Protein Function: The immune system and motors

Question 1

What is a key feature of protein-ligand interactions?

Answer 1

They are often based on the presence of a cleft lined with amino acid R-groups.

Question 2

How does protein conformation affect ligand binding?

Answer 2

The binding of ligands (e.g., O2 or CO) to the haem affects the protein’s conformation and vice versa

Question 3

What is essential for binding sites in proteins?

Answer 3

They must effectively discriminate between ligands, even with small structural differences.

Question 4

What is the role of the haem group in globins?

Answer 4

It binds oxygen and carbon monoxide, influencing the protein’s conformation

Question 5

What is the significance of reversible ligand binding?

Answer 5

It is crucial for sensitive and specific biochemical systems.

Question 6

What distinguishes “self” from “non-self” in the immune system?

Answer 6

All vertebrates possess an immune response that can make this distinction

Question 7

What does the immune system eliminate?

Answer 7

Viruses, bacteria, and other pathogens, as well as foreign molecules.

Question 8

What components are involved in the immune response?

Answer 8

Specialist proteins (e.g., immunoglobulins), small molecules (e.g., cytokines), and various cell types

Question 9

What is the Major Histocompatibility Complex (MHC)?

Answer 9

A set of proteins on the surface of vertebrate cells that presents antigens to T-cellsv

Question 10

How many class I MHC proteins can an individual produce?

Answer 10

Up to six class I MHC proteins.

Question 11

What is the primary function of class I MHC proteins?

Answer 11

To signal to T-cells when cells are infected by viruses.

Question 12

How many class II MHC proteins can an individual produce?

Answer 12

Up to twelve class II MHC proteins

Question 13

What is an antigen?

Answer 13

A molecule recognized by the immune system

Question 14

What is the role of the T cell receptor (TCR)?

Answer 14

It recognizes the MHC-antigen complex, crucial for the immune response

Question 15

What is the humoral immune response?

Answer 15

The antibody-mediated immune response where antibodies bind to antigens

Question 16

What is the structure of IgG antibodies?

Answer 16

Composed of four polypeptide chains: two light chains and two heavy chains

Question 17

What is the total molecular weight of an IgG antibody?

Answer 17

Approximately 150 kDa.

Question 18

What are the components of the light and heavy chains in antibodies?

Answer 18

Light chains: 1 constant domain and 1 variable domain; Heavy chains: 3 constant domains and 1 variable domain

Question 19

What happens when an antibody is cut with papain?

Answer 19

It generates Fc and Fab fragments

Question 20

What is the function of the Fab fragment?

Answer 20

It is responsible for antigen binding.

Question 21

What stabilises immunoglobulin domains?

Answer 21

A disulfide bond

Question 22

What is the typical structure of immunoglobulin domains?

Answer 22

A 7-9 stranded β-barrel with two antiparallel β-sheets

Question 23

What is the significance of the hinge region in antibodies?

Answer 23

It allows antibodies to bind tightly and specifically to antigens.

Question 24

What is the binding energy of antibodies to antigens?

Answer 24

Approximately -65 kJ/mol.

Question 25

What is the equation for the dissociation constant (Kd) of antibody-antigen complexes?

Answer 25

Kd = [Ab−Ag]/ [Ab][Ag] ​

Question 26

What is the role of myosin in muscle contraction?

Answer 26

Myosin interacts with actin to facilitate muscle contraction.

Question 27

What triggers muscle contraction?

Answer 27

The release of Ca²⁺ ions in response to nerve impulses.

Question 28

What is the cross-bridge cycle?

Answer 28

The series of steps involving ATP binding and hydrolysis that leads to muscle contraction

Question 29

What are the components of thick filaments in muscle?

Answer 29

Myosin II, consisting of two heavy chains and four light chains.

Question 30

What is the function of ATP in muscle contraction?

Answer 30

It provides the energy needed for myosin to change conformation and interact with actin.

Question 31

What are the components of thin filaments?

Answer 31

Monomeric actin (G-actin) that forms filamentous actin (F-actin).

Question 32

How does ATP hydrolysis relate to actin assembly?

Answer 32

ATP is hydrolyzed to ADP during the assembly of actin, not during contraction.

Question 33

What role does tropomyosin play in muscle contraction?

Answer 33

It covers myosin binding sites on actin, regulating contraction

Question 34

What is the role of troponin in muscle contraction?

Answer 34

It binds Ca²⁺ ions, causing a conformational change that allows contraction.

Question 35

What is the significance of the sarcomere structure?

Answer 35

It is the basic unit of muscle contraction, where thick and thin filaments slide past each other

Question 36

What is Western Blotting?

Answer 36

A technique used to detect specific proteins in a sample using antibodies

Question 37

What is immunohistochemistry?

Answer 37

A method for detecting specific antigens in tissues using antibodies.

Question 38

What is the role of antibodies in experiments?

Answer 38

They are used to identify and quantify specific proteins or antigens.

Question 39

What is the importance of antibody specificity?

Answer 39

It ensures that antibodies bind only to their specific epitopes.

Question 40

What is an epitope?

Answer 40

The part of an antigen that is recognized by an antibody.

Question 41

How do proteins achieve spatial and temporal organisation?

Answer 41

Through interactions with ligands and other proteins

Question 43

What is the primary energy source for motor proteins?

Answer 43

ATP is the fuel for cyclical conformational changes in motor proteins

Question 44

What is the effect of Ca²⁺ ions on muscle contraction?

Answer 44

They trigger conformational changes that allow actin and myosin interactions

Question 45

What is the role of cytokines in the immune response?

Answer 45

They are small signaling molecules that mediate and regulate immunity.

Question 46

What is the significance of immunoglobulins in the immune system?

Answer 46

They are key components of the antibody-mediated immune response.

Question 47

What is the relationship between myosin heads and muscle contraction?

Answer 47

Only 1-3% of myosin heads are bound at any moment, preventing slippage

Question 48

What is the Greek Key motif in immunoglobulin domains?

Answer 48

A structural arrangement that stabilizes the domain.

Question 49

How do antibodies undergo conformational changes?

Answer 49

Binding to antigens often induces structural changes for better fit.

Question 50

What is the role of disulfide bonds in antibodies?

Answer 50

They stabilize the overall structure of the antibody.

Question 51

How does the immune response adapt to new pathogens?v

Answer 51

Through the generation of diverse antibodies that can bind to various epitopes.