Unit 5 - Energy Transfers in & b/w Organisms Flashcards
describe the structure of mitochondria
outer membrane - freely permeable
inner membrane
intermembrane space
matrix
cristae
ATP synthase (stalked particle)
describe the inner membrane
folded into cristae - increases SA for insertion of membrane proteins ATPsynthase & ETC proteins
selectively permeable so most substances can only pass through carrier/channel proteins
stalked particle contains ATP synthase
describe the matrix
inner space
made of semi-rigid material containing enzymes, other proteins, lipids, 70s ribosomes & circular mitochondrial DNA
describe mitochondria characteristics in cells that are more metabolically active?
more mitochondria
larger mitochondria
more densely packed cristae
define cellular respiration
the conversion of organic molecules e.g. glucose (main respiratory substance) into ATP molecules
describe the 2 forms of cellular respiration
aerobic respiration - requires oxygen, produces CO2 + H2O + 38 ATP (lots more than anaerobic respiration)
anaerobic respiration (fermentation) - absence of O2, produces lactic acid/lactate in animals & ethanol + CO2 in plants & yeast
small amount of ATP produced (2 ATP molecules)
what are 2 key principles in respiration & PS?
redox reactions & co-enzymes
describe redox reactions
molecule is oxidised - lost e-s or H atoms
molecule is reduced - gained e-s or H atoms
OILRIG
H atom (1 proton + 1e-)
describe coenzymes
carriers of H atoms (H+ + e-)
molecules that are required by some enzymes to make them function
NAD involved throughout respiration
FAD involved in Krebs cycle
NADP involved in PS
coenzyme-A required to allow Krebs cycle to continue
define aerobic respiration
series of enzyme-catalysed reaction which use coenzymes & make ATP
in presence of O2
what are the 4 stages of aerobic respiration & give brief overview of each?
- glycolysis
in cytoplasm
oxidation of glucose to form 2 pyruvate molecules
occurs in both aerobic & anaerobic respiration - link reaction
in matrix
pyruvate (3C) –> acetyl coenzyme-A (2C) + CO2
aerobic - Krebs cycle
in matrix
acetyl coenzyme A goes into cycle of oxidation-reduction reactions
ATP & e-s produced (e-s reduce NAD & FAD)
aerobic - oxidative phosphorylation (& ETC)
occurs in cristae & intermembrane space
e-s from reduced NAD & reduced FAD from Krebs cycle help to synthesise ATP
H2O is produced as a by-product
aerobic
describe the process of glycolysis
series of enzyme-catalysed reactions in cytoplasm
1. activation of glucose by phosphorylation
glucose is made more reactive by the addition of 2 phosphate molecules, from hydrolysis of 2 ATP, to form glucose phosphate
- phosphorylated glucose is split into 2 triose phosphate (3C) molecules
- oxidation of triose phosphate
2 triose phosphates are oxidised by the removal of hydrogen from each
the hydrogens are transferred to NAD to form reduced NAD (NADH) - production of ATP & pyruvate
enzyme-catalysed reactions convert each triose phosphate into pyruvate (3C)
this makes 2 ATP per pyruvate
this is substrate-level phosphorylation
NB for glycolysis
does not need O2
if no O2, anaerobic respiration takes place after
what are the net products of glycolysis?
2 ATP (4 total but 2 used to phosphorylate glucose at the start)
2 pyruvate
2 reduced NAD (NADH) for ETC later…
what happens b/w glycolysis & the link reaction?
the 2 molecules of pyruvate are actively transported into the mitochondria matrix through carrier molecules in inner membrane, needing ATP
describe the process of the link reaction
occurs in matrix of mitochondria
1. pyruvate is oxidised by removing hydrogen
2. hydrogens are transferred to NAD to form reduced NAD (NADH)
3. CO2 is removed from pyruvate to form a 2C molecule (acetate)
4. 2C molecule (acetate) combines with a molecule of coenzyme-A to form acetyl coenzyme-A
what are the net products of the link reaction?
2 reduced NAD
2 CO2
2 acetyl CoA
no ATP
NB for the link reaction
2 pyruvates produced in glycolysis from 1 glucose
describe the process of the Krebs cycle
occurs in matrix of mitochondria
a series of enzyme-catalysed oxidation-reduction reactions
- 2C acetyl coenzyme-A from the link reaction reacts with 4C molecule to produce a 6C molecule. original CoA is recycled.
- this 6C molecule is decarboxylated & oxidised/dehydrogenated to produce a 4C molecule, 2xCO2 & 2xNADH
- a single ATP molecule is produced by substrate-level phosphorylation
- the 4C molecule transforms into original 4C molecule, which combines with new acetyl CoA to begin the cycle again
2 turns of cycle
what are the net products of the Krebs cycle?
2 ATP
6 NADH
& 2 FADH2 both carrying H atoms to be used in ETC
4CO2
how many turns of Krebs cycle per glucose molecule?
glucose forms 2 pyruvate in glycolysis
–> 2 acetyl CoA in the link reaction
–> 2 turns of Krebs cycle
complete the table to show the differences b/w the Krebs cycle & Calvin cycle for site, e-/H carriers, CO2 & ATP
see booklet
what happens b/w the Krebs cycle & oxidative phosphorylation?
the H atoms removed during glycolysis, the link reaction & the Krebs cycle are carried to the ETC by reduced NAD & reduced FAD
define electron transport chain
the mechanism by which the energy of electrons within H atoms is converted into ATP
describe oxidative phosphorylation
on cristae
1. the reduced NAD & reduced FAD are oxidised as they donate H atoms to carrier molecules attached to the inner mitochondrial membrane. so, the carrier molecules are reduced.
- the H atoms dissociate into protons & electrons
- the e-s are transferred along other carrier molecules in the ETC in a series of redox reactions
- as the e-s pass down the chain, they lose energy, which is used to power 3 proton pumps (in the carrier molecules)
- protons are pumped from the matrix into the intermembrane space where they accumulate
- the protons move back into the matrix bc fac. dif. through proton channels/ATPsynthase down the electrochemical gradient. this potential energy makes the ATPsynthase catalyse the condensation of ADP + Pi to form ATP
- at the end of the ETC, H+ & e- recombine to form H atoms
- O2 is the final electron acceptor in the ETC as the H atoms link with oxygen to form H2O
describe chemiosmosis/chemiosmotic theory
the e-s are transferred along other carrier molecules in the ETC in a series of redox reactions
as the e-s pass down the chain, they lose energy, which is used to power 3 proton pumps (in the carrier molecules)
protons are pumped from the matrix into the intermembrane space where they accumulate
the protons diffuse back into the matrix through proton channels down the electrochemical gradient. this potential energy makes the ATPsynthase catalyse the condensation of ADP + Pi to form ATP
diagram of oxidative phosphorylation
see booklet
why is oxygen needed for aerobic ATP production?
oxygen is the final electron acceptor
electrons cannot be passed along the ETC if there is no oxygen to accept them
if O2 is absent then protons & electrons would back up along the ETC & the process of aerobic respiration stops
decreased ATP produced
NADH & FADH2 cannot donate their H atoms to become oxidised so less NAD & FAD for the rest of respiration
what are alternative respiratory substrates?
lipids & proteins
describe the respiration of lipids
lipids are hydrolysed into fatty acids & glycerol (3C)
fatty acids are broken down into 2C fragments & converted into acetyl CoA –> enters Krebs cycle
glycerol is phosphorylated to convert it to triose phosphate which enters glycolysis pathway
describe the respiration of proteins
proteins are hydrolysed into amino acids
amine group removed
enter respiratory pathway at different point depending upon # of C atoms - 4C/5C enter Krebs cycle, 3C converted into pyruvate & enter the link reaction
what is the respiratory quotient?
the ratio of the volume of CO2 exhaled to that of oxygen consumed by an organism, tissue or cell in a given time
RQ = CO2 produced / O2 used
look at molar ratio in chemical equation
how does cyanide affect the ETC?
respiratory poison
prevents the transfer of e-s from the final e- carrier in the ETC to O2
non-competitive inhibitor that binds to final enzyme in ETC (cytochrome oxidase)
why is the theoretical yield of ATP rarely achieved?
- protons leak across the mitochondrial membrane not through ATP synthase
- ATP produced is used for active transport of pyruvate into matrix (for link reaction)
describe anaerobic respiration
occurs in the absence of O2 so no final e- acceptor in ETC
less ATP formed
ATP only formed by substrate-level phosphorylation
glycolysis then production of lactate or ethanol + CO2
No link reaction, Krebs cycle or ETC
what happens in glycolysis in anaerobic respiration?
pyruvate is reduced to ethanol/lactate
hydrogen is removed from reduced NAD, oxidising it to NAD
pyruvate accepts hydrogen
NAD can be used in further glycolysis, producing ATP
net gain of 2 ATP molecules
what is the equation for the anaerobic respiration/fermentation of plants & yeast?
pyruvate is decarboxylated/reduced
pyruvate + NADH –> ethanol + CO2 + NAD
what are the uses of ethanol & CO2?
ethanol used in brewing w yeast
CO2 used in baking w yeast (makes bread rise)
what is the equation for the anaerobic respiration/fermentation in animals?
pyruvate + NADH –> lactate + NAD
when oxygen is available lactate must be oxidised back to pyruvate
what is the ultimate source of energy for most organisms?
sunlight
apart from for organisms in hydrothermal vents/deep ocean
how is sunlight used?
in light-dependent reaction in photosynthesis to make organic molecules (e.g. glucose for respiration & ATP to make biological molecules for plant biomass
what are the uses of glucose?
in respiration as respiratory substrate to make ATP
make starch & cellulose
to make fats & oils, + N –> nucleic acids & + N –> proteins
describe the groups of organisms
- producers - use light in PS to make organic molecules e.g. glucose
- 1st trophic level (TL) /feeding level - consumers - feed on other organisms
2nd TL - 1y feed on producers (herbivores)
3rd TL - 2y feed on 1y (omnivores/carnivores)
4th TL - 3y feed on 2y (carnivores) - saprobionts = decomposers - release enzymes to break down complex materials in dead organisms into simpler, soluble molecules that can be used & reabsorbed to make other molecules in respiration
bacteria & fungi
define food chain
simple energy flow diagram showing feeding relationship with one organism from each trophic level
e.g.
grass –> grasshopper –> frog
define food web
shows all feeding relationships within an ecosystem
- more realistic & complex than food chain
define trophic level
feeding level/position of organism in food chain
plants = 1st trophic level
define biomass
living mass in an area at a given time
define fresh biomass
includes water content of organism, which varies greatly
so less accurate measure of biomass
define dry biomass
requires killing the organism to dry it to remove water & burn to give a more accurate estimate of biomass
biomass can be measured in terms of mass of carbon or dry mass
how can the chemical energy store in dry biomass be estimated?
with a calorimeter
describe bomb calorimetry
estimates chemical energy store in dry biomass
dry material is weighed & burnt in pure oxygen
the heat of combustion causes the temperature to rise in surrounding water & the temp. change is measured
E released from dry mass = mcΔt
what features of the bomb calorimeter ensure a valid measurement?
insulation of calorimeter/air/glass
reduces heat loss/gain of heat energy to/from surrounding environment
stirrer
distributes heat
water has high specific heat capacity
thermometer
what are the units for the energy of the Sun?
kJm-2year-1
kJ per metre2 per year
Energy, area, time
why is not all of the Sun’s energy absorbed by green plants in photosynthesis?
most is reflected by clouds/dust or absorbed in atmosphere
reflected by waxy cuticle
wrong wavelength so is not absorbed e.g. green
light may pass through the leaves or hit non-photosynthetic parts
another limiting factor is present e.g. temp. or CO2 conc.
what is gross primary production (GPP)?
the total amount of energy fixed by plants in photosynthesis
= chemical energy store in plant biomass in a given area
converted into organic molecules
why is not all of GPP available to other trophic levels?
respiratory losses (R) to produce ATP for active transport of mineral ions into roots
what is net primary production (NPP)?
chemical energy store after respiratory losses to the environment have been considered
available for plant growth & reproduction
biomass available for the next trophic level
what is the formula linking NPP, GPP & R?
NPP = GPP - R
why do primary consumers use only 10% of NPP for growth?
some of the plant is not consumed (roots)
some is lost in faeces via egestion so is not digested & absorbed
some is excreted in urine
some is lost as heat via respiration (for muscle contraction, AT & thermoregulation)
what is the formula for the net production of consumers (N)?
N = I - (F+R)
I - chemical energy of ingested food
F - energy loss in faeces & urine
R - respiratory losses
what % energy is transferred from 1y to 2y consumers & why?
20% bc more energy dense food, more organism is eaten & it is easier to digest
what does the low % energy transfer explain?
why food chains only have 4 or 5 trophic levels
why biomass decreases at each stage
& why available energy decreases at each stage
what is the formula for % energy transfer from one trophic level to the next?
energy available after / energy available before X 100
define primary & secondary productivity
the rate of primary or secondary production, respectively
measured as biomass in a given area in a given time e.g. kJha-1year-1
what is the aim of farming?
to maximise growth, yield & profit by increasing energy conversion efficiency
how is energy conversion made more efficient?
- intensively rearing livestock e.g. factory farming
limiting movement - less ATP needed for muscle contraction so decreased respiratory losses (R)
keep environment warm - less ATP needed for thermoregulation so decreased R
carefully control feeding - optimum type/amount of food for growth (protein) so increased I
exclude predators so no loss to predators - simplifying food webs e.g. monoculture
to eliminate competition for the crop (for water, light & mineral ions) so factors are at max.
to remove pests that consume biomass by using pesticides but decreases biodiversity & expensive
what are the problems with farming?
conflict with conservation
monoculture allows pests/fungal diseases to spread
pollution - eutrophication
describe the carbon cycle (GCSE recap)
see booklet
draw a basic nutrient cycle
see booklet
describe a basic nutrient cycle
nutrients are passed on by consumption & released from an organism as waste or when is dies & is decayed by saprobionts
there is limited availability of nutrients e.g. C, N & phosphorus
they are used many times & stay in the system so a cycle is formed
energy enters the system as sunlight & lost as heat energy via respiration so cannot be recycled but this is not an issue bc of constant energy supply from the Sun
draw the nitrogen cycle & label arrows
see booklet
describe the key points in the nitrogen cycle
plants obtain N in the form of nitrate ions NO3- by active transport from soil
animals obtain N-containing compounds by consuming plants
N is found in AAs, DNA, RNA & ATP - use in Qs
NO3- ions are v soluble so are readily lost from the soil - why N cycling is important
define nitrogen fixation
the process by which nitrogen gas (N2) is converted into nitrogen-containing compounds (ATP, DNA, RNA etc.)
describe the 2 main forms of nitrogen fixation
- free-living N fixing bacteria in soil
N2 gas is reduced to ammonia (NH3) or ammonium ions (NH4+)
NH3/NH4+ used to make AAs
AAs are released when bacteria die - mutualistic N fixing bacteria
live in root nodules of plants (e.g. legumes: beans, peas)
bacteria get carbs from plant & plant gets AAs (N2 fixed into NH3/NH4+ –> make AAs) from bacteria
= mutualistic relationship
how are mutualistic N fixing bacteria used in farming & describe process?
crop rotations to keep soil ‘fertile’
1. grow legumes that have N fixing bacteria to replenish ions
2. grow different crops in field each year as dif. crops use dif. amounts of ions
3. dif. pests & diseases
define ammonification
the production of ammonia or ammonium ions from organic nitrogen-containing compounds e.g. DNA, AAs etc.
by saprobionts
describe ammonification
saprobionts hydrolyse N-containing compounds from faeces & dead organisms, releasing ammonia –> NH3 dissolves in H2O to form NH4+ in soil
= N returned to non-living component of the ecosystem
define nitrification
conversion of ammonium ions to nitrate ions via nitrite ions
NH4+ –> NO2- –> NO3-
describe nitrification
oxidation reaction which releases energy for nitrifying bacteria to drive their chemical reactions
aerobic conditions needed - farmers plough fields to keep soil structure aerated & drain fields to prevent water build-up
describe denitrification
want to avoid!
denitrifying bacteria convert nitrate ions in soil into nitrogen gas (N2) in anaerobic conditions
therefore, it is v important to have oxygen present in soil to increase nitrifying bacteria & decrease denitrifying bacteria
what happens in anaerobic conditions?
decrease N-containing compounds in soil
= decrease yield
= decrease profit
draw phosphorus cycle & label arrows
see booklet
what is the phosphorus cycle needed for?
phospholipids (CSMs), DNA, RNA, ATP - give e.gs in Qs
what is the main reservoir of P?
rock deposits
exists mostly as phosphate ions (PO43-)
what is the main reservoir of C & N?
atmosphere
describe the role of mycorrhizae in nutrient cycles
mycorrhizae (fungi) are extensions on plant roots that increase the surface area for absorption of water by osmosis & mineral ions by active transport even when they are scarce in the soil
how is the relationship b/w plants & mycorrhizae mutualistic?
mycorrhizae benefit bc they receive organic compounds (e.g. carbs/sugars & AAs)
plants benefit bc they can absorb more water & mineral ions due to increased SA of root network
what is the role of fertilisers?
to establish & replenish mineral ions in soil (N, P & K)
to ensure mineral ions are not limiting so plants can grow optimally = max. PD = max. growth = max. yield = max. money
describe how mineral ions are lost from the soil
intensive farming = same area of land repeatedly used so mineral ions are removed by the crop (seeds, leaves & roots) & are not retuned to the soil bc the crop is removed at harvest & not returned to decay by saprobionts
naturally, mineral ions removed by plants are recycled when the plants die & saprobionts break down organic molecules into inorganic molecules
e.g. N-containing compounds (DNA, ATP, AAs etc.) –> ammonium ions –> nitrate ions
animals rarely produce faeces, urea or dead remains in the same area they grazed
what are the 2 types of fertiliser?
natural/organic fertilisers
artificial/inorganic fertilisers
describe natural/organic fertilisers & what are their pros & cons?
dead & decaying remains of plants or animals & animal waste e.g. manure, slurry & bone meal
pros: cheaper, less impact on environment
cons: slower acting & less specific mineral content
describe artificial/inorganic fertilisers & what are their pros & cons?
mined from rocks or created in industry by Haber process
pros: v specific application of ions
cons: big carbon footprint, more expensive, v soluble so big risk of leaching which leads to eutrophication
how do fertilisers help?
N –> AAs, DNA, RNA, ATP
P –> ATP, phospholipids, DNA, RNA
increased nitrate availability = increased AAs & ATP = plants develop earlier w greater leaf SA = increased PS = increased yield
what are the 3 -ve consequences of using fertilisers?
- reducing species diversity
- leaching
- eutrophication
how do fertilisers reduce species diversity?
N-containing fertilisers favour fast-growing species (e.g. grasses) which outcompete slower growing species, which are more successful in low mineral environments
describe leaching of fertilisers
nitrate ions are v soluble to readily dissolve in rainwater & can enter water sources pr become too deep in soil for plants to reach
high nitrate levels in drinking water –>
prevents O2 transport in babies
potentially causes stomach cancer
what are the cause & sources of eutrophication?
caused by leaching of nitrate ions
sources - fertilisers & untreated sewage
describe the process of eutrophication
- nitrates are normally present in low concentrations so limit algal growth in lakes
- leaching causes nitrate conc. to increase so it is no longer a limiting factor so population size of algae increases
- more algae are in the upper waters so they become densely populated = algal bloom
this absorbs light & prevents light reaching deeper water - this lack of light limits plant/algal growth in deeper water so plants die
- saprobiotic bacteria break down dead plants & algae & pop. increases bc availability of dead organisms is not limiting
- saprobionts respire, using up oxygen in water (bc of greater biological oxygen demand)
- fewer plants PS so less O2 released into water so oxygen levels fall & further release of nitrates from saprobionts
- aerobic organisms are limited by low O2 conc. so die, reducing competition with anaerobic organisms
- as well as release of nitrates from decomposition, anaerobic decomposers release toxic waste (e.g. methane greenhouse gas & hydrogen sulfide) which makes water putrid
