6.4 and D.6 Gas Exchange

Question 1

All organisms absorb one gas from the environment and release another through diffusion =

Answer 1

gas exchange

Question 2

Humans absorb oxygen and transport it to all living cells =

Answer 2

cell respiration

Question 3

Flow of air in and out of the gas exchange surface, to replace air/water, helps to maintain concentration gradients =

Answer 3

ventilation

Question 4

Is breathing the same as respiration? True or False

Answer 4

Flase

Question 5

The ventilation system maintains a ___________ ______________ ____________ between the alveoli and the blood

Answer 5

large concentration gradient

Question 6

What does the body need to get rid of carbon dioxide?

Answer 6

The body requires oxygen to make ATP (cell respiration) to get rid of carbon dioxide.

Question 7

What concentrations of oxygen and carbon dioxide in the alveoli are required to diffuse from alveoli into the blood?

Answer 7

high concentration of oxygen, low concentration of carbon dioxide

Question 8

What are the two stages of ventilation?

Answer 8

1. Inspiration (inhalation)
2. Expiration (exhalation)

Question 9

What is the mechanism of ventilation based on?

Answer 9

The mechanism of ventilation is based on the inverse relationship between pressure and volume as an increase in volume leads to a decrease in pressure.

Question 10

How are alveoli well adapted to gas exchange?

Answer 10

1. Alveoli increase the surface area for gas exchange
   - They are millions in number each with their own network of capillaries
2. Membranes are very thin for both the alveoli and the capillaries which means the diffusion path is short
3. The surfaces are wet which means gases are dissolved which makes diffusion easier.

Question 11

What are type I pneumocytes

Answer 11

Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange

Question 12

What are the properties of a Type I pneumocyte cell?

Answer 12

• They are flattened cells
• Cover 70% of the internal surface of each alveolus
• Extremely thin (short diffusion distance)
• Permeable
• A single layer of cells form the walls of an alveolus

Question 13

What is the function of Type II pneumocytes?

Answer 13

Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension.

Question 14

What are the properties of a Type II pneumocyte cell?

Answer 14

• Secrete fluid to moisten the inner surface of the alveolus
• Fluid aids diffusion of gases
• Fluid contains surfactant to prevent the walls sticking together - maintains the lumen
• Can divide to form Type I pneumocytes (this is done to repair damage)

Question 15

How many membranes must an oxygen molecule pass through in order to enter an erythrocyte?

Answer 15

5, it passes through two membranes each on its way through the alveoli and capillaries and there is also one more membrane to pass through in the red blood cell.

Question 16

What is a tumour?

Answer 16

Tumours are abnormal growth of tissue that develop at any stage of life in any part of the body.

Question 17

What is cancer?

Answer 17

A cancer is a malignant tumour and it named after the part of the body where cancer first develops.

Question 18

What factors increase lung cancer risk?

Answer 18

Air pollution, exposure to a radon (radioactive) gas, previous lung disease, family history, past cancer treatment, lowered immunity, previous smoking related cancers, smoking

Question 19

What are symptoms of lung cancer?

Answer 19

Short of breath, Having a cough, Coughing up phlegm with blood, an ache or pain in the chest or shoulder, loss of appetite, fatigue, weight loss

Question 20

What is emphysema?

Answer 20

Emphysema is a type of lung disease that causes breathlessness.

Question 21

What is the main cause of emphysema?

Answer 21

The main cause of Emphysema is smoking.

Question 22

Is Emphysema curable?

Answer 22

No, but there are treatments

Question 23

What are symptoms of Emphysema?

Answer 23

Difficulty breathing, cough, loss of appetite, weight loss

Question 24

How does Emphysema work?

Answer 24

Protease is released by leukocytes (white blood cells) and inflamed lung tissue. This protease then breaks down the connective tissue of the lungs and this results in the destruction of small airways and alveoli. This results in the formation of large air pockets and the breakdown of capillaries. Consequently the large air pockets have a much lower surface area to volume ratio than the alveoli which causes insufficient ventilation. This combined with the reduced blood supply results in insufficient gas exchange and low blood oxygen levels.

Question 25

What are the consequences of emphysema?

Answer 25

- Damage to the alveoli is caused by emphysema which is irreversible - Causes low oxygen blood levels - Lack of energy - Shortness of breath

Question 26

What is a Haemoglobin?

Answer 26

A protein molecule found within erythrocytes (RBCs). Responsible for carrying oxygen in bloodstream.

Question 27

What is each Haemoglobin molecule capable of binding to?

Answer 27

4 oxygen molecules and one carbon dioxide molecule

Question 28

How does Haemoglobin change shape when carrying oxygen and what is the effect of this?

Answer 28

When oxygen binds to haemoglobin, haemoglobin has up to 4 different shapes, depending on how many oxygen's are bound. Therefore 4 oxygen molecules can bind to one haemoglobin. These shapes affect haemoglobin's affinity for oxygen. The greater the tendency to bond, the higher the affinity. This means haemoglobin will have a higher affinity for O2 in oxygen-rich areas (like the lung), promoting oxygen loading Conversely, haemoglobin will have a lower affinity for O2 in oxygen-starved areas (like muscles), promoting oxygen unloading

Question 29

What is partial pressure?

Answer 29

The mixture of gases has a total pressure that is exerted. The portion of the total pressure that is due to oxygen alone is the partial pressure of oxygen.

Question 30

What does the oxygen saturation curve describe?

Answer 30

The saturation of haemoglobin by oxygen at different partial pressures of oxygen.

Question 31

What are the axes of an oxygen dissociation curve?

Answer 31

X-axis = partial pressure of oxygen. Y-axis = % saturation of haemoglobin with oxygen.

Question 32

What does high and low saturation on the oxygen dissociation curve indicate?

Answer 32

High - lungs Low - tissues

Question 33

Compare Haemoglobin and myoglobin

Answer 33

- Both are oxygen binding proteins - Myoglobin is found in the muscles and stores oxygen in muscle tissue, delaying the onset of lactic acid fermentation - Haemoglobin takes oxygen from lungs to the tissues - Haemoglobin has a quaternary structure - Myoglobin has a tertiary structure etc.

Question 34

What are myoglobin?

Answer 34

Myoglobin is used to store oxygen in muscle tissues and release it when needed in respiration. Myoglobin gives muscle tissue its red colour. It increases the efficiency of respiration in the muscle tissues as it is more sensitive to changes in partial pressure of oxygen. It releases oxygen into the tissues rapidly as they use it in respiration.

Question 35

Adult haemoglobin vs fetal haemoglobin

Answer 35

Fetal haemoglobin has different molecular composition to adult haemoglobin. Fetal haemoglobin must have a greater affinity for oxygen at all partial pressures. This ensures that oxygen is transferred to the fetus from the maternal blood across the placenta. In placental capillaries, adult haemoglobin dissociates with oxygen, fetal haemoglobin binds to that same oxygen. Fetal haemoglobin dissociates this oxygen only when it reaches tissues of fetus. The curve for fetal hemoglobin is consistently to the left of adult haemoglobin. Adult binds less oxygen at the same partial pressure to fetal haemoglobin.

Question 36

Explain carbon dioxide transport in the blood

Answer 36

Cell respiration waste = carbon dioxide. Carbon dioxide diffuses into bloodstream. 3 ways carbon dioxide is transported to lungs. 1. Carbon dioxide gas dissolved in blood plasma. 2. Carbon dioxide bound to haemoglobin (1 carbon dioxide per haemoglobin – the basis of the Bohr shift). 3. As hydrogen carbonate ions dissolved in blood plasma. Most (70%) of carbon dioxide enters RBCs and converted into hydrogen carbonate ions.

Question 37

How does hydrogen carbonate ions form?

Answer 37

Cytoplasm of RBCs contains enzyme carbonic anhydrase. This enzyme catalyses reaction: carbon dioxide and water → carbonic acid (H2CO3). Carbonic acid then dissociates into a hydrogen carbonate ion and hydrogen ion. (carbonic anhydrase) CO2 + H2O → H2CO3 → HCO3- + H+

Question 38

What happens to the excess hydrogen ions from the formation of hydrogen carbonate ions?

Answer 38

Hydrogen carbonate ions exit cytoplasm of RBC through specialised protein channels in the cell membrane. H+ produced must be removed to prevent pH change in blood. Called pH buffering. Some bind to haemoglobin, others bind to plasma proteins. The hydrogen ions within the erythrocyte make the environment less alkaline, causing haemoglobin to release its oxygen The haemoglobin absorbs the H+ ions and acts as a buffer to maintain the intracellular pH When the red blood cell reaches the lungs, bicarbonate is pumped back into the cell and the entire process is reversed

Question 39

What is the Bohr shift?

Answer 39

Carbon dioxide lowers the pH of the blood (by forming carbonic acid), which causes haemoglobin to release its oxygen This is known as the Bohr effect – a decrease in pH shifts the oxygen dissociation curve to the right

Question 40

What part of the brain controls the ventilating rate?

Answer 40

Under control of area of medulla oblongata of the brainstem, called the breathing centre.

Question 41

Regulation of blood pH

Answer 41

If the blood pH falls below 7.35 the chemoreceptors signal to the respiratory centre to increase the rate of ventilation. Hyperventilation withdraws CO2 from the blood, driving the carbonic acid reaction to the left, raising pH. If the blood becomes too basic, the bicarbonate ions can be secreted into the distal convoluted tubules of the kidney. This pH range is, in part, maintained by plasma proteins which act as buffers

Question 42

What is the effect of high altitude on partial pressure?

Answer 42

Not a change in % oxygen, rather a change in the air pressure, with altitude. At high altitudes, air pressure is lower and hence there is a lower partial pressure of oxygen (less O2 because less air overall) This makes it more difficult for haemoglobin to take up and transport oxygen (lower Hb % saturation) Consequently, respiring tissue will receive less oxygen – leading to symptoms such as fatigue, headaches and rapid pulse

Question 43

What are the symptoms of altitude sickness?

Answer 43

headaches, nasuea, vomiting, dizziness, loss of consciousness, muscle weakness, rapid pulse, breathing rate