answer 28

c. Binding of effectors to allosteric sites

Question 29

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.

Answer 29

d. They stabilize the enzyme's active conformation.

Question 30

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

Answer 30

c. Covalent modification

Question 31

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.

Answer 31

c. It inhibits an enzyme earlier in the pathway.

Question 32

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.

Answer 32

c. They compete with substrates for the active site.

Question 33

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

Answer 33

d. Non-competitive inhibition

Question 34

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.

Answer 34

c. They denature enzymes and lead to a loss of activity.

Question 35

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

Answer 35

a. Allosteric regulation

Question 36

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

Answer 36

d. Substrate concentration regulation

Question 37

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.

Answer 37

c. It binds to calcium ions and activates enzymes.