chapter 4

Question 1

Why binding is important in Physiology?

Answer 1

Binding of molecules to receptors causes changes in cells and serves in transporting, communicating and affecting the overall functions of organs

Question 2

examples of molecules binding

Answer 2

• hormones
• enzymes
• neurotransmitters
• gases

Question 3

Competition

Answer 3

The presence of multiple ligands able to bind to the same site

Question 4

Agonist

Answer 4

Binds and triggers response, goal is to activate or increase an action. Often mimics a natural produced ligand

-Ex. Decongestant-mimic epinephrine but on a subtype receptor of epi

Question 5

Antagonist

Answer 5

Molecule that does NOT activate as the natural ligand would. Often occupies the site so the natural ligand and its effect does not occur.

-Ex. Antihistamine-a histamine blocker by occupying those binding sites

Question 6

what is a ligand and are the forces

Answer 6

any molecule or ion that is bound to a protein by one of the following forces:

1. electrical attractions
2. Weaker attractions due to hydrophobic forces between nonpolar regions on the two molecules

Question 7

active site

Answer 7

region of a protein to which a ligand binds

Question 8

When a ligand binds to a protein the proteins’ specific function may either be _____ or _____

Answer 8

activated or inhibited

Question 9

Chemical specificity

Answer 9

in order to bind properly proteins must have the right conformational shape

-A single protein may have multiple active sites for multiple ligands OR multiple sites for one ligand

Question 10

Chemical specificity ; the active (binding) site determines ________________

Answer 10

the type of chemical that is bound

Question 11

Some sites only bind ____ ligand while others can bind _____ ligands

Answer 11

one; many

example:Drugs. The more sites a drug binds to, the higher the chance of unwanted side-effects.

Question 12

substrate=

enzyme=

Answer 12

substrate=ligand

enzyme=protein

Question 13

enzyme characteristics (4 main ones_

Answer 13

• can be defined as protein catalyst (speeds up reaction)
• Increases the rate of a reaction or Lowers the activation energy of the reaction
• enzyme itself is unchanged (a single catalyst molecule can act over and over again to catalyze many reactions)
• Enzymes end in -ase

Question 14

shape of active site on the enzyme provides basis for ______ _______.

Answer 14

enzymes specificity

–substrate comes and binds to an enzyme; lock and key model–>if substrate doesn’t fit it can’t bind there.

Question 15

the strength of ligand protein is a property of the binding site known as _____

Answer 15

affinity

Question 16

specificy depends on _____ of binding site

Answer 16

shape

Question 17

affinity depends on the ____ of attraction in binding site of protein to ligand

Answer 17

strength

Question 18

what does the affinity of a binding site for a ligand determine ?

Answer 18

how likely it is that a bound ligand will leave the protein surface and return to its unbound state.

Question 19

what does the term saturation refer to

Answer 19

the fraction of total active sites that are occupied at any given time.

Question 20

the percent saturation depends on

Answer 20

• the concentration ligand

- affinity

Question 21

chemical reactions involve breaking of chemical bonds into _____ (reactant/products) and the making of new chemical bonds in ______ (reactant/product)

Answer 21

reactant, products

Question 22

energy is added or released and doesn’t disappear (true or false)

Answer 22

true

Question 23

4 determinants of chemical reaction rates

Answer 23

1. reactant concentrations (higher concentration–>faster reaction rate)
2. activation energy (higher activation energy; slower reaction rate)
3. Temperature (higher temp–>faster reaction rate)
4. Catalyst (presence of catalyst–>faster reaction rate)