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 matric 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
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
