Energy For Life

Question 1

Equation for respiration

Answer 1

Oxygen + Glucose -> Carbon Dioxide + Water (+ATP)
6O2 + C6H12O6 -> 6CO2 + 6H2O

Question 2

What is ATP

Answer 2

Energy for cells

Question 3

Aerobic respiration

Answer 3

WITH oxygen
Oxygen + Glucose -> Carbon Dioxide + Water (+ATP)
O2 + C6H12O6 -> 6CO2 + 6H2O

Question 4

Anaerobic Respiration
Plants + fungi
Animals

Answer 4

WITHOUT oxygen
(Animals)
glucose → lactic acid

(Fungi + Plants)
glucose → ethanol + carbon dioxide

Question 5

Describe the practical can we use to investigate the production of carbon dioxide and heat in respiring cells

Answer 5

Pea Practical
As the peas grow they respire + release heat.
The thermos flask is insulated, so heat is not transferred to the surroundings and we can measure the change in temperature.
Temperature rise in thermos A only, as the peas in thermos B are dead (they have been boiled).
In both thermos flasks the peas are soaked in Milton solution (bleach). This kills any bacteria which would also respire and so would affect the results.
We could also use gas delivery tubes to collect any gas produced. The gas can then be bubbled through limewater. The gas from flask A only would turn the limewater cloudy - this shows that carbon dioxide is produced.

Question 6

Define diffusion and name two factors which can affect it

Answer 6

The random movement of particles from an area of high concentration to an area of lower concentration

1. Temperature - At higher temperatures, molecules have more kinetic energy and so move faster so diffusion occurs faster
2. Concentration gradient - If there is a very large difference in concentration between to areas,
   molecules will diffuse from the higher to the lower concentration quickly. If the concentration gradient
   (difference) is small, diffusion will happen more slowly.
3. Distance - Diffusion takes longer if the molecules have to travel further*. Therefore cells are small
   (smaller volume reduces distance).
4. Surface area: volume ratio - A larger surface area speeds up the rate of diffusion as there are more
   opportunities for the molecules to move, which is why surfaces such as alveoli in lungs are so large.
   Surface area to volume ratio is more significant, as the two counteract (oppose) each other: an
   efficient exchange surface has a surface area which is very large compared to the distance the
   molecules must travel. SA:V is increased when structures are small.

Question 7

Explain why the gas exchange system is well suited to its purpose

Answer 7

Many alveoli = high surface area
Each alveoli has its own blood supply = high concentration gradient
The alveoli wall is only one cell thick -> short diffusion distance

Question 8

Describe a practical that investigates diffusion

Question 9

What happens in exhalation

Answer 9

Ribs = down and in
Intercostal muscles = down and in
Air pressure is higher/lower than outside

Question 10

What happens in inhalation

Answer 10

Ribs = up and out
Intercostal muscles = up and out
Diaphragm contracts and flattens
Air pressure is higher/lower than outside
Volume of thorax increases, therefore pressure decreases

Question 11

What can ATP be used for?

Answer 11

1. Building large molecules such as protein
2. Transporting molecules (active transport)
3. Cell division (meiosis)
4. Contraction of muscles (movement)

Question 12

What is the difference between anaerobic respiration and aerobic respiration?

Answer 12

Aerobic respiration uses oxygen and produces carbon dioxide + water
Anaerobic respiration doesn’t use oxygen (only uses glucose) and produces toxic waste products such as lactic acids (animals) and ethanol and carbon dioxide (plants and fungi)

Question 13

What is the volume of oxygen needed to oxidise the lactic acid in the liver called?

Answer 13

Oxygen debt

Question 14

Test for carbon dioxide

Answer 14

Carbon dioxide bubbled through limewater turns cloudy

Question 15

Advantage of anaerobic respiration

Answer 15

It allows cells to obtain a small amount of energy when O2 is limited