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AQA Biology A level > Mass transport > Flashcards

Mass transport Flashcards

1
Q

What is the importance of mass transport?

A

Mass transport systems are needed to carry substances between exchange surfaces and the rest of body

  • Diffusion is not enough to maintain tissue fluid composition as cells are too far from exchange surfaces
  • It maintains the final diffusion rates between cells
  • It maintains a stable immediate environment of tissue fluid
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2
Q

What is the structure of the circulatory system?

A
  • Closed double circulatory system
  • Blood passes through the heart twice to reach the entire body
  • Pulmonary circulation (blue side) - Deoxygenated blood in the right side of heart is pumped to the lungs, oxygenated blood returns to the left side of the heart
  • Systemic circulation (red side) - Oxygenated blood in the left side of the heart is pumped to tissues/organs, deoxygenated blood returns to right side
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3
Q

Where are these located?

  • Heptic artery/vein
  • Renal artery/vein
  • Intestinal artery
A

Heptic artery- left side of the heart (to liver)

Intestinal artery- left side of the heart (to stomach/intestine)

Renal artery- left side of the heart (to kidneys)

Heptic vein- right side of the heart (from liver)

Renal vein- right side of the heart (from kidneys)

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4
Q

Why is a double circulatory system important for mammals?

A
  • Prevents the mixing of oxygenated and deoxygenated blood (efficient transport of oxygen and glucose for respiration + blood fully saturated with O2)
  • Blood can be pumped at a higher pressure (as lowers after being in the lungs) as a result substances are removed from body cells quicker + more efficiently
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5
Q

What is the function of the coronary arteries?

A

Deliver oxygenated blood to the heart

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6
Q

What are the blood vessels entering and leaving heart? + functions

A
  • Aorta- takes oxygenated blood from heart to respiring tissues
  • Vena Cava- takes deoxygenated blood from respiring tissues to the heat
  • Pulmonary artery and Pulmonary Vein
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7
Q

What are the blood vessels entering and leaving lungs? + functions

A
  • Pulmonary Artery- takes deoxygenated blood from the heart to the lungs
  • Pulmonary Vein- takes oxygenated blood from the lungs to the heart
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8
Q

What are the blood vessels entering and leaving kidneys? + functions

A
  • Renal arteries- take deoxygenated blood to kidneys

- Renal veins- take deoxygenated blood to the vena cava from the kidneys

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9
Q

What is the structure of the heart?

A
  • Atrioventricular valves- prevents the back flow of blood from ventricles to atria
  • Semi-lunar valves- prevents the back flow of blood from arteries to ventricles

(look at photo of a heart)

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10
Q

Why does the left side of the heart have a thicker muscular wall?

A
  • Generates a higher blood pressure

- For oxygenated blood to travel a further distance around the body

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11
Q

Why does the right side of the heart have a thinner muscular wall?

A
  • Generates lower blood pressure

- For deoxygenated blood to travel a small distance to the lungs where high pressure would damage to alveoli

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12
Q

What is the structure of the arteries and how does this relate to their function?

A

Arteries- carry blood from the heart to the rest of the body at a high pressure

  • Thick smooth muscle layer -> contract to push blood along, control/maintain blood flow/pressure
  • Elastic tissue layer -> stretch as ventricle contracts (under high pressure) and recoil when ventricle relaxes (under low pressure)
  • Thick wall -> withstand high pressure and prevents bursting of artery
  • Smooth and thin endothelium -> reduces friction
  • Narrow lumen -> increases and maintains high blood pressure
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13
Q

What is the structure of the arterioles and how does this relate to their function?

A

Arterioles- division of arteries to smaller vessels allowing the blood to be directed to different areas/capillaries

(similar to arteries)

  • Thicker muscle layer than arteries -> narrows lumen to reduce blood flow by constricting but widens lumen to increase blood flow by dilating
  • Thinner elastic layer (than arteries) due to lower pressure
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14
Q

What is the structure of the veins and how does this relate to their function?

A

Veins- carry blood back to the heart under lower pressure

  • Wider lumen than arteries
  • Very little elastic and muscle tissue
  • Valves -> prevents back flow of blood
  • Contraction of skeletal muscles squeezes the veins -> maintains blood flow
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15
Q

What is the structure of the capillaries + the importance of capillary beds as exchange surfaces?

A

Capillaries allow gases to be efficiently exchanged between the blood and tissue fluid

  • Wall is thin (one cell thick) of squamous endothelial cells -> short diffusion path for rapid diffusion
  • Capillary bed is made of a large network of branded capillaries -> increases SA:V for rapid diffusion
  • Narrow lumen -> reduces rate of blood flow so more time for diffusion
  • Pores in walls between cells -> allows substances to escape (dealing with infections for example)
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16
Q

What is tissue fluid and its function?

A

Tissue fluid -the fluid surrounding cells/tissues

  • Provides respiring cells with water/oxygen/glucose etc
  • Enables waste substances to move back into the blood (urea. lactic acid + CO2)
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17
Q

How is tissue fluid formed?

A

(start) Nearest arteriole end of capillaries
- There is a higher hydrostatic pressure inside the capillaries (as left ventricle contracts) than tissue fluid
- This forces the fluid out of capillaries into spaces around cells
- Large plasma portions remain in the capillaries as they are too large to leave

18
Q

How does tissue fluid return to the circulatory system?

A

(end) toward the venue end of the capillaries
- Hydrostatic pressure reduces as tissue fluid leaves the capillary (also because of friction)
- There is an increasing concentration of plasma proteins due to water loss, this lowers the water potential in the tissue fluid
- Water enters the capillaries from the tissue fluid by osmosis down a water potential concentration
- Excess water is taken up by the lymphatic system and is returned to the circulatory system via the veins (in neck)

19
Q

What are the cause of accumulation of tissue fluid?

A

Low concentration of protein in blood plasma can lead to an accumulation of tissue fluid

  • Water potential in capillary not as low so water potential gradient is reduced
  • More tissue fluid formed at arteriole end
  • Less/no water absorbed into blood capillary by osmosis

High blood pressure can lead to an accumulation of tissue fluid

  • High blood pressure leads to a high hydrostatic pressure
  • Increases outward pressure from arterial end of capillary / reduces inward pressure at venue end of capillary
  • So more tissue fluid formed and less tissue fluid reabsorbed
  • Lymph system is unable to drain the tissues fast enough
20
Q

What are the stages of the cardiac cycle?

A

atrial systole, ventricular systole, diastole

21
Q

What happens in atrial systole?

A

Atrial systole

  • Atria contract -> decreasing volume and increasing pressure inside atria
  • Atrioventricular valves forced open (when pressure in atria is greater than the pressure in ventricles -> causes atrioventricular valves to open
  • Therefore blood pushed into ventricles
22
Q

What happens in ventricular systole?

A

Ventricular systole

  • Ventricles contract from bottom up -> decreasing volume and increasing pressure inside ventricles
  • Semilunar valves forced open (as pressure inside ventricles is greater than pressure inside arteries
  • Atrioventricular valves shut (as pressure inside ventricles in greater than pressure inside atria)
  • As a result blood is pushed out of heart through the arteries
23
Q

What happens in diastole?

A

Diastole

  • Atria and ventricles relax -> increasing volume and decreasing pressure inside the chambers
  • Blood from the veins fills the atria and flows passively to ventricles
  • Atrioventricular valves open (as pressure inside atria is greater than ventricles
  • Semilunar valves shut (as pressure inside arteries is greater than pressure inside ventricles) - this prevents the back flow of blood
24
Q

What is the equation for cardiac output?

A

Cardiac output = heart rate x stroke volume

Cardiac output - amount of blood pumped out of heart per min

Stoke volume - volume of blood pumped by ventricles in each heart beat

Heart rate - number of beats per minute

25
Q

How is heart rate calculated from cardiac cycle data?

A
  • One beat = one cardiac cycle
  • Find the length of one cardiac cycle (human average = 0.83 seconds)
  • Heart rate in beats per min = 60 seconds / length of one cardiac cycle (human average = 72 bpm)
26
Q

How does atheroma result in a heart attack?

A
  • Atheroma causes the narrowing of the coronary arteries
  • This restricts blood flow to heart supplying glucose and oxygen
  • Therefore the heart anaerobically respires -> less ATP produced -> not enough energy for heart to contract -> lactate produced -> damaged caused to the heart
27
Q

What are the risk factors of cardiovascular disease?

A
  • Age
  • Diet high in salt or saturated fat
  • High consumption of alcohol
  • Stressful lifestyle
  • Smoking
  • Genetics
28
Q

Why is high blood pressure a problem?

A

High blood pressure increases the risk of damage to endothelium of artery wall which increases the risk of atheroma and therefore blood clots

29
Q

What is haemoglobin? + structure

A

Found in red blood cells

  • have a quaternary structure, made of four polypeptide chains (2 alpha and 2 beta)
  • each polypeptide chain in haemoglobin contains a haem group with an iron ion (this ion combines with oxygen)
30
Q

What are some adaptations of red blood cells

A

They have no nucleus to be able to contain more haemoglobin + a biconcave shape for a larger surface area for rapid diffusion of O2.

31
Q

How is oxygen loaded, transported and unloaded in the blood?

A
  • Haemoglobin in red blood cells carries and transports oxygen as oxyhaemoglobin
  • Haemoglobin can carry 4 oxygen molecules (one at each hem group)
  • In the lungs there is a high partial pressure of oxygen therefore haemoglobin has a high affinity for oxygen therefore oxygen readily loads/associated with haemoglobin
  • At respiring tissues, there is a low partial pressure for oxygen so it readily unloads and dissociates fro, haemoglobin
  • Also when concentration of CO2 is high, it increases the rate of oxygen unloading
32
Q

What is the shape of the oxygen dissociation curve?

A

S shaped

33
Q

Explain the shape of the oxygen dissociation curve?

A
  • At high partial pressure, haemoglobin is saturated with oxygen
  • At low partial pressure, haemoglobin is less saturated with oxygen

The graph is S shaped because:

  • Oxygen has a low affinity for oxygen when the first molecule binds, so there is a slow increase in saturation
  • After the first molecule binds, the shape of haemoglobin changes therefore it is easier for the second and third oxygen molecules to bind (haemoglobin has a higher affinity for oxygen) as a result there is an increase in rate of saturation
  • After the third oxygen molecule binds, haemoglobin becomes more saturated and the shape changes, making it difficult for the other molecules to bind -> at a high partial pressure, the rate increase percentage of saturation decreases
34
Q

What is the Bohr effect?

A

At high partial pressure or carbon dioxide, pH is lowered and the haemoglobin’s affinity for oxygen reduces as it changes shape

  • this increases the rate of oxygen unloading
  • therefore more oxygen is provided for the muscles and tissues for aerobic respiration
  • this causes the oxygen dissociation curve to shift to the right
35
Q

How can organisms be adapted to their environment by having different types of haemoglobin and oxygen transport properties?

A

When the curve shifts left..

  • Haemoglobin has a higher affinity for oxygen
  • More oxygen associates with haemoglobin more readily at a lower partial pressure but dissociates less readily
  • This is good for animals which live in high altitudes, underground or foetuses (who have little access to oxygen)

When the curve shifts right…

  • Haemoglobin has a lower affinity for oxygen
  • Oxygen dissociates from haemoglobin more readily to respiring cells at a higher partial pressure but associates less readily
  • This is good for organisms which has a high rate of respiration (small/active)
36
Q

What is the role of the xylem?

A

Tissue that transports water in the stem and leaves of the plant

37
Q

What is the cohesion tension theory of water transport in the xylem?

A

Cohesion tension theory: How water moves up the xylem against gravity via trasnpiration stream

  • Water evaporates from the leaves through the open stomata due to transpiration
  • This reduces the water potential in the cell and increases the water potential gradient
  • Water is drawn out of the xylem which creates tension
  • Water has cohesive molecules which pulls water up as a column
  • Any water lost enters the roots via osmosis
  • As water is cohesive it sticks to the edges of the column
38
Q

What are some adaptations of the xylem?

A
  • Hollow and dead so more space for the uptake of water
  • Rigid so will not collapse under low pressure
  • Thick cell walls made of lignin
  • Narrow lumen to increase the height that water can travel due to cohesion tension
39
Q

What is the role of the phloem?

A

Transports organic substances in plants

40
Q

What is the mass flow hypothesis?

A

Involves translocation: Solutes are moved from source to the sink

At the source:
High concentration of sucrose
Active transport transports sucrose from companion cells to sieve tubes in the phloem
This lowers the water potential in the sieve tubes
Therefore water can enter the sieve tubes by osmosis from the xylem (where there is a higher water potential)
So there is an increasing hydrostatic pressure inside the sieve tubes at the source end
This pressure gradient pushes the sucrose from the source to the sink to be stored or used

At the sink:
Low concentration of sucrose
Sucrose is removed to be used up
There is an increasing water potential in sieve tubes
Water leaves the tubes by osmosis
This lowers the pressure inside the sieve tubes

41
Q

What are some adaptations of the phloem?

A
  • Sieve tube elements have no nucleus and few organelles

- Companion cells: carry out living functions for sieve cells in sieve tubes

AQA Biology A level (13 decks)

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