Cellular Energetics

Question 1

• Breathing air (oxygen) from birth to death is ONLY so that

Answer 1

biological

oxidations can take place in the cells

Question 2

• The mitochondria use oxygen to

Answer 2

generate energy (ATP) – this is called ‘oxidative phosphorylation’

Question 3

• Fuels such as glucose and fatty acids are used to

Answer 3

generate energy in
the form of ATP (from ADP & Pi
)

Question 4

• The energy in ATP is available for:

Answer 4

i) moving ions across membranes against their conc. or electrical
gradient
ii) muscle contraction
iii) nerve conduction etc.

Question 5

How is fuel ENERGY Quantified?

Answer 5

The BOMB Calorimeter

Question 6

The BOMB Calorimeter

Answer 6

Food is ignited
• ∆Temp of H2O is measured
• Thermal capacity of H2O is
known
• Mass of sample is known
• Therefore, the oxidative
energy content can be
calculated

Question 7

The _____ ______ content of a food sample is the same whether
liberated by uncontrolled combustion in a bomb calorimeter or by
controlled enzymatic decomposition within the cells of living organisms.

Answer 7

oxidative energy

Question 8

BOMB Calorimeter will tend to over estimate energy available

Answer 8

Cellulose ,Fibre = food material that can’t be digested ( humans dont have enzymes to break down)

Question 9

Oxidising different fuels yields similar amounts

of energy per unit O2 consumed

Answer 9

Glucose, Fat, Protein
Energy released (kJ g-1) = 16,39, 18

Question 10

Glucose metabolism eqn

Answer 10

𝐂6𝐇12𝐎𝟔 + 𝟔O2 + 32ADP + 32Pi → 6CO2 + 6H2O + 𝟑2ATP

Question 11

The main waste products of mitochondrial oxidation of substrates are

Answer 11

CO2 and NH3 (ammonia)

Question 12

CO2 and NH3 (ammonia)
Both are water soluble & carried in the blood
– CO2 excreted by ?
– NH3 carried to liver where?

Answer 12

diffusion into the lung & by the kidney as HCO3-

it is eventually converted to urea & excreted by the kidneys.

Question 13

α-ketoglutarate (TCA cycle) is important for _____ __________. Reaction with ___means that it is not available
for oxidative phosphorylation and this can be toxic, especially to the brain.

Answer 13

oxidative phosphorylation
NH3

NH3 + α ketoglutarate → glutamate + H2O

Question 14

VO2max

Answer 14

• the maximal rate of consumption of oxygen
• a measure of ‘aerobic capacity’
• units are L/min
(or L min-1)

Question 15

VO2 max is reached when

Answer 15

oxygen consumption remains at a

steady state despite an increase in workload

Question 16

Fick principle used to measure VO2

Answer 16

• Subject breathes using a respiratory valve
• Inspired gas content known
• Expired air analysed for O2 & CO2 content
• Volume expired measured

Question 17

Energy Efficiency

Answer 17

Mechanical Output: Work rate (Power), Speed, Distance, Time (heat)
over
• Metabolic Input: Fuel usage, O2 uptake, ATP turnover

Question 18

Efficiency eqns

Answer 18

=
output/input
=
power/VO2

Question 19

Energy can be used by the cell for:

Answer 19

1. Chemical work: moving a molecule against its concentration
   gradient
2. Electrical work: moving a molecule against its electrical gradient
3. Mechanical work: e.g muscle contraction

Question 20

The Sarcolemmal Na+/K+-ATPase

Answer 20

a membrane-bound electrogenic enzyme that moves Na+ out of
the cell (efflux) and K+ into the cell (influx) against their
concentration gradients and electrical gradient (Na+)

3Na+ out & 2K+ in

Question 21

Electro-chemical Work

Answer 21

The TOTAL work done (i.e. energy performed) in
moving an ion across the sarcolemma is merely the
sum of the chemical and electrical components:

Question 22

The PRINCIPLE Energy Sinks of exercising skeletal /

cardiac muscle are:

Answer 22

1. The sarcolemmal Na+/K+ ATPase
2. The sarcoplasmic reticular Ca2+ -ATPase
3. The cross-bridge actomyosin-ATPase

Question 23

These Energy Sinks perform Work:

Answer 23

1. Chemical
2. Electrical
3. Mechanical

Question 24

Main energy ‘sink’ in active muscle cells

Stoichiometry is 1 ATP: 1 crossbridge

Answer 24

Myosin ATPase

Question 25

The WORK performed in pumping Ca2+ ions from cytoplasm back into sarcoplasmic
reticulum (SR):

Answer 25

The Sarcoplasmic Reticular
Ca2+-ATPase (SERCA)
1ATP for 2 Ca++

Question 26

The ‘Cost’ of a Contraction Trigger

Answer 26

Ca2+ ions are released from the sarcoplasmic reticulum (SR) and
bind to the myofilaments to trigger contraction.
Ca2+ is then taken back up into the SR by the SRCa2+-ATPase pump.