Cellular Respiration Flashcards
what is cellular respiration?
Cellular Respiration is the metabolic process that transforms glucose into ATP in order to readily access its energy. It takes place in the cytosol and the mitochondria.
what are the 5 principles of metabolic pathways?
○ Complex transformations occur in a series of separate reactions
○ Each reaction is catalysed by a specific enzyme
○ Many metabolic pathways are similar in all organisms
○ In eukaryotes, metabolic pathways are compartmentalised in specific organelles
○ Key enzymes can be inhibited or activated to alter the rate of the pathway
what are the steps of cellular respiration and where do they occur?
- Glycolysis- cytosol
- Pyruvate Oxidation- mitochondrial matrix
- Citric Acid Cycle- mitochondrial matrix
- Electron Transport Chain- inner mitochondrial membrane
what is the equation for cellular respiration?
C6H1206 + 6O2 –> 6CO2 + 6H2O
what happens in glycolysis?
- 6 carbon sugar (glucose) is converted into fructose-1,6-biphosphate by enzymes such as phosphofructokinase-1 and hexokinase.
- These are then cleaved into 2 3 carbon sugars, from which, glyceraldehyde-3-phosphate is converted into pyruvate.
- Each 3 carbon molecule is converted, therefore producing 2 pyruvate for every glucose molecule.
- Pyruvate is then shuttled across the mitochondrial membrane to undergo pyruvate oxidation.
- 2 ATP used: 4 ATP produced = 2 NET ATP
2NAD+ 4E- +4H+ –> 2NADH +2H+ (NAD+ is reduced) electron acceptor
All 10 steps have a different enzyme catalysing it.
what is the purpose of glycolysis?
The purpose of glycolysis is to convert glucose into pyruvate
what are the two main steps in glycolysis?
Energy investment phase
Energy payoff phase
what happens in the energy investment phase?
- Glucose is converted into fructose-1,6-biphosphate, by phosphofructokinase
- Then cleaved into glyceraldehyde-3-phosphate.
- Uses 2 ATP to do this
what happens in the energy payoff phase?
- glyceraldehyde-3-phosphate (G3P) is converted into pyruvate
- Produces 2 ATP per G3P molecule (therefore 4 overall)
- Converts 2NAD+ to NADH (one for each)
how is glycolysis regulated?
Glycolysis is regulated through the activation or inhibition of phosphofructokinase. It is activated by ADP/AMP and inhibited by ATP
There is lots of ADP when there is no ATP, therefore allowing ATP to be produced by allowing glycolysis to occur
When there is too much ATP/sufficient, then this inhibits the reaction and stops more being made
This is how it is restricted
what is anaerobic respiration?
anaerobic fermentation occurs when there isnt sufficient oxygen for aerobic respiration. It occurs in order to recycle NAD+ from NADH in order to continue transforming glucose into ATP.
describe lactic acid fermentation
Glycolysis produces pyruvate, 2ATP and 2NADH. In order to recycle the NADH to keep producing ATP, pyruvate is converted into lactate in multicellular organisms. Lactate can build up and be a toxin, therefore it is important to break it down
describe alcoholic fermentation
Glycolysis produces pyruvate, 2ATP and 2NADH. In order to recycle the NADH to keep producing ATP, pyruvate is converted into ethanol and carbon dioxide in unicellular organisms + plant cells. Alocohol can build up and be a toxin, therefore it is important to break it down
pyruvate decarboxylase converts pyruvate to acetaldehyde and then it is durther reduced to ethanol by alcohol dehydrogenase
describe pyruvate oxidation- what is it and where does it occur?
occurs in the mitochondrial matrix
- Pyruvate is oxidised to acetate and CO2
- Acetate binds to coenzyme A to form acetyl CoA
- this process is catalysed by pyruvate dehydrogenase
- 2NAD+ to NADH
what is the purpose of pyruvate oxidation?
The purpose is to convert pyruvate into acetyl CoA to be used in the TAC
what is the citric acid cycle?
The purpose is to complete the breakdown of glucose that started in glycolysis.
It oxidises acetyl CoA to CO2
also produces:
1. 8 NADH
2. 2FADH2
3. 2 ATP
other names for the citric acid cycle
TAC cycle
Krebs cycle
describe the citric acid cycle- what are the steps and where does it occur?
8 reactions completely recycles pyruvate into 2 CO2 molecules
- acetyl group and acetyl CoA bind to oxaloacetate
- forms citrate
- undergoes two decarboxylation reactions
- removed carbon atoms as CO2
- gives rise to succinyl coA and GTP
- series of reactions that convert it back into oxaloacetate
- the cycle begins again
GTP can transger its high-energy phosphate to form ATP
what is oxidative phosphorylation?
ATP is synthesised by reoxidation of electron carriers in the presence of O2
has two components:
1. electron transport chain
2. chemiosmosis
describe ETC- GENERALLY
Hydrogen ions and electrons from NADH and FADH2 are passed from one electron carrier to the next and combine with oxygen to make H20
The energy released during electron transport is used to synthesise ATP from ADP and Pi, a process called oxidative phosphorylation
what is FAD/FADH2?
Electron carrying molecule
It is reduced to create FADH2 and oxidised to produce FAD
what is NAD/NADH
Electron carrying molecule
It is reduced to create NADH and oxidised to produce NAD+
what are the three important protein complexed in oxidative phosphorylation?
NADH dehydrogenase
bc1 complex
cytochrome oxidase complex
what are q and c?
q: ubiquinone
c: cytochrome c
they are mobile electron carriers (can move)
they help the transport of electrons
Q also dehydrogenises FADH to FAD
what is the importance of oxygen in the ETC?
It acts as the final electron acceptor in the ETC. If there is no oxygen at cytochrome oxidase complex then electrons will not pass through the ETC, and therefore ATP will not be able to be made through aerobic respiration
how is ATP specifically produced?
inputs and products from one turn of the citric acid cycle
inputs:
Acetyl CoA
3NAD+
FAD
GDP
Pi
2H20
outputs:
HS-CoA
3NADH
3H+
FADH2
GTP
2CO2
what are the intermembrane proteins
- NADH dehydrogenase
gets rid of the hydrogen off of the NADH and carries its electron - bc1 complex
pushes more hydrogen through the membrane into the intermembrane space- electron carrier - cytochrome oxidase complex
oxygen as the final electron receiver
converts hydrogen into oxygen
pyruvate oxidation and the citric acid cycle regulation
They are regulated by the quantities of their starting materials
lots = inhibiter
a little = activated
can also be regulated through the amount of enzymes/through enzyme interference
