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Flashcards in Respiration Deck (31):

What are coenzymes?

A coenzyme is a molecule that aids the function of an enzyme by transferring a chemical group from one group to another


What are the 4 stages of aerobic respiration?

Links reaction
The Krebs cycle
Oxidative phosphorylation


What is glycolysis?

Glycolysis is a stage of aerobic respiration where the 6 carbon glucose molecule splits into two 3 carbon pyruvate molecules


Glycolysis is split into 2 stages what are they?

Phosphorylation and oxidation


What happens in phosphorylation?

Glucose is phosphorylated by 1 ATP molecule which makes it more reactive so it can be form glucose phosphate ( 6c).As a result the ATP is hydrolysed into ADP and Pi
Glucose phosphate(6c) is phosphorylated again to form hexose biphosphate
The hexose bisphosphate splits imo two molecules of triose phosphate

This process lowers activation energy and phosphorylation makes glucose more reactive so overall 2 ATP used to form tp from glucose


What happens in oxidation?

Triose phosphate is oxidised to pyruvate by removing hydrogen from the two triose phosphate molecules and this is transferred to a hydrogen carrier molecule known as NAD which is reduced to form 2 reduced NAD( one for every triose phosphate)
4 ATP are produced but 2 were used up in
Substrate level phosphorylation so net gain of 2 ATP


What are the overall products of glycolysis? Where do they go? What are they used for?

2 reduced NAD which go to oxidative phosphorylation and used in the formation of ATP
2 pyruvate are actively transported into the mitochondrial matrix for the links reaction
2 net gain of ATP which is used for energy


Where does glycolysis take place?

The cytoplasm


What is anaerobic respiration?

This is respiration when a lack of oxygen is present
The only and final stage is glycolysis in the cytoplasm
This only produces ATP so releases much less energy than aerobic respiration.


What are the the two types of ways anaerobic respiration uses the pyruvate produced in glycolysis ?

Alcoholic fermentation
Lactate fermentation
In both of these pyruvate takes up two hydrogen atoms from the reduced NAD

Reduced nad loses its hydrogen atoms and it’s taken up by pyruvate


What is alcoholic fermentation?

This occurs in plants and yeasts cells . The pyruvate is converted into ethanol and carbon dioxide. The production of ethanol regenerates oxidised NAD so do glycolysis can occur when there’s a lack of oxygen.

Reduced nad


What is lactate fermentation?

Pyruvate is converted into lactate. This reaction uses reduced NAD,oxidising it once more so it’s available for use in glycolysis and can accept further hydrogen


What are examples of alternative respiratory structures?

Lipids and proteins can be used as respiratory substrates


Describe the respiration of lipids?

Lipids are hydrolysed to glycerol and fatty acids .
Glycerol is used to make triose phosphate which enters glycolysis
( glycerol, glycolysis)
Fatty acids contain carbon chains is 2 CARBON FRAGMENTS such as acetyl coenzyme A which is used in the Krebs cycle
Fatty acids contain many hydrogen atoms which can be used to produce ATP in oxidative phosphorylation


Describe the links reaction

Tip: always try link these reactions to redox reactions

This occurs in the mitochondrial matrix and the pyruvate that is actively transported here is decarboxylated( one carbon atom is removed in the form of carbon dioxide and loses 2 hydrogen’s).
At the same time pyruvate is oxidised ( as it loses co2 and H2) to form acetate.
The hydrogen’s accepted by NAD form reduce NAD( these are later used to produce ATP)
The acetate is combined with coenzyme A to form acetyl coenzyme A
No ATP is produced here


How many times does the links reaction happen at what does mean for products of the links reaction?( where do products go and what are they used for?)

Two pyruvate molecules are made for every glucose molecule that enters glycolysis. This means the links reaction( and Krebs cycle) occurs twice for every glucose molecule

2 acetyl coenzyme A is produced which goes to the Krebs cycle
2 carbon dioxide is produced which is released as a waste product
2 reduced NAD which again goes to oxidative phosphorylation


Describe the respiration of proteins

Protein is hydrolysed into its constituent amino acids. These have their amino group( nh2) removed before entering the respiratory pathway at different points depending on
The number of carbon atoms they contain
3 carbons are converted into pyruvATE( atehas 3 letter)
4 and 5 carbons and converted into intermediates in the Krebs cycle ( oxaloacetate)


Describe the Krebs cycle

This occurs in the mitochondrial matrix and is a cycle!
Remember it is split into 3 stages
( total 15) or 654


Describe the first stage of the Krebs cycle ( there are 2 products of this reaction)

The first stage is when the 2 carbon acetyl coenzyme A combines with a 4 carbon molecule( oxaloacetate) to form a six carbon molecule( citrate)
Coenzyme A is released and goes to the link reaction to be used again.


What is the second stage of the Krebs cycle?

The six carbon citrate molecule is converted to a 5 carbon molecule. Decarboxylation occurs where carbon dioxide is removed. Dehydrogenation ( of the 6 carbon molecule) also occurs and the hydrogen is used to produced ONE reduced NAD from NAD.


What is the last stage of the Krebs cycle?

Regeneration of oxaloacetate
The five carbon is converted to a four carbon molecule
Decarboxylation and dehydrogenation of the 5 carbon molecule occur and this produces one molecule of reduced FAD and two of reduced NAD

ATP is also produced from the direct transfer of a phosphate group from an intermediate compound to ADP. This is substrate level phosphorylation


What is the function of coenzyme A?

It transfers acetate between molecules


What are the products of the krebs cycle?( Show the cycle turning twice for each glucose molecule)

2 coenzyme A which is reused in the links reaction
4 carbon compound( oxaloacetate
4 carbon dioxide( 2 instances of decarboxylation)
6 reduced nad( 1 formed second stage 2 third stage) - this goes to oxidative phosphorylation
2 reduced fad( one produced in stage 3) - this goes to oxidative phosphorylation to form ATP


What is the significance of the Krebs cycle?

Regenerates 4 carbon compound that combines with acetyl coenzyme A which would otherwise accumulate
Produced hydrogen atoms that are carried by NAD to electron transport chain and provides energy for oxidative phosphorylation
Leads to production of more ATP

Intermediate compound can manufacture fatty acids, A.A Nd chlorophyll


What is the survival advantage of anaerobic respiration?

Baby mammal in a period shortly after birth or animal living in low oxygen conditions
Strenuous physical activity such as fleeing from a predator


What Is the importance of glycolysis?

It is a universal feature of every living organism and provides indirect evidence for evolution
The enzymes for the glycolytic pathway are found in the cytoplasm of cells


What is the danger in lactate?

Lactate is an acid and it will cause cramps and muscle fatigue if it’s allowed to accumulate in muscle tissue
Lactate is an acid and also caused pH changes which affects enzymes
Needs to be removed by blood and taken into liver to be converted into glycogen


What happens when little oxygen is available ?

The Krebs cycle, links reaction nor electron transport chain( oxidative phosphorylation ) can occur
All FAD and NAD become reduced and no FAD or NAD take up the hydrogen ions produced during the Krebs cycle and enzymes stop working


Where does oxidative phosphorylation take place?

It occurs in the inner mitochondrial membrane which folds to form the Cristae
It is here that the enzymes and electron transport proteins needed to synthesise most of the ATP are found


Describe oxidative phosphorylation briefly

This is the process by which energy carried by electrons, from reduced coenzymes( reduced NAD and reduced FAD is used to make ATP. Oxidative phosphorylation involves the electron transport chain and chemiosmosis


What are the stages of oxidative phosphorylation?

Hydrogen atoms are released from the reduced NAD and reduced FAD as they’re oxidised to NAD and FAD. The hydrogen atoms split into protons and Electron and the fad and nad are recycled

The electrons move down the electron transport chain. They are then passed from one electron transport molecule to the next in a series of redox reactions
Each carrier becomes reduced when it receives an electron, then reverts to its oxidised stage when the electron is passed on.

The electrons lose energy at each carrier as they move down the chain and this energy is used to actively pump protons into the inter membrane space ( the space between the inner and outer mitochondrial membrane)

The concentration of protons is higher in the inter membrane space than in the mitochondrial matrix so this forms a steep electrochemical gradient between here and the matrix of the mitochondria

Protons then move down their electrochemical gradient by diffusion
They go back across the inner mitochondrial membrane and into the mitochondrial matrix , via atp synthase which is embedded In the inner mitochondrial membrane
This movement drives the synthesis of ATP from ADP and inorganic phosphate