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HL Biology - topical sets > Topic 8 > Flashcards

Topic 8 Flashcards

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1
Q

Benefits of metabolic pathway

A
  • intermediates formed -> controlled reaction
  • not a lot of energy lost via heat -> smaller reactions (check this point though)
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2
Q

How enzymes work + types of enzymatic reactions

A
  • enzyme binds to subs –> stresses and destabilises bonds -> lower Ea

Types:

  1. Endergonic: in anabolic reactions -> free energy from surr to sys -> energy needed to form bonds between molecules
  2. Exergonic: in catabolic reactions -> free energy from system to surroundings, energy released when bonds broken
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3
Q

Competitive v Non competitive enzyme inhibition (MS based)

A
  • C: inhibitor binds to active site, NC: allosteric site
  • C: increasing subs [] may overpower the effect of inhibitor; NC: inc subs [] has no effect -> the subs cannot bind to many enzymes anymore
  • C: Inh complementary shape to AS, similar shape to subs; NC: not
  • C: subs binding prevented because inh occupies AS; NC: Subs binding prevented bc inh changes the AS
  • C: pharma use; NC: end-product inhibitor use
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4
Q

Competitive inhibition example

A
  • Relenza inhibitor of influenza patients
  • viruses release virions from infected cells -> enzyme neuraminidse cleaves docking protein
  • relenza binds to neuraminidase AS competitively -> prevents cleavage -> no virions released
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5
Q

NC inhibition example

A
  • cyanide
  • prevents aerobic respiration -> cause eventual death
  • binds to cytochrome oxidase allosteric site
  • ## prevents it from functioning in the ETC
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5
Q

NC inhibition example

A
  • cyanide
  • prevents aerobic respiration -> cause eventual death
  • binds to cytochrome oxidase allosteric site
  • prevents it from functioning in the ETC
  • aerobic resp doesnt happen
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5
Q

Feedback inhibition

A
  • method of negative feedback in metabolic pathways
  • products of metabolic pathways are NC inhibitors of an earlier enzyme (often first step)
  • increase in product levels -> enzyme inhibited -> product levels decrease
  • decrease in product levels -> pathway uninhibited -> product levels increase
  • used to tightly regulated levels of essential molecules
  • binding to enzyme is reversible
  • isoleucine inhibits threonine to isoleucine pathway by binding to threonine deaminase
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6
Q

Isoleucine pathway inhibition example

A
  • Isoleucine formed from threonine in 5 step pathway
  • threonine deaminase is the first enzyme to convert threonine into intermediate
  • isoleu binds to TD allosteric site and prevents this formation
  • ensures that isoleu production pathway doesn’t deplete threonine stocks
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7
Q

Drug design based on enzyme inhibition

A
  • microbe proteome sequenced from genome -> metabolism enzymes identified
  • microbe (eg plasmodium for malaria) enzymes are identified -> in plasmodium -> the enzymes needed for metabolism
  • inhibitors for that enzyme found via screening through bioinformatic database
  • inh made less toxic, with increased binding affinity
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8
Q

rational drug design

A
  • using computers/software to generate a compound -> will function as an inhibitor for an enzymes AS
  • using combinatorial chemistry to make that compound
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9
Q

ATP - why it is used for energy, functions

A
  • 3 phosphate bonds
  • phosphorylation makes compounds less stable, more reactive -> atp readily reacts with other compounds
  • on breaking terminal phosphate bond -> lots of enegry released
  • functions as the energyb currency -> transfers the phosphate group to other molecules -> releases energy for reactions
  • renders other org. molecules less stable
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10
Q

2 sources of energy to synth ATP from adp

A
  • solar energy (during photosynth)
  • oxidative processes (cell respiration)
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11
Q

Define cell respiration

A

The controlled release of energy from org. compounds to produce ATP (aerobic -> in pres of O2)

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12
Q

Benefits of series of reactions to form one reaction

A
  • smaller activation energies -> can occur at normal temperatures and rates,
  • less energy loss through heat -> transferred to carrier molecules
    • transferred via transfer of H atoms -> energy transferred to electron carriers with protons and electrons
    • carriers carry H to the ETC -> used to synth ATP
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13
Q

what are the similarities between photosynthesis and respiration

A
  • both use double-membrane bound organelles;
  • both use an electron transport chain to synthesise ATP;
  • both generate proton gradient/involve chemiosmosis/use ATP synthase
  • both generate ATP;
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13
Q

what are the differences between photosynthesis and respiration

A
  • R uses O2, P releases O2
  • R releases CO2, P FIXES CO2
  • R occurs in the mitochondria/matrix, P occurs in the chloroplast/stroma (for LIR);
  • R reduces FAD/NAD, P reduces NADP
  • R: chemical energy to usable energy/ATP, P: solar energy to chemical energy;
14
Q

Anaerobic v aerobic respiration definitions

A

AN: the incomplete controlled breakdown of organic molecules to produce a small yield of ATP. No oxygen is not required

A: the complete breakdown of organic molecules to produce a large yield of ATP in the presence of oxygen.

15
Q

How hydrogen/electron carriers work

A
  • H+ ions and e- are transferred from organic molecules to the carrier molecules -> energy stored in organic molecules also transferred
  • e- carriers carry the e- and 2H+ to the cristae of the mitochon. -> transfer to the ETC
  • in the ETC the energy of the e- and H+ are used by ATP synthase to synth ATP
  • only in aerobic resp is ATP thats derived using FADH2 and NADH used
16
Q

What happens to pyruvate if oxygen is not present?

A

In humans:
- forms lactic acid
- in the process to form lactic acid it is reduced -> reduced by the electron carriers -> oxidised to OG state to replenish stocks

In microogr/yeast
- forms CO2 and ethanol
- same as above

NAD+ stocks hence replenished so small quantities of ATP can continue to be produced

17
Q

Explain how chemical energy for use in the cell is generated via chemiosmosis and electron transport

A
  • electron carriers FAD and NAD+ are reduced in glycolysis/link/krebs BY GAINING 2 H AND 2 E
  • reduced FAD and NAD deposit high energy electrongs and H+ ions at the cristae of mitochon at IM proteins
  • electrons travel down ETC, from one carrier protein to the next in a series of redox reactions
  • as electron travle down they release energy
  • this generates energy for H+ ions to be pumped via proton pumps across the membrane into the IMS
  • The p+ concentration builds up in the IMS and a proton motive force forms
  • the protons travel down this chemiosmotic gradient across the mem through the transmem. protein ATP synthase in inner mitochondrial cristae/mem
  • energy released when electrons pass through ATP synthase
  • ATP synthase uses the movement of H+ to catalyse the reaction forming ATP from ADP +Pi
  • oxidative phosphorylation
  • Electrons in the ETC are accepted by O, the final e acceptor, and this ensures the ETC can continue
  • chemiosmosis is the use of the movement of H+ ions down a concentration gradient to generate ATP
18
Q

total atp from aerobic

A

38

19
Q

mitochondria adaptations

A
  • cristae - large mem area for etc
  • matrix has the right enzymes and pH for krebs cycle
  • mem proteins: electron carriers and other proteins for the ETC and ATP Synthase. outer membrane has the right transport proteins to transport pyruvate from cytosol
  • small IMS - maximise the p+ gradient
20
Q

Electron tomography

A

creating 3d visualisation of a sample

  • Imaging using a TEM
  • Image of sample repeatedly taken, tilting it at different angles between images
  • 3D model generated
  • samples must be dehydrated and fixed or frozen

Things discovered:
- IMS is of a consistent width
- the cristae are continuous with the inner mem
- the shape, position and volume of mito can keep changing in active mitochon.

21
Q

Non-cyclic photophosphorylation

A
  • Light energy/photons are absorbed
  • by PSII
  • Energy used in the photolysis of water -> 2H+, O, 2e-
  • PSII electrons are excited -> travel down an ETC in the thylakoid membrane -> one carrier to next througha. series of redox reactions
  • this movement releases energy
  • energy used to pump H+ ions across the thy. mem into the thylakoid space.
  • The H+ ion conc increases, generating proton motive force
  • H+ ions diffuse down the concentration gradient though ATP Synthase in the thylakoid mem. -> the energy from the diffusion of H+ ions used to synth ATP
  • from ADP + Pi
  • e- from ETC enter PSI where they are re-excited
  • transferred to a protein where they reduce NADP+ to NADPH + H+
  • e- lost initially from PSII are replaced by electrons from photolysis of water
  • end products: reduced NADP, ATP and O2 as a by-product
22
Q

Cyclic photophosphorylation

A
  • Only the electrons in PSI are excited
  • NADP+ is not reduced
  • the electrons from PSI undergo the ETC, synthesise ATP and return to the PSI to be re-energised
23
Q

C v. NC photophosphorylation

A

basic differences: oxygen evolved, PSI and PSII used, water photolysis and NADPH produced for NC

NC is to produce ATP as well as organic molecules for further long term storage. C only produces ATP in presence of sunlight

24
Q

How Calvin cycle was discovered

A
  • algae grown in radioactive C-14 -> C - 14 incorporated into compounds -> light shone of algae so it photosynthesises
  • algae run through hot ethanol to kill it
  • 2D chromatography used to identify the compound w radioactivity
  • radioactive compounds identified using autoradiogrpahy
  • experiment repeated by exposing the plant to ligth for different times -> order of compounds determined
25
Q

Chloroplast adaptations

A
  • Thin space within thylakoids: optimise h+ [] grad
  • photosystems in the thylakoid membranes for the ETC -> PS maximise light absorption
  • suitable enzymes and pH in the stroma for calvin cycle
  • grana: thylakoids arranged into stacks to maximise the SA of the thyl. mem.
  • ## lamellae: connects and separates different grana, maximising photosynthetic efficiency

HL Biology - topical sets (11 decks)

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