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A-Level Biology > Module 5: Energy > Flashcards

Module 5: Energy Flashcards

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1
Q

source of energy for an ecosystem

A

sunlight

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2
Q

role of producers

A

photosynthetic organisms
plants
use light energy to make biological molecules

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3
Q

role of consumers

A 
animals
can't make their own biological molecules
eat plants (primary consumer) 
eat other animals (secondary/tertiary)
to obtain biological molecules
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4
Q

decomposers

A

bacteria and fungi
perform saprobiotic decomposition
release enzyme onto dead plants/animals/animal waste
breaking them down into organic matter

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5
Q

why do producers/plants need biological molecules

A

glucose-respiration, store as starch, make cellulose
amino acids- make proteins (enzymes)
fatty acid and glycerol-make triglyceride as energy store, make phospholipid for membranes

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6
Q

why do consumers/animals need biological molecules

A

glucose-respiration, store as glycogen
amino acids-make proteins (enzymes)
fatty acids and glycerol-make triglyceride as energy store and insulation/protection, make phospholipid for membranes

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7
Q

why do decomposers need biological molecules

A

glucose-respiration
amino acids-make proteins (enzymes)
fatty acids and glycerol-make phospholipid for membranes

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8
Q

how do organisms carry energy

A

main source- glucose
stored as starch in plants
stored as glycogen in animals
alternative source-lipids/fats/triglycerides and proteins

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9
Q

how does energy move through an ecosystem

A

by the food chain
producer-primary consumer-secondary-tertiary
decomposers occur at each trophic level

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10
Q

why is all the light energy not utilised by plants in photosynthesis

A

only 2% is used in photosynthesis

rest of light: some misses chloroplast, others reflected by the wrong wavelength

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11
Q

why is energy lost along a food chain

A

respiration
inedible and indigestible parts of plants
stored as starch/glycogen
used to build biomass
10% producer to primary
20% consumer to consumer
consumers more digestible as they aren’t made up of cellulose
higher consumers have higher respiratory losses as they hunt

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12
Q

effect of energy loss on a food chain

A

places a limit on the length of a food chain, those at higher trophic levels (quaternary) wouldn’t obtain enough energy from the food it consumes

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13
Q

productivity

A

amount of glucose/energy available to an organism

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14
Q

primary productivity

A

amount of glucose/energy available to plants

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15
Q

secondary productivity

A

Amount of glucose/energy available in animals

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16
Q

Net primary productivity equation

A

Gross productivity - respiratory losses

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17
Q

Gross primary productivity

A

Amount of glucose made by a plant in photosynthesis

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18
Q

What is net primary productivity

A

Amount of glucose stored as starch after respiration

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19
Q

Gross secondary productivity

A

Amount of glucose consumed by animal

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20
Q

Net secondary productivity

A

Amount of glucose stored as glycogen after respiration

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21
Q

When are respiratory losses higher

A

In consumers than producers due to movement
Higher in secondary/tertiary/quaternary consumers as they move more to hunt for food
Higher in consumers that have to maintain constant body temperature (endotherms)

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22
Q

What does a pyramid of number represent

A

Number of each type of organism at each trophies level- numbers decrease as we move up trophic levels due to loss of energy (not as many can be supported)
Can look inverted when it doesn’t take mass into account

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23
Q

What does a pyramid of biomass represent

A

biomass of each type of organism at each trophic level
Move up food chain loss of energy due to respiration/inedible parts/indigestible parts so less energy to build up biomass so biomass decreases

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24
Q

Biomass

A

Mass of living tissue (based on dry mass, water excluded)

g per m2 for land based or g per m3for water based

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25
Q

What does a pyramid of energy represent

A

Amount of energy found at each trophic level

As before loss of energy occurs along a food chain

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26
Q

How is energy lost in a food chain

A

Respiration
Inedible parts
Indigestible parts

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27
Q

Units for energy

A

kJ/m2/year

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28
Q

What is photosynthesis

A

Uses light energy to make glucose

Occurs in plants and algae

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29
Q

Adaptation of plant for photosynthesis

A

Leaf at top of plant=closer to light
Thin and wide= large SA, short diffusion distance
Veins= connect to xylem
Stomata=gas exchange
Palisade cells= top of leaf, large,thin cell wall, many chloroplasts and large vacuole (pushes chloroplasts to edge of cell closer to light)

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30
Q

Structure of chloroplasts

A 
Site of photosynthesis 
Double membrane
Thylakoids discs 
Stacks of thylakoids=granum
Thylakoids surrounded by fluid called stroma
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31
Q

2 stages of photosynthesis

A

Light dependent

Light independent

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32
Q

Light dependent brief

A

On thylakoids
Makes ATP
reduced NADP

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33
Q

Light independent brief

A

In stroma
Uses ATP and reduced NADP
makes glucose

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34
Q

Light dependent stage

A

Light strikes chlorophyll and is absorbed
Pair of electrons become excited and leave chlorophyll (photoionised)
Electrons enter ETC, move down system releasing energy
Protons from stroma into thylakoid space
Protons accumulate in thylakoid space, diffuse back into stroma
Pass through ATP synthase channel (chemiosmosis) which joins ADP and Pi to ATP, photophosphorylation
Electron joins NADP to form reduced NADP
light strikes water molecule
Causes photolysis
Forms H+, e- and O2
H+ joins reduced NADP (carries hydrogen atom)
e- replaces electrons lost from chlorophyll
O2 is waste

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35
Q

Light independent stage

A

Involves Calvin cycle
RuBP (5C) joins CO2 to make 2 glycerate 3 phosphate (GP)
GP reduced to triose phosphate (TP)
Uses energy from ATP and hydrogen atom from reduced NADP
TP can be used to reform RuBP (uses energy from ATP)
TP used to form glucose
GP used to form amino acids and fatty acids
TP used to form glycerol
Fatty acids and glycerol form lipid

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36
Q

process of chemiosmosis

A

pumping protons through special channels in the membranes of the mitochondria
from inner to outer compartment
establishes a H+ gradient
after gradient is established, proteins diffuse down gradient using ATP synthase channel

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37
Q

limiting factors for photosynthesis

A

light
CO2
temperature

increase any of these then the rate of photosynthesis increases

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38
Q

effect of limiting light on the calvin cycle

A

RuBP decreases- being converted into GP but not being reformed from TP (no ATP)
GP increases- not converted into TP (no ATP/reduced NADP) but is being formed from RuBP

39
Q

effect of limiting CO2 on the calvin cycle

A

RuBP increases- not converted into GP (no CO2) but is being reformed from TP
GP decreases- not being formed from RuBP (no CO2) but being converted into TP

40
Q

products of the light dependent reaction

A

ATP

NADPH

41
Q

products of the light independent reaction

A

glucose
NADP+
ATP
inorganic phosphate

42
Q

what is the compensation point in plants

A

point in the day (light intensity) when the CO2 taken in by photosynthesis equals the amount given out by respiration= no net gas exchange
at low light intensity: rate of respiration > rate of photosynthesis (CO2 released)
at high light intensity: rate of photosynthesis> rate of respiration (CO2 absorbed)

43
Q

how to measure the rate of photosynthesis

A

measure amount of CO2 used or measure amount of O2 produced, in a certain time
use a photosynthometer

44
Q

how does a photosynthometer work

A

measures amount of O2 produced
uses aquatic plants as the O2 produced can be observed and collected
plant is surrounded in sodium hydrogencarbonate solution (CO2 source)
plant is kept in darkness before experiment begins (remove all O2)
as experiment runs O2 will be produced, collect in a capillary tube
amount collected can be measured , converted into a volume by multiplying length of oxygen bubble by pi r^2
volume O2 collected can be divided by time to find rate of photosynthesis

45
Q

structure of ATP

A 
adenosine triphosphate
1 adenosine, 3 phosphates
energy carrier molecule 
ADP + Pi (+energy used) -> ATP
condensation reaction using ATP synthase 
carries energy in its bonds 
ATP-> ADP + Pi (+energy released)
hydrolysis reaction using ATP hydrolase (ATPase)
46
Q

what is GP

A

glycerate 3 phosphate

47
Q

what is TP

A

triose phosphate

48
Q

how can ATP be formed

A

photophosphorylation (light dependent stage of photosynthesis)
substrate-level phosphorylation (glycolysis and krebs cycle of respiration)
oxidative phosphorylation (electron transport chain of respiration)

49
Q

what makes ATP (from respiration) a good source of energy

A 
immediate= need to only break one bond to release energy, bond is weak 
manageable= releases small amount of energy
50
Q

uses of ATP (made in respiration) in organisms

A 
proteins synthesis 
organelle synthesis 
DNA replication
cell division
active transport 
metabolic reactions
movement 
maintaining body temperature
51
Q

what is respiration

A

releasing energy from glucose to make ATP
ATP will provide energy for life processes
occurs in all living organisms
ATP can be made by substrate level phosphorylation (glycolysis and krebs cycle) and oxidative phosphorylation (electron transport chain)

52
Q

2 types of respiration

A

aerobic

anaerobic

53
Q

4 stages of aerobic respiration

A

glycolysis
link reaction
krebs cycle
oxidative phosphorylation

54
Q

glycolysis

A

occurs in cytoplasm
glucose is phosphorylated to make it more reactive (uses 2 ATP)
glucose is split into 2 triose phosphates
hydrogen is removed and reduced NAD
triose phosphate turned into pyruvate, regenerates 2 ATP

uses glucose to produce 2x pyruvate, 2x ATP and 2x reduced NAD
pyruvate enters link reaction
ATP made by substrate-level phosphorylation
reduced NAD is used in ETC

55
Q

link reaction

A

occurs in matrix of mitochondria
pyruvate oxidised to acetate, decarboxylated and dehydrogenated
2x H reduce NAD
acetate combines with coenzyme A to produce acetyl co enzyme A

pyruvate + coenzyme A + NAD -> acetylcoenzyme A + reduced NAD + CO2
acetylcoenzyme A is used in Krebs
reduced NAD used in ETC
CO2 is given of as waste

56
Q

krebs cycle

A

occurs in the matrix of the mitochondria
acetyl coenzyme A from link combines with 4 carbon molecule
dehydrogenated and decarboxylated twice
to reform 4 carbon molecule
hydrogen reduces NAD and FAD

uses acetylcoenzyme A to produce 3x reduced NAD, 1 x reduced FAD, 1x ATP, 2x CO2
reduced NAD and reduced FAD are used in ETC
ATP is made by substrate-level phosphorylation
CO2 given off as waste

57
Q

oxidative phosphorylation/ETC

A

takes place on the inner membrane of the mitochondria (cristae)
hydrogen atoms produced in glycolysis and krebs combine with coenzymes NAD and FAD
donate H to ETC
down ETC with redox reactions
energy released causes active transport of protons across inner mitochondrial membrane and into inner-membranal space
accumulate in inner-membranal space before diffusing back into matrix through atp synthase channels
at the end of the chain electrons protons and oxygen combine to form water
oxygen is the final acceptor

58
Q

Anaerobic respiration

A

no oxygen present so no final electron acceptor
Electron transport chain stops
Krebs and link also stop as NAD and FAD aren’t reformed
Glycolysis continues as it forms its own NAD
anaerobic respiration only relies on glycolysis (2 ATP by substrate level phosphorylation)
NAD reformed from reduced NAD made in glycolysis
Reduced NAD donates hydrogen atom H+/e- to pyruvate to reform NAD
In animals pyruvate becomes lactate (lactic acid)
In plants/yeast pyruvate becomes ethanol and CO2

59
Q

How to measure rate of respiration

A

Measure amount of O2 used or measure amount of CO2 produced in a certain time
Respirometer

60
Q

How does respirometer work

A

Measure amount of gas exchange taking place between organism and air in a test tube
Test tube connected to manometer
Organism more O2 in then air in test tube decreases, less pressure so liquid moves towards test tube
Organism more CO2 out, more pressure so liquid moves away
Amount/volume by which coloured liquid moves represents volume of gas taken in/given out

61
Q

What are respiratory substrates

A

Carbohydrates are turned into glucose
Proteins, excess amino acids converted into keto acid (turned into pyruvate and intermediates of krebs)
Lipids turn into fatty acids which turn into acetyl co enzyme a, glycerol turns into triode phosphate

62
Q

Value of nitrogen to organisms

A

Amino acids
Proteins
Nitrogenous bases in DNA

63
Q

nitrogen cycle

A

nitrogen fixation:

  • nitrogen gas to nitrogen-containing compounds
  • uses free living nitrogen fixing bacteria and mutualistic nitrogen-fixing bacteria
    - free-living: reduce gaseous nitrogen to ammonia, manufacture amino acids, release nitrogen rich compounds when they die and decay
    - mutualistic: live in nodules on roots, obtain carbohydrates from plant and plant acquires amino acids from bacteria

ammonification:
- organic material broken down by saprobiotic decomposers
- releases NH4+ back into the soil

nitrification:

  • uses nitrifying bacteria, require oxygen so in soil with lots of air spaces
  • ammonium to nitrate ions
  • oxidation of ammonium to nitrite(NO2-)
  • nitrite to nitrate (NO3-)

denitrification:

  • nitrate back to nitrogen gas by denitrifying bacteria
  • anaerobic conditions
  • waterlogged field and all air spaces filled with water
64
Q

value of phosphorus to organisms

A

phospholipids
DNA
ATP

65
Q

Describe the phosphorus cycle

A

Phosphorus present in sedimentary rocks as phosphate ions
When sedimentary rocks erodes leaves the soil containing the phosphate ions
Plants absorb the ions to make phospholipids/DNA/ATP
Consumers eat plants to obtain the phospholipids/DNA/ATP
Organic material is broken down by Sa probiotic decomposers, releasing the phosphate ions back unto the soil
Over time the soil sediments and hardens returning to a rock state

66
Q

What are mycorrhizae

A

Fungi inn the roots of plants to support uptake of scarce materials like phosphate ions

67
Q

Agricultural ecosystem

A

Description for farming ecosystems
Aim of farms is to grow crops and raise animals
Grow crops to sell and feed farm animals
Raise animals to sell meat and other resources

68
Q

How are crops intensively farmed for high yield

A

Select suitable location
Clear area of plants and animals
Selectively breed the corp
Use greenhouse to provide high levels of light,CO2 and temperature
Provide water by irrigation
Add fertilizers
Control pests
Polyculture/ crop rotation (so minerals don’t become depleted)
Ploughing (add air spaces to soil so bacteria can aerobically respire)

69
Q

What are pests

A

Organisms that harm plants/ crops

Other plants e.g. weeds act as competitors, insects eat the plant and fungi cause disease

70
Q

How can pests be controlled

A

Pesticides or biological control

71
Q

What are pesticides

A

Chemical sprays that kill the pest
Weeds= herbicide
Insects= insecticide
Fungi= fungicide

72
Q

Advantages of using pesticides

A

Fast acting

Can control the area covered

73
Q

Disadvantages of using pesticides

A

Non-specific
Non- biodegradable which leads to bioaccumulation and toxicity in the higher trophic levels
Pest may be resistant
Needs to be reapplied

74
Q

What is biological control

A

Using predators or parasites to the pest

75
Q

Advantages of using biological control

A

Specific
Doesn’t cause bioaccumulation
Pests do not develop resistance
Doesn’t need to be reappplied

76
Q

Disadvantages of using biological control

A

Slow acting
May become a pest itself
Can’t control the area covered

77
Q

What is bioaccumulation

A

Pesticides aren’t biodegradable
Remain stored in the organisms tissues
They accumulate up the trophic levels
Toxic to the consumers at higher trophic levels

78
Q

What is an integrated pest control system

A

Makes use of both pesticides and biological control

Keep some native trees
Monitor area for pests
Mechanically remove pests if present
Initial dose of pesticide is fast acting
Then apply biological control- will increase in number over time and provide long term control
Reapply pesticides whenever there is an uncontrollable outbreak

79
Q

What minerals do fertilizers provide

A 
Nitrate= make amino acids and nitrogenous bases 
Phosphates= make ATP, DNA and phospholipids 
Magnesium= make chlorophyll
80
Q

2 types of fertilizers

A

Natural

Artificial

81
Q

Natural fertilizers

A

Applying dead plants/animals/animal waste

Decomposed leading to ammonifiation, followed by nitrification to provide source of no3-

82
Q

Artificial fertilizers

A

Spraying on concentrated solutions of the minerals

83
Q

Natural vs artificial fertilizers

A 
Natural= reduced risk of leaching/eutrophication bu slower release of minerals 
Artificial= faster release of minerals and higher concentration but risk of leaching/eutrophication and lowers the water potential of the soil so plant absorbs less water by osmosis
84
Q

Benefit of ploughing

A

Increases amount of air spaces in the soil

Supports aerobic respiration of decomposers and bacteria involved in the nitrogen cycle

85
Q

Eutrophication process

A

If large amounts of chemical fertilizers are sprayed onto fields and heavy rainfall occurs the fertilizer may leach into local water sources
Fertilizer will travel and build up in ponds or lakes
Mineral will be absorbed and used by algae
Leads to an increase growth of algae=algal bloom
Algae grows on the upper surface of the water which prevents light reaching the plants at the bottom of the water
Light becomes the limiting factor so no photosynthesis
Plants die
Provide more nutrients to saprobiotic decomposers so they increase in number
Aerobically respire so oxygen becomes the limiting factor
Fish unable to respire so die
Provides more nutrients
Oxygen concentration too low so water turns putrid

86
Q

Deforestation impact on crop farming

A

Reduces species diversity
Reduces plant species diversity
Less habitats and food sources
Reduces animal species diversity

87
Q

Monoculture impact on crop farming

A

One type of plant

Depletes certain nutrients in the soil (no time provided for nutrient levels to recover)

88
Q

Selective breeding impact on crop farming

A

Reduces genetic diversity of crop

Reduces variation and reduces the ability to adapt to changes in the environment

89
Q

Pollution impact on crop farming

A

Bioaccumulation of pesticides

Eutrophication from chemical fertilizers

90
Q

Reducing the environmental impact of crop farming

A

Keep some native trees (species diversity)
Keep hedgerows (species diversity and absorb chemical fertilizers reducing eutrophication)
Polyculture (grow different crops at different times of the year, allows depleted nutrients in the soil to recover)
Keep seeds of wild crop (maintain genetic diversity, use if the environment changes)
Uses biological control for pests an natural fertilizers for minerals

91
Q

How are animals intensively reared in farming

A

Selectively bred
Given predigested food (enzymes added) with high protein and high energy levels
Given antibiotics and vaccinations
Given steroid hormones
Restricted movement andrkept warm to reduce energy levels

92
Q

Natural ecosystem

A 
Light energy source
High biodiversity 
High species diversity 
High genetic diversity 
Low productivity 
Nutrient recycled 
Competition/predators control pests 
Reaches climax community
93
Q

Artificial ecosystem (farming)

A 
Light and food for farmer and fossil fuel for machines as energy sources 
Low biodiversity 
Low species diversity 
Low genetic diversity 
High productivity 
Nutrients are added via fertilizers 
Pesticides/biological control to control pests 
Prevent climax community being reached

A-Level Biology (14 decks)

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