6b. Transport in the blood

Question 1

What is the blood made up of

Answer 1

Plasma
Platelets
RBC
WBC

Question 2

What can blood transport

Answer 2

-CO2 from the organs to the lungs
-Soluble products of digestion from the small intestine to the other organs
-Urea from the liver to the kidneys

Question 3

What do RBC do

Answer 3

Transport oxygen from lungs to the organs using haemoglobin.
They have no nucleus

Question 4

What does a WBC do

Answer 4

Form part of the bodys defence against microorganisms
They do have a nucleus

Question 5

What do platelets do

Answer 5

Small fragments of cells
Help blood to clot at the site of a wound
They have no nucleus

Question 6

What are the different types of WBC found in the blood

Answer 6

Lymphocytes (B and T cells)
Phagocytes

Question 7

What is the lifecycle of a RBC

Answer 7

About 120 days
Their membranes become more and more fragile until they are destroyed - normally in the spleen

Question 8

What are 3 unusual things about RBC

Answer 8

Very small
Shaped like a biconcaved disc
Have no organelles

Question 8

Why are RBC very small

Answer 8

Every haemoglobin molecule is near to the cell’s membrane
Short diffusion pathway for oxygen
Large SA:V

Question 9

Why are RBC biconcaved

Answer 9

Increases SA:V
Oxygen can quickly diffuse in and out
Short diffusion pathway

Question 10

Why do RBC have no organelles

Answer 10

Can carry as much haemoblobin and as much oxygen as possible

Question 11

What is tissue fluid

Answer 11

Cells are bathed in tissue fluid, which provides them with water, oxygen, glucose and other nutrients
Essential for the efficient exchange of materials between the blood and the cells
Constantly being formed at the arteriole end of capillaries and reabsorbed at the venule end

Question 12

How are capillaires suited to their function

Answer 12

· Pores in wall to increase permeability
· Small size and large numbers of capillaries give a large SA:VOL ratio
· Narrow diameter – slows blood flow, so more time for diffusion/exchange

Question 13

What is the hydrostatic pressure of the blood in the arteriole end of the cappilary

Answer 13

Its high
Due to the contraction of the left ventricle in ventricular systole

Question 14

What two opposing forces affect the formation and reabsorption of tissue fluid

Answer 14

-The high BP forces out water, salts and nutrients
-The soluble plasma proteins in blood, which reduces WP of the blood. Creates a WP gradient which exertts a pulling force, opposing loss of fluid

Question 15

Why dont plasma proteins leave the capillary along

Answer 15

Too large to fit through capillary pores

Question 16

How is tissue fluid formed

Answer 16

At the arteriole end of capillaries, the BP is greater than the WP gradient.
So water and solutes are forced out of the blood through the pores in the capillary walls forming the fluid

Question 17

How does tissue fluid exchange substances with cells

Answer 17

Freshly formed tissue fluid has a high concentration of oxygen, glucose and mineral ions needed by the cells
Substance diffuse into cells
Waste products diffuse out of the cells into tissue fluid then into the capillaries along with water at the venule end
Tissue fluid is the site of the exchange of metabolites

Question 18

What happens to blood as it passes trough capillaries

Answer 18

As blood moves from the ateriole to the venule end of the capillary, there is a fall in the BP and so the outward force is much reduced

Question 20

What happens to WP through the capillaries

Answer 20

-WP at venule end is low
PP remain inside the capillary
-WP in the tissue fluid is high
large, inward osmotic pull which is now greater than the outward BP
-Water is drawn back into capillaries by osmosis down a WP gradient at the venule end

Question 21

What happens to suplus tissue fluid

Answer 21

More fluid leaves the capillaries than is reabsorbed
Drains into the lymphatic vessels
Blind ending tubes with valves which return to the blood via the thoracic duct in the neck

Question 22

Summarise tissue fluid formation + reabsorption

Answer 22

-At arteriole, outward BP is greater than inward WP gradient from PP
-Water, ions and small molecules are filtered / forced out of blood into spaces between cells
-Loss of fluid from blood leads to fall in BP at venule end
-At venule, inward osmotic pull exceeds the outward BP and some water re-enters by osmosis down a WP gradient
-TF is drained from cells by lymph vessels and returned to blood

Question 23

What is the solubility of oxygen in water

Answer 23

Relativley low, but oxygen carrying capacity of the bloodis increased by the presence of blood pigments

Question 24

What does haemoglobin do

Answer 24

Blood pigment with a high affinity for oxygen and readily loads oxygen where O2 concs are high
Unloads O2 where O2 conc are low

Question 25

Why is haemoglobin a conjugated protein with a quaternry structure

Answer 25

Conjugated - Protein is bound to a non-protein group
-Quaternary - protein has more than one polypeptide chain

Question 26

What is the name of haemoglobin bound to oxygen

Answer 26

oxyhaemoglobin

Question 27

What is percentage saturation

Answer 27

The amount of oxygen carried by haemoglobin when refered to as a percentage of the maximum that can be carried

Question 28

What is cooperative binding

Answer 28

Each haemoglobin molecule combines with four moleucles of O2 in 4 separate reversible reactions
Binding of the first haem grp with O2 changes te tertiary structure and shape of haemoglobin
This uncovers the 2nd haem grp
Making it more accessible and easier for oxygen to bind
increasing the affinity
This increases the affinity of the 3rd haem grp etc
Explains why the oxygen dissociation curve has a sigmoidal shape

Question 29

What is the oxygen dissociation curve for haemoglobin

Answer 29

a graphical representation of the behaviour of haemoglobin when subjected to differing partial pressures of oxygen
Partial pressure of oxygen is shown as pO2
Curve is sigmoidal and displays the % saturation of haemoglobin with oxygen at varying pO2

Question 30

What is the dissociation curve for haemoglobin influenced by

Answer 30

Temperature
pH
CO2 conc

Question 31

What is the Bohr shift

Answer 31

dissociation curve for haemoglobin is influenced by an increase is temp, pH , CO2 conc
Displaces curve to right
It facilitates delivery of oxygen to the respiring tissues

Question 33

How does the size of a mammal relate to the oxygen dissociation curve

Answer 33

Smaller mammals have haemoglobin with lower affinity for oxygen in order to facilitate oxygen delivery to the tissues
They have larger SA:V so lose heat faster
Have increased respiration rates to release more heat to replace what is lost
Have a higher rate of O2 consumption per gram of body mass due to the faster respiration

Question 34

What does high affinity haemoglobin look like

Answer 34

• In organisms that live in low pO2 environments
  -Haemoglobin loads O2 more readily
  -Curve shifts to left
  -Haemoglobin is more saturated at any given po2

Question 35

What does lower affinity haemoglobin look like

Answer 35

• Usually in organisms that have high metabolic rate (e.g. small mammals with large SA:volume ratio and high rates of heat loss)
• Haemoglobin unloads oxygen more readily at tissues for respiration
• Curve shifted to right
• Haemoglobin has reduced saturation at any given pO2