Organisms Exchange Subtsances With Their Environment (3.3) Flashcards
1
Q
What materials need to be exchanged?
A
- Respiratory gasses (oxygen, carbon dioxide)
- Nutrients (glucose, fatty acids, amino acids, minerals)
- Excretory products (urea and carbon dioxide)
- Heat
2
Q
How can exchange take place?
A
Passively (diffusion or osmosis)
Actively (active transport)
3
Q
Simple diffusion of materials across the surface can only meet the needs of a relatively __________ organism. Even if the surface area could supply enough material it would still take too______ for it to reach the middle of the organism.
A
Inactive
Long
4
Q
What are the features of a specialised exchange surface?
A
- large surface area
- thin
- partially permeable
- movement
5
Q
Why is a large surface area to volume ratio a feature of a specialised exchange surface?
A
Increases the rate of exchange
6
Q
Why is being thin a feature of a specialised exchange surface?
A
Provides a short diffusion pathway meaning materials can cross the exchange surface rapidly.
7
Q
Why is being partially permeable a feature of a specialised exchange surface?
A
It allows selected materials to cross without obstruction.
8
Q
Why is movement a feature of a specialised exchange surface?
A
Movement of an environmental medium maintains a concentration gradient e.g blood moves to maintain the concentration gradient.
9
Q
How can you calculate diffusion?
A
Diffusion = surface area X difference in concentration
—————————————————————
Length of diffusion pathway
10
Q
Why are exchange surfaces often located in an organism?
A
Because they are easily damaged.
11
Q
Diffusion is sufficient if….
A
The distances are short (less than 0.5mm)
The surface area is relatively large
12
Q
Why do large, active organisms need exchange surfaces?
A
The distances are too great for the materials to reach the centre of the organism.
13
Q
How do you find the volume of a cube/rectangle?
A
Base x height x width
14
Q
How do you find the area of a sphere?
A
4/3 pi r 3
15
Q
How do you find the surface area of a sphere?
A
4 pi r 3
16
Q
How do you find the surface area of a sphere?
A
4 pi r 2
17
Q
If size increases, surface area increases ___________ compared to volume.
A
Disproportionally
18
Q
Large organisms have a ______ surface area to volume ratio.
A
Small
19
Q
Small organisms have a ________ surface area to volume ratio.
A
Large
20
Q
Insects have no blood so they need……?
A
Tubules
21
Q
Why do insects have tubules?
A
To take oxygen to muscle cells
22
Q
What makes an insect’s tubule system?
A
Trachea and tracheoles
23
Q
How does oxygen reach an insets trachea?
A
Spiracles on their surface
24
Q
What are trachea and tracheoles supported by to prevent their collapse?
A
Strengthened rings
25
Why do spiracles close their valves?
To minimise water loss
26
What are the two ways spiracles minimise water loss?
- close spiracles using valves
- there are hairs around the spiracles to trap humid air
27
What are the three ways respiratory gasses move in an insect?
- along the concentration gradient
- contraction of muscles
- movement of water into muscle cells which increases the volume of gasses that can fit into the end of a tracheole.
28
Describe how insects prevent water loss.
- the ends of tracheoles are filled with water.
- during active periods, muscle cells around tracheoles carry out anaerobic respiration.
- this produces a soluble lactate.
- water (containing the dissolved lactate) move into cell from the tracheoles by osmosis, lowering the water potential of the muscle cells.
29
What is the limitation of gas exchange in insects?
It heavily relies on diffusion which requires a short diffusion pathway, meaning the insect has to be relatively small.
30
What protects the gills in a fish?
Operculum/ gill cover
31
How does water get into the fish for gas exchange?
The mouth
32
Describe the movement of water **in** a fish.
Water enters the mouth and **passes over** the gills.
33
Describe 3 features of gills in a fish?
-large surface area provided by *gill lamellae**
- rich blood supply
- counter current flow
34
Why can fish **not** survive out of water?
In water their gills are feathery, increasing their surface area for exchange. When a fish is out of the water their gills collapse down, decreasing their surface area- this reduced ur face area does not allow sufficient gas exchange.
35
What two features of a gill increase the surface area?
Gill filaments
Lamellae
36
What is counter current?
When blood flow passes in the opposite direction to water flow
37
Describe how the blood and water supply interact in counter current ,when they flow in opposite directions.
- oxygen rich blood encounters oxygen rich water
- oxygen poor blood encounters oxygen poor water
38
What would happen if parallel flow occurred in the gills of a fish?
Exchange would reach equilibrium (no longer occur).
39
Why do highly active fish swim with their mouths open?
- they maintain a high rate of water flow across gills to provide sufficient oxygen for a high rate of respiration
40
Why is countercurrent flow import?
It maintains a favourable concentration gradient. (A concentration gradient is maintained across the entire distance of the gill lamella)
41
what makes up the mesophyll layer in a leaf?
Palisade mesophyll
Spongy mesophyll
Air space
42
What makes up the vascular bundle in a leaf cell?
Xylem
Phloem
43
What surrounds the stomata in a leaf?
Guard cells
44
What is the role of the waxy cuticle in a leaf?
Waterproofing and protection
45
what is the role of the palisade mesophyll in a leaf?
- rich in chloroplasts = photosynthesis
- ‘crammed’ = maximum amount of light can be absorbed
- vertical - increasing likelihood of light striking chlorophyll molecules
46
What is the role of the spongy mesophyll in a leaf cell?
It has air spaces to allow gasses to circulate when diffusion to and from the environment
47
What is the role of the vascular bundle in a leaf?
Transport vessels
48
Plant cells respire ___ hours a day.
24
49
Photosynthesis only occurs in________.
Daylight
50
In plants, waste gasses from __________ respiration can be sued for ____________ visa Vera’s.
Respiration
Photosynthesis
51
How is the leaf a specialised exchange surface?
- flat shape provides a large surface area
- stomata allow many routes into/out of the leaf
- spongy mesophyll offers interconnected air spaces
52
What is the singular word for stomata?
Stoma
53
What are stomata?
Tiny pores, surrounded by guard cells, that allow control of gas exchange and water loss by evaporation.
54
How do guard cells open and close stomatal pores?
They manipulate the water potential.
55
How do guard cells **open a stomatal pore**?
- ions move into the guard cells, making the water potential more negative
- water follows by osmosis
- cells become more turgid and the pore opens
56
How do guard cells close to stomata?
- ions move out of the guard cells making the water potential less negative
- water follows by osmosis
- cells become flaccid and the pore closes
57
what is a xerophyte?
A plants which is adapted to live in very **dry** conditions.
58
What is an example of a xerophyte?
Cacti
Marram grass
59
What are some structural adaptations of a xerophyte?
Waxy cuticle - reduce evaporation from epidermis
Long, shallow spread out root system - reaches water supplies on the surface of the ground
Swollen succulent system - store moisture
Leaves reduces to spikes and round shape - reduces surface area:volume which means water isn’t lost
Hairs on surface to reflect light - reduces photosynthesis, reduces demand for water
60
Where is marram grass found?
Sand dunes
61
Name two adaptations of marram grass.
Rolled leaf
Fewer stomata sunken into pits with hairs
62
Why does marram grass have a rolled leaf?
Less surface area which means there are less stomata.
The stomata are internal, trapping humid air.
63
Why does marram grass have stomata with hairs?
The hairs trap humid air, reducing the concentration gradient.
64
What do hinge cells do?
Allow a leaf to roll up when short of water so that stomata aren’t exposed to wind or dry air.
65
Where in the body are the lungs found?
The thorax
66
What two parts connect the lungs to the mouth?
Trachea and bronchi
67
There are __ bronchi in the lungs.
2
68
What provides support and flexibility to the bronchi and trachea?
Many C shaped rings of cartilage.
69
What lines the lumen of the bronchi and trachea?
Ciliated epithelial cells
70
How do the ciliated epithelial cells and goblet cells work together in the bronchi and trachea?
Goblet cells lie in between the epithelial cells. They produce mucus to trap dirt and pathogens. Cilia waft mucus out of the airways.
71
What does the smooth muscle do in the bronchi and trachea?
Controls their diameters
This can reduce air flow e.g when pollen is inhaled.
72
What do bronchioles not have?
Cartilage
73
How many alveoli are in the lungs?
Millions
74
What do alveoli consist of?
Squamous epithelial tissue and elastic fibres.
75
Where does gas exchange occur in the lungs?
Alveoli
76
Where does gas exchange occur in the lungs?
Alveoli
77
Alveoli have a large _______ _____ and a good _______ supply, this maximised gas exchange.
Surface area
Blood
78
Alveoli have a short diffusion pathway that is 2 cells thick. What are these cells?
Squamous epithelia of the alveoli. The endothelia of the walls of the blood vessels.
79
What is pulmonary fibrosis caused by?
Damaged alveoli cause lungs to become stiff and thick scar tissue on alveoli, increasing the diffusion pathway making it difficult for 02 to get into the blood.
80
what are the risk factors that can cause pulmonary fibrosis?
Smoking
Acid reflux
Viral infections
Family history
Exposure to certain types of dust e.g metal and wood dust
81
what are the symptoms of pulmonary fibrosis?
Shortness of breath
Tiredness
Persistent dry cough
Loss of appetite and weight loss
Swollen fingertips
82
What are the symptoms of emphysema?
Shortness of breath
83
What is emphysema caused by?
Damaged alveoli causes the inner walls of the air sacs to weaken and rupture. This created large air spaces, reducing the surface area which reduces the rate of gas exchange.
84
What are the risk factors that can cause emphysema?
Smoking
Age
Exposure to 2nd hand smoke
Exposure to pollution
85
Summarise what the trachea is.
- has c shaped rings of cartilage to keep it open. Has ciliated epithelial tissue to waft pathogens and mucus out of the airways. Leads to bronchi.
86
Summarise what the bronchi are.
1 per lung, has c shaped cartilage rings to keep them open.
87
Summarise what the bronchioles are.
- branch off bronchi, supplied 02 to alveoli.
88
Summarise what the alveoli are.
- sacs with a large surface area in which 02 moves into the capillaries surrounding them. Site of gas exchange.
89
Summarise what the diaphragm is.
A large sheet of muscle that separates the lungs from the abdominal cavity. Contracts to help you inhale and exhale.
90
Summarise what the intercostal muscle is.
Located in the rib cage to provide support. Expands and shrinks the size of the chest cavity.
91
What is inspiration?
Breathing in
92
Describe the process of inspiration.
- the external intercostal muscles contract, while the internal intercostal muscles relax.
- the ribs are pulled upwards and outwards, increasing the volume of the thorax.
- the diaphragm muscles contract, causing it to flatten, which also increases the volume of the thorax.
- the volume of the thorax results in reduction of pressure in the lungs.
- atmospheric pressure is now greater than pulmonary pressure, and so air is forced into the lungs.
93
What is expiration?
Breathing out
94
Describe the process of expiration.
- the internal intercostal muscles contract, while the external intercostal muscles relax.
- the ribs move downwards and inwards, decreasinf the volume of the thorax.
- the diaphragm muscles relax, making it return to its upwardly domed position, again decreasing the volume of the thorax.
- the decreases volume of the thorax increases the pressure in the lungs.
- the pulmonary pressure us now greater than that of the atmosphere, and so air is forced out of the lungs.
95
Why do the external intercostal muscles contract, while the internal intercostal muscles relax during inspiration?
The intercostal muscles are **antagonistic**
96
What is the tidal volume?
Volume of air breathed in and out of the lungs during each breath
97
How do you calculate pulmonary ventilation?
Tidal volume x ventilation rate
98
Define digestion.
Large biological molecules are hydrolysed to smaller ones that can be absorbed across cell membranes.
99
What is mechanical digestion?
Large chunks of food get broken down into smaller ones
100
What is chemical digestion?
The action of enzymes break don the food into energy
101
What food needs to be broken down?
Large molecules or macromolecules such as carbohydrates, proteins, lipids.
Small molecules or micro molecules like minerals, vitamins and water
102
What are macromolecules broken down by?
Hydrolysed by enzymes called hydrolases. E.g amylase, lipase, protease
103
Carbohydrates require more than one ________ to hydrolyse them into monosaccharides.
Enzyme
104
What do carbohydrates require to be broken down?
Amylases
Membrane bound disaccharides
105
Where is amylase produced?
The Pancreas and salivary glands
106
What does amylase do to carbohydrates?
Hydrolysed polysaccharides into the disaccharide maltose by hydrolysing the glycosidic bonds.
107
During digestion of carbohydrates, where do amylase act?
In the mouth
108
Which membrane bound enzymes act in the 2nd part of carbohydrate digestion?
Sucrase and lactase.
109
In the ______________ and _______, sucrase and lactase hydrolyse sucrose and lactose into monosaccharides.
Duodenum
Ileum
110
What does sucrase digest sucrose to?
Glucose and fructose
111
What does lactase digest lactose into?
Glucose and galactose
112
MOUTH (?). (?)
Starch glycogen ————————-> maltose——————-> glucose
1.Amylase
2. Maltase
113
ILEUM (?)
Sucrose ———————-> glucose + fructose
(?)
Lactose ———————> glucose + galactose
1. Sucrase
2. Lactase
114
Amylase is produced by the _______ and ___________ _______. It hydrolyses polysaccharides into the disaccharide ___________ by hydrolysing the ____________ bonds.
Pancreas
Salivary glands
Maltose
Glycosidic
115
Which 3 enzymes can hydrolyse proteins?
Endopeptides
Exopeptides
Membrane bond dipeptidases
116
What do endopeptidases do?
Hydrolyse peptide bonds between amino acids in the middle of a polymer chain
117
What do exopeptidases do?
Hydrolyse peptide bonds between amino acids at the end of a polymer chain
118
What do membrane-bound dipeptidases do?
Hydrolyse peptide bonds between two amino acids e.g when there are only 2 amino acids together left in a protein chain.
119
Protein digestion starts in the ________, continues in the ____________ and is fully digested in the _____.
Stomach
Duodenum
Ileum
120
Lipids are digested by _______ and the action of _______ _______.
Lipase
Bile salts
121
Where is lipase produced?
The pancreas
122
What does lipase hydrolyse?
The ester bond in triglycerides
123
Lipase is produced in the ______ and it can hydrolyse the ______ bond in ________________to form the monoglycerides and fatty acids.
Pancreas
Ester
Triglycerides
124
Where are bile salts produced?
The liver
125
what do bile salts do?
Emulsify fats to form Micelles.
Micelles increase the surface area for lipase to act on.
This occurs before lipase action.
126
Describe how micelles assist lipid digestion.
Fatty acids and monoglycerides (from fat digestion) leave micelles and enter epithelial cell as they are non polar.
Monoglycerides and fatty acids are transported to the Endoplasmic reticulum where they form triglycerides.
This process starts in the ER and continues in the Golgi apparatus.
Chylomicrons are formed. (Triglycerides associate with cholesterol and lipoproteins to form these). Chylomicrons are adapted for the transport of lipids.
Chylomicrons move out of the epithelial cells by exocytosis.
They then enter the lymphatic capillaries and lacteals (found in the centre of each villus).
127
What happens in lacteals?
Chylomicrons pass via lymphatic vessels, into the blood system. The tri-glycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of blood capillaries from where they diffuse into cells.
128
How long is the small intestine?
7 metres
129
The small intestine has an upper tube called the ____________ into which opens the bile duct and the pancreatic duct.
Duodenum
130
What is the upper tube of the small intestine called?
The duodenum
131
The duodenum leads via the _________ to a lower tube called the ileum.
Jejunum
132
What are the 2 major functions of the small intestine?
Digestion
Absorption
133
What is the lining of the small intestine called?
Ileum
134
Where are villi found?
On the ileum
135
What do villi do?
Increase the surface area for enzyme action and the absorption of food.
136
What do the burners glands in the duodenum secrete?
Alkaline secretions which neutralise acidic chyme from the stomach.
137
What does the epithelial layer release which prevents the duodenum from acid damage?
Mucus
138
What are the small projections on villi called?
Microvilli
139
How thick is the epithelium and why?
One cell thick
Reducing the diffusion distance
140
The ______ is the main sight of absorption.
Ileum
141
Bile acts to __________ lipids into __________.
Emulsify
Micelles
142
To absorb glucose and amino acids from the lumen to the gut there must a higher concentration gradient in the __________ compared to the __________ ______ (for ____________ diffusion).
Lumen
Epithelial cell
Facilitated
143
Haemoglobin + 02 ————-> ?
Oxyhaemoglobin
144
Haemoglobin is a ______ protein.
Globular
145
How many polypeptide chains are there in Haemoglobin?
4
146
Each polypeptide chain in Haemoglobin contains _ haem group. Each haem group can combine with _ oxygen molecule.
1
1
147
How many oxygen molecules can Haemoglobin bind to?
4
148
Describe the tertiary structure of Haemoglobin.
Each polypeptide chain is folded into a precise shape - an important factor in its ability to carry oxygen.
149
Describe the quaternary structure of Haemoglobin.
4 polypeptide chains are linked together to form an almost spherical molecule. Each polypeptide chain is associated with a haem group - containing ferrous iron (Fe2+). Each ion can combine with a single oxygen.
150
What is oxygen saturation?
The amount of oxygen bound to the haemoglobin in our blood.
151
What are the units for oxygen saturation?
SaO2%
152
Describe how oxygen associates and disassociated from Haemoglobin
At a gas exchange surface C02 is being removed. C02 is acidic so the PH is raised, due to the low level of C02.
Change in PH (increase) changes the shape of haemoglobin to one that loads readily and increases the affinity of Haemoglobin for 02. (Tertiary structure changes).
In tissues C02 is produced by respiring cells. PH of blood is lowered.
A lower PH changes the shape of Haemoglobin into one with a lower affinity for oxygen - releasing the oxygen.
153
The effect of carbon dioxide is to shift the whole oxygen dissociation curve to the……
Right
154
Carbon dioxide causes the oxygen affinity of haemoglobin to ________.
Decrease
155
The partial pressure of carbon dioxide will be high in _________ tissue undergoing _________ ___________.
Active
Aerobic respiration.
156
When does haemoglobin have a higher affinity for oxygen?
Where the partial pressure of carbon dioxide is low e.g in the lungs
157
Why does haemoglobin unload bound oxygen in respiring tissues?
The Haemoglobin has a lower oxygen affinity because the partial pressure of carbo dioxide is high.
158
What can carbon dioxide form in the blood?
Carbonic acid
159
What does carbonic acid release?
Hydrogen ion (H+)
160
What does H+ do to haemoglobin?
It combines with haemoglobin and causes the quaternary structure of the haemoglobin to change. As a result of the change in the quaternary structure, the haemoglobin has a lower affinity for oxygen. This causes the haemoglobin to unload its oxygen more readily.
161
What 5 factors can cause a right shift on an oxygen dissociation curve?
- affinity for oxygen decreases
- high concentration of carbon dioxide
- PH lowered
- increase in temperature
- high metabolic rate
162
What causes a left shift on the oxygen dissociation curve?
- increased affinity for oxygen
- low concentration of carbon dioxide
- PH increase
- decrease in temperature
- low metabolic rate
163
What is a right shift in the oxygen dissociation curve called?
The Bohr effect
164
What type of curve is the oxygen dissociation curve?
Sigmoid curve (s shape)
165
At low partial pressures of oxygen, haemoglobin has a _____ affinity for oxygen.
Low
166
What happens once one oxygen molecule is bound to a haem group?
The affinity of haemoglobin for oxygen increases. It becomes much easier to bind further oxygen molecules.
When one molecule of oxygen binds, the quaternary structure of the haemoglobin molecule changes - this now increases the affinity of the haem groups for oxygen. So, binding molecules only requires a relatively small increase in the oxygen partial pressure.
167
What is positive cooperativity?
When one oxygen molecule binds to haemoglobin, changing the quaternary structure. This means that binding molecules only require a relatively small increase in the oxygen partial pressure.
168
Where is the partial pressure of oxygen high?
Alveoli
169
What happens to red blood cells as they move into body tissues?
There is a lower partial pressure of oxygen as the tissues are carrying out aerobic reparation. So, at a certain point one oxygen molecule will dissociate from the haemoglobin molecule. This unloading changes the quaternary structure of the haemoglobin molecule. The effect of this is to decrease the oxygen affinity of the remaining haem groups.
170
It is _______ that **all** oxygen molecules will unload from a haemoglobin molecule under normal conditions. But, it could take place in very ______ tissue. E.g muscle tissue during intensive _______.
Unlikely
Active
Exercise
171
Name the 4 chambers of the heart?
Right atrium Left atrium
Ventricle Left ventricle
172
What do large organisms have to ensure that they obtain the oxygen and glucose they require?
A double circulatory system
173
Why do large organisms have a double circulatory system?
They have a small surface area: volume ratio so they cannot obtain the oxygen and glucose they require by diffusion
174
What are the features of a transport system?
- a watery liquid (blood) that readily dissolves substances
- a closed system of branching vessels to distribute the transport medium to all the parts of the organism
- a mechanism for moving the transport medium e.g heart and other muscles (arteries) - or the transpiration stream in plants
- a mechanism to ensure the flow is in one direction and a way of controlling the flow to meet the demand e.g valves to prevent back flow of blood
175
What arteries is a closed system made up of?
Arteries, capillaries, veins
176
What takes oxygenated blood to the heart?
Pulmonary vein
177
What takes deoxygenated blood to the lungs?
Pulmonary artery
178
What transports oxygenated blood to the body?
Aorta
179
What takes oxygenated blood to the liver?
Hepatic artery
180
What takes deoxygenated blood from the liver?
Hepatic vein
181
What takes oxygenated blood to the kidneys?
Renal artery
182
What takes deoxygenated blood from the kidneys?
Renal vein
183
what makes a closed blood system?
If the blood is confined to vessels
184
What is the function of an artery?
Transports blood from the heart rapidly under high pressure
185
Describe the structure of an artery.
❑ Thicker muscle layer (compared to vein): Can be constricted and dilated to control blood flow
❑Thicker elastic layer: blood pressure needs to be kept high in arteries in order to reach extremities of body. They are stretched at each beat of the heart. It then springs back(recoils) when it relaxes.
❑ Overall thickness large: stops the vessel bursting under pressure
❑ No valves (except in those leaving heart): Blood is under constant high pressure and doesn’t flow backwards
186
What is the function of an arteriole?
Carry blood under lower pressure than arteries, from arteries to capillaries & regulate blood flow between the two.
187
Describe the structure of an arteriole.
❑ Muscle layer thicker than arteries: allows constriction of the lumen in order to control blood flow into capillaries
❑ Elastic layer thinner than arteries: blood pressure lower
188
What is the function of a vein?
Carry blood slowly, under low pressure from tissues to heart.
189
Describe the stature of a vein.
❑ Muscle layer relatively thin: does not control flow to the tissues
❑ Elastic layer relatively thin: Low pressure will not cause them to burst
❑ Overall thickness small: no need for thick wall as pressure is low. Allows them to be easily flattened aiding flow of blood
❑ Valves: ensure blood does not flow backwards, when body muscles contract, veins are compressed, pressurising the blood within them, forcing & pushing blood along the vein
190
What is the function of a capillary?
Exchange of Oxygen, Carbon dioxide and glucose between blood and cells. Slow blood flow allows more time for exchange of materials.
191
Describe the structure of a capillary.
❑ Walls extremely thin, so short diffusion pathway between blood and cells
❑ Numerous and highly branched- creating a large surface area
❑ Narrow: Permeate tissue so that no cell is far away from a capillary
❑ Narrow lumen: RBC’s squeeze flat against the side to bring them closer to the cells
❑ Pores in the endothelium: allow WBC’s to escape
192
where does coronary heart disease occur?
Coronary arteries
193
What is coronary heart disease caused by?
An atheroma specific to the coronary artery
194
What is an atheroma?
Fatty deposits form within the wall of an artery.
•These are accumulations of white blood cells that have taken up Low-density lipoproteins (LDL’s)
•Bulge into lumen taking up room narrowing of arteries and blood flow is reduced.
195
What is a myocardial infaraction?
Heart attack- reduced supply of oxygen to the muscle of the heart. Blockage in the coronary arteries.
•If occurs close to junction of coronary artery and aorta, the heart will stop beating.
196
What are the risk factors for heart disease?
Smoking
2-6 times more likely to suffer from heart disease
Smoking
•
haemoglobin to form carboxyhaemoglobin which reduces the oxygen-carrying capacity of blood. The heart has to work harder to deliver the same amount of oxygen.
•High blood pressure which increases risk of CHD and strokes
Carbon monoxide
combines irreversibly with
Nicotine:
•Stimulates adrenaline production which increases heart rate and raises blood pressure
- makes red blood cells and more ‘sticky’ and leads to higher risk of thrombosis
Diet
High levels of salt:
raises blood pressure
High levels saturated fat: density lipoproteins
increases low
Blood cholesterol
High - density lipoproteins remove
cholesterol from tissues and transport to liver for excretion. Help protect against heart disease
Low density lipoproteins transport
cholesterol from liver to tissues, including artery walls, which they infiltrate, leading to development of atheroma.
density lipoproteins (HDL’s): remove
197
Why is smoking a risk factor for heat disease?
2-6 times more likely to suffer from heart disease
Carbon monoxide combines irreversibly with haemoglobin to form carboxyhaemoglobin which reduces the oxygen-carrying capacity of blood. The heart has to work harder to deliver the same amount of oxygen.
High blood pressure which increases risk of CHD and strokes
Nicotine:
Stimulates adrenaline production which increases heart rate and raises blood pressure
Makes red blood cells more ‘sticky’ and leads to higher risk of thrombosis
198
why is diet a risk factor for heart disease?
High levels of salt: raises blood pressure
High levels saturated fat: increases low density lipoproteins
199
How is blood cholesterol a risk factor for heart disease?
High-density lipoproteins (HDL’s): remove cholesterol from tissues and transport to liver for excretion. Help protect against heart disease
Low-density lipoproteins (LDL’s) transport cholesterol from liver to tissues, including artery walls, which they infiltrate, leading to development of atheroma.
200
What are the 2 types of blood cholesterol?
High-density lipoproteins (HDL’s)
Low-density lipoproteins (LDL’s)
201
What are the 2 components that make up the bloood?
Cells
Blood plasma
202
what makes up the cells in the blood?
Red blood cells
White blood cells
Platelets
203
What makes up blood plasma?
Glucose
Amino acids
Mineral ions
Oxygen
Plasma proteins
204
Where does tissue fluid leave the blood?
The parts of the capillary which are near the artery
205
Tissue fluid transfers molecules such as ________ and __________ to the tissue cells
Oxygen
Glucose
206
Tissue fluid returns back to the blood at the _______ end of a capillary
Venous
207
Blood at the arterial end of the capillary is under relatively ______ pressure.
High
208
___________________ _________ tends to force fluid out of the blood and into the tissue.
Hydrostatic pressure
209
What lowers the water potential of blood plasma and why?
Plasma proteins
They are hydrophilic
210
Plasma proteins are hydrophilic so they lower the water potential of the blood plasma. So there is a tendency for water to to move back _______ the blood by _______.
Into
Osmosis
211
What is ultrafiltration?
Tissue fluid is forced out of the capillary through gaps between endothelial cells because in the ar arterial end of the capillary, the hydrostatic pressure is greater than the onctic pressure.
212
What molecules are too large to leave the capillary so remain in the blood plasma?
Blood cells and plasma proteins
213
At the venous end of the capillary, the hydrostatic pressure is much ________.
Lower
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why is the hydrostatic pressure at the venous end of the capillary much lower?
A large amount of water has left the blood
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What causes water to move into the blood by osmosis at the venous end of a capillary?
The hydrostatic pressure is less than the oncotic pressure
216
What happens to the tissue fluid that isn’t re absorbed?
It is drained into lymph capillaries
217
What do lymph capillaries connect to?
Larger lymph vessels, forming the lymphatic system
218
How does lymph fluid move along lymph vessels?
The lymph vessels are squeezed by nearby skeletal muscles
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What helps lymph fluid to move forward in the lymph vessels?
Valves
220
what happens to lymph fluid?
It eventually returns to the bloodstream via blood vessels
221
What is the cardiac cycle?
The sequence of events during one heartbeat
222
How long is the cardiac cycle?
0.8 seconds
223
Describe an atrial systole?
- cardiac muscles of atria contracts
- volume of atria decreases
- blood pressure in atria increases
224
What is this the process of?
cardiac muscles of atria contracts
- volume of atria decreases
- blood pressure in atria increases
Atrial systole
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A systole is a _________.
Contraction
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A diastole is a ________.
Relaxation
227
Describe the process of a ventricular systole?
- cardiac muscles of ventricles contract
-volume of ventricles starts to decrease
- blood pressure in ventricles starts to rise
- when blood pressure increases above that of the atrial the atrioventricular valves slam shut (“lubb”)
- blood pressure continues to rise as ventricular cardiac muscles continues to contract
- blood pressure now becomes greater in ventricles compares with arteries
- semi-lunar valves which have been shut until now open
- blood flows out of the heart into the aorta and pulmonary arteries
228
what is this process?
cardiac muscles of ventricles contract
-volume of ventricles starts to decrease
- blood pressure in ventricles starts to rise
- when blood pressure increases above that of the atrial the atrioventricular valves slam shut (“lubb”)
- blood pressure continues to rise as ventricular cardiac muscles continues to contract
- blood pressure now becomes greater in ventricles compares with arteries
- semi-lunar valves which have been shut until now open
- blood flows out of the heart into the aorta and pulmonary arteries
Ventricular systole
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cardiac muscles of ventricles________
-volume of________ starts to decrease
- blood pressure in ventricles starts to rise
- when blood pressure increases above that of the atrial the______________ valves slam shut (“lubb”)
- blood pressure continues to rise as ventricular cardiac muscles continues to contract
- blood pressure now becomes greater in ventricles compares with__________
- semi-lunar valves which have been shut until now______
- blood flows out of the heart into the aorta and pulmonary arteries
Contract
Ventricles
Atrioventricular
Arteries
Open
230
Describe the process of an atrial diastole
- atrial cardiac muscle relaxes
- pressure decreases and blood flows into atria from veins so volume increases
231
What is this the process of?
- atrial cardiac muscle relaxes
- pressure decreases and blood flows into atria from veins so volume increases
Atrial diastole
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Describe the process of a ventricular diastole.
- cardiac muscles of ventricles relaxes
- pressure in ventricles starts to decrease and volume increases
- when the blood pressure drops below that in the arteries, the semi-lunar valves slam shut (“dub” sound)
- on further relaxation, continued increase in volume and drop in pressure brings the blood pressure of the ventricles below that in the atria
- atrioventricular valves now open and blood starts to flow into the ventricles from the relaxed but filling atria
233
What is this the process of?
- cardiac muscles of ventricles relaxes
- pressure in ventricles starts to decrease and volume increases
- when the blood pressure drops below that in the arteries, the semi-lunar valves slam shut (“dub” sound)
- on further relaxation, continued increase in volume and drop in pressure brings the blood pressure of the ventricles below that in the atria
- atrioventricular valves now open and blood starts to flow into the ventricles from the relaxed but filling atria
Ventricular diastole
234
Define heart rate.
Number of heart beats per minute
235
Define stroke volume
Volume of blood (cm3) pumped by heart in 1 beat
236
Define cardiac output
Stroke volume multiplied by the heart rate gives the amount of blood (cm3) pumped by heart in 1 minute
237
How do you calculate heart rate?
Heart rate = #beats
————-
Minute
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how do you calculate stroke volume?
Stroke volume = bloom cm3
—————
Beat
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How do you calculate cardiac output?
Cardiac output = blood cm3 X #beats = blood
————- ———- ——
Beat. Min. Min.
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What factors can change cardiac output?
Cardiovascular centre in brain
Hormones e.g. adrenaline
Stretching of cardiac muscle
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Narrower vessels=…….?
Vasoconstriction
242
Wider vessels= ………….?
Vasodilation
243
What factors affect blood pressure?
Cardiovascular centre
Smoking
Diet
Adrenaline
Increase in blood viscosity
244
How does the cardiovascular centre affect blood pressure?
Diameter of blood vessels controlled by stimulation of sympathetic and parasympathetic nerves
245
How does smoking affect blood pressure?
Nicotine causes vasoconstriction
Build up of fatty deposits in vessels
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How does diet affect blood pressure?
High fat diet leads to build up of fatty deposits in blood vessels
247
How does adrenaline affect blood pressure ?
Causes selective vasoconstriction & vasodilation
248
How does increase in blood viscosity affect blood pressure?
Excess water loss (sweating/excessive urination)
249
What is the SA node also known as?
Pacemaker
250
Describe the cardiac cycle (electrical activity)
- SA mode starts initial stimulus
- a wave of excitation is started
- the wave spreads across both atria
- atrial systole - blood is pushed into the ventricles
- the atria relax
- there is a short delay
- excitation reaches the AV node
- the excitation reaches the bottom of the bundle of His
- excitation passes along the Purkyne fibres
- the excitation moves up the sides of the ventricles
- the ventricles contract in a wringing movement
- blood is forced into the arteries
- the heart is relaxed
- the atria refill with blood
- the next cycle starts
251
The cardiac cycle
- __ node starts initial stimulus
- a wave of _________ is started
- the wave spreads across both____
- atrial systole - blood is pushed into the_________
- the atria ______
- there is a short ______
- excitation reaches the __ node
- the excitation reaches the bottom of the______ of His
- excitation passes along the Purkyne ______
- the excitation moves up the sides of the_________
- the ventricles ____________ in a wringing movement
- blood is forced into the ________
- the_______ is relaxed
- the atria refill with blood
- the next cycle starts
- SA
- excitation
- atria
- ventricles
- relax
- delay
- AV
- bundle
- fibres
- ventricles
- contract
-arteries
-heart
252
What forms the vascular bundle?
Xylem and phloem
253
What are the elements of the xylem vessel?
Dead cells (walls made of lignin, impermeable to water)
The end of the walls break down to form an uninterrupted pathway for the water (xylem vessels)
Gaps in the walls called pits to allow movements between vessels and/or living tissues nearby
254
What is transpiration the movement of?
Water
255
What ‘dilemma’ do plants have to balance water uptake with water loss?
Stomata open =more gas exchange but also more water loss
Stomata closed =less water loss but also less gas exchange
256
How does temperature increase evaporation in a plant?
Temperature increase ———> water molecules gain kinetic energy——-> increased evaporation
257
What happens to the rate of evaporation when you decrease humidity?
Increases
258
Describe cohesion-tension theory.
Water in the xylem vessels is pulled (therefore under tension) towards the leaves because of the transpiration (transpiration pull).
Water molecules attract each other, because they are dipoles. This provides cohesion (stickiness) of the molecules, hence the uninterrupted column of water.
259
Describe the root pressure theory.
In the roots, endodermis cells (around the xylem vessels) actively transport mineral ions into the xylem, reducing its water potential
water is drawn in hydrostatic pressure increases water is pushed upwards
(mainly herbaceous plants)
260
Describe capillarity.
Water molecules ‘climb up’ in narrow tubes (μm) because they are attracted (adhesion) to polar molecules of the tube.
The narrower the tube the higher the water goes
261
What are the 3 water movement theories?
Cohesion-tension theory
Root pressure
Capillarity
262
Describe how plants uptake mineral ions.
• Plants obtain the mineral from the soil (except carnivorous plants and legumes)
• Nitrogen usually enters the plant as nitrates/ammonium ions
• Ions move into the roots by diffusion (down the concentration gradient) or active transport
• Ions move across the roots.
• At the endodermis these ions are actively transported to by-pass the Casparian bands. Plants can so be selective of the ion taken in
263
What is translocation?
Where the phloem tissue transports substances made in the leaves to all other parts of the plant.
264
What does the phloem transport?
Sucrose (soluble carbohydrate)
Amino acids
Minerals
Hormones
265
Describe the process of translocation.
1. Sucrose is manufactured in leaves from glucose made in photosynthesis
2. Sucrose is transported by facilitated diffusion into the companion cells
3. Hydrogen ions are actively transported from companion cells into phloem along with sucrose.
4. This means the contents of the phloem now has a lower water potential than the Xylem.
5. Water from the xylem moves by osmosis into the phloem creating a hydrostatic pressure.
6. Respiring cells are using up sucrose which lowers their water potential.
7. Water then moves from the phloem into the xylem by osmosis.
8 The pressure is lowered in respiring cells
Sucrose moves from source to sink using the hydrostatic pressure gradient.
266
TRANSLOCATION
1. Sucrose is manufactured in leaves from _______made in photosynthesis
2. Sucrose is transported by _________ diffusion into the companion cells
3. Hydrogen ions are_____ transported from companion cells into phloem along with sucrose.
4. This means the contents of the phloem now has a______ water potential than the Xylem.
5. Water from the xylem moves by _______ into the phloem creating a hydrostatic pressure.
6. Respiring cells are using up _______ which lowers their water potential.
7. Water then moves from the phloem into the _____ by osmosis.
8 The pressure is lowered in __________cells
Sucrose moves from source to sink using the hydrostatic pressure gradient.
1. Glucose
2. Facilitated
3. Actively
4. Lower
5. Osmosis
6. Sucrose
7. Xylem
8. Respiring
267
Describe the experiment using aphids to show phloem transport of food substances.
- aphid penetrates the stem into the phloem using its mouthpart called stylet and sucks the plant sap
- a feeding aphid can be anaesthetised and the stylet cut off
- the phloem sap flows out through the stylet and can be analysed. It is found to contain sugars and other organic substances
268
Describe how ringing experiments show phloem transport of food substances.
In the ringing experiment, a ring of bark is scraped away that also removes the phloem, exposing the xylem. Sugar then attempts to move down the stem but is stopped by the ring. This is demonstrated by a bulge of sugar forms above the ring, suggesting that sugar moves down the stem in the phloem and is transported by the xylem.
269
Describe how radioactive tracers show phloem transport of food substances.
These show the direction of flow of sucrose, This method uses radioactive carbon dioxide (14C). This radioactive carbon dioxide is put in a bag over a leaf and sealed. The carbon dioxide gets converted into glucose and an x-ray can
be taken that will show the radioactive C in the phloem.
270
What are the 3 experiments that can show phloem transport of food substances?
- using aphids
- ringing experiments
- radioactive tracers
271
What are the two ways in which water goes through a plant?
- cell wall pathway
- cytoplasmic pathway
