Bio8 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

8.1 Explain what
metabolic pathways
are

A

• Metabolic pathways consist of chains and cycles
of enzyme-catalysed reactions
metabolism: sum total of all reactions that occur
within an organism in order to maintain life
-chemical changes in a cell result from a series of
reactions (pathways)
-with each step controlled by a specific enzyme
Metabolic pathways allow for a greater level of
regulation:
-the chemical change is controlled by numerous
intermediates
-typically organised into chains or cycles of
enzyme-catalysed reactions
Examples of chains: Glycolysis (in cell respiration),
coagulation cascade (in blood clotting)
Examples of cycles: Krebs cycle (in cell
respiration), Calvin cycle (in photosynthesis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

8.1 Explain the
function of
enzymes.

A

Enzymes lower the activation energy of the chemical reactions that they
catalyse
-enzyme binds to a substrate -> stresses and destabilises the bonds in the
substrate
-the substrate binds to the active site and is altered to reach the transition state
-it is then converted into the products, which separate from the active site.
-reduces the overall energy level of the substrate’s transitionary state
-the activation energy of the reaction is therefore reduced. (The net amount of
energy released by the reaction is unchanged by the involvement of the
enzyme.)
-so less energy is needed to convert it into a product and the reaction
proceeds at a faster rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

8.1 Explain enzyme
inhibition.

A

• Enzyme inhibitors can be competitive or non-
competitive
enzyme inhibitor: a molecule that disrupts the
normal reaction pathway between an enzyme and
a substrate
-prevent the formation of an enzyme-substrate
complex and hence prevent the formation of
product
**may be either reversible or irreversible
depending on the specific effect of the inhibitor
being used
Competitive Inhibition
-involves a molecule, other than the substrate,
binding to the enzyme’s active site
-inhibitor is structurally and chemically similar to
the substrate (hence able to bind to the active
site)
-competitive inhibitor blocks the active site and
thus prevents substrate binding
-as the inhibitor is in competition with the
substrate, its effects can be reduced by increasing
substrate concentration
Noncompetitive Inhibition
-involves a molecule binding to a site other than
the active site (an allosteric site)
-binding of the inhibitor to the allosteric site
causes a conformational change to the enzyme’s
active site
-the active site and substrate no longer share
specificity, meaning the substrate cannot bind
-as the inhibitor is not in direct competition with
the substrate, increasing substrate levels cannot
mitigate the inhibitor’s effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

8.1 Identify one
specific example
for competitive and
non-competitive
inhibition and
explain it.

A

Relenza (Competitive Inhibitor)
-a synthetic drug designed by Australian scientists
to treat individuals infected with the influenza
virus
-virions are released from infected cells when the
viral enzvme neuraminidase cleaves a docking
protein (haemagglutinin)
-relenza competitivelv binds to the neuraminidase
active site and prevents the cleavage of the
docking protein
-virions are not released from infected cells,
preventing the spread of the influenza virus
Cyanide (Noncompetitive Inhibitor)
-cyanide is a poison which prevents ATP
production via aerobic respiration -> eventual
death
-it binds to an allosteric site on cytochrome
oxidase - a carrier molecule that forms part of the
electron transport chain
-by changing the shape of the active site,
cytochrome oxidase can no longer pass electrons
to the final acceptor (oxygen)
-the electron transport chain cannot continue to
function and ATP is not produced via aerobic
respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

8.1 Explain how
metabolic pathways
can be controlled
and provide an
example.

A

• Metabolic pathways can be controlled by end-
product inhibition
End-product inhibition: a form of negative
feedback by which metabolic pathways can be
controlled
-the final product in a series of reactions inhibits
an enzyme from an earlier step in the sequence
-product binds to an allosteric site and
temporarily inactivates the enzyme (non-
competitive inhibition)
-enzyme can no longer function -> reaction
sequence is halted -> rate of product formation is
decreased
**functions to ensure levels of an essential
product are always tightly regulated
-product levels build up -> inhibition -> decreases
the rate of further product formation
-product levels drop -> reaction pathway
proceeds -> the rate of product formation will
increase
• End-product inhibition of the pathway that
converts threonine to isoleucine
Isoleucine: an essential amino acid = not
synthesised by the body in humans (and hence must be ingested)
-in plants and bacteria, isoleucine may be
synthesised from threonine in a five-step reaction
pathway
-in lst step: threonine is converted into an
intermediate compound by an enzyme (threonine
deaminase)
-isoleucine can bind to an allosteric site on this
enzyme and function as a non-competitive
inhibitor
-excess production of isoleucine inhibits further
synthesis, it functions as an example of end-
product inhibition
-feedback inhibition ensures that isoleucine
production does not cannibalise available stocks
of threonine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

8.1 Application: Use
of databases to
identify potential
new anti-malarial
drugs.

A

Malaria is a disease caused by parasitic
protozoans of the genus Plasmodium
the disease is transmitted via mosquito bites
-maturation and development of the parasite in
both human and mosquito host is coordinated by
specific enzymes
-targeting these enzymes for inhibition, new anti-
malarial drugs and medications can be produced
Scientists have sequenced the genome of
infectious species of Plasmodium and used it to
determine the parasite’s proteome
-enzymes involved in parasitic metabolism have
been identified as potential targets for inhibition
-enzymes may be screened against a
bioinformatic database of chemicals to identify
potential enzyme inhibitors
-promising compound identified -> chemically
modified to improve its binding affinity and lower
its toxicity
An alternative method by which potential new
anti-malarial medications can be synthesised is via
rational drug design
-involves using computer modelling techniques to
invent a compound that will function as an
inhibitor
-using combinatorial chemistry, a compound is
synthesised that is complementary to the active
site of the target enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

8.2 Give a general
account on how
energy in ATP is
converted for
cellular usage

A

• Phosphorylation of molecules makes them less
stable
D
phosphorylation: the addition of phosphate to an
organic compound.
-one ATP contains three covalently bonded
phosphate groups (potential energy stored in
bonds)
-phosphorylation makes molecules less stable
and hence ATP is a readily reactive molecule that
contains high energy bonds
-When ATP is hydrolysed (to form ADP + Pi), the
energy stored in the terminal phosphate bond is
released for use by the cell
ATP is synthesised from ADP using energy
derived from one of two sources:
-solar energy - photosynthesis converts light
energy into chemical energy that is stored as ATP
-oxidative processes - cell respiration breaks
down organic molecules to release chemical
energy that is stored as ATP
**

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

8.2 Explain
glycolysis in cellular
respiration.

A

• In glycolysis, glucose is converted into pyruvate
in the cytoplasm
-a hexose sugar (6C) is broken down into two
molecules of pyruvate (3C)
1. Phosphorylation
-hexose sugar (typically glucose) is
phosphorylated by two molecules of ATP (to
form a hexose bisphosphate)
-makes the molecule less stable and more
reactive, and also prevents diffusion out of the
cell
-glucose + 2P
2. Lysis
-hexose biphosphate (6C sugar) is split into two
triose phosphates (3C sugars)
3. Oxidation
-H atoms are removed from each of the 3C
sugars (via oxidation) to reduce NAD+ to NADH (+
H+)
-2 molecules of NADH are produced in total (one
from each 3C sugar)
4. ATP formation
-some energy released from the sugar intermediates is used to directly synthesise ATP
-direct synthesis of ATP is called substrate level
phosphorylation
-in total, 4 molecules of ATP are generated
during glycolysis by substrate level
phosphorylation (2 ATP per 3C sugar)
At the end of glycolysis, the following reactions
have occurred:
-glucose (6C) has been broken down into two
molecules of pyruvate (3C)
-two hydrogen carriers have been reduced via
oxidation (2 × NADH + H+)
-net total of two ATP molecules have been
produced (4 molecules were generated, but 2
were used)
• Glycolysis gives a small net gain of ATP without
the use of oxygen
-no 02 = pyruvate is not broken down further and
no more ATP is produced (incomplete oxidation)
-pyruvate remains in the cytosol and is converted
into lactic acid (animals) or ethanol and CO2
(plants and yeast)
-this conversion is reversible and is necessary to ensure that glycolysis can continue to produce
small quantities of ATP
-glycolysis involves oxidation reactions that cause
hydrogen carriers (NAD+) to be reduced
(becomes NADH + H+)
-the reduced hydrogen carriers are oxidised via
aerobic respiration to restore available stocks of
NAD+In the absence of oxygen
-glycolysis will quickly deplete available stocks of
NAD*, preventing further glycolysis
-fermentation of pyruvate involves a reduction
reaction that oxidises NAH (releasing NAD+ to
restore available stocks)
-hence, anaerobic respiration allows small
amounts of ATP to be produced (via glycolysis) in
the absence of oxygen
• Energy released by oxidation reactions is carried
to the cristae of the mitochondria by reduced
NAD and FAD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

8.2 Explain the link
reaction

A

• In link reaction pyruvate is decarboxylated and
oxidised, and converted into acetyl compound
and attached to coenzyme A to form acetyl
coenzyme A in the link reaction

Ist stage of aerobic respiration is the link reaction,
which transports pyruvate into the mitochondria.
-pyruvate is transported from the cytosol into the
mitochondrial matrix by carrier proteins on the
mitochondrial membrane
-pyruvate loses a carbon atom (decarboxylation),
which forms a carbon dioxide molecule
-2C compound then forms an acetyl group when
it loses hydrogen atoms via oxidation (NAD+ is
reduced to NADH + H+)
-acetyl compound then combines with coenzyme
A to form acetyl coenzyme A (acetyl CoA)
the link reaction occurs twice per molecule of
glucose
-per glucose molecule, the link reaction produces
acetyl COA (×2), NADH + H+ (
2) and CO2 (
2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

8.2 Explain the
Krebs Cycle.

A

• In the Krebs cycle, the oxidation of acetyl
groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide
-acetyl CoA transfers its acetyl group to a 4C
compound to make a 6C compound
-coenzyme A is released and can return to the
link reaction to form another molecule of acetvl
COA
-over a series of reactions, the 6C compound is
broken down to reform the original 4C
compound (hence, a cycle)
-2 carbon atoms are released via decarboxvlation
to form two molecules of carbon dioxide (CO2)
-multiple oxidation reactions result in the
reduction of hydrogen carriers (3 × NADH + H+ ; 1
× FADH2)
-1 molecule of ATP is produced directly via
substrate level phosphorylation
**the Krebs cycle occurs twice
Per glucose molecule, the Krebs cycle produces:
4x CO2 ;
2× ATP :
6* NADH + H+ ;
2× FADH2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

8.2 Explain the
processes in the
electron transport
chain.

A

• Transfer of electrons between carriers in the
electron transport chain in the membrane of the
cristae is
coupled to proton pumping.
-hydrogen carriers donate high energy electrons
to the ETC (located on the cristae)
-as the electrons move through the chain they
lose energy, which is transferred to the electron
carriers within the chain
-the electron carriers use this energy to pump
hydrogen ions from the matrix and into the
intermembrane space
-accumulation of H+ ions in the intermembrane
space creates an electrochemical gradient (or a
proton motive force)
-H+ ions return to the matrix via the
transmembrane enzyme ATP synthase (this
diffusion of ions is called chemiosmosis)
-as the ions pass through ATP synthase they
trigger a phosphorylation reaction which
produces ATP (from ADP + Pi)
• Oxygen is needed to bind with the free protons
to maintain the hydrogen gradient, resulting in the
formation of water
-de-energised electrons are removed from the chain by oxygen, allowing new high energy
electrons to enter the chain
-02 also binds matrix protons to form water - this
maintains the hydrogen gradient by removing H+
ions from the matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

8.2 Skill: Analysis of
diagrams of the
pathways of
aerobic respiration
to deduce where
decarboxylation
and oxidation
reactions occur

A

Decarboxylation:
-C atoms are removed from the organic molecule
(glucose) to form carbon dioxide
-2 in Link reaction and 4 in Krebs
Oxidation:
-e- and H+ are removed from glucose and taken
up by hydrogen carriers (NADH and FADH2)
-2 NADH in glycolysis
-2 NADH in link reaction
-6 NADH and 2 FADH2 in Krebs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

8.2 Skill: Annotation
of a diagram of a
mitochondrion to
indicate the
adaptations to its
function.
List out the
structures of the
mitochondria and its
adaptations.

A

• The structure of the mitochondrion is adapted to
the function it performs
-eukarvotic cells possess mitochondria - aerobic
prokaryotes use the cell membrane to perform
oxidative phosphorylation
-outer membrane - the outer membrane contains
transport proteins that enable the shuttling of
pyruvate from the cytosol
-inner membrane - contains the electron transport
chain and ATP synthase (used for oxidative
phosphorylation)
-cristae - the inner membrane is arranged into
folds (cristae) that increase the SA:Vol ratio (more
available surface)
-intermembrane space - small space between
membranes maximises hydrogen gradient upon
proton accumulation
-matrix - central cavity that contains appropriate
enzymes and a suitable pH for the Krebs cycle to
Occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

8.3 Outline the
process of
photosynthesis.

A

Photosynthesis is a two-step process:
• Light dependent reactions take place in the
intermembrane space of the thvlakoids
• Light independent reactions take place in the
stroma.
Step 1: LDR
-light is absorbed by chlorophyll, which releases
energised electrons that are used to produce ATP
(chemical energy)
-electrons are donated to carrier molecules
(NADP+), which is used (along with ATP) in the
light independent reactions
-electrons lost from the chlorophyll are replaced
by water, which is split (photolysis) to produce
oxygen and hydrogen
Step 2: Light Independent Reactions
-ATP and hydrogen / electrons (carried by
NADPH) are transferred to the site of the light
independent reactions
-hydrogen / electrons are combined with carbon
dioxide to form complex organic compounds
(e.g. carbohydrates)
-ATP provides the required energy to power
these anabolic reactions and fix the carbon
molecules together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

8.3 Outline light
dependent reaction
in photosynthesis.

A

-light dependent reactions occur within the
intermembrane space of the thylakoids
-chlorophyll in Photosystems I and Il absorb light,
which triggers the release of high energy
electrons (photo activation)
-excited electrons from Photosystem Il are
transferred between carrier molecules in an
electron transport chain
-electron transport chain translocates H+ ions
from the stroma to within the thylakoid, creating a
proton gradient
-the protons are returned to the stroma via ATP
synthase, which uses their passage (via
chemiosmosis) to synthesise ATP
-excited electrons from Photosystem I are used to
reduce NAD+ (forming NADPH)
-electrons lost from Photosystem I are replaced
by the de-energised electrons from Photosystem
Il
-electrons lost from Photosystem Il are replaced
following the photolysis of water
-products of the light dependent reactions (ATP
and NADPH) are used in the light independent
reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

8.3 Explain light
dependent reaction
in photosynthesis.

A

-excitation of photosystems by light energy
-production of ATP via an electron transport
chain
-reduction of NAD+ and the photolysis of water
-light dependent reactions use photosynthetic
pigments (organised into photosystems) to
convert light energy into chemical energy
(specifically ATP and NADPH)
• Absorption of light by photosystems generates
excited electrons
• Transfer of excited electrons occurs between
carriers in thylakoid membranes
Step 1: Excitation of Photosystems by Light Energy
-photosystems are groups of photosynthetic
pigments (including chlorophyll) embedded within
the thylakoid membrane
-photosystems are classed according to their
maximal absorption wavelengths (PS I = 700 nm ;
PS I| = 680 nm)
-when a photosystem absorbs light energy,
delocalised electrons within the pigments become
energised or ‘excited’
-excited electrons are transferred to carrier
molecules within the thylakoid membrane
Excited electrons from Photosvstem I are used to contribute to generate a proton gradient
• ATP synthase in thylakoids generates ATP using
the proton gradient
Step 2: Production of ATP via an Electron
Transport Chain
-excited electrons from Photosystem I (P680) are
transferred to an electron transport chain within
the thylakoid membrane
-as the electrons are passed through the chain
they lose energy, which is used to translocate H+
ions into the thylakoid
-build up of protons within the thylakoid creates
an electrochemical gradient, or proton motive
force
-H+ ions return to the stroma (along the proton
gradient) via the transmembrane enzyme ATP
synthase (chemiosmosis)
-ATP synthase uses the passage of H+ ions to
catalyse the synthesis of ATP (from ADP + Pi)
-above process is photophosphorylation - as light
provided the initial energy source for ATP
production
-newly de-energised electrons from Photosystem
Il are taken up by Photosystem I
• Excited electrons from Photosystem I are used to reduce NADP
• Photolysis of water generates electrons for use
in the light dependent reactions
Step 3: Reduction of NAD+ and the Photolysis of
Water
-excited electrons from Photosystem I may be
transferred to a carrier molecule and used to
reduce NADP+
-forms NADPH - which is needed (in conjunction
with ATP) for the light independent reactions
-electrons lost from Photosystem I are replaced
by de-enerqised electrons from Photosystem Il
-electrons lost from Photosystem Il are replaced
by electrons released from water via photolysis
-H2O is split by light energy into H+ ions (used in
chemiosmosis) and oxygen (released as a by-
product)
• Reduced NAD and ATP are produced in the
light dependent reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

8.3 Explain
photophosphorylation.

A

• Photophosphorylation may be either a cyclic
process or a non-cyclic process
Cyclic:
-involves the use of only one photosystem (PS 1)
and does not involve the reduction of NADP+
-when light is absorbed by Photosystem I, the
excited electron may enter into an electron
transport chain to produce ATP
-the de-energised electron returns to the
photosystem, restoring its electron supply (hence:
cyclic)
-electron returns to the photosystem, so NAD+ is
not reduced and water is not needed to replenish
the electron supply
Non-Cyclic
-involves two photosystems (PS I and PS I) and
the reduction of NADP+
-light is absorbed by Photosystem Il, the excited
electrons enter into an electron transport chain to
produce ATP
-photoactivation of Photosystem I results in the
release of electrons which reduce NAD+ (forms
NADPH)
-photolysis of water releases electrons which
replace those lost by Photosystem Il (PS I
electrons replaced by PS I1)
-cyclic photophosphorylation can be used to
produce a steady supply of ATP in the presence
of sunlight
-non-cyclic photophosphorylation produces
NADPH in addition to ATP (this requires the
presence of water)
**only non-cyclic photophosphorylation allows
for the synthesis of organic molecules and long
term energy storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

8.3 Explain light
independent
reactions.

A

-carboxylation of ribulose bisphosphate
-reduction of glycerate-3-phosphate
-regeneration of ribulose bisphosphate
• In the light independent reactions a carboxylase
catalvses the carboxvlation of ribulose
bisphosphate
Step 1: Carbon Fixation
-Calvin cycle begins with a 5C compound called
ribulose bisphosphate (or RUBP)
-enzyme, RUBP carboxylase (or Rubisco),
catalyses the attachment of a CO2 molecule to
RUBP
-resulting 6C compound is unstable, and breaks
down into two 3C compounds - called
glycerate-3-phosphate (GP)
A single cycle involves three molecules of RuBP
combining with three molecules of CO2 to make
six molecules of GP
• Glycerate-3-phosphate is reduced to triose
phosphate using reduced NAP and ATP
Step 2: Reduction of Glycerate-3-Phosphate
-reduction by NADPH transfers hydrogen atoms
to the compound, while the hydrolysis of ATP
provides energy
-each GP requires one NADPH and one ATP to form a triose phosphate - so a single cycle
requires six of each molecule
• Triose phosphate is used to regenerate RUBP
and produce carbohydrates
• Ribulose bisphosphate is reformed using ATP
Step 3: Regeneration of RuBP
-of the six molecules of TP produced per cycle,
one TP molecule may be used to form half a
sugar molecule
-two cycles are required to produce a single
glucose monomer, and more to produce
polysaccharides like starch
-remaining five TP molecules are recombined to
regenerate stocks of RuBP (5 × 3C = 3 × 5C)
-regeneration of RuB requires energy derived
from the hydrolysis of ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

8.3 Skill: Annotation
of a diagram to
indicate the
adaptations of a
chloroplast to its
function.
Explain the
structure of the
chloroplast is
adapted to its
function in
photosynthesis

A

-chloroplasts are the “solar energy plants’ of a
cell - they convert light energy into chemical
energy
The structure of the chloroplast is adapted to the
function it performs:
-thylakoids - flattened discs have a small internal
volume to maximise hydrogen gradient upon
proton accumulation
-grana - thylakoids are arranged into stacks to
increase SA: Vol ratio of the thylakoid membrane
-photosystems - pigments organised into
photosystems in thylakoid membrane to maximise
light absorption
-stroma - central cavity that contains appropriate
enzymes and a suitable pH for the Calvin cycle to
occur
-lamellae - connects and separates thylakoid
stacks (grana), maximising photosynthetic
efficiency

20
Q

8.3 Explain the
Lollipop
experiment.

A

-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)

21
Q

8.1 Contrast
metabolic chain
reaction pathways
with cyclical
reaction pathways.

A

-most chemical changes in a cell result from a
series of reactions (pathways), with each step
controlled by a specific enzyme
-metabolic pathways allow for a greater level of
regulation, as the chemical change is controlled
by numerous intermediates
-some metabolic pathways form a cycle rather
than a chain.
-in this type of pathway, the end product of one
reaction is the reactant that starts the rest of the
pathway.

22
Q

8.1 Define enzyme
inhibitor

A

Substances that bind to enzymes and lower their
activity.

23
Q

8.1 Outline the
mechanism and
benefit of end-
product inhibition.

A

-allows the concentration of the end-product
produced to be controlled, it would be wasteful
to continue making a substance that is not
needed.
-reactions often do not go to completion.
-instead, an equilibrium position is reached with a
characteristic ratio of substrates and products.
-so, if the concentration of products increases, a
reaction will eventually slow down and stop.
-this effect reverberates back through a metabolic pathway when the end product
accumulates, with all the intermediates
accumulating.
-end-product inhibition prevents this build-up of
intermediate products.

24
Q

8.1 State the
consequence of an
increase in
isoleucine
concentration.

A

As the concentration of isoleucine builds up, it
binds to the allosteric site of the first enzyme in
the chain, threonine deaminase, thus acting as a
non-competitive inhibitor

25
Q

8.1 Outline the
reasons for
development of
new anti-malarial
drugs.

A

-(Malaria is a disease caused by the pathogen
Plasmodium falciparum.)
-the increasing resistance of P. falciparum to anti-
malarial drugs such as chloroquine
-the dependence of all new drug combinations on
a narrow range of medicines and increasing
global efforts to eradicate malaria all drive the
need to develop new anti-malarial drugs

26
Q

8.1 Explain the use
of databases in
identification of
potential new anti-
malarial drugs.

A

Plasmodium falciparum strain 3D7 is a variety of
the malarial parasite for which the genome has
been sequenced

27
Q

8.1 State two
methods for
determining the rate
of enzyme
controlled
reactions.

A

-measuring the rate of disappearance of a
substrate or the rate of appearance of a product.
Example: use iodine to test the presence of starch
as iodine turns blue/black if starch is present.
Have one drop of iodine into each well.
Every 30 seconds, place a drop of the starch
buffer solution into the iodine solution.
Continue until there is no colour change of the
iodine solution when combined with the buffer
solution.

28
Q

8.1 Outline the use
and benefits of the
bioinformatics
technique of
chemogenomics in
development of
new pharmaceutical
drugs.

A

-bioinformatics is an approach whereby multiple
research groups can add information to a
database enabling other groups to query the
database.
-one promising bioinformatics technique that has
facilitated research into metabolic pathways is
referred to as chemogenomics.
-sometimes when a chemical binds to a target site,
it can signifcantly alter metabolic activity.
-scientists looking to develop new drugs test
massive libraries of chemicals individually on a
range of related organisms.
-for each organism a range of target sites are
identified and a range of chemicals which are
known to work on those sites are tested.

29
Q

8.2 Define “electron
carrier.”

A

Electron carriers are molecules that can accept or
donate electrons.

30
Q

8.2 Define
phosphorylation.

A

The addition of a phosphate group, typically from
ATP. (catalysed by kinases)

31
Q

8.2 Glycolysis is an
example of a
metabolic

A

Glycolysis is an example of a metabolic pathway.

32
Q

8.2 Define oxidative
phosphorylation
and chemiosmosis.

A

Oxidative phosphorylation is where energy ‘
originally released from the oxidation of glucose
is used to produce ATP from ADP and Pi.
Chemiosmosis is the use of the energy held within
the proton gradient (created by the transport of
electrons by the electron transport chain) to
produce ATp

33
Q

8.2 Outline Peter
Mitchell’s proposal
of the chemiosmotic
hypothesis.

A

Peter Mitchell’s proposal of the chemiosmotic
hypothesis in 1961 lead to a major shift in our
understanding of cellular processes.
-explains the coupling of electron transport in the
inner mitochondrial membrane to ATP synthesis.
-his hypothesis was a radical departure from
previous hypotheses and only after many years
was it generally accepted

34
Q

8.3 List the type of
reactions that occur
in the light
dependent reaction
of photosynthesis.

A

The light dependent reactions of
photosynthesis include:
Photoactivation
Photolysis
Electron transport
Chemiosmosis
ATP synthesis
Reduction of NADP to NADPH + H+

35
Q

8.3 List the type of
reactions that occur
in the light
independent
reaction of
photosynthesis

A

Light independent reactions of
photosynthesis include:
Carbon fixation
Carboxylation of RUBP
Production of triosphosphate
ATP and NADPH as energy sources
ATP used to regenerate RUBP
* ATP used to produce carbohydrates

36
Q

8.3 Define
photosvstem and
reaction center.

A
  • Photosystems are chlorophyll molecules and
    other accessory pigments which are organized
    into photosystems.
    Reaction center: a complex of several proteins,
    pigments and other co-factors that together
    execute the primary energy conversion reactions
    of photosynthesis
37
Q

8.3 Outline the role
of plastoquinone in
light dependent
reaction.

A

-a hydrophobic electron carrier
-stays inside the thylakoid membrane to pass on
the electrons to the next electron carrier;
continuing all the way to photosystem I.
-in photoactivation at Photosystem II, the reaction
center chlorophyll is oxidized and the
plastoquinone (Pq) is reduced
-electrons pass from plastoquinone (Pq) through
a chain of electron carrier molecules.

38
Q

8.3 Define carbon
fixation and
carboxylation.

A

Carbon fixation: the process by which inorganic
carbon (particularly in the form of carbon
dioxide) is converted to organic compounds by
living organisms.
eq carbon dioxide is converted into another
carbon compound
Carboxylation: a chemical reaction in which a
carboxylic acid group is produced by treating a
substrate with carbon dioxide.
e.g. the reaction in which carbon dioxide reacts
with RUBP to produce an unstable six carbon
compound

39
Q

8.3 List areas in
photosynthesis
where carbon
fixation and
carboxylation
occured

A

-carbon fixation occurs in the chloroplast stroma.

-the 5-carbon molecule ribulose bisphosphate
(RUBP) is carboxylated by CO2, forming 2 3-
carbon molecules called glycerate-3-phosphate
(G3P).
-the enzyme that catalyzes the carboxylation of
RUBP is called ribulose bisphosphate carboxylase
(rubisco).*

40
Q

8.3 Explain the role
of the ATP formed
in the light
dependent reaction.

A

ATP (from the light dependent reaction) provides
the energy for NADPH (from the light dependent
reaction) to reduce G3P, forming a three carbon
carbohydrate, triose phosphate.
ATP is used to regenerate RUBP from triose
phosphate.

41
Q

8.3
turns of the
Calvin Cycle are
needs to produce
one molecule of
glucose.

A

two turns of the Calvin Cycle are needs to
produce one molecule of glucose.

42
Q

8.3 Outline how
chloroplast
structure could
evolve through
natural selection.

A

-if the structure of chloroplasts varied, those
organisms with the chloroplast that absorbed light
and converted it into glucose most efficiently
would have the advantage.
-they would have an increased chance of survival
and would tend to produce more offspring.
-these offspring would inherit the type of
chloroplast that produces glucose using light
energy more efficiently.
-if this trend continued, the structure of the
chloroplast would gradually evolve to become
more and more efficient.
-(Chloroplasts are quite variable in structure but
share certain features):
A double membrane forming the outer
chloroplast envelope.
An extensive system of internal membranes called
thylakoids, which are an intense green colour.
Small fluid filled spaces inside the thylakoids.
A colorless fluid around the thylakoids called
stroma that contains many different enzymes.
In most chloroplasts there are stacks of
thylakoids, called grana.
If a chloroplast has been photosynthesising
rapidly then there may be starch grains or lipid
droplets in the stroma.

43
Q

8.3 Explain Calvin’s
experiment and
what was
discovered about
photosynthesis
through his work.

A

a. Calvin cycle is light-independent
b. carbon fixation OR carboxylation of ribulose
bisphosphate/RUBP occurs
c. algae placed in thin glass container/”lollipop”
apparatus/
d. given plenty of light and bicarbonate/ CO2
e. at start of experiment algae supplied
radioactive carbon/HCO3 - / 14C V
f. samples taken at intervals / heat/alcohol killed
samples
g. C-compounds separated by chromatography
h. 14C/radioactive-compounds identified by
autoradiography
i. showed that RUBP was phosphorylated
j. after five seconds/immediately more
glycerate-3-phosphate/3-PGA labelled than any
other compound k. shows glycerate-3-
phosphate/3-PGA first «carboxylated»
compound/the first stable product
I. next compound to be detected containing
radioactive carbon was triose phosphate/ G3P/
glyceraldehyde3 phosphate
m. showed that a wide range of carbon
compounds was quickly made in sequence
n. showed that a cycle of reactions was used to
regenerate RuBP

44
Q

8.3 Outline Calvin’s
“lollipop”
experiment,
including the role
Of.
Radioactive
carbon-14
Green algae
Air with CO2
Light
Varying the time
of light exposure
Heated alcohol
Chromatography
Autoradiography

A

-Calvin used algae suspended in a solution.
-the vessel containing the algae had a lollipop
shape; it was a thing, round, glass vessel.
-this ensured all the algae had equal light.
-air was bubbled through the vessel.
-a short burst of 14CO2 was supplied.
-every few seconds, samples of algae were taken
and added to hot methanol.
-khis kills the algae, stopping the light-
independent reactions.
-the samples were seperated by two-dimensional
paper chromatography and visualized by
autoradiography.
-by analyzing autoradiograms of samples
stopped at different times after the addition of
14C02, Calvin could follow the pathway taken by
14C.
-in the first sample, the most abundant compound
was glycerate-3-phosphate, indicating this is the
first product.
-he determined the order of the complete cycle.

45
Q

8.3 State the role of
a starch grain.

A

An insoluble form of glucose produced by
photosynthesis. Starch is the form that glucose is
transported around the plant as.