C1.2: Cell Respiration Flashcards
Describe the structure of ATP.
An RNA Nucleotide made of 3 parts:
- Nitrogenous base Adenine
- Ribose Sugar
- A tail of 3 phosphate molecules
State the name of the process where a phosphate is added to another molecule
Phosphorylation
Outline properties of ATP that make it suitable for the use as an energy currency within cells.
- ATP is soluble in water
- ATP is stable at pH levels close to neutral
- ATP can’t pass freely through phospholipid bilayer: Movement between membrane bound organelles within cells can be controlled
- 3rd Phosphate group of ATP can be easily removed (hydrolysis) and reattached (condensation): Hydrolysing ATP to ADP and phosphate releases a small amount of energy which is not wasted and is sufficient for many processes within the cell
Outline example cellular processes that require use of ATP (3)
- Synthesising macromolecules like DNA
- Pumping molecules or ions via active transport
- Movement of things within the cell such as vesicles
Define Exergonic
Energy is released into surrounding environment
Define Endergonic reaction
Energy is absorbed form surrounding environment
What does ADP stand for
Adenosine Diphosphate
Describe the ATP-ADP cycle, firstly by stating how ATP changes to ADP + Phosphate.
- Hydrolysis reaction occurs with the addition of H2O
- Bond holding 3rd phosphate to 2nd phosphate gets broken and an exergonic reaction occurs, energy is released
- This changes ATP to ADP too
Describe the ATP-ADP cycle, secondly by stating how ADP + Phosphate changes to back to ATP.
- 3rd Phosphate group is added to a molecule of ADP (Phosphorylation occurs)
- A molecule of water is removed in an endergonic reaction and energy is temporarily stored
- Energy stored is released during ATP hydrolysis at the first step which is sufficient for processes within the cell
Where can the energy required to convert ADP and Phosphate back to ATP come from
- Cell respiration: Energy is released by oxidising carbohydrates, fats or proteins
- Photosynthesis: Light energy is converted to chemical energy
- Chemosynthesis: Energy is released by oxidising inorganic substances like sulfides
State why heat is generated during the ATP-ADP cycle.
Exergonic reaction occurs when ATP is hydrolysed into ADP
Define cellular respiration.
Cellular respiration is the gradual and controlled release of energy by breaking down organic compounds to produce ATP
List reasons why cellular respiration must be continuously performed by all cells.
- ATP can’t be stored for later use
- ATP can’t be transferred from cell to cell
- When ATP’s used in cells, heat is released: This heat energy is wasted
Distinguish between cellular respiration and gas exchange (respiration).
- Cellular respiration is a complex series of metabolic pathways and cycles that break down carbon compounds which is used to produce ATP.
- Gas Exchange (respiration) is the movement of oxygen form the inhaled air into the blood and carbon dioxide from the blood into the air to be exhaled.
Define what a respiratory substrate is
Any molecule that can be broken down in respiration to release energy
List common substrates of cellular respiration.
- Glucose
- Carbohydrates
- Lipids
- Proteins (amino acids)
Compare and contrast anaerobic fermentation and aerobic respiration.
Anaerobic Fermentation:
- Occurs in the absence of oxygen
- Occurs only in cytoplasm
- Only glucose and carbs can be used as respiratory substrates
- Yield of ATP is relatively large
- Waste products lactate (lactic acid)
Aerobic Respiration:
- Occurs in the presence of oxygen
- Begins in cytoplasm but most steps occur in mitochondria
- Able to use any respiratory substrates
- Yield of ATP is small
- Waste products are CO2 and H2O
Instrument used to measure rate of respiration and how does it measure the respiration rate
Respirometer: it measures the consumption of O2
Identify the manipulated (independent), responding (dependent) and controlled variation in experiments of variables affecting the rate of cell respiration.
Independent variable:
- Temperature
Dependent variable:
- Rate of cell respiration (volume of oxygen consumed per unit time)
Controlled variables:
- same conc of substrate
- same pH level
- same duration
- same light exposure
List three approaches for determining the rate of cellular respiration.
- Oxygen uptake
- CO2 Production
- Consumption of glucose or other respiratory substrates
Describe three investigative techniques for measuring the effect of a variable on the rate of cellular respiration.
Measure O2 uptake: A capillary tube containing fluid connected to the container to measure changes in the volume of air inside the respirometer
Converting measurements to volumes: Movement of fluid in capillary tube is measured in mm and should be converted to units of volume
Calculating rates: Volume of oxygne used must be divided by time. This rate is the dependent variable in an experiment using a respirometer
Outline oxidation and reduction reactions in terms of movement of hydrogen and electrons.
Oxidation:
- E- are lost
Reduction:
- E- are accepted
Define “electron carrier.”
Substances that are able to accept and lose electrons reversibly
State the name of the electron carrier molecule used in cellular respiration. It is also known as an oxidiser
NAD (Nictotinamide Adenine Dinucleotide)
Outline the formation of reduced NAD (NAD+ + 2H+ + 2e- –> NADH + H+) during glycolysis.
- NAD+ has 1 positive charge
- reduction reaction occurs in respiration by adding 2 H atoms
- Each H atom consists of an electron and a proton
- NAD+ accepts 2 e- and 1 proton from the H atom becoming NADH and the other H+ proton is released
State the formula for the glycolysis reaction.
C6H12O6 + 2 ADP + 2 Pi + 2 NAD+ –> 2 pyruvate + 2 ATP + 2 NADH + 2H+.
In which types of respiration does glycolysis occur?
Glycolysis occurs in both anaerobic and aerobic respiration
State the location of the glycolysis reaction in a cell as well as the conditions
- Cytoplasm of the cell
- It is an anaerobic process
State an example of a metabolic pathway catalyzed by enzymes.
Glycolysis
Outline the glycolysis reaction, including phosphorylation of glucose, lysis, oxidation and ATP formation [PLOA]
- Phosphorylation: Hexose sugar (6C Sugar) gets phosphorylated by 2 ATP to become Hexose Biphosphate (making it unstable)
- Lysis: Hexose Biphosphate (6C sugar) splits into 2 Triose Phosphates (3C sugars).
- Oxidation and Dehydrogenation: in 1 Triose phosphate,
- Oxidation occurs, NAD+ gets reduced to NADH + H+
- The Phosphate group on triose phosphate molecule is used to phosphorylate 1 ADP to 1 ATP
- A pyruvate molecule form
- This is repeated again for the other triose phosphate - ATP Formation: Net gain of 2 ATP, 2NADH+, 2 Pyruvates (3C Sugars)
State the net yield of ATP and reduced NAD produced in glycolysis.
- A net gain of 2 molecules of ATP (4 released)
- 2 molecules of NADH + H+ produced
- 2 Pyruvate molecules
State why NAD must be regenerated in anaerobic respiration.
By restoring stocks of NAD+, the organism can continue to produce ATP via Glycolysis
Compare anaerobic respiration in yeasts and humans.
Humans:
- Pyruvate is converted into lactate
Yeasts:
- Pyruvate is converted into ethanol and CO2
Outline the process of regenerating NAD and production of lactate in humans during anaerobic respiration (Or AKA the process of Lactic Acid Fermentation).
- Pyruvate is converted into lactate by the reduction of the Pyruvate with NADH + H+ using an enzyme
- At the same time, this oxidises the NADH back to NAD (regenerating NAD)
- Therefore allowing NAD to take part in further glycolysis
State the condition in which humans would perform anaerobic respiration.
- When oxygen is short in supply
State an advantage of anaerobic respiration over aerobic respiration in humans
- It is faster
Outline the process of regenerating NAD and production of ethanol in yeast during anaerobic respiration.
- Pyruvate is decarboxylated and a CO2 molecule gets released.
- This converts Pyruvate into Ethanal
- Ethanal is reduced with NADH using an enzyme into Ethanol
- At the same time, this oxides NADH back to NAD (regenerating NAD)
- Therefore, allowing NAD to take part in further glycolysis
Outline how anaerobic respiration in yeast is used in Baking
Baking:
- Yeast is added to dough
- Yeast feeds on sugars in dough and anaerobically respires as it uses up O2 quickly
- CO2 is produced in the dough which creates bubbles causing dough to rise
- Ethanol produced evaporates
Outline how anaerobic respiration in yeast is used in Brewing
Brewing:
- Yeast feeds on sugars from the material being fermented (e.g. grapes for wine)
- Anaerobic conditions are maintained by fermenting in a fermenter (sealed)
- Ethanol produced is the desired product
- CO2 can be used to make some of the products carbonated
Summarize the reactants and products of the link reaction.
Reactants: 2 Pyruvates
Oxidative Decarboxylation occurs: Oxidation when 2NAD+ gets reduced to 2NADH+ and accepts 2e-. 2 Carbon dioxide released as waste
Products:
- 2 Acetyl CoA molecules
- 2CO2 (waste)
- 2NADH + H+
State where the Link Reaction occurs
Mitochondrial Matrix
Outline the link reaction with references to decarboxylation, oxidation and binding of CoA.
Link reaction:
- 1 Pyruvate transported from cytosol to mitochondrial matrix
- Oxidative Decarboxylation occurs: Oxidation when NAD+ gets reduced to NADH+ and accepts an e-. a Carbon dioxide is released as waste
- pyruvate oxidised to acetyl group
- The acetyl group binds to complex carrier molecules called Coenzyme A. Product is 1 Acetyl Coenzyme A
The process is repeated a second time for the second pyruvate molecule
State where the Krebs Cycle occurs
Mitochondrial Matrix
Name 2 carriers that can carry electrons and hydrogen (as they also accept protons)
- FAD
- NAD
Outline the events of the Krebs cycle, referencing the formation of citrate from oxaloacetate, decarboxylation of citrate to reform oxaloacetate, formatting of CO2, formation of ATP and the oxidation reactions that form reduced NAD (=NAD + H+) and reduced FAD (=FADH2).
- 1 Acetyl group (2C Sugar) is consumed by Oxaloacetate (4C Sugar) producing Citrate (6C Sugar). CoA enzyme is released
- Decarboxylation occurs: Oxidation when NAD+ gets reduced to NADH+ and accepts an e-. A Carbon dioxide is released as waste
- Decarboxylation occurs: Oxidation when NAD+ gets reduced to NADH+ and accepts an e-. A Carbon dioxide is released as waste
- ADP converted to ATP
- FAD reduced to FADH2 by oxidising acetyl groups
- H2O is released
- Decarboxylation occurs: Oxidation when NAD+ gets reduced to NADH+ and accepts an e-. A Carbon dioxide is released as waste
- Oxaloacetate forms
The process is repeated a second time for the second pyruvate molecule
The reduced NAD and reduced FAD produced in the Krebs cycle carry electrons to where?
NADH and FADH2 produced in Krebs cycle carry electrons to the Mitochondrial Electron Transport Chain
List the net products of one turn of the Krebs cycle (Using 1 Pyruvate)
- 3 NADH+
- 1 FADH2
- 2 CO2
- 1 ATP
List the net products of the 2 turns of the Krebs cycle (Using 2 Pyruvates)
- 6 NADH+
- 2 FADH2
- 4 CO2
- 2 ATP
State the purpose of the Krebs cycle in Cell Respiration
- To complete the breakdown of Glucose and Produce Reduced NAD (NADH+) and Reduced FAD (FADH2)
Outline the structure and function of the electron transport chain within a mitochondrion.
Structure:
- Series of protein complexes in the cristae (inner membrane) of mitochondria
Function:
- Pumps protons across the membrane using the energy released by the flow of electrons from NADH and FADH2 to generate and maintain a proton gradient across the inner membrane of mitochondria
State what happens to NADH and FADH2 at the Mitochondrial Electron Transport chain
At the ETC,
- NADH and FADH2 are oxidized with the transfer of electrons to electron carrier proteins.
List the reactions that generated the reduced NAD (=NADH + H+) and reduced FAD (=FADH2) used in the electron transport chain.
- NADH+ oxidises to NAD+
- FADH2 oxidises to FAD
/Describe how the movement of electrons through the electron transport chain is used to generate a proton gradient in the intermembrane space.
- FADH2 and NADH get oxidised and the e- get transferred to membrane protein complexes
- E- get transported across the series of membrane protein complexes. The ETC uses energy from e- to move H+ from matrix to the inner mitochondrial membrane space via the protein complexes (as they are moving against their concentration gradient) thus, proton gradient is formed
Define chemiosmosis.
Energy stored in the proton gradient is used to produce ATP
Describe the structure ATP synthase.
ATP Synthase is a large and complex protein that contains 2 main regions:
- One is made of transmembrane subunits embedded into the inner mitochondrial membrane (functions in facilitated diffusion)
- The other is globular and projects into the matrix, it contains active sites (functions as an enzyme)
Define Oxidative Phosphorylation
The energy to synthesise ATP is derived form the oxidation of H+ carriers
Outline the formation of ATP by ATP synthesis, with reference to the movement of protons and phosphorylation of ADP.
- The proton motive force (flow of protons) generates the energy required to phosphorylate ADP using Pi (inorganic phosphate) to form 4 ATP - this is called oxidative phosphorylation
- The oxygen with accepted electrons combines with protons (H+) to maintain a proton gradient thus, forming water
State the formula showing the accepting of electrons by oxygen
1/2 O2 + 2H+ +2e- = H2O
Identify what would happen if toxin cyanide binds to one of the protein complexes in the ETC and prevents it from carrying out its function
Aerobic respiration stops
Compare the total amount of ATP made from anaerobic and aerobic respiration.
Aerobic Respiration: 34 ATP
Anaerobic Respiration: 2 ATP
What molecule is the electron transport chain’s final electron acceptor (terminal electron acceptor)?
Oxygen
Explain why aerobic respiration will stop if oxygen is not present.
H+ carriers can’t transfer energised e- to the chain and ATP production stops
State 2 functions of Oxygen in the ETC
- O2 removes de-energised e- from the chain
- O2 removes the matrix protons to form water
What is formed in the mitochondrial matrix at the end of the ETC and what is it used for?
- Water
- Helps to maintain the proton gradient between the inner mitochondrial membrane space and the matrix.
Compare the use of carbohydrates and lipids as respiratory substrates in aerobic and anaerobic respiration.
- Lipids are unable to be broken down through glycolysis thus, only carbs can be used for anaerobic respiration and in glycolysis
- Lipid molecules are broken down into glycerols and fatty acids - glycerol can be used in glycolysis and fatty acids are broken down into acetyl groups through the Link Reaction and become units of acetyl CoA thus, being able to enter the Krebs cycle and be used in aerobic respiration as they require more O than carbs
Explain the greater energy yield of lipids compared to carbohydrates when used as respiratory substrates.
Carbs:
- Energy is released from a substrate by oxidising C and H and in Carbs more than 50% of the mass is O, which does not yield energy. Therefore, carbs contain less energy per gram than lipids and are used for short-term energy storage
Lipids:
- Nearly 90% of the mass of lipids is C and H from which there is a yield of energy in respiration. Therefore, lipids contain 2x energy per gram than carbs and are used for long-term energy storage
Outline the process by which lipids can be a substrate for respiration.
- Lipid molecules are broken down into glycerols and fatty acids - glycerol can be used in glycolysis and fatty acids are broken down into acetyl groups through the Link Reaction and become units of acetyl CoA thus, being able to enter the Krebs cycle and be used in aerobic respiration as they require more O than carbs
What is a key component required for the synthesis of Acetyl CoA in the Link Reaction
- Pyruvic Acid
State the purpose of converting pyruvate to lactate during anaerobic cell respiration
- To regenerate NAD
Outline the energy changes involved in the interconversion between ATP and ADP
- Energy released when ATP is hydrolysed to ADP + Phosphate
- Energy is required to synthesise ATP from ADP + Phosphate
What is the role of ATP in cellular processes
- ATP is a short-term energy storage molecule
What distinguishes peptide hormones from steroid hormones
- Peptide hormones act through secondary messengers (cAMP)
Outline the roles of oxidation reactions in oxidative phosphorylation.
- NADH+ oxidises to NAD+ and loses electrons to NAD+ in the electron transport chain
- NADH+ disassociates from Hydrogen
Explain what would happen to the cell if cellular respiration was an uncontrolled release of energy from glucose.
- Glycolysis wouldn’t occur
- Cell temperature would increase
Explain how oxygen produced during photosynthesis can be used during respiration.
- Oxygen is the terminal electron accepter
- Oxygen transforms into water at the ETC
Describe the role of coenzymes in aerobic respiration, using NAD+ or FAD as an example
- NAD+ used in glycolysis, link reaction or Krebs cycle
- NAD+ get reduced to NADH+ thus, NAD+ accepts electrons
- NADH+ is oxidised to release electrons to used at the ETC
ATP is a readily available source of energy for a cell. The primary substrate for the production of ATP is glucose. State one more possible substrate other than glucose.
- A lipid or protein
Describe how the structure of ATP is related to its function.
- ATP is a nucleotide made up of an Adenine nitrogenous base, 3 phosphate groups and a ribose sugar
- ATP can be hydrolysed or phosphorylated meaning it can be recycled
- ATP can lose a phosphate group in a hydrolysis reaction thus, releasing energy immediately
- ATP is soluble thus, it can readily react with other molecules
Compare and contrast anaerobic respiration in mice (Mus musculus) and yeast.
- Both can occur alongside aerobic respiration
- Both occur for a short amount of time
- Both use glucose as a substrate
- Both occur in the cytoplasm
- Anaerobic R in yeasts produces ethanol and CO2 whereas in mice, lactate is produced
- Both produce a small yield of ATP
- Ethanol fermentation in yeasts is more efficient than lactate fermentation
Give an example of a coenzyme
NAD+
