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topic eight Flashcards

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1
Q

metabolic reactions can be

A

linear (glycolysis) or cyclic (krebs)

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2
Q

How an enzyme lowers the activation energy of a reaction.

A
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3
Q

types of enzyme inhibitors

A

Competitive
Non-competitive.

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4
Q

comp inhibitors

A

competes with the susbtrate for the active site

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5
Q

non comp inhibitors:

A

bind at a site away form the active site, altering the shape of the enzyme

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6
Q

why in competitive inhibition, the maximum rate of reaction (V max ) is eventually the same as the reaction without inhibitor.

A

When the substrate concentration increases, the rate will increase, because there is more available substrate than inhibitor. Therefore, there is a greater chance of the substrate binding to the enzyme’s active site and forming product(s).

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7
Q

why In non-competitive inhibition, the rate levels off and never reaches the same level that it would without inhibitor

A

This difference is caused by the fact that all enzyme molecules to which the inhibitor is attached are effectively blocked from reacting with the substrate due to modification of their active site. Therefore, fewer enzyme molecules (free of inhibitor) are available to catalyse the reaction.

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8
Q

which is chemically similar to the substrate, comp or non comp inhibitor

A

comp

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9
Q

what is an allosteric site

A

a binding site on the surface of an enzyme other than the active site. In the end-product inhibition, the product of the last reaction of an enzyme binds to the allosteric site.

In non-competitive inhibition, when the inhibitor binds to an allosteric site, it blocks the activity of the enzyme.

In an allosteric inhibition, the binding of a regulatory molecule (which is often the end product of the pathway) to the allosteric site changes the overall conformation of the enzyme. This, in turn, can either enable the substrate to bind to the active site or prevent the binding of the substrate.

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10
Q

what is end product inhibition

A

When the end-product of a pathway is no longer needed, it makes sense to stop the reactions at the first step of the pathway

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11
Q

In the pathway that converts threonine to isoleucine, name the enzyme inhibited by the end-product isoleucine.

A

Threonine deaminase

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12
Q

Which of the following is the correct explanation of how databases are used to identify potential new antimalarial drugs?

Databases were used to compare the Plasmodium falciparum genome and protein sequence with those of mosquitoes.

Databases with Plasmodium falciparum genome and protein sequence information were used to screen chemicals for possible interactions before starting lab research.

Databases with Plasmodium falciparum genome and protein sequence information were screened for mutations.

Databases were used to compare the Plasmodium falciparum genome and protein sequence with those of human beings.

A

Databases with Plasmodium falciparum genome and protein sequence information were used to screen chemicals for possible interactions before starting lab research.

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13
Q

In most enzyme-catalysed reactions, you will measure any one of these:

A

The time taken for a particular substrate to be used up
Rate (s -1 ) = 1/ t (where t is the time taken in seconds)

The time taken for a specific product to be made
Rate (s -1 ) = 1/ t (where t is the time taken in seconds)

Amount (mass or volume) of substrate used up over a specific amount of time
the mass or volume can be divided by time to obtain the rate of reaction per second.

Amount (mass or volume) of product made over a specific amount of time.
the mass or volume can be divided by time to obtain the rate of reaction per second.

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14
Q

When plotting a graph of the rate of an enzyme-controlled reaction, what variable should always be plotted on the x-axis (horizontal axis)?

A

independent

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15
Q

oxidation is

A

loss of electrons
loss of hydrogen
gain of oxygen

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16
Q

reduction is

A

gain of electrons
gain of hydrogen
loss of oxygen

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17
Q

phosphorylation

A

adding a phosphate group

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18
Q

two differenet types of phosphorylation

A

substrate and oxidative

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19
Q

What is the purpose of phosphorylation of molecules?

A

To make them more reactive

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20
Q

where is glucose broken down into pyruvate

A

cytoplasm

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21
Q

what is pyruvate converted into in the mitochondrial matrix

A

acetyl coenzyme A (acetyl CoA)

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22
Q

glycolyis yields

A

2 ATP and 2 reducd NADH+H+

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23
Q

at the end of the glycolytic pathway, ??? molecules of pyruvate are formed

A

2

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24
Q

why does the conversion of pyruvate to acetyl coA count as a decarboxylation reaction

A

because carbon is lost as carbon dioxide

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25
why does the conversion of pyruvate to acetyl coA count as a oxidation reaction
pyruvate loses hydrogen
26
what is the link reactin
pyruvate is converted to acetyl coA
27
link reaction
28
Where does glycolysis take place in eukaryotic cells?
Cytoplasm
29
During glycolysis, when each glucose molecule is catalytically broken down to two molecules of pyruvate, most of the potential energy contained in glucose is: Transferred to ADP, forming ATP Transferred directly to ATP Stored in the NADH + H+ produced Retained in the two pyruvates
retained in the two pyruvates
30
why is the krebs scyle sometimes referred to as citric acid cycle
because the first step after the link reaction involves citric acid
31
what are the starting and ending products in citric acid cycle
citrate (6C) to oxoaloacetate (4C)
32
order of resp
glycolysis link reaction krebs cycle
33
what happens to the acertyl group that enters the krebs cycle
successively oxidised as it loses hydrogen atoms and electrons
34
what happens to the hydrogen atoms lost from the acetyl group in the krebs cycle
The hydrogen atoms lost are picked up by hydrogen carriers, either NAD or FAD, which are themselves reduced. Both NAD and FAD are hydrogen acceptor coenzymes that can be reduced by accepting hydrogen.
35
what is the overall yield of one glucose molecule
38 molecules
36
what does one molecule of glucose yield that requires krebs to go twice
two molecules of pyruvate
37
How many carbon atoms are fed into the Krebs cycle as a result of the oxidation of two molecules of pyruvate?
4
38
what can nad and fad do
Both coenzymes are able to carry hydrogen atoms or electrons from one place to another in a cell. The reduced forms of these molecules, in turn, carry the energy released by the oxidation reactions to the cristae of the mitochondria where they give off their electrons
39
The inner mitochondrial membrane is folded to form cristae, which provide an increased
surface area.
40
what is the last protein complex in the etc
cytochrome oxidase
41
what happens to the electrons at cytochrome oxidase
they are combined with oxygen adn hydrogen to form waterw
42
waht is the ultimate electron acceptor
oxygen
43
what is oxidative phosphprylation
the combining of oxygen, hydrogen and electrons to formw ater
44
Since the transfer of electrons along the ETC involves a drop in the energy state of electrons, energy is released. This energy is used to do waht
to pump H + ions across the inner mitochondrial membrane into the intermembrane space.
45
what results in the development of a high concentration of H + in the intermembrane space
the inner mitochondrial membrane is impermeable to protons,
46
The potential energy in the gradient is used by ATP synthase to make
ATP
47
chemiosmosis
involves the pumping of protons (H + ions) into the intermembrane space of the mitochondria by using energy released by electron transport along the ETC, followed by diffusion of protons into the matrix down a concentration gradient through ATP synthase to produce ATP.
48
how many molecules of atp can NADH+H+ give rise to
3
49
how many molecules of atp can FADH2 give rise to
two
50
During aerobic respiration, which sequence do electrons follow?
glucose → NADH → electron transport chain → oxygen
51
mitcohondria structure
52
svedberg units
used to define the size of ribosomes. It is a measurement of sedimentation rate after centrifugation of RNA subunits. The bigger the ribosome, the larger the S value. Therefore 70S is larger than 50S.
53
Small space between inner and outer membranes (intermembrane space) adaptation
Allows fast accumulation of protons needed for chemiosmosis.f
54
fluid matrix containing enzymes adaptation
Enables the link reaction and the Krebs cycle to proceed at an appropriate rate.
55
70S ribosomes adaptation
Synthesises some of the proteins and enzymes needed within the mitochondrion.
56
outer mitochondrial membrane adpatation
Isolates the content of the mitochondrion from the cytoplasm, to allow optimum conditions for reactions of aerobic respiration.
57
Protein-coated, circular DNA adaptation
codes for some of the mitochondrial proteins
58
the light dependent
Photoactivation Photolysis Electron transport chain Chemiosmosis ATP synthesis NADP reduction. all in the intermembrane space
59
The energy generated in the light-dependent reactions of photosynthesis needs to be stored. Again, as is the case with cellular respiration, the energy is transferred to electron carriers, but in the chloroplast, it is in the reduced form of ???
NADP
60
Each NADP molecule accepts ??? hydrogen atoms (i.e. two H + ions and two electrons)
Each NADP molecule accepts two hydrogen atoms (i.e. two H + ions and two electrons)
61
The light-independent reactions, also called the Calvin cycle, take place in the ??? (the cytoplasm of the chloroplast).
stroma
62
light independent reaction steps
Carbon fixation Carboxylation of ribulose bisphosphate (RuBP) Triose phosphate production.
63
Where do the light-independent reactions take place?
Stroma of the chloroplast
64
accessory pigments
any pigment, other than chlorophyll a, that can absorb light. Examples include chlorophyll b and carotenoids.
65
Photosystem I is sensitive to light wavelengths of
700nm
66
Photosystem II is sensitive to light wavelengths of
680 nm
67
photosystem II
68
hwo is activation energy transferred in photosystem II
The chlorophyll molecules in Photosystem II become activated by the photons (photoactivation) of light and pass on their activation energy to the reaction centre, which in turn passes two excited electrons to the primary electron acceptor. This then passes the two electrons to plastoquinone, a hydrophobic electron carrier, which stays inside the thylakoid membrane to pass on the electrons to the next electron carrier; continuing all the way to photosystem I . Photosystem II repeats this one more time, so that, in the end, the reaction centre has lost four electrons that must be replaced before a new cycle can begin.
69
why does the reaction centre in photosynthesis become a powerful oxidising agent
it has lost ofur electrons
70
how can water molecuels be split or lysed to give up their electrosn to the reaction centre
the oxidising reaction centre
71
Photolysis of water generates electrons for use in the ?? reaction, because it constantly replaces electrons lost by Photosystem II.
light dependent
72
Photolysis of water is the
splitting of water molecules into oxygen, hydrogen ions and electrons in the presence of light. Light is not used to split the water molecules directly, but instead causes the loss of electrons from the reaction centre (of Photosystem II), which then acts as an oxidising agent to trigger the reaction.
73
equation for photolysis
2H 2 O → 4H + + 4e − + O 2
74
The electrons lost from the reaction centre are replaced by electrons derived from ???
water
75
why do hydrogen ions quickly accumulate and establish an electrochemical grad
the thylakoid membrnae is impermeable to protons
76
describe photophosphorylation
As excited electrons are transferred along electron carriers, they drop in energy level to return to their stable ground state. This causes a release of energy, which is then used to pump hydrogen ions from the stroma into the thylakoid intermembrane space. As the thylakoid membrane is impermeable to protons, the hydrogen ions quickly accumulate and establish an electrochemical gradient. The proton gradient, resulting from this higher concentration of protons, provides the potential energy for an ATP synthase complex to drive the production of ATP, just like in cellular respiration. As hydrogen ions diffuse through the ATP synthase complex, sufficient energy is released to phosphorylate ADP to ATP. Since this process is ultimately driven by energy derived from photons (particles of light), it is referred to as photophosphorylation .
77
chemiosmosis involves
the pumping of protons (H + ions) into the intermembrane space of thylakoids by using energy released by electron transport along the ETC, followed by diffusion of protons into the stroma down a concentration gradient through ATP synthase to produce ATP.
78
Photosystem I involves similar steps to Photosystem II. The excited electrons received (from Photosystem II) are ultimately transferred to ferredoxin, which in turn reduces NADP to NADPH. Each NADP molecule accepts ???? electrons from Photosystem I and ??? hydrogen ions from the stroma to form NADPH.
two
79
ultimate electron acceptor of the electrons released from photosystem II in the photophosphorylation process
NADPH
80
how is atomospheric co2 fixed
by adding it to ribulose bisphosphate (RuBP). The reaction is catalysed by a large enzyme, ribulose-1,5-bisphosphate carboxylase, commonly referred to as rubisco.
81
where does the calvin cycle take plaec
the stroma, where there is a high conc of rubisco (rubisco is quite slow and calvin cycle is rather inefficent due to its high energy requiremt
82
four phases of the calvin cycle
carbon fixation reduction of glycerate 3 phosphate to triose phosphate release of one molecule of triose phosphate regeneration of ribulose bisphosphate
83
to produce one molecule of triose phosphate that can be used to produce glucose and other carbohydrate requires how many turns of the calvin cycle
3.
84
the calvin cycle
85
The NADPH required for the Calvin cycle comes from
Reactions initiated in photosystem I
86
what did calvin use as starting material for photosynthesis
14CO2
87
calvin lollipop experiment
Radioactive carbon-14 is added to a ‘lollipop’ apparatus containing green algae (Chlorella) Light is shone on the apparatus to induce photosynthesis (which will incorporate the carbon-14 into organic compounds) After different periods of time, the algae is killed by running it into a solution of heated alcohol (stops cell metabolism) Dead algal samples are analysed using 2D chromatography, which separates out the different carbon compounds Any radioactive carbon compounds on the chromatogram were then identified using autoradiography (X-ray film exposure) By comparing different periods of light exposure, the order by which carbon compounds are generated was determined Calvin used this information to propose a sequence of events known as the Calvin cycle (light independent reactions)
88
a single stack of thylakoids is called
a stack
89
waht does the thylakoid membranes being small in volume allow
the proton conc to be as high as possible
90
benefit of large sa of thylakoid membranes
Photosystems I and II, ETC and ATP synthase are embedded
91
what dna do chloroplasts have
circular molecule/bacterial genomea nd fully functioning protein translation machinery 70S
92
adaptation to function of thylakoid and grana
Thylakoids and grana offer a large surface area where photosystems, ETC and ATP synthase are embedded and light-dependent reactions occur.
93
adaptation to function of small thylakoid intermembrane space
The small volume of the thylakoid intermembrane space allows the fast generation of the H + gradient needed for chemiosmosis.
94
adaptation to function of stroma
This contains rubisco, as well as other enzymes, substrates, NADPH and ATP molecules to keep the Calvin cycle turning.
95
adaptation to function of 70S ribosomes
These synthesise some of the proteins and enzymes needed within the chloroplast.
96
adaptation to function of naked dna
This codes for some of the chloroplast proteins.
97
The pH of the thylakoid space has been measured, as have the pH of the stroma and the cytoplasm of a particular plant cell. Which, if any, relationship would you expect to find?
The pH within the thylakoid is lower than that of the stroma, due to the proton conc

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