Organisms Exchanging Substances

Question 1

Factors affecting gas exchange

Answer 1

Diffusion distance
Surface area
Concentration gradient
Temperature

Question 2

Gas exchange in insects

Answer 2

• Air passes in to the trachea (microscopic air-filled pipes) through pores called spiracles
• The trachea branches into smaller tracheoles which have thin permeable wall allowing oxygen to diffuse directly into respiring cells

Question 3

Small organisms

Answer 3

•large surface area to volume ratio
•more faster heat loss per gram in relation to body size
•faster rate of respiration releases heat

Question 4

Large organisms

Answer 4

•small surface area to volume ratio
•more slower heatloss per gram in relation to body size
•slower rate of respiration

Question 5

Tracheoles

Answer 5

• Highly branched tracheoles
• large number of tracheoles
• filled in ends of tracheoles moves into tissues during exercise
• so larger surface area for gas exchange

Question 6

Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake

Answer 6

1. Large(r) organisms have a small(er) surface area:volume (ratio);
   OR
   Small(er) organisms have a large(r) surface area:volume (ratio);
2. Overcomes long diffusion pathway
   OR
   Faster diffusion;

Question 7

Trachea

Answer 7

• reinforced with spirals of chitin - prevents it from collapsing
• increases the rate of gas exchange

Question 8

Spiracles

Answer 8

•Sphicter - can open and close
•prevents waterloss
•materials can diffuse in and out of

Question 9

tracheal fluid

Answer 9

to increase the movement of gases

Question 10

Insects respire aerobically

Answer 10

•muscles respire anaerobically and produce lactate
•water potential decreases as its soluble
•water in the tracheoles move into cells by osmosis
•reduces the volume of tracheal fluid
•draws air into tracheoles and co2 out
•creates a diffusion gradient

Question 11

Gas exchange in bony fish

Answer 11

Operculum > opercular cavity > gills > gill arch and filaments > gill lameallae

Question 12

counter current exchange

Answer 12

•blood and water moves in opposite directions
•water passing the blood has a high concentration gradient if oxygen
•diffusion gradient maintained throughout the entire lamellae

Question 13

Adaptations of xerophytes

Answer 13

•curled leaves - trap moisture to increase local humidity
•hairs - trap moisture to increase local humidity
•sunken stomata - trap moisture to increase local humidity
•longer roots - network to reach more water
•thicker cuticle- to reduce Evaluation

Question 14

Short diffusion pathway

Answer 14

•stomata - no cells are to far away from the stomata
•numerous interconnecting airspaces- in the mesphophyll so gass can easily come into contact with the cell
•large SA in mesphophyll - rapid diffusion

Question 15

Describe the process involved in the absorption and transport of digested lipid molecules from the ileum into the lymph vessels (5)

Answer 15

1. Micelles contain bile salts and fatty acids
2. Release fatty acids to the lining of the ileum
   3.fatty acids absorbed by diffusion
3. Triglycerides reformed in cells
4. Vesicles move to the cell membrane

Question 16

Describe the role of micelles in the absorption of fats into the cells lining the ileum. (3)

Answer 16

1. Micelles include bile salts and fatty acids;
2. Make the fatty acids (more) soluble in water;
3. Bring/release/carry fatty acids to cell/lining (of the ileum);
4. Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
5. Fatty acids (absorbed) by diffusion;

Question 17

Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Explain why. (2)

Answer 17

1. More oxygen enters/oxygen enters more quickly
2. So maintains concentration gradient/greater diffusion gradient

Question 18

what can you conclude about how exposure to CO affects the loading and unloading of oxygen by haemoglobin?
Explain your answer. {3}

Answer 18

1. Less oxygen is loaded at high pO2 compared with no CO (this bc CO has a higher affinity for oxygen and binds quicker)
2. So Hb has a higher affinity for oxygen at low pO2
3. Hb has more oxygen at low pO2

Question 19

To be used as passive immunity treatment, the anti-toxin antibody would be injected.
If it was given by mouth, it would be digested.
Describe how the anti-toxin antibody would be digested.

Answer 19

1. Peptide bonds are hydrolysed
2. Endopeptidases break internal peptide bonds
3. Exopeptidase break terminal peptide bonds
4. Dipeptidase break dipeptides to amino acids

Question 20

Explain why the damage to the cells lining the ileum reduces absorption of the products of digestion and why this reduces absorption of water. {3}

Answer 20

1. Reduces surface area
2. Decreases water potential gradient in the lumen (as protiens are large remain in the lumen due to fewer co transport)
3. So water moves out of cells into the lumen by osmosis

Question 21

Chitin keeps the trachee open in the tracheal system of gas exchange in an insect.
Gas exchange does not occur in the tracheae.
Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect. {2}

Answer 21

1. Tracheoles are highly branched
2. So short diffusion pathway (or) large surface area for rapid diffusion
3. Tracheole walls are one cell thick
4. Rapid diffusion into cells (or) short diffusion pathway

Question 22

Describe how proteins are digested in the human gut.

Answer 22

1. Hydrolysis of peptide bonds;
2. Endopeptidases break polypeptides into smaller peptide chains;
3. Exopeptidases remove terminal amino acids;
4. Dipeptidases hydrolyse / break down dipeptides into amino acids;

Question 23

Describe how proteins are digested in the human gut.

Answer 23

1. Hydrolysis of peptide bonds;
2. Endopeptidases break polypeptides into smaller peptide chains;
3. Exopeptidases remove terminal amino acids;
4. Dipeptidases hydrolyse / break down dipeptides into amino acids;