Bioenergetics 1 - Life & Energy (incl. Bomb Calorimeter)

Question 1

Ultimately, why do we breathe?

Answer 1

So that we can produce energy in the form of ATP!

Question 2

EVERY cell has the capacity for self-………… and self-…………… .

Answer 2

Replication, assembly.

Question 3

What is the bioenergetics definition of energy?

Answer 3

How living systems capture, transform and use energy to perform work and stay alive.

Question 4

Name some forms of biological work.

Answer 4

Synthetic, mechanical, concentration (e.g. active transport), electrical, heat, bioluminescent.

Question 5

Hydrocarbons + oxygen =

CH4 + 2O2 =

Answer 5

Water + carbon dioxide + energy.

H2O + CO2 + energy.

Question 6

Dietery fuel / carbohydrates and lipids + oxygen =

C6H12O6 + O2 =

Answer 6

Carbon dioxide + water + energy.

6CO2 + H2O + energy.

Question 7

How would a biochemist define energy?

Answer 7

Usually, as the chemica energy that is exchanged in a reaction, e.g.:

ATP to ADP, NADH to NAD+ or Glucose to CO2 and H2O.

Question 8

What is the activation energy of a reaction?

Answer 8

How much energy is required for the reaction to take place.

Question 9

What effect does an catalyst have on the activation energy of a reaction?

Answer 9

A catalyst lowers the activation energy of a reaction.

Question 10

Are living creatures efficient in their chemical reactions?

Answer 10

No!

Question 11

True or false? Reactions in living creatures always have a start and an end point.

Answer 11

False.

Question 12

Why is non-equilibrium thermodynamics used in living organisms?

Answer 12

Non-equilibrium thermodynamics are used in living organisms because they are very inefficient and the reactions do not have a start and end point.

Question 13

Why can’t equilibrium thermodynamics be used in living organisms?

Answer 13

Reactions in living organisms do not have start and end points.

Question 14

Define a ‘system’.

Answer 14

The matter within a defined region of space.

Question 15

What is an open system? Give an example.

Answer 15

In open systems, matter AND energy can be exchanged between the system and its surroundings.

e.g. ocean.

Question 16

What is a closed system? Give an example.

Answer 16

In a closed system, energy can enter and leave the system into the surroundings, but matter is trapped within the system.

e.g. greenhouse.

Question 17

What is an isolated system? Give an example.

Answer 17

An isolated system is one where both energy and matter are trapped inside the system and cannot leave.

e.g. gas cylinder.

Question 18

What is the concept of equilibrium thermodynamics?

Answer 18

‘Man-made machines are devices which allow energy to be transformed from one type to another’.

Question 19

What is this concept called?:

‘Man-made machines are devices which allow energy to be transformed from one type to another’.

Answer 19

Equilibrium thermodynamics.

Question 20

What is the First Law of Thermodynamics?

Answer 20

Energy within a system is conserved, it can be converted from one form to another but it cannot be created or destroyed.

Question 21

If a reaction occurs in a well-insulated container, there is no ……………… exchange.

If a piston is prevented from moving, there is no …………….. done.

This is the principle of the …………… …………….. .

Answer 21

Heat, work, bomb calorimeter.

Question 22

ΔE = Q-W.

What does this reaction show?

Answer 22

Change in energy = heat added to the system - work done.

Question 23

If there is no heat exchange and Q = 0. What does ΔE = ?

Answer 23

-W.

Question 24

If no work is done and W=0, what is ΔE?

Answer 24

Q.

Question 25

Which instrument is the MOST DIRECT way of measuring the energy content of foodstuffs and metabolites?

Answer 25

The bomb calorimeter.

Question 26

In a bomb calorimeter, the energy produced by combusting or oxidising a substrate can be measured as…?

Answer 26

A change in internal energy, ΔE.

Question 27

In exothermic reactions, is ΔE always positive or always negative?

Answer 27

In exothermic reactions, ΔE is ALWAYS negative.

Question 28

What is the enthalpy of a system?

Answer 28

A measurement of heat change during a reaction at a constant pressure and volume.

Question 29

Why is enthalpy used for changes in internal energy in living systems?

Answer 29

The temperature difference between the system and the surroundings are small.

Question 30

What does this equation calculate?

ΔE = ΔH - PΔV

where H is heat, P is pressure and V is volume.

Answer 30

Enthalpy of a system.

Question 31

If, in biology,

Question 32

If, in biology, we assume pressure and volume to be constant, what does this mean for the following equation?:

ΔE = ΔH - PΔV

Answer 32

If we assume P and ΔV to be constant, then ΔH = ΔE.

Question 33

What does ΔH mean?

Answer 33

The enthalpy of ‘heat combustion’.

Question 34

What units does ΔH, enthalpy of heat combustion have?

Answer 34

Joules.

Question 35

When glucose is completely burned in a bomb calorimeter, the energy released is -2,810kJmol-1, whereas when a fatty acid is burned -9,950kJmol-1 is released. What does this tell us about glucose vs. fatty acids?

Answer 35

Fatty acids are better for storing energy than glucose because they can hold more energy per mole.

Question 36

Outline how a bomb calorimeter can be used to calculate the energy produced in a reaction.

Answer 36

1. Combust a fixed quantity of substance one and measure ΔH1.
2. Repeat for ΔH2 in a separate reaction.
3. ΔH? = ΔH1 - ΔH2.

Make sure to account for how many molecules of product are made for each molecule of reactant!

Question 37

Which is more efficient - sprinters using ‘fast’ muscles to convert glucose to lactate anaerobically, or marathon runners using ‘slow’ muscles to convert glucose and fat to carbon dioxide and water aerobically?

Answer 37

Marathon runners.

Question 38

True or false? In extreme circumstances, heart muscle can convert fatty acids to carbon dioxide and water in aerobic respiration.

Answer 38

True.

Question 39

How efficient is lactobacillus in converting glucose to lactate?

a. 1.8%
b. 18%
c. 81%.

Answer 39

1.8%!

Question 40

How efficient is skeletal muscle in converting glucose to lactate?

a. 1.8%
b. 18%
c. 81%.

Answer 40

1.8%!