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A-Level Bio > Unit 5: Energy Transfers In & Between Organisms > Flashcards

Unit 5: Energy Transfers In & Between Organisms Flashcards

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Biology 101 flashcards
1
Q

what is the site of the light dependent stage of photosynthesis

A

the grana

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2
Q

describe the stroma

A

a fluid-filled matrix where the light independent stage of photosynthesis takes place. it contains a number of other structures like starch grains.

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3
Q

what does the chloroplast genome code for

A

ribosomal RNA

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4
Q

define community

A

all the living organisms that live in a habitat at the same time

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5
Q

define population

A

the number of the same species that live in a habitat at the same time

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6
Q

define ecosystem

A

a community in conjunction with the non living components of the environment

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7
Q

define abiotic

A

the non living, chemical and physical components of the ecosystem

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8
Q

define biomass

A

the total mass of living matter within an organism

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9
Q

define respiratory substrate

A

the organic molecules that can be oxidised by respiration, releasing energy to make molecules of ATP

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10
Q

define calorimetry

A

a technique used to measure the quantity of heat gained/lost by a system

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11
Q

the measure of biomass

A

dry mass of tissue per given area

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12
Q

use of calorimetry

A

to estimate the chemical energy store in dry biomass

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13
Q

what do the sugars synthesised by plants form

A

most are used as respiratory substrates and the rest make other groups of biological molecules which form the biomass

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14
Q

define gross primary production

A

the total quantity of the chemical energy store in plant biomass, in a given area or volume, in a given time

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15
Q

define net primary production

A

the chemical energy store which is left in plant biomass after respiratory losses to the environment have been taken into the account

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16
Q

what is NPP available for

A

plant growth, reproduction, to other trophic levels in the ecosystem such as herbivores/consumers and decomposers

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17
Q

the equation for net production of consumers

A

net = I - (F+R)
I = chemical energy store in ingested food
F = chemical energy store lost to the environment in faeces and urine
R = respiratory losses to the environment

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18
Q

explain the reasons why a low percentage of energy is transferred between trophic levels

A

some of the organism is not consumed
some parts cannot be digested
some energy lost in excretory materials
some energy lost as heat from respiration, lost to the environment

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19
Q

equation for percentage efficiency

A

energy available after transfer divided by energy available before transfer x 100

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20
Q

one aim of a farming practice and an example

A

to reduce respiratory losses in a human food chain in order to reduce energy loss and increase yield.
e.g keeping animals in confined spaces to reduce muscle movement and can keep them warm to reduce heat loss (ethical concerns)

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21
Q

second aim for farming practice and an example

A

to simplify food webs in order to reduce energy losses to non-human food chains.
e.g reduce/eliminate organisms that compete with the organism being farmed (crops compete with plants for water, space and light etc)

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22
Q

benefit of natural predators introduced into the ecosystem

A

crops lose less biomass and increase productivities

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23
Q
A
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24
Q

explain ammonification

A
  • saprobiontic microorganisms feed off faeces, urine, and dead organisms
  • this releases ammonia which forms ammonium ions in the soil
  • the nitrogen returns to the non living component of the ecosystem
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25
Q

explain nitrification

A

oxidation reactions occurs which releases energy
oxidation occurs by free-living soil microorganisms known as nitrifying bacteria
first the oxidation of ammonium ions to nitrite ions
then the oxidation of nitrite ions to nitrate ions
the nitrifying bacteria need oxygen for these conversions

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26
Q

explain the farming practice of ploughing

A

nitrifying bacteria need oxygen for conversions of nitrate ions so lots of air spaces are preferable in the soil

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27
Q

explain nitrogen fixation

A

free-living nitrogen fixing bacteria reduce gaseous nitrogen to ammonia which they then manufacture into amino acids
when the bacteria decay/die, nitrogen rich compounds are released
mutualistic nitrogen fixing bacteria live on nodules on the roots of plants and obtain carbs from the plants
in exchange the plant gets amino acids from them.

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28
Q

explain denitrification

A

waterlogged soils means a decrease in oxygen concentration so there is a drop in aerobic nitrifying bacteria
therefore there is an increase anaerobic denitrifying bacteria which convert soil nitrates

29
Q

how do farmers prevent build up of denitrifying bacteria

A

ensure well aerated land

30
Q

define ammonification

A

the production of ammonia from organic nitrogen-containing compounds

31
Q

define nitrification

A

the conversion of ammonium ions to nitrate ions

32
Q

define nitrogen fixation

A

nitrogen gas is converted to nitrogen containing compounds

33
Q

outline the phosphorous cycle

A

phosphorous exists mostly as phosphate ions in sedimentary rock but weathering/erosion dissolves the ions
the ions are then absorbed by plants and are incorporated into their biomass
animals obtain the ions when they feed on these plants
excess ions are excreted and may accumulated in waste material
decomposers break down these dead plants and animals which releases phosphate ions into the water and soil
some of the ions are left in remains such as bone or shell because it is slower to decompose
the phosphate ions are then released by decomposition or dissolve out of rocks and are transported by rivers/streams into lakes/oceans where they form sedimentary rock and complete the cycle

34
Q

explain the role of mycorrhizae in nutrient cycles

A

fungi increase surface area for absorption of water/minerals
also acts as a sponge in the soil so holds water/minerals in the neighbourhood of the roots
this increases drought resistance and takes up inorganic ions more readily, improving the uptake of scarce phosphate ions

35
Q

describe the relationship between mycorrhizae and plants

A

a mutualistic/symbiotic relationship
the fungi gets sugars and amino acids from the plant
the plant benefits from increased water/ion uptake

36
Q

why does agriculture cause a loss in nutrients

A

when crops are harvested, minerals are removed and are not returned upon decomposition because the crops are taken away for consumption so minerals are not replaced by their remains/waste products

37
Q

define fertilisers

A

they replace the lost materials so increase energy efficiency of the food chain

38
Q

define natural fertilisers

A

organic matter such as manure, compost, sewage sludge, seaweed etc

39
Q

define artificial fertilisers

A

inorganic matter such as pure chemicals (ammonium nitrate as powder/pellets)

40
Q

describe the environmental issues with fertilisers

A

if more is added than can be used, the fertilisers are susceptible to leaching into waterways by rain or irrigation which can lead to eutrophication

41
Q

when is leaching more likely and with which fertiliser

A

if the fertiliser is applied just before rainfall.
artificial fertiliser is more soluble so more likely to leach

42
Q

benefit of natural fertiliser being less soluble

A

the fertiliser is released slower and with more control so it is harder to add in excess, less leaching

43
Q

relevance of phosphate-nitrate solubility

A

phosphates less likely to leach than nitrates as they are less soluble in water

44
Q

explain eutrophication

A

Caused by excess nutrients leaching into waterways/oceans etc)
The leached excess minerals stimulate rapid growth of algae, naturally nitrate ions are a limiting factor for plant and algal growth as in low concentrations
The new large amount of algae block light reaching plants beneath them, light becomes the limiting factor for growth at lower depths
These plants cannot photosynthesise enough so die
Saprobiontic bacteria then feed on the dead plants, as lack of dead organisms is no longer a limiting factor, they use up all remaining oxygen through aerobic respiration
Fish and other organisms in the water die because there is not enough dissolved oxygen to survive, oxygen becomes the limiting factor for the aerobic organisms
Less competition for the anaerobic organisms now so their populations rise
They further decompose dead material releasing more nitrates and making the water putrid.

45
Q

photolysis

A

a chlorophyll molecule absorbs a photon of light, splitting water into protons, electrons and oxygen
the electrons replace those lost due to photoionization
they provide energy for the proton pump and lead to chemiosmosis

46
Q

photoionization of chlorophyll

A

When a photon of light is absorbed, a pair of electrons gain energy and are excited
They become unstable and are transferred to an electron chain acceptor
Results in production of atp and reduced nadp

47
Q

chemiosmosis

A

Each electron carrier is at a lower energy level so electrons lose energy through the chain
This energy is used to transport protons from the stroma across into the thylakoid
Makes a concentration gradient of protons so they diffuse down the gradient through ATP synthase
This causes a change to the structure of ATP synthase and causes it to rotate, converts ADP and a Pi into ATP

48
Q

production of ATP and reduced NADP

A

ATP and NADPH are results of photolysis producing electrons and photoionisation moving those electrons outside the chlorophyll, through the electron transfer chain
Then chemiosmosis occurs to get the protons on the stroma side, producing ATP and NADP

49
Q

adaptations of the chloroplasts

A

Thylakoid membranes give a large surface area for the attachment of chlorophyll, electron carriers and enzymes for the LDR
Protein network in grana holds chlorophyll precisely to allow maximum light absorption
Granal membranes have ATP synthase to catalyze the production of ATP, selectively permeable to ensure a proton gradient
Contain dna and ribosomes to manufacturer some of the proteins involved in the LDR

50
Q

cyclic electron pathway

A

A photon is absorbed by chlorophyll a in PSI
Two electrons in this molecule is excited and attains a higher energy level and becomes unstable so is transferred to an electron acceptor
Acceptor is reduced, molecule is oxidized (photoionisation)
These redox reactions occur along the electron transport chain until the electron is accepted by ferredoxin
Each new carrier is at a lower energy level so electrons lose energy at each stage
Ferredoxin transfers the electron to the cytochrome proton pump which transfers it back to PSI
Protons are pumped across the thylakoid membrane from the chloroplast stroma to the thylakoid lumen which creates a proton gradient
The protons flow through ATP synthase channel protein which changes the structure of the enzyme and causes it to rotate
This catalyses the addition of a phosphate and a proton to form ATP
Known as photo phosphorylation

51
Q

non cyclic photophosphorylation pathway

A

A photon is absorbed by a molecule of water which breaks down into electrons, protons and oxygen
The electrons move into the reaction centre of PS2
The chlorophyll a molecule in PS2 absorbs a photon and an electron in this molecule is excited
The electron is donated between the electron acceptors, creating a series of redox known as the electron transfer chain
A section of the chain involves the transfer of the electrons between PS2 and PS1 which is performed by cytochrome proton pump
Protons are pumped across the thylakoid membrane from stroma to lumen, creating a gradient
High concentration inside the thylakoid space and low in the stroma
Protons flow through the channel protein associated with ATP synthase, causing the enzyme to rotate
Atp synthase catalyses the addition of ADP and a phosphate, forming ATP
Electron moves into reaction centre in PS1
The electron is excited again when P700 absorbs a photon and it is transferred between electron acceptors to ferredoxin
Electron transferred from ferredoxin to NADP, this cofactor also joins with a hydrogen ion to form reduced NADP
The electron in PS2 is replenished when another molecule of water is photolysed

52
Q

How is carbon dioxide absorbed into the plant?

A

Carbon dioxide from the atmosphere diffuses into the leaf through stomata, it dissolves in water around the mesophyll cell walls.
Then diffuses through the cell surface membrane, cytoplasm and chloroplast membranes into the stroma of the chloroplast.

53
Q

How is carbon dioxide then incorporated into organic molecules?

A

It reacts with ribulose bisphosphate (RuBP 5C), the carboxylation catalysed by Rubisco.
This reaction produces two molecules of glycerate 3-phosphate (GP 3C.)
Reduced NADP from the LDR reduces GP to Triose phosphate (TP 3C) using energy supplied by ATP.

54
Q

What then happens to the NADP and TP?

A

The NADP is reformed and goes back to a reactant in the LDR to be reduced again
Some TP is converted to organic substances needed by the plant e.g starch, cellulose and amino acids
Most TP is used to regenerate RuBP using ATP from the LDR.

55
Q

Adaptations of the chloroplasts for the LIDR:

A

Stroma fluid contains all the necessary enzymes
Products of the LDR can readily diffuse into the stroma as the stroma fluid surrounds the grana
Contains dna and ribosomes so can manufacture proteins involved in the LIDR

56
Q

Generates ATP

A

both

57
Q

photolysis

A

non cyclic

58
Q

ps2

A

non cyclic

59
Q

ps1

A

both

60
Q

produces oxygen

A

non cyclic

61
Q

reduced NADP

A

non cyclic

62
Q

proteins in thylakoid

A

both

63
Q

Describe the role of RuBP in the Calvin cycle

A

combines with carbon dioxide to form two GP molecules

64
Q

State how the reduced NADP from the LDR is used in the LIDR

A

Reduces the GP to TP

65
Q

Which other product of the LDR is used in the LIDR

A

ATP provides the energy for the reduction reactions

66
Q

State precisely where in a plant cell the enzymes involved in the calvin cycle are found

A

in the stroma

67
Q

Light is not required for the calvin cycle to take place. Explain therefore why the calvin cycle cannot take place for long in the absence of light.

A

Reduced NADP and ATP, products from the LDR, are important components in the calvin cycle. With no more being produced, reduction of GP to TP cannot occur and the cycle will come to a halt.

68
Q

Why can plants not use the LDR as their only source of ATP? Suggest two reasons:

A

When it is dark, the plant will not be able to produce any ATP and will not make any glucose. Also, the LDR might not be efficient enough to produce ATP at the requirements of the plant. Cells without chlorophyll cannot produce ATP in this way and ATP cannot be transported around the plant

A-Level Bio (17 decks)

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