1.7 Cellular Respiration Flashcards
What is cellular respiration?
A series of metabolic pathways that brings about the release of energy from a foodstuff and the regeneration of the high-energy compound adenosine triphosphate (ATP)
What ATP composed of ?
Adenosine and 3 inorganic phosphate (Pi) groups
What is stored within a ATP molecule ?
Energy
When is the energy released from an ATP molecule?
When the bond attaching the terminal phosphate is broken
What is the result when the bond attaching the terminal phosphate is broken?
Adenosine diphosphate and inorganic phosphate
What is the energy released for give 5 examples ?
Cellular processes e.g. Muscle contraction
Active transport mitosis/ meiosis (to separate chromosomes)
DNA replication
Protein synthesis
Why is ATP important?
it provides a means by which chemical energy is transferred from one type of reaction to another in a living cell.
Why is there a rapid turnover of ATP molecules?
as cells require a constant supply of ATP molecule
What is happening at the same time as ATP molecules are being broken down?
many are being regenerated from ADP and Pi
What is phosphorylation?
an enzyme-controlled process where a phosphate group is added to a molecule.
Give an example of phosphorylation?
when an inorganic phosphate combines with ADP to form ATP
What are the 3 main stages respiration is divided into?
glycolysis
citric acid cycle
electron transport chain
Where does glycolysis take place ?
cytoplasm of a cell
What is not needed for glycolysis to occur?
oxygen
Describe overall what happens in glycolysis?
a series of enzyme-controlled steps where glucose is broken down into pyruvate
What is glycolysis split into and what are they called?
2 enzyme-controlled phases
energy investment phase
energy pay-off phase
What is USED UP in the energy investment phase?
2 ATP molecules are used up per molecule of glucose
Why are 2 ATP molecules used up?
2 intermediate compounds are phosphorylated (i.e. a phosphate from the breakdown of ATP is added to these compounds)
What does the first of these phosphorylations lead to?
a product that can continue to a number of pathways
What is the second phosphorylation catalysed by?
an enzyme called phosphofructokinase
What kind of reaction is the second phosphorylation and what does the resulting compound only leads to ?
the final stage of the glycolytic pathway
What is produced in the energy pay-off phase?
4 ATP
Apart from 4 ATP being produced during the energy payoff phase what else happens?
dehydrogenase enzymes release hydrogen ions from some of the compounds in this part of the pathway. These hydrogen ions are picked up by a co-enzyme called NAD which in turn becomes NADH
When will the citric acid cycle take place?
if oxygen is present
What happens to the pyruvate in the citric acid cycle?
pyruvate is broken down into carbon dioxide and an acetyl gorup.
What happens to the actetyl group?
acetyl group binds with coenzyme A to enter the citric acid cycle as acetyl CoA
How is citrate formed?
when the acetyl group of acetyl coenzyme A combines with oxaloacetate.
Where does the citric acid cycle take place?
the matrix of the mitochondria
What does the highly folded inner membrane give it?
larger surface area
During citric acid cycle, what do dehydrogenase enzymes do?
remove hydrogen ions and electrons from the respiratory substrate. These are passed to the coenzyme NAD to form NADH or FAD to form FADH2.
What is produced and what is released during citric acid cycle?
ATP is produced
carbon dioxide is released
What does an electron transport chain consist of?
a group of protein molecules
Where are many of the electron transport chains found?
in a cell
Where are electron transport chains found attached to?
the inner membrane of mitochondria called cristae
What do NADH and FADH2 from the glycolytic and citric acid pathways do?
release high-energy electrons and pass them to the electron transport chains
What do electrons begin in?
a high-energy state
What happens to electrons as they flow along a chain of electron acceptors?
they release energy
What is the energy from the electrons used to do?
pump hydrogen ions across the membrane from the inner cavity (matrix) side to the intermembrane space,where a higher concentration of hydrogen ions is maintained
After the hydrogen ions are pumped across to the intermembrane space, what happens to the hydrogen ions?
they move by diffusion and this returns the flow of hydrogen ions to the matrix drives ATP synthase to synthesise ATP from ADP + Pi
When the electrons come to the end of the electron transport chain, what do they combine with?
oxygen, the final electron acceptor, to form water
What does the electron transport chain provide?
Most of the energy (ATP) in cellular respiration
How much ATP is generated in aerobic respiration?
38
How much ATP is generated in glycolysis?
2
How much ATP is generated in the cirtric acid cycle?
2
How much ATP is generated in the electron transport chain?
34
What is the main substrate used in the respiratory pathway?
glucose
What other substrates can be used in the respiratory pathway?
starch glycogen other sugar molecules e..g. lactose amino acids fats
What are starch and glycogen examples of?
complex carbohydrates
What is starch ?
a complex carbohydrate stored by plants
What is glycogen?
a complex carbohydrate stored by animals
What are both starch and glycogen composed of?
chains of glucose molecules
What can starch and glycogen be used in?
respiration as they breakdown into glucose molecules
What are fats broken down into and when?
glycerol and fatty acids when it is required to take part in respiration
What is glycerol and fatty acids converted into?
Glycerol is converted into a glycolytic intermediate and fatty acids are metabolised into smaller fragments that enter the pathway as acetyl coA for use in the citric acid cycle
What are proteins broken down into ?
amino acids by digestive enzymes
What happens to extra amino acids that are not required for protein synthesis ?
they undergo deamination, forming urea and respiratory pathway intermediates
During glycolysis, how can the enzyme phosphofructokinase be inhibited?
by the accumulation of ATP and/or citrate
What is the inhibition of phosphofructokinase by the accumulation of ATP and/or citrate an example of?
feedback inhibition
What does the feedback inhibition of phosphofructokinase help to do?
synchronise and regulate the RATE of glycolysis and the citric acid cycle.
Why is the feedback inhibition of phosphofructokinase important to a cell?
it prevents the needless buildup of intermediate compounds
ATP is only produced when it is required
It conserves resources
What happens to muscle cells during intense exercise?
they start to respire anaerobically because they do not achieve an ADEQUATE supply of oxygen from the bloodstream to support an increased level aerobic respiration.
If there is an inadequate supply of oxygen what can neither the citric acid cycle nor the electron transport chain not do?
generate additional ATP; only glycolysis is able to provide more ATP.
What does glycolysis able to generate?
2NADH and 2ATP from each molecule of glucose as it is broken down to pyruvate
What happens to the pyruvate if there is an inadequate supply of oxygen?
it is converted to lactate and this is accompainied by the transfer of hydrogen from NADH and the regeneration of NAD.
Why must NAD present?
to enable glycolysis to continue and produce more ATP
What does a build up of lactate in muscle cells cause?
fatique and an oxygen debt builds up
What happens when exercise stops?
energy generated by aerobic respiration is now used to convert lactate back to pyruvate
During intense muscular activity, what do muscle cells do?
breakdown ATP to release energy
What do muscle cells contain?
a small store of ATP, which can supply energy for only a few muscle contractions
What is the chemical which provides much of the energy needed for intense muscular activity?
creatine phosphate
What does creatine phosphate do?
breaks down to release energy and phosphate that is used to convert ADP to ATP at a fast rate.
What the creatine phosphate system only support?
strenuous muscle activity for around 10 seconds, when the creatine phosphate supply runs out.
When is the supply of creatine phosphate restored ?
when energy demands are low
Why are skeletal muscle fibres required by the body?
to bring about all kinds of movemenr
What are the 2 types of skeletal muscle fibres?
slow-twitch muscle fibres
fast-twitch muscle fibres
When are slow-twitch muscle fibres most effective and why?
during endurance activities such as long-distance running as they can work for a long time without getting tired
What speed do slow-twitch muscle fibres contract?
slowly
What do slow-twitch muscle fibres depend on?
aerobic respiration to generate most of their ATP
What number of mitochondria do slow-twitch muscle fibres have?
large
When are fast-twitch muscle fibres most effective?
during power events such as weight-lifting
What speed do fast-twitch muscle fibres contract?
quickly
What is the length of time contraction is sustained in a fast-twitch muscle fibre?
short periods of time, but get tired fast, as they consume lots of energy.
What do fast-twitch muscle fibres depend on?
glycolysis to generate ATP
What number of mitochondria do fast-twitch muscle fibres have?
small
What blood capillary density do fast-twitch muscle fibres have?
low
What blood capillary density do slow-twitch muscle have?
high
What concentration of myoglobin do fast-twitch muscle fibres have?
low
What concentration of myoglobin do slow-twitch muscle fibres have?
high
What is myoglobin?
an oxygen-storing protein present in muscle cells
What major storage fuels are used in slow-twitch muscle fibres?
fats
What major storage fuels are used in fast-twitch muscle fibres?
glycogen and creatine phosphate
