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Biology > 9. Exchange in Animals > Flashcards

9. Exchange in Animals Flashcards

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1
Q

What do animals need exchange surfaces for?

A

To supply oxygen and nutrients to survive

Remove waste products so they don’t build up and become toxic.

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2
Q

What are the 3 main factors that affect the need for an exchange system?

A

The size of the organism
Surface area to volume ratio
Level of activity

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3
Q

How does size affect the need for a transport system?

A

In very small organisms, all the cytoplasm is very close to the environment in which they live.
Diffusion is enough to supply oxygen and nutrients.
However, in larger organisms, the diffusion distance is too large and diffusion takes too long to enable sufficient supply to the innermost cells.

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4
Q

How does surface area to volume ratio affect the need for a transport system?

A

Small organisms have a large surface area to volume ratio while larger organisms have a small surface area to volume ratio so need a range of tissues to give the body the ability to exchange substances.

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5
Q

How does the level of activity affect the need for a transport system?

A

The cells of an active organism need a good supply of nutrients and oxygen to supply energy for movement.
This needs energy is increased in those animals that need to keep themselves warm.

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6
Q

What does the gaseous exchange system in mammals consist of?

A

The lungs and associated airways that carry air into and out of the lungs.
Air passes into the lungs through the nose, along the trachea, bronchi and bronchioles and reaches the alveoli.

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7
Q

Which factors allow gaseous exchange to take place?

A

Large surface area
The barrier to exchange is permeable to oxygen and carbon dioxide
Thin barrier reduces diffusion distance (each one cell thick)
Good blood supply maintains a steep concentration gradient of oxygen
Ventilation maintains a steep concentration gradient of CO2.

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8
Q

How does gaseous exchange take place in the lungs?

A

Gases pass by diffusion through the thin walls of the alveoli.
Oxygen passes from the air in the alveoli to the blood in the capillaries.
CO2 passes from the blood to the air in the alveoli.
The lungs maintain a steep concentration gradient in each direction in order to ensure that diffusion can continue.

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9
Q

How is diffusion distance reduced between the alveolus and capillaries?

A

Both the alveolus and capillary wall is one cell thick and consist of squamous (flattened) cells, the capillaries lumen is so thin that the red blood cells are pushed against the wall, reducing diffusion distance.

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10
Q

How is a good supply maintained to keep a steep concentration gradient?

A

The blood system transports CO2 from the tissues to the lungs. This ensures that the concentration of CO2 in the blood is higher than in the air of the alveoli, so CO2 diffuses into the alveoli.
The blood also transports O2 in the blood away from the lungs. This ensures that the concentration of O2 in the blood is lower than in the alveoli, so O2 diffuses into the blood.

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11
Q

How does ventilation increase the rate of gaseous exchange in the lungs?

A

As a result of ventilation (breathing) oxygen is brought into the lungs and carbon dioxide is removed.
This maintains the concentration gradient of CO2 and O2 between the alveolus and capillaries.

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12
Q

What is the structure of the alveoli?

A

They are comprised of squamous epithelium and are surrounded by blood capillaries.

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13
Q

What is a single circulatory system?

A

Fish have a single circulatory system.
The blood flows through the heart once for each circuit of the body.
Heart- Gills- Body- Heart

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14
Q

What is a double circulatory system?

A

Mammals have a double circulatory system.
It has two separate circuits.
The pulmonary circuit carries blood to the lungs to pick up oxygen.
The systemic circuit carries the oxygen and nutrients around the body and tissues.
The blood travels through the heart twice on each circuit.
heart- body- heart- lungs- heart

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15
Q

What are the properties of single circulatory systems?

A

Blood has a low pressure so does not flow very quickly.

The rate at which oxygen and nutrients is delivered and carbon dioxide and urea are removed, is limited.

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16
Q

What are the properties of double circulatory systems?

A

The blood pressure must not be too high otherwise it may damage the delicate capillaries in the lungs.
The heart can increase the pressure of the blood after it has passed through the lungs so it can flow more quickly.
The systemic circulation carries blood at a higher pressure than the pulmonary circulation.

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17
Q

What is an open circulatory system?

A

It means that blood is not always held within blood vessels. Instead, it circulates through the body cavity.

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18
Q

What are the disadvantages of open circulatory systems?

A

Blood pressure is low and blood flow is slow.

Circulation can be affected by body movements or lack of body movements.

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19
Q

What are closed circulatory systems?

A

A system where the blood stays entirely inside vessels.

A separate fluid, called tissue fluid bathes the tissues and cells.

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20
Q

What are the advantages of closed circulatory systems?

A

Higher pressure so blood flows more quickly.
More rapid delivery of oxygen and nutrients.
More rapid removal of carbon dioxide and other wastes.
Transport is independent of body movements.

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21
Q

What is the endothelium?

A

A thin layer made of a single layer of cells on the inner lining of all blood vessles.
It is particularly smooth in order to reduce friction with the flowing blood.

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22
Q

What is the function of arteries?

A

They carry blood away from the heart.

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23
Q

How is the structure of arteries adapted to their function?

A

Inner layer consists of a thin layer of elastic tissue which allows the wall to stretch and recoil to maintain pressure.
Middle layer consists of a thick layer of smooth muscle.
Outer layer is a relatively thick layer of collagen and elastic tissue. Provides strength to maintain withstand pressure.

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24
Q

What is the function of arterioles?

A

Small vessels that distribute the blood from the arteries to capillaries.

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25
Q

How is the structure of arterioles adapted to their function?

A

Walls contain a layer of smooth muscle which contracts to constrict the diameter of the arteriole.
This can divert the flow of blood to regions of the body that are demanding more oxygen.

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26
Q

What is the function of capillaries?

A

They allow the exchange of materials between the blood and the tissue fluid.

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27
Q

How is the structure of capillaries adapted to their function?

A

The lumen is very narrow so red blood cell which reduces diffusion distance and blood flow.
The wall consists of a single layer of flattened endothelial cells which reduces diffusion distance.

28
Q

What is the function of veins?

A

To carry blood back to the heart.

29
Q

How is the structure of veins adapted to their function?

A

The lumen is large, allowing ease of blood flow.
The walls have thinner layers of collagen, smooth muscle and elastic tissue as blood is at a low pressure.
They contain valves to prevent blood flowing the opposite direction.

30
Q

What does blood consist of?

A

A liquid called plasma, red blood cells (erythrocytes), white blood cells (leucocytes), platelets, dissolved oxygen, minerals, glucose, amino acids and carbon dioxide.

31
Q

What is tissue fluid?

A

It is formed by blood plasma leaking from the capillaries by mass flow.
It surrounds the cells in the tissue and supplies them with oxygen and nutrients.

32
Q

How do substances in the blood travel into the tissue fluid?

A

There is a high hydrostatic pressure at the arterial end of a capillary.
This allows nutrients and oxygen to diffuse out of the capillaries into the tissue fluid.

33
Q

How do substances from the tissue fluid return to the blood?

A

There is a low hydrostatic pressure at the venule end which allows tissue fluid to return to the capillaries.
It carries carbon dioxide and other waste substances.

34
Q

What is the lymphatic system?

A

It drains excess tissue fluid out of the tissue and returns it to the blood.

35
Q

What is the structure of the heart?

A

There are two main pumping chambers, the ventricles and above them, the atria which are much smaller.

36
Q

What is the function of the atria?

A

They receive blood from the major veins.
Deoxygenated blood from the body flows through the vena cava into the right atrium.
Oxygenated blood from the lungs flows through the pulmonary vein into the left atrium.

37
Q

Where does blood flow to from the atria?

A

It flows through the atrio-ventricular valves into the ventricles.
Tendinous cords prevent valves from turning inside out.

38
Q

What is the septum?

A

A wall of muscle separating the ventricles

39
Q

What is the function of ventricles?

A

They pump blood away from the heart to the lungs and body.
Deoxygenated blood leaving the right ventricle flows into the pulmonary artery to the lungs to be oxygenated.
Oxygenated blood leaving the left ventricle flows into the aorta to the rest of the body.

40
Q

What are semilunar valves?

A

They are at the base of the arteries, where they leave the heart to prevent the blood re-entering the heart.

41
Q

What is blood pressure like in the atria?

A

The muscle in the atrial walls are thin because they don’t need to create a high blood pressure as they only push blood to the ventricles.

42
Q

What is blood pressure like in the right ventricle?

A

The walls are thicker than the atria but do not need to create a high blood pressure.
They pump deoxygenated blood to the lungs so don’t need to travel very far and high blood pressure can damage the delicate alveoli.

43
Q

What is blood pressure like in the left ventricle?

A

The walls in the left ventricle are very thick as it needs to create sufficient pressure to overcome the resistance of the systemic circulation.

44
Q

What is the structure of cardiac muscle?

A

Consist of fibres that branch, creating cross-bridges.
This ensures the muscle can produce a squeezing action.
Mitochondria provide energy for this.

45
Q

What transports oxygen around the body?

A

It is transported in the red blood cells (erythrocytes) which contain the protein haemoglobin.
When oxygen binds reversibly with haemoglobin, it is called oxyhaemoglobin.

46
Q

What is the structure of haemoglobin?

A

A complex protein with four subunits.
Each subunit consists of a polypeptide chain and a haem (non-protein) group.
The haem group contains a single iron ion which has an affinity for oxygen molecules and can attract and hold them.

47
Q

How many oxygen molecules can one haemoglobin molecule hold?

A

As each haem group can hold one oxygen molecule, each haemoglobin molecule can hold 4 oxygen molecules.

48
Q

How is oxygen concentration measured?

A

It is called the partial pressure of oxygen and is measured in kilopascals (kPa).

49
Q

What is the haemoglobin disassociation curve?

A

Compares how the partial pressure of oxygen effects the saturation of haemoglobin with oxygen.

50
Q

How is fetal haemoglobin different from adult haemoglobin?

A

It has a higher affinity for oxygen.

Therefore, its haemoglobin disassociation curve shifts to the left.

51
Q

What are hydrocarbonate ions and how are they formed?

A

When carbon dioxide combines with water inside the red blood cells to form a weak acid called carbonic acid.
This reaction is catalysed by carbonic anhydrase
The carbonic acid dissociates to release hydrogen and hydrocarbonate ions.

52
Q

What is the chloride shift?

A

When the hydrocarbonate ions diffuse out of the red blood cell into the plasma while chloride ions are moving into the red blood cell which keeps the movement going.

53
Q

What prevents the hydrogen ions building up inside the red blood cells from making the cell acidic?

A

The hydrogen ions are taken out of the solution and associate with haemoglobin to form haemoglobinic acid.

54
Q

What is the bohr effect?

A

It describes the effect that concentration of carbon dioxide has on heamoglobin.
The presence of Carbon Dioxide shifts the haemoglobin dissociation curve to the right.

55
Q

What effect does carbon dioxide have on haemoglobin (the bohr effect)?

A

Carbon dioxide forms carbonic acid in the red blood cells which dissociate to release hydrogen ions and make the cytoplasm more acidic.
This affects the tertiary structure of the haemoglobin and reduces its affinity for oxygen.

56
Q

Explain the haemoglobin dissociation curve.

A

When haemoglobin associates with oxygen it produces an S-shaped curve.
At low partial pressure (at the tissues), haemoglobin does not readily associate with oxygen and is more inclined to disassociate.
As partial pressure rises, a conformation change allows oxygen to associate with the haem groups.
At a high partial pressure (at the lungs) hemoglobin readily associates with oxygen.
As haemoglobin reaches 100% saturation, the curve levels off.

57
Q

Why is the Bohr effect beneficial?

A

Where the tissues are respiring more, more carbon dioxide is produced.
Therefore, more oxygen is released.
This keeps the supply of oxygen high in respiring tissues.

58
Q

What happens during inspiration (inhaling)?

A

Diaphragm contracts to move down.
External intercostal muscles contract to raise the ribs.
Chest cavity volume increases.
The pressure in the chest cavity drops below atmospheric pressure.

59
Q

What happens during expiration (exhaling)?

A

Diaphragm relaxes to move up.
External intercostal muscles relax so the ribs fall.
Chest cavity volume decreases.
The pressure in the chest cavity rises above atmospheric pressure.

60
Q

What is vital capacity?

A

The maximum volume of air that can be moved by the lungs in one breath.

61
Q

What is residual volume?

A

The volume of air that remains in the lungs after an expiration.

62
Q

What is tidal volume?

A

The volume of air moved in and out with each breath, usually at rest.

63
Q

How are gasses exchanged in insects?

A

They do not transport oxygen in the blood.

They have an air-filled tracheal system which supplies directly into respiring tissues.

64
Q

What is the main component of the exoskeleton of insects?

A

Chitin.

65
Q

How does air travel in the tracheal system in insects?

A

It enters through pores called spiracles.
It is transported into the body through tracheae which divide into tracheoles.
At the end of these are filled with tracheal fluid which allows gas exchange with air in the tracheole.

66
Q

How does gas exchange increase in insects?

A

When tissues are active, the tracheal fluid can be withdrawn to increase the surface area of the tracheole wall exposed to air.

Biology (13 decks)

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