all Flashcards
(211 cards)
1
Q
describe a prokaryotic cell(2)
A
lacks membrane-bound organelles - the cell contents are suspended in cytoplasm
nuclear region (nucleoid) is not surrounded by a membrane
2
Q
describe a eukaryotic cell
A
has membrane-bound organisms
nuclear region (nucleus) is surrounded by a nuclear membrane
3
Q
define catabolims
A
cellular energy production
complex molecules release energy and become simple molecules
4
Q
define anabolism
A
external carbon substrate molecules use energy to make new cellular material
5
Q
define metabolsm
A
the sum of catabolism and anabolism catalysed by enzymes
6
Q
explain the diff between ATP and NADH,FADH2
A
ATP
- Ready-to-use energy for the cell.
-Use it immediately to power things like muscle movement, nerve signals, and building molecules.
-It’s fast and convenient
NADH,FADH2
- stored energy you cant use it straight away.
-You first need to turn them into ATP.
- stores energy more efficiently
7
Q
how are catabolism and anabolism linked
A
catabolism releases energy which coverts ADP into ATP and anabolism breaks down ATP into ADP
8
Q
what are the 3 steps in energy production and explain each one(bio)
A
Glycolysis - first step in respiration of sugar 6carbons to 3 carbons
both ATP and NADH released but more NADH
Krebs - series of reactions which release ATP and NADH(more) from citric acid
uses 3 carbons
Electron transport - converts NADH to ATP with an electron acceptor eg. O2
9
Q
how do eukaryotes and prokaryotes reproduce
A
eukaryotes -asexual and sexual - mitosis/ meiosis
prokaryotes - asexual - binary fission very fast
10
Q
what are the 3 types of aerobes
A
=>Facultative anaerobes
They do not need oxygen (O₂) to survive, but they can use it if it’s available.
If oxygen is present, they grow better (because oxygen allows more efficient energy production).
If oxygen is missing, they switch to using alternative electron acceptors (other chemicals) to survive
=>Obligate aerobes
They must have oxygen to live and grow.
They cannot survive without oxygen.
=>Obligate anaerobes
They cannot tolerate oxygen at all — oxygen is actually toxic to them.
They only use alternative electron acceptors (not oxygen) to make energy.
If they are exposed to oxygen, they die.
11
Q
molarity eq
A
moles/volume(liters)
12
Q
normality eq
A
Mr/charge
how much of a substance you need to have a mole of a certain charge
13
Q
what is the henrys law equation
A
Concentration of gas = Kh * partial pressure of gas
14
Q
what is a gene
A
a segment of DNA that encodes the synthesis of messenger RNA (mRNA)
15
Q
What happens in transcription
A
gene coding DNA segment is copied into mRNA
The mRNA encodes the synthesis of enzyme/protein
16
Q
what happens in translation
A
mRNA is decoded by rRNA to produce protein/enzyme
17
Q
what is rRNA
A
Ribosomal RNA - a complex RNA-protein macromolecule found in all living cells which can read the mRNA and synthesize protein
18
Q
what is the importance of hydrogen bonds in DNA
A
Weak bonds allow DNA strands to separate for replication/transcription.
19
Q
what do proteins do
A
act as enzymes, structural components, and catalysts for reactions
20
Q
what is tRNA
A
transfer RNA transfers an amino acid with 3 codons into a growing protein chain
21
Q
what does 16S rRNA sequencing tell you
A
microbe’s identity - Who are you?
contains unique “fingerprint” regions that are specific to different types of bacteria
22
Q
what does metagenomics tell you
A
The potential functions and capabilities of the community - What can you do?
Sequences all the DNA
Identify all the genes present within the microbial community
23
Q
what does metatranscriptomics tell you
A
what are you doing?
gives us a snapshot of the active metabolic processes and pathways within the community
24
Q
what does Proteomics tell you
A
Provide direct information about the functional activities occurring within the community, including enzyme activity and even insights into the three-dimensional structures of these proteins
25
Advantages of Bioinformatics
- handle big data
- Accelerates research
- cost effective
-Facilitates Predictive Modelling
26
in Gibbs free what does it mean if delta G is +/-
Negative is spontaneous/favourable
positive is non spontaneous/unfavourable
27
what are the 4 water pollution control objectives and explain each one
health - minimise risk of disease transmission by water-borne route
Ecology - Minimise risk to natural ecological balance of receiving water
Aesthetic - maintaining value of water for recreational activities
Economics - Provide an appropriate level of treatment to achieve environmental protection at a reasonable cost
28
what are the 4 steps in waste treatment and explain each one
- Preliminary - screening removes solid matter
- primary settlement removes suspended soils as sewage sludge
- secondary biological treatment and settlement reduces the organic matter content using oxygen as the electron acceptor and organic matter as the donor
-tertiary treatment effluent polishing step reduce the load of micro organisms and/or nutrients in the effluent
29
How can you determine the reactivity of an atom like Oxygen (8 electrons)?
Calculate valence electrons (O: 2 in 1st shell, 6 in valence shell). Apply Octet Rule (needs 8). Since it needs 2 more electrons, it's reactive. Valency = 8-6 = 2.
30
Define 'molecule' and 'compound' and state the key difference.
Molecule: Stable association of 2+ atoms (can be same or different elements). Compound: Molecule with atoms of at least two different elements. Key difference: Compounds must have different elements, molecules don't have to.
31
How is chemical bond type (ionic, polar covalent, non-polar covalent) determined using electronegativity?
By the difference in electronegativity between bonding atoms. Large difference (> ~1.8) -> Ionic. Moderate difference (~0.4-1.8) -> Polar Covalent. Small difference (< ~0.4) -> Non-polar Covalent. (Values/scale likely provided if needed).
32
Explain key properties of water (e.g., high specific heat, density anomaly) by linking them to a specific type of bonding.
Water's unique properties (high specific heat, high heat of vaporization, ice less dense than water) are primarily due to extensive hydrogen bonding between water molecules, which requires significant energy to break or forms specific structures (like in ice).
33
What is the difference between covalent bonds and hydrogen bonds in water, especially regarding location and strength?
Covalent bonds (O-H) are within a single water molecule and are strong. Hydrogen bonds are between neighbouring water molecules, are weaker than covalent bonds, and are responsible for many of water's bulk properties.
34
What are the basic definitions of oxidation and reduction in terms of electron transfer and associated energy change?
Oxidation: Loss of electrons, energy is lost by the species. Reduction: Gain of electrons, energy is gained by the species.
35
Understand that the periodic table organizes elements by properties related to electron configuration. If needed for an exam question, relevant parts or information will likely be provided
The periodic table groups elements with similar chemical properties, often based on the number of valence electrons. Relevant data (electron counts, electronegativity) will be provided if needed for calculations.
36
What are the key structural differences between prokaryotic and eukaryotic cells?
Prokaryotes lack a membrane-bound nucleus and other membrane-bound organelles (DNA in nucleoid region). Eukaryotes have a true nucleus containing chromosomes and possess membrane-bound organelles like mitochondria.
37
Define metabolism, catabolism, and anabolism. What are the roles of ATP and NADH/FADH2?
Metabolism: Sum of all biochemical reactions. Catabolism: Breakdown of complex molecules, releases energy. Anabolism: Synthesis of complex molecules, requires energy. ATP: Main energy "currency". NADH/FADH2: Electron carriers storing energy for later ATP production.
38
List the 3 main stages of aerobic cellular respiration in sequence and state the basic purpose/key outputs of each.
Glycolysis (breaks glucose to pyruvate, yields small ATP/NADH).
2. Krebs Cycle/TCA Cycle (completes breakdown, yields CO2, small ATP, much NADH/FADH2).
3. Electron Transport Chain (ETC) (uses NADH/FADH2, O2 as final acceptor, produces large amount of ATP via oxidative phosphorylation
39
What is the role of Oxygen in the Electron Transport Chain (ETC) and ATP production?
Oxygen serves as the final electron acceptor at the end of the ETC. This process drives the production of the majority of ATP during aerobic respiration.
40
What is fermentation, under what conditions does it occur, and what is its main purpose besides yielding minimal ATP?
Fermentation is an anaerobic process (no O2) following glycolysis. Its main purpose is to regenerate NAD+ from NADH, allowing glycolysis to continue producing small amounts of ATP. It yields much less energy than aerobic respiration.
41
How are humans and plants classified based on their energy and carbon sources?
Humans: Chemoheterotrophs (Energy & Carbon from organic compounds). Plants: Photoautotrophs (Energy from light, Carbon from CO2).
42
What is the primary mode of prokaryotic reproduction? What is the main advantage of sexual reproduction seen in many eukaryotes?
Prokaryotes primarily reproduce via Binary Fission (asexual). The main advantage of sexual reproduction is increased genetic diversity, enhancing adaptation to changing environments.
43
Define: Obligate Aerobe, Obligate Anaerobe, and Facultative Anaerobe based on oxygen requirements.
Obligate Aerobe: Requires O2. Obligate Anaerobe: Cannot tolerate O2. Facultative Anaerobe: Can grow with or without O2, but prefers O2.
44
Name the basic categories of microbes based on their optimal growth temperature.
Psychrophiles (cold), Mesophiles (moderate), Thermophiles (hot), Hyperthermophiles (extreme hot).
45
How do high salt or sugar concentrations in the environment typically inhibit microbial growth?
High external solute concentrations create a hypertonic environment, causing water to leave the cell (osmotic stress/dehydration) and reducing available water activity, thus inhibiting growth.
46
Define solubility, solvent, solute, unsaturated, saturated, supersaturated solutions, and precipitation.
Solubility: Max solute dissolved in solvent. Solvent: Dissolving medium.
Solute: Substance dissolved. Unsaturated: Can dissolve more solute.
Saturated: Max solute dissolved at equilibrium.
Supersaturated: More solute dissolved than normal limit (unstable). Precipitation: Solute forming solid from solution.
47
Explain how increasing temperature generally affects the solubility of solids vs. gases in liquids.
increasing temperature generally increases the solubility of most solids (more energy to dissolve). However, it decreases the solubility of gases (more energy allows gas to escape the liquid).
48
What is Molarity (M) and how is it calculated?
Molarity is moles of solute per litre of solution (mol/L). M = (grams of solute / Molecular Weight) / Litres of solution.
49
What is the principle of charge balance (electroneutrality) in a solution?
The total positive charge from cations must equal the total negative charge from anions, making the bulk solution electrically neutral.
50
How is a charge balance calculation typically performed to check water analysis accuracy?
Convert major ion concentrations to equivalents/L (e.g., mg/L / EW). Sum positive equivalents (cations) and negative equivalents (anions). The two sums should be approximately equal.
51
How do you write the equilibrium constant expression (Keq or Ksp)? What types of substances are typically omitted?
Keq = [Products]^coeffs / [Reactants]^coeffs. Pure solids and pure liquids (like water as solvent) are omitted from the expression. For Ksp of solids, only the aqueous ion products are included.
52
Given the Ksp for a sparingly soluble salt like CaF2 (Ksp = [Ca2+][F-]^2), how can you calculate its molar solubility 's'?
Set up concentrations in terms of 's' based on stoichiometry (e.g., [Ca2+]=s, [F-]=2s). Substitute into the Ksp expression (Ksp = s * (2s)^2 = 4s^3) and solve for 's'.
53
What does Henry's Law state about gas solubility? What is the basic equation?
Gas solubility in a liquid is directly proportional to the partial pressure of that gas above the liquid. Equation: C = kH * Pgas (C=concentration, kH=Henry's constant, Pgas=partial pressure).
54
Understand the concept behind Normality and equivalent weight, particularly for charge balance calculations.
Normality (N) is equivalents per litre. Equivalent weight (EW = MW/valence) relates mass to reacting units or charge. It's used to ensure positive and negative charges balance in solutions by comparing total equivalents of cations and anions.
55
State the central principle of molecular biology, including the two main processes involved.
DNA → (Transcription) → RNA → (Translation) → Protein.
56
What are the key structural and compositional differences between DNA and RNA?
DNA: Deoxyribose sugar, bases A, G, C, T, typically double-stranded. RNA: Ribose sugar, bases A, G, C, U, typically single-stranded.
57
What is the role of hydrogen bonds in the structure and function of DNA?
Hydrogen bonds hold the two strands of the DNA double helix together via specific base pairing (A-T, G-C). They are weak enough to allow strands to separate for replication and transcription.
58
Describe the roles of mRNA, ribosomes (rRNA), and tRNA during translation.
mRNA carries the genetic code from DNA. Ribosomes are the site of protein synthesis, reading the mRNA codons. tRNA molecules transport the specific amino acids corresponding to the mRNA codons to the ribosome.
59
What is a codon?
A sequence of three consecutive nucleotide bases on an mRNA molecule that specifies a particular amino acid or a start/stop signal during translation.
60
Define Genomics, Transcriptomics, and Proteomics. What level of functional insight does each provide?
Genomics: Study of genome (DNA); shows potential function. Transcriptomics: Study of transcriptome (RNA); shows genes currently expressed (activity preparation). Proteomics: Study of proteome (proteins); shows proteins present and potentially active functions.
61
Why is the 16S rRNA gene commonly used as a marker for bacterial and archaeal identification?
It's universally present, essential (conserved regions for primers), and contains hypervariable regions that differ between taxa, allowing for taxonomic discrimination
62
Outline the main steps in a typical 16S rRNA gene sequencing workflow for microbial community analysis
1.DNA Extraction.
2. PCR Amplification (of 16S gene region).
3. Sequencing.
4. Bioinformatics (Quality control, feature generation/clustering, taxonomic classification against database, relative abundance calculation).
63
What specific information about a microbial community does 16S rRNA gene sequencing primarily provide?
It identifies which bacterial/archaeal taxa are present ('who is there') and their relative abundance within the community.
64
Which 'omics' technique (16S rRNA, Metagenomics, Metatranscriptomics) is most suitable for determining the actively expressed functions of a microbial community at a specific time?
Metatranscriptomics (sequences all expressed RNA)
65
How does the sign of Gibbs Free Energy change (ΔG) indicate the spontaneity of a reaction?
ΔG < 0 (negative): Spontaneous (favorable, releases energy). ΔG > 0 (positive): Non-spontaneous (unfavorable, requires energy input). ΔG = 0: Equilibrium.
66
How do you calculate the overall standard free energy change (ΔG°') for a redox reaction using tabulated half-reaction free energies?
Identify reduction and oxidation half-reactions. Reverse the oxidation half-reaction and reverse the sign of its ΔG°'. Sum the ΔG°' of the reduction half (as is) and the reversed oxidation half.
67
Why is Oxygen (O2) the preferred electron acceptor in many environments? What is the general sequence of electron acceptor utilization as conditions become more reducing?
O2 yields the most energy (most negative ΔG) when used in respiration. Sequence: O2 > NO3- > Mn(IV) > Fe(III) > SO4^2- > CO2 (for methanogenesis).
68
What is the basic redox principle underlying the corrosion of iron (rusting) or concrete sewer pipes
A substance (Iron metal or H2S gas) is oxidized (loses electrons), while another substance (Oxygen or intermediate sulfur compounds) is reduced (gains electrons), leading to the degradation of the material.
69
Define pH and explain its relationship to acidity and alkalinity.
pH = -log10[H+]. pH < 7 is acidic, pH = 7 is neutral, pH > 7 is basic/alkaline. Lower pH means higher acidity ([H+])
70
What do Ka and pKa represent, and how do they indicate the strength of a weak acid?
Ka is the acid dissociation constant. pKa = -log10(Ka). A larger Ka (smaller pKa) indicates a stronger weak acid (dissociates more readily).
71
How can the Ka expression (Ka = [H+][A-]/[HA]) be used to find the pH or [H+] of a weak acid solution?
If Ka and equilibrium concentrations of [HA] and [A-] are known (or can be determined, e.g., using 's' or initial conc. minus 'x'), the equation can be solved for [H+], and then pH calculated using pH = -log10[H+].
72
What is the Henderson-Hasselbalch equation and what is it used for?
pH = pKa + log10([A-]/[HA]). It's used to calculate the pH of a buffer solution given the pKa of the weak acid and the concentrations of the acid [HA] and its conjugate base [A-].
73
Define a buffer solution. What is its main function and typical composition?
A solution that resists changes in pH upon addition of small amounts of acid or base. Typically composed of a weak acid and its conjugate base (or weak base/conjugate acid).
74
What is the key chemical species responsible for buffering capacity in most natural waters?
Bicarbonate ion (HCO3-).
75
What is the approximate pH of natural rainwater in equilibrium with the atmosphere, and why is it not neutral (pH 7)?
Approx. pH 5.6-5.7. It's acidic because atmospheric CO2 dissolves in water to form carbonic acid (H2CO3), which then releases H+ ions.
76
Which carbonate species (H2CO3, HCO3-, CO3^2-) is typically dominant in natural waters (around neutral pH)
Bicarbonate (HCO3-).
77
Define alkalinity. What chemical species are the main contributors? How does it differ conceptually from buffering?
Alkalinity is the acid-neutralizing capacity of water. Main contributors are HCO3-, CO3^2-, and OH-. Buffering resists pH change from both acid and base, while alkalinity specifically measures resistance to acid
78
Define water hardness. What are the primary ions responsible for it?
Hardness is primarily caused by the presence of dissolved divalent cations, mainly Calcium (Ca2+) and Magnesium (Mg2+).
79
Describe the main problems associated with hard water. Why does scale typically form when hard water is heated?
Problems: Soap scum formation (reduces cleaning), scale deposits in pipes/heaters. Scale (CaCO3) forms upon heating because increased temperature reduces CO2 solubility, shifting carbonate equilibrium to favor precipitation of CaCO3.
80
Explain the principle behind removing dissolved heavy metals from wastewater by increasing the pH.
Increasing the pH increases the hydroxide ion [OH-] concentration. This causes many dissolved metal ions (like Zn2+, Cu2+) to exceed their solubility product constant (Ksp) for metal hydroxides (e.g., Zn(OH)2), leading them to precipitate out as solids which can then be removed.
81
List and briefly explain the four main objectives of wastewater treatment
1. Public Health (Minimize disease). 2. Environmental Protection (Protect receiving waters). 3. Recreation (Maintain water quality). 4. Economics (Cost-effective treatment).
82
Describe the main purpose of each major wastewater treatment stage (Preliminary, Primary, Secondary, Tertiary).
Preliminary: Remove large solids/grit. Primary: Settle suspended solids. Secondary: Remove dissolved organics (BOD) biologically. Tertiary: Polish effluent (nutrient removal, disinfection).
83
Explain the basic role of aerobic respiration (catabolism using O2) in the biological (e.g., aeration) tank for removing pollutants
Microbes use dissolved organic pollutants (electron donor) and supplied oxygen (electron acceptor) via aerobic respiration to generate energy and grow, converting pollutants into CO2, H2O, and new cells (sludge), thus removing BOD.
84
Why is providing oxygen (aeration) effective for wastewater treatment, explained using the concept of Gibbs Free Energy?
Using Oxygen (O2) as the electron acceptor in respiration yields the most free energy (most negative ΔG) compared to other acceptors, making the breakdown of organic matter thermodynamically favorable and efficient.
85
How are anaerobic processes utilized in sludge treatment?
Anaerobic digestion breaks down sludge organic matter in the absence of oxygen, producing biogas (methane) as a renewable energy source, while stabilizing the sludge.
86
Describe the basic mechanism, key advantages, and key disadvantages of attached growth systems like Trickling Filters.
Mechanism: Biofilm on media, passive aeration. Adv: Simple, low energy cost, robust. Disadv: Large footprint, potential odor/clogging, less control.
87
Describe the basic mechanism, key advantages, and key disadvantages of suspended growth systems like Activated Sludge.
Mechanism: Flocs suspended in aeration tank + clarifier + sludge recycle. Adv: Good control, smaller footprint, flexible. Disadv: High energy cost (aeration), complex operation, sensitive to shocks, potential settling issues.
88
why don't we use groundwater as much
contains Ca2+ and Mg2+
89
describe the process of waste water leaving house/industry and what each step is
bar screen - Removes large objects like sticks, rags, plastic, and other debris
grit tank -Removes heavy inorganic materials like sand, gravel, and small stones.
Setting tank - Allows solids to settle at the bottom, forming sludge, while oils and grease float to the top.
Either a digester - Treats sludge anaerobically (without oxygen) using bacteria.
Produces biogas (mainly methane), which can be used for electricity or heat.
Leftover material is disposed of or used as fertiliser after further treatment.
or aeration tank - Adds air to support bacteria that break down organic matter in the water.
if digester then disposed or used for electricity/heat
if aeration then clarifier -Allows remaining solids (mostly bacterial biomass) to settle out.
and and finally the UV and chlorine added and sent back into houses
90
explain the catabolism of the aeration tank
glucose is broken down into pyruvic acid producing small amounts of ATP and more NADH which carry electrons
Pyruvic acid enters the mitochondrion and is converted to Acetyl CoA this is broken down in the Krebs Cycle and produces CO2 more NADH and ATP
NADH carries electron to the electron transport chain where they move through a series of protons releasing energy used to produce ATP
91
explain attached growth and suspended growth systems
attached growth - Microorganisms grow as a biofilm attached to a solid surface. Wastewater flows over or around the surface, allowing bacteria to consume organic pollutants.
suspended growth - Microorganisms are suspended in the wastewater itself, not attached to any surface
92
give adv and disadv for attached growth
adv:
Simple operation
* Low maintenance
* Low energy use (30-50%
less than activated sludge)
* Reliable
* Sloughed biomass easily
removed by sedimentation
* Treat industrial WW
* Buffered to withstand shock
loadings
– Contaminants
– Excessive nutrients
* Biomass retained therefore
not susceptible to wash-out
disadv
Filter clogging due to
excessive microbial growth
* Potential odours
* Fly nuisance
* Difficult to control
* Poorer operation in cold
conditions
* Requires pretreatment and
primary sedimentation
93
give adv and disadv for suspended growth systems
Advantages
– Increased process control
– Flexible as different redox environments created by
reactor design – eg enhanced nutrient removal
– Reduced odour and fly problems
– Smaller footprint (10%) than attached growth systems
* Disadvantages
– Susceptible to shock loads and contaminants
– Susceptible to biomass wash-out
– More complex operation
– Susceptible to poor sedimentation (eg ‘bulking’ sludge)
– High energy demand (60% WWT electricity consumption)
94
what is the purification mechanism in suspended growth (2 steps)
Rapid Stage
– due properties of floc
– rapid adsorption+flocculation of soluble & colloidal
– capture of particulate solid matter
– rapid reduction in BOD
* Oxidation Stage
– Respiration at inlet increased as organic matter
oxidised (500 mg O2 g
-1 h
-1
)
– Rapid oxidation of readily degradable organics
– Slower oxidation of recalcitrant components
– Respiration <1/10 initial rate at end of tank
95
in anaerobic digestion what gasses are released
CH4 and CO2 mainly
96
explain the 4 steps of the biochemistry of anaerobic decomposition
Hydrolysis - Large, complex organic molecules (like carbohydrates, proteins, and fats) are broken down into simpler soluble compounds.
Fermentation - The products of hydrolysis are further broken down by acidogenic bacteria into volatile fatty acids (VFAs),
alcohols, lactic acid, H₂, CO₂, and NH₃.
Acetogenesis - VFAs and alcohols from acidogenesis are converted into acetic acid (CH₃COOH), H₂, and CO₂ by acetogenic bacteria.
Methanogenesis- Acetate converted to CH4 by methanogenetic bacteria
97
Name the two most significant greenhouse gases mentioned and their main sources.
CO2 (fossil fuels, land use) & Methane (CH4) (natural gas leaks, agriculture, waste)
98
List 4 major predicted impacts of climate change according to the IPCC.
Sea level rise, more extreme weather (heat/drought/flood), ocean acidification, biodiversity loss. (Any 4 from notes).
99
What is the difference between climate mitigation and adaptation?
Mitigation = Reducing GHG emissions (cause). Adaptation = Adjusting to impacts (effects).
100
What are SSPs (Shared Socioeconomic Pathways)?
Scenarios used by IPCC to model future climate impacts based on different global development paths (population, tech, policy etc.).
101
Define upstream pollution with an example.
Pollution occurring before the final use of a product/energy. E.g., Methane leaks during natural gas extraction, environmental damage from mining battery materials.
102
Explain the difference between stratospheric and ground-level ozone.
Stratospheric: High up, good (filters UV). Ground-level: Low down, bad (pollutant, smog component).
103
Define Embodied Carbon.
Carbon emissions associated with material extraction, manufacturing, transport, construction, maintenance, and disposal of a product/building (lifecycle except use).
104
Define Operational Carbon.
Carbon emissions generated during the actual use of a product/building (e.g., energy for heating, lighting, appliances).
105
What does the Keeling Curve show? What causes the annual fluctuations?
Shows the steady rise in atmospheric CO2 since 1958. Fluctuations caused by seasonal plant growth/photosynthesis in the Northern Hemisphere.
106
What are the two largest GHG emitting sectors in the UK?
Transport and Buildings (Energy Supply/Use).
107
What is the main reason UK's total energy mix is decarbonising slower than its electricity generation?
Heavy reliance on gas for heating and oil for transport, which are harder/slower to decarbonise than electricity supply.
108
What are the three components of the Energy Trilemma?
Sustainability, Security, Equity/Affordability.
109
Explain the Greenhouse Effect in simple terms.
Incoming solar radiation (visible light) passes through atmosphere, warms surface. Surface emits infrared radiation. GHGs in atmosphere absorb some outgoing infrared, trapping heat.
110
What is Climate Forcing (or Radiative Forcing)?
The change in Earth's net energy balance (W/m²) at the top of the atmosphere caused by a specific factor (like GHGs) relative to pre-industrial times.
111
Define Albedo. Give an example of a high and low albedo surface
Surface reflectivity. High: Snow/Ice (~90%). Low: Ocean water (~10-20%).
112
Describe the ice-albedo feedback loop
Warming -> Ice melts -> Darker surface (lower albedo) revealed -> More solar energy absorbed -> More warming -> More ice melts. (Positive/Amplifying feedback).
113
What are the 3 main drivers of large-scale ocean currents (thermohaline circulation)?
Differences in water Temperature, Salinity (both affect density), and Wind (surface drag).
114
What is the Clausius-Clapeyron relationship relevant to rainfall?
Warmer air can hold exponentially more water vapour (~7% more per °C increase). Suggests potential for more intense rainfall events in a warmer climate.
115
Define Capacity Factor (CF). How does it differ from efficiency?
(Actual Energy Generated) / (Max Possible Generation at full capacity). Measures utilization, not conversion effectiveness. Affected by resource availability, downtime etc.
116
What is the Levelized Cost of Energy (LCOE)? What is its main purpose?
Average cost ($/kWh or $/MWh) of generating energy over a power plant's lifetime. Purpose: Compare economic competitiveness of different generation technologies.
117
What are CapEx and OpEx?
CapEx = Capital Expenditure (upfront cost to build). OpEx = Operating Expenditure (ongoing running costs).
118
What has been the major trend in the LCOE of Solar PV and Wind energy over the last 10-15 years? What drove this?
Dramatic decrease, making them highly competitive. Driven by the Learning Rate (tech improvements, scale, manufacturing efficiency).
119
What is 'marginal pricing' in the wholesale electricity market?
The price paid to ALL dispatched generators is set by the bid price of the LAST (most expensive) generator needed to meet demand.
120
Why is energy storage crucial for high penetration of solar and wind power?
To balance supply and demand due to their intermittent nature (store excess when sunny/windy, release when not).
121
State the Ideal Gas Law equation and define the terms (using absolute T and P).
PV=mRT or Pν=RT. P=Absolute Pressure, V=Volume (ν=Specific Vol), m=mass, R=Specific Gas Constant, T=Absolute Temperature (Kelvin).
122
What defines an adiabatic process? What typically happens to temperature during rapid adiabatic compression?
No heat transfer (Q=0). Temperature increases during rapid adiabatic compression.
123
What defines an isothermal process? What is required for it to occur?
Constant temperature (ΔT=0). Requires slow process and heat transfer with surroundings/reservoir.
124
How is boundary work calculated on a P-V diagram? Is it path-dependent?
W = ∫ P dV (Area under the curve). Yes, it is path-dependent.
125
What is the sign convention for Heat (Q) transfer in thermodynamics?
Q > 0 = Heat INTO system. Q < 0 = Heat OUT OF system.
126
State the First Law of Thermodynamics for a closed system process (equation).
ΔE = Q - W (or ΔU = Q - W if KE/PE negligible). Change in internal energy = Heat added minus Work done BY system.
127
What is the main purpose of a power cycle (heat engine)? What is its thermal efficiency definition?
Convert heat (QH) into net work (W_net). η_th = W_net / QH = 1 - QL/QH.
128
What is the main purpose of a refrigeration cycle? What performance metric is used and how is it defined?
Move heat (QL) from a cold space using work input (W_in). Metric: Coefficient of Performance (COP_R) = QL / W_in.
129
What is the main purpose of a heat pump cycle? How does its COP relate to a refrigerator's COP?
Move heat (QH) to a hot space using work input (W_in). Metric: COP_HP = QH / W_in. COP_HP = COP_R + 1.
130
State the Kelvin-Planck statement of the Second Law of Thermodynamics. What does it imply about efficiency?
Impossible for a cycle to take heat from a single reservoir and produce net work. Implies efficiency must be < 100% (must reject heat QL).
131
State the Clausius statement of the Second Law of Thermodynamics. What does it imply about refrigerators/heat pumps?
Impossible for a cycle's sole effect to be transferring heat from cold to hot. Implies refrigerators/heat pumps require work input.
132
What is the Carnot cycle? Why is it important?
An ideal, theoretical cycle consisting of four reversible processes. Important because it defines the maximum possible efficiency/COP between two temperature limits.
133
Write the formula for the Carnot efficiency of a heat engine. What determines the maximum efficiency?
η_Carnot = 1 - (TL / TH) (Temperatures in Kelvin). Determined by the absolute temperatures of the hot (TH) and cold (TL) reservoirs. Larger difference = higher potential efficiency.
134
What is the basic physical principle behind Solar PV cells?
The photovoltaic effect: Incident photons with sufficient energy (above the material's band gap) excite electrons in a semiconductor material, creating an electric current.
135
What is the 'band gap' in a semiconductor, and why is it important for PV?
The minimum energy required to free an electron into a conductive state. Photons below the band gap energy pass through; photons above it create an electron-hole pair, but excess energy is lost as heat. Matching the band gap to the solar spectrum is key for efficiency.
136
What is the typical efficiency range for commercial silicon PV panels? What is the theoretical limit (Shockley-Queisser)?
Commercial: ~20-25%. Theoretical limit (single junction): ~33%. Multi-junction cells can achieve higher efficiencies but are much more expensive.
137
What does 'solar tracking' mean in the context of PV, and what are the types?
Mechanically orienting panels towards the sun to maximize incident radiation. Types: Single-axis (follows sun East-West) and Dual-axis (tracks both altitude and azimuth). Increases energy yield but adds cost/complexity.
138
What materials are commonly used in 'first-generation' PV cells? What are their characteristics?
Crystalline silicon (mono- or poly-crystalline). Moderate efficiency, mature technology, relatively high embedded energy in wafer production.
139
What is the idea behind 'second-generation' (thin-film) PV cells?
Use very thin layers of semiconductor material (e.g., amorphous silicon, CdTe, CIGS). Lower cost, lower material usage, lower embedded energy, but often lower efficiency than crystalline silicon. Can be flexible.
140
What are 'third-generation' (e.g., multi-junction) PV cells designed to achieve?
Overcome the single-junction efficiency limit by stacking materials with different band gaps to capture more of the solar spectrum. Very high efficiency but currently very high cost (used in niche applications like space).
141
List advantages of Solar Photovoltaics (PV).
Zero emissions during operation. Abundant global resource. Rapidly falling costs (often cheapest new electricity). Highly scalable (small rooftop to large utility). Relatively low maintenance. No water needed for operation. Can be integrated into building materials. Fast deployment possible. Silent operation.
142
List disadvantages of Solar Photovoltaics (PV).
Intermittent (daylight/weather dependent). Requires energy storage/backup. Lower capacity factor (~10-25%). Land use for large farms. Efficiency limits. Manufacturing involves energy & potentially rare/hazardous materials. Grid integration challenges (inverters, variability). Performance degrades slightly over time and with high temperatures.
143
What is the fundamental difference between Solar PV and Solar Thermal technologies?
PV converts sunlight directly into electricity. Solar Thermal converts sunlight into heat, which can be used directly (water heating) or indirectly to generate electricity (via turbines in CSP).
144
Describe a typical flat-plate solar thermal collector (e.g., for hot water). What affects its efficiency?
Dark absorber plate with fluid pipes, covered by glass, insulated box. Efficiency affected by: Optical losses (reflection), Thermal losses (convection/radiation from hot plate to surroundings - increases with temperature difference). Higher solar irradiance improves output.
145
What is an 'evacuated tube' solar thermal collector, and why might it be more efficient than a flat plate?
Consists of glass tubes with an inner absorber tube surrounded by a vacuum. The vacuum acts as an excellent insulator, significantly reducing thermal losses, especially at higher temperatures.
146
What is the primary purpose of Concentrating Solar Power (CSP)?
To use mirrors or lenses to concentrate sunlight onto a small receiver, achieving much higher temperatures than flat-plate collectors, enabling efficient electricity generation via conventional heat engines (e.g., steam turbines).
147
Name two main types of CSP technology.
1) Parabolic Troughs/Linear Fresnel: Concentrate sunlight onto a line (tube). 2) Power Towers/Solar Dishes: Concentrate sunlight onto a point (receiver on tower or dish focus).
148
Why is achieving high temperatures advantageous for thermal power generation (link to thermodynamics)?
Higher operating temperature (TH) increases the maximum theoretical (Carnot) efficiency (η = 1 - TL/TH) of the heat engine used to convert heat to electricity. CSP allows higher TH than non-concentrating thermal.
149
What is a key advantage of CSP regarding energy storage?
Can be readily integrated with large-scale, relatively cheap thermal energy storage (TES), typically using molten salts. This allows CSP plants to store heat collected during the day and generate electricity on demand, even after sunset or during cloudy periods (dispatchability).
150
What factors limit the maximum concentration ratio and operating temperature in CSP systems?
Material limits (receiver/fluid must withstand high T), heat losses (especially radiative losses, which scale with T⁴), optical precision limits (cost/accuracy of mirrors/tracking), environmental factors (dust on mirrors).
151
List advantages of Solar Thermal / Concentrating Solar Power (CSP).
Can generate high temperatures for efficient electricity generation or industrial heat. Integrates well with cost-effective thermal energy storage (TES) enabling dispatchability/baseload potential. Uses direct sunlight. Potential for hybridization with fossil fuels. Long operational life possible.
152
List disadvantages of Solar Thermal / Concentrating Solar Power (CSP).
Higher LCOE than PV currently. Requires direct sunlight (performance drops significantly in hazy/cloudy conditions). Mechanically complex (tracking, fluid systems). Often requires significant water consumption (cooling cycle, mirror cleaning). Land intensive. High upfront capital cost. Potential environmental impacts (wildlife).
153
What are the two main configurations of wind turbines based on axis orientation? Which is dominant?
Horizontal Axis Wind Turbines (HAWTs) and Vertical Axis Wind Turbines (VAWTs). HAWTs are overwhelmingly dominant (~99%) for commercial power generation.
154
How does the theoretical power available in the wind relate to wind speed?
Power is proportional to the cube of the wind speed (P ∝ U³). Small increases in wind speed lead to large increases in available power. Also proportional to rotor swept area (A) and air density (ρ). P = ½ ρ A U³.
155
What is the Betz Limit, and what does it represent?
The maximum theoretical efficiency (power coefficient, Cp) for extracting kinetic energy from the wind using a turbine. It's approximately 59.3%. You cannot extract 100% because the air needs some residual velocity to leave the turbine.
156
Why do most large wind turbines have three blades?
It's a compromise between aerodynamic efficiency (more blades capture slightly more power but increase drag/complexity), structural stability/balance (avoids issues of 1 or 2 blades), and cost/aesthetics.
157
What is the 'Tip Speed Ratio' (TSR or λ) of a wind turbine? Why is there an optimal TSR?
Ratio of the speed of the blade tip to the incoming wind speed (λ = ΩR/U). There's an optimal TSR for maximum power extraction; too slow = inefficient capture, too fast = high frictional/aerodynamic losses and potential stall.
158
Explain the basic aerodynamic principle allowing HAWT blades (airfoils) to generate rotational force.
Blades are shaped like airfoils. The combination of incoming wind and blade rotation creates a relative wind velocity hitting the airfoil at an angle of attack. This generates aerodynamic lift (primarily) and drag forces. The lift component in the direction of rotation drives the turbine.
159
What is aerodynamic 'stall' on a wind turbine blade?
Occurs at high angles of attack when the airflow separates from the blade surface, causing a sharp drop in lift and increase in drag, reducing power output. Some turbines use stall regulation for power control at high winds.
160
Why are offshore wind farms becoming increasingly common despite higher costs?
Wind resources are generally stronger and more consistent offshore. Less visual/noise impact on populated areas. Avoids land use conflicts. Allows for larger turbines.
161
What is the 'wake effect' in a wind farm?
Downstream turbines experience lower wind speeds and increased turbulence due to the energy extraction and disruption caused by upstream turbines, reducing their power output and increasing fatigue loads. Farm layout optimisation is crucial.
162
List advantages of Wind Power.
Zero emissions during operation. Mature, cost-competitive technology (esp. onshore LCOE). Abundant resource, widely distributed. Scalable. High capacity factors possible (esp. offshore). Can share land use (onshore). Domestic energy source reducing import reliance.
163
List disadvantages of Wind Power.
Intermittent (wind variability). Requires storage/backup. Visual/noise impacts (onshore). Wildlife impacts (birds/bats). Higher cost/complexity offshore. Grid connection costs. Wake effects reduce farm efficiency. Blade disposal challenges. Optimal sites may be remote.
164
What is the overall goal of Carbon Capture and Storage (CCS)?
To prevent large quantities of CO2, primarily from industrial processes and fossil fuel power generation, from entering the atmosphere by capturing it, transporting it, and storing it securely underground.
165
Name the three main approaches to CO2 capture.
1) Post-combustion: Capture CO2 from flue gases after fuel burning (using solvents/sorbents). 2) Pre-combustion: Convert fuel to H2 and CO2 before combustion, capture CO2, burn H2. 3) Oxy-fuel combustion: Burn fuel in pure O2 (not air) to produce flue gas of mostly CO2 and H2O, easily separated by condensing water.
166
Describe the basic principle of post-combustion capture using chemical absorption (e.g., amines).
Flue gas contacts a liquid solvent (e.g., MEA) in an absorber column; solvent selectively absorbs CO2. CO2-rich solvent is heated in a stripper/regenerator column to release concentrated CO2 (for storage) and regenerate the solvent for reuse.
167
What is the main drawback ('energy penalty') of most CCS processes?
The capture and compression processes require significant energy input (often parasitic load from the host plant, e.g., steam for solvent regeneration), reducing the net energy output and increasing the effective cost per unit of energy delivered.
168
What is chemical adsorption (vs. absorption) capture? What materials are used?
CO2 molecules stick to the surface of a solid sorbent material (e.g., zeolites, Metal-Organic Frameworks - MOFs) rather than dissolving in a liquid. Requires cyclic process (adsorption phase, regeneration phase via pressure or temperature swing - PSA/TSA).
169
Why is CCS considered essential for decarbonizing certain industrial sectors like cement and steel production?
These industries have significant 'process emissions' – CO2 released from chemical reactions (e.g., calcination of limestone in cement) inherent to the process, not just from fuel combustion. CCS is currently the main option to capture these process emissions.
170
What is BECCS and DACS, and why are they important for climate targets?
BECCS: Bioenergy with CCS (burn biomass, capture CO2). DACS: Direct Air Capture with Storage (capture CO2 directly from ambient air). Both are negative emission technologies (NETs), removing existing CO2 from the atmosphere, likely needed to meet ambitious climate targets (e.g., 1.5°C) which may require net removal later this century.
171
What are common methods for transporting captured CO2?
Primarily pipelines (requires CO2 to be compressed to dense phase/supercritical state) or ships (requires liquefaction). Road/rail possible for smaller quantities.
172
Where is captured CO2 typically stored long-term? What makes a good storage site?
Deep geological formations: Depleted oil/gas reservoirs, deep saline aquifers, potentially unmineable coal seams. Requires porous rock layer for storage volume and an impermeable cap rock layer above to prevent leakage. Must be well-characterized geologically.
173
List advantages of Carbon Capture and Storage (CCS).
Allows continued use of fossil fuels with reduced emissions (bridging). Decarbonizes 'hard-to-abate' industrial process emissions. Enables negative emissions (BECCS/DACS). Utilizes some established technologies (e.g., gas processing, pipelines). Can support low-carbon hydrogen production (Blue H2).
174
List disadvantages of Carbon Capture and Storage (CCS).
High cost (capture, transport, storage). Significant energy penalty reduces net plant output. Requires large-scale infrastructure. Long-term storage liability/monitoring. Leakage risk (low but non-zero). Public acceptance issues. Doesn't address other pollutants or upstream impacts. Potential 'moral hazard' delaying fossil fuel phase-out.
175
What is the basic principle of generating electricity from hydropower?
Utilizing the potential energy of water stored at a height (head). Water flows through turbines, converting potential/kinetic energy into rotational mechanical energy, which drives a generator to produce electricity. Power ∝ Flow Rate × Head.
176
Differentiate between 'Run-of-River' and 'Impoundment (Storage)' hydropower dams.
Run-of-River: Minimal water storage; uses natural river flow, often with a small dam (weir) to create head. Output varies with river flow (less dispatchable). Lower environmental impact. Impoundment: Large dam creates a reservoir, storing water. Allows control over water release for dispatchable power generation, flood control, water supply. Larger environmental/social impact.
177
What is Pumped Hydro Storage (PHS)? How does it work and why is it important?
Uses two reservoirs at different elevations. Pumps water uphill to the upper reservoir using cheap/excess electricity (e.g., overnight, high renewables). Releases water downhill through turbines to generate electricity during peak demand/low supply. Currently the dominant form of large-scale, long-duration energy storage globally.
178
Name the three main types of hydro turbines and their typical application ranges (head/flow).
1) Pelton: Impulse turbine; high head, low flow (uses jets hitting buckets). 2) Francis: Reaction turbine; medium head, medium/high flow (most common type). 3) Kaplan: Propeller-type reaction turbine; low head, high flow (adjustable blades).
179
What is the typical efficiency of a large hydro turbine?
Very high, often 85-95%.
180
List major environmental impacts associated with large impoundment dams.
Habitat loss/fragmentation (flooding reservoir area), altered downstream flow regimes, barrier to fish migration, sediment trapping (loss of downstream nutrients/land, reservoir siltation), water quality changes (temperature, dissolved oxygen), potential methane emissions from decaying submerged vegetation.
181
What is 'reservoir sedimentation' and why is it a problem?
Rivers carry sediment which gets trapped behind the dam, gradually filling the reservoir. Reduces water storage capacity (affecting energy output, water supply, flood control) and deprives downstream ecosystems of sediment. Reduces dam lifespan effectiveness.
182
What is tidal energy? Name the two main approaches.
Harnessing energy from the predictable rise and fall of tides. 1) Tidal Range (Barrage): Dam built across an estuary, capturing water at high tide and releasing through turbines at low tide (uses head difference). 2) Tidal Stream: Underwater turbines placed in areas of strong tidal currents (uses kinetic energy, like underwater wind turbines).
183
List advantages of Hydropower.
Mature, reliable, low-cost (existing plants) renewable energy. High efficiency. Dispatchable (storage dams). Pumped hydro provides large-scale storage. Long lifespan. Multi-purpose benefits (flood control, water supply, irrigation). No fuel costs. Low operating emissions.
184
List disadvantages of Hydropower.
High upfront cost & long construction. Major environmental/social impacts (large dams). Geographically limited. Vulnerable to climate change (droughts/floods). Catastrophic failure consequences. Sedimentation reduces lifespan/storage. Disrupts river connectivity. Best sites often developed.
185
What is the fundamental source of geothermal energy?
Heat originating from the Earth's interior (radioactive decay, residual heat from formation). Manifests as a geothermal gradient (temperature increases with depth).
186
Differentiate between high-temperature geothermal and low-temperature geothermal systems.
High-T: Uses hot fluids/steam (>150–200°C) near volcanically active areas to generate electricity. Low-T (GSHP): Uses near-constant shallow ground temperature (~10–15°C) for heating/cooling buildings via heat pumps.
187
What are Enhanced Geothermal Systems (EGS) and how do they work?
Artificial reservoirs created in hot rock with low permeability by injecting high-pressure water to create fractures. Circulating water extracts heat for power or direct use.
188
Explain the principle of a Ground Source Heat Pump (GSHP) for building heating.
A fluid circulates through underground pipes to absorb heat from the ground. The heat pump upgrades this heat for indoor heating. In summer, the process is reversed for cooling.
189
What are closed-loop and open-loop ground source systems?
Closed-loop: Sealed pipes circulate heat fluid underground. Open-loop: Groundwater is pumped through the system then re-injected or discharged.
190
What are energy geo-structures (e.g., thermal piles, tunnel linings)?
Structural elements (like piles or walls) with embedded pipes that act as both support and heat exchangers for buildings or infrastructure.
191
What property determines energy needed to change a material’s temperature? What about heat transfer rate?
Heat Capacity determines energy needed. Thermal Conductivity determines how fast heat is transferred.
192
What is a Thermal Response Test (TRT) and what does it measure?
A field test where heat is injected/extracted from a borehole. Measures the effective thermal conductivity of the ground.
193
List advantages of geothermal energy.
Reliable baseload power, high efficiency, low emissions, small footprint, GSHP usable almost anywhere, potential for direct use, indigenous source.
194
List disadvantages of geothermal energy.
High upfront/drilling costs, limited geographic suitability, EGS risks (seismicity), water contamination, GSHP retrofit disruption, long-term ground temp changes.
195
What is nuclear fission and what is released?
Splitting of heavy nuclei (e.g., U-235), releasing energy, 2–3 neutrons, and radiation.
196
What is a nuclear chain reaction and what condition sustains it?
A self-sustaining fission process. Sustained if reactor is "critical" (k-effective = 1).
197
What is the role of a moderator in thermal reactors?
Slows down fast neutrons to thermal energy. Common moderators: light water, heavy water, graphite.
198
Difference between fissile and fissionable isotopes?
Fissile: Can fission with any neutron (e.g., U-235). Fissionable: Fissions only with fast neutrons (e.g., U-238).
199
Describe the basic layout of a Pressurized Water Reactor (PWR).
Enriched uranium fuel. Light water is both coolant and moderator. High-pressure primary loop transfers heat to secondary steam cycle.
200
What is nuclear fuel enrichment and why is it needed?
Increasing U-235 concentration (~0.7% → ~3–5%) to sustain fission in thermal reactors.
201
What is decay heat and why is it a safety concern?
Residual heat from radioactive decay after shutdown. Must be removed to prevent meltdown.
202
What is High-Level Waste (HLW) and why is it hard to manage?
Spent fuel with long-lived isotopes and high radioactivity. Requires long-term isolation.
203
What is the main goal of Generation IV reactors?
Burn long-lived actinide waste, reduce radiotoxicity, improve fuel use and efficiency.
204
What are Small Modular Reactors (SMRs) and claimed advantages?
<300 MWe reactors. Claimed: faster/cheaper to build, safer, flexible deployment. Real-world performance still under evaluation.
205
List advantages of nuclear power.
Low emissions, reliable baseload, high energy density, secure fuel supply, mature tech, low fuel cost, not weather-dependent.
206
List disadvantages of nuclear power.
High capital costs, long-lived waste, public concerns, potential for accidents, proliferation risk, complex regulation, decommissioning costs.
207
How does hydrogen’s energy density compare to fossil fuels?
High by mass (~3× methane), very low by volume (as a gas at STP).
208
What is the round-trip efficiency of hydrogen for electricity storage?
Electrolysis (~70–80%), losses in storage, fuel cell (~40–60%) → overall ~30–50%.
209
What is the "hydrogen economy" concept?
A future energy system using hydrogen from low-carbon sources across transport, power, industry, and heating.
210
What industries could use low-carbon hydrogen?
Steelmaking, ammonia production, refining, high-temp industrial heat.
211
What are key safety issues with hydrogen?
Wide flammability range, low ignition energy, leaks easily, nearly invisible flame, material embrittlement.
