chapter 12 Flashcards
Why do we need ATP (energy)?
● Anabolic reactions e.g. synthesis of DNA and
proteins
● Active transport
● Movement
● Homeostasis
Why is ATP used for energy?
● ATP is tri-phosphorylated. The removal of each
phosphate releases energy.
● ATP is easily hydrolysed and water-soluble (easy
to transport), making it a useful source of energy.
Name the four main stages of aerobic respiration and state where they occur.
● Glycolysis - cytosol
● Link reaction - mitochondrial matrix
● Krebs cycle - mitochondrial matrix
● Electron transport chain - inner mitochondrial
membrane
Outline the stages of glycolysis.
- Glucose (hexose sugar) phosphorylated to hexose
bisphosphate by 2× ATP - Hexose bisphosphate splits into 2× triose phosphate (TP)
- 2 molecules of TP oxidised to 2× pyruvate
Net gain of 2× reduced NAD (NADH) and 2× ATP per glucose.
Draw a flowchart to explain glycolysis.
https://ibb.co/8PnX31L
How does pyruvate from glycolysis enter the mitochondria?
Via active transport (oxygen is required)
What happens during the link reaction?
- Oxidative decarboxylation and dehydrogenation of
pyruvate to form acetate
Net gain of CO2 and 2× reduced NAD
- Acetate combines with coenzyme A (CoA) to form
acetyl coenzyme A
Draw a flowchart to summarise the link reaction.
https://ibb.co/8MhdZwx
Define “substrate level phosphorylation”.
The synthesis of ATP by the transfer of a
phosphate group from a phosphorylated
intermediate to ADP.
What happens in the Krebs cycle?
Series of redox reactions that produces:
● ATP by substrate-level phosphorylation
● Reduced coenzymes
● CO2 from decarboxylation
Begins when the acetyl group from Acetyl CoA (2C) reacts with oxaloacetate (4C).The cycle regenerates oxaloacetate.
Draw a diagram to explain the Krebs cycle.
https://ibb.co/P66Bfcc
What is the electron transfer chain (ETC)?
● Series of carrier proteins embedded in the
membrane of the cristae of mitochondria
● Produces ATP through oxidative
phosphorylation via chemiosmosis during
aerobic respiration
What happens in the electron transfer chain (ETC)?
● Electrons released from reduced NAD and FAD
undergo successive redox reactions
● The energy released is coupled to maintaining the
proton gradient or is released as heat
● Oxygen acts as the final electron acceptor
How does chemiosmosis produce ATP during aerobic respiration?
Some energy released from the ETC is coupled to the active transport of H+ ions (protons) from the mitochondrial matrix into the intermembrane space.
H+ ions move down their concentration gradient into the mitochondrial matrix via the channel protein ATP synthase.
ATP synthase catalyses ADP + Pi → ATP
Note: chemiosmosis also occurs in photosynthesis in chloroplasts.
Draw a diagram to represent the ETC and chemiosmosis.
https://ibb.co/jM7QYsd
State the role of oxygen in the electron transfer chain.
Final electron acceptor:
O2 + 4H+ + 4e- → 2H2O
Name the stages in respiration that produce ATP by substrate-level phosphorylation.
● Glycolysis (anaerobic)
● Krebs cycle (aerobic)
What is the respiratory quotient? Write the equation.
Ratio of CO2 produced to O2consumed.
RQ = CO2/O2
What is the RQ of carbohydrates, lipids and proteins?
● Carbohydrates: 1
● Lipids: 0.7-0.72
● Proteins: 0.8-0.9
What could an RQ of greater than 1indicate?
● May indicate the conversion of carbohydrates to lipids
● RQ in anaerobic respiration is ∞
Why do different respiratory substrates have different relative energy values?
Depends on the number of hydrogens in
the structure which are oxidised to water
e.g. the number of hydrogens is greater
in fatty acids than carbohydrates.
Outline anaerobic respiration in muscle cells.
● Only glycolysis continues
● Reduced NAD (product of glycolysis) transfers
the H to pyruvate, forming lactic acid and
regenerating NAD
● Catalysed by enzyme lactate dehydrogenase
Draw a flowchart to show how lactic acid is produced during anaerobic respiration in muscle cells.
https://ibb.co/jM7QYsd
Outline anaerobic respiration in plants and microorganisms.
● Only glycolysis continues
● Pyruvate is decarboxylated to form ethanal
● Ethanal accepts a H from reduced NAD making ethanol. NAD
regenerated for glycolysis
● Less ATP is produced than in aerobic respiration
