week 8

Question 1

The Energy of Life.

name all components (5)

Answer 1

• All living organisms require energy in order to survive
• The sunlight is the source of energy on Earth
• The sunlight is used for synthesis of sugars through
photosynthesis (by plants)
• Energy is transferred through metabolism
• The living cell is a miniature factory where thousands of
reactions occur => Converts energy in many ways
• Example: some organisms convert energy to light
(bioluminescence)

Question 2

Energy flow on Earth.

Steps

Answer 2

• Sun → Producers → Consumers, decomposers

Question 3

What is Metabolism

Answer 3

is the totality of an organism’s
chemical reactions through which:
- Energy is stored (anabolic processes)
- Energy is released (catabolic processes)

Question 4

Metabolic Pathways

Answer 4

• A metabolic pathway has many steps that begin with a
specific molecule and end with a product
• Each step is catalyzed by a specific enzyme
• Metabolic pathways are controlled according to cellular
demands

Question 5

pic page 6

Answer 5

week 8

Question 6

Catabolic pathways

Answer 6

• Release energy**

• Break down complex molecules into simpler
compounds
• Example: cellular respiration

Question 7

Anabolic pathways

Answer 7

• Consume energy**

• Synthesize complicated molecules from
simpler ones
• Example: photosynthesis, protein synthesis
from aminoacids

Question 8

Potential energy includes what?

Answer 8

Includes chemical energy stored in molecular structure

Question 9

Free energy

Function?
equation?

Answer 9

• Organisms live by spending (consuming) free energy

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

• The free-energy change (ΔG) of a reaction indicates
whether the reaction occurs spontaneously or not
ΔG = Gfinal - Ginitial

Question 10

Εxergonic reactions:

Answer 10

– Spontaneous reactions

– Free energy released→ ΔG < 0 (negative)

– ΔG = Gfinal - Ginitial => Gfinal < Ginitial

diagram14

Question 11

Εndergonic reactions:

Answer 11

• Absorb free energy from their surroundings (require energy)
• Non-spontaneous reactions → ΔG > 0
• ΔG = Gfinal - Ginitial => Gfinal > Ginitial

diagram15

Question 12

do metabolic pathways reach equilibrum?

Answer 12

no

Question 13

The Structure of ATP?

Function?

Answer 13

• ATP (adenosine triphosphate):
- the cell’s energy shuttle (energy storage and transfer)

• Nucleotide that stores energy in phosphate bonds
• Function: Provides energy for cellular functions
  – energy rich => unstable → tends to break down

diagram17

Question 14

ATP hydrolysis ?

regeneration (synthesis)?

Answer 14

• ATP hydrolysis:
ATP → ADP + Pi => energy release

• ATP synthesis:
ADP + Pi → ATP => energy stored (in
phosphate bonds)

diagram18

Question 15

Energy coupling by ATP

what is Energy coupling?

Three main kinds of endergonic cellular work (require energy
input)?

Answer 15

-ATP powers cellular work by energy coupling

energy coupling: the use of an exergonic process to drive an
endergonic one

(types):
– Mechanical
– Transport
– Chemical

• ATP – mediated energy coupling:
- an endergonic process can by driven by the ATP hydrolysis (exergonic
process)
=> ATP hydrolysis provides the energy required for the endergonic
reaction to occur

Question 16

Exergonic reaction:

How is energy released

Answer 16

Energy is released from ATP when
any of the 2 terminal phosphate bonds are broken

diagram20

Question 17

∆G in

Endergonic reaction:

Exergonic reaction:

Coupled reactions:

Answer 17

• Endergonic reaction: ∆G is positive, reaction is not spontaneous
• Exergonic reaction: ∆G is negative, reaction is spontaneous

-Coupled reactions: Overall ∆G is negative;
together, reactions are spontaneous

Question 18

phosphorylation and ATP

How does ATP affect endrogenic reactions?

Answer 18

• ATP drives endergonic reactions by phosphorylation (transfer of a phosphate to other molecules)

diagram22

Question 19

diagram23***

Answer 19

look!

Question 20

formula
Photosynthesis:

Cellular respiration (aerobic):

Answer 20

CO2 + H20—–) C6H1206 + O2
Carbon dioxide water —–glucose oxygen

Cellular respiration (aerobic):
C6H1206 + Ο2——-) CO2 + H20 + ΑΤP
Glucose oxygen ——-)carbondioxide water
energy

Question 21

diagram25week8*

Answer 21

look

Question 22

Enzymes:

Catalyst:

examples

Answer 22

• Enzymes: catalytic proteins that speed up metabolic
reactions by lowering energy barriers

• Catalyst: a chemical agent that speeds up a reaction
without being consumed by the reaction

• Example: sucrose hydrolysis by sucrase
• Sucrase: the enzyme that catalyzes sucrose hydrolysis

Question 23

The activation energy, EA (4 components)

Answer 23

– The initial amount of energy needed to start a

chemical reaction

Question 24

Enzymes lower the Ea barrier

Enyme affect on reaction?

Answer 24

-By lowering the activation energy (EA) barrier
=> This speeds up the reaction

– The enzyme does not affect whether the reaction will
happen spontaneously or not (without the input of
energy)
– An enzyme will only speed up a reaction that would
occur anyway

Question 25

What is a Substrate example?

Answer 25

Substrate: the reactant an enzyme acts on Example: sucrose is the substrate for sucrase

Question 26

What is Substrate specificity:

Answer 26

``` the enzyme will only recognize its specific substrates (and no other related compounds) ```

Question 27

What is the The active site:

Answer 27

the region on the enzyme where the substrate binds

Question 28

Induced fit of a substrate:

Answer 28

enzyme changes shape upon substrate binding =>brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction

Question 29

Denaturation:

Answer 29

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

Question 30

Environmental factors that may affect enzyme activity:

Answer 30

- pH | - Temperature

Question 31

Cofactors: and what are Inorganic cofactors Coenzymes:

Answer 31

Cofactors: non-protein enzyme helpers Inorganic cofactors: e.g. metal ions Coenzymes: organic cofactors (e.g. vitamins)

Question 32

Each enzyme has an........... in which it can function

Answer 32

optimal temperature

Question 33

Each enzyme as an ........ in which it can | function

Answer 33

optimal pH

Question 34

Irreversible inhibitors: examples?

Answer 34

Irreversible inhibitors: bind to an enzyme by covalent bonding => inhibition is irreversible -Examples: several toxins, antibiotics and poisons – Sarin, DDT, parathion: inhibit nervous system enzymes – Penicillin derivatives: inhibit the enzyme transpeptidase that synthesize the bacterial cell wall peptidoglycan

Question 35

Reversible inhibitors: Types(2)

Answer 35

Reversible inhibitors: bind to enzymes by weak bonds (non-covalent interactions: H-bonds, hydrophobic interactions and ionic bonds) => inhibition is reversible - 2 types of reversible inhibitors: 1. Competitive inhibitors 2. Non-competitive inhibitors

Question 36

Competitive inhibitors: bind to what? function? How can inhibation be overcome?

Answer 36

Competitive inhibitors: bind to the active site of an enzyme (weak binding) • Compete with the substrate => inhibit substrate binding to the active site ``` -Inhibition can be overcome by adding excess substrate ```

Question 37

Non-competitive inhibitors: bind to what? Function? Can inhibition be overcome?

Answer 37

Non-competitive inhibitors: bind to another part of an enzyme not to the active site. Change the shape of the enzyme Inhibit the function of the enzyme -Inhibition cannot be overcome by adding excess substrate

Question 38

Two basic methods of enzyme regulation:

Answer 38

1. Regulation of enzyme production by regulation of gene expression 2. Regulation of enzyme activity by feedback inhibition (by allosteric regulation)

Question 39

diagram44

Answer 39

look

Question 40

In feedback inhibition: whats the end product? Role? Examples (2) ??????????????????????

Answer 40

**Feedback inhibition prevents waste that occurs when more of a product is made than the cell needs. – The end product of a metabolic pathway inhibits the pathway – Role: prevents a cell from wasting chemical resources by synthesizing more product than is needed – Examples: ➢ Inhibition of catabolic pathways by ATP (ATP is the end product) ➢ Inhibition of anabolic pathways by their end product (e.g tryptophan synthesis pathway inhibition by tryptophan)

Question 41

Allosteric Regulation of Enzymes:

Answer 41

– A form of reversible modulation common in enzymes (and proteins) made from polypeptide subunits – can be positive (activation) or negative (inhibition) – a protein’s function (activity) at one site (active site) is affected by binding of a regulatory molecule usually (not always) at another site (regulatory site) ``` – Regulatory molecules bind to regulatory sites via non-covalent binding interactions (similar to reversible non-competitive inhibitors) ``` – Enzyme changes shape when regulatory molecules bind to specific sites, affecting their function – can be heterotropic (regulatory molecules bind to sites other than the active sites) or homotropic (regulatory molecule is the substrate and binds to active sites) *basically non-competitive inhibtors i think

Question 42

Allosteric activators

Answer 42

Allosteric activators stabilize the active form of the enzyme

Question 43

Allosteric inhibitors

Answer 43

Allosteric inhibitors stabilize the inactive form of the enzyme

Question 44

Homotropic allosteric regulation:

Answer 44

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

Question 45

Cooperativity: example

Answer 45

• Cooperativity: special form of positive allosteric regulation (activation) that can amplify enzyme activity – Example: O2 binding to haemoglobin – The binding of substrate (oxygen) at one subunit increases the binding affinity of the other subunits (oxygen= allosteric activator)

Question 46

Allosteric activator

Answer 46

Allosteric activator is the substrate; locks all subunits into active conformation

Question 47

Allosteric regulation summary

Answer 47

• Allosteric inhibitors can be competitive or noncompetitive inhibitors • Heterotropic allosteric modulator (non-competitive inhibitors + activators): - a regulatory molecule that is NOT the enzyme's substrate - Example: - AMP is a heterotropic allosteric activator of PFK (phosphofructokinase) - CO2 is a heterotropic allosteric inhibitor (noncompetitive inhibitor) of haemoglobin => reduces haemoglobin's affinity for oxygen => Oxygen is released in the tissues

Question 48

Homotropic allosteric modulator (competitive | inhibitors + activators):

Answer 48

- both a substrate for its target enzyme and a regulatory molecule of the enzyme's activity. - It is typically an activator of the enzyme (exception: CO for Hb). - Example: O2 and CO are homotropic allosteric modulators of haemoglobin. - O2 is an homotropic allosteric activator of haemoglobin - CO is a competitive inhibitor: binds to haemoglobin at the same site as the oxygen => has higher affinity for Hb than oxygen => does not allow oxygen to be released in tissues.

Question 49

diagram53

Answer 49

look has summary