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A-level Biology > energy transfer in and between organisms > Flashcards

energy transfer in and between organisms Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Location of light dependent reaction

A

Thylakoid membranes of chloroplast

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2
Q

Location of light independent reaction

A

Stroma of chloroplast

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2
Q

Thylakoid membranes

A

Folded membranes containing photosynthetic proteins (chlorophyll)
embedded with transmembrane electron carrier proteins involved in the LDRs

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2
Q

Chlorophyll

A

Located in proteins on thylakoid membranes
mix of coloured proteins that absorb light
different proportions of each pigment lead to different colours on leaves

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3
Q

Light-dependent reaction (LDR)

A

First stage of photosynthesis occurs in thylakoid membranes uses light energy and water to create ATP and reduced NADP for LIR
involves photoionisation of chlorophyll, photolysis and chemiosmosis

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3
Q

Advantage of many pigments

A

Each pigment absorbs a different wavelength of visible light
many pigments maximises spectrum of visible light absorbed
maximum light energy taken in so more photoionisation and higher rate of photosynthesis

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4
Q

Photolysis

A

Light energy absorbed by chlorophyll splits water into oxygen, H+ and e-
H20 –> 1/2 O2 + 2e- + 2H+

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5
Q

Products of photolysis

A

H+
Picked up by NADP to form
reduced NADP for LIR

e-
passed along chain of
electron carrier proteins

oxygen
used in respiration or diffuses out leaf via stomata

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6
Q

Chemiosmosis

A

Electrons that gained energy move along a series of electron carriers in thylakoid membrane release energy as they go along which pumps proteins across thylakoid membrane electrochemical gradient made protons pass back across via ATP synthase enzyme producing ATP down their conc. gradient

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7
Q

Photoionisation of chlorophyll

A

Light energy absorbed by chlorophyll excites electrons so they move to a higher energy level and leave chlorophyll some of the energy released is used to make ATP and reduced NADP

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8
Q

What happens to protons after chemiosmosis

A

Combine with co-enzyme NADP to become reduced NADP reduced NADP used in LIR

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9
Q

Products of LDR

A

ATP (used in LIR)
reduced NADP (used in LIR) oxygen (used in respiration / diffuses out stomata)

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10
Q

Light independent reaction (LIR)

A

Calvin cycle
uses CO2, reduced NADP and ATP to form hexose sugar occurs in stroma which contains the enzyme Rubisco temperature-sensitive

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11
Q

RuBP

A

Ribulose Bisphosphate
5-carbon molecule

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12
Q

GP

A

Glycerate-3-phosphate
3-carbon molecule

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13
Q

TP

A

Triose phosphate
3-carbon molecule

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14
Q

Producing hexose sugar in LIR

A

Takes 6 cycles
glucose can join to form disaccharides (sucrose) or polysaccharides (cellulose) can be converted to glycerol to combine with fatty acids to make lipids

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15
Q

Limiting factor

A

A factor which, if increased, the rate of the overall reaction also increases

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16
Q

Limiting factors of photosynthesis

A

Light intensity
CO2 concentration
temperature

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17
Q

How light intensity limits photosynthesis

A

If reduced, levels of ATP and reduced NADP would fall
LDR limited - less photolysis and
photoionisation
GP cannot be reduced to triose phosphate in LIR

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18
Q

How temperature limits photosynthesis

A

LIR inhibited - enzyme controlled (Rubisco)
up to optimum, more collisions and E-S complexes
above optimum, H-bonds in tertiary structure break, active site changes shape - denatured

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19
Q

How CO2 concentration limits photosynthesis

A

If reduced, LIR inhibited
less CO2 to combine with RuBP to form GP
less GP reduced to TP
less TP converted to hexose and RuBP regenerated

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20
Q

Products of LIR

A

Hexose sugar
NADP - used in LDR

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20
Q

Agricultural practices to maximise plant growth

A

Growing plants under artificial lighting to maximise light intensity
heating in greenhouse to increase temperature
burning fuel to release CO2

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21
Q

Benefit of agricultural practices for plant growth

A

Faster production of glucose -> faster respiration
more ATP to provide energy for growth e.g. cell division + protein synthesis
higher yields so more profit

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22
Q

Stages of aerobic respiration

A

1) Glycolysis
2) Link reaction
3) Krebs cycle
4) Oxidative phosphorylation

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23
Q

Location of glycolysis

A

Cytoplasm

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24
Q

Glycolysis

A

Substrate level phosphorylation
- 2 ATP molecules add 2 phosphate groups to glucose glucose phosphate splits into two triose phosphate (3C) molecules
both TP molecules are oxidised (reducing NAD) to form 2 pyruvate molecules (3C) releases 4 ATP molecules

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24
Q

Coenzymes

A

A molecule which aids / assists an enzyme
NAD and FAD in respiration both gain hydrogen to form reduced NAD (NADH) and reduced FAD (FADH)
NADP in photosynthesis gains hydrogen to form reduced NADP (NADPH)

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25
Q

Products of glycolysis

A

Net gain of 2 ATP
2 reduced NAD
2 pyruvate molecules

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26
Q

How many ATP molecules does glycolysis produce

A

2 ATP molecules used to phosphorylate glycose to glucose phosphate
4 molecules generated in oxidation of TP to pyruvate net gain 2 ATP molecules

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27
Q

Location of the link reaction

A

Mitochondrial matrix

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28
Q

Link reaction

A

Reduced NAD and pyruvate are actively transported to matrix
pyruvate is oxidised to acetate (forming reduced NAD)
carbon removed and CO2 forms
acetate combines with coenzyme A to form acetylcoenzyme A (2C)

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29
Q

Products of the link reaction per glucose molecule

A

2 acetylcoenzyme A molecules 2 carbon dioxide molecules released
2 reduced NAD molecules

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30
Q

Mitochondria structure

A

Double membrane with inner membrane folded into cristae enzymes in matrix

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30
Q

Location of the Krebs cycle

A

Mitochondrial matrix

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31
Q

Krebs cycle

A

Acetylcoenzyme A combines with 4C molecule to produce a 6C molecule - enters cycle oxidation-reduction reactions

31
Q

Location of oxidative
phosphorylation

A

Cristae of mitochondria

32
Q

Products of the Krebs cycle per glucose

A

8 reduced coenzymes
6 reduced NAD
2 reduced FAD
2 ATP
4 carbon dioxide

33
Q

Role of reduced coenzymes in oxidative phosphorylation

A

Accumulate in mitochondrial matrix, where they release their protons (H+) and electrons (e-)
regenerate NAD and FAD to be used in glycolysis/ link reaction / Krebs cycle

34
Q

Role of electrons in oxidative phosphorylation

A

Electrons pass down series of electron carrier proteins, losing energy as they move
energy released actively transports H+ from mitochondrial matrix to inter- membranal space electrochemical gradient generated

35
Q

How is ATP made in oxidative
phosphorylation

A

Protons move down electrochemical gradient back into matrix via ATP synthase ATP created
movement of H+ is chemiosmosis

36
Q

Role of oxygen in oxidative phosphorylation

A

Oxygen is the final electron acceptor in electron transport chain
oxygen combines with protons and electrons to form water enables the electron transport chain to continue

37
Q

How would lack of oxygen affect respiration

A

Electrons can’t be passed along the electron transport chain
the Krebs cycle and link reaction stop because NAD and FAD (converted from reduced NAD/FAD as they release their H atoms for the ETC), cannot be produced

37
Q

Oxidation

A

Loss of electrons
when a molecule loses hydrogen

38
Q

Location of anaerobic respiration

A

Cytoplasm
glycolysis only source of ATP

39
Q

Reduction

A

Gain of electrons
a reaction where a molecule gains hydrogen

40
Q

Anaerobic respiration animals

A

Pyruvate produced in glycolysis is reduced to form lactate pyruvate gains hydrogen from reduced NAD
reduced NAD oxidised to NAD so can be reused in glycolysis
2 ATP produced

41
Q

Anaerobic respiration in plants & microbes

A

Pyruvate produced in glycolysis is reduced to form ethanol and CO2
pyruvate gains hydrogen from reduced NAD
reduced NAD oxidised to NAD so can be reused in glycolysis
2 ATP produced

42
Q

Other respiratory substances

A

Fatty acids and amino acids can enter the Krebs cycle for continued ATP synthesis

43
Q

Lipids as respiratory substances

A

Glycerol from lipid hydrolysis converted to acetylcoenzyme A can enter the Krebs cycle

44
Q

Producers

A

Plants
produce their own carbohydrates from carbon dioxide (autotrophs)
start of a food web

44
Q

Consumers

A

Heterotrophs that cannot synthesise their own energy obtain chemical energy through eating

45
Q

Energy transfer between trophic levels

A

Biomass and its stored energy is transferred through trophic levels very inefficiently
most energy is lost due to respiration and excretion

46
Q

Proteins as respiratory substances

A

Amino acids from protein hydrolysis can be converted to intermediates within Krebs cycle

47
Q

Biomass

A

Measured in terms of:
mass of carbon
dry mass of tissue per given area

48
Q

Calorimetry

A

Laboratory method used to estimate chemical energy stored in dry biomass

48
Q

How is dry mass of tissue estimated

A

Sample of organism dried in oven below 100C (avoiding combustion + loss of biomass) sample reweighed at regular intervals
all water removed when mass constant

49
Q

Why is dry mass a representative measure of biomass

A

Water content in tissues varies heating until constant mass allows standardisation of measurements
for comparison

50
Q

Calorimetry method

A

Sample of dry biomass is burnt energy released used to heat known volume of water
change in temperature of water used to calculate chemical energy

51
Q

Net primary production

A

Chemical energy stored in plant biomass after respiratory losses available for plant growth and reproduction - create biomass available to other trophic levels

51
Q

Gross primary production

A

Chemical energy stored in plant biomass, in a given area / volume
total energy resulting from photosynthesis

52
Q

Calculating net primary production

A

NPP = GPP - R
R = respiratory losses to the environment

53
Q

Calculating net production of consumers (N)

A

N = I - (F + R)
I = chemical energy store in ingested food
F = chemical energy store in faeces / urine
R = respiratory losses

54
Q

Units of productivity rates

A

kJ Ha-1 year-1
kJ is the unit for energy

55
Q

Why is productivity measured per area

A

Per hectare (for example) is used because environments vary in size
standardises results so environments can be compared

56
Q

Why is productivity measured per year

A

More representative of productivity
takes into account effects of seasonal variation (temperature) on biomass environments can be compared with a standardised amount of time

57
Q

Why is energy transfer inefficient from sun -> producer

A

Wrong wavelength of light - not absorbed by chlorophyll
light strikes non- photosynthetic region (bark) light reflected by clouds / dust lost as heat

58
Q

Farming practices to increase energy transfer for crops

A

Simplifying food webs to reduce energy / biomass
herbicides kill weeks -> less competition
fungicides reduce fungal infections
results in more energy used to create biomass
fertilisers such as nitrates to promote growth

58
Q

Why is energy transfer inefficient after producers

A

Respiratory loss - energy used for metabolism (active transport)
lost as heat
not all plant / animal eaten (bones)
some food undigested (faeces)

58
Q

Saprobionts

A

Feed on remains of dead organisms and their waste products (faeces / urea) and break down organic molecules secrete enzymes for extracellular digestion

59
Q

Farming practices to increase energy transfer for animals

A

Reducing respiratory losses (more energy to make biomass)
restrict movement
keep warm
slaughter animal when young (most energy used for growth) selective breeding to produce breeds with higher growth rates

60
Q

Mycorrhizae

A

Symbiotic relationship between fungi and roots of plants
fungi act as extensions of roots increase surface area of system - increasing rate of absorption mutualistic relationship as plants supply fungi with carbohydrates

61
Q

Importance of nitrogen to organisms

A

Used to create
amino acids / proteins
DNA
RNA
ATP

62
Q

Nitrogen cycle stages

A

Nitrogen fixation
nitrification
denitrification
ammonification

63
Q

Nitrogen fixation

A

Nitrogen fixing bacteria break triple bond between two nitrogen atoms in nitrogen gas fix this nitrogen into ammonium ions

64
Q

Nitrogen fixing bacteria

A

Fix nitrogen gas into
ammonium ions
free living in soil
or form mutualistic relationship on root nodules of leguminous plants
give plants N in exchange for carbohydrates

65
Q

Nitrification

A

Ammonium ions in soil are oxidised to nitrite ions nitrite ions are oxidised to nitrate ions
by nitrifying bacteria

66
Q

Denitrification

A

Returns nitrogen in compounds back into nitrogen gas in atmosphere
by anaerobic denitrifying bacteria

67
Q

Ammonification

A

Proteins / urea / DNA can be decomposed in dead matter and waste by saprobionts
return ammonium ions to soil - saprobiotic nutrition

67
Q

Importance of phosphorius

A

Used to create:
DNA
RNA
ATP
phospholipid bilayers
RuBP / GP/ TP

68
Q

Fertilisers

A

Replace nutrients (nitrates and phosphates) lost from an ecosystem’s nutrient cycle when
crops are harvested
livestock removed
can be natural (manure) or artificial (inorganic chemicals)

69
Q

Natural fertilisers advantages

A

Cheaper than artificial fertilisers
often free if farmer has own
animals - recycle manure organic molecules have to be broken down first by saprobionts so leaching less likely

70
Q

Artificial fertilisers advantages

A

Contain pure chemicals in exact proportions
more water-soluble, so more ions dissolve in water surrounding soil.
higher absorption

71
Q

Natural fertilisers disadvantages

A

Exact minerals and proportions
cannot be controlled

72
Q

Artificial fertilisers disadvantages

A

High solubility means larger quantities can leach away with rain
risking eutrophication reduce species diversity as favour plants with higher growth rates e.g., nettles

73
Q

Leaching

A

When water-soluble compounds are washed away into rivers / ponds
for nitrogen fertilisers, this can lead to eutrophication

74
Q

Eutrophication

A

When nitrates leached from fields stimulate growth of algae algal bloom
can lead to death of aquatic organisms

75
Q

How does eutrophication lead to death of aquatic organisms?

A

Algal bloom creates blanket surface of water blocking light plants cannot photosynthesize and die
aerobic bacteria feed and respire on dead plant matter eventually, aquatic organisms die due to lack of dissolved oxygen in water

76
Q

Mutualistic relationships

A

A type of symbiotic relationship where all species involved benefit from their interactions

77
Q

Role of saprobionts in nitrogen cycle

A

They use enzymes to decompose proteins/DNA/RNA/urea
releasing ammonium ions

A-level Biology (8 decks)

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