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OCR A-Level Biology > Chapter 8 - Transport in Animals > Flashcards

Chapter 8 - Transport in Animals Flashcards

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1
Q

State 5 reasons why most animals need specialised transport systems.

A
  • high metabolic demands - lots of oxygen and food required and lots of waste products, diffusion over long distances is not enough
  • low SA:V - as orgs get bigger, diffusion distances get bigger and amount of SA available to absorb/remove substances gets smaller
  • hormones/enzymes made in one place but needed in another
  • food digested in one organ system then needs to be transported to every cell for respiration & other uses
  • waste products need to be removed from cells and transported to excretory organs
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2
Q

Describe how diffusion distance, SA, volume and SA:Vol ratio vary with increasing organism size.

A
  • diffusion distances get bigger - there will be more cells between the surface of organism and the inner cells
  • SA gets larger but V grows quicker so the SA:Vol ratio decreases = slower diffusion rate & bigger diffusion distances
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3
Q

Describe how the level of activity of an organism is related to demand for oxygen and glucose.

A
  • high levels of metabolic activity = more energy required
  • energy is released through respiration which requires glucose and oxygen - demand will be higher
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4
Q

Explain how volume is related to demand and SA is related to supply

A
  • as V increases, org get larger - made up of more cells
  • these cells will require glucose and oxygen supply in order to carry out respiration to carry out vital bioprocesses
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5
Q

Explain why supply meeting demand requires adaptations as organisms incerase in size.

A
  • made up of more cells that all require constant and large supply of O and removal of a lot of CO2
  • metabolic rate is usually higher - more respiration needs to occur
  • diffusion distances increase - not possible to supply cells deeper inside the organism through just the surface
  • smaller SA:V ratio - slow diffusion and gases cant be exchanged fast enough or in large amounts
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6
Q

Explain why diffusion alone cannot meet the demands of most multicellular animals but state where diffusion is still necessary in these organisms.

A
  • most MCO too large for transport of substances by diffusion - rate would be too slow due to the low SA:V ratio & large diffusion distances
  • MCO are also more metabolically active so large amounts of oxygen & food need to be transported -diffusion too slow
  • diffusion occurs in specialised exchange surfaces in organisms - alveoli and capillaries - other substances are transported by mass flow
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7
Q

Define mass flow

A

movement of a fluid in bulk in one direction

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8
Q

Define diffusion

A

net movement of particles from a region of higher concentration to a region of lower concentration.

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9
Q

Define circulatory system

A

transport system of an animal

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10
Q

Define open circulatory system

A

circulatory system with a heart but few vessels to contain the transport medium

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11
Q

Define closed circulatory system

A

where blood is enclosed in blood vessels and does not come directly into contact with the cells of the body beyond the blood vessels

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12
Q

What is haemolymph?

A

transport medium in insects

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13
Q

Describe a single circulatory system

A

where blood passes through the heart once in each circulation (eg. fish)

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14
Q

Describe a double circulatory system

A

blood passes through the heart twice in each circulation in two separate circuits:
- deoxygenated blood is pumped by the heart to the lungs
- oxygenated blood is pumped by the heart to the rest of the body

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15
Q

Describe pulmonary circulation

A

passage of blood from right side of the heart through arteries to lungs where it picks up oxygen and is returned to the left side of the heart by veins

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16
Q

Describe systemic circulation

A

passage of blood from left side of the heart through arteries to the capillaries in body tissues where it exchanges O for CO2 and is returned to the right side of the heart by veins

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17
Q

State some examples of organisms with each type of circulatory system.

A
  • open - invertebrate animals (most insects)
  • single closed - fish
  • double closed - birds & most mammals
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18
Q

Describe the general features of circulatory systems

A
  • liquid transport medium that circulates around the system
  • vessels that carry the transport medium
  • pumping mechanism to move fluid around the system
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19
Q

Explain why organisms need mass flow.

A
  • it delivers oxygen and food to cells in the body a lot more rapidly than diffusion does
  • large quantities of oxygen and food are able to be moved at once - large multicellular organisms are highly metabolically active
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20
Q

Describe the features of open circulatory systems.

A
  • very few vessels needed to contain transport medium
  • transport medium pumped from heart into the body cavity of animal
  • transport medium comes into direct contact with tissues and cells (where exchange takes place) & is at low pressure
  • in insects - haemolymph does not carry gases
  • haemolymph does circulate but steep diffusion gradients cannot be maintained for efficient diffusion
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21
Q

Describe the features of closed circulatory systems and what organisms have them.

A
  • blood is enclosed in vessels - does not come into contact with cells of the body
  • heart pumps the blood at high pressure through arteries
  • blood returns back to the heart through veins after the exchange at capillaries in tissues
  • amount of blood flowing can be adjusted by widening/narrowing blood vessels
  • most able to carry gases using haemoglobin
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22
Q

Describe the features of single closed circulatory

A
  • blood travels once through the heart for each complete circulation
  • blood passes thru 2 sets of capillaries before returning to heart
  • first set - exchanges O2 and CO2
  • second set - substances exchanged between blood and cells in diff organ systems
  • blood returns to the heart slowly bc it passes thru 2 sets of very narrow vessels the pressure drops considerably - efficiency of exhange processes relatively low
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23
Q

Describe how the single closed circulatory system of a fish

A
  • fish have efficient single circulatory system and can be very active bc:
  • countercurrent gas exchange system in gills maintains steep conc gradient for diffusion of oxygen
  • body weight supported by water & they do not maintain their own body temp - lower metabolic demands so no need for double circ
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24
Q

Describe the features of a double closed circulatory system and state which animals have them.

A
  • blood travels through the heart twice per circuit
  • involves two separate circulations:
  • blood pumped from heart to lungs to pick up oxygen and unload CO2 and then returns to the heart
  • blood flows thru the heart and is pumped out to travel around body to deliver oxygen and pick up CO2 before returning to the heart again
  • each circuit passes thru one capillary network so high pressure and fast blood flow maintained - most efficient system for transporting substances
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25
Q

List in order the sequence of blood vessel types that blood passes thru once it leaves the heart.

A

artery - arteriole - capillaries - venule - vein

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26
Q

Define lumen

A

inside space of a tubular structure, such as an artery or intestine.

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27
Q

State the names of anatomical layers in blood vessels & what they are composed of.

A
  • tunica intima - endothelium (thin squamous cells)
  • tunica media - smooth muscle and elastic fibres
  • tunica externa - connective tissue with collagen fibres
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28
Q

State properties and functions of endothelium in blood vessels.

A
  • smooth – minimises friction
  • thin – can be a good exchange surface if nothing else gets in the way
  • there can be gaps between cells for filtration (and allowing WBCs into tissues)
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29
Q

State properties and function of smooth muscle tissue.

A
  • can contract or relax - change diameter of lumen which adjusts how much blood flows down from which blood vessel & regulates blood pressure
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30
Q

State properties & function of elastic fibres in blood vessels.

A

can stretch and recoil – stretching copes with high blood pressure, recoiling maintains the blood pressure. Both stretching and recoiling result in an evening out of surges in blood flow.

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31
Q

State properties and function of connective tissue with collagen fibres in blood vessels.

A
  • inelastic, flexible and high tensile strength – prevents blood vessels increasing in diameter too much when blood pressure is high.
  • protects blood vessels from physical damage (e.g. rubbing against other organs).
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32
Q

Compare the relative proportions of elastin fibres, smooth muscle and collagen in the aorta, medium-sized arteries and arterioles.

A
  • aorta has most elastic fibres bc blood pressure is high and pulses need evening out - pumps blood directly from heart to body
  • medium arteries and arterioles have more smooth muscle tissue than aorta bc these are the blood vessels where redirecting blood flow is important
    (stressed vs relaxed states, hot vs cold) vasoconstriction and vasodilation
  • aorta has most connective tissue with collagen to prevent aorta from widening due to high pressure and preventing from damage from rubbing against other organs because of surges of blood, medium sized arteries have less collagen because they have more smooth muscle
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33
Q

State the width of the aorta, medium-sized artery and arteriole

A
  • aorta: 2.5cm
  • medium-sized artery: 0.4cm
  • arteriole: 30μm
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34
Q

Describe the structure of capillaries

A
  • single layer of endothelial cells with gaps in between
  • lumen is very small - just enough for erythrocytes to travel in single file line
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35
Q

Describe how capillaries are adapted for their function

A
  • large surface area for diffusion of substances in/out of blood
  • walls are single endothelial cell thick - thin layer for diffusion - small diff distance
  • total cross sectional area of capillaries greater than arteriole so blood flow rate falls - blood moves more slowly giving more time for exchange of substances by diffusion
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36
Q

Describe how veins are adapted for their function

A
  • function: carry low pressure deoxygenated blood (except pulm vein) to the heart
  • thin walls - no need for resistance to pulse because surges from heart are lost as blood passes thru capillaries
  • large lumen to allow more blood to flow with less vessel resistance because it is at low speed & pressure
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37
Q

Describe the function of valves in veins and explain how they work

A
  • prevent backflow of low pressure blood
  • flaps of inner lining of vein
  • when blood flows in direction of the heart, the valves are open so blood can pass thru, if it flows backwards they close
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38
Q

Describe 3 adaptations that enable the body to return low pressure blood to the heart against gravity

A
  • veins have one-way valves at invervals
  • bigger veins run between big active muscles so when they contract they squeeze the veins forcing blood towards the heart
  • breathing movements of chest cause pressure changes, squeezing actions move blood in the veins of the chest and abdomen to the heart
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39
Q

Compare the function of arteries, capillaries and veins

A

arteries: carry blood away from heart under high pressure
capillaries: carry blood slowly through tissues - allow exchange of materials with the cells
veins: carry blood back to heart under low pressure

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40
Q

State whether blood is oxygenated or not in arteries, capillaries and veins

A

arteries: oxygenated (except pulmonary artery)
capillaries: oxygenated in systemic, deoxygenated in pulmonary circulation
veins: deoxygenated (except pulmonary vein)

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41
Q

Compare the lumen diameter of arteries, capillaries and veins

A

arteries: relatively narrow
capillaries: approx. RBC thick
veins: relatively wide

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42
Q

Compare the wall structure of arteries, capillaries and veins

A

arteries: thick, endothelium, lots of elastic fibres & smooth muscle, a lot of connective tissues
capillaries: one cell thick, thin endothelial cells
veins: thin, endothelium, little smooth muscle & elastic fibres, lots of collagen

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43
Q

State whether the arteries, capillaries and veins have valves

A

arteries: no (except start of aorta & pulmonary artery)
capillaries: no
veins: yes

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44
Q

Describe the processes of vasoconstriction and how this affects blood flow through capillaries.

A

smooth muscle in arteriole contracts & constricts the vessel preventing blood flowing into a capillary bed

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45
Q

Describe the processes of vasoconstriction and how this affects blood flow through capillaries.

A

smooth muscle in arteriole relaxes & dilates the vessel allowing blood to flow into the capillary bed again

46
Q

Explain why the heart is called a double pump.

A
  • right side pump sends deoxygenated blood to the lungs to become oxygenated and return to heart
  • left side pump sends newly oxygenated blood around the body
  • these two sides never mix & they work simultaneously
47
Q

Describe the structure of the heart and state what each chamber does

A

consists of four chambers - left and right atria, left and right ventricles
- right atrium receives blood from venae cavae, left atrium receives blood from the pulmonary vein
- right ventricle pumps blood into the pulmonary artery, right atrium pumps blood through the aorta
- made out of cardiac muscle, coronary arteries supply it with blood
- surrounded by inelastic pericardial membranes

48
Q

Name the type of muscle the heart is made out of and describe its features.

A
  • contracts & relaxes in regular rhythm, involuntarily
  • does not get fatigued and need to rest like skeletal muscle
49
Q

Name the blood vessels that supply the heart muscle with oxygen and glucose.

A

coronary arteries

50
Q

State the role of pericardial membranes

A
  • prevent heart from stretching too much from the blood
  • keeps heart fixed in place within chest cavity
  • lubriactes heart to prevent friction with tissues around it
51
Q

Explain why the walls of ventricles are thicker than the walls of the atria

A
  • walls are thicker because they have to pump blood out of the heart
  • atria only receive blood and pass it to ventricles
52
Q

Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.

A
  • left ventricle pumps oxygenated blood round the entire body while the right ventricle only pumps blood to the lungs which is a much shorter distance & also they are smaller
  • left ventricle pumps further so it needs to generate more force during contraction
  • right ventricle pumps to lungs where blood needs to be at lower pressure to prevent damage to thin capillaries in lungs
53
Q

Describe the function of each of the valves and chordae tendinae

A
  • tricuspid valve prevents backflow of blood from right ventricle to right atrium
  • bicuspid valve prevents backflow of blood from left ventricle to left atrium
  • semilunar valves prevent backflow of blood into the heart from pulmonary artery and aorta
  • chordae tendinae - make sure valves are not turned inside out by pressures exerted
54
Q

State location and function of the septum in the heart.

A
  • inner dividing wall of the heart
  • prevents mixing of deoxygenated and oxygenated blood
55
Q

Name the stages in the cardiac cycle and outline what is happening at each stage.

A
  • diastole (atrial and ventricular) - chambers relaxed, filling with blood
  • atrial systole - atria contract and push blood into ventricles
  • ventricular systole - ventricles contract and push blood out thru aorta and pulm artery
56
Q

Compare what happens in atrial systole, ventricular systole and diastole when contracting/relaxing

A

atrial systole: atria contract, ventricles relaxed
ventricular systole: atria relax, ventricles contract
diastole: atria relaxed, ventricles relax

57
Q

Compares the pressure changes in atrial systole, ventricular systole and diastole

A

atrial systole: pressure in atria > ventricles / pressure in aorta > ventricles
ventricular systole: pressure in atria < ventricles / pressure in aorta < ventricles
diastole: pressure in atria > ventricles / pressure in aorta > ventricles

58
Q

Compare the valves in atrial systole, ventricular systole and diastole

A

atrial systole: atrioventricular valve open / semilunar valve shut
ventricular systole: atrioventricular valve shut / semilunar valve open
diastole: atrioventricular valve open / semilunar valve shut

59
Q

Compare the direction of blood flow in atrial systole, ventricular systole and diastole

A

atrial systole: atrium to ventricle
ventricular systole: ventricle to aorta/pulmonary artery
diastole: vena cava/pulmonary vein to atria and ventricles

60
Q

Explain how to work out what is happening in one side of the heart if you know what is happening in the other.

A

the same thing will be happening in the other side of the heart since both work simultaneously.

61
Q

Define myogenic

A

muscle that has its own intrinsic rhythm

62
Q

Define sino-atrial node (SAN)

A

region of the heart that initiates wave of excitation that triggers contraction of heart

63
Q

Define atrio-ventricular node (AVN)

A

stimulates ventricles to contract after imposing a slight delay to ensure atrial contraction is complete

64
Q

Define bundle of His

A

conducting tissue composed of purkyne fibres that passes through the septum of the heart

65
Q

Define purkyne fibres

A

tissue that conducts the wave of excitation from the apex of the heart up the walls of ventricles causing them to contract

66
Q

Describe the sequence of electrical events of the heart beat.

A
  • wave of electrical excitation begins in SAN, causing atria to contract & initiating the heartbeat
  • non-conducting tissue layer (septum) prevents excitation passing directly to ventricles
  • electrical activity picked up by AVN which imposes slight delay before stimulating bundle of His
    bundle of His splits into two branches and conducts wave of excitation to the apex
  • at apex, Purkyne fibres spread out thru walls of ventricles of both sides and spread excitation triggers contracation of ventricles, starting at apex
67
Q

Link the electrical events of the heart beat to events in the cardiac cycle.

A
  • atrial systole - when SAN initiates wave of excitation
  • ventricular systole - as purkyne fibres conduct from apex up the walls of ventricles
68
Q

Explain the importance of the delay in conduction of the AVN

A

permits atria to finish beating so that the ventricles completely fill with blood before they themselves begin to beat

69
Q

Explain the importance of the layer of non-conducting tissue between atria and ventricles

A

so that the atria and ventricles can contract separately so that the heart can maintian pressure needed to work as a pump

70
Q

Define electrocardiogram

A

recording of electrical activity in heart

71
Q

Define tachycardia

A

rapid hearbeat, even, 100+ bpm

72
Q

Define bradychardia

A

slowed, even, less than 60bpm

73
Q

Define ectopic heartbeat

A

when there is an extra beat out of rhthym

74
Q

Define fibriliation

A

very rapid irregular contractions of the muscle fibers of the heart resulting in a lack of synchronism between heartbeat and pulse

75
Q

Define arrhythmia

A

abnormal rhythm of the heart

76
Q

Outline how an ECG is recorded

A
  • electrodes stuck to clean skin
  • electrodes measure tiny electrical differences in your skin which result from electrical activity of the heart
77
Q

Describe what is happening in the heart at each stage of an ECG.

A
  • P-wave - wave of excitation spreads over both atria from SA node causing the atrial muscles to contract
  • PR segment - delay at AV node to allow filling of ventricles
  • QRS complex - wave of excitation spreading up walls of ventricles from the apex, causing ventricles to contract
  • T wave - ventricles repolarise after which - ventricular diastole
78
Q

Describe the structure of haemoglobin.

A
  • globular protein made up four peptide chains
  • each peptide chain has an iron-containing haem prosthetic group
79
Q

Write a reversible equation to show how haemoglobin carries oxygen.

A

haemoglobin (Hb) + oxygen (4O2) <–> oxyhaemoglobin (Hb(O2)4

80
Q

Describe the route oxygen takes from the air in the alveoli to haemoglobin and explain how the concentration gradient is maintained.

A
  • oxygen diffuses from alveoli into capillaries and then into erythrocytes, binding to haemoglobin
  • initially, oxygen levels in the erythrocytes are low - steep conc gradient between inside of erythrocytes and air in alveoli
  • as soon as 1 oxygen binds to a haem group, molecule changes shape and it makes it easier for more oxytgen mols to bind
  • bc oxygen is bound to haemoglobin, free oxygen conc in erythrocyte remains low - steep diff gradient maintained until all haemoglobin is saturated
81
Q

Define partial pressure

A

pressure exerted by a component in a mixture of gases

82
Q

Define affinity

A

strength by which two or more molecules interact or bind

83
Q

Define dissociation

A

process by which mols or ionic compounds separate or split into smaller particles (atoms, ions or radicals) usually in a reversible manner.

84
Q

Define positive cooperativity

A

describes how haemoglobin changes shape after first oxygen binds to it, making it easier for the next oxygen mols to bind

85
Q

Explain how the binding of oxygen affects haemoglobin’s affinity for oxygen and how this explains the shape of the oxygen dissociation curve.

A
  • after the first oxygen molecule binds to Hb, it causes conformational change to Hb - “lag” at the start of the curve
  • new shape causes Hb to have increased affinity for oxygen - steep gradient around middle
  • fourth oxygen molecule is hard to load - plateau at the end bc Hb becomes saturated at high pO2
86
Q

Define the bohr effect

A

effect of CO2 concentration on the uptake and release of O2 by Hb

87
Q

Explain the value of the Bohr effect in the transport of oxygen.

A
  • in respiring tisssues, O2 unloads more readily so more oxygen delivered (bc high CO2 and therefore high H+)
  • in lungs, haemoglobin is able to become saturated more easily - higher proportion of O2 picked up (bc low CO2 and therefore low H+)
88
Q

Describe oxygen dissociation curves for fetal and adult haemoglobin

A

fetal haemoglobin has higher affinity for O2 so able to become more saturated per unit of partial pressure

89
Q

Explain the importance of the difference between oxygen dissociation curves for fetal and adult Hb & explain why it is important to lose fetal Hb after birth.

A
  • fetal Hb has higher affinity for O2 so shift to the left of adult
  • allows oxygen transfer from maternal blood to fetal blood in placenta bc fetal Hb is better competitor for oxygen in placenta
  • if it was the same affinity as adult blood, then little/no oxygen would be transferred to blood of fetus
  • important to lose fetal Hb after birth
  • bc fetal Hb requires lower O2 conc before it can unload O2
  • adult tissues not adapted to that
90
Q

Describe oxygen dissociation curves for llamas and mice

A
  • llama (low partial pressure) - shift to left bc it needs higher affinity for oxygen in order to take in higher proportion of oxygen from atmosphere
  • mouse (high oxygen demand) - shift to right bc it needs to be able to unload higher proporiton of O2 at higher partial pressure of O2
91
Q

List 3 methods of transporting CO2 in the blood

A
  • 5% dissolved in plasma
  • 10-20% combined with amino groups in pp chains of haemoglobin to form carbaminohaemoglobin
  • 75%-85% converted into hydrogen carbonate ions in cytoplasm of RBC
92
Q

Describe what happens when CO2 diffuses from body cells to RBC and forms carbonic acid.

A
  • carbonic acid (formed from reaction between H2O and CO2 catalysed by carbonic anhydrase) dissociates into H+ and HCO3-
  • hydrogencarbonate ions diffuse out of RBC, Cl- ions enter cell to maintain charge - chloride shfit
  • oxyhaemoglobin dissociates under influence of H+ ions - Bohr effect
  • assisted by higher temp and lower pH
  • haemoglobin binds to H+ to form haemoglobinic acid
93
Q

Describe what causes CO2 to leave RBC at the lungs.

A
  • haemoglobinic acid dissociates into H+ and Hb
  • hydrogencarbonate ions diffuse back into RBC and react with hydrogen ions to form carbonic acid, chloride ions diffuse out
  • this is broken down to release free CO2 (carbonic anhydrase) that diffuses out of blood into lungs down a concentration gradient
94
Q

List the components of blood and describe their functions

A
  • plasma - carries other components in blood
  • erythrocytes - carry oxygen and carbon dioxide
  • platelets - fragments of megakaryocytes found in red bone marrow, involved in blood clotting
  • leucocytes - immune response
95
Q

State functions of the blood

A

transport of:
- O2 to and CO2 from respiring cells
- digested food from small intestine
- nitrogenous waste products from cells to excretory organs
- hormones
- food molecules from storage mols to cells that need them
- platelets to damaged areas
- cells and antiboides involved in immune response

other functions:
- maintaining steady body temp
- buffer to minimise pH changes

96
Q

Define blood plasma & state functions of each plasma protein

A

yellow liquid that carries other components: glucose, amino acids, hormones, ions, large plasma proteins
- albumin - maintaining osmotic potential
- fibrinogen - blood clotting
- globulins - transport and immune system

97
Q

Define tissue fluid

A

solution surrounding cells of multicellular organisms
- plasma without red blood cells or plasma proteins

98
Q

Define lymph

A

modified tissue fluid that is collected in the lymph system
- less oxygen and fewer nutrients, contains fatty acids and carries lymphocytes

99
Q

Compare the cells found in blood, tissue fluid and lymph

A

blood plasma: RBC, WBC
tissue fluid: none
lymph: lymphocytes

100
Q

Compare proteins found in blood plasma, tissue fluid and lymph

A

blood plasma: plasma proteins
tissue fluid: none
lymph: low

101
Q

Compare fats found in blood plasma, tissue fluid and lymph

A

blood plasma: low
tissue fluid: non
lymph: present

102
Q

Describe how total cross sectional area of blood vessels varies across the circulatory system.

A

lowest at aorta and vena cava, highest at capillaries

103
Q

Define hydrostatic pressure

A

pressure of blood against blood vessels, generated by contraction of cardiac muscle in heart

104
Q

Define oncotic pressure

A

interaction of hydrostatic and osmotic pressures, driving fluid out of the capillary
- difference between hydrostatic pressure and oncotic pressure

105
Q

Define filtration

A

movement of a fluid and its dissolved substances thru pores in the capillary wall due to the hydrostatic pressure generated by the heart

106
Q

Describe how pressure/hydrostatic pressure varies across circulatory system.

A

highest in arteries, drops in capillaries, keeps dropping in veins

107
Q

Describe how oncotic pressure in capillaries is produced

A
  • plasma proteins give blood in capillaries a high solute potential and a low water potential compared to surrounding fluid
  • as result - water has tendency to move into blood vessels in capillaries from surrounding fluid by osmosis - oncotic pressure
108
Q

Explain the movement of liquid into a capillary

A
  • hydrostatic pressure falls to 2.3kPa as fluid has moved out and pulse is completely lost
  • oncotic pressure is -3.3kPa so it is stronger than hydrostatic pressure and water moves from tissue fluid back into capillaries by osmosis
109
Q

Explain the movement of liquid out of a capillary

A
  • hydrostatic pressure is at about 4.6kPa bc it is still under pressure from surge of blood every time heart contracts
  • it is higher than oncotic pressure so fluid is squeezed out of the capillaries - tissue fluid
  • oncotic pressure is about -3.3kPa due to presence of plasma proteins
110
Q

Describe production of tissue fluid in a capillary bed and the possible routes it will take.

A
  • forms by ultrafiltration of blood plasma thru fenestration in capillary walls at the arterial end bc hydrostatic pressure > oncotic pressure
  • 90% re enters blood by reapsorption at venous end
  • 10% of tissue fluid is drains into system of blind ended lymph capillaries where it is called lymph thru which it eventually returns into blood into right & left subclavian veins
111
Q

Describe the structure and function of the lymphatic system

A
  • system of blind-ended tubes
  • lymph capillaries that carry lymph that is tissue fluid that drained into this system in one direction
  • leads fluid back into blood into left/right subclavian vein
  • lymph nodes along the vessels where lymphocytes build up when necessary to produce antibodies
  • intercept bacteria and other debris from lymph which are egested by phagocytes in nodes
  • one way valves are present, fluid transported by squeezing of body muscles

OCR A-Level Biology (16 decks)

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