Respiration Flashcards
Specification reference: 5.2.2
Glucose
- Hexose sugar produced during photosynthesis
- Contains energy absorbed from sunlight with C-H Bonds
Carbon framework of glucose
The C-H bonds and glucose is broken down
-Energy is released and used for the synthesis of ATP by chemiosmosis
Respiration
Complex multi step pathway
Eukaryotic cells
Takes place in the mitochondria of cells
Prokaryotic cells
Do not have a mitochondria so many reactions take place in the cell membrane
What is the first stage of respiration?
Glycolysis
Glycolysis
Glycolysis - Step 1: Phosphorylation
Phosphorylation: Two phosphates released from the 2 ATP molecules are attached to a glucose molecule forming hexose bi-phosphate
Glycolysis - Step 2: Lysis
Lysis: This destabilises the molecule causing it to split into 2 triose phosphate molecules
Glycolysis - Step 3: Phosphorylation
Phosphorylation: Another phosphate group is added to each triose phosphate forming 2 bi phosphate molecules.
-These phosphate groups come from free inorganic phosphate ions present in the cytoplasm
Glycolysis - Step 4: Dehydrogenation + Formation of ATP
Dehydrogenation + Formation of ATP: 2 triose bi-phosphate molecules are the oxidised by the removal of hydrogen atoms (dehydrogenation) to form 2 pyruvate molecules.
-NAD co-enzymes accept the removed hydrogen’s (which are reduced) forming NADH
Substrate level phosphorylation
formation of ATP without an electron transport chain.
-ATP is formed by the transfer of a phosphate group from triose bi phosphate to ADP
Overall Net ATP yield
Two ATP molecules are used at the beginning and 4 ATP molecules are produced so 2 is produced overall
Cristae
Projections of the inner membrane which increase SA available for oxidative phosphorylation
Inner mitochondrial membrane
Contains electron transport chains and ATP Synthase
Outer mitochondrial membrane
Separates the contents of the mitochondrion from the rest of the cell, creating a cellular compartment with ideal conditions for aerobic respiration
Matrix
Contains enzymes for the Krebs cycle and the link reaction. It also contains mitochondrial DNA
Inter membrane Space
Proteins are pumped into the space by the electron transport chain. The space is small so the concentration builds up quickly
The link reaction (oxidative decarboxylation)
This is the first step in anaerobic respiration. This is referred to as the link reaction because it links anaerobic glycolysis occurring in the cytoplasm, to the aerobic steps of respiration in the mitochondria
Link Reaction - Step 1: Movement
(Eukaryotic cells): Pyruvate enters the mitochondria matrix by active transport via specific carrier proteins
Link Reaction - Step 2: Removal
Pyruvate then undergoes the link reaction and CO2 is removed (decarboxylation),along with hydrogen (oxidation).
Link Reaction - Step 3: Hydrogen
Hydrogen atoms which are removed are accepted by NAD. NAD is reduced to form NADH
Link Reaction: Step 4: Acetyl
2 carbon acetyl group is formed and binds to an coenzyme A which results in acetyl COA
Link Reaction: Step 5: Delivery
The acetyl coa is delivered to the krebs cycle.
What is the reduced NAD used for?
Oxidative phosphoryalation to synthesise ATP
Explain why the removal of carbon dioxide in the link reaction is oxidative (2 marks)
Hydrogen is also removed (1); removal of hydrogen oxidises pyruvate (1).
Name one organic compound and one organic compound and one inorganic compound produced in the link reaction? (2 marks)
Acetyl group (1); carbon dioxide (1)
Suggest why glcolysis occurs in the cytoplasm but not the mitochondrial matrix (4 marks)
Enzymes required are in cytoplasm/ORA (1); glucose molecule too large to move into
mitochondrion (1); no transport proteins for pyruvate (1); mitochondria not originally present in
(eukaryotic) cells (1).
Where does the Krebs cycle take place?
The mitochondrial matrix where each complete cycle results in the breakdown of an acetyl group
Krebs Cycle: Step 1: Entrance
Acetyl Coenzyme A brings the Acetyl group into the krebs cycle. The two carbon acetyl group combines with 4 carbon oxaloacetate to form citrate
Krebs Cycle: Step 2: Decarboxylation + Dehydration
The citrate molecule molecule undergoes decarboxylation and dehydration producing one reduced NAD and CO2. A five carbon molecule is formed
Krebs Cycle: Step 3: Further Decarboxylation + Dehydration
The five carbon compound undergoes further decarboxylation and dehydration , eventually regenerating oxaloacetate.
Krebs Cycle: Step 4: Cycle continues
The cycle continues so more CO2 and 2 more reduced NADs and one reduced FAD are produced. ATP is also produced by substrate- level phosphorylation
