Transport in mammals

Question 1

Describe a closed system

Answer 1

blood is contained in blood vessels

Question 2

Describe a double circulatory system

Answer 2

blood passes through the heart twice in one complete circuit

Question 3

What is a systemic circulatory system?

Answer 3

Oxygenated blood is pumped out of the heart via the aorta to most body tissues.

Veins collect deoxygenated blood from these organs (e.g. the renal vein collects deoxygenated blood from the kidneys).

Deoxygenated blood is returned to the heart via the vena cava.

Question 4

What is a pulmonary circulatory system?

Answer 4

1. deoxygenated blood is pumped out of the heart via the pulmonary artery of the lungs
2. Oxygenated blood is returned to the heart via the pulmonary vein from the lungs

Question 5

Describe the structure of arteries

Answer 5

• carry blood away from the heart

-have relatively thick walls that allow them to withstand high pressure of blood

-narrow human (ensures that blood remains at high pressure)

-walls are composed of elastic fibres and muscular tissues (arteries closer to the heart contain a higher proportion of elastic fibres because they must be able to stretch and recoil to accommodate blood surging through preventing them from bursting)

Question 6

Why do arteries that are further away from the heart have higher proportion of elastic fibres?

Answer 6

they must be able to stretch and recoil to accommodate blood surging through preventing them from bursting

Question 7

What is the diameter of a capillary

Answer 7

5-10 μm (the diameter of a typical red blood cell is 7 μm

Question 8

Describe the structure and function of a capillary

Answer 8

-the endothelial wall is only one cell thick
( ensures that substances can diffuse easily between the capillary and neighbouring cells)

-the walls are ‘leaky’ (small gaps between individual squamous epithelial cells that form the wall to allow small substances to leak out of the blood into the fluid surrounding the cells of the body)

-narrow diameter 5-10 μm

Question 9

Describe the structure and function of veins

Answer 9

• transports blood to the heart

-outer layer is relatively tough and composed of collagen fibres

-middle layer is relatively thin and contains small amounts of elastic fibres and smooth muscle

-lumen is large

Question 10

Describe the structure of red blood cells

Answer 10

• have no nucleus

-contain haemoglobin which has a quaternary structure that contains haem iron groups

-have a biconcave shape

Question 11

Describe the structure of monocytes

Answer 11

-largest whit blood cell
- nucleus shaped like a kidney or bean
-nucleus tends to appear lighter after staining (light blood colour)

Question 12

Describe the structure of neutrophils

Answer 12

• has a multi lobed nuclei
• granules of neutrophils typically stain pink or purple

Question 13

Describe the structure of lymphocytes

Answer 13

• small white blood cells
• have a large nucleus (stains a dark colour)
• they are around the size of red blood cells

Question 14

Explain the role of water in blood and tissue fluid

Answer 14

• main component of blood
• good solvent (makes it ideal for transport in mammels)

-has high specific heat capacity (its vital in maintaining the temperature of blood and tissue fluid it keeps it constant)

Question 15

Describe the structure of haemoglobin

Answer 15

• contains four ham iron groups each able to bind to an oxygen molecule

Question 16

What happens when oxygen binds to haemoglobin

Answer 16

oxyhemoglobin is formed
4O2 + Hb —-> Hb4O2

Question 17

What happen when the first oxygen molecule binds to haemoglobin?

Answer 17

-the structure of the haemoglobin molecule changes
-making it easier for each successive oxygen molecule to bind (cooperative binding)

Question 18

How is tissue fluid formed?

Answer 18

as blood passes through capillaries some plasma leaks out through gaps in the walls of the capillary to surround the cells of the body

Question 19

Why does tissue fluid contain fewer proteins than plasma

Answer 19

proteins are too large to fit through gaps in the capillary walls and so remain in the blood

Question 20

What is this chloride shift?

Answer 20

the movement of chloride ions into red blood cells that occurs when hydrogen carbonate ions are formed

Question 21

Describe the process of forming hydrogen carbonate

Answer 21

-Carbon dioxide diffuses into the red blood cells

-the enzyme carbonic anhydrase catalyses the combining of carbon dioxide and water to form carbonic acid
CO2 + H2O ⇌ H2CO3

-carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions
H2CO3 ⇌ HCO3- + H+

Question 22

What is the equation for the formation of carbonic anhydrase

Answer 22

CO2 + H2O ⇌ H2CO3

Question 23

Describe the process of the chloride shift

Answer 23

• carbon dioxide diffuses into the red blood cells

-the enzyme carbonic anhydrase catalyses the reaction btwn water and carbon dioxide forming carbonic acid

-the carbonic acid dissociates to form hydrogen ions and hydrogen carbonate ions

-the negatively charged hydrogen carbonate ions are transported out of the red blood cells via a transport protein

• to prevent an electrical imbalance occurring negatively charged chloride ions are transported into the red blood cells via the same transport protein

Question 24

What will happen if the chloride shift does not happen?

Answer 24

red blood cells would become positively charged as a result of a buildup of hydrogen ions

Question 25

How is the pH of red blood cells not lowered by H+ ions

Answer 25

the hydrogen ions can combine with the haemoglobin forming haemoglobinic acid

Question 26

Explain how carbon dioxide is transported in the form of hydrogen carbonate ions

Answer 26

-Carbon dioxide diffuses down a concentration gradient from respiring cells into the plasma, and diffuses again into red blood cells

-In the red blood cells some carbon dioxide combines with water to form carbonic acid, in a reaction catalysed by the enzyme carbonic anhydrase

-Carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions

-The hydrogen carbonate ions diffuse out of the red blood cells into the plasma, where they are transported to the lungs

Question 27

What does the oxygen dissociation curve show?

Answer 27

the rate at which oxygen associates, and also dissociates with haemoglobin

(at different partial pressures of oxygen)

Question 28

What is partial pressure of oxygen?

Answer 28

• a measure of oxygen concentration
  (the pressure exerted by oxygen within a mixture of gases)

Question 29

When is haemoglobin referred to as being saturated?

Answer 29

-when all its oxygen binding sites are take up with oxygen

Question 30

When does haemoglobin affinity for oxygen change?

Answer 30

at different partial pressure of oxygen

Question 31

What happens to oxygen at low partial pressure of oxygen?

Answer 31

binds slowly to haemoglobin
(haemoglobin has a low affinity for oxygen at low pO2)

Question 32

what happens when there’s an increase in partial pressure of oxygen?

Answer 32

haemoglobin saturation also increases

Question 33

What happens to oxygen at high pO2?

Answer 33

binds more easily to haemoglobin
(haemoglobin has a high affinity for oxygen)

Question 34

Explain the shape of oxygen dissociation curve

Answer 34

Due to the shape of the haemoglobin molecule it is difficult for the first oxygen molecule to bind to haemoglobin; this means that binding of the first oxygen occurs slowly, explaining the relatively shallow curve at the bottom left corner of the graph

-After the first oxygen molecule binds to haemoglobin, the haemoglobin protein changes shape, or conformation, making it easier for the next haemoglobin molecules to bind; this speeds up binding of the remaining oxygen molecules and explains the steeper part of the curve in the middle of the graph

-The shape change of haemoglobin leading to easier oxygen binding is known as cooperative binding

Question 35

What are changes in the oxygen dissociation curve as a result of carbon dioxide levels known as?

Answer 35

Bhor effect/shift

Question 36

What happens when partial pressure of carbon dioxide is high in the blood?

Answer 36

haemoglobin affinity for oxygen is reduced

Question 37

On a graph showing the dissociation curve, when does the curve shift to the right

Answer 37

When carbon dioxide levels increase ( meaning less haemoglobin is saturated)

Question 38

Describe the cardiac cycle

Answer 38

The Sinoatrial node sends out a wave of excitation and this spreads across both atria, causing atrial systole. Non-conducting tissue called the Annulus fibrosus prevents the excitation from spreading to the ventricles and so this ensures that atria and ventricles don’t contract at the same time. The Atrioventricular node then sends the wave of excitation to the ventricles after a short delay of around 0.1 - 0.2 seconds, ensuring that the atria have time to empty their blood into the ventricles. The Purkyne fibres conduct the excitation down the septum of the heart and to the apex, before the excitation is carried upwards in the walls of the ventricles. This means that during ventricular systole, the blood contracts from its base and blood is pushed upwards and outwards.

Question 39

Three ways carbon dioxide is transported in the blood?

Answer 39

-bicarbonate
-dissolved gas
-carbaminohaemoglobin bound to haemoglobin