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week 8 Flashcards

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1
Q

The Energy of Life.

name all components (5)

A

• 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)

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2
Q

Energy flow on Earth.

Steps

A

• Sun → Producers → Consumers, decomposers

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3
Q

What is Metabolism

A

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

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4
Q

Metabolic Pathways

A

• 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

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5
Q

pic page 6

A

week 8

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6
Q

Catabolic pathways

A

• Release energy**

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

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7
Q

Anabolic pathways

A

• Consume energy**

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

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8
Q

Potential energy includes what?

A

Includes chemical energy stored in molecular structure

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9
Q

Free energy

Function?
equation?

A

• 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

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10
Q

Εxergonic reactions:

A

– Spontaneous reactions

– Free energy released→ ΔG < 0 (negative)

– ΔG = Gfinal - Ginitial => Gfinal < Ginitial

diagram14

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11
Q

Εndergonic reactions:

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

diagram15

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12
Q

do metabolic pathways reach equilibrum?

A

no

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13
Q

The Structure of ATP?

Function?

A

• 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

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14
Q

ATP hydrolysis ?

regeneration (synthesis)?

A

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

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

diagram18

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15
Q

Energy coupling by ATP

what is Energy coupling?

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

A

-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

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16
Q

Exergonic reaction:

How is energy released

A

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

diagram20

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17
Q

∆G in

Endergonic reaction:

Exergonic reaction:

Coupled reactions:

A
  • 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

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18
Q

phosphorylation and ATP

How does ATP affect endrogenic reactions?

A

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

diagram22

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19
Q

diagram23***

A

look!

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20
Q

formula
Photosynthesis:

Cellular respiration (aerobic):

A

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

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

21
Q

diagram25week8*

A

look

22
Q

Enzymes:

Catalyst:

examples

A

• 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
23
Q

The activation energy, EA (4 components)

A

– The initial amount of energy needed to start a

chemical reaction

24
Q

Enzymes lower the Ea barrier

Enyme affect on reaction?

A

-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

25
Q

What is a Substrate

example?

A

Substrate: the reactant an enzyme acts on

Example: sucrose is the substrate for sucrase

26
Q

What is Substrate specificity:

A 
the enzyme will only recognize its
specific substrates (and no other related compounds)
27
Q

What is the The active site:

A

the region on the enzyme where the substrate binds

28
Q

Induced fit of a substrate:

A

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

29
Q

Denaturation:

A

the loss of a protein’s native conformation

due to unravelling => loss of function

30
Q

Environmental factors that may affect enzyme activity:

A
  • pH

- Temperature

31
Q

Cofactors:
and what are Inorganic cofactors

Coenzymes:

A

Cofactors: non-protein enzyme helpers
Inorganic cofactors: e.g. metal ions

Coenzymes: organic cofactors (e.g. vitamins)

32
Q

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

A

optimal temperature

33
Q

Each enzyme as an …….. in which it can

function

A

optimal pH

34
Q

Irreversible inhibitors:

examples?

A

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

35
Q

Reversible inhibitors:

Types(2)

A

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
36
Q

Competitive inhibitors:
bind to what?
function?

How can inhibation be overcome?

A

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
37
Q

Non-competitive inhibitors:
bind to what?
Function?

Can inhibition be overcome?

A

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

38
Q

Two basic methods of enzyme regulation:

A
  1. Regulation of enzyme production by
    regulation of gene expression
  2. Regulation of enzyme activity by feedback
    inhibition (by allosteric regulation)
39
Q

diagram44

A

look

40
Q

In feedback inhibition:

whats the end product?
Role?
Examples (2)
??????????????????????

A

**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)

41
Q

Allosteric Regulation of Enzymes:

A

– 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

42
Q

Allosteric activators

A

Allosteric activators
stabilize the active
form of the enzyme

43
Q

Allosteric inhibitors

A

Allosteric inhibitors
stabilize the inactive
form of the enzyme

44
Q

Homotropic allosteric regulation:

A

Binding of substrate to active site

of one subunit locks all subunits into active conformation

45
Q

Cooperativity:

example

A

• 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)

46
Q

Allosteric activator

A

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

47
Q

Allosteric regulation summary

A

• 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
48
Q

Homotropic allosteric modulator (competitive

inhibitors + activators):

A
  • 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.
49
Q

diagram53

A

look has summary

Biology (5 decks)

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