Organisms Exchange Subtances With Their Environment Flashcards
1
Q
What affects substances diffusion between organism and surroundings
A
Size and metabolic rate
2
Q
What types of exchange are there, and which exchange does not use these
A
Passive by diffusion, osmosis
Active by active transport
Except heat
3
Q
How is exchange effective regarding surface area and volume
A
Large surface area to volume ratio
4
Q
How do you find the area of a cell
A
Pi x r^2
5
Q
How do you find he volume of a sphere
A
4/3 Pi x r^3
6
Q
What happens to surface area volume ratio as volume increases
A
Decreases
7
Q
What features have large active organisms got as they cannot rely on simple diffusion (would take too long)
A
Flattened shape so no cell ever far from surface
Specialised exchange surfaces, large areas increase surface area:volume ratio
8
Q
What is around cells of multicellular organisms
A
Tissue fluid, mass transport system distributes materials to tissue fluid, return waste product to exchange surface, removed
9
Q
What is Ficks law
A
Rate diffusion (dependent on) SA x concentration difference/distance
10
Q
What are the specialised exchange surface features
A
Large SA:Volume
Very thin (short diffusion pathway)
Selectively permeable
Movement of environmental medium (maintain steep concentration gradient)
Movement of internal medium using transport systems (maintain steep concentration gradient)
11
Q
Why are thin, specialised exchange surfaces inside the organism
A
Easily damaged, dehydrated
Need to move external medium over surface e.g ventilating lungs
12
Q
What SA:V would could slow heat loss
A
Small SA:V
13
Q
What practical was used to test the rate of penetration / diffusion
A
Cresol red gelatine cubes
Different block sizes, timing how long lol dilute hydrochloric acid to penetrate and dissolve the cubes
Smaller cube, faster rate of penetration - acid penetrating cube by diffusion
14
Q
What is the benefit of single-celled organisms
A
Large SA:V, quick gas exchange through cell
Oxygen absorbed by diffusion across their body surfaces, only covered by cell surface membrane
15
Q
What does terrestrial mean
A
Lives on land
16
Q
How is water loss reduced
A
Waterproof covering over whole body surface
Small SA:V minimise water loss
17
Q
How do insects control gas exchange
A
Spiracles, openings in tracheae, can close to reduce water loss, need oxygen so usually closed when at rest
18
Q
What prevents the insects internal network of tubes (tracheae) from collapsing
A
Supported by rings of chitin
18
Q
How does atmospheric air get water to respiring tissues
A
Tracheae divide into tracheoles, extend through all body tissues of insect. Air with oxygen brought directly to respiring issue
19
Q
How do gases leave/enter insect
A
Through spiracles
20
Q
How do gases move in/out of the tracheal system
A
Along diffusion gradient
Mass transport
Ends of tracheoles filled with water
21
Q
How do gases move along the diffusion gradient in the tracheal system
A
Respiring cells cause oxygen concentration in spiracle ends fall, diffusion gradient for oxygen to diffuse all,b tracheae, tracheoles to cells
Respiring cells make CO2, concentration gradient in opposite direction
Air direction more rapid than water, respiratory gases exchanged quickly
22
Q
How do gases move my mass transport in the tracheal system
A
Contraction of muscles in insects can squeeze trachea enabling mass movement of air in/out (ventilation) further speeds respiratory gas exchange
23
Q
What happens to water when an insect is resting
A
Water diffuses out of cells into tracheole ends, oxygen ,use diffuse through water to reach cells, slow process
24
What happens during vigorous exercise
Muscles anaerobically respire, make lactate. Is soluble so lowers water potential of muscle cells, water drawn into muscle cells from tracheae - osmosis
Tracheae water volume decrease reducing cells diffusion pathway
Air gas exchange quicker, more efficient
25
What is the limitation of the tracheal system
For effective diffusion, pathway. Just be short, limits insect size
26
What is the covering like on fish and the SA:V
Waterproof, gas tight covering
| Small SA:V
27
What are the specialised internal gas exchange surfaces in fish
Gills
28
What are fills made of, how does it effect gas exchange and where are they
Thousands of filaments, covered in feathery lamellae each only few cells thick containing capillaries
Ensures large surface area and short diffusion pathway
Behind head
29
What are the gulls covered by
Muscular flaps - operculum
30
How does water go through fish and how does it effect concentration of oxygen and carbon dioxide
Water in through mouth, forced over gills, out through opening on both sides of body
Flow through filaments, lamellae, oxygen can diffuse down concentration gradient between blood and water
Carbon dioxide diffuses in opposite direction, down concentration
31
How does the placing of lamellar on filaments effect surface area
At right angles to filaments, increase fills surface area
32
How does the epithelium effect diffusion
Is thin, reduce diffusion distance between blood and water
33
What is the countercurrent exchange principle
Blood flows towards front of fish in gill lamellae, water flows towards back
Always higher oxygen concentration in water than blood
Oxygen diffuses across whole lamellae length, steep diffusion gradient kept across whole
80% dissolved oxygen extracted
Equilibrium between oxygen concentration of water and blood never reached
34
How is the gas exchange system useful in leafs
Many plants photosynthesis (and respire), gases made in one process can be used for the other
35
How does the volume and types of gases exchanged vary
Depends on balance between rates of photosynthesis and respiration
36
What process occurs all the time
Respiration
| Photosynthesis can't at night as no light
37
How is a plant leaf adapted to function
Many stomata on lower epidermis, allow gas diffusion in/out, no cells far from stomata, short diffusion pathway
Mesophyll cells have large SA for rapid diffusion
Main gas exchange surface - spongy mesophyll cells in leaf, loosely packed many interconnecting air spaces throughout do gases readily come into contact with them
38
How are plant cells in the leaf adapted to function
Spongy mesophyll layer crate large surface area for diffusion
Upper epidermis - transparent, sun,Igbo reach chloroplasts
Chloroplasts in palisade mesophyll can move near surface, maximise light absorption
Palisade cells packed tightly together for mass light absorption
Waxy cuticle, guard cell reduce water loss
39
What is the photosynthesis equation
Carbon dioxide + water -> glucose + oxygen
40
What is the respiration equation
Glucose + oxygen -> carbon dioxide + water
41
What and where are stomata and what do they do
Minute pores, occur on leaves, especially underside
Each surrounded by pair of guard cells
Open/ lis control rate gas exchange and water loss
42
What causes stomata to open
When potassium ions actively transported into guard cells, lower water potential of surrounding cells
Water moves in - osmosis
Guard cells become turgid, stomata open
43
What causes stomata to close
When potassium ions actively transported out guard cells, lower water potential of surrounding cells
Water moves out by osmosis (down concentration gradient)
Cells become flaccid, stomata closes
44
What is the human gas exchange system structure like
All aerobic organisms require constant oxygen supply release energy - ATP during respiration, CO2 made in process needs to be removed as built up could be harmful to body
Oxygen volume that needs to be absorbed, volume CO2 must be removed in large mammals
45
Why must CO2 be removed in large mammals
Relatively large organisms wi h large volume of living cells
| Maintain high body temperature, related to them having high metabolic and respiratory rates
46
Why are lungs inside
Air not dense enough support, protect delicate structures
| Body would lose lots water, dry out
47
How are the lungs supported/protected
Bony box - rib cage
48
What protected the alveolus from da,axe as mucus made by goblet cells
Cells lining trachea and bronchus
49
How is the mucus moved to be swallowed
Ciliated epithelium cells have tiny hairs that waft mucus, swallowed
50
What are the bronchi, how are they supported
Two divisions of trachea, lead to one lung structure to trachea
Larger bronchi supported by cartilage but amount reduces as get smaller
Have ciliated epithelium and goblet cells
51
Where are the external intercostal muscles
Outside rob age
52
Where are the internal intercostal muscles
Inside ribcage
53
What are trachea, how are they supported and what are they made of
Flexible airways supported by cartilage rings, stop it collapsing
Tracheal walls ,are of muscle lined with ciliated epithelium and goblet cells
54
What are bronchioles and what are they made of
Series of branching subdivisions of bronchi
Walls are muscle lined with epithelial cells
Allows them to contract controlling air flow in/out alveoli
55
What do goblet cells produced and why is this useful
Make mucus to trap dirt particles and bacteria, cilia move mucus up throat passes down oesophagus to stomach, swallowed
56
What are alveoli, what is their function and how is this useful
Minute air sacs found at ends of bronchioles
Contain collagen and elastic fibres lined with epithelium elastic fibres, can stretch when filled with air, spring back (recoil) to empty
Gas exchange occurs at alveoli surface
57
What is the rib cages function and how does it move
Protect lungs, moved by intercostal muscles between them
58
What is the diaphragm
Muscle sheet, separates thorax and abdomen
| Relaxes and contracts
59
What are the lungs
Loved structures specialised for gas exchange
60
What is the pulmonary ventilation equation
Pulmonary ventilation=tidal volumexbreathing rate
| dm^3min^-1 dm^3 min^-1
61
What occurs in inspiration
External intercostal muscles and diaphragm muscles contract
Rib cage moves upwards and outwards, diaphragm flattens
Volume of thorax increase
Lung pressure decrease (below atmospheric pressure) air flows into lungs
Active process - needs energy
62
What occurs in expiration
Internal intercostal muscles contract only up during strenuous activity and external intercostal muscles and diaphragm muscles relax
Rib cage moves downwards and inwards, diaphragm becomes curved again (pushed up by abdomen contents)
Volume of thorax decrease
Lung pressure increase (above atmospheric pressure) air forced out lungs
Passive process
63
Why is residual air needed
Remains in lungs to stop alveolus sticking together
64
What is pulmonary ventilation
Total volume air loved into lungs in one minute
65
What is tidal volume
Volume of air moved into lungs in one breath (changes in strenuous activity)
66
What is ventilation
Breathing rate - number breathes taken in one minute
67
How does oxygen get to blood
Passes through sing,e layer alveoli epithelium, the. Single layer of endothelical cells of blood capillaries
68
What is diffusion
Particles in fluid move from high concentration to low, till evenly distributed
69
How is material efficiently transferred by diffusion/active transport
Large SA:V speed rate of exchange
Partially permeable allow selected materials easily diffuse
Movement of internal medium
Movement of environmental medium
Thin for short diffusion pathways, cross rapidly
70
What is the role of alveoli in gas exchange
Each alveolus has network of capillaries, so narrow red blood cells flattened against thin capillary wall to fit through
Walls of capillary single cell thick
71
How are body cells adapted for short diffusion pathway
Distance between alveolar air and red blood cells reduced as red blood cells flattened
Walls of both alveoli and capillaries very thin, short diffusion distance
72
How are body cells adapted for steel concentration gradient
Breathing movements always ventilate lungs, action of heart always circulates blood round alveoli ensure steep concentration gradient from gas exchange
Blood flow through pulmonary capillaries maintains concentration gradient
73
How are body cells adapted for large SA:V
Alveoli and pulmonary capillaries have very large total surface area
74
How is diffusion time increases
Red blood cells slowed as pass through pulmonary capillaries
75
What are correlations and casual relationships
Sometimes cannot know fro, data if the thing is a cause, ,au suggest but with no real evidence. Needs clear casual connection, as could be a different factor causing it. So experimental evidence to show distinct correlation
76
What are the risk factors offer lung disease, the chromic obstructive pulmonary disease
Smoking, 90% people suffering COPD are/were heavy smokers
Air pollution, pollutant particles, gases e.g So2, especially in heavy industry areas
Genetic makeup, some genetically more likely to, why non smokers get lung disease
Infections, frequently get chest infections, build up scar tissue, higher COPD
Occupation, harmful chemicals, gases, dusts inhaled increase risk
77
What lung diseases are there
Pulmonary fibrosis
Asthma
Emphysema
78
Why does pulmonary fibrosis arise
When scars on epithelium form, so irreversibly thickened, reduce lungs elasticity
79
What are the symptoms of pulmonary fibrosis
Shortness of breath, especially when exercising, due to considerable air space in lungs occupied by fibrous tissue - less air in lungs in each breath (affects concentration gradient)
Chronic dry cough, pain/discomfort to chest, weakness/fatigued to reduce respiration
80
How does pulmonary fibrosis effects rate of diffusion
Scar tissue increases diffusion pathway
| Less air in lungs in each breath affects concentration gradient
81
How is asthma caused
By one/more allergens, white blood cells of bronchi/bronchioles release chemical - histomine
Lining of airways inflamed epithelial cells of airway make mucus
Muscles round bronchioles contract, constrict airway
82
What are the symptoms of asthma
Difficulty breathing, wheezing, tight feeling in chest, coughing
83
How does asthma effect rate of diffusion
Narrow airways reduce efficient ventilation, reduces concentration gradient
Mucus reduces bronchioles surface area, less oxygen diffusing into cell
84
How is emphysema caused
By smoking, 1 in 5 smokers
Disease develops over 20 years is irreversible
Alveoli contain lots elastic tissue containing protein - elastin
Tissue stretches alveoli when breathe in, recoils when breathe out, permanently stretched can't recoil
85
What are the symptoms of emphysema
Shortness of breath (reduces surface area and decreases ventilation)
Chronic cough
Bluish skin colouration - oxygen lack
86
How does emphysema affect rate of diffusion
Reduced expel CO2, affects concentration gradient, less air in/out
Alveoli walls destroyed, surface area reduced
87
Where are the salivary glands and what do they do
Near mouth, pass secretion via duct into mouth
| Secretions contain amylase to hydrolyse starch to maltose
88
How does the oesophagus carry food from the mouth to stomach
Peristalsis
89
What is the pancreas and what does it do
Large gland below stomach
| Produces secretion - pancreatic juice
90
What does the pancreatic juice contain
Proteases to hydrolyse proteins
Lipases to hydrolyse lipids
Amylase to hydrolyse starch
91
What else other than pancreatic juice does the pancreas make
Insulin
92
What is the stomach and what does it do
Muscular sac with inner layer that makes enzymes
Stores and digests food especially protein
Glands make protease to digest protein
93
What does the large intestine do
Absorb water
| Most secretions of many digestive glands
94
What does the small intestine (ileum) and what does it do
Long muscular tube
| Further food digested by enzymes made in its walls and glands
95
How is the ileum adapted for absorption and digestion into the bloodstream
Inner ileum walls folded into villi, large surface area, increased by microvilli, on epithelial cells of each villus
96
What does the rectum do
Final section of intestines
| Faeces stored and removed via anus - egestion
97
What is physical digestion and how is it beneficial
Large food broken to small pieces by structures e.g teeth
| Provides large surface area for chemical digestion, helps ingest food, also churned by muscles in stomach wall
98
What is chemical digestion
Hydrolysis large insoluble molecules into small soluble ones, carried out by enzymes
All digestive enzymes function by hydrolysis
99
What is carbohydrases for
Hydrolyse carbohydrates ultimately to monosaccharides
100
What are lipases for
Hydrolyse lipids into glycerol and fatty acids
101
What are proteases for
Hydrolyse proteins ultimately into amino acids
102
How are carbohydrates digested
1. Physical digestion, salivary amylase hydrolysis starch to maltose, mineral salts for neutral pH - amylase optimum
2. Swallowed, acidic stomach denatures amylase stop hydrolysing
3. Small intestine - pancreatic juice has pancreatic amylase hydrolysis remaining starch, alkaline salts maintain neutral pH
4. Ileum wall muscles push food along. Epithelial lining makes maltase, hydrolysis maltose into alpha glucose
103
What produces alkaline salts in the carbohydrate digestion system and why
Saliva in mouth has mineral salts and pancreas intestinal wall make alkaline salts to maintain neutral pH for amylase to function
104
What happens in lactase hydrolysis and what's made
Hydrolyses single glycosidic bond in lactose
| Makes alpha glucose and galactose
105
What happens in sucrase hydrolysis and what's made
Hydrolyses single glycosidic bond in sucrose
| Makes alpha glucose and fructose
106
Where are sucrose and lactose found
Wall of small intestine
107
What digests proteins
Peptidases
108
What do endopeptidases do
Hydrolyse bonds between amino acids in central region of protein, form series peptide molecules
109
What do exopeptidase do
Hydrolyse peptide bonds on ends of smaller polypeptide chains made by endopeptidases
Progressively release dipeptides, single amino acids
110
What do dipeptidases do
Hydrolyses bond between two amino acids in central region of protein, make series of peptide molecules
111
How are lipids digested and what is formed
Lipids hydrolysed by lipases (made in pancreas) hydrolyses ester bond in triglycerides to make fatty acids and monoglycerides
112
What is a monoglyceride
Glycerol with single fatty acid
113
How are lipids first spilt into tiny droplets (what are these called) and how does this affect lipases speed
Tiny droplets - micelles by bile salts made in liver
| Is an emulsification, increases lipids surface area so action of lipases speed up
114
How are lipids digested in small intestine
1. Bile salts in liver released into small intestine from gall bladder, break lipids to small droplets - emulsification (increases SA for enzymes)
2. Lipases digest lipids to fatty acids and monoglycerides, these remain stuck with bile salts - micelles
3. Micelles contact with epithelial cells of small intestine, break down release fatty acid and monoglycerides (non polar) fat soluble, diffuse through phosoplipid bilayer of epithelial cells, travel to endoplasmic reticulum
4. Go to Golgi body, triglycerides join with cholesterol and lipoproteins - chylomicrons, released from epithelial cells by exocytosis, pass into capillaries of lymphatic system - lacteals into blood
5. Here triglycerides in chylomicrons hydrolysed by enzyme in endothelial cells of blood capillaries
6. Release fatty acids and monoglycerides, diffuse out capillaries into cells, used
115
Where are bile salts made and where are the release into and from
Made in liver
| Released into small intestine from gall bladder
116
What do bile salts do to lipids
Break lipids up into small droplets - emulsification
| Increases surface area for enzymes
117
What are micelles
Monoglycerides and fatty acids stuck to bile salts
118
Why can monoglycerides and fatty acids diffuse through phosoplipid membrane
They're non polar, fat soluble
119
What are chylomicrons and how are they release from epithelial cells
Triglycerides combined with cholesterol and lipoproteins
| Released from epithelial cells by exocytosis
120
What happens to chylomicrons when they pass through lymphatic system
Triglycerides in chylomicrons hydrolysed by enzyme on endothelial cells of blood capillaries
Fatty acids and monoglycerides diffuse into cells
121
How is the ileum adapted for absorption
Small intestine wall folded, has finger-like projections - villi
Epithelial cells have microvilli on other side blood capillary network
Villi increase surface area, accelerate absorption
122
Where are the villi
Interface between lumen of intestines
123
How is a concentration gradient created for blood diffusion
Usually make products of digestion in small intestine than blood
Blood always circulated so product of digestion removed
Villi contain muscles, contract and relax, mixing contents of small intestine
124
Where is active transport in absorption
Co-transport, facilitated diffusion,
125
How do the villi affect ficks law
Thin walled - thin diffusion pathway
Regularly contract, relax mix contents of small intestine - concentration gradient
Wall covered in folded villi and microvilli - large surface area
Good blood supply - concentration gradient
126
Why are there usually more products of digestion in the small intestine than blood
Proteins and carbohydrates always digested, usually more products of digestion in small intestine
127
How does the amount of products being higher in the small intestine than blood affect where the products of digestion diffuse
Creates a concentration gradient for products of digestion to diffuse into the blood
128
How is the concentration gradient between blood and small intestine kept
Blood always circulated so products of digestion removed
129
How is the contents of the villi mixed, what effect does this have
Villi contain muscles, contract, relax so mix contents of small intestine so maintain concentration gradient
130
Why is not all available glucose absorbed
May pass out of body
131
Why do glucose and amino acids need to be transported
Or concentrations either side of the intestinal epithelium equal
132
How are sodium and glucose molecules moved into cell
Sodium - down concentration gradient
Glucose - against concentration gradient
Sodium powers glucose movement into cells rather than ATP
Indirect active transport (co-transport)
133
How is sodium removed from the cell
Through sodium potassium pump - active transport
Low concentration in cell, moves jerk blood capillary
Potassium ions move into cell
134
How is glucose moved out of the cell
Moved into a blood capillary by facilitated diffusion
135
How are villi adapted to Ficks law
Thin walled - short diffusion distance
Micro-villi - increase SA
Regularly contract mixing contents- concentration gradient
Well supplied blood vessels - concentration gradient
136
How do transport systems affect diffusion
Create larger organisms smaller surface area:volume
| Longer distance for diffusion, not as rapid
137
What does blood transport
Oxygen, carbon dioxide, hormones, idea, glucose, amino acids
138
What is blood made up of
55% plasma
| 45% red blood cells, platelets and white blood cells
139
What is plasma
Straw coloured liquid, carries hormones, nutrients, urea, (heat)
140
What do red blood cells art
Carry oxygen and carbon dioxide
141
What is another word for red blood cells
Erythrocytes
142
What do platelets do and carry
Form scabs
| Carry carbon dioxide
143
What are white blood cells for
Immunity
144
How are RBC SA:V adapted for function
Large SA:V lots of oxygen can diffuse at fast rate through outer surface to cell centre
145
How is RBC size adapted for function
Small in diameter and relatively thick, can fit through capillaries one at a timme
146
How does RBS shape adapted for function
Biconcave discs increases surface compared to inside volume even more
147
How is the adaption of RBC having no nucleus benefit
Before RBC leaves bone marrow (where made) and enters blood, nucleus breaks down so more room for haemoglobin
148
How is oxyhaemoglobin formed and where
In lungs 0: oxygen + haemoglobin -> oxyhaemoglobin
149
How does oxyhaemoglobin break down and where
Tissues: oxyhaemoglobin -> oxygen + haemoglobin
150
What structure do haemoglobin have and how does effect (un)/loading of oxygen
Quaternary structure, evolved to make loading and unloading of oxygen efficient
151
What is the quaternary structure of haemoglobin
All 4 polypeptides are linked to form almost spherical molecule polypeptide is associated with haeme group containing Fe^2+ ion
152
What are the subunits in haemoglobin
2 alpha and 2 beta
153
What does each subunit contain
A haeme group (inorganic prosthetic iron group)
154
How does oxygen combine with a haemoglobin molecule
Binds to the iron in subunit
| Can carry 4 oxygen molecules
155
What must haemoglobin be to be efficient at transporting oxygen
Readily associate with oxygen where loading occurs - lungs
| Readily dissociate where unloading occurs - tissues
156
Why is the pO2 low at the start of the oxygen dissociation curve
Low pO2 of Hb saturation is low
| pO2 increase there is an in increase in in oxygen saturation, slow at first
157
When does oxygen associate with Hb easier
When oxygen concentration high, higher saturation percentage
158
When does oxygen dissociate from Hb
When Hb low concentration so lower percentage saturation
159
Why does oxygen unload in tissues
Lower pO2 so Hb gives up some oxygen- unloads
160
Why is it difficult to load oxygen at start of oxygen dissociation curve
At very low oxygen concentration, 4 polypeptide chains of Hb molecule closely united so difficult to absorb first oxygen molecule
161
Why does the oxygen dissociation curve increase rapidly after one oxygen molecule has combined to the Hb
Causes polypeptides to load remaining 3 oxygen molecules easily as first one changes quaternary structure to make it easier for oxygen to bind. Smaller increase in pO2 needed to bind second oxygen molecule - positive co-operativity, so steeper gradient
162
Why does the oxygen dissociation curve plateau at the end
High pO2 as Hb saturated with oxygen. After binding third oxygen molecule, while easier to bind to fourth, most binding sites occupied so less likely to get empty space
163
What is partial pressure of oxygen (pO2)
Amount of gas present in mixture measured by pressure it contributes to total pressure of gas mixture
Measured in kilopascal (kPa)
164
How does the environment affect haemoglobin in different organisms
In low oxygen areas, oxygen dissociation curve shifted to left
Hb can become fully saturated even at low pO2 of oxygen
Only effective if organism has low metabolic rate
165
How does the size effect haemoglobin in different organisms
Small organisms have large SA:V, lose heat rapidly, keep constant body temperature, high respiration rate, need lots oxygen so readily unloaded at higher pO2, shifts right
166
How does activity affect haemoglobin in different organisms
Active organisms have high respiration rates, oxygen unloaded readily in respiring tissues. Curve shifts right
167
How does carbon dioxide affect haemoglobin in different organisms
Higher concentrations, Hb bind more loosely so Hb releases oxygen, CO2 acidic and low pH causes Hb to change shape
168
What is the Bohr effect
Carbon dioxide and water form carbonic acid which dissociates to give hydrogen ions. Decrease pH (more acidic) hydrogen ions bind with Hb, causes a decrease in oxygen affinity.
169
Why does Hb have a reduced affinity for oxygen when carbon dioxide is present
Greater the carbon dioxide the more readily oxygen dissociates
170
Why is oxygen affinity high at gas exchange surface, why does this cause the oxygen-dissociation curve shifted to the left.
At gas exchange surface (lungs) CO2 is low, diffuses across exchange surface, expelled. Oxygen affinity of Hb is high, coupled with high concentration of oxygen in lungs, oxygen readily loaded by Hb.
171
Why is oxygen readily unloaded in respiring tissues, and why does this cause the oxygen-dissociation curve to shift to the right
In rapidly respiring tissue (muscles) level of CO2 is high, affinity of Hb for oxygen is less, low concentration of oxygen in muscles, readily unload
172
How is a high pH achieved at the lungs and why is this good
CO2 constantly removed, pH raised due to low amount. Higher pH changes Hb shape so oxygen is more readily loaded, increases affinity of Hb for oxygen
173
Why does CO2 lower the pH
Is acidic in solution, so pH of blood in tissues lowered, changes Hb shape to one with lower oxygen affinity, unloads
174
How do single celled organisms exchange materials between them and environment
Over body surface
175
WHy can't larger organisms exchange materials between them and the environment over their body surface
Increase of size, surface area:volume decreases, need of organism can't be met by only body surface
176
What are specialist exchange surfaces needed for
to absorb nutrients and respiration gases, removes excretory products
177
What makes the transport system more essential for larger organisms
As organisms evolved to larger, more complex structures, tissues and organs that they're made of become more specialised and dependent of each other
178
What causes organisms transport systems to need a pump
Lower SA:V, and more active organism is, greater need for specialised transport
179
What medium is used to carry materials
Normally liquid based on water, as readily dissolves substances, easily moved, can be a gas
180
How does transport medium reach all parts of organism
Closed system of tubular vessels that contain the transport medium and form branched network to distribute to all part of organism
181
What mechanism causes medium in vessels to be moved
Pressure difference between one part of the system and another.
Muscular contraction for animals/specialised pumping of organ (heartPlants rely on passive physical process - evaporation of water
182
What mechanism maintains mass flow movement in one direction
Valves
183
What is the double circulatory system in mammals
closed, double circulatory system
184
What is the double sirculatory system
blood confined to vessels, pass through heart, when blood passed through lungs, pressure reduced. If past to rest of body straight away, low pressure would make circulation slow
blood returns to heart to boost pressure before circulated to rest of tissues
185
Why must blood be pumped round to rest of the heart quickly in mammals
High body temperature, so high heart rate of metabolism
186
What are the vessels that make up the circulatory system of a mammal
Arteries
Veins
Capillaries
187
What system is used to transport substances longer distances. What is the final part of the journey into the cell
Transport system
| Final part of he journey into the cells is by diffusion
188
Why is the exchange from blood vessels to cells rapid
Takes place over a large surface area, across short distances and there is a steep diffusion gradient
189
What is the function of the arteries
Transport blood rapidly under high pressure away from heart, into arterioles
190
What is the function of the arterioles
Smaller arteries that control blood flow (through their muscle layer) from arteries to capillaries
191
What is the function of the capillaries
Tiny blood vessels that link arterioles and veins, exchange metabolic materials e.g oxygen
192
What is the function of veins
Carry blood slowly from capillaries to heart under low blood pressure
193
What are the layers (from outside inwards) of arteries, arterioles and veins
```
Tough outer layer
Muscle layer
Elastic layer
Thin inner lining (endothelium)
Lumen
```
194
What is the tough outer layer for
Resists pressure changes from in and out
195
What is the muscle layer for
Can contract, control blood flow (especially important for arterioles)
196
What is the elastic layer for
Helps maintain blood pressure by stretching/springing back (recoiling)
197
What is the lumen for
Central cavity through which blood flows
198
What causes valves to close, preventing blood backflow
Blood flowing away from heart pushes valves closed, so blood is prevented from flowing further in direction
199
Which blood vessel has the thickest muscular layer
Arterioles
200
Which blood vessel has the thickest elastic layer
Arteries
201
Why do the arteries have relatively thick muscular layer (compared to veins)
Means smaller arteries can be constricted and dilated in order to control volume blood passing through
202
Why do arteries have a thick elastic layer (compared to veins)
Important for blood pressure in arteries kept high if to reach extremities of body
Elastic wall is stretched at each beat of the heart
203
Why is the overall thickness large in arteries
Resists vessel bursting under pressure
204
Why do arteries have no valves (except leaving the heart)
Blood under constant high pressure due to heart pumping blood into the arteries, doesn't flow backwards
205
Why is the arterioles muscle layer relatively thicker than arteries
Contraction of muscle layer allows constriction of lumen of arterioles. Restricts blood flow, controls movement into capillaries into capillaries that supply tissues with blood
206
Why do arteries have relatively thinner elastic layer
Lower blood pressure
207
Why do veins have a thin muscle layer (compared to arteries)
Veins carry blood away from tissues, constriction and dilation can't control flow into tissues
208
Why do veins have a thin elastic layer
Low blood pressure in veins, won't cause them to burst, pressure too low to create recoil
209
Why is the overall thickness of veins small
Don't need to be thick as pressure in veins too low to create risk of bursting. Can be flattened easily,aiding blood flow
210
Why do veins have valves throughout
Ensure blood doesn't flow back, which could otherwise as low pressure when body muscles contract, veins compressed, pressure blood in.
Ensure pressure directs blood only to heart
211
Why is there a slow blood flow in capillaries
Gives time for materials to diffuse
212
What is the final journey of metabolic substances
Metabolic substances made in liquid solution that bathes tissues - tissue fluid
213
What is the important exchange surface in capillaries
Capillary bed
214
How are capillary walls adapted to short diffusion distance
Is endothelium lining (one cell thick) so extremely thin, short diffusion distance, rapid diffusion between blood and cells
215
How do capillaries provide large surface area
Highly branched
216
Why is no cell far from capillaries
Narrow diameter so can permeate tissues
217
What causes red blood cells to be squeezed flat
Narrow lumen so red blood cells are squeezed flat against capillary side, closer to cells to which they supply oxygen, reduces distances, slows flow
218
What does the reduces diffusion distances and slow blood flow cause
Increases diffusion time
219
How do white blood cells escape from capillaries and why
Through spaces in endothelial lining cells
| Deal with infections in tissues
220
What substances does tissue fluid carry
Watery liquid containing glucose, amino acids, fatty acids, salts, oxygen
221
What substances does tissue fluid recieve
Carbon dioxide, waste materials from tissues
222
What does the tissue fluid do
Bathes cells of body, exchanges materials between blood and cells
223
What is tissue fluid formed by
Blood plasma, controlled by homeostatic mechanisms, providing a constant environment to cells near
224
What is the formation of tissue fluid
Blood gradually moves, narrowing vessels to capillaries, pressure forms - hydrostatic pressure
225
How is tissue fluid removed from blood plasma
Pressure found at arterial end of capillaries, forces tissue fluid out of blood plasma into tissues
226
What is ultrafiltration
Capillaries hydrostatic pressure is only enough to force small molecules out (cells and proteins remain in blood)
Filtration under pressure
