Unit 3.1 - Energy And ATP and Unit 3.3 - Respiration released chemical energy in biological processes Flashcards
What is ATP?
A nucleotide
What is ATP known as and why?
The universal energy currency of the cell - is used in all processes requiring energy, in all reactions in all living cells, making it the major energy currency of the cell
How does ATP show the relationship between all living organisms?
There’s no other method for them to transfer energy, it’s in all types of cells and it’s only evolved once in the history of life
Name some uses of ATP in the cell
Protein synthesis
Active transport
Movement of cells (e.g - spermatozoa swimming, contraction of muscle cells)
DNA replication
Why is ATP so important?
Used in all reactions in all cells
4 benefits of ATP
Inert
Soluble
Easily transported
Releases energy efficiently
What are the 3 components of all nucleotides?
Organic base
Pentose sugar
Phosphate groups
What does the structure of ATP consist of?
3 phosphate group
Adenine
Ribose sugar
How is energy released from ATP?
Hydrolysis of the bond between the 2nd and 3rd phosphate groups
What is responsible for the hydrolysis of the bond between the 2nd and 3rd phosphate groups in ATP?
ATPase
How much energy is released when the bond is hydrolysed in ATP?
30.6kJmol-1 of energy
Equation for ATP synthesis
ATP ⇌ ADP + Pi
Why is 30.6kJmol-1 a good amount of energy to be released from ATP?
Little wasted as heat
Usable amount
What’s the name of the process used to reform ATP?
Phosphorylation
Phosphorylation
Phosphate group (Pi) added to ADP by condensation reaction
How is ATP reformed?
Phosphate group (Pi) added to ADP by condensation reaction
Name for ATP to ADP
Dephosphorylation
What happens to energy during dephosphorylation?
Available for cellular work and for chemical synthesis
What type of reaction is dephosphorylation?
Exergonic
What type of reaction is phosphorylation?
Endergonic
Where does the energy required for phosphorylation come from?
Sunlight or food
Is there an ATP store? Why?
No - the ATP cycle is continuous
Where does most ATP synthesis take place?
On the internal membranes of mitochondria and chloroplasts
Do prokaryotes make ATP differently? Why?
Yes - they don’t have mitochondria or chloroplasts
What’ the name of the process of making ATP in mitochondria and chloroplasts?
Chemiosmosis
Why is Chemiosmosis called this?
Osmosis with protons, not water
Which part of mitochondria and chloroplasts is ATP produced in?
Inner membranes
Stages of Chemiosmosis
1.) the enzyme ATP synthetase is part of the stalked particle
2.) this enzyme catalyses the phosphorylation of ADP (the addition of Pi) to form ATP
3.) the enzyme cannot do this without energy. This comes from the flow of protons through the stalked particle’s channel and through ATP synthetase
4.) flow of protons generates an electrochemical gradient, which is a source of potential energy
5.) this drives the phosphorylation of ADP to form ATP (chemical energy)
How does ATPsynthetase obtain its energy to catalyse the phosphorylation of ADP to form ATP?
From the flow of protons through the stalked particle’s channel - generates an electrochemical gradient, a source of potential energy
Why do protons flow through the stalked particle’s channel during Chemiosmosis?
There’s a high concentration of protons in the inter membrane space
The protons diffuse from the intermembrane space to the matrix through the stalked particle
Why is there a concentration gradient for the protons in the intermembrane space in mitochondria?
Protons have been pumped from the matrix to the intermembrane space by transport proteins (proton pumps)
Why can’t protons just flow through the inner membrane without using the channels in the mitochondria?
Protons are polar
Repelled by the non-polar fatty acid tails of the phospholipids that make up the phospholipid bilayer
What are the differences between Chemiosmosis in chloroplasts and mitochondria?
Mitochondria
Protons flow across the inner membrane
From the intermembrane space
To the matrix
Chloroplasts
Protons flow across the thylakoid membrane
From the thylakoid space
To the stoma
Where does the energy come from to maintain the concentration of protons in the intermembrane space/thylakoid space in mitochondria and chloroplasts?
Mitochondria - food
Chloroplasts - light
What do both food and light have to do with the electron transport chain?
Both excite electrons
Where does the energy for proton pumps to pump protons come from?
The flow of electrons in the electron transport chain
What are part of the electron transport chain (in the mitochondria) in the inner membrane?
Stalked particles
x3 proton pumps
Electron carrier proteins
Stages in the electron transport chain
1.) Electron comes from an electron donor - NADH
2.) high energy electron provides energy for proton pumps to pump protons
3.) When NAD loses an electron, it becomes oxidised, whilst the proton pump is reduced (gains an electron) = redox reaction
4.) as the electron is passed from one component to the next in the chain, it causes a series of redox reactions
NADH2 —> NAD+ + 2e- + 2H+
5.) At the end of the process, electrons have to leave the proton pump to make space for the chain to continue, so oxygen accepts the electron
2H+ + 2e- + 1/202 —> H2O
What type of electrons are involved in the electron transport chain?
High energy electrons
Beginning reaction of the electron transport chain
NADH2 —> NAD+ + 2e- + 2H+
End reaction of the electron transport chain
2H+ + 2e-+ 1/2O2 —> H20
Why do we breathe oxygen?
So that cells can use is during oxidative phosphorylation, at the final stage of cellular respiration
Which processes make up oxidative phosphorylation?
The electron transport chain
Chemiosmosis
What happens during transpiration?
High energy bonds in energy rich molecules such as glucose and fatty acids are broken
Energy rich molecules examples
Glucose
Fatty acids
Examples of bonds broken during respiration
C-C
C-H
C-OH
What is the energy released during respiration used for?
To produce ATP
Using which process is ATP produced using the energy released during respiration?
Phosphorylation
(Pi + ADP)
What is respiration catalysed by?
Enzymes
4 stages of respiration
Glycolysis
The link reaction
The Krebs cycle
Oxidative phosphorylation
Where does glycolysis occur?
Cytoplasm
Why does glycolysis not occur in the mitochondria?
Glucose cannot pass through mitochondrial membranes
What type of cells does glycolysis occur in and why?
Both prokaryotic and eukaryotic cells
Can occur under anaerobic and aerobic conditions - no O2 is used
Stages of glycolysis
1.) 2 ATP molecules are needed for the phosphorylation of glucose
2.) forms hexose phosphate
3.) hexose phosphate is unstable - forms 2 molecules of triose phosphate (TP)
4.) each TP molecules loses 2 hydrogen atoms by dehydrogenation
5.) this reduction reaction is catalysed by dehydrogenase
6.) hydrogen atoms released are picked up by NAD to form NADH2 (reduced NAD)
7.) 2 molecules of ATP are also produced by substrate level phosphorylation
8.) pyruvate is formed
Products of glycolysis
Pyruvate
Reduced NAD
2 ATP molecules (net)
What is the net ATP produce of glycolysis? Why
2
2 used, 4 made
What does the reduced NAD produced during glycolysis go on to do?
Donates an electron in the electron transport chain, so more ATP is produced
Where does the link reaction occur?
In the matrix of the mitochondrion
Stages of the link reaction
1.) pyruvate diffuses down its concentration gradient into the mitochondrial matrix
2.) pyruvate is decarboxylated by the enzyme decarboxylase (loses carbon)
3.) releases CO2
4.) pyruvate is also dehydrogenated (loses hydrogen) by the enzyme dehydrogenase
5.) releases 2 hydrogen atoms to form 2C Acetate/acetyl
6.)2C acetate attaches to coenzyme A to form acetyl CoA
7.) hydrogen atoms released are once again picked up by NAD to form reduced NAD
Amount of carbon in all glycolysis stages
6
6
6
3 3
3 3
3 3
Amount of carbon in stages of the link reaction
3
2
2
What does the reduced NAD produced during the link reaction do?
Donates an electron to the electron transport chain
Number of carbons in the stages of the Krebs cycle
4C intermediate + Acetyl coenzyme A (2C)
6C
5C
4C
4C
Name for losing C
Decarboxylation
Name for losing hydrogen
Dehydrogenation
Why is little ATP produced directly during the Krebs cycle?
Most is produced by electron transfer chain through NADH2 and FADH2
Reduced cofactors during Krebs cycle
NADH2
FADH2
How much ATP does NADH2 phosphorylate when transferring an electron?
3
How much ATP does FADH2 phosphorylate when transferring an electron?
2
Stages of the Krebs cycle
1.) Acetyl Coenzyme A (CoA) enters the Krebs cycle, combining with a 4 carbon acid to form a 6 carbon compound, and the CoA is regenerated
2.) the 6 carbon acid is dehydrogeated, making reduced NAD and decarboxylated to make CO2 and a 5 carbon acid
3.) the 5 carbon acid is dehydrogenated, making reduced NAD and FAD and decarboxylated to make CO2 and to regenerate the 4 carbon acid
4.) the 4 carbon acid can come in with more AcCoA and repeat the cycle
Why do we calculate yields of 2 link reactions and 2 Kreb cycles when considering 1 glucose molecule?
Everything is doubled from the glycolysis of 1 glucose molecule
NADH2 produced during glycolysis, the link reaction and Krebs cycle
2, 2, 6
=10
FADH2 produced during glycolysis, the link reaction and Krebs cycle
0, 0, 2
=2
ATP equivalent of 10 NADH2
30
ATP equivalent of 2 FADH2
4
How many ATP are produced using only substrate level phosphorylation during glycolysis, the link reaction and Krebs cycle?
Only 2 ATP
Which is more efficient - aerobic or anaerobic respiration? Why?
Aerobic
More ATP is produced as the electron transport chain is used
What happens to the rest of the available energy from respiration?
Lost as heat
Why are we warm blooded?
The rest of the available energy from respiration is lost as heat
Name 2 other respiratory substrates
Fats
Amino acids
What are fats converted into?
Glycerol
Long-chain fatty acids
Glycerol (from fat) involvement as a respiratory substrate
Converted into 3C triose phosphate, an intermediate in glycolysis
Fatty acids (from fat) involvement as respiratory substrates
Split into 2C acetate fragments, which enter the Krebs cycle as acetyl coenzyme A
What’s the order in which substrates are used for energy?
First - carbohydrates
Fats
Last - amino acids
What would a high protein diet lead to?
An excess of amino acids
What happens to excess amino acids from a high protein diet?
Metabolised in the liver
Deaminated (their amino group is removed and converted into ammonia)
The remaining portion of the molecule is converted into Keto-acid which then enters glycolysis or the Krebs cycle
Urea
Nitrogenous waste in urine
Deaminated amino acids
Amino group is removed and converted into ammonia
What do we always need to remember to do when NAD is reduced in a reaction?
That something was dehydrogenated
(Catalysed by dehydrogenase)
Function of circular DNA in mitochondria
Codes for proteins
Allows mitochondria to replicate
Which substrate is used as a long term energy store in the body and why?
Fats
When it’s broken down, it releases lots of energy as you get multiple Krebs cycles from one fatty acid chain
What’s the remaining part of an amino acid like when the amino group has been removed?
A carbohydrate
Where does Krebs cycle occur?
Matrix of the mitochondria
Where does Krebs cycle occur?
In the matrix of the mitochondria
Where does oxidative phosphorylation occur?
In the inner mitochondrial membrane
Example of animal cells which can respire anaerobically
Muscle cells
What occurs during anaerobic respiration in animal cells?
Lactic acid fermentation
What’s the first stage of both aerobic and anaerobic respiration?
Glycolysis
Lactic acid fermentation
1.) glycolysis converts glucose to pyruvate
2.) reduced NAD transfer the hydrogen to pyruvate to reduce it to lactate
3.) NAD+ feeds back to pick up the hydrogen in glycolysis to be reduced again
What’s lactate also known as?
Lactic acid
Why is lactic acid fermentation not the preferred method of respiration in animal cells?
It produced less ATP
When is lactic acid fermentation used? Give an example
Only in extreme situations (e.g - vigorous exercise)
Why is lactic acid fermentation used during vigorous exercise?
The O2 supply to muscles isn’t sufficient, so cells respire anaerobically for short term ATP production
Is lactic acid fermentation reversible?
Yes, if oxygen becomes available
The amount of oxygen needed to remove the lactic acid built up during lactic acid fermentation
Oxygen debt
What occurs during anaerobic respiration in plants or fungi?
Alcohol fermentation
What does lactic acid fermentation occur in?
Animal cells
What does alcohol fermentation occur in?
Plants or fungi
Alcohol fermentation
1.) glycolysis converts glucose to pyruvate
2.) pyruvate is decarboxylated to ethanal
3.) reduced NAD transfers the hydrogen to ethanal to reduce it to ethanol
4.) NAD+ feeds back to pick up the hydrogen in glycolysis to be reduced again
What is used to produce alcoholic drinks? How come?
Alcohol fermentation
Ethanol = alcohol
CO2 released = carbonated drink
Is alcohol fermentation reversible? Why?
No - the ethanol Is toxic and will eventually kill cells
How many ATP per molecule of glucose are produced under anaerobic conditions?
2
What can the respiratory quotient be used for?
As a way of determining which substrate an organism is using in respiration (e.g - glucose or lipids)
What can we use to determine which substrate an organism is using in respiration?
Respiratory quotient (RQ)
What do we need to know to work out a respiratory quotient?
Number of O2 molecules consumed
Number of CO2 molecules produced
Respiratory quotient (RQ) equation
Number of molecules of CO2 produced
———————————————————
Number of molecules of O2 used
RQ of glucose when used as a substrate in respiration + why
1
Equal volumes of O2 and CO2 are consumed and produced respectively
RQ of lipids when used a substrate in respiration + why
Less than 1
Not equal volumes of O2 and CO2 are consumed and produced respectively - more O2 used than CO2 produced
What generates more energy per unit mass - respiration of lipids or respiration of glucose derived from glycogen in the liver and muscle cells?
Lipids
Glycogen
Stored glucose
In which cels is glucose derived from glycogen?
Liver and muscle cells
What’s the difference between when glucose and lipids are the respiratory substrate during respiration?
Less O2 is consumed and less CO2 is produced when glucose is the respiratory substrate
How is energy stored in the liver?
Glycogen
Why is energy stored as glycogen in the liver as opposed to fat?
Less O2 is consumed and less CO2 is produced when glucose is the respiratory substrate
What’s the benefit of having lipids as a respiratory substrate?
They generate more metabolic water during respiration, which is essential for some desert organisms
Which substrates do cells usually use in respiration?
A combination of both fats and glucose
What is the value of RQ usually between and why?
0.7 and 1
Cells usually respire using a combination of both fats and glucose
(Fats RQ = about 0.7)
(Glucose RQ = 1)
When using the “number of molecules” in the respiratory quotient equation, which numbers are we looking at?
The big ones in front
What’s the difference between NAD and FAD?
NAD -> gives electrons to the first proton pump
FAD -> gives electrons to the second proton pump, so less protons are pumped and so less ATP is produced
What is it that determines whether pyruvate is converted to lactate or CoA?
The oxygen availability
What do we always need to remember to do when talking about respiration?
Say whether it’s aerobic or anaerobic
What happens to energy that’s not converted into ATP?
Released as heat
Which bond is broken when proteins are hydrolysed?
Peptide bond
How is an amino group converted into ammonia and then urea?
By combining with CO2
Where does deamination of amino acids occur?
In the liver
When do we use the chi^2 test and when do we use the students t-test?
Chi^2 : to see whether data is as expected and to compare categorical variables, can use with any type of distribution
t-test : to compare the mean of two given samples (normal distribution only)
