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A Level Biology > 3. Gas Exchange And Mass Transport > Flashcards

3. Gas Exchange And Mass Transport Flashcards

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1
Q

Define haemoglobin

A

Group of chemically similar molecules found in a wide variety of organisms

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2
Q

Define loading

A

Process when haemoglobin binds with oxygen
In lungs

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3
Q

Define unloading

A

Process when haemoglobin releases oxygen
Respiring tissues

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4
Q

What is the structure of haemoglobin?

A

Globular protein which is an oxygen carrying pigment found in red blood cells

Red blood cells have a bioconcave discs so high surface area to volume ratio

No nucleus to have as much space as possible for haemoglobin to transport oxygen

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5
Q

What are prosthetic groups in haemoglobin?

A

Iron containing haem group combines with oxygen to form oxyhaemoglobin

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6
Q

What causes blood to be bright red?

A

When iron combines with oxygen to form oxyhaemoglobin

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7
Q

What is the quaternary structure in haemoglobin contains?

A

Four polypeptides linked to form an almost spherical shape
Made up of two alpha polypeptides and two beta polypeptides

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8
Q

What does it mean if haemoglobin has a high affinity for oxygen?

A

Takes up oxygen more easily but releases it less easily

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9
Q

What does it mean if haemoglobin has a low affinity for oxygen?

A

Takes up oxygen less easily but releases it more easily

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10
Q

What is haemoglobin role?

A

Binding oxygen in lungs and transporting oxygen to tissues for use in metabolic pathways

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11
Q

To be efficient in transporting oxygen haemoglobin must:

A
  1. Readily associate with oxygen at the surface where gas exchange takes place
  2. Readily dissociate from oxygen at those tissues requiring it
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12
Q

How is haemoglobin able to achieve this efficiency?

A

As haemoglobin is able to change its tertiary structure in the presence of certain substances

Eg. CO2 the new shape of haemoglobin binds more loosely to oxygen

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13
Q

What do oxygen dissociation curves show?

A

Shows rate at which oxygen associates and also dissociates with haemoglobin at different partial pressures

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14
Q

Why at low oxygen concentrations little oxygen binds to haemoglobin?

A

Shape of haemoglobin makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide subunits as they are closely united

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15
Q

What happens to haemoglobin once the first oxygen binds?

A

Changes the quaternary structure causing it to change shape this makes it easier for the other oxygen molecules to bind

Known as positive cooperativity

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16
Q

Why is it harder for the fourth oxygen molecule to bind?

A

Due to probability
Majority of binding sites occupied it is less likely that a single molecule of oxygen will find an empty site to bind to

Gradient of the curve flattens off

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17
Q

What is the Bohr effect?

A

Changes in oxygen dissociation as a result of CO2 levels

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18
Q
A
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19
Q

What happens to the Bohr effect during exercise?

A

Increase CO2

Lowers pH- haemoglobin changes shape

Reduces affinity for O2

Increase O2 unloading at respiring tissues

Curve shifts to the right

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20
Q

What happens to the Bohr effect at gas exchange surfaces?

A

Concentration of CO2 is low

Affinity for O2 is increased

High concentration of O2

O2 readily loaded by haemoglobin

Curve shifts to the left

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21
Q

Why do large organisms need a transport system?

A

Constant supply of reactants needed for metabolism

Large organisms have many layers of cells= long diffusion distance= exchange surfaces created mass transport system

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22
Q

What are two factors that determine whether a specialised transport medium is required and whether or not it is circulated by a pump?

A

The surface area to volume ratio
How active the organism is

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23
Q

What are some common features of transport systems?

A

Suitable medium to carry materials= blood, normally a liquid based on water because it readily dissolves substances and can circulate easily

Moved in bulk over large distances

Mechanism to maintain mass flow movement in one direction= valves

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24
Q

What does it mean if you have a closed system?

A

Blood pumped around the body and is confined within a network of vessels

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25
What does it mean if you have an open system?
Blood not contained within vessels and is pumped directly into body cavities Eg. Arthropods
26
Why do mammals have a closed double circulatory system?
Because as blood passes through the lungs, pressure is reduced so circulation would be too slow Substances need to be delivered quickly because of mammals high body temp and high rate of metabolism
27
What does the renal artery carry
Oxygenated blood from aorta through renal artery to the kidneys
28
What does the renal vein carry?
Deoxygenated blood from the kidneys to the vena cava
29
What are the valves called that prevent the back flow of blood into the atrium when ventricles contract?
- left atrioventricular valve = bicuspid - right atrioventricular valve= tricuspid
30
What does the aorta do?
Connected to left ventricle, carries oxygenated blood to all parts of the body except lungs
31
What does the vena cava do?
Connected to the right atrium, carries deoxygenated blood back from tissues
32
What does the pulmonary artery do?
Connected to the right ventricle, carried deoxygenated blood to the lungs where it is oxygen replenished
33
What does the pulmonary vein do?
Connected to the left atrium, brings oxygenated blood back from the Lungs
34
What happens if the coronary arteries are blocked?
Myocardial infarction because an area of the heart os deprived of blood and oxygen Cells unable to respire aerobically so die
35
What are coronary arteries?
Heart muscle supplied by its own vessels
36
When do atrioventricular valves open?
When pressure is greater in atria than ventricles
37
When do semi lunar valves open?
When pressure is greater in ventricles than blood vessels
38
What are the risk factors associated with cardiovascular disease?
Smoking= carbon monoxide binds irreversibly to haemoglobin Reduces oxygen carrying capacity= raised blood pressure increasing risk of heart attack High blood pressure= heart must work harder to pump blood into arteries More likely to develop an aneurysm Blood cholesterol= HDLS remove cholesterol, LDLS= transport cholesterol to tissues
39
What are the two stages in the cardiac cycle?
Diastole= relaxation Systole= contraction of the heart
40
What happens in diastole?
1. Blood returns to the atria through the pulmonary vein and the vena cava 2. As the atria fill the pressure rises. 3. When the pressure exceeds that in the ventricles the atrioventricular valves open allowing blood to pass into the ventricles 4. The muscular walls of both atria and ventricles are relaxed 5. Relaxation of ventricle walls causes them to recoil and reduces pressure within ventricle 6. Pressure to be lower than in aorta and pulmonary artery so semi lunar valves close = ‘dub’ sound
41
What happens in atrial systole?
1. Contraction of atria walls along with recoil of relaxed ventricle walls forces out the remaining blood in the atria 2. Throughout this stage the ventricle walls are relaxed
42
What happens in ventricular systole?
1. After a short delay to allow the ventricle to fill with blood their walls contract simultaneously 2. Increases the blood pressure within them, forcing shut the atrioventricular valves and preventing back flow into the atria= ‘lub’ sound 3. The pressure rises further once it exceeds that in the aorta and pulmonary artery blood is forced into them
43
What are pocket valves?
In veins that occur without the whole venous system They ensure when veins are squeezed (skeletal muscle contract) the blood flows back towards the heart
44
Define cardiac output?
The volume of blood pumped by one ventricle of the heart in one minute
45
How to calculate cardiac output?
Cardiac output= heart rate x stroke volume
46
What is stroke volume?
Volume of blood pumped per beat
47
What happens to atrioventricular and semi lunar valves during diastole?
Atrioventricular Open Semi lunar Closed
48
What happens to atrioventricular and semi lunar valves during systole?
Atrioventricular Closed Semi lunar Open
49
How does the heart generate electricity and how is it spread?
1. The SAN group of cells in right atrium 2. Initiates a wave of depolarisation that causes the atria to contract 3. Region of non- conducting tissue which prevents the depolarisation spreading straight to ventricles 4. Instead carried to atrioventricular node (AVN)- region of conducting tissue between atria and ventricles 5. After slight delay the AVN is stimulated and passes the stimulation along the bundle of His 6. This delay means the ventricles contract after the atria
50
What is purkyne tissue?
Bundle of His divides into two conducting fibres = purkyne tissue
51
What do purkyne tissue do?
Initiate depolarisation of the ventricles from the apex of the heart This makes the ventricles contract from the bottom upward and blood is forced out of the ventricle
52
What do arteries do?
Carry blood away from the heart and into arterioles
53
What do arterioles do?
Smaller arteries that control blood flow from arteries to capillaries
54
What do capillaries do?
Tiny vessels that link arterioles to veins
55
What do veins do?
Carry blood from capillaries back to the heart
56
What are the basic structures of all blood vessels?
1. Tough fibrous outer layer= resists pressure changes 2. Muscle layer= can contract and control the flow of blood 3. Elastic layer= helps maintain blood pressure by stretching and recoiling
57
What is artery structure related to function?
Function=. Transport blood rapidly under high pressure from the heart to tissues Structure= muscle layer thick compared to veins, elastic layer is thick so blood pressure is kept high
58
What is arteriole structure related to function?
Function= carry blood under lower pressure than arteries Structure= muscle layer thicker than arteries, elastic layer is thinner than in arteries
59
What is veins structure related to function?
Function= transport blood slowly under low pressure Structure= muscle layer thin, valves to maintain one direction, elastic layer thin
60
What is capillary structure related to function?
Function= exchange metabolic materials- flow much slower to allow more time for exchange of materials Structure= walls consist of lining layer- extremely thin, rapid diffusion, numerous and highly branched , lumen narrow
61
62
What is tissue fluid?
Watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen Supplies all of these substances to the tissues
63
How is tissue fluid formed?
1. Pumping by the heart creates hydrostatic pressure at the arterial end of capillaries 2. This hydrostatic pressure causes tissue fluid to move out of the blood plasma 3. This pressure is only enough to force out small molecules leaving cells and proteins in the blood= ultrafiltration
64
The outward pressure of tissue fluid moving out of blood plasma is opposed by what two other forces?
1. Hydrostatic pressure of the tissue fluid outside the capillaries which resists outward movement of liquid 2. Lower water potential of the blood due to plasma proteins that causes water to move back into the blood within the capillaries
65
How is tissue fluid returned to the circulatory system?
1. Loss of tissue fluid from the capillaries reduced the hydrostatic pressure inside them 2. Time blood has reached the venous end of capillary its hydrostatic pressure is lower than the tissue fluid outside it 3. Tissue fluid forced back into capillaries by the higher hydrostatic pressure outside them 4. Plasma has lost water and still contains proteins= lower water potential than tissue fluid 5. Water leaves the tissue by osmosis down a water potential gradient
66
What happens to the tissue fluid that canto be returned to the capillary systems?
Returns through lymphatic system
67
What is the lymphatic system?
System of vessels that begin in the tissues which have dead end tubes which merge into larger network
68
What are the contents of the lymphatic system moved by?
1. Hydrostatic pressure of the tissue fluid that has left the capillaries 2. Contraction of body muscles that squeeze the lymph vessels- valves in lymph vessels ensure that liquid inside them moves away from the tissues

A Level Biology (7 decks)

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