Topic 5 - Respiration Flashcards
General info of mitochondria
- ‘powerhouse’ of the cell
- Found in all cell types
- Found in high numbers in cells that have high energy demands
- 1um diameter, 10um long
Draw and label mitochondria
check notes
WHat are the 4 stages of respitation with breif description
1 Glycolysis
a. Splitting 6C glucose into 2x 3C pyruvates
2 Link Reaction
a. Converts 3C pyruvate into CO2 and 2C acetylcoenzyme A
3 Krebs Cycle
a. Acetylcoenzyme A goes through redox reactions that produces ATP and reduced NAD and reduced FAD
4 Oxidative Phosphorylation
a. Uses electrons associated with rNAD and rFAD to synthesise ATP (and waste water)
Where does glycolysis occur?
Cytoplasm of the cell
Where does link reaction occur?
Matrix of the mitochondria
Where does krebs cycle occur?
Matrix of the mitochondria
WHere does oxidative phosphorylation occur?
utilises proteins found in the membrane of the crista
What are the 4 stages of glycolysis?
Stage 1: Activation of glucose by phosphorylation
Stage 2: Splitting of the phosphorylated glucose
Stage 3: Oxidation of triose phosphate
Stage 4: Production of ATP
Describe stage 1 of glycolysis
Before splitting, glucose is made more reactive by adding 2 phosphate molecules (phosphorylation)
Phosphates from the hydrolysis of ATP ADP
This provides the energy to activate glucose and lowers the activation energy needed for the following enzyme controlled reactions
2 ATPs have been ‘spent’
The phosphorylation of glucose is carried out by enzymes called ___________
Hexokinases
Phosphorylation of glucose forms what?
glucose 6-phosphate (G6P)
Extra info for stage 1 of glycolysis
- The reaction uses ATP, but it acts to keep the glucose concentration low, allowing continuous transport of glucose into the cell
- It also blocks glucose from leaking out – the cell lacks transporters for G6P, and free diffusion out of the cell is prevented due to the charged nature of G6P
Describe stage 2 of glycolysis
Glucose 2x 3C triose phosphates (TP)
Describe stage 3 of glycolysis
2 hydrogen removed from each TP
Hydrogen transferred to NAD= (hydrogen carrier)
This forms reduced NAD
What is NAD+
nicotinamide adenine dinucleotide
Describe stage 4 of glycolysis
Enzymes convert 3C TP 3C pyruvate
2 ATPs generated from ADP (net)
Summarise what happens in the link reaction
converts 3c pyruvate into CO2 and 2C acetyl coenzyme A
Where does the link reaction take place? And what happens there?
.Takes place in the mitochondrial matrix
.Oxidises the pyruvate made in glycolysis
.Pyruvate actively transported into matrix of mitochondria
Draw a flow chart of the link reaction
check notes
4 steps of link reaction
- Pyruvate has a hydrogen removed by NAD (NAD is reduced)
- CO2 is removed from pyruvate
- Acetate is formed
- Coenzyme A is added to acetate to form acetyl coenzyme A (2C)
How many times must the link reaction occur for each glucose?
Twice
Krebs cycle, who, when, aka
- Sir Hans Krebs 1937
- AKA Citric acid cycle
Where does krebs cycle take place?
Matrix
How many kreb cycles for each glucose?
2
Draw krebs cycle
check notes
Define Substrate level phosphorylation
the direct phosphorylation of ADP with a phosphate group by using the energy obtained from a coupled reaction
Define oxidative phosphorylation
the production of ATP from oxidised NADH and FADH
So each acetyle CoA enterign the krebs cycle results in what?
1 2CO2 molecules (plus 1 from LR)
2 1 ATP molecule
3 Reduced co-enzymes NAD and Fad
.Coenzymes NADH and FADH are carrying what?
Hydrogen atoms
.During oxidative phosphorylation, some of the energy of the electrons is conserved in the formation of what?
ATP
Where does oxidative phosphorylation occur?
The cristae of the mitochondria
Enzymes and proteins needed for oxidative phosphorylation are found where?
The inner membrane of the mitochondria
Draw a labelled diagram of oxidative phosphorylation
Check notes
Oxygen is important in respiration, why?
it is the final acceptor in oxidative phosphorylation, joining with protons and electrons to form water.
If no oxygen was present in respiration what would happen?
If there was no oxygen present, then there would be nothing to takeaway the protons and electrons, they would block the flow along the ETC and so respiration would stop
Why is the step by step approach in the movement of electrons along the ETC in respiration important?
When a lot of energy is released in one step, a lot is lost as heat (and therefore energy is wasted). If it is released slowly over several steps, more energy is available for the use of the organism. Therefore, NAD and FAD transfer the electrons gradually.
Other substances are also able to undergo oxidation to release energy, what are they?
lipids and proteins
Describe the process of Oxidative Phosphorylation
1 Hydrogen atoms from glycolysis and Krebs join with coenzymes NAD and FAD
2 Reduced NAD and FAD donate the electrons of the hydrogen atoms they are carrying to the first electron transport molecule
3 The electrons pass along the ETC in a series of redox reactions
4 As the electrons pass along the chain they release energy which causes the active transport of protons across the inner mitochondrial membrane into the inter-membranal space
5 The protons gather in the area between the mitochondrial membranes
6 They then diffuse back into the mitochondrial matrix through ATP synthase channels in the inner mitochondrial membrane
7 At the end of the chain the electrons combine with the protons and oxygen making water
8 Oxygen is the final acceptor of the electrons in the ETC
if there was no oxygen availible for respiration, what problems would occur?
Oxygen is the final electron acceptor in aerobic respiration
Without it, NADH no longer releases hydrogen at the ETC
This creates a backlog of NADH, and no NAD being regenerated
Without NAD, the Kreb’s cycle, link reaction, and glycolysis cannot take place
The NADH produced during glycolysis must be oxidised back into NAD+ so that it can be reused
If NAD+ remained as NADH, there would be no carriers to take up the hydrogen atoms released during glycolysis
Glycolysis would stop
In anaerobic respiration conditions, neither Krebs nor the ETC can continue as all the coenzymes are reduced
This means there will be no available NAD+ pr FAD to take up the hydrogen atoms produced
This will cause the enzymes to stop working
As a result the only ATP produced would be the two net produced during glycolysis
How does anaerobic respiration get around the problems of lack of oxygen?
NAD+ is replenished by pyruvate
Pyruvate accepts the hydrogen from NADH
The newly oxidised NAD+ can then be reused in glycolysis
There are two types of anaerobic respiration carried out by eukaryotic cells, what are they?
1 Plants and microorganisms – pyruvate converted to ethanol and CO2
2 Animals – pyruvate converted to lactate
Describe anaerobic respiration for Bacteria and certain fungus (yeast)
1 Pyruvate is decarboxylated (loses CO2) 2 Forms ethanal 3 Ethanal is reduced by H atoms supplied by NADH 4 This forms ethanol Pyruvate + NADH ethanol + CO2 + NAD+
What are the uses of anaerobic respiration in bacteria and certain fungus?
- Yeast and the brewing industry
- Yeast grown anaerobically
- Ferments natural carbohydrates from plant products:
o Grapes (wine)
o Barley seeds (beer)
Why is anaerobic respiration good for animals?
Occurs in animals to overcome a temporary oxygen shortage Survival advantage (immediately after birth, water with low O2, escape)
Where is anaerobic respiration most common in animals?
Skletal muscles
During an oxygen shortage, NADH from glucose can accumulate and must be recovered in animals, how is it gotten rid of?
pyruvate takes up 2 hydrogen atoms from NADH
- This forms lactate
Draw the diagram of pyruvate + NADH –>
Lactate + NAD+
check notes for diagram
When oxygen is availible again, the lactate is oxidised back to what?
Pyruvate
When pyruvate is oxidised from lactate, what can be done to it?
o Further oxidised to release energy
o Converted back to glucose
Problems associated with lactate
- Muscles cramp and fatigue
- Lactate is an acid so causes pH changes that affect enzyme action
- It is removed by the blood and taken to the liver where it is converted into glycogen
D# - This regeneration requires lots of ATP (which is produced in aerobic respiration)
- This regeneration therefore leads to an oxygen debt, where the athlete is continuing an elevated level of oxygen consumption (post exercise oxygen consumption)
