topic 8

Question 1

anabolic processes are where energy is

Answer 1

stored

Question 2

catabolic processes are where energy is

Answer 2

released

Question 3

catabolic pathways ____

Answer 3

breakdown complex molecules into simpler compounds

Question 4

anabolic pathways ____

Answer 4

synthesize complicated molecules from simpler ones

Question 5

photosynthesis is an example of (catabolic or anabolic)?

Answer 5

anabolic pathway

Question 6

cellular respiration is an example of?

Answer 6

catabolic pathway

Question 7

the first law of thermodynamics states that ____

Answer 7

energy cannot be created or destroyed (but can be transferred/transformed)

Question 8

the second law of thermodynamics states that ____

Answer 8

spontaneous changes that do not require outside energy (no energy consumption) increase the entropy (disorder)
of the universe

Question 9

what is free energy? (ΔG)

Answer 9

a living system’s energy that can do work under cellular conditions

Question 10

what are exergonic reactions?

Answer 10

• when ΔG < 0
• free energy is released
• spontaneous reactions

Question 11

what are endergonic reactions?

Answer 11

• ΔG > 0
• absorb free energy from their surroundings
• non-spontaneous reactions

Question 12

what is ATP?

Answer 12

• adenosine triphosphate
• nucleotide that stores energy in phosphate bonds

Question 13

what is the function of ATP?

Answer 13

provides energy for cellular functions

Question 14

ATP powers cellular work by energy coupling; what is energy coupling?

Answer 14

the use of an exergonic process to drive an
endergonic one

Question 15

what are the 3 main types of endergonic cellular work?

Answer 15

• mechanical
• transport
• chemical

Question 16

how is ATP an example of mediated energy coupling?

Answer 16

ATP hydrolysis provides the energy required for the endergonic reaction to occur

Question 17

what is phosphorylation?

Answer 17

the transfer of a phosphate to other molecules

Question 18

how does ATP undergo mechanical, transport, and chemical work?

Answer 18

mechanical - ATP phosphorylates motor proteins

transport - ATP phosphorylates transport proteins

chemical - ATP phosphorylates key reactants

Question 19

what is the activation energy Ea?

Answer 19

the initial amount of energy need to start a chemical reaction

Question 20

what does the activation energy do?

Answer 20

it is needed to de-stabilize the structure of the reactants so they can react more easily

Question 21

what is denaturation?

Answer 21

the loss of a protein’s native conformation due to unravelling => loss of function

Question 22

what are some environmental factors that may affect enzyme activity?

Answer 22

• pH
• temperature
• cofactors

Question 23

what are cofactors?

Answer 23

non-protein enzyme helpers required for enzyme activity

Question 24

what is an example of an inorganic cofactor?

Answer 24

metal ions (ex: Zn, Cu)

Question 25

what are coenzymes? give an example

Answer 25

organic cofactors such as vitamins

Question 26

what are irreversible inhibitors?

Answer 26

bind to an enzyme by covalent bonding => inhibition is irreversible

Question 27

examples of irreversible inhibitors of the nervous sytsem?

Answer 27

sarin, DDT, parathion

Question 28

what are penicillin derivatives?

Answer 28

inhibit the enzyme transpeptidase that synthesizes the bacterial cell wall peptidoglycan

Question 29

what are reversible inhibitors?

Answer 29

bind to enzymes by weak bonds (non-covalent interactions: H-bonds, hydrophobic interactions, ionic bonds) => inhibition is reversible

Question 30

what are the 2 types of reversible inhibitors?

Answer 30

- competitive inhibitors - non-competitive inhibitors

Question 31

what are competitive inhibitors?

Answer 31

-compete with the substrate - bind to the active site of an enzyme (weak binding) to inhibit substrate binding

Question 32

what are non-competitive inhibitors?

Answer 32

- bind to another part of an enzyme not to the active site - change the shape of the enzyme - inhibit the function of the enzyme

Question 33

in ONLY competitive inhibition, how can inhibition be overcome?

Answer 33

by adding excess substrate

Question 34

what are 2 basic methods of enzyme regulation?

Answer 34

1. regulation of gene expression 2. feedback inhibition (by allosteric regulation)

Question 35

what is feedback inhibition?

Answer 35

- prevents a cell from wasting chemical resources by synthesizing more product than is needed - (end products always inhibits the pathway)

Question 36

give 2 examples of feedback inhibition

Answer 36

1. inhibition of catabolic pathways by ATP 2. inhibition of anabolic pathways by their end product (tryptophan)

Question 37

what is allosteric regulation?

Answer 37

- a form of reversible modulation common in enzymes (and proteins) made from polypeptide subunits – can be positive (activation) or negative (inhibition)

Question 38

allosteric activators stabilize the ____

Answer 38

active form of the enzyme

Question 39

allosteric inhibitors stabilize the ____

Answer 39

inactive form of the enzyme

Question 40

what is homotropic allosteric regulation?

Answer 40

binding of substrate to active site of one subunit locks all subunits into active conformation

Question 41

what is heterotropic allosteric regulation?

Answer 41

binding of regulatory molecules to sites other than the active sites

Question 42

what is cooperativity?

Answer 42

special form of positive allosteric regulation (activation) that can amplify enzyme activity

Question 43

given an example of cooperativity

Answer 43

- O2 binding to hemoglobin - the binding of substrate (oxygen) at one subunit increases the binding affinity of the other subunits (oxygen= allosteric activator)

Question 44

allosteric inhibitors can be ____

Answer 44

competitive or non-competitive

Question 45

heterotropic allosteric modulator

Answer 45

non-competitive inhibitors + activators

Question 46

give an example of a heterotropic allosteric activator

Answer 46

AMP is a heterotropic allosteric activator of PFK => (phosphofructokinase= glycolysis enzyme)

Question 47

give an example of a heterotropic allosteric inhibitor

Answer 47

CO2 is a heterotropic allosteric inhibitor (noncompetitive inhibitor) of hemoglobin => reduces hemoglobin's affinity for oxygen => oxygen is released in the tissues

Question 48

homotropic allosteric modulator

Answer 48

(competitive inhibitors + activators)

Question 49

give an example of a homotropic allosteric modulator

Answer 49

O2 and CO are homotropic allosteric modulators of hemoglobin

Question 50

O2 is a _____ of hemoglobin

Answer 50

homotropic allosteric activator

Question 51

CO is a _____ of hemoglobin

Answer 51

competitive inhibitor

Question 52

what is the main difference between homotropic and heterotropic allosteric modulators?

Answer 52

heterotropic --> a regulatory molecule that is NOT the enzyme's substrate homotropic --> both a substrate for its target enzyme and a regulatory molecule of the enzyme's activity