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Biology > Topic 5 Energy & eco systems > Flashcards

Topic 5 Energy & eco systems Flashcards

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1
Q

Describe how biomass is formed in plants

A

During photosynthesis, plants make organic carbon compounds from atmospheric or aquatic CO2. Most sugars made are used by the plant as respiratory substrates.
The rest of the sugars are used to make other groups of biolgoical molecules such as carbs, lipids and proteins which form biomass

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2
Q

How can biomass be measured?

A

Mass of carbon or dry mass of tissue per given area

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3
Q

Describe how dry mass of tissue can be measured and why the factors at each stage are as they are

A

Sample dried in oven at 100 degrees to avoid combustion
The sample is weighed and reheated at regular intervals until the mass remains constant so all the water has evaporated.

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4
Q

What is biomass

A

Biomass is the total mass of living material in a specific area at a given time

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5
Q

Explain why dry mass is more representative than fresh wet mass?

A

Water volume in wet samples will vary but not affect the dry mass

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6
Q

Describe how the chemical energy stored in dry biomass can be estimated?

A

Using calorimetry:
-Known mass is biomass is fully combusted (burnt)
-Heat energy released heats a known volume of water
-Increase in temperature of the water is used to calculate chemical energy of the biomass

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7
Q

Explain how features of a calorimeter enable valid measurement of heat energy released

A

Stirrer- Evenly distributes heat energy in water
Air/insulation- reduces heat loss and gain to and from surroundings
Water- has high specific heat capacity

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8
Q

What is gross primary production?

A

The total quantity of chemical energy stored in plant biomass in a given area or volume in a given time. It is also the total energy transferred into chemical energy from light energy during photosynthesis.

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9
Q

What is net primary production?

A

The amount of chemical energy stored in plant biomass after some energy is lost to respiration

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10
Q

State the formula for net primary production

A

Gross primary production - respiratory losses = net primary production

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11
Q

Explain the importance of net primary production in ecosystems

A

The net primary production is available for plant growth and reproduction, it is also available to other trophic levels in the ecosystem such as herbivores and decomposers

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12
Q

What are the units used for primary or secondary productivity?

A

kJ m-2 year-1 (unit for energy per unit area per year)

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13
Q

What is primary or secondary productivity?

A

The rate of primary or secondary production, respectively

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14
Q

Why are the given units for primary or secondary productivity used?

A

kJ- amount of energy produced
Per unit area- takes into account that different environments vary in size which standardizes results to enable comparison between environments.
Per year- Takes into account the effect of seasonal variation (e.g temperature) on biomass. This is more representative and enables comparison between environments.

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15
Q

Explain why most light falling on producers is not used in photosynthesis

A

-Light is reflected or wrong wavelength
-Light missed chlorophyll/chloroplasts/photosynthetic tissue
-CO2 concentration or temperature is a limiting factor

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16
Q

State the formula for net production of consumers

A

N=I-(F+R)
N- net production
I- ingested food
F- Energy lost in urine and faeces
R -represents the energy lost in respiration

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17
Q

State the formula for efficiency of energy transfer

A

Percentage efficiency transfer = biomass in higher trophic level / biomass in lower trophic level × 100

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18
Q

Explain why energy transfer between trophic levels is inefficient

A

-Heat energy is lost via respiration
-Energy lost via parts of organism that aren’t eaten e.g bones
-Energy lost via food not digested like faeces
-Energy lost via excretion e.g urea in urine

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19
Q

Explain how different crop farming practices increase efficiency of energy transfer

A

You can simplify the food webs to reduce energy/biomass loss to non human food chains such as Herbicides-Kill weeds so there is less competition(e.g light) so more energy to create biomass
Pesticides- Kill insects to reduce loss of biomass from crops from eating the crops (in direct competition with humans) or damaging crops and reducing ability to photosynthesize thus reducing productivity
Fungicides- Reduces fungal infections which means crops have more energy to create biomass.
Fertilisers- e.g. nitrates to prevent poor growth due to lack of nutrients due to lack of nutrients.

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20
Q

Explain how livestock farming practises increase efficiency of energy transfer

A

Reducing respiratory losses within a human food chain
-Restrict movement and keep warm so less energy is lost as heat from respiration and vasodilation(most reared species are warm blooded)
-Slaughter animals while growing/young when most of their energy is used for growth
-Treat with antibiotics to prevent loss of energy to fighting pathogens
Selective breeding to produce breeds with higher growth rates

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21
Q

Explain the role of saprobionts in recycling chemical elements

A

-Decompose organic compounds such as proteins and DNA in dead matter
-Secreting enzymes for extracellular digestion
-Absorb soluble needed nutrients and release mineral ions e.g. Phosphate ions

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22
Q

Explain the role of mycorrhizae

A

Symbiotic association between fungi and plant roots Fungi acts as an extension of plant roots to increase surface area of root system
This increases rate of uptake/absorption of water and inorganic ions#In return fungi receive organic compounds e.g carbohydrates

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23
Q

Give examples of biological molecules that contain nitrogen

A

Amino Acids
Proteins/Enzymes
Urea
DNA RNA
Chlorophyll
ATP/ADP
NAD/NADP

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24
Q

What are the 4 main stages of the nitrogen cycle

A

Ammonification
Nitrification
Nitrogen fixation
Denitrification

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25
Q

Describe the stage of ammonification in the nitrogen cycle

A

NItrogen containing compounds such as proteins and urea from dead organisms are broken down/decomposed. Saprobiontic micro organisms mainly fungi and bacteria that feed on this(release enzymes for extracellular digestion) release ammonia which then forms ammonium ions in the soil.

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26
Q

Describe the stage of nitrification in the nitrogen cycle

A

Ammonium ions in the soil are converted from ammonium ions to nitrite ions (NO2-)
then from nitrite ions to Nitrate ions (NO3-) via a 2 step oxidation reaction. This reaction is carried out by nitrifying bacteria in aerobic conditions (oxygen), this is an exothermic reaction

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27
Q

Describe what nitrogen fixation is and the process

A

Nitrogen gas is converted into nitrogen containing compounds, it can be carried out industrially or when lightning is struck. There is free living nitrogen fixing bacteria that reduce gaseous nitrogen to ammonia which these use to manufacture amino acids
In addition, there is mutualistic nitrogen fixing bacteria that live on root nodules in plants like peas/ beans they obtain carbohydrates from the plant and the plant amino acids from the bacteria

28
Q

Describe the process of denitrification

A

When nitrates in soil are converted into nitrogen gas through reduction reaction by denitrifying bacteria in anaerobic conditions (e.g.waterlogged soil)

29
Q

Suggest why ploughing (aerating soil) increases its fertility

A

More ammonium converted into nitrite and nitrate (more nitrification)
Less nitrate converted to nitrogen gas (less denitrification)

30
Q

Give examples of biological molecules that contain phosphorus

A

Phospholipids/DNA RNA/ ATP or ADP

31
Q

Describe the phosphorus cycle

A

Phosphate ions in rocks are released into soils and oceans by erosion
Phosphate ions are taken up by producers and incorporated into their biomass(rate of absorption increased by mycorrhizae)
Phosphate ions are transferred through food chain e.g producers are eaten by herbivores
Some phosphate ions lost from animals in waste products
Saprobionts decompose organic compounds like DNA in dead matter releasing phosphate ions

32
Q

Explain why fertilisers are used

A

To replace nitrates and phosphates lost when plants are harvested and livestock are removed.
Those removed from soil and incorporated into biomass cant be released back into soil through decomposition by saprobionts. So efficiency of energy transfer is improved increasing yield

33
Q

Describe the difference between artificial and natural fertilisers

A

Natural fertilisers- Organic matter that consists of dead and decaying remains e.g. manure. Ions from these fertilisers are released during decomposition by saprobionts
Artificial fertilisers- Inorganic fertilisers that are mined from rocks and deposits, converted into different forms and blended for appropriate balance of minerals. NPK always present.

34
Q

Explain the key environmental issue arising from use of fertilisers

A

Phosphates and nitrates dissolve in water leading to leaching of nutrients into lakes. This leads to eutrophication which is where there is an algal bloom so light is blocked. Submerged plants die as they cannot photosynthesise. Saprobionts decrease dead plant matter using oxygen in aerobic respiration. There is less oxygen for fish to aerobically respire leading to their death

35
Q

Explain the key advantage of using natural fertiliser over artificial fertiliser

A

-Less water soluble so less leaching and eutrophication is less likely
-Organic molecules require breaking down by saprobionts which means there is slow release of nitrate/phosphate

36
Q

What are the stages of photosynthesis and where do they occur

A

-Light dependent reaction in the thylakoid membrane of chloroplast
-Light independent reaction of stroma of chloroplast

37
Q

Describe photoionisation in the light dependent reaction

A

-Chlorophyll absorbs light energy which excites electrons to a high energy level
-Electrons are released from chlorophyll so chlorophyll becomes positively charged

38
Q

Describe what happens after photoionisation in the light dependent reaction

A

Some energy released from electrons in photoionisation is conserved in the production of ATP/Reduced NAPD which is called the chemiosmotic theory which is where:
-Electrons move along electron transfer chain releasing energy
-This energy is used to actively pump protons from the stroma into thylakoid
-Protons move by facilitated diffusion down electrochemical gradient into stroma via ATP synthase
-Energy used to join ADP and Pi to form ATP (photophosphorylation)
-NADP accepts a proton and an electron to become reduced NADP

39
Q

Describe the photolysis of water in the LDR

A

Light strikes chlorophyll molecule leaving it short of electrons and unable to absorb light
Water splits to reduce protons, electrons and oxygen, Electrons replace those lost from chlorophyll

40
Q

Describe the light dependent reaction of photosynthesis (calvin cycle)

A

-CO2 diffuses into leaf through stomata and dissolves in water around the walls of mesophyll cells. Then diffuses into stroma of the chloroplast where it reacts with ribulose bisphosphate (RuBP) catalysed by the enzyme rubisco
-This forms 2 glycerate 3-phosphate (GP) molecules
-Reduced NADP from light dependent reaction is used to reduce GP is reduced to Triose phosphate (TP) using energy supplied by ATP.
-Reduced NADP is re-formed and goes back to the light dependent reaction to be reduced again by accepting more protons
-Some TP converted to useful organic substances (e.g. glucose)
-Some TP used to regenerate RuBP in the calvin cycle using energy from ATP

41
Q

Describe and explain how temperature affects the rate of photosynthesis

A

1) As temperature increases, rate increases
-Enzymes such as rubisco gain kinetic energy so more enzyme substrate complexes are formed
2) Above optimum temperature, rate decreases
-Enzymes denature as H bonds in tertiary structure break
-Fewer enzyme substrate complexes form

42
Q

Describe and explain how light intensity affects rate of photosynthesis

A

1) As light intensity increases, the rate increases
-Light dependent reaction increases do there is more photoionisation of chlorophyll so more ATP and reduced NADP produced.
-Light independent reaction increases as more GP reduced to TP and more TP regenerates RuBP
2) Above a certain light intensity, the rate stops decreasing, this is because another factor is limiting such as Temp or CO2 conc

43
Q

Describe and explain how CO2 concentration affects the rate of photosynthesis

A

1) As CO2 conc increases, rate increases
-Light independent reaction increases
-More CO2 combines with RuBP to for GP
-So more GP reduced to TP
-So more TP converted to organic substances and more RuBP regenerated
2) Above a certain CO2 concentration, rate stops increasing because of other limiting factors such as temp/ light intensity

44
Q

Explain the key consideration when evaluating data relating to agricultural practices used to overcome the effect of limiting factors

A

Agricultural practice should increase the rate of photosynthesis leading to increased yield because, more glucose produced for faster respiration so more ATP release energy for growth e.g cell division and protein synthesis. But extra profit from extra yield should be greater than costs.

45
Q

Describe how pigments from a leaf of a plant can be isolated with paper chromatography

A

-Crush leaves with solvent to extract pigments
-Draw a pencil line on chromatography paper 1cm above bottom
-Add a drop of extract to line (point of origin)
-Stand paper in boiling tube of organic solvent below the point of origin
-Add lid and leave to solvent to move up carrying dissolved pigments
-Remove before solvent reaches top and mark solvent front with a pencil

46
Q

Explain why the origin should be drawn in pencil rather than with ink

A

Ink is soluble in solvent so it would mix with the pigments causing the line to move

47
Q

Explain why the point of origin should be above the level of the solvent

A

Pigments are soluble in solvent, so would run off paper

48
Q

Explain why a pigment may not move up the chromatography paper in one solvent

A

May be soluble in one solvent but insoluble in another

49
Q

Describe how pigments can be identified from chromatogram

A

Calculate Rf value which is = distance moved by spot/distance moved by solvent front
-Compare Rf value to published value

50
Q

Explain why the solvent front should be marked quickly once chromatography paper is removed

A

Once solvent evaporates, solvent front is not visible

51
Q

Explain why the centre of each pigment spot should be measured

A

Standardises readings as pigment is spread out. this allows comparisons to be made

52
Q

Explain why the obtained Rf values were similar but not identical to the published values

A

DIfferent solvent/paper/running conditions may affect Rf value

53
Q

Explain why Rf values are used and not the distances moved by the pigment spots

A

Solvent/pigment moves different distances.
Rf value is constant for the same pigment so value can be compared

54
Q

Describe the role of the enzyme dehydrogenase in photosynthesis

A

-Catalyses the reduction of NADP in the light dependent reaction
-NADP accepts electrons from photoionisation of chlorophyll/ photolysis of water

55
Q

Describe how the rate of dehydrogenase activity in extracts of chloroplasts can be measured

A

-Extract chloroplasts from a leaf sample using centrifuge
-Control 1 - set volume of DCPIP (redox indicator dye, electron acceptor), water and chloroplasts in isolation medium, covered in foil to block light
B. Control 2 - set volume of DCPIP, water and isolation medium without chloroplasts
C. Standard - set volume of water and chloroplasts in isolation medium, without DCPIP
D. Experiment - set volume of DCPIP, water and chloroplasts in isolation medium
Shine light on test tubes and time how long to it takes for DCPIP to turn from blue (oxidised) to
colourless (reduced) in tube D (tube A and B should show no change)
- Compared to a colour standard (tube C) to identify end point
4. Rate of dehydrogenase activity (1/time taken)

56
Q

What is a limit to the method to measure dehydrogenase activity and how can this be overcame?

A

-End point (colour change) is subjective
-Use a colorimeter
-Measure light absorbance of the sample at the set time intervals
-Zero colorimeter using the colour standard

57
Q

why respiration is important ?

A

-Respiration produces ATP which is used for active transport and protein synthesis

58
Q

Summarise the stages of aerobic and anaerobic respiration

A

Aerobic-
1. Glycolysis - cytoplasm (anaerobic)
2. Link reaction - mitochondrial matrix
3. Krebs cycle - mitochondrial matrix
4. Oxidative phosphorylation - inner
mitochondrial membrane

Anaerobic respiration
1) Glycolysis- cytoplasm
2) NAD regeneration- cytoplasm

59
Q

Describe the process of glycolysis

A

-Glucose phosphorylated to glucose phosphate using inorganic phosphates from 2 ATP
-Hydrolysed to 2x triose phosphate
-Oxidised to pyruvate
2 NAD reduced
4 ATP regenerated (net gain of 2)

60
Q

Explain what happens after glycolysis if respiration is anaerobic

A

-Pyruvate is converted to lactate (in animals and some bacteria) or ethanol (in plants and yeast)
-Oxidising reduced NAD- NAD regenerated
-SO glycolysis can continue (which needs NAD)
allowing continued production of ATP

61
Q

Suggest why anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration

A

-Only glycolysis involved which produces little ATP (only 2 molecules)
-No oxidative phosphorylation which forms majority of ATP (34 molecules roughly)

62
Q

What happens after glycolysis if respiration is aerobic?

A

Pyruvate is actively transported into the mitochondrial matrix.

63
Q

Describe the link reaction

A

-Pyruvate is oxidised to acetate. CO2 is produced and reduced NAD produced
-Acetate combines with coenzyme A, forming Acetyl coenzyme A

64
Q

Describe the Krebs cycle

A

1) Acetyl coenzyme A reacts with a 4C molecule
-releasing coenzyme A
-producing a 6C molecule that enters the Krebs cycle

2)In a series of oxidation-reduction reactions, the 4C molecule is regenerated and
-2x CO2 lost
-Co enzymes NAD & FAD reduced
-Substrate level phosphorylation (direct transfer of pi from intermediate compound to ADP)
-ATP produced

65
Q

Describe the process of oxidative phosphorylation

A

1) Reduced NAD oxidised to release H atoms which are split into H+ protons and electrons (e-)
2) Electrons transferred down the electron transfer chain by redox reactions
3) Energy released by electrons used in the production of ATP from ADP+Pi (chemiosmotic theory)
-Energy used by electron carriers to actively pump protons from matrix
-Protons diffuse into matrix down an electrochemical gradient via ATP synthase
-Releasing energy to synthesise ATP from ADP and PI
4) In a matrix at end of electron acceptor, oxygen is the final electron acceptor, so protons, electrons and oxygen combine to form water.

66
Q
A

Biology (11 decks)

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