Respiration Flashcards
What is respiration
Releases energy stored in organic molecules such as glucose
-energy then used to synthesis ATP from ADP + inorganic phosphate
What is ATP used for
Hydrolysed to release energy needed to drive biological processes within cells
-Active Transport
-Endocytosis / Exocytosis
- Synthesis of large molecules
-DNA replication
-Cell Divison
Two different types of metabolic reactions in cells
Anabolic - large molecules synthesised from smaller molecules
Catabolic - Involves hydrolysis of large molecules to smaller ones
Why do organisms need to respire
-Thermal energy (heat) helps maintain a stable temperature
-Chemical potential energy in ATP enables living organisms to do work
What does one molecule of ATP consist of
Adenosine, ribose, 3 phosphates
ATP in the solution of cells
Relatively stable but is readily hydrolysed
-While in solution it can be easily moved from place to place within a cell
-Hydrolysed by ATP synthase
How is ATP released
In small manageable amounts so as to not damage the cell or be wasteful
What is ATP referred to
The universal energy currency as it occurs in all living cells and is a source of energy that can be used by cells in small amounts
Amount of energy released from each phosphate hydrolysed from ATP
1- 30.5KJmol-1
2-30.5
3-13.8 (nearest to the ribose)
What is the role of glucose
Adds a phosphate to ADP
Glycolysis
The first stage of respiration; a ten-stage metabolic pathway that converts glucose to pyruvate
-Biochemical pathway that occurs in the cytoplasm
-Uses the co-enzyme NAD
What are the three main stages of glycolysis
1) Phosphorylation of glucose to hexose bisphosphate
2) Splitting each hexose bisphosphate into two triose phosphate molecules
3)Oxidation of triose phosphate to pyruvate
NAD
Nicotinamide adenine dinucleotide
Nonprotein that dehydrogenases enzymes to carry out oxidation
Structure of NAD
Adenine - 6
2 x ribose
2 x phosphate
Oxygen
Nicotinamide
Reduced NAD
-Carries protons and electrons to the cristae of mitochondria
-Delivers them to be used in oxidative phosphorylation for generation of ATP from ADP + Pi
What kind of respiration is glycolysis
Anaerobic
OIL RIG
Oxidation Is Loss
Reduction Is Gain
Glycolysis reaction
Glucose + NAD + 2ADP + 2Pi = 2 Pyruvate + 2NADH + 2ATP
Investment phase
Have to invest 2 ATP molecules to make 4 ATP which gives a net gain of 2 ATP
First stage of Phosphorylation
ATP is hydrolysed to ADP to release a phosphate group which is added to glucose to make hexose monophosphate
-Uses a magnesium co-factor to help the reaction
- One ATP is lost
What enzyme is used in phosphorylation
Hexokinase
Second stage of Phosphorylation
ATP is hydrolysed to ADP to release a phosphate group which is added to glucose to make hexose bisphosphate
-Uses a magnesium co-factor to help the reaction
- One ATP is lost
Hexose Bisphosphate
Sugar with a phosphate at C1 and C6
Splitting the hexose bisphosphate
Each molecule is split in half into three-carbon molecules
-Triose phosphate
-Each has a phosphate group attached
-Think of it as splitting the glucose directly in half
What kind of respiration is oxidation of triose phosphate to pyruvate
Anaerobic as it involves the removal of hydrogen atoms through oxidation
Oxidation of triose phosphate to pyruvate
Dehydrogenase reduces NAD to NADH with a magnesium co-factor
-NAD accept the hydrogen atoms become reduced
-Another phosphate group is added to the triose phosphate- This happens 2X as there are two triose phosphate
Pay off phase
The two phosphate groups on triose phosphate are taken off by phosphoglycerate kinase which then produces 2 ATP molecules
-This happens 2x so 4ATP molecules are made
-This means that there is a net gain of 2ATP due to the investment phase at the start
Products of glycolysis
4 ATP with a net gain of 2 ATP
2X reduced NAD
2 pyruvate
Where do the pyruvate go under aerobic/ anaerobic conditions (absence of oxygen)
Aerobic - Actively transported into the mitochondria for the Link reaction
Anaerobic - converted in the cytoplasm to lactate/ ethanol
-Reduced NAD oxidized so glycolysis can continue to run
What do the mitochondria look like
-Rod shaped
-Thread like
-Diameter 0.5 um
-Length 2-5 um
Structure of mitochondria
-Inner and outer phospholipid membrane making envelope
-Outer membrane smooth ; inner membrane folded into cristae - large SA
-Embedded in inner membrane are proteins that transport electrons + protein channels associated with ATP synthase that allow proteins to diffuse through
- Between inner and outer - intermembrane space
-Mitochondrial matrix, enclosed by inner is semi-rigid and gel like; contains mitochondrial ribosomes; looped mitochondrial DNA ; enzymes for links and Krebs
What does the matrix contain
- Enzymes for Krebs and links
-NAD and FAD
-Oxaloacetate
-Mitochondrial DNA
-Mitochondrial ribosomes
Outer membrane
Fluid Mosaic model
-Allows passages of molecules such as pyruvate into the mitochondrion
Inner membrane
-Lipid bilayer less permeable to small ions such as hydrogen ions (protons)
-Folds (cristae) give large SA for electron carriers and ATP synthase enzymes embedded within
Electron carriers
Protein complexes arranged in electron transport chains
-Involved in the final stage of aerobic respiration
Intermembrane space
Between inner and outer layers of the mitochondrial envelope
-Involved in oxidative phosphorylation
What is a co-factor
A non-protein haem group that contains an iron ion
The electron transport chain - electron carries and cofactors
Each electron carrier has a cofactor
-Iron ion can become oxidised (Fe3+) and reduced (Fe2+) when donating an electron to next electron carrier
-ECP are oxidoreductase enzymes
The electron transport chain - electron carries and coenzymes
Each electron carrier has a co-enzyme
-Using energy from electrons pumps protons from matrix to intermembrane space
-Protons accumulate in IMS and concentration gradient form
What does the proton gradient achieve
Produces a flow of protons through channels in ATP synthase enzymes to produce ATP
The ATP synthase enzymes
Large and protrude from inner membrane into the matrix
-Protons can pass through
What should the outer layer of mitochondrion always be described as
An envelope as it consists of two membranes
How is pyruvate transported to the matrix
A specific pyruvate-H+ symport
-A transport protein that transports two ions/molecules in the same direction
What are the two things that happens to the pyruvate after it has entered the matrix
1) Pyruvate is oxidised from a 3-carbon compound to a 2-carbon compound acetyl CoA, in this process NAD is reduced (Links)
2) The acetyl group is oxidised (Krebs)
The links reaction
1) Pyruvate is decarboxylated and dehydrogenated to produce an acetyl group
2) Acetyl group combines with coenzyme A
3) NAD becomes reduced
Links reaction formula from one glucose molecules
2 pyruvate + 2NAD + 2coA = 2CO2 + 2NADH + 2 CoA
How does the acetyl group get carried to the Krebs cycle
The acetyl group is accepted by CoA and carried to the Krebs cycle
How is energy conserved during the Krebs cycle
By reducing the NAD and FAD
Krebs cycle
1) Acetyl group released from CoA and combines with four-carbon compound oxaloacetate - six-carbon compound formed ( Citrate)
2) Citrate is decarboxylated/hydrogenated = 5 carbon compound + CO2 +NADH
3) 5C decarboxylated/dehydrogenated = 4C + CO2 + NADH
4) 4C combines temp with CoA then released (substrate level phosphorylation) = ATP
5) 4C dehydrogenated = FADH2
6) Atoms rearranged ( enzyme - isomerase) dehydrogenated = oxaloacetate
How many turns of the Krebs cycle is there for each molecule of glucose
2 x
Why do living organisms only have a small amount of oxaloacetate in their cells
As it is recycled and reused in the Krebs cycle
What are the products of the Krebs cycle from one glucose molecules
6 NADH (+2 from Links)
2ATP
2 FADH2
6CO2
What kind of respiration is it in the Krebs cycle/ Links reaction
Aerobic
What other substrates beside glucose can be broken down and respired aerobically
1) Fatty acids = acetate = enter Krebs via CoA
2) Glycerol = Pyruvate = enter Krebs via Links
3) Amino acids = deaminated (NH2 removed) = enter directly/ changed to pyruvate via CoA
Where are the coenzymes FAD and NAD derived from and what can a deficiency in this cause
B vitamins
- A deficiency can affect metabolism
Substrate level phosphorylation
Production of ATP and Pi during glycolysis and Krebs cycle
What is the final stage of respiration
Oxidative phosphorylation
-the formation of ATP using the energy released from the electron transport chain and in the presence of oxygen
What do the folded cristae provide
A large SA for electron carrier proteins and ATP synthase enzymes
What happens in oxidative phosphorylation
1) NADH and FADH reoxidised and deliver H+ to electon transport chain
2) H+ atoms released split into protons and eletrons
3) The protons go in solution into the matrix
Chemical formula of NADH being reduced during oxidative phosphorylation
NADH - oxidised - NAD+ + 2H+ + 2E-
The electron transport chain
1) Electrons released pumped along chain of electron carriers
2) Each electron carrier has a haem group (iron ion) which becomes reduced (Fe2+) when accepts electron and then reoxidised when releases (Fe3+)
3) Called oxido-reductase enzymes
What happens when electrons are pumped from one electron to another
The energy released enables a coenzyme on the electron carriers to pump the protons across the inner membrane into the intermembrane space
-Means each electron has less and less energy
Proton gradient
As protons accumulate in the inner-mitochondrial space it creates a proton gradient as there are more protons in the intermembrane space then in the matrix
What does the proton gradient generate
A chemiosmotic potential = proton motive force (pmf)
-Source of potential energy
-How ATP is made
Chemiosmosis
Flow of protons, down their concentration gradient, across a membrane, through a channel associated with ATP synthase
Why can protons not diffuse straight out of the intermembrane space
The outer membrane has a low degree of permeability to protons and the inner membrane is impermeable to protons
-Has to diffuse out of ATP synthase enzymes that span the membrane
What happens to the ATP synthase as protons diffuse out
It causes the axel to spin - causing a conformational change
-ADP + Pi forced to combine = ATP
- 3ATP produced for each turn
Role of oxygen
Final electron acceptor
- Combines with electrons coming off of the electron transport chain and proteins diffusing down the ATP synthase channel
-This forms Water
Equation surmising the reaction with oxygen
4H+ + 4E- + O2 = 2H20
2H+ + 2e + 1/2 O = H20
How do bacteria use ATP synthase
In reverse to power the movement of the flagella
- Use ATP to produce a proton gradient and the energy associated with the gradient causes a flow of protons that rotates the flagella
How many molecules of ATP are produced per one molecule of glucose
28 ATP
What happens if oxygen is not present
Aerobic respiration discontinues
1) Oxygen cannot act as the final electron acceptor
-Protons cannot combine with electrons and form water
2) Concentration in the matrix increases and reduces the proton gradient across the inner membrane
3)Oxidative phosphorylation ceases
4) NADH AND FADH2 cannot be reoxidised
5) Krebs cycle and link reaction stops
What stage of respiration can continue and what must happen
Glycolysis
-NAD needs to be reoxidised to oxidise the triose phosphate
-Cannot be reoxidised on electron transport chain so another pathway needs to operate
What are the two pathways to reoxidise NAD
Ethanol fermentation pathway (Fungi/plants)
Lactate fermentation pathway (mammals)
Ethanol fermentation pathway
1) Pyruvate - ethanal
-decarboxylated by (pyruvate decarboxylase with co-enzyme thiamine diphosphate)
2)Ethanal - ethanol
-Ethanal reduced and NAD oxidised (ethanol dehydrogenase)
Enzymes involved in the ethanol fermentation pathway
pyruvate decarboxylase with co-enzyme thiamine diphosphate
ethanol dehydrogenase
Yeast is a facultative anaerobe
Live without O2 but if present will respire aerobically
-in anaerobic conditions when accumulation of ethanol reaches 15% it will kill the yeast cells
Equation for the ethanol fermentation pathway
Pyruvate - ethanal - ethanol
When does the lactate fermentation pathway occur in mammals
During vigorous activity i.e. running fast to escape predation
-when the demand for ATP production is high and their is a deficit
The lactate fermentation pathway
1) Pyruvate reduced and NADH oxidised (lactate dehydrogenase)
2) NAD can hydrogen atoms from triose phosphate and glycolysis can continue
Lactate fermentation pathway equation
Pyruvate - lactate
(lactate dehydrogenase) (NADH-NAD)
What happens to the lactate
Transported to the liver and when more oxygen is available lactate may be either:
-Converted to pyruvate and enter Krebs via Links
-Recycled to glucose and glycogen
What would happen if lactate was not removed from the muscle tissue
The pH would be lowered and it would inhibit the action of many enzymes involved in glycolysis and muscle contraction
ATP yield
Glycolysis can continually cycle two ATP molecules
-Glucose is only partly broken down so many more molecules of glucose can undergo glycolysis per minute - overall yield of ATP quite large
-Still only 1/15 compared to aerobic
Fast twitch muscle fibres
Few mitochondria and powered by glycolysis to power their shirt-duration contractions
-Fatigue easily/ pale due to lack of electron carrier transport proteins
-Lack myglobin which stores O2 in some muscles
Slow twitch muscle fibres
Operate aerobically for endurance exercise:
-Dark red contain many mitochondria and are slow to fatigue
Chickens vs ducks/geese
Chickens’ breast meat is pale as they have many fast twitch muscle fibers - only fly occasionally to escape predation
Duck/geese dark - slow twitch muscle fibres as they fly long-distances
Hydrogen acceptor Lactate vs ethanol
pyruvate
ethanal
Co2 - Lactate vs ethanol
no / yes
ATP - Lactate vs ethanol
No
End products Lactate vs ethanol
lactate, NAD
CO2, Ethanol, NAD
Enzymes involved Lactate vs ethanol
Lactate dehydrogenase
Pyruvate decarboxylase, ethanol dehydrogenase
NAD reoxidised - Lactate vs ethanol
yes
Site of pathway
Cytoplasm
Respiratory substrate
An organic substance that can be oxidised by respiration, releasing energy to make molecules of ATP
E.g of respiratory substrates
Carbohydrates, proteins, lipids
-Each have different relative energy values
Carbohydrates
First to be used as easily accessible to hydrolysed
-Stored as glycogen in animals and starch in plants
-Disaccharides can be digested to monosaccharides for respiration
-Monosaccharides (galactose/fructose) can be changed by isomerase enzymes to glucose for respiration
What mammalian cells can only use glucose for respiration
Brain cells/ RBC
Proteins
-Deamination - amino group converted to urea
-If fasting proteins need to be respired
-Enter links/Krebs at different places dependant on amino acid (R group varies number of carbons)
-Slightly more energy than glucose (more NADH per mol)
Fatty acids/ glycerol
Glycerol converted to triose phosphate so it can be respired
-Fatty acids - lots of carbon - lots of ATP produced
Beta oxidation
1) Fatty acid is activated by reacting with Coenzyme A in cytoplasm (energy from ATP - AMP)
2) Enters mitochondrial matrix - broken down into 2 carbon acetyls each attached to coenzymeA
3) Generates NADH AND FADH2
4) Acetyl group released and enters Krebs
Products of krebs
3NADH
FAD
ATP
2CO2
What muscles respire fatty acids
The heart
Mean energy value per gram of the different substrates
Carbohydrates- 15.8 KJg-1
Proteins - 17
Lipid - 39.4
What does a greater proportion of hydrogen atoms in a molecules need
More oxygen to act as the final proton and electron acceptor
How is the respiratory quotient calculated
-How much Co2 produced for O2 consumed
CO2 produced/ O2 consumed
Respiratory quotient for the different substrates
Glucose - 1
Amino acids - 0.9-0.8
Fatty acids - 0.7
What does it mean if the RQ value is greater than one
Some anaerobic respiration is taking place because it shows more CO2 is produced compared to O2 consumed
What does a respirometer measure
The rate of respiration of living organisms by measuring the rate of exchange between CO2 and O2
The principle of the respirometer
If CO2 is absorbed by sodium hydroxide solution/soda lime then the only volume change in the respirometer is due to the volume of oxygen absorbed by the organisms
-If O2 absorbed in tube with organisms then tube has a reduced volume of air exerting less pressure then the greater volume of air in the other tube
-Coloured liquid in the manometer tube rises up twoards the respirometer tube
-If original level of liquid in manometer is marked and the radius of the bore in the capillary tube is known the volume of oxygen absorbed in a specific period can be calculated
How do you reset a respirometer
Syringe is depressed to inject air into the system and reset the liquid in the manometer tube back to its original position
-Allows a reading of the volume of O2 absorbed by noting the change in level of the syringe plunger, as emasured from the graduated scale of the syringe barrel
Why are there glass tubes in the other respirometer
Even out the change in volume of air so the starting amount of air in both capillary tubes are the same
Setting up the respirometer apparatus
1) Add coloured liquid (i.e. methylene blue) with a drop of detergent into the manometer tube
2) Apparatus is connected with the taps open
3) Mass of living organisms found
4) Placed in a water bath for ten mins until apparatus reaches the same temperature as the water bath
5) Syringe plunger should be near the top of the scale of the syringe barrel and its level noted
6) Levels of manometer liquid marked with a felt tip pen
7) Taps are closed and apparatus left in the waterbath for a specific period
8) Change in level of manometer liquid can be measured and the syringe barrel depressed to rest the apparatus - also enables you to measure the volume of O2 absorbed
9) Then calculate the volume ofO2/min/gram
Why must the taps be open on the respirometer and be in the water bath left open for 10mins
So the air in the apparatus can connect with the atmosphere so whilst its reaching the required temperature the organisms respiration is not affecting the fluid in the nanometre
How is a respirometer used with plants
Tubes containing them must be wrapped in foil/black paper to prevent photosynthesis
What should happen between each reading of the organisms breathing rate
Apparatus and organisms should be allowed to adjust to the new temperature
Suitable organisms for the respirometer
Blowfly maggots/ woodlice/ yeast in glucose suspension/ soaked pea seeds
-used over a narrow range of temperatures 10-40
What organisms are used when measuring in extreme temperatures
Fungal material
The effect of substrate concentration on the rate of respiration of yeast
Respirometer may be used with suspensions of yeast and differing concentrations of glucose
-if sodium hydroxide is omitted the evolution of CO2 during a specific time can be measured
What can yeast do in respiration
Produce isomerase enzymes to change some monosaccharides to glucose so glycolysis can take place
-Produce enzymes to hydrolyse disaccarharides
How do you see how efficiently yeast can respire different substrates
Set up fermentation tubes with all conditions the same except the type of sugar being used, and measure the heights of CO2 bubbles over a set period of time
What do you need to remember when drawing ATP
Adenine is not attached by a vertical line
How do you determine the quantity of glass beads in the respirometer
State the method:
1) Find out the difference in mass between the soaked and dry peas
2) The difference in mass represents the volume of glass beads required
3)Calculate the volume of one bead to determine the number of beads equivalent to the volume required
Explain why there is an increased rate of respiration in soaked seeds at 25 °C compared with soaked seeds at 15 °C.
1) Reaction needs to take place in water
2) Enzymes/ substrates can collide in soaked seeds/ limited in dry seeds
3) Soaked = need more ATP
4) For protein synthesis
