Ch 12 Energy and respiration Flashcards
What adenosine triphosphate?
- ATP
- a nucleotide derivative
- consists of ribose, adenine and three phosphate groups
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.
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
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.
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.
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 O2 consumed.
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 1 indicate?
● 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
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
Name two types of molecule that can be used as
alternative respiratory substrates.
● (amino acids from) proteins
● (glycerol and fatty acids from) lipids
Compare the efficiency of aerobic and anaerobic
respiration
Hydrolysis of 1 mole glucose produces 2880 kJ. 1 molecule ATP produces
30.6 kJ. In aerobic respiration 32 ATP are gained whereas in anaerobic 2
ATP are gained.
● Aerobic efficiency= [(32 × 30.6)/2800] × 100 = 34%
● Anaerobic efficiency= [(2 × 30.6)/2800] × 100 = 2.1%
● Aerobic respiration is = 34/2.1= 16.2× more efficient than anaerobic
Define oxygen debt and oxygen deficit.
● Oxygen debt (also referred to as Excess Post-Exercise
Oxygen Consumption or EPOC) is the amount of additional
O2 needed after exercise to return body systems to their
previous state
● Oxygen deficit is the volume of O2 required during exercise
minus volume of O2 obtained
How is rice adapted for growth in a low oxygen
environment?
● Rapid growth maintains flowering parts above water line allowing gas
exchange through the leaves
● Aerenchyma in stem allows gases to move to submerged parts of the
plant
● Hydrophobic coating on leaves maintains air film around plant
● Root cells produce alcohol dehydrogenase to offset ethanol toxicity from
anaerobic respiration
How can DCPIP be used to measure respiration in
yeast?
To establish the chemiosmotic gradient, H+ is pumped
out of the matrix. H+ reduces DCPIP producing a
colour change from blue to colourless. The rate at
which this change takes place allows us to measure
the rate of respiration in yeast.
Define the term “respirometer”.
A device used to determine respiration
rate in living organisms by measuring the
change in volume of oxygen or carbon
dioxide.
How could a student calculate the rate of respiration
using a respirometer?
volume of O2 produced or CO2 consumed/ time ×
mass of sample
volume = distance moved by coloured drop ×
(0.5 × capillary tube diameter)2 × π
