5.7 respiration Flashcards
need for cellular respiration
to drive biological processes and metabolic pathways
for active transport
endocytosis and exocytosis
synthesis of large molecules
DNA replication
cell division
movement etc
anabolic reactions
large molecules are synthesised
catabolic reactions
hydrolysis of large molecules to smaller ones
heterotrophs
consumers and decomposers
obtain energy and molecules from other organisms
autotrophs
trap and use energy to make own molecules
role of ATP
hydrolysed to release energy
structure of a mitochondrion and why its suited
matrix - link reaction and krebs cycle takes place, contains enzymes, NAD/FAD, mitochondrial DNA and ribosomes
outer membrane - contains proteins to allow the passage of molecules into the mitochondria
inner membrane - folds to form cristae which gives a large surface area, electron carriers and ATP synthase enzymes embedded in them
ATP synthase - large and protude from I.M to matrix, protons can pass through
intermembrane space - involved in oxidative phosphorylation and has a short space to allow reduced NAD/FAD to deliver hydrogens to TC
ETC - has cofactors and coenzymes to allow chemiosmosis
name the stages of respiration
glycolysis
link reaction
krebs cycle
oxidative phosphorylation
describe the process of glycolysis
glucose is phosphorylated into hexose bisphosphate
uses hydrolysis of ATP twice
hexose bisphosphate (6C) splits into two triose phosphates (3C)
oxidation of the 2 triose phosphates to 2 pyruvates catalysed by the reduction of NAD and synthesis of 2ATP
products of glycolysis
pyruvate
net gain of 2 ATP
2 molecules of NAD
describe the process of the link reaction
pyruvate is decarboxylated (carboxyl groupis removed) - C02 produced
dehydrogenation occurs and produces an acetyl group - NAD gets reduced
acetyl group combines with coenzyme A to become acetyl coenzyme A (acetyl CoA)
where does the link reaction and kreb cycle occur
mitochondrial matrix
describe the process of (1) the krebs cycle
acetyl group (2C) is released from acetyl CoA
combines with oxaloacetate (4C)
to form citrate
citrate is decarboxylated and dehydrogenated CO2 and reduced NAD is produced
further decarboxylated/dehydrogenated to C02 and reduced NAD is produced
ATP synthesis occurs = 1 ATP
dehydrogenated and produced reduced FAD
dehydrogenated again to regenerate a molecule of oxaloacetate
describe what happens in oxidative phosphorylation
reduced NAD and Fad are reoxidised when they deliver the hydrogen atoms to the ETC
hydrogens split into protons and electrons
protons go into matrix and the electrons are passed along the electron carriers by donating electrons to the next
this releases energy which is used to pump protons across the membrane into the intermembrane space
creates a proton gradient so can now diffuse back into matrix through proton channels associated with ATP synthase enzymes
flow of protons causes change in ATP synthase shape which allows synthesis of ATP (chemiosmosis)
oxygen in the matix accepts electrons from the ETC and and protons (H) forms water
where does oxidative phosphorylation occur
in matrix/ on the cristae
net gain of ATP during each stage
-glycolysis
-link
-krebs
-o.p
- overall
2
0
2
28
32
how much reduced NAD and FAD produced in each stage of respiration for 1 glucose molecule
NAD
glycolysis - 2
LR - 2
Krebs - 6
FAD
Glycolysis - 0
LR - 0
Krebs - 2
how much C02 is produced during each stage of respiration
glycolysis - 0
LR - 2
Krebs - 4
when does anaerobic respiration occur
when no oxygen is present
what happens if oxygen is absent
oxygen cannot act as the final electron acceptor at the end of oxidative phosphorylation
protons diffusing through ATP synthase cannot combine with e- and oxygen = no water
conc. of protons in the matrix increases = reduces proton gradient across membrane
oxidative phosphorylation ceases
reduced FAD and NAD cannot be reoxidised and unload hydrogen atoms
kreb cycle stops
what is used in anaerobic respiration
pyruvate
describe anaerobic respiration in mammals
glycolysis produces pyruvate
pyruvate accepts 2 hydrogens from the reduced NAD (made in glycolysis)
pyruvate is reduced to lactate
reduced NAD is reoxidised
describe anaerobic respiration in yeast
pyruvate is decarboxylated (loses C02) and is converted to ethanal
ethanal accepts 2 hydrogen atoms from reduced NAD and becomes reduced to ethonol
the reduced NAD is reoxidised
what happens to lactate in mammals
carried away in the blood
when oxygen is available then it can be converted to pyruvate or recycled to glucose and glycogen
what would happen if lactate remains in the blood
pH would be lowered and it would inhibit the action of many enzymes
name respiratory substrates
carbohydrates
lipids
protein
what is a respiratory substrate
Molecule broken down / hydrolysed to release energy in respiration
how are carbohydrates used in repsiration
animals can store glycogen
plants store starch
disaccharides can be digested to mono. and into glucose for respiration
how are lipids used in respiration
triglycerides are hydrolysed by lipase to glycerol and fatty acids can be converted into TP
how are fatty acids used with the beta oxidation pathway
fatty acids can be combined with CoA
transported into matrix
broken down into acetyl groups
beta oxidation pathway generates reduced NAD and FAD
acetyl groups are released and enter krebs cycle
how are proteins used as a respiratory substrate
excess amino acids are deaminated
the keto group enters the respiratory pathway
explain which respiratory substrate produces the highest mean energy value and why
lipids
greater availability of of protons for chemiosmosis as lots of hydrogen
more ATP can be produced
what is the respiratory quotient
ratio of C02 produced and 02 consumed
C02 produced/02 consumed
what does the RQ value indicate
greater then 1 = anaerobic respiration taking place as more C02 produced then oxygen consumed
describe what happens to respiration in the absence of oxygen
oxygen cannot act as the final acceptor at the end of oxidative phosphorylation so protons diffusing through channels associated with ATP synthase are not able to combine with e- and o2 to form water
so conc. of protons increase in the matrix
reduces proton gradient = o.p stops
reduced NAD and FAD can’t unload hydrogen atoms and cannot be reoxidised
Krebs cycle stops - and the link reaction
what is the difference between lactate and ethanol fermentation
lactate = mammals
ethanol = yeast/ plants
word equation for both types of anaerobic respiration
glucose -> lactic acid
glucose -> C02 + ethanol
where does anaerobic respiration take place
cytoplasm of cells
describe anaerobic respiration in yeast/ plants
pyruvate is decarboxylated and produces ethanal
ethanal accepts hydrogen atoms from reduced NAD and is reduced to ethanol
(as NAD is reoxidised it can accept more hydrogen atoms from TP so glycolysis can continue)
describe anaerobic respiration in mammals
pyruvate accepts hydrogen atoms from reduced NAD and is reduced to lactate
(reduced NAD is reoxidised and can accept more hydrogen atoms from glycolysis so it can continue to produce ATP to sustain muscle contraction for short periods.)
what happens to lactate once its produced
when more oxygen is prodcued it can convert lactate to pyruvate (enters kreb cycle)
recycled to glucose and glycogen
why does lactate need to be removed from muscle tissues
the pH will be lowered = inhibit action of enzymes involved in glycolysis and muscle contraction
ATP yield from anaerobic respiration
net gain of 2 ATP as the pathways allow glycolysis to continue rather then producing any itself
glucose only partly broken down = yield is about 1/15 of whats produced in aerobic
describe what a respirometer is and how it works
apparatus used to measure the rate of respiration of living organisms
C02 is produced + oxygen absorbs from tube with organisms = volume stays the same
soda lime placed in tube = absorbs C02 produced = volume changes is down to volume of oxygen absorbed by organisms
so pressure in tube reduced and liquid in capillary tube/ manometer moves
measure length of liquid moved and radius = volume of oxygen absorbed
how can you measure the effect of temperature on respiration
using a respirometer
taking readings at different temperatures
why is yeast a faculative anaerobe
can respire aerobically and anaerobically
how can you measure respiration rates in yeast
using a haemocytometer
to count the number of cells produced
