Module 3 Exchange And Transport

Question 1

Features of an efficient exchange surface.

Answer 1

• Increased surface area - root hair cell.
• Thin layer - alveoli.
• Good blood supply/ventilation to maintain gradient - gills/alveolus.

Question 2

Functions of cartilage.

Answer 2

• Increases the bone tensile strength.
• Provides support in bony areas where flexibility is required.

Question 3

Structure of cartilage.

Answer 3

A type of smooth elastic tissue that provides structural support to the body E.g. joints, nose, ears, trachea, ribs.

Question 4

Structures of Ciliated epithelium.

Answer 4

Strong and flexible connective tissue that allows the trachea to remain open at all times.

Question 5

Functions of cartilage.

Answer 5

The open cartilage facing towards the oesophagus, allowing it to expand to accommodate masses of food moving through it.

Question 6

Functions of Ciliated epithelial cells.

Answer 6

Beat/waft mucus up towards the throat, which traps pathogens and is swallowed by stomach where pathogens are digested.

Question 7

Functions of goblet cells.

Answer 7

Secreted mucus which traps pathogens.

Question 8

Structure of bronchioles.

Answer 8

• In lungs bronchi divide to form many small bronchioles.
• Smaller bronchioles (diameter 1mm or less), no cartilage.
• Walls contain smooth muscles that contracts and construct.
• Lined with thin layer of flattened epithelium making gas exchange possible.

Question 9

Function of bronchioles.

Answer 9

• Carry air to alveoli.
  When relaxed, bronchioles dilate.

Question 10

Function of surfactants.

Answer 10

• Reduced surface tension and allow the alveoli to retain its shape.

Question 11

Structure of trachea.

Answer 11

• Supported by incomplete rings of strong, flexible cartilage.
• Contains smooth muscle and elastic fibres.
  Contains Ciliated epithelium and goblet cells.

Question 12

Function of trachea.

Answer 12

• The main airway carrying clean, warm, moist air down from the nose an into the chest.
• Cartilage rings are incomplete to food can move easily down the oesophagus.

Question 13

Structure of alveoli.

Answer 13

• Diameter around 200-300mm.
• Unique to mammalian lungs.
• Consists of layer of thin, flattened epithelial cells with some collagen and elastic fibres.

Question 14

Function of alveoli.

Answer 14

• Where the exchange of oxygen and carbon dioxide takes place.
• Elastic tissues allow alveoli to stretch and retract, this is known as the elastic recoil of the lungs.

Question 15

Function of rib cage.

Answer 15

• Protects the organs in the thoracic cavity, assists in respiration and provides support for the upper extremities.

Question 16

Function of diaphragm / intercostal muscles. (Breathing in)

Answer 16

1. As the diaphragm contracts it flattens and moves down.
2. The external intercostal muscles contract and lifts the ribs upwards and outwards.
3. This results in an increase in volume of the thorax causes a decrease in air pressure and fresh air is drawn into the lungs.

Question 17

Function of diaphragm / intercostal muscles. (Breathing out)

Answer 17

1. The diaphragm relaxes and moves upwards.
2. The intercostal muscles relax and the rib cage drops downwards and inwards.
3. This results in a decrease in volume of the thorax and the air in the lungs is pushed out.

Question 18

Vital capacity.

Answer 18

The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath.

Question 19

Tidal volume.

Answer 19

The volume of air that moves into and out of the lungs with each resting breath. It is around 500cm^3 in most adults at rest, which uses about 15% of the vital capacity of the lungs.

Question 20

Residual volume.

Answer 20

The volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly.

Question 21

Total lung capacity.

Answer 21

The sum of the vital capacity and the residual volume.

Question 22

What is a single circulatory system?

Answer 22

A single circulatory system, the blood flows through the heart where it is pumped through the respiratory system and to the rest of the body where it is then returned to the heart.

Question 23

What is a double circulatory system?

Answer 23

A double circulatory system, the heart pumps the blood to the lungs to be oxygenated where it is then returned to the heart. The oxygenated blood is then pumped by the heart to the rest of the body.

Question 24

Why does blood typically travel at lower pressure in a single circulatory system than in a double circulatory system?

Answer 24

The blood travels at lower pressure in a single circulatory system because it is only pumped through the heart once per circulation. However, the blood travels at a higher pressure in a double circulatory system because it is pumped through the heart twice per circulation.

Question 25

Structure and function of an artery.

Answer 25

Tunica externa:
Collagen - prevents bursting.

Tunica media:
Elastic fibres - withstand force.
Smooth muscle - contracts to so strict.

Tunica interna:
Endothelium - carries blood away from heart, usually oxygenated except pulmonary artery.

Lumen:
Narrow - maintain high pressure.

Question 26

Structure and function of a vein.

Answer 26

Tunica externa:
Tough outer layer - giver structure and shape to the vein.

Tunica media:
Thin muscle wall - low pressure.
Little elastin - low pressure.

Tunica interna:
Endothelium - carry blood towards the heart, usually carry deoxygenated blood except pulmonary veins.

Lumen - maintain low pressure.

Question 27

Structure and function of a capillary.

Answer 27

Endothelium - one cell thick.
Adapted for efficient diffusion
Substance can diffuse into and out of cells into the capillaries.

Question 28

What is tissue fluid and how is it formed?

Answer 28

Plasma, along with the substances dissolved into it (except large plasma proteins), can move in and out of capillaries through tiny pores).

Hydrostatic pressure inside the vessels (resulting from contractions in the heart). This acts to push plasma and solutes out of the capillary. The fluid leaves the capillary is referred to as tissue fluid. It flows around the tissues, where diffusion takes place.

Question 29

How is tissue fluid formed? (Arterial end).

Answer 29

At the arterial end of the capillary:
- Hydrostatic pressure (created by the heart contracting) is greater than the oncotic pressure (the attraction of water, by osmosis, that results from plasma proteins).

• Therefore water leaves the capillaries through small gaps in the capillary wall.
• Tissue fluid circulates around the cells and exchange takes place.

Question 30

How is tissue fluid formed? (Venous end).

Answer 30

At the venous end of the capillary:
- The oncotic pressure is now greater than the hydrostatic pressure.
Fluid moves back into the capillaries, carrying waste products.

Question 31

What is lymph and how is it formed?

Answer 31

What is Lymph?
• 10% of liquid that leaves the blood vessels drains into the lymphatic system.

• This liquid is called lymph.

• Lymph is similar to plasma and tissue fluid, however it has less oxygen and fewer nutrients.

• Lymph travels through lymph capillaries. These join to form the larger vessels.

• Fluid travels through the squeezchy of body muscles.

• Lymph capillaries have one way valves to stop the back flow of lymph (like blood).

• Along the lymph vessels there are lymph nodes. Lymphocytes build up in the lymph nodes when necessary and produce antibodies which are then pushed into the blood.

• Lymph nodes intercept bacteria and other derbies from the lymph.

• The lymphatic system plays a major role in the defence mechanisms of the body.

Question 32

What is the need for transport systems in multicellular plants?

Answer 32

Larger organisms require specialised mass transport systems, increasing transport distances, increased transport speed.

Question 33

Rate of transpiration formula.

Answer 33

TT x r^2 x h
——————
Time taken

r = half
Pi = 3.142
r = radius of the capillary tube.
h = distance travelled by air bubble.

Question 34

How does water transport through the plant and to the air surrounding the leaves?

Answer 34

The transpiration stream.
- An uninterrupted stream of water and solutes which is takes up by the roots and transported via the xylem to the leaves where it evaporates into the air as water vapour through the leaves pores.

Question 35

What adaptations do plants have to the availability of water around them.

Answer 35

Closing stomata - When the stomata is closed, photosynthesis will decrease because no CO2 can enter through the closed stomata. Less photosyntheses means less energy is produced by the plant and the plant stops growing.

Waxy cuticles - act as a barrier to evaporation. Shiny surface also reflects her and so lowers temperature.

• Hairy leaves - minimises water loss by reducing air flow and creating a humid microclimate which reduces evaporation and the water potential gradient.
• Curled leaves - minimises water loss with no air flow creating a humid microclimate reducing evaporation and water potential gradient.

Question 36

What is translocation?

Answer 36

The movement of assimilates within phloem sieve tubes from source to sink.

Question 37

What are sources?

Answer 37

The site where sucrose/assimilates are made and loaded into the phloem (high concentration). E,g, green leaves, green stems, roots.

Question 38

What are sinks?

Answer 38

The site where sucrose/assimilates are unloaded from the phloem for use or storage. E.g. meristems, roots, fruits, seeds.

Question 39

What is a symplast pathway?

Answer 39

Symplastic pathway (through the cytoplasm and plasmodesmata) which is a passive process as the sucrose molecules move by diffusion.

Question 40

What is apoplast pathway?

Answer 40

Apoplastic pathway (through the cell walls) which is an active process.

Question 41

Explain the process of active loading sucrose into the phloem at the source.

Answer 41

1. Hydrogen ions (H+) are actively pumped out of the cytoplasm of companion cells via a proton pumps into their cell walls (involves the hydrolysis of ATP – active process).
2. This increases the hydrogen ion concentration in the cell walls of the companion cells compared to the inside. Creating a concentration gradient.
3. Hydrogen ions, re-enter the cytoplasm of the companion cell, down their concentration gradient via a cotransporter protein.
4. While transporting the hydrogen ions this co-transporter protein also carries sucrose molecules (at a different binding site) into the companion cell against the concentration gradient for sucrose (by facilitated diffusion).
5. The sucrose molecules then diffuse into the phloem sieve tubes via the plasmodesmata from the companion cells.

Question 42

Explain the process of active unloading of sucrose/assimilates at the sink.

Answer 42

1. At the sink end, solutes are removed from the phloem to be used up.
2. This increases the water potential inside the sieve tubes, so water also leaves the tubes by osmosis.
3. This lowers the pressure inside the sieve tubes.
4. This result is a pressure gradient from the source end to the sink end.
5. This gradient pushes solutes along the side tubes to where they’re needed.