12. Respiration Flashcards
Name the full name of ATP and name the groups in it.
Adenosine triphosphate. Adenine, ribose and three phosphate
Write the hydrolysis equation for ATP
ATP + H2O ——> ADP + Pi
Define glycolysis
First part of cellular respiration in which (6-carbon) glucose is broken down anaerobically in the cytoplasm to two molecules of (3 carbon) pyruvate.
Why does the cell store energy as ATP
- ATP cannot pass out of the cell
- ATP is easily hydrolysised
- Stores and relases energy in small amounts
Name the molecules needed in glycolysis
- glucose
- 2 ATP
- 2 NAD (oxidised, hydrogen removed)
Name the molecules produced in glycolysis
- 2 Pyruvate
- 4 ATP
- 2 NADH (reduced, hydrogen added)
Name the stages of glycolysis
- Phosphorylation of glucose.
- Splitting of phosphorylated glucose
- Oxidation of triose phosphate
- The production of ATP
What happens in the phosphorylation of glucose
Glucose is phosphorylated by adding 2 phosphate molecules which come from the hydrolysis of two ATP molecules. This activates the glucose and lowers the activation energy for the enzyme controlled reactions that follow
What happens in the splitting of phosphorylated glucose
The molecule is split up into two 3 carbon sugars, triose phosphate
What happens in the oxidation of triose phosphate
One hydrogen is removed from each TP molecule and is transferred to a hydrogen- carrier molecule known as NAD to form reduced NAD.
What happens in the production of ATP (hydrolysis)
Both triose phosphate are converted into 3 carbon molecules: pyruvate. In this process 2 ATP molecules are produced for 2 ADP for each pyruvate molecule.
What must occur before the krebs cycle
- the two pyruvate molecules produced in glycolysis must be oxidised
- this is done in the link reaction
What occurs in the link reaction
- pyruvate molecules are oxidised to acetate,
- it loses a CO2 molecule and a hydrogen molecule which forms NADH
- it combines with a molecule called Coenzyme A to form acetylcoenzyme A.
Where do link reactions and krebs cycle take place
Inside the mitochondria (matrix)
What is the link reaction equation
pyruvate + NAD+ CoA——> acetylcoenzyme A + NADH + CO2
Name the order of the carbon molecules in the krebs cycle
4 ——> 6 ——> 5 ——> 4 ——>beginning
How many separate steps are there in the krebs cycle
4
Reactions in the krebs cycle
- 4 carbon molecule binds with acetylchoenzyme (ACoA has been fixed) to produce CoA and 6 carbon molecule. (4C + ACoA —> CoA + 6C)
- The 6 carbon molecule loses a CO2 (decarboxylation) and a hydrogen to form a 5 carbon molecule (oxidised) and NADH (reduced) . (6c+ NAD —> 5c +CO2 +NADH).
- The 5 carbon molecule loses a CO2 (decarboxylation) and hydrogen to form a 4 carbon molecule and 2 NADH and FAD. (5c+ 2NAD + FAD —> 4c +CO2 +2NADH +FADH+ ATP). A single ATP molecule is also produced by substrate level phosphitylation.
- 4C molecule can bind with ACoA to start the cycle again
For one glucose molecule how many cycles of krebs are there
Glucose = 2 pyruvate so 2 ACo A so goes round twice.
Where does glycolysis take place
Cytoplasm of all living cells
Glycolysis is the initial stage of which type of respiration
Both aerobic and anaerobic
How is glycolysis indirect evidence for evolution
Glycolysis is a universal feature of every living organism
Does glycolysis require any organelles or membranes to take place
- no
- the enzymes for the glycolytic pathway are found in the cytoplasm
Does glycolysis require oxygen
- no
- therefore it can take place even when oxygen is not present
How do pyruvate molecules produced in the cytoplasm reach the matrix of the mitochondria
- they are actively transported
- through two membranes in the mitochondria
For each molecule of pyruvate, the link reaction and the Krebs cycle produce:
- reduced coenzymes such as NAD and FAD
- one molecule of ATP
- three molecules of CO2
For each original glucose, the link reaction and the Krebs cycle produce:
- reduced coenzymes such as NAD and FAD
- two molecule of ATP
- six molecules of CO2
What is a coenzyme
- not enzymes
- molecules that some enzymes require in order to function
Name 3 types of coenzyme
- NAD (respiration)
- FAD (krebs)
- NADP (photosynthesis)
In what way does the Krebs cycle perform an important role in the cells of organisms
- breaks down macromolecules into smaller ones (pyruvate is broken down into CO2)
- produces hydrogen atoms that are carried by NAD to the electron transfer chain and provide energy for oxidative phosphorylation (leads to the production of ATP which provides energy)
- regenerates the 4 carbon molecule that combines with the acetylcoenzyme A (which would otherwise accumulate)
- it is a source of intermediate compounds used by cells to manufacture other important substances such as fatty acids amino acids and chlorophyll
Where is the site of oxidative phosphorylation
Mitochondria
What is different about mitochondria in metabolically active cells
- there are more
- they have more densely packed cristae which provide a greater SA of membrane incorporating enzymes and other proteins involved in oxidative phosphorylation
Describe the process of oxidative phosphorylation
- electrons enter the electron transfer train by the NADH and FADH donating the electrons of the hydrogen atoms to the first electron transfer carrier molecule in the electron transfer chain.
- the electrons pass along a chain of electron transfer carrier molecules in a series of oxidation-reduction reactions.
- as the electrons flow along the chain the energy released causes active transport of protons across the inner mitochondrial membrane into inter membranal space
- the protons accumulate in the inter-membranal space before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane
- at the end of the chain the electrons combine with these protons and oxygen to form water
- oxygen is the final acceptor of electrons in the electron transfer chain
What donates electrons to the first molecule in the electron transfer chain
NADH and FADH. They donate the electrons of the hydrogen atoms they are carrying
What does the series of oxidation-reduction reactions along the chain of electron transfer cause
It releases energy causing the active transport of protons across the inner mitochondrial membrane and into inter-membranal space
Through what channel do protons travel through when in the inter-membranal space
ATP synthase (via facilitated diffusion)
What is the product of oxidative phosphorylation
ATP and water
What is the importance of oxygen in respiration
- it acts as the final acceptor of the hydrogen ions produced in glycolysis and the Krebs cycle
- without its role of removing the hydrogen atoms the H+ and electrons would ‘back up’
- respiration would come to a halt
Why is it better to release energy in stages
- releasing in a single step causes more energy to be lost of useless heat
- releasing a little at a time more can be harvested for the benefit of the organism
Why is energy from electrons carried by NAD and FAD not transferred in one step
- passed along a series of electron transfer carrier molecules
- so less energy is wasted as heat energy
What do the electrons move down
An energy gradient as each transfer carrier molecule is at a slightly lower energy level. This allows the energy released from the transfer of electrons down this concentration gradient to be released gradually and therefore more usefully
Name two other alternative respiratory substances
- lipids
- protein
What must occurs in the respiration of lipids
- must be first hydrolysed to glycerol and fatty acids
- glycerol is then phosphorylated and converted in triose phosphate which enters the glycolysis pathway which then enters Krebs
- the fatty acid is broken down in 2-carbon fragments which are converted to acetyl coenzyme A which then enters Krebs
What is produced from the oxidation of lipids
- produces 2-carbon fragments of carbohydrate, triose phosphate and many hydrogen atoms
- the hydrogen atoms are used to produce ATP during oxidative phosphorylation
- for this reason lipids release more than double the energy of the same mass of carbohydrate
What must occurs in the respiration of proteins
- hydrolysed to amino acids
- these amino acids have amino group remove before entering the respiratory pathway at different points depending on the no. of carbon atoms they contain
- 3 carbon compounds are converted to pyruvate
- 4 and 5 carbon compounds are converted to intermediates in the Krebs cycle
What processes cannot occur in the absence of oxygen
Krebs cycle and the electron transfer chain as soon all the NAD and FAD would be reduced with no oxygen to accept the final H atom. No NAD or FAD will be available to take up the H+ produced in the Krebs cycle. This denatures enzymes
What must be removed for glycolysis to continue
Its products of pyruvate and hydrogen which is carried by NAD. H must be released from the reduced NAD in order to regenerate NAD. Without this all NAD would be converted to NADH leaving no NAD to take up the hydrogen newly produced from glycolysis, stopping glycolysis
In plants and yeast what is pyruvate converted into
Ethanol and carbon dioxide
In animals what is pyruvate converted into (anarobic)
Lactate
What occurs in anaerobic respiration in plants and yeast
-pyruvate molecule produced in glycolysis loses a CO2 molecule and accepts a H from NADH to produce ethanol
What is the overall equation for anaerobic respiration in plants and yeast
pyruvate + reduced NAD —> ethanol + CO2 + oxidised NAD
What occurs in anaerobic respiration in animals
-each pyruvate molecule produced in glycolysis takes up the two hydrogen atoms from the reduced NAD in glycolysis to form lactate
What is the overall equation for anaerobic respiration in animals
pyruvate + reduced NAD —-> lactate + oxidised NAD
What happens when lactate can be oxidised
- oxidised back into pyruvate
- can then be further oxidised to release energy or converted into glycogen
What happens with a build up of lactate
- cause cramp and muscle fatigue
- lactate is an acid so it lowers pH which effects enzymes
Where is lactate converted into glycogen
It is removed by the blood and taken to the liver to be converted into glycogen
Name two ways energy from cellular respiration is derived
- substrate-level phosphorylation in glycolysis and the Krebs cycle
- oxidative phosphorylation in the electron transfer chain
What is substrate-level phosphorylation
The direct transfer of phosphate from a respiratory intermediate to ADP to produce ATP (glycolysis and Krebs)
What is oxidative phosphorylation
The indirect linking of energy from phosphate to ADP to produce ATP involving energy from the hydrogen atoms that are carried on NADH and FADH (electron transfer chain). Cells produce most of their ATP this way
What is the only process that can occur in anaerobic respiration
Glycolysis as Krebs and electron transfer chain cannot take place as pyruvate is converted into ethanol or lactate
