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Biology AS (OCR) Unit 1 > Module 2 - Exchange and transport. > Flashcards

Module 2 - Exchange and transport. Flashcards

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1
Q

Define an Exchange Surface.

A

An Exchange Surface is a specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other.

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2
Q

Define Gaseous exchange.

A

Gaseous exchange us the movement of gases by diffusion between an organism and its environment across a barrier such as an alveolus wall.

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3
Q

State three ways in which the structure of the lungs allows efficient gas exchange.

A

Large numbers of Alveoli increase the surface area, the wall of each alveolus is very thin, there is a good blood supply.

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4
Q

Why must the diffusion barrier be as thin as possible?

A

Our tissues need a lot of oxygen; the blood must be as close to the air in the alveoli so that the gases can move quickly into and out of the lungs via diffusion. A thin barrier means a shorter diffusion distance.

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5
Q

Describe how a steep diffusion gradient is achieved in the lungs.

A

Ventilation brings a fresh supply of air into the lungs. This carries oxygen into the alveoli and removes carbon dioxide.
Blood flowing into the capillaries carries oxygen away and brings more CO2 . Therefore the concentration of oxygen in the air is higher than that of the blood.

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6
Q

Define Tidal Volume.

A

Tidal Volume is the volume of air that is moved into and out of the lungs with each breath when you are at rest. it is approximately 0.5 dm3. This is where both oxygen and carbon dioxide are at safe levels.

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7
Q

Define Vital Capacity.

A

Vital Capacity is the largest volume of air that can be moved into and out of the lungs in any one breath. This is approximately 5 dm3 but varies between men and women and a persons size and age.

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8
Q

Define Residual Volume.

A

Residual volume is the volume of air that always remains in the lungs even after the biggest possible exhalation. This is approximately 1.5 dm3.

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9
Q

Define Dead Space.

A

Dead Space is the air in the bronchioles bronchi and trachea. There is no gas exchange between this air and the blood.

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10
Q

Define Inspiratory reserve volume.

A

Inspiratory reserve volume is how much more air can be breathed in over and above the normal tidal volume when you take a big breath. You call on this reserve when exercising.

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11
Q

Define Expiratory reserve volume

A

how much more air can be breathed out over and above the amount that is breathed in a tidal volume.

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12
Q

What is the function of Cartilage in the exchange system?

A

Cartilage provides strength to the trachea and bronchus, holds open the airways so there is little resistance to airflow.

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13
Q

What is the function of Smooth muscles in the exchange system?

A

Smooth muscles in the exchange system contracts to the narrow the airways.

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14
Q

What is the function of Goblet cells in the exchange system?

A

Goblet cells secrete mucus. This mucus is sticky and collects particles of dust, dust and bacteria.

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15
Q

What is the function of Elastic fibres in the exchange system?

A

Elastic fibres stretch when breathing in and filling the lungs and recoils when breathing out to help force out air from the lungs.

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16
Q

What is the function of Ciliated cells in the exchange system?

A

Ciliated cells moves mucus up the airways towards the mouth.

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17
Q

What is the function of Squamous epithelium in the exchange system?

A

Squamous epithelium gives a short diffusion pathway for oxygen and carbon dioxide in the alveoli.

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18
Q

Explain why humans have a specialised gas exchange surface, but protoctists do not.

A

Humans have a ver small surface-area-to-volume ratio. The surface area is not large enough to permit enough oxygen to enter by diffusion. Protoctists have a very large surface-area-to-volume ratio and there is sufficient surface for oxygen the need.

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19
Q

How many cell surface membranes must oxygen pass through from the air to the alveolus to the haemoglobin in a red blood cell.

A

Five membranes; two for squamous epithelial cells; two for the endothelial cell of the capillary and one for the red blood cell.

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20
Q

What is tissue fluid?

A

Tissue fluid is a colourless fluid that is formed from blood plasma by pressure filtration through the capillary walls. It surrounds all the cells in the body and all exchanges between blood and cells occur through it.

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21
Q

What is Lymph?

A

Lymph is tissue fluid that has drained into the lymphatic system. It passes through lymph nodes, where it gains white cells and antibodies. Lymphatic vessels absorb hormones from some endocrine glands and fat in small intestine.

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22
Q

What is the Sinoatrial Node?

A

The SAN is known as the heart’s natural pacemaker.

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23
Q

What is the function of the SAN?

A

The SAN sends out electrical impulses to start each heartbeat it is recorded as the P wave in an electrocardiogram.

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24
Q

Mammals have a Double Circulatory system- what is the name of the two circuits?

A

Pulmonary circuit-from the heart to the lungs and back.

Systemic circuit- from the heart to the rest of the body and back.

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25
Q

Name Five features of the Artery.

A

Wall are thick and strong to withstand high blood pressure.
Elastic fibres stretch when blood is pumped into artery.
Elastic fibres recoil to push blood on its way towards capillaries.
Smooth muscle in smaller arteries control diameter to alter blood flow.
Lined by layer of squamous epithelial.

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26
Q

What is the diameter of the lumen of an artery?

A

2mm

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27
Q

Name three features of the Capillary.

A

Wall is made of one layer of endothelial cells, so diffusion distance is short.
Tinny holes in endothelial cells allow water and some solutes to leave the blood.
Very small, so as to have a large surface area for diffusion.

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28
Q

What is the diameter of the lumen of a capillary?

A

8um

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29
Q

List four features of the Vein.

A

Walls are thin, as the blood pressure is low.
Walls distend (stretch)to accomodate large volumes of blood
Veins have semilunar valves to ensure blood travels towards the heart.
Lined by endothelial cells.

30
Q

What is the diameter of the lumen of a vein?

A

10mm

31
Q

State where red blood cells picks up oxygen and where they are likely to be released.

A

Red blood cells pick up oxygen from the lungs. The red blood cells will then transport the oxygen via the blood vessels all around the body. Oxygen is the most likely to be released at respiring tissues.

32
Q

What part of the haemoglobin molecules binds to oxygen.

A

The haem (non protein) group has an affinity (attraction to) oxygen. This means that this part of haemoglobin molecule is responsible for the binding of oxygen molecules in red blood cells.

33
Q

Explain what is meant by the term affinity.

A

Affinity means attraction to for example phosphate head of a phospholipid is said to have an affinity to water.

34
Q

Describe an explain the shape of an adult dissociation curve.

A

The shape of an adult dissociation curve has an s or ‘sigmoid’ shape. This is because more will attach as the p02 in the air, to which the haemoglobin is exposed to, increases. At a low p02 it is hard for oxygen to bind to the haemoglobin. As p02 increases a conformational change takes place and makes it easier until saturation.

35
Q

Explain why Fetal Haemoglobin must have higher affinity than adult haemoglobin.

A

A Foetus is in the womb and therefore isn’t exposed to the outside air. For this reason, it must be able to take oxygen at a low p02 as the maternal haemoglobin as the maternal haemoglobin needs to release it first.

36
Q

List the ways in which carbon dioxide can be transported in the blood.

A

Carbon dioxide is transported in three ways:
5% is transported directly in the plasma.
10% is combined directly with haemoglobin as a compound called carbaminoheamoglobin.
85%is transported as hydrogencarbonate ions.

37
Q

Describe how carbon dioxide is converted into hydrogencarbonate ions.

A

Within an erythrocyte the enzyme known as carbonic anyhydrase causes carbon dioxide and water that is present in the cells to combine and form carbonic acid. This acid will then dissociate into hydrogencarbonate ions and H+ IONS.

38
Q

Explain the need for the chloride shift.

A

The chloride shift neutralises the charge of the red blood cell. This is due to the fact that hydrogencarbonate ions have a negative charge and when they diffuse out of the cell the cell becomes positively charged. The movement of chloride ions into the cell is need to neutralise this charge.

39
Q

Explain how the presence of carbon dioxide can reduce the affinity of haemoglobin for oxygen.

A

The affinity of haemoglobin for oxygen is reduced in the presence of carbon dioxide because as carbonic acid dissociates and hydrogen H+ ions are produced these compete with the oxygen molecules for space. Therefore as more hydrogen ions are produced more oxygen is released from the haemoglobin.

40
Q

What does a dissociation curve show?

A

Dissociation curve show how efficient haemoglobin is at absorbing oxygen in the lungs and delivering oxygen to the tissues.

41
Q

Give three key features of a Red Blood Cell.

A

Biconcave disc shape gives a large surface area for diffusion of oxygen and carbon dioxide.
No organelles, so cytoplasm is full of haemoglobin.
Elastic membrane allows cells to change shape as they squeeze through capillaries and restore shape when they enter veins.

42
Q

What is the diameter of a red blood cell?

A

7um

43
Q

Give three features of a Phagocyte.

A

Phagocytosis-bacteria engulfed in vacuoles digested.
Large number of lysosomes for digestion of bacteria.
Lobed nucleus to help squeeze through gaps between cells in capillary walls.

44
Q

What is the diameter of the Phagocyte.

A

9um

45
Q

Give one feature of a lymphocyte.

A

Some lymphocytes develop into plasma cells that have a large quantity of rough endoplasmic reticulum for fast production of antibodies.

46
Q

Name the two types of valves in relation to the circulatory system.

A

Semilunar valves, and atrioventricular valves.

47
Q

What produces the hydrostatic pressure in the blood?

A

the heart beat creates the hydrostatic pressure of the blood.

48
Q

Name the three stages in the cardiac cycle.

A

Diastole, Atrial systole, and Ventricular systole.

49
Q

Describe and explain what happens during the filling stage of the cardiac cycle.

A

When both the atria and the ventricles are relaxing, the internal volume increases and blood flows into the heart from the major veins. The blood flows into the atria and then down through the atrioventricular valves and into the ventricles. This phase of the cycle is called diastole.

50
Q

What is the specific name given to the left atrioventricular valve?

A

Bicuspid valve.

51
Q

What is the specific name given to the right atrioventricular valve?

A

Tricuspid Valve

52
Q

Explain why the sinoatrial node is called the pacemaker.

A

The sinoatrial node, is often called the pacemaker and this initiates a wave of excitation at regular intervals (55-80 beats per minutes). This coordinates the heart beat.

53
Q

Why is it essential for the wave of excitation sent from the SAN to the AVN to be delayed?

A

This allows the atria to finish contracting and the blood to reach the ventricle before the sub sequential contraction of the ventricles.

54
Q

What is the Purkyne tissue and its function?

A

The Purkyne tissue is a specialised conducting tissue which runs down the inter-ventricular septum and carries the wave of excitation to the AVN.

55
Q

What does wave P show on an electrocardiogram.

A

Wave P show the excitation of the atria.

56
Q

What does the wave QRS indicate of the electrocardiogram?

A

QRS indicates the excitation of the ventricles.

57
Q

What does T show on the electrocardiogram.

A

T shows diastole.

58
Q

What does a deep S wave on an electrocardiogram show?

A

A deep s wave on an electrocardiogram indicates abnormal ventricular hypertrophy.

59
Q

What does ST elevation show on an ECG?

A

ST elevation indicates a heart attack.

60
Q

What does a small unclear P wave suggest on a ECG?

A

A small unclear P wave suggests atrial fibrillation.

61
Q

What substances are moved in the xylem tissue of a plant?

A

Water and soluble minerals travel upwards in xylem tissue

62
Q

What substances are moved in the phloem tissue of a plant

A

Sugars (such as sucrose), travel up or down in phloem tissue.

63
Q

Name the parts of a transverse section of a root in a young plant.

A

From the outside to the inside it is as follows. Epidermis, cortex, endodermis, pericycle, phloem and xylem.

64
Q

Where is the vascular bundle of a young root?

A

The vascular bundle is found at the centre of a young root.

65
Q

What is the role of the endodermis?

A

Endodermis is a special sheath of cells found around the vascular bundle, it has a key role in getting water into xylem vessels.

66
Q

Where are the vascular bundles found in the stem? How is this different to the vascular bundles in a root?

A

Vascular bundles are found near the outer edge of the stem. This is different form that of a root because the vascular bundle is found towards the centre.

67
Q

Where is the xylem found in the stem?

A

The xylem is found towards the centre of each vascular bundle as in that of a young root.

68
Q

What is the layer called that is inbetween that of xylem and phloem tissue?

A

In-between the phloem and xylem there is a layer of cambium. cambium is a layer of meristem cells that divide to produce new xylem and phloem.

69
Q

Where can vascular bundles on a leaf be seen?

A

Vascular bundles form the midrib and veins of a leaf.

70
Q

How can you tell whether a leaf is a dicotyledon.

A

A dicotyledon leaf has a branching network of veins that get smaller as they spread away from the midrib.

71
Q

How are xylem vessels formed?

A

Long cells with thick wall are impregnated by lignin. As the cell develops the lignin waterproofs the cell and its end wall and cell contents decay. This leaves a long column of dead cells with no contents.

72
Q

How is the xylem tissue adapted to its function?

A

_It is made up from dead cells aligned end to end to form a continuous column.
_the tubes are narrow so the water column does not break easily and capillary action can be effective.
_pits in the lignified walls allow water to move sideways from one vessel to another.
_lignin deposited in the walls in spiral, annular, or reticulate patterns allows xylem to stretch as plant grows.

Biology AS (OCR) Unit 1 (2 decks)

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