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week 2 Flashcards

1
Q

define cellular respiration

A

metabolic process with which an organism obtains energy by oxidising nutrients and releasing waste products of H20 and CO2

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2
Q

what are catabolic and anabolic reactions

A

catabolic: energy released through breakdown of larger molecules
anabolic: energy required to build up larger molecules eg proteins

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3
Q

what are the 3 overall stages of respiration

A

glycolysis, TCA/Krebs, ETC

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4
Q

explain what occurs in the glycolysis stage of respiration

A

breakdown of glucose to capture energy, done via phosphorylation to yield ATP, and REDOX reactions yield electrons carried by electron carrier NADH
all occurs in the cytosol and can proceed in the absence of oxygen

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5
Q

what is the resulting products of the glycolysis stage

A

1 glucose molecule yields 2 pyruvate, 2 H20 2 ATP and 2 NADH

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6
Q

what occurs during TCA/Krebs cycle

A

occurs within the mitochondria and yields energy in the form of ATP and electrons carried by NADH and FADH2 to be used in the ETC
Acetyl-CoA combines with oxaloacetate, and is regenerated at the end of the cycle so a new molecule of Acetly-CoA can be converted

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7
Q

what occurs during the ETC

A

occurs in mitochondria, electrons carried by NADH and FADH2 are released, and travel through a series in molecules in the inner mitochondrial membrane

during movement energy is used to pump H+ molecules across the inner membrane, forming an electrochemical gradient.

causes ions to flow back across the membrane through ATPsynthase, known as chemiosmosis

oxygen is reduced to water as it is the final electron acceptor, combining with H+

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8
Q

what is the result of the TCA cycle

A

2 ATP, 8 NADH, 2 FADH and 6CO
TCA cycle must be completed twice for one original glucose molecule

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9
Q

overall what is the input and output of glycolysis

A

2 ATP used, 4 ATP made, net 2 ATP made from each glucose molecule

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10
Q

when is resiration affected by lack of oxygen

A

glycolysis can still occur but it cannot proceed to stage 2
lactate is made in animals and ethanol in plants

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11
Q

what enzyme adds phosphate

A

kinase

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12
Q

what enzyme splits things

A

lyase

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13
Q

what enzyme cleaves water

A

enolase

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14
Q

what does isomerase do

A

converts molecule from one isomer to another, no splitting

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15
Q

what do dehydrogenase enzymes do

A

oxidises a substrate by reducing an electron acceptor

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16
Q

what is the basic equation for respiration

A

glucose + oxygen -> CO2, H2O and ATP

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17
Q

define photosynthesis

A

converting CO2 and H2O into carbohydrates using cellular energy

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18
Q

where does photosynthesis occur (larger organism)

A

in phototrophs which are organisms that capture photons, produce compounds and acquire energy

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19
Q

what is a dark reaction

A

a reaction that doesn’t require light and occurs in the stroma in solution
it reduces gaseous CO2 to carbohydrates
requires energy from NADPH and ATP

20
Q

what is a light reaction

A

a reaction that requires light and occurs in the thylakoids
electrons are excited when light hits chlorophyll, electrons move through the ETC, generating ATP and NADPH
H2O is split to release oxygen
the energy is used in the dark reactions, and O2 is released into the air

21
Q

how are chloroplasts structured

A

double membranes, stacks of thylakoids within the membrane with stroma inbetween (this is the solution where dark reactions take place)

22
Q

how do chlorophylls capture light most effectively

A

they contain a tetrapyrrole ring (chlorin), and contain Mg2+ at the centre with pyrroles surrounding
their shape also means they have a higher chance of capturing light

23
Q

what are the different types of chlorophyll in plants and bacteria

A

chlorophyll a and b in plants
bacteriochlorophylls a and b similar and major pigments in anaerobic photosynthetic bacteria

24
Q

what are antenna pigments and name some types of them

A

light absorbing molecules in thylakoid membranes of chloroplasts
include carotenoids, phycocyanin and phycoerythrin

25
what are the purpose of antenna pigments
to extend the range of light capture, especially in green
26
how is light energy captured using antenna pigments and chlorophylls
they exchange light energy (excited electrons) until captured
27
what are PS1 and PS2
photosystems that operate in series connected by cytochrome bf complex they contain many proteins and pigments embedded in the thylakoid membrane
28
how do PS 1 and 2 work
electrons are excited in both and go through cascade between them enters in PS1 in oxidised state, then becomes reduced
29
what is the structure of DNA
sugar phosphate backbone, strands running antiparallel 10 base pairs per turn of the double helix bases are on the inside, phosphate on the outside space filling model show major and minor groove in the double helix
30
why is it called the semi-conservative model of dna replication
explains how DNA copies itself before cell division, and each new DNA molecule consists of one original strand and one newly synthesised strand
31
why is the semi conservative model so important
it ensures accurate DNA copying with fewer mutations allows genetic information to be passed on during cell division keeps DNA structures stable across generations
32
what are the three steps of replication
Initiation (Unwinding the DNA) Elongation (Building the new strands) Termination (Finalising the process)
33
what occurs during initiation
happens in nucleus of eukaryotic cells and cytoplasm of prokaryotes helicase unzips DNA by breaking hydrogen bonds between bases Topoisomerase prevents DNA from supercoiling or tangling during unwinding Single Strand binding proteins (SSBs) keep the DNA strands separated and stable results in a replication form - one in prokaryotes and many in eukaryotes
34
what ocurs during elongation
DNA polymerase adds new nucleotides primase adds a short RNA primer which tells DNA polymerase where to start copying Leading strand shows continuous copying in the 5' to 3' direction Lagging strand shows fragmented copying, where DNA polyermase works in short segments (Okazaki fragments) each fragment needs a new primer before DNA polymerase can add nucleotides DNA ligase joins the fragments together into a continuous strand
35
what occurs during termination
RNA primers are removed, DNA polymerase fills the gaps with DNA DNA ligase connects any remaining fragments, leaving 2 identical DNA molecules, each with one original strand and one new strand
36
what wavelengths do PSI and PSII absorb
PSI paired for P700 - absorbs light up to 700nm PSII paired for P680 - absorbs light up until 680nm
37
how does the Z scheme work - details
it is the path of electron flow and reduction potentials of the components in photosynthesis the absorption of light energy converts P680 and P700 (poor reducing agents) to excited molecules (good reducing agents) light energy drives electron flow uphill light is captured by antenna complexes for 2 H2O oxidised to O2, 2 NADP+ are reduced to 2 NADPH
38
how was the Calvin cycle discovered
identified in 1948, led to the Nobel prize in chemistry key enzyme is RuBisCo discovered using radioactive carbon-14 (¹⁴C) labelling to track the sequence of carbon transitions. By introducing ¹⁴CO₂ into algae and stopping photosynthesis at different time intervals, Calvin identified the order in which intermediate compounds formed. the cycle regenerates RuBP allowing constant fixation of CO2
39
how were dark reactions identified
a fast CO2 injection and a rapid 'quench' of perchloric acid to stop reactions 2D chromatography improves separation of intermediates
40
what is photorespiration
it recycles the toxic products of the oxygenation reaction; it consumes NADH, ATP to give glyoxylate, serine, glycine and CO2 catalysed by RuBisCo like photosynthesis
41
what is RuBisCo's main substrate
CO2 in photosynthesis, to incorporate CO2 into an organic molecule
42
how have angiosperms evolved to 'feed' RuBisCo during photosynthesis
C4 and CAM photosynthesis
43
how have cyanobacteria and algae evolved to 'feed' RuBisCo during photosynthesis
cyanobacteria: form carboxysomes algae: form pyrenoids
44
how does C4 photosynthesis work
it fixes HCO3- with pyruvate into malate, then transports malate to a second cell for decarboxylation and refixation by RuBisCo more efficient because it fixes HCO3- first, and avoids O2 it depends on spatial separation of C4 and C3 fixation reactions the only major C4 crop is maize summary = C4 respiration gets around the CO2 limitation by introducing a pre-fixation step to capture C as a 4-carbon acid
45
what is CAM photosynthesis
CAM = crassulacean Acid Metabolism it depends on separation of timing of the C4 and C3 fixation reactions CAM plants store C4 acids (malate) in the vacuole for decarboxylation and refixation by RuBisCo in the day CAM requires fine control of gene expression over the day/night cycle CAM uses 'introverted' cycle of stomatal opening/closing to save water and concentrate CO2 in the leaf only major CAM crop is pineapple
46
what is C3 photosynthesis
most common - default pathway carbon gets fixed by RuBisCo sometimes photorespiration mistakenly happens when RuBisCo binds with CO2 instead of O2, reducing efficiency it depends on rubisco selectivity between CO2 and O2
47
what conditions suit C4 and CAM photosynthesis
well suited to growth under high light - extra energy - and reduced water availability

bio 1B (11 decks)

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