BIOL 435 Ch. 3 Part One (Recognition and Response)

Question 1

receptor-ligand binding

Answer 1

• occurs via multiple covalent bonds
• may be multivalent
• induces molecular change in the receptor

Question 2

multiple noncovalent bonds

Answer 2

• weak individual bonds add up to strong binding affinity

- many weak bonds=great cumulative bond strength

Question 3

types of non covalent bonds

Answer 3

• hydrogen bond
• ionic bond
• vander waals

Question 4

dissociation constant (Kd)

Answer 4

-a measure of strength of ligand binding
-lower=stonger
>lower [ ] 1/2 lignad is bound

Question 5

multivalency

Answer 5

-increases avidity of the interactions

Question 6

affinity

Answer 6

-the strength of an invidivual bond

Question 7

avidity

Answer 7

• the combined strength of multiple bonds

* an interacton may have weak affinity but high overall avidity

Question 8

molecular change in the receptor

Answer 8

• conformational
• dimerization/clustering
• localization in the membrane
• covalent modifications

Question 9

receptor interactions

Answer 9

-induce cascades of intracellular events
>activation of enzymes
>changes in intracellular location of molecules

Question 10

lipid raft

Answer 10

-PM where there is a higher proportion of sphingolipid and cholesterol
>internal kinases and phosphatases

Question 11

aggregation

Answer 11

-due to ligand binding enhance ligand binding Kd

Question 12

cell-cell interactions rely on

Answer 12

-a binding affinity to maintain contact over long periods of time

Question 13

extended contact

Answer 13

• facilitates signal transduction and exchange of cytokine signals
• cytoskeletal reorganization may occur

Question 14

lignad-binding ability

Answer 14

-can be affected by receptor types and levels of expression
-different combos of receptors/protein chains change affinity
>a ligand binding may cause the other protein chains to be upregulated

Question 15

level and natrue of cell-surface receptors

Answer 15

-tied to activation-state of the cell
Ex. activated lymphocytes upregulate IL-2Ralpha
>changes intermediate affintiy R to high affintiy R (produced alpha chain)
>IL-2 is also being upregulated

Question 16

local concentrations of ligands

Answer 16

• cell-cell interactions allow directional release of ligands
• can increase to very high levels: increasing signal strength

Question 17

immunoglobulin (Ig domains)

Answer 17

-contain parallel beta-strands organized as a pair of beta-sheets
-hydrophilic and hydrophobic AA alternate
>hydrophobic AA face centre
-stabilized by disulfide bonds
-forms ‘hydrophobic sandwich’

Question 18

examples of Ig domains in molecules

Answer 18

• Ig molecules (antibodies)
• T-cell accesory proteins (CD)
• adhesion molecules
• MHC molecules

Question 19

beta-sheets in Ig domain

Answer 19

-are connected by variable loops
>CDR-1, CDR-2, CDR-3
-key to variability of An binding sites

Question 20

CDR

Answer 20

-complementary determining regions

Question 21

loops

Answer 21

• often contain hydrohilic residues (2-16)
• found on protein surface
• connect helices and sheets
• allow protein folding
• reverse direction of peptide

Question 22

hypervariable loops

Answer 22

-responsible for sequence and structural diversity in Ab and TCR

Question 23

immune receptors

Answer 23

• bear Ig domains

- can be transmembrane, cytosolic or secreted

Question 24

soluble/secreted Ab

Answer 24

-Ig lacking the carboxyl terminus transmembrane segment is secreted

Question 25

BCR

Answer 25

• B-cell receptor

- contains an antibody of defined specificity

Question 26

TCR

Answer 26

• T cell receptor
• speicific for peptide antigens presented by MHC molecules
• peptides derived from proteins degraded by APC
• CD4 and CD8 are T-cell coreceptors that devine different subsets of T-cell function

Question 27

3 hypervariable regions

Answer 27

-of AA are found in variable heavy and variable light regions
-complementaryity-determining regions
>CDR3 is most variable
-heavy chain is most variable
*come together to form the antibody combining site

Question 28

framework region

Answer 28

• invariant AA interspersed near each CDR

- responsible for the folding of the CDRs to form the Ab combining site

Question 29

quaternary protein

Answer 29

• is made up of 2 identical heavy chains and 2 identical light chains
• hinge region
• 1 or 2 disulphide bonds
• 2 or 3 Ig domains in effector region of heavy chains

Question 30

hinge region

Answer 30

-can help the Ab bind in 2 places

Question 31

An specificity

Answer 31

-determined by structure of variable regions at ends of light/heavy chains

Question 32

Ab effector activity

Answer 32

• eg. phagocytosis and complement fixation

- a function of the interaction of the constant regions of the heavy chain