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Edexcel Biology A Level > Mammalian Transport Systems > Flashcards

Mammalian Transport Systems Flashcards

1
Q

What is diffusion

A

the movement of particles in a liquid or gas down the concentration gradient from an area where they are at a relatively high concentration to an area where they are at a relatively low concentration

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2
Q

How do microscopic multicellular organisms supply their needs

A

by diffusion

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3
Q

What conditions must be met for an organism to be able to use diffusion for the transportation of all substances

A

1) the diffusion distance from the outside to the innermost areas of the cells are very small
2) the surface area in contact with the outside environment is vey large when compared to the volume inside the organism. It has a large surface area to volume ratio (sa:vol)
3) metabolic demands are low– the organisms do not regulate
their own temperature and the cells do not use much oxygen and
food or produce much carbon dioxide

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4
Q

Why do many animals have a heart and circulation which acts as a mass transport system

A

to overcome the limitations of diffusion in organisms with a small sa:vol ratio

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5
Q

what happens to the sa:vol ratio when an organism gets larger

A

it decreases

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6
Q

what happens when the sa:vol ratio decreases

A

The distance from the
outside of the organism to the inside gets longer, and there is
proportionately less surface for substances to enter through. So it
takes longer for substances to diffuse in, and they may not reach
the individual cells quickly enough to supply all their needs

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7
Q

what is a mass transport system

A

an arrangement of structures by which
substances are transported in the flow of a fluid with a mechanism for
moving it around the body

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8
Q

What are the features of a mass transport system

A

exchange surfaces

a system of vessels that carry substances

a way of making sure the substances are moved in the right direction

a way of making materials move fast enough to supply the needs of the organism

a suitable transport medium ex:fluid

a way of adapting the rate of transport to the needs of the organism

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9
Q

What are the two types of circulatory systems

A

open and closed

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10
Q

what type of circulatory system do mammals have

A

a closed circulatory system with the blood contained in tubes

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11
Q

what are the advantages of a closed circulatory system

A

the pressure can be increased to make the blood flow more quickly

the flow can be directed more precisely to the organs that need most oxygen and nutrients.

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12
Q

describe a fish’s circulatory system

A

fish have a single circulation system. The heart pumps deoxygenated blood to the gills, the organs of gas exchange where the blood takes in oxygen (becomes oxygenated) and gives up carbon dioxide at the same time. The blood then travels on around the rest of the body of the fish, giving up oxygen to the body cells before returning to the heart

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13
Q

What is a single circulation system

A

a circulation in which the heart pumps the
blood to the organs of gas exchange and the blood then travels on
around the body before returning to the heart

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14
Q

what is a double circulation system

A

a circulation that involves two separate
circuits (systemic circulation and pulmonary circulation), one of deoxygenated blood flowing from the heart to the gas
exchange organs to be oxygenated before returning to the heart, and
one of oxygenated blood leaving the heart and flowing around the
body, returning as deoxygenated blood to the heart

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15
Q

advantages of a double circulatory system

A

The separate circuits of a double circulatory system ensure that the oxygenated and deoxygenated blood cannot mix, so the
tissues receive as much oxygen as possible.

the fully oxygenated blood can be delivered quickly to the body tissues at high pressure.

The blood going through the tiny
blood vessels in the lungs is at relatively low pressure, so it does not damage the vessels and allows gas exchange to take place

If this oxygenated blood at low pressure went straight into the big vessels that carry it around the body, it would move very slowly. However, the oxygenated blood returns to the heart, so it can be
pumped hard and sent around the body at high pressure. This means it reaches all the tiny capillaries between the body cells
quickly, supplying oxygen for an active way of life.

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16
Q

What is the mass transport system in mammals

A

the cardiovascular system

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17
Q

What are the components of the blood

A

plasma
rbcs (erythrocytes)
wbcs (leucocytes)
platelets

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18
Q

what does blood plasma transport

A

chemical messages

digested food products

nutrient molecules from storage areas to the cells that need them

excretory products

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19
Q

What is the function of the blood plasma

A

transportation, maintaining body temperature, and acting as a buffer to regulate pH changes

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20
Q

What is the role of hemoglobin and where is it found

A

transportation of oxygen and carbon dioxide

it is found in erythrocytes

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21
Q

where are erythrocytes found and how long do they take to mature

A

bone marrow
120 days

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22
Q

what cell in the mammalian body does not have a nucleus

A

erythrocytes

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23
Q

what gives blood its color

A

the red pigment, heamoglobin

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24
Q

what are the adaptation of erythrocytes

A

1) The biconcave disc shape of the cells means that they have a large surface area to volume ratio, so oxygen can diffuse into and out of them rapidly
2) Having no nucleus leaves much more space inside the cells for the haemoglobin molecules that carry the oxygen

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25
Q

what are white blood cells called

A

leucocytes

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26
Q

what are red blood cells called

A

erythrocytes

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27
Q

where are erythrocytes made

A

they are made in the bond marrow, although some mature in the thymus gland

28
Q

what is the function of leucocytes

A

defend the body against infection and help in the inflammatory response of the body when an area of tissue is damaged

29
Q

describe a leucocyte cell

A

They all contain a nucleus and have colourless cytoplasm, although some
types contain granules which can be stained.

30
Q

what are platelets

A

cell fragments involved in the clotting mechanism of the blood

31
Q

what cells are platelets tiny fragments of

A

megakaryocytes (which are found in the bond marrow)

32
Q

what are megakaryocytes

A

large cells present in the bone marrow and produce platelets

33
Q

Describe the structure of hemoglobin

A

Each haemoglobin molecule is a large
globular protein consisting of four peptide chains, each with an iron-containing prosthetic group. Each group can collect four molecules of oxygen in a reversible process to form oxyhaemoglobin:

34
Q

Explain what happens when the first molecule of oxygen binds to the heamoglobin, and when it is removed

A

The first oxygen molecule that binds to the haemoglobin changes the arrangement of the molecule making it easier for the following oxygen molecules to bind. The final oxygen molecule binds several
hundred times faster than the first. The same process happens in reverse when oxygen dissociates from haemoglobin – it gets progressively harder to remove the oxygen.

35
Q

how is a steep concentarion gradient maintened between the air in the lungs and the erythrocytes

A

When the blood enters the lungs, the concentration of oxygen
in the red blood cells is relatively low. Oxygen moves into the
red blood cells from the air in the lungs by diffusion. The oxygen
is collected and bound to the haemoglobin, so the free oxygen
concentration in the cytoplasm of the red blood cells stays low.
This maintains a steep concentration gradient from the air in the
lungs to the red blood cells, so more and more oxygen diffuses in
and joins onto the haemoglobin.

36
Q

what percentage of the oxygen in the hemoglobin is released, and what percentage is reserved

A

When you are at rest or exercising gently, only about 25%
of the oxygen carried by the haemoglobin is released into your
cells. There is another 75% in reserve in the transport system for
when you are very active

37
Q

how is CO2 transported

A

Haemoglobin carries some of the carbon dioxide produced in respiration back to the lungs. The rest is transported in the plasma.

38
Q

What does the strong affinity of hemoglobin for oxygen result in

A

a small change in the proportion of oxygen in the surrounding
environment can have a big effect on the saturation of the blood
with oxygen. So in the lungs, the haemoglobin rapidly gains oxygen
and in the tissues, as the oxygen saturation of the environment
falls, oxygen is released rapidly

39
Q

What is the shape of the oxygen dissociation curve for human hemoglobin

A

sigmoid

40
Q

What happens when carbon dioxide dissolves in blood

A

d it reacts slowly with the water to
form carbonic acid, H2CO3. The carbonic acid separates to form
hydrogen ions H+ and hydrogencarbonate ions HCO3–

41
Q

what molecule forms when carbon dioxide combines with heamoglobin

A

carbaminohemoglobin

42
Q

What is the name of the enzyme that controls the rate of reaction between carbon dioxide and water to produce carbonic acid

A

carbonic anhydrase

43
Q

Describe the process of CO2 being transported to the lungs

A

1) Carbon dioxide passes into the plasma and red blood cells by diffusion. It combines with water to form carbonic acid, catalyzed by the enzyme carbonic anhydrase.

2) Carbonic acid dissociates to give hydrogen ions and hydrogen carbonate ions.

3) Hydrogen carbonate ions pass
out of the red blood cells by
diffusion, and chloride ions move
in. This is called the CHLORIDE SHIFT

4) Haemoglobin acts as a buffer,
accepting the hydrogen ions to
form haemoglobinic acid to avoid
changing the pH of the blood.

44
Q

What happens to heamoglobins affinity for oxygen when the proportion of CO2 is increased

A

decreases because as CO2 builds up it affects the pH and this has an effect on the protein structure, so hemoglobin does not work as well (i.e. it has a lower affinity for oxygen).

45
Q

What is the bohr effect and explain

A

the name given to changes in the oxygen dissociation curve of haemoglobin that occur due to a rise in carbon dioxide levels and a reduction of the affinity of haemoglobin for oxygen.

explanation: When the proportion of carbon dioxide in the tissues is high, the affinity of haemoglobin for oxygen is reduced. In other words, haemoglobin needs higher
levels of oxygen to become saturated and releases oxygen much more easily. So in active tissues with high carbon dioxide levels, haemoglobin releases oxygen more readily. Carbon dioxide levels in the
lung capillaries are relatively low, which makes it easier for oxygen to bind to the haemoglobin. The changes in the oxygen dissociation curve that result as the carbon dioxide level changes are known as the Bohr effect

46
Q

What is the name of the special oxygen carrying pigment in the fetus

A

fetal heamoglobin

47
Q

What is different between fetal hemoglobin and adult hemoglobin

A

Fetal haemoglobin has a higher affinity for oxygen than the adult haemoglobin
of the mother. Consequently, the fetal haemoglobin can remove oxygen from the maternal blood even when the proportion of oxygen is relatively low

48
Q

what ensures the concentration gradient between the mother’s blood and
that of her fetus as steep as possible

A

the maternal and fetal blood running opposite directions. This maximizes the oxygen transfer to the blood of the fetus

49
Q

What happens as a result of contact between platelets and components of a cut tissue (e.g. collagen fibers in the skin)

A

platelets break open in large numbers and release several substances such as serotonin and thromboplastin

Serotonin causes the smooth muscle of the blood vessel to contract. This narrows the blood vessels, cutting off the blood flow to the damaged area.

Thromboplastin is an enzyme that starts a sequence of chemical changes that clot the blood

50
Q

Describe the blood clotting process

A

1) Thromboplastin catalyses the conversion of a large soluble protein called prothrombin found in the plasma into another soluble protein, the enzyme called thrombin. Calcium ions need to be present in the blood at the right concentration for this reaction to happen.

2) Thrombin acts on another soluble plasma protein called fibrinogen, converting it to an insoluble substance called fibrin. The fibrin forms a mesh of fibres to cover the wound.

3) More platelets and red blood cells pouring from the wound get trapped in the fibrin mesh. This forms a clot.

4) Special proteins in the structure of the platelets contract, making the clot tighter and tougher to form a scab that protects the skin and vessels underneath as they heal.

51
Q

What are the types of blood vessels

A

arteries, capillaries and veins

52
Q

What is the function of arteries

A

carrying blood away from the heart (usually oxygenated)

53
Q

Which arteries carry deoxygenated blood

A

pulmonary artery and umbilical artery

54
Q

Describe the structure of an artery

A

1) thick walls and lots of
collagen to withstand the high
pressure.
2) The middle layers of the artery wall contain elastic fibres and smooth muscle; arteries nearest the heart have more elastic
fibres, those further from the heart have a greater proportion of muscle tissue
3) Lumen is small when artery unstretched by flow of blood from heart
4) external layer of tough tissue
5) The endothelium forms a smooth lining which allows the easiest possible flow of blood.

55
Q

why do arteries have a lot of elastic fibers

A

so they can stretch to
accommodate the greater volume of blood without being damaged. Between surges, the elastic fibres return to their original length, squeezing the blood to move it along in a continuous flow.

Note: The role of the elastic fibres in artery walls is to return to their original
length to help maintain the pressure. This is called recoil. The elastic recoil does not help to increase pressure, it simply helps to maintain the pressure – so do not suggest that the recoil helps pump blood along

56
Q

What are peripheral arteries

A

arteries further away from the heart but before the arterioles

57
Q

What is the role of muscle fibers in arteries

A

contract or relax to change the size of the lumen, controlling the blood flow. The smaller the lumen, the harder it is for blood to flow through the vessel. This controls the amount of blood that flows into an organ, so regulating its activity

58
Q

What is an advantage of capillaries having a small diameter

A

the blood travels relatively slowly through them, giving more opportunity for
diffusion to occur

59
Q

How are capillaries adapted

A

Their walls are very thin and contain no elastic fibres, smooth muscle or collagen. This helps them fit between individual cells and allows rapid diffusion of substances between the blood and the cells. The walls consist of just one very thin cell
the lumen is just large enough to let Erythrocytes pass through

60
Q

What is the function of veins

A

carrying blood towards the heart (usually deoxygenated)

61
Q

Which veins carry oxygenated blood

A

pulmonary vein and umbilical vein

62
Q

What is the structure of a vein

A

1) smooth inner surface
2) relatively thin layer of smooth muscle with few elastic fibers
3) relatively large lumen
4) outer tough layer consisting mainly of collagen fibers

63
Q

name the two veins that carry blood back to the heart

A

inferior vena cava (from the lower parts of the body) and superior vena cava (from the upper parts of the body)

64
Q

what is caused as a result of veins having a very large lumen

A

hold a large volume of blood and act as a blood reservoir

65
Q

Why do veins have low blood pressure

A

the pressure surges from the heart are eliminated before the blood reaches the capillary system. This blood at low pressure
must be returned to the heart and lungs to be oxygenated again and recirculated.

66
Q

What two mechanisms are used to return blood to the heart

A

muscle pressure and one-way valves

Edexcel Biology A Level (3 decks)

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