5.7 Respiration Flashcards
what is the equation for aerobic respiration
glucose +water = carbon dioxide +water+energy
define respiration
the release of chemical potential energy from organic molecules
define the two metabolic processes
-catabolic (break down)
-anabolic (build up)
what is ATP
adenosine triphosphate
-it is a phosphorylated nucleotide
-cannot leave the cell where it is made
define hydrolysis
breaking molecules with the addition of water
define condensation
joining molecules resulting in removal of water
what can ATP be hydrolysed to
ADP + Pi
why is some energy released as heat
to keep living organisms warm and provide an optimum temperature for enzyme catalysed reactions
Why is ATP better than direct energy transfer
so cells can obtain the energy they need for a process in small manageable amount that will not cause damage or be wasteful
how much energy is released when ATP is catalysed by ATPases
ATP = ADP 30.5kJmol-1
ADP = AMP 30.5kJmol-1
AMP = adenosine 13.8kJmol-1
Total= 74.8kJmol-1
what is the role of ATP in the cell
-releases energy
-phosphate is removed in hydrolysis
-ADP can attach phosphate during respiration
-energy is released in small quantities to reduce waste
what are the 4 main processes in aerobic respiration
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
define oxidation
loss of electrons/ hydrogen
define reduction
gain of electrons/ hydrogen
what does NAD do in respiration
NAD is a coenzyme. It accepts hydrogen molecules to form NADH (reduced NAD). This hydrogen can be removed and used to generate ATP
what is glycolysis
the first stage of respiration that converts glucose to pyruvate
where does glycolysis occur
in the cytoplasm
what are the 3 main stages of glycolysis
- phosphorylation of glucose to hexose bisphosphate
2.lysis- splitting each hexose bisphosphate molecule into 2 triode phosphate molecules - oxidation of triode phosphate to pyruvate
what are the 2 parts of glycolysis
energy investment phase - phosphorylation
energy pay off phase- oxidation
what is pyruvate
a 3 carbon sugar
Describe the NAD molecule
nicotinamide adenine dinucleotide
has 2 phosphate groups with an oxygen molecule between them.
each phosphate group is attached to ribose.
the bottom ribose is attached to adenine and the top one is attached to nicotinamide
describe the structure of ATP
3 phosphate groups which are joined with phosphoanhydride bonds
ribose which is joined to the phosphate by a phosphodiester bond
adenine which joins the ribose by a glycosidic bond
how does the structure of ATP compare to a nucleotide
-both have pentose sugar (ribose)
-ATP has 3 phosphate, nucleotide has 1
-both can have adenine
describe glycolysis
Glucose has 6 carbons
2 ATP are hydrolysed forming 2 ADP and they donate the phosphate groups to the glucose forming hexose bisphosphate (phosphorylation)
This goes through lysis forming 2x triose phosphate . 2 phosphate groups from the cytoplasm attach to each triose phosphate forming triose bisphosphate. 2 ADP take away the phosphate groups from the triose bisphosphates forming ATP. NAD takes away a hydrogen molecule becoming NADH (reduced NAH) (oxidation) forming pyruvate. 1 glucose molecule produces 2 pyruvate (3 carbon molecule)
what are the products of glycolysis
-2 ATP
-2 NADH
-2 pyruvate
what happens to the pyruvate that is produced during glycolysis
it is transported across the outer and inner mitochondrial membranes via specific pyruvate H+ symport into the fluid filled matrix of the mitochondria
define decarboxylation
removing carboxyl group
define dehydrogenation
removing hydrogen
describe the link reaction
pyruvate (3C molecule) goes through decarboxylation and dehydrogenation with the use of pyruvate dehydrogenase and pyruvate decarboxylase which changes it to an acetyl group (2 carbon molecule). The acetyl group combines with Coenzyme A becoming Acetyl Coenzyme A
describe the Krebs cycle
Acetyl Coenzyme A (2C molecule) reacts with oxaloacetate (4C molecule). Coenzyme A is removed and returns to the link reaction to be reused. 6C molecule is formed called Citrate. Co2 is released and NAD takes 2 hydrogen which forms a 5C compound and NADH. Decarboxylation and dehydrogenation occurs again which forms a 4C compound (oxaloacetate) and NADH. ATP, 2 molecules of reduced NAD, one molecule of FAD and carbon dioxide form in this step.
What are the products of the link reaction per glucose molecule
2 NADH
2 Co2
what are the products of the Krebs cycle per glucose molecule
6 NADH
2 reduced FAD
4 Co2
2 ATP
define chemiosmosis
flow of protons down their conc. gradient across a membrane, through a channel associated with ATP synthase
define oxidative phosphorylation
the formation of ATP using energy released in the electron transport chain and in the presence of oxygen
where does oxidative phosphorylation take place and what does it involve
In mitochondria and it involves electron carrier proteins, arranged in chains called the electron transport chains, embedded in the inner mitochondrial membranes
What happens to NADH and FADH at the electron transport chain
NADH and FADH are deoxidised when they deliver their hydrogen atoms to the electron transport chain.
The hydrogen atoms released from the reduced coenzymes split into protons and electrons and the protons go into solution in the mitochondrial matrix
describe what happens at the electron transport chain
the electrons from the hydrogen atoms pass along the chain of electron carriers. Each electron carrier has an iron ion and they can gain an electron becoming reduced iron. The reduced iron ion can donate the electron to the iron ion in the next electron carrier in the chain, becoming reoxidised. As electrons pass down the chain, some of their energy is used to pump protons across the inner mitochondrial membrane into the intermembrane space.
describe the proton gradient
as protons accumulate in the intermembrane space, a proton gradient forms across the membrane. this gradient generates a chemiosmotic potential (proton motive force) and it is a source of potential energy. ATP is made using the energy of the proton motive force.
describe chemiosmosis
protons cannot diffuse through the lipid bilayer of the mitochondrial membranes . however, they can diffuse through protein channels associated with ATP synthase enzymes that are in the inner membrane. As protons diffuse down their concentration gradient, the flow of protons causes a shape change in the ATP synthase enzyme that allows ADP to combine with Pi, forming ATP. The formation of ATP this way is called oxidative phosphorylation and the final electron acceptor is oxygen.
describe chemiosmosis
protons cannot diffuse through the lipid bilayer of the mitochondrial membranes . however, they can diffuse through protein channels associated with ATP synthase enzymes that are in the inner membrane. As protons diffuse down their concentration gradient, the flow of protons causes a shape change in the ATP synthase enzyme that allows ADP to combine with Pi, forming ATP. The formation of ATP this way is called oxidative phosphorylation and the final electron acceptor is oxygen.
after oxidation phosphorylation, what happens to the electrons?
They are accepted by oxygen. It combines with electrons coming off the electron transport chain and with protons, diffusing down the ATP synthase channel, forming water.
what is the total amount of ATP made during aerobic respiration per glucose molecule
glycolysis- 2
link- 0
krebs- 2
oxidative phosphorylation- 28
total- 32
why is the theoretical yield of ATP rarely achieved
-some ATP is used to actively transport pyruvate into the mitochondria
-some ATP is used in a shuttle system that transported NADH made during glycolysis into mitochondria
-some protons may leak out through the mitochondrial membrane
describe the structure of the mitochondrion
-can be rod shaped, thread like or spherical
-outer membrane is smooth, inner membrane is folded into cristae
-inner membrane contains proteins that transport electrons and protein channels associated with ATP synthase that allow protons to diffuse
what does the mitochondrial matrix contain
contains mitochondrial ribosomes, looped DNA and enzymes for the link reaction and Krebs cycle
molecules of coenzymes NAD and FAD
oxaloacetate
what is the function of oxaloacetate
accepts acetyl group from link reaction
what is the function of mitochondrial DNA
codes for mitochondrial enzymes and proteins
describe the outer membrane of the mitochondrion
contains proteins, some which form channels or carriers that allow passage of molecules such as pyruvate into the mitochondrion
describe the inner membrane of the mitochondrion
-lipid bilayer is less permeable to small ions than outer membrane
-cristae gives large surface area for electron carriers and ATP synthase embedded in it
-electron carriers are protein complexes arranged in electron transport chains
describe the inter membrane space of the mitochondrion
-between inner and outer layers of the mitochondrial envelope
-inner membrane is in close contact with the mitochondrial matrix so molecules of NADH and FADH can easily deliver hydrogens to the electron transport chain
what is substrate level phosphorylation
when ATP is given off at glycolysis and krebs cycle
what happens to respiration when oxygen is absent
oxidative phosphorylation does not occur and link and krebs stop so only glycolysis occurs which produces 2 ATP. But in order for glycolysis to keep running, the NADH must be reoxidised to lose the hydrogen. Fungi and Mammals have two processes to reoxidise the NADH
what are the two metabolic pathways that eukaryotic cells use to reoxidise NADH
Fungi and plants use the ethanol fermentation pathway
Mammals use the lactate fermentation pathway
describe the ethanol fermentation pathway
pyruvate gets catalysed by pyruvate decarboxylase (CO2 is given off) to form ethanal and ethanal gets catalysed by ethanol dehydrogenase (NADH is reoxidised) to form ethanol.
describe the lactate fermentation pathway
pyruvate gets catalysed by lactate dehydrogenase (NADH is reoxidised) and forms lactate
what are the 2 outcomes of the lactate fermentation pathway
-pyruvate is reduced to lactate
-NADH is deoxidised into NAD
where is lactate produced
It is produced in muscle tissue and is carried away from muscles in the blood to the liver
what happens to lactate when more oxygen is available
-lactate converts to pyruvate which may enter the Krebs cycle via link
-lactate can be recycled to glucose and glycogen
what would happen if lactate was not removed from the muscle tissue
the PH would lower and this would inhibit the action of many of the enzymes involved in glycolysis and muscle contraction
How much ATP is released in anaerobic respiration
ethanol and lactate fermentation pathways do not release ATP but they allow glycolysis to continue. Only 1/15 of ATP produced in aerobic respiration is released because glucose is only partly broken down
define respiratory substrate
organic substance which can be oxidised by respiration, releasing energy to make molecules of ATP
How does glucose act as a chief respiratory substrate
it can be stored as glycogen in mammals or starch in plants as it can be hydrolysed to glucose for respiration
how can disaccharides be used for respiration
they can be converted into monosaccharides and can be changed by isomerase enzymes into glucose
(monosaccharides such as fructose and galactose)
how can lipids (fats) be respired
triglycerides can be hydrolysed by lipase to glycerol and fatty acids. Glycerol can then be converted to triose phosphate, enter glycolysis and be respired. The fatty acids are activated by reacting with CoEnzyme A in the cytoplasm. This enters the mitochondrial matrix where it is broken down into 2 carbon acetyl groups each attached to COA. The beta oxidation pathway generates NADH and FADH. The acetyl groups are released from CoA and enter the Krebs cycle by combining with oxaloacetate
Why do we respire glucose first rather than fats
because to respire fats, it takes a lot of energy to break the bonds even though it produces a lot more ATP
which respiratory substrate produces the most energy
lipids (39.4kj)
proteins (17kj)
carbohydrates (15.8kj)
how can proteins be respired
excess amino acids are deaminated in the liver (which removes the amino group). The rest of the amino acid (a keto acid) enters the respiratory pathway as pyruvate, acetyl CoA or as a Krebs cycle acid such as oxaloacetic acid. During fasting/starvation, when glucose or lipids are insufficient, protein from muscles can be hydrolysed to amino acids which are then respired.
how do you work out the respiratory quotient
Co2 produced/ O2 consumed
Using the respiratory quotient, how can you identify if the molecule is a carbohydrate
value is close to 1
Using the respiratory quotient, how can you identify if the molecule is an amino acid
value is around 0.9
Using the respiratory quotient, how can you identify if the molecule is a fatty acid
value is around 0.7
Using the respiratory quotient, how can you identify if anaerobic respiration is taking place
the value is above 1
why will the fluid in a respirometer move towards the living organism doing respiration
as the Co2 will be swapping with O2 as the Co2 would be getting absorbed in the filter paper
