Transport In Animals And Plants

Question 1

Explain how a valve in a vein stops the back flow of blood.

Answer 1

Blood tries to flow back.

Fills pockets which forces the valve to close.

Question 2

Veins located in the head of a human don’t have valves. Suggest a reason for this lack of valves.

Answer 2

There is no backflow as the veins are located above the heart.
Blood moves by gravity.

Question 3

Explain how blood is forced towards the heart in veins found in the legs.

Answer 3

Veins lie next to muscle.
When muscle contracts the vein is squeezed.
This forces the blood towards the heart.

Question 4

Explain how red blood cells are adapted to carry out it’s function.

Answer 4

No nucleus, allows more space for haemoglobin.
Oxygen combines with haemoglobin to form oxyhaemoglobin.
RBC have large SA due to biconcave shape.
Has a flexible membrane, allowing greater contact with capillary walls.

Question 5

State one function of red blood cells.

Answer 5

To transport oxygen from the lungs to respiring tissues.

Question 6

Describe what is meant by a double circulatory system in a mammal and describe two advantages of such a system.

Answer 6

Separate circulation for body and lungs.
Blood passes through heart twice in one circuit.
Separates oxygenated and deoxygenated blood.
Maintains high bp and greater O2 concentration to the tissues.
Lower pressure for pulmonary circulation.

Question 7

Describe the functions of capillaries.

Answer 7

Site of exchange.
Removes waste products between blood and tissues.
Tissue fluid formation, slows blood flow to allow time for diffusion.
Reduces bp/carries blood at low pressure.

Question 8

State three differences between an artery and the vein.

Answer 8

Arteries-small lumen, thick muscle wall, regular shape.

Veins-wider lumen, thin muscle wall, irregular shape.

Question 9

Explain the differences in pressure between the left atrium, left ventricle and right ventricle.

Answer 9

The thickness of the muscular wall affects the pressure.
The LA forces blood into the ventricle which is close to it.
The LV has to push blood around the entire body which is further.
The RV has to push blood to the lungs which are closer and need lower bp.

Question 10

What is the advantage of the S-shaped curve shown by haemoglobin in the tissues?

Answer 10

As partial pressure of oxygen going into the tissues decreases, more oxygen is dissociated.

Question 11

What is the advantage of the S-shaped curve shown by haemoglobin in the lungs?

Answer 11

The haemoglobin is fully saturated at relatively low partial pressures of oxygen.

Question 12

What would be the effect on the human haemoglobin curve line if the carbon dioxide concentration increased?

Answer 12

The haemoglobin curve would move to the right.

Question 13

What is the name of the effect when the oxygen dissociation curve shifts to the right?

Answer 13

Bohr effect.

Question 14

A lugworm has a curve to the left of the human haemoglobin. What is the advantage of this to the lugworm?

Answer 14

A curve to the left means that the haemoglobin ha a greater affinity for oxygen at lower partial pressures and reaches saturation at lower partial pressures of oxygen.

Question 15

What does it suggest about the conditions under which the lugworm lives if the curve is toward the left of a human haemoglobin curve?

Answer 15

It lives under low oxygen conditions.

Question 16

How does the pressure in the atria compare to the pressure in the ventricles during atriol systole?

Answer 16

Pressure is greater in the atria/lower in ventricles.

Atrio-ventricular valves are open.

Question 17

Explain the importance of the slight delay at the AVN.

Answer 17

The delay allows blood to pass into the ventricles from the atria.
Before the ventricles contract(preventing the ventricles contracting before the atria are empty).

Question 18

Explain the importance of the electrical activity being passed to the base of the ventricles.

Answer 18

So that the ventricles contract from the base upwards.

So more blood is forced out/ventricles empty completely.

Question 19

Give the function of a xylem vessel.

Answer 19

Transport water and minerals.

Question 20

Give the function of a sieve tube.

Answer 20

Transport products of photosynthesis eg sucrose.

Question 21

Give the function of a companion cell.

Answer 21

Carries out respiration to synthesise ATP for active processes in the sieve tube.

Question 22

Explain the function of lignin in the cell wall of the xylem vessel.

Answer 22

Supports/strengthens the vessel preventing it from collapsing.
Aids movement of water upwards by adhesion of water molecules.

Question 23

Explain what is meant by cohesion.

Answer 23

The strong attraction that water molecules exert on one another.

Question 24

Explain how tension is generated in the xylem vessel.

Answer 24

Water molecules evaporating through the stomata at the top of the column are replaced from below.
Because of cohesion this creates an upward force(tension) throughout the whole column.

Question 25

What additional force helps to support water molecules in the xylem against the force of gravity?

Answer 25

Adhesion between the water molecules and the xylem wall.

Question 26

An additional small force operates throughout any 24-hr period, and influences the upward movement of water. Name this force.

Answer 26

Root pressure.

Question 27

How is the force of root pressure generated?

Answer 27

Active transport of ions into the xylem of the root.
Creates an osmotic gradient.
Water is drawn in at the base of the xylem.

Question 28

State the name given to the types of plants that live in hot, dry environments.

Answer 28

Xerophyte.

Question 29

State 3 features of the leaf that enable the plant to live in hot, dry conditions and explain how each of the features helps the plant to live in it’s environment.

Answer 29

Sunken stomata-water vapour held above stomata(reduces water loss).
Hairs surrounding stomata-helps to retain water vapour.
Thick cuticle-reduces water loss.

Question 30

What type of plant is Nymphaea?

Answer 30

Hydrophyte.

Question 31

State 3 adaptations of plants such as Nymphaea for living in an aquatic environment and state why each is important.

Answer 31

Large air spaces-for buoyancy/diffusion.
Stomata on upper surface-to allow gas exchange with the air.
Thin cuticle-as little water vapour loss.
Little support tissue-buoyed by water.

Question 32

State the name of the substance in which 14C will be transported in the stem.

Answer 32

Sucrose.

Question 33

Explain how the results of the experiment demonstrate that bi-directional flow occurs in the stem.

Answer 33

The 14Cis taken into the leaf half way up the stem and appears at the top and in the roots.

Question 34

Explain the relatively high value of 14C found at the top of the stem.

Answer 34

The top of the stem is the growing point where carbohydrate is needed.
To provide ATP for respiration.

Question 35

State the general name given to areas where unloading of carbohydrate occurs.

Answer 35

Sink.

Question 36

Plants have two distinct transport systems. Describe how the structure of each is adapted to it’s functions.

Answer 36

Xylem transports water and minerals from roots to leaves.
Phloem transports sucrose and amino acids from source to sink(leaves to other parts of the plant).
Xylem is made of vessels and tracheids.
During development xylem vessels lose their end walls and form continuous tubes.
Their wall is lignified to strengthen.
Mature xylem vessels are dead.
Phloem made of sieve tubes and companion cells.
The sieve tubes lose most of their organelles but remain alive.
They have perforated sieve plates that low solutes to pass through.
Sucrose flow in both directions.
Companion cells contain mitochondria and provide ATP for sieve tubes.
Flow of water up the xylem by cohesion tension theory and capillarity.