Exchange and Transport in Animals

Question 1

Describe the need to transport substances into and out of a range of organisms

Answer 1

During photosynthesis, plants specialize in absorbing carbon dioxide and releasing oxygen. Simultaneously, they absorb nutrients, minerals and water from the soil and air.
Animals utilize systems like the kidney to efficiently eliminate waste, including urea and excessive ions. Proper waste removal is crucial to prevent toxic buildup, as seen with excess urea and carbon dioxide leading to acidosis if not effectively removed.

Question 2

Explain the need for exchange surfaces and a transport in multicellular organisms
Large surface area:

Answer 2

The greater the surface area, the more particles can move through, resulting in a faster rate of diffusion.
Lungs: alveoli has a large surface area – approximately 75m2
Small intestine: millions of villi in the small intestine cells, increase the surface area.
Fish gills: lamellae in gills enhance the surface area.
Leaves: the flattened shape and internal air spaces increase the leaf’s surface area.

Question 3

Explain the need for exchange surfaces and a transport in multicellular organisms
Have a thin membrane:

Answer 3

Provides a short diffusion pathway, allowing the process to occur faster.
Lungs: alveoli and capillary walls are extremely thin.
Small intestine: villi have a single layer of surface cell.

Question 4

Explain the need for exchange surfaces and a transport in multicellular organisms
Having an efficient blood supply:

Answer 4

Creates a steep concentration gradient, so diffusion occurs faster.
Lungs: a continuous exchange of O2 and CO2 occurs between alveoli and capillaries, maintains a steep concentration gradient.
Fish: the one direction flow of water ensures a consistent high oxygen concentration in the water.

Question 5

What is the surface area to volume ratio?

Answer 5

The surface area to volume ratio is a vital assessment of an organisms or cell’ substance transport efficiency.
Calculated by dividing the surface area (length x width) by the volume (length x width x height) and expressed as the smallest whole number in a ratio.
A larger ratio indicates less reliance on specialized exchange surfaces as sufficient diffusion rates fulfil gas exchange needs. For instance, a ratio like 3:1 signifies favourable conditions for effective transport.

Question 6

Explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in the capillaries

Answer 6

Alveoli, small air sacs in the lungs, facilitate gas exchange with blood vessels through thin walls. Key adaptations include their small size and clustered arrangement, maximising the surface area for efficient diffusion. The thin walls of alveoli contribute to faster diffusion, enhancing the efficiency of gas exchange.
Capillaries surrounding alveoli ensure a substantial blood supply, sustaining a steep concentration gradient.

Question 7

Describe the factors affecting diffusion
Surface area:

Answer 7

The greater the surface area, the more space for particles to move through, resulting in a faster rate of diffusion.

Question 8

Describe the factors affecting diffusion
Concentration gradient:

Answer 8

The greater the difference in concentration, the faster the rate of diffusion, as more particles are randomly moving down the gradient than moving against it.

Question 9

Describe the factors affecting diffusion
Diffusion distance:

Answer 9

The smaller the distance, the faster the rate of diffusion as it provides a short diffusion pathway, allowing the process to occur faster.

Question 10

How to calculate the rate of diffusion using Fick’s law?

Answer 10

Rate of diffusion ∝ (Surface area x Concentration difference)/Thickness of membrane
Ficks law: Describes the relationship between rate of diffusion and the variables that may affect it

Question 11

Explain how the structure of red blood cells relates to its function

Answer 11

Red blood cells: transport oxygen from the lungs to all cells in the body. Their biconcave disc shape maximizes surface area. They contain the red pigment haemoglobin, crucial for binding to oxygen and forming oxyhaemoglobin.

Question 12

Explain how the structure of white blood cells relates to its function

Answer 12

White blood cells: vital to the immune system’s defence against pathogens. They have a nucleus and have several types: those producing antibodies against microorganisms, those engulfing and digesting pathogens, and those generating antitoxins to neutralize toxins produced by microorganisms.

Question 13

Explain how the structure of plasma relates to its function

Answer 13

Plasma: a liquid that carries the components in the blood: red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins.

Question 14

Explain how the structure of platelets relates to its function

Answer 14

Platelets: aid in forming blood clots at wound sites, creating scabs that promote new skin growth while preventing microorganisms from entering. They lack a nucleus and their absence would lead to excessive bleeding and bruising in the absence of clotting.

Question 15

Explain how the structure of arteries relate to its function

Answer 15

Arteries carry blood AWAY from the heart.
Layers of muscle in the walls make them strong.
Elastic fibres allow them to stretch.
This helps the vessels withstand the high pressure created by the pumping of the heart.

Question 16

Explain how the structure of veins relate to its function

Answer 16

Viens carry blood TOWARDS the heart.
The lumen (the actual tube in which flows through) is wide to allow the low pressure blood to flow through.
They have valves to ensure the blood flows in the right direction.

Question 17

Explain how the structure of capillaries relate to its function

Answer 17

Capillaries allow the blood to flow very close to cells to enable substances to move between them.
One cell thick walls create a short diffusion pathway.
Permeable walls so substances can move across them.

Question 18

Explain how the structure of the heart and circulatory system is related to its function

Answer 18

o Muscular walls to provide a strong heartbeat.
o The muscular wall of the left ventricle is thicker as blood need to be pumped all around the body rather than just to the lung like the right ventricle.
o 4 chambers that separate the oxygenated blood from the deoxygenated blood.
o Valves to make sure blood does not flow backwards.
o Coronary arteries cover the heart to provide its own oxygenated blood supply.

Question 19

Describe the process of the circulatory system

Answer 19

1. Deoxygenated blood flows through the vena cava into the right atrium.
2. The blood then flows to the right ventricle via the tricuspid valve.
3. The blood then travels to the lungs via the pulmonary artery.
4. In the lungs, this is where the deoxygenated blood becomes oxygenated.
5. This oxygenated blood then travels through the pulmonary vein to the left atria.
6. The blood travels to the left ventricle via the mitral valve.
7. The oxygenated blood travels out the left ventricle to be pumped around the body via the aorta.

Question 20

What is cellular respiration?

Answer 20

Respiration, occurring in every cell, transfers energy from glucose for vital living processes. It is exothermic, as energy is transferred to the environment.
It can take place aerobically (with oxygen) or anaerobically (without oxygen).

Question 21

Describe aerobic respiration

Answer 21

This uses oxygen.
It yields the most energy.
Most of the reactions that make up aerobic respiration occur in the mitochondria.
C6H12O6 + 6O2 → 6CO2 + 6H2O
glucose + oxygen -> carbon dioxide + water

Question 22

Describe anaerobic respiration

Answer 22

Occurs when there is not enough oxygen.
It does not yield as much energy as aerobic respiration.
It is only used as a last resort, for example during a sprint where it is difficult to breath in enough oxygen.
The oxidation of glucose is compete.
In animals:
glucose → lactic acid

In plant and yeast cells it is called fermentation:
Glucose →ethanol + carbon dioxide
This reaction is used to make bread and alcoholic drinks.

Question 23

CORE PRACTICAL - Investigate the Rate of Respiration in living organisms

Answer 23

In this practical, we’ll build a simple respirometer (a machine) to asses how temperature impacts the oxygen consumption of small organisms.
1. Pick a small organism that you would like to measure the rate of respiration of (e.g. maggots or leaves).
2. Place 5m2 of soda lime into a test tube.
3. Place gauze on top and a small amount if the organism being tested on top of this.
4. Attach a three-way tap, capillary tube and syringe to the test tube. Plug the test tube with a stopper.
5. Insert a small amount of coloured liquid into the capillary tube.
6. Turn the 3 way tap to allow air to enter the test tube for 5 minutes. After 5 minutes, close the 3 way tap.
7. Record how far the coloured liquid has moved against a scale.

Question 24

How to calculate the cardiac output?

Answer 24

cardiac output = stroke volume x heart rate
Stroke volume is the volume of blood expelled from the heart in one contraction, whereas heart rate is the number of contractions (beats) per minute.