Section 5 - Chapter 12: Respiration - old Flashcards
What are the 4 stages of aerobic respiration
- Glycolysis
- Link reaction
- Krebs Cycle
- Oxidative phosphorylation
What are coenzymes
- A co-enzyme is a molecule that aids the function of an enzyme by transferring a chemical group from 1 molecule to another
What are examples of co-enzymes in respiration and what do they do
- NAD, Co-enzyme A and FAD
- NAD and FAD transfer hydrogen
- Co-enzyme A transfers acetate between molecules
What are the 2 different forms of cellular respiration
- Aerobic Respiration
- Anaerobic Respiration
What does Aerobic Respiration and Anaerobic Respiration produce
- Aerobic: CO2, Water and a lot of ATP
- Anaerobic: lactate (animals), ethanol and CO2 (plants/fungi) and a little bit of ATP
What happens in Glycolysis and what is the overall product?
- Splitting of a 6-carbon glucose molecule into 2 3-carbon pyruvate molecules
What happens in the Link Reaction and what are the overall products
- The 3-carbon pyruvate molecules enter into a series of reactions which lead to the formation of acetyl co-enzyme A (2-carbon molecule)
What happens in the Krebs Cycle and what are the overall products
- Acetyl Co-enzyme A goes into a series of oxidation-reduction reactions that yield some ATP and lots of reduced NAD and FAD
What happens in Oxidative Phosphorylation and what are the overall products
- The use of electrons, associated with reduced NAD and FAD synthesise ATP with water produced as a by-product
What are the 2 main stages in Glycolysis
- Phosphorylation
- Oxidation
What happens in Phosphorylation in Glycolysis
- Glucose is phosphorylated using a phosphate from ATP to create Glucose Phosphate and 1 ADP
- ATP is used to add a phosphate to Glucose Phosphate to make Hexose Biphosphate
- Each phosphorylated glucose molecule is split into 2 3-carbon Triose Phosphate
What happens in Oxidation in Glycolysis
- Hydrogen is removed from both Triose Phosphate molecules.
- Hydrogens are transferred to NAD to form 2 reduced NAD
- Enzyme controlled reactions convert each TP molecule in Pyruvate. (2 ATP produced - 4 in total)
What are the products if Glycolysis and what are their uses
- 2 NADH - goes to oxidative phosphorylation
- 2 Pyruvate - Actively transported into mitochondrial matrix for link reaction
- 2 ATP - used for energy
Where are the enzymes for Glycolysis found and what does this mean
- Found in the cytoplasm (takes place in cytoplasm)
- Glycolysis doesn’t require any organelle or membrane to take place
- It doesn’t require oxygen
What happens in the Link Reaction
- Pyruvate molecules are actively transported into the matrix of the mitochondria
- Pyruvate (3C) is oxidised to acetate (2 C). 1 CO2 and 2 hydrogens (forms NADH) released for 1 pyruvate
- The 2C acetate combines with co-enzyme A to produce acetyl coenzyme A
What are the products of the Link reaction and where do they go
- 2 Acetyl co-enzyme A - To the Krebs Cycle
- 2CO2 - Released as a waste product
- 2NADH - To oxidative phosphorylation
What are the main stages of the Krebs Cycle of Respiration
- Formation of a 6C compound
- Formation of a 5C compound
- Regeneration of Oxaloacetate
What happens in the Formation of a 6C compound in the Krebs Cycle
- The 2C acetyl CoA (from link reaction) combines with a 4C molecule (Oxaloacetate) to form a 6C compound Citrate.
- Co-enzyme A goes back to the link reaction to be used again.
What happens in the Formation of a 5C compound part of the Krebs Cycle
- In a series of reactions. Citrate is converted into a 5C compound
- Decarboxylation occurs 1 CO2 is removed
- Dehydrogenation occurs. Hydrogen is removed and forms NADH
What happens in the Regeneration of Oxaloacetate part of the Krebs Cycle
- The 5C compound turns into a 4C compound
- Decarboxylation and Dehydrogenation occurs and produces 1 ATP - substrate-level phosphorylation
- Produces 1 FADH, 2 NADH
What are the products of the Krebs Cycle and what are their uses
- 1 co-enzyme A - reused in the next link reaction
- Oxaloacetate - Regenerated for the use in the next Krebs Cycle
- 2CO2 - waste
- 1 ATP - energy
- 3 NADH and 1 FADH - oxidative phosphorylation
What is the importance of the Krebs Cycle
- Breaks down macromolecules into smaller ones - pyruvate broken into CO2
- Produces hydrogen atoms that are carried by NAD to electron transfer chain and provide energy for OP. This produces ATP
- It regenerates Oxaloacetate that combines with acetylcoenzyme A which would accumulate
- Is a source of intermediate compounds used by cells to manufacture substances like fatty acids, amino acids and chlorophyll.
Practical:
- What happens when you add hydrogen atoms to methylene blue
2) Why use a control tube
- Becomes reduced methylene blue (colourless)
- Show that the yeast was responsible for the colour change (glucose didn’t change methylene blue/ didn’t change by itself)
Tube A has yeast, glucose and methylene blue - colourless
Tube C has yeast, water, methylene blue - pale blue
Suggest explanation for the colours
- Yeast uses glucose as a respiratory substrate producing hydrogen - taken up by methylene
- Yeast uses stored carbohydrate as a respiratory substrate that has to be converted to glucose so the production of hydrogen is slower
How might the results in tube A after 15 minutes been different if carried out at different temperature 60°c
- Remained this because enzymes involved in respiration are denatured at 60°c
After 20 minutes tube A was mixed vigorously turning methylene blue again. How
- Air contains oxygen which would reoxidise methylene blue so it is blue
What is the process of the electron chain in OP
- Hydrogen atoms are released from NADH and FADH . They split into protons and electrons
- Electrons move down ETC in a series of oxidation-reduction reactions. As they flow the energy they release causes active transport of protons across mitochondrial membrane into the inner membranal space
- Protons accumulate in the inter membranal space they move into mitochondrial matrix via ATP synthase. The movement drives the synthesis of ATP
- In the mitochondrial matrix at the end of ETC. Protons, electrons and oxygen from blood combine to form water. Oxygen is the final acceptor
How are lipids used as a respiratory substrate
- Before being respired, lipids are first hydrolysed to glycerol and fatty acids
- Glycerol is phosphorylated and converted to triose phosphate which enters glycolysis
- Fatty acid is broken down 2-carbon fragment which are converted into acetyl coenzyme A
- Hydrogen atoms are released
How are proteins used as a respiratory substrate
- It is first hydrolysed to amino acids.
- They have their amino group removed before entering the respiratory pathway at different points depending on the number of carbon atoms.
- 3 carbon compounds - pyruvate
- 4/5 converted to intermediates in the Krebs Cycle.
What happens when there is an absence of oxygen
- Neither the Krebs cycle nor ETC can continue as all FAD and NAD will reduce
- NO FAD or NAD will take up H+ from Krebs so enzymes will stop working
- Leaves only glycolysis
What do the 2 ways in Eukaryotic cells during anaerobic respiration produce
- In plants and yeast the pyruvate is converted into ethanol and CO2
- In animals the pyruvate is converted to lactate
What happens in anaerobic respiration with plants/yeast
- The pyruvate molecule formed at the end of glycolysis loses a molecule of carbon dioxide to produce ethanal
- This accepts hydrogen from reduced NAD to produce ethanol.
What happens in anaerobic respiration in animals
- Produces lactate in means of overcoming a temporary shortage of oxygen
- Lactate production occurs in muscles exercise may cause oxygen debt.
- NAD can accumulate and must be removed therefore each pyruvate takes up 2 hydrogen atoms from NADH to form lactate.
What happens to the lactate when there is oxygen again
- Lactate is oxidised to pyruvate
- This can be further oxidised to release energy or converted to glycogen
- Lactate can cause muscle cramp. Lactate is an acid - cause pH changes (enzymes)
Energy from cellular respiration is derived from 2 ways
- Substrate-Level Phosphorylation: in Glycolysis and the Krebs Cycle. This is the direct transfer of a phosphate from a respiratory intermediate to ADP
- Oxidative Phosphorylation: In the ETC. Involving energy of the hydrogen atoms from NAD/FAD.
In anaerobic respiration how is ATP formed
- Pyruvate is converted to either ethanol or lactate. Not available for the Krebs Cycle or ETC.
- Only ATP produced is from the Glycolysis stage
