Breathing

Question 1

Why is surface area to volume ratio important in biology

Answer 1

• the surface are to volume ratio reduces as an object gets bigger
  So for small object it has a large surface area to volume ratio
• smaller objects therefore have a shorter diffusion distance and simple diffusion is sufficient for exchanging materials
  Whilst bigger objects have a bigger diffusion distance and simple diffusion is no longer enough to exchange materials
• this is why multicellular organisms have special exchange surfaces with adaptations

Question 2

What are adaptations of exchange surfaces

Answer 2

• having a large surface area for a larger area over which exchange can take place
• being thin, provides a short diffusion path
• having an efficient blood supply (animals), which moves the diffusing substances away, maintaining a concentration gradient for diffusion
• being ventilated (animals), makes gas exchange more efficient more efficient by maintaining steep concentration gradients

Question 3

What is ventilating, breathing

Answer 3

The process of oxygen diffusing into the bloodstream and carbon dioxide diffusing out of

Question 4

Parts of the gas exchange system

Answer 4

Nose/mouth
Trachea
Bronchi (entrance to each lung)
Bronchioles (inside the lungs)
Alveoli sacs

Question 5

What are the alveoli’s job

Answer 5

• sight of gas exchange
• inhaled oxygen diffuses from the alveoli into the bloodstream
• waste carbon dioxide diffuses from the blood plasma into the alveoli to be exhaled

Question 6

Adaptations of the alveoli

Answer 6

• there are millions of alveoli in the lungs giving it a huge surface area
• alveoli are surrounded by a network or capillaries (strong blood supply) keeping a steep concentration gradient for diffusion
• they have very thin walls reducing diffusion distance

Question 7

Describe the movement of the lungs when breathing in

Answer 7

• intercostal muscles contract, pulling the ribs upwards and outwards
• diaphragm contracts and flattens
• these 2 movements increase the volume of the thorax as the same amount of gas is now inside a much bigger space
  So, the pressure inside the thorax is much lower than the pressure outside your body, causing air to move into the lungs

Question 8

Describe the movement of the lungs when breathing out

Answer 8

• the intercostal muscles relax Cardin your ribs to drop down again
• the diaphragm replace and curves back into a dome
  *these 2 movements decrease the volume of the thorax meaning there is much more air pressure in the chest, forcing air out of the lungs

Question 9

Composition of inhaled air

Answer 9

Nitrogen 80%
Oxygen 20%
Carbon dioxide 0.04%

Question 10

Composition of exhaled air

Answer 10

Nitrogen 80%
Oxygen 16%
Carbon dioxide 4%

Question 11

Breathing may stop due to disease or injury. Mechanical ventilators can be used in these cases. Explain the 2 types

Answer 11

Positive pressure ventilators:
Forces the right amount of air into the lungs

Negative pressure ventilators:
Draws air into the lungs

Question 12

Explain aerobic respiration

Answer 12

Glucose + oxygen —> carbon dioxide + water + energy
C6H12O6 + 6O2 —> 6CO2 + 6H2O
- takes place continuously in both plants and animals
- takes place in the mitochondria of cells

Question 13

Uses of energy produced through aerobic respiration

Answer 13

• to build larger molecules from smaller ones
• in animals, to enable muscle contraction
• in mammals and birds, to maintain steady body temperature in colder surroundings
• in plants to build up sugars, nitrates, and other nutrients into amino acids which are then built into proteins

Question 14

During exercise, the human body has a higher demand for energy, what are changes that take place in the body?

Answer 14

• heart rate increases, increasing blood flow to muscles
• rate and depth of breathing increases to provide more oxygen to blood and more carbon dioxide is lost
• glycogen stored in the muscles convert back into glucose

Question 15

Describe anaerobic respiration

Answer 15

• when the body has an insufficient amount of oxygen, energy is transferred by aerobic respiration

Glucose —> lactic acid
C6H12O6 —> 2C3H6O3

• anaerobic respiration in the muscles, is the incomplete breakdown of glucose.
  This can cause a build up of lactic acid.
• an oxygen debt needs to be repaid to oxidise the lactic acid into carbon dioxide and water
• as the breakdown of glucose is incomplete, much less energy is transferred in anaerobic respiration than aerobic
• lactic acid build up can cause muscle fatigue

Anaerobic respiration in plants and microorganisms:
Glucose —> ethanol + carbon dioxide
C6H12O6 —> 2C2H5OH + 2CO2