Respiration 5.1.7 Flashcards
Why is ATP the energy currency of the cell
-ATP can be quickly made and brocken down
-Hydrolysis of ATP releases small manageble quantities of energy so not more energy is released than needed
Why is it ideal that respiration occurs in the mittochondria?
-Provides an isolated environment with ideal conditions for respiration
-Have their own DNA to produce enzymes for respiration
What is the definition of a coenzyme? and what do NAD and FAD do?
-A molecule that aids the function of an enzyme by transfering a chemical group from one molecule to another
-NAD and FAD can reduce or oxidise to give or take hydrogen from a molecule, therefore they are coenzymes that can transfer protons and electrons from a molecule
What are the four stages of respiration?
-Glycolysis
-The link reaction
-The krebs cycle
-Oxidative Phosphorylation
True or False: The first 3 stages of respiration products are used in the final stage to produce lots of ATP
True
Describe key facts about glycolysis?
-Glucose makes pyruvate from glucose
-Occurs in the cytoplasm
-Anaerobic
-Two stages:
=>Phosphorylation
=>Oxidation
What is phosphorylation and lysis?
Phosphorylation: The addition of an inorganic phosphate to a protein
Lysis: Splitting by destabillisation
Describe the process of Glycolysis?
1.Phosphorylation: two phosphates are released from ATP and join to glucose to form hexose bisphosphate
2.Lysis: hexose bisphosphate is split into two triose phosphate
3. Phosphorylation: a phosphate group is added to both TP molecules (pᵢ was free in cytoplasm)
4. Dehydrogenation and formation of ATP: TB molecules are oxidised by the removal of hydrogen, which reduces NAD, two phoshate groups are removed and added to form ATP
What is substrate level phosphorylation?
The formation of ATP without electron transport chains
Describe the link reaction?
1.Pyruvate enters the mitochondrial matrix by active transport (carrier protein)
2. Oxidative decarboxylation occurs-removal of carbon dioxide and oxidation: removal of hydrogen
3.NAD⁺ accepts H to form NADH
4. This leaves a two carbon acetyl group which binds to coenzyme A to form acetylcoenzyme A
Describe the Krebs cycle?
1.Acetyl CoA delivers an acetyl group which combines with oxaloacetate to form a six-carbon citrate
2.Citrate undergoes decarboxylation and dehydrogenation which produces one reduced NAD and CO₂ and a 5 carbon compound is formed
3. The 5 carbon compound undergoes further decarboxylation and dehydrogenation eventually regenerating to oxaloacetate
4. The net products of Krebs cycle are 2ATP, 6 reduced NAD, 2 FAD and 4CO₂ (cycle happens twice)
How many times does glycolysis, the link reaction and the Krebs cycle occur per molecule of glucose?
-Glycolysis: once
-The link reaction: twice
-The Krebs cycle: twice
What location does glycolysis, the link reaction and the Krebs cycle take place
-Glycolysis: Cytoplasm of the cell
-Link reaction: Mitochondrial matrix
-Krebs cycle: Mitochondrial matrix
Describe the process of Oxidative Phosphorylation?
- Occurs across the inner membrane of the mitochondrion, reduced NAD and FAD release hydrogen atoms and become oxidised (catalysed by NADH dehydrogenase), hydrogen atoms split into protons (H⁺) and electrons (e⁻)
- Electrons move along the electron transport chain, losing energy at each carrier
- Some of this energy is used to pump H⁺ from matrix into intermembrane space, rest is lost as heat
- The concentration of protons is higher in the intermembrane space than matrix, protons move down their electrochemical gradient back into matrix via ATP synthase
- This movement drives the synthesis of ATP from ADP and Pᵢ, this is called chemiosmosis
- Oxygen then combines with the protons and electrons to form water
What is the theoretical yield of ATP from aerobic respiration and why is it usually lower?
-38 ATP molecules per glucose molecule
=> Some ATP is used to transport pyruvate and reduced NAD into the mitochondria
=> Some protons may leak out through the outer mitochondrial matrix
Label this diagram of a mitochondria
1: Outer mitochondrial membrane
2: Cristae
3: Matrix
4: Intermembrane space
What is the difference between NAD and FAD?
-NAD takes part in all the stages of cellular respiration whereas FAD only in Krebs cycle.
-NAD accepts on H⁺ whereas FAD
-Reduced NAD results in the synthesis of 3 ATP molecules whereas reduced FAD only results in 2.
How much ATP does aerobic and anaerobic respiration yield?
-Aerobic respiration: 38 ATP
-Anaerobic respiration: 2 ATP
What are the different categories of organisms determined by their dependence of oxygen?
-Obligate anaerobes: cannot survive in prescence of oxygen
-Faculatative anaerobes: can synthesise ATP by both aerobic and anaerobic respiration
-Obligate aerobes: can synthesise ATP aerobically but can only synthesis ATP anaerobcally for short periods
How does a lack of oxygen prevent aerobic respiration
-Without oxygen, oxidative phosphorylation and Krebs cycle can’t function, Coenzymes like NAD⁺ accumulate
Describe the process of Lactate fermentation in mammals?
1.Pyruvate acts as a hydrogen acceptor, taking h⁺ from NADH, and is converted into lactate, this is catalysed by the enzyme lactate dehydrogenase
2.NAD⁺ is regenerated
3. Lactic acid is converted back into glucose in the liver, requires oxygen
Draw the process of lactate fermentation in mammals
What is the lactate fermentation equation?
Why can’t lactate fermentation occur indefinetly?
-Reduced ATP would not be enough to sustain vital processes for a long time
-Accumulation of lactic acid would cause a fall in PH inhibiting enzymes
Draw the process of alcoholic fermentation in plants and yeast?
Ethanol dehydrogenase catalyses the conversion of ethanal into ethanol
What is the differences between Lactate fermentation and Ethanol fermentation? (Hydrogen acceptors,CO₂ produced?, end products and site)
-Hydrogen acceptor: LF>Pyruvate and EF>Ethanal
-CO₂ produced: LF>no EF>Yes
-End products: LF>Lactate,NAD⁺ EF>Ethanol, CO₂, NAD⁺
Which molecule has the highest energy value when used as a substrate for respiration? (Lipids,Proteins and carbohydrates) and why?
-Lipids are highest, then proteins and then carbohydrates
-Substrates with more hydrogen atoms per unit mass will cause more ATP to be produced as ATP is mostly made in oxidative phosphorylation from reduced NAD and FAD
Describe how Lipids are respired?
- Triglycerides are hydrolysed into glycerol and fatty acids, glycerol is converted into triose phosphate and respired
- Fatty acids combines with coenzyme A and complex is transported into mittochondrial matrix
- Fatty acids are brocken down into acetyl groups and released from CoA and enter the Krebs cycle
How is protein respired?
- Deaminated in liver (amino group removed and converted into urea)
- The rest of the amino acid molecule, a keto acid enters the respiratory pathway
What are the respiratory quotients equations?
What does it mean when the RQ is more than 1 and can you work out the respiratory quotient for a whole organism?
-It means that some anaerobic respiration is taking place as more carbon dioxide is being produced than oxygen consumed
-Yes, do the mean for all the respiratory quotients for all different substrates, this is usefull as it can tell you what kind of respiration is being carried out.
Describe how to use a respirometer?
- Place a known mass in 1 respirometer tube and place manometer fluid in the manometer and open tubes
2.Place apparatus in water bath for 10 mins and mark level of fluid with pen - Close taps and leave for 10 mins and measure change in fluid, and if radius of tube is known volume
- Calculate the volume of oxygen absorbed per gram of organism per minute
Describe one method to measure the respiration rates of yeast?
- Yeast and sugar solution are placed in a fermentor tube
- This is inverted and pushed to end of a test tube
- Volume of CO₂ produced by yeast in anaerobic respiration can then be measured in a set time
