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A-levle Biology > 3.1.2 - Transport In Animals (set C - Transport Of Substances) > Flashcards

3.1.2 - Transport In Animals (set C - Transport Of Substances) Flashcards

1
Q

What are erythrocytes?

A

Red blood cells - very specialised and have a number of adaptions to their main function of transporting oxygen

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2
Q

Explain how erythrocytes are adapted for their role - give 2 ways and explain them?

A
  • biconcave shape - provides a larger SA then just a simple disk structure, more SA available for diffusion of gases, helps with moving through narrow capillaries
  • mature erythrocytes loose their nuclei when they enter circulation - maximises amount of Haemoglobin that fits into cells, as well as limiting their life (about 120 days in bloodstream)
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3
Q

Explain what Haemoglobin is?

A

Red pigment that carries oxygen (gives erythrocytes their colour) - is a very large globular conjugated protein, made up of four peptide chains, each with an iron-containing haem prophetic group

  • oxygen binds loosely to Haemoglobin forming oxyhaemoglobin
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4
Q

Explain what type of protein Haemoglobin is?

A

Very large globular conjugated protein made up of four peptide chains, each with an iron-containing haem prosthetic group

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5
Q

Give the equation for Haemoglobin binding with oxygen?

A

Haemoglobin + oxygen - oxyhaemoglobin

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6
Q

Explain the process of oxygen binding to Haemoglobin?

A

Erythrocytes enter the capillaries in the lungs, the oxygen levels in the cells are relatively low creating a seep concentration gradient between the inside of the erythrocytes and the air in the alveoli - this causes oxygen to move into the erythrocytes and bind with the Haemoglobin

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7
Q

Explain positive cooperativity, and how it takes place?

A

Arrangement of the Haemoglobin molecule means that as soon as one oxygen molecules binds to a haem group the molecule changes shape - making it easier for the next oxygen molecule to bind

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8
Q

Explain fully the process of erythrocytes receiving oxygen in the lungs?

A

Erythrocytes enter capillaries in lungs (oxygen levels in cell are low) steep concentration gradient between inside of erythrocytes and air in alveoli

Oxygen moves into the erythrocytes and binds with Haemoglobin - molecule changes shape (positive cooperativity) easier for next oxygen molecule to bind

Diffusion gradient is maintained until all the Haemoglobin is saturated with oxygen

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9
Q

Explain how a seep diffusion gradient is maintained in erythrocytes in the capillaries of lungs?

A

Because the oxygen is bound to the Haemoglobin, the free oxygen concentration in the erythrocyte stays low, so a steep diffusion gradient is maintained until all of the Haemoglobin is saturated with oxygen

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10
Q

Explain what happens when erythrocytes reaches body tissues?

A

The concentration of oxygen in the cytoplasms of the body cells is lower than in the erythrocytes - oxygen moves out of the erythrocytes down a concentration gradient - once the first oxygen molecule is released by the Haemoglobin, the molecule changes shape making it easier to remove the remaining oxygen molecules

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11
Q

What is the oxygen dissociation curve?

A

Graphical representation of the relationship between the percentage saturation Haemoglobin in the blood against the partial pressure of oxygen

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12
Q

Explain why a small change in the pressure of oxygen makes a significant difference to the saturation of Haemoglobin?

A

once the first molecule becomes attached with a haem group, the change in shape means other oxygen molecules are added rapidly (positive cooperativity)

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13
Q

Describe the oxygen dissociation curve for human Haemoglobin?

A

1) at low partial pressure of oxygen, few Haem groups are bound to oxygen, so Haemoglobin does not carry much oxygen

2) at higher partial pressure of oxygen, more haem groups are bound to oxygen, so it changes shape and makes it easier for more oxygen to be picked up

3) the Haemoglobin becomes saturated at very high partial pressure of oxygen as all the haem groups become bound - curve levels out, no more oxygen uptake

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14
Q

Explain where the difference in partial pressure of oxygen occurs?

A
  • High partial pressure of oxygen in the lungs, so haemoglobin in the erythrocytes are rapidly loaded with oxygen
  • relatively small drop in oxygen levels in the respiring tissues means oxygen is released rapidly from haemoglobin to diffuse into the cells
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15
Q

Explain why partial pressure of oxygen is important?

A

The partial pressure of oxygen has a significant effect on wether oxygen will bind to, or be released from haemoglobin

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16
Q

Explain the change known as bohrs effect?

A

As the partial pressure of carbon dioxide rises (higher partial pressure of carbon dioxide), Haemoglobin gives up oxygen more easily - the Bohrs effect is important in the body

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17
Q

Explain 2 ways bohrs effect is important in the body?

A
  • in active tissues with a high partial pressure of carbon dioxide, haeomoglobin gives up oxygen more readily
  • in the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules easily
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18
Q

Explain feta haemoglobin?

A

When a fetus is developing it’s completely dependent on the mother to supply it with oxygen - oxygenated blood from the mother runs close to the deoxygenated fetus blood in the placenta - oxygen removed from maternal blood due to fetal blood having higher affinity for oxygen

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19
Q

Explain the problem if the blood of the fetus had the same affinity for oxygen as the mother?

A

if the blood of the fetus had the same affinity for oxygen as the blood of the mother, then little to no oxygen would be transferred to the blood of the fetus

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20
Q

Explain the problem between the mother and fetal blood, explain how its avoided?

A

If the affinity for oxygen is the same for both bloods, then none would need transferred to the blood of the fetus

Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin - so it removes oxygen from the maternal blood as they move past each other

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21
Q

Explain three ways carbon dioxide is transported from tissues to the lungs?

A
  • 5% carried dissolved in the plasma
  • 10-20% combined with the amino groups in the polypeptide chains of Haemoglobin forming carbaminohaemoglobin
  • 75-85% is converted into hydrogen carbonate ions in cytoplasm of RBCs
22
Q

Explain what happens to most carbon dioxide from respiring tissues?

A

Diffuses into RBCs - reacts with water forming carbonic acid (catalysed by carbonic anhydrase)

  • carbonic acid dissociates to give hydrogen ions and hydrogencarbonate ions
23
Q

State the enzyme which catalyses formation of carbonic acid from water and carbon dioxide?

A

Carbonic anhydrase

24
Q

Explain the products of the dissociation of carbon acid?

A
  • hydrogen ions - H+
  • hydrogencarbonate ions - HCO3-
25
Q

Explain the result of excess H+ ions, what compound is formed?

A

Causes oxyhemoglobin to unload oxygen, so that the Haemoglobin can take up the H+ ions (reversible reaction)

  • forms compound called haemoglobonic acid
26
Q

Explain how Haemoglobin acts to reduce the concentration of hydrogen ions in the blood?

A

Acts as a buffer and prevents changes in the pH - stops the H+ ions from increasing the cells acidity by accepting free H+ ions in a reversible reaction to form Haemoglobinic acid

27
Q

Explain what the chloride shift is?

A

The movement of negatively charged chloride ions via transport proteins into RBCs - occurs when hydrogen carbonate ions are formed (due to carbonic acid dissociating)

  • prevents red blood cells becoming positively charged
28
Q

Outline the need for the chloride shift?

A

The movement of negatively charged chloride ions into RBCs prevents them from becoming positively charged - which occurs due to the build up of H+ ions formed from the dissociation of carbonic acid

29
Q

Explain what happens to hydrogencarbonate ions in the RBCs?

A

Negatively charged hydrogencarbonate ions formed from the dissociation of carbonic acid are transported out of RBCs via a transport protein

  • transported in the blood plasma
30
Q

Outline what happens when blood reaches the lung tissue?

A
  • relatively low carbon dioxide concentration
  • carbonic anhydrase catalyses the reverse reaction - breaking down carbonic acid into carbon dioxide and water
  • hydrogen carbonate ions diffuse back into RBCs forming more carbonic acid
  • chloride ions diffuse out down an electrochemical gradient
31
Q

Explain the removal of chloride ions from RBCs in the lung tissue?

A

Chloride ions diffuse out of the red blood cells into the plasma down an electrochemical gradient

32
Q

Explain 4 functions of the blood?

A
  • transport of oxygen and carbon dioxide from and to cells

-platelets to damaged areas

  • cells and antibodies involved in the immune response
  • chemical messages (hormones)
33
Q

Outline the structure of blood - give examples of substances transported?

A

Consists of plasma (yellow liquid) composed of 95% water and makes up 55% of the blood by volume and carries components like
- dissolved glucose
- amino acids
- mineral ions
- RBCs
- larger plasma proteins
- platelets

34
Q

Explain briefly what platelets are, where do they come from?

A

Fragments of megakaryocytes (large cells) found in the red bone marrow - involved in clotting mechanism of blood

35
Q

Explain the formation of tissue fluid?

A

Blood passing through capillaries results in some plasma leaking out through gaps in the capillary walls that surround cells of the body

  • similar composition to plasma - contains a lot less proteins (as they are too lager to fit through gaps)
36
Q

Outline the role of tissue fluid - give an example?

A

Fluid bathes all the cells of the body outside the circulatory system - allows for diffusion of substances between blood and cells

Eg - carbon dioxide produced in respiration leaves a cell, and dissolves into the tissue fluid surrounding it and moves into the capillary

37
Q

Explain hydrostatic pressure in regard to tissue fluid formation?

A

Pressure exerted by fluid (blood) in this case blood pressure, which is generated by the contraction of the heart

38
Q

Explain onoctic pressure in regard to tissue fluid formation?

A

The osmotic pressure exerted by plasma proteins within a blood vessel

  • plasma proteins lowers the water potential within the vessel - causes water to move into the blood via osmosis
39
Q

What two factors which affects the volume of liquid that leaves the plasma?

A
  • hydrostatic pressure
  • oncotic pressure
40
Q

Outline what happens at the arterial end - in regard to the formation of tissue fluid?

A
  • Hydrostatic pressure is greater than osmotic - forces fluid out of the capillary
  • proteins are too large for the pores and remain in the blood
  • increased protein content creates a water potential gradient between capillary and tissue fluid
41
Q

Outline what happens at the venous end - in regard to the formation of tissue fluid?

A
  • hydrostatic pressure lower than osmotic pressure - water flows back into the capillary (90%)
  • water potential gradient between capillary and the tissue fluid remains the same as arterial end
  • 10% remains as tissue fluid and is collected by lymph vessels
42
Q

Explain why the hydrostatic pressure is lower at the venous end of the capillary?

A

Hydrostatic pressure reduced due to increased distance from the heart and the slowing of blood flow as it passes through the capillaries

  • osmotic pressure is greater
43
Q

Explain the result of higher blood pressure at the arterial end - result on tissue fluid?

A

High blood pressure (hypertension) means the pressure at the arterial end is even greater - pushes more fluid out of the capillary which accumulates around the tissues (oedema)

44
Q

Outline the formation of lymph?

A

Most tissue fluid re-enters the capillaries whilst some enters lymph vessels (10%) - fluid now known as lymph - returns to the blood, flowing into the right and left subclavian veins

45
Q

Describe the structure of lymph vessels?

A
  • closed ends and large pores - allow large molecule to pass through
  • lymph capillaries join to form larger vessels
  • valves prevent back flow
  • fluid transported by the squeezing of the body muscles
46
Q

Explain why lymph contains fatty acids?

A

Contains fatty acids absorbed into the lymph from the villi of the small intestine - transported to bloodstream by lymph system

47
Q

Explain the role and location of lymph nodes?

A

located along the lymph vessels - lymphocytes build up in the nodes and are passed into the blood when necessary (play important role in defence mechanism of the body)

  • nodes intercept bacteria from the lymph
48
Q

Outline the significance of lymph nodes regarding the defence of the body?

A

Lymph nodes store lymphocytes which when necessary can produce antibodies which are then passed into the blood,

  • lymph nodes intercept bacteria and other debri from lymph - phagocytes digest them
49
Q

Outline the substances found in blood?

A

-red blood cells
- white blood cells
- platelets
- proteins
- water
- dissolved solutes

50
Q

Outline the substances found in tissue fluid?

A
  • very few white blood cells
  • very few proteins - too big to fit through capillaries
  • water
  • dissolved solutes
51
Q

outline the substances found in lymph?

A
  • white blood cells
  • proteins (only antibodies)
  • water
  • dissolved solutes
52
Q

Explain why there are very few RBCs, WBCs and proteins in tissue fluid compared to blood?

A
  • RBCs are too big to get through capillary walls (none present)
  • WBCs are in the lymph system - only enter tissue fluid during infection (very few)
  • most plasma proteins are too big to get through capillary walls (very few)

A-levle Biology (24 decks)

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