Module 3 notes Flashcards
(84 cards)
1
Q
surface area : volume
A
- exchange surfaces in organisms have many similar adaptations to make transport across the surface more efficient
- small organisms, e.g. amoeba, have very large SA:V ratio
- big SA means shorter distance fro outside of organism so middle of it- so simple diffusions meets exchange needs
- larger organsisms have small SA:V ratio, higher metabolic rate, longer distance from outside to middle- so require adaptations to increase efficiency of exchange
2
Q
3 structural factors that affect rate of diffusion
A
- surface area
- concentration gradient
- length of diffusion pathway
3
Q
mammalian gas exchange system structures
A
- trachea
- bronchi and bronchioles
- alveoli
4
Q
trachea
A
- C-shaped rings of cartilage for support
- ciliated epithelium with goblet cells
- smooth muscle is within walls of trachea
- muscle contracts if there are harmful substances detected in air
- results in lumen of trachea constricting and reducing airflow into lungs
- when smooth muscle relaxes, lumen dilates
- this stretch and recoil of lumen is possible due to elastic fibres within tracheal wall
5
Q
bronchi and bronchioles
A
- trachea splits into 2 tubes, the bronchi, which connect to right and left lung
- these split into many smaller tubes to create network of bronchioles
- both bronchi and broncioles have cartilage in their walls for structural support and to keep tubes open
6
Q
alveoli
A
- located at end of broncioles
- site of gas exchange
- oxygen diffuses from alveoli into blood in capillaries and carbon dioxide diffuses from blood in capillaries to alveoli
- large SA –> large number of alveoli
- short diffusion distance –> alveoli walls are very thin, made of squamos epithelial cells
- maintains steep concentration gradient –> each alveolus surrounded by network of capillaries to quickly take away O2 and ventilation in lungs is constant to quickly take away CO2
7
Q
ventilation
A
the mechanism of breathing which involves the diaphragm and antagonistic interactions between the external and internal intercostal muscles, bringing about pressure changes in the thoracic cavity
8
Q
inspiration
A
results in increased volume of the thorax, therefore air pressure inside thorax is reduced- causes air to flow into lungs
* diaphragm contracts- moves down and becomes flatter
* external intercostal muscles contract
* internal intercostal muscles relax
* pulls ribcage up and out
9
Q
expiration
A
decrease in volume of thorax and there is increase in air pressure within thorax- forces air out of lungs
* diaphragm relaxes- domes upwards
* external intercostal muscles relax
* forced expiration- internal intercostal muscles contract
* relaxed expiration- internal intercostal muscles remian relaxed
* pulls ribcage inwards and down
10
Q
spirometer
A
measures volume of air inhaled and exhaled
11
Q
vital capacity
A
maximum volume of air an individual can inhale and exhale during a deep breath
12
Q
tidal volume
A
the air inhaled (peaks) and exhaled (troughs) when at rest
13
Q
residual volume
A
the volume of air that always remains in the lungs to they don’t collapse
14
Q
breathing rate
A
number of breaths taken per minute
(can be worked out from graph by counting how many breaths taken per minute- how many full peaks and troughs there are)
15
Q
ventilation rate
A
volume of air inhaled per minute
(tidal volume x breathing rate)
16
Q
oxygen uptake
A
will increase when ventilation rate increases, e.g. during exercise
17
Q
ventilation in fish
A
- swim with their mouth open so water flows over the gills
- lower their buccal cavity and open their mouth; this increases the volume of the buccal cavity and therefore decreases the pressure- results in water flowing into the buccal cavity
- operculum valve will shut and operculum cavity (where gills located) will expand
- causes an increase in volume of operculum cavity- decrease in pressure
- fish will then raise floor of buccal cavity, forcing water from buccal cavity over gills within operculum cavity
- fish closes its mouth and opens operculum- increases pressure in operculum cavity and roces water over gillsand out side of fish’s head
- ensures constant flow of water over gills for gas exchange
18
Q
gas exchange in fish
A
- exchange gases across their gills
- have 4 layers of gills on both sides of their heads
- gills made of gill filaments and gill lamellae
- large SA–> many gill filaments and lamellae which are stacked at right angles to each other
- short diffusion distance–> gill lamellae and filaments are both thin and contain a capillary network
- maintain steep concentration gradient–> countercurrent mechanism
19
Q
countercurrent flow mechanism
A
- water has a lower dissolved oxygen concentration compared to the concentration of oxygen in the atmosphere
- for fish to be able to maintain the steep concentration gradient for diffusion, counter-current flow mechanism is used
- this is when water flows over gill lamellae in opposite direction to flow of blood in capillaries
- ensures that diffusion gradient is maintained across entire length of gill lamellae
20
Q
gas exchange in insects
A
- involves tracheal system made up of spiracles (valve like structures that run along side of abdomen) and trachea
- insects contract and relax their abdominal muscles to move gases on mass into and out of the spiracles to the trachea
- large SA–> many brandhing tracheoles
- short diffusion distance–> many branching tracheoles reach muscle and thin-walled tracheoles
- maintains steep concentration gradient–> when cells respire, they use up oxygen and produce carbon dioxide. Abdominal muscle contract to pump air
- when insect is in flight, muscle cells start to respire anaerobicalyt to produce lactate- lowers water potential of cells so water moves from tracheoles into cells by osmosis- decreases volume of liquid in tracheoles and causes more air from atmosphere to move in
21
Q
ciculatory systems
A
- each animal has a ciculatory system adapted to meet its needs
- transport gases and nutrients around an organism in a transport liquid (e.g. blood)
- this liquid is transported around in vessels and there is a pump to move the liquid (e.g. heart)
22
Q
4 types of circulatory systems
A
- open
- closed
- double
- single
23
Q
open circulatory system
A
- invertebrates, e.g. insects
- transport medium (haemolymph) is usually pumped direclty to open body cavity (haemocoel) and there are very few transport vessels
- transport medium is pumped at low pressure and will transport food and nitrogenous waste, but not gases, which are transported via tracheal system
- once exchange has taken place at cells and tissues, transport medium returns to heart through open-ended vessel
24
Q
closed circulatory systems
A
- all vertebrares, e.g. fish and mammals, and some invertebrates, e.g. annelid worms
- transport medium (blood) remains inside vessels (blood vessels)
- gases and small molecules can leave blood by diffusion or due to high hydrostatic pressure
- transport oxygen and carbon dioxide, and oxygen usually transported by a pigmented protein, e.g. haemoglobin
25
single closed circulatory systems
- blood only passes through heart once per cycle
- e.g. fish
- blood passes through 2 sets of capillaries. Immediately after being pumped out of heart, blood flows through capillaries in gills to become oxygenated
- blood then flows through capillaries delivering blood to body, before returning back to heart
- system would not enable efficient gas exchange for mammals, but works for fish due to counter-current flow mechanism
26
double closed circulatory systems
- blood passes through heart twice per cycle
- e.g. birds and most mammals
- one circuit of blood vessels carries blood from heart to lungs for gas exchange (the pulmonary circuit)
- second circuit of blood vessels carries blood from heart to rest of body to deliver oxygen and nutrients and to collect waste (the systemic circuit)
27
arteries
- smooth muscle layer- thicker than veins so that constriction and dilation can occur to control volume of blood
- elastic layer- thicker than veins to help maintain blood pressure. The walls can strecth and recoil in response to the heart beat
- collagen layer- collagen outer layer to provide structural support
- wall thickness- thicker than veins to help maintain blood pressure
- no valves
28
arterioles
- smooth muscle layer- thicker than in arteries to help restrict blood flow into capillaries
- elastic layer- thinner than in arteries as pressure is lower
- collagen layer- thinner
- wall thickness- thinner as pressure is slightly lower
- no valves
29
capillaries
- no smooth muscular wall
- no elastic layer
- no collagen layer
- wall thickness- one cell thick consisting of only a lining layer- provides short diffusion distance for exchanging materials between the blood and cells
- no valves
30
venules
- smooth muscle layer- thin
- no elastic layer
- no collagen layer
- wall thickness- very thin wall. Several venules join to form a vein
- has valves
31
veins
- smooth muscle layer- relatively thin so it cannot control blood flow
- elastic layer- relatively thinner as pressure lower
- collagen layer- lots of collagen
- wall thickness- thin as pressure is lower so low risk of vessel bursting. Thinness means vessels are easily flattened, which helps flow of blood up to heart
- has valves
32
tissue fluid
- capillaries have small gaps in their walls so that liquid and small molecules can be forced out- this forms tissue fluid
- the interaction of hydrostatic and oncotic pressure is responsible for the formation and reabsorption of tissue fluid
33
hydrostatic pressure
the pressure exerted by liquid
34
oncotic pressure
the tendency of water to move into the blood via osmosis
35
tissue fluid formation
- as blood enters capillaries from arterioles, the smaller diameter results in high hydrostatic pressure
- this pressure forces water, glucose, amino acids, fatty acids, ions and oxygen out of the capillaries at the arterial end
- the solution that has been forced out is called tissue fluid and it bathes the cells in substances they need
- the hydrostatic pressure is higher than the oncotic pressure at the arterial end of the capillaries, so the net movement of liquid is out of the blood in the capillaries
36
tissue fluid reabsorption
- large molecules, e.g. plasma proteins) remain in the capillaries and therefore lower water potential of blood remaining in capillary
- this results in higher oncotic pressure
- towards venule end of capillaries, hydrostatic pressure is low due to loss of liquid, but water potential very low
- as result, net movement of liquid is back into capillary by osmosis
- once equilibrium of water potential of blood is reached, no more water from tissue fluid can be reabsorbed back into blood in capillaries
- remaining liquid is absorbed into lymphatic system and eventually drains back into bloodstream near heart
- once liquid in lymphatic system, it's called lymph
- lymph has similar composition to plasma, except it does not contain large plasma proteins and has less oxygen and nutrients
37
mammalian heart
- organ, made of cardiac muscle, responsible for pumping blood aroung blood vessels
- cardiac muslce is myogenic (automatically contracts and relaxes) and it never fatigues
- coronary arteries supply cardiac muslce with oxygenated blood for aerobic respiration- provides ATP so cardiac muslce can continually contract and relax
- heart surrounded by pericardial membranes- inelastic membranes which prevent heart from filling and swelling with blood
38
left ventricle of mammalian heart
- thicker muscular wall so it can contract with more force and pump blood at higher pressure
- needed so that blood will flow all the way around the body
39
right ventricle of mammalian heart
- only pumps blood to lungs, which is much closer and requires blood to flow slowly to allow time for gas exchange
- muscular wall is much thinner as blood does not need to be pumped at as high a pressure
- atria both have very thin muscular walls as blood only needs to be pumped from atria into ventricles, so minimal pressure and force is required
40
3 stages of cardiac cycle
- diastole
- atrial systole
- ventricular systole
41
diastole
- atria and ventricular muscles are relaxed
- blood will enter atria via vena cava and pumonary vein
- blood flowing into atria increases pressure within atria and atrioventricular valves open so blood can begin to flow into ventricles
42
atrial systole
- atria muscular walls contract, increasing the pressure further
- causes blood to flow into ventricles, through open atrioventricular valves
- ventricular muscular walls relaxed.
43
ventricular systole
- after short delay, ventricle muscular walls contract, increasing pressure beyond that of atria
- causes atrioventricular valves to close and semi-lunar valves to open
- blood is pushed out of ventricles into arteries
44
cardiac output
volume of blood which leaves one ventricle in one minute
cardiac output= heart rate x stroke volume
45
structures in control of cardiac cycle
- cardiac muscle is myogenic- contracts on own accord- but rate of contraction is controlled by wave of electrical activity
- sinoatrial node (SAN) is located in right atrium and known as pacemaker
- atrioventricular node (AVN) is located near border of right and left ventricle within atria still
- bundle of His runs through septum
- Purkyne fibres in walls of ventricles
46
process of control of cardiac cycle
- SAN releases wave of depolarisation across atria, causing it to contract
- AVN releases another wave of depolarisation when the first reaches it. Non-conductive layer between atria & ventricles prevents wave of depolarisation travelling down to ventricles
- bundle of His conducts wave of depolarisation down septum & Purkyne fibres
- as result, apex & then walls of ventricles contract. There is a short delay before this happens, whilst AVN transmits second waves of depolarisation
- allows enough time for atria to pump all blood into ventricles. Cells repolarise, anc cardiac muslce relaxes
47
electrocardiogram (ECG)
- waves of depolarisation (electrical activity) can be measured using ECG and interpreted to diagnose irregularities in heart rhythms
- ECG doesn't directly measure electrical activity of heart, instead measures differences in electrical acitivty in skin which is caused by electrical activity of heart
- electrodes are stuck onto skin to detect electrical activity
48
4 abnormal heart rhythms
- tachycardia
- bradycardia
- fibrillation
- ectopic heartbeat
49
tachycardia
- when heart is beating at over 100bpm
- normal during exercise but would be anormally fast while at rest
50
bradycardia
- when heart beating at less than 60bpm
- many athletes have bradycardia as they are so fit that their cardiac muscle can contract harder and therefore fewer contractions are required
- if heart rate drops too low, artificial pacemaker is needed to regulate heart rate
51
fibrillation
- when there is an irregular and chaotic rhythm of heart
52
ectopic heartbeat
- when there are additional heartbeats that are not in rhythm
- will show up on an ECG as 2 heartbeats close together, followed by normally spaced heartbeats
- very common for this to occur once a day, but if it is happening more regularly, could indicate a serious health condition
53
haemoglobin
- globular protein
- protein with quaternary structure
- transport oxygen
54
oxyhaemoglobin dissociation curve
- oxygen is associated in regions with high partial pressure of oxygen (e.g. alveoli)- haemoglobin has high affinity for oxygen
- diassociated in regions of low partial pressure of oxygen (e.g. respiring tissues)- haemoglovin has low affinity for oxygen
- shown on oxyhaemoglobin dissociation curve
55
cooperative binding
- cooperative nature of oxygen binding to haemoglobin is due to haemoglobin changing shape when first oxygen binds
- makes it easier further oxygens to bind
56
the Bohr effect
- when a high carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right
- affinity for oxygen decreases because acidic carbon dioxide changes shape of haemoglobin slighlty
57
3 ways that carbon dioxide is transported
- dissolved in blood plasma
- as carbaminohaemoglobin. Carbon dioxide can bind with heamolgobin
- in cytoplasm of red blood cells in form of hydrogen carbonate ions
58
hydrogen carbonate ions
- almost 85% of carbon dioxide is transported as hydrogen carbonate ions in red blood cells
- water and carbon dioxide react, in reversible reaction, to form carbonic acid
- carbonic anhydrase, an enzyme in cytoplasm of red blood cells, catalyses this reaction
- carbonic acid then dissociates to form hydrogen ions and hydrogen carbonate ions
- haemoglobin then binds to hydrogen ions (and dissociates from oxygen), forming haemoglobinic acid
- hydrogen carbonate ions diffuse out of red blood cells and in exchange, chloride ions diffuse into red blood cells
- both these ions are negative, so this exchange maintains electrical balance of red blood cells, known as chloride shift
59
structure of the roots
- xylem is found at center of root, often resembling a star shape
- pholem found in between each of points of star shape
60
structure of the stem
- xylem found on inner edge of each bundle, closest to centre of stem
- phloem found in outer edge of each bundle, closest to surface of stem
- in between xylem and phloem is a layer of cambium
61
cambium
meristematic tissue, containing actively dividing pluripotent cells
62
structure of the leaf
- vascular bundle runs down centre of leaf as a vein and containts both xylem and phloem tissues
- xylem is towards top of leaf in each bundle whereas phloem is found towards bottom of leaf
63
2 components of phloem tissue
- sieve tube elements- living cells, no nucleus, contain few organelles
- companion cells- provide ATP required for active transport of organic substances
64
xylem cells
- dead and hollow
- do not contain any organelles or end walls, as result, stack on top of each other to make a continuous hollow column- ideal for transporting water and mineral ions
- xylem wall is also strengthened with a waterproof chemical, lignin
65
transport of water into the plant
- water is absorbed into plants through the root hair cells by osmosis
- root hair cells are adapted to maximise osmosis by having thin walls and a large surface area
66
transport of water to the xylem
- once the water has moved into the root hair cell by osmosis, it then travels to the xylem by either the symplast or apoplast pathway
67
symplast pathway
- through the cytoplasm
- water moves from cell to cell, towards xylem, by osmosis through cytoplasm and through gaps in each cell wall (plasmodesmata)
- each successive cell's cytoplasm has a lower water potential- enables water to move by osmosis
68
apoplast pathway
- through cell walls
- water can enter cell wall and move due to the cohesive force of water
- water molecules stick together, forming a continuous stream of water which move toward the xylem
- transports water faster, as there is little resistance to water in cell wall
69
# (stomata)
adaptations of plants
- dicotyledonous plants exchange gases through stomata
- stomata are tiny pores mainly on leaves which can open or close, determined by guard cells surrounding them
- this is a mechanism to help prevent excessive water loss by evaporation
70
xerophytes
plants with adaptations to reduce water loss and are therefore found in locations with limited water, e.g. the desert
example- marram grass
71
adaptations of marram grass
- curled leaves to trap moisture to increase local humidity
- hairs to trap moisture to increase local humidity
- sunken stomata to trap moisture to increase local humidity
- thicker cuticle to reduce evaporation
- longer root network to reach more water
72
hydrophytes
- plants which live in or on water, so require adaptations to survive in an excess of water
- e.g. water lillies which grow on surface of water
- short roots, very thin to no waxy cuticles, stomata being permanently open and on top surface of leaf- ensure no additional water is retained in plant
- leaves large, wide and on surface of water- esures enough light is absorbed for photosynthesis
73
transpiration
- the loss of water vapour from the stomata by evaporation
- measured using a potometer
74
4 factors that affect transpiration
- light intensity- positive correlation, more light causes more stomata to open= larger surface area for evaporation
- temperature- positive correlation, more heat means more kinetic energy, faster moving molecules and therefore more evaporation
- humidity- negative correlation, more water vapour in the air will make water potential more positive outside leaf, therefore reduces water potential gradient
- wind- positive correlation, more wind will blow away humid air containing water vapour, therefor maintaining water potential gradient
75
cohesion-tension theory
- water moves up a plant from the roots against gravity
- only possible due to cohesion-tension theory: cohesion, adhesion, root pressure
76
cohesion
- water is a dipolar molecule (slight negative oxygen and slight positive hydrogens)
- this enables hydrogen bonds to form between the hydrogen and oxygen of different water molecules
- this creates cohesion between water molecules- they stick together. Therefore water travels up the xylem as a continuous water column
77
adhesion
- when water molecules sticks to other molecules forming hydrogen bonds with the surface
- water molecules adhere to the lignin in xylem walls
78
root pressure
- as water moves into roots by osmosis it increases volume of liquid inside root and therefore pressure inside root increases- root pressure
- this increase in pressure in roots forces water above it upwards (positive pressure)
79
movement of water up xylem
1. water evaporates out of stomata on leaves. This loss in water volume creates lower pressure
2. when this water is lost by transpiration more water is pulled up xylem to replace it (moves due to negative pressure)
3. due to hydrogen bonds between water molecules, they are cohesive (stuck together). This creates a column of water within xylem
4. water molecules also adhere (stick) to the walls of the xylem. This helps to pull the water column upwards
5. as this column of water is pulled up the xylem it creates tension, pulling the xylem in to become narrower
80
translocation- mass flow hypothesis in plants
- transport of organic substances in a plant
- requires energy- active (co-transport)
- mass flow from source of production, the leaves, to the sink, site where organic substances are used up
81
source to sink explanation
- sucrose lowers water potential of source cell
- water enters by osmosis- increases hydrostatic pressure
- at same time respiring cell is using up sucrose so has more positive water potential
- water leaves sink cell by osmosis- hydrostatic pressure decreases
- source cell has higher hydrostatic pressure than sink cell so solution forced towards sink cell via phloem
82
# translocation
how sucrose transports from the source to the sieve tube element
- active transport of hydrogen ions occurs from the companion cell into the photsynthesising cells of the source
- this creates a concentration gradient and therefore the hydrogen ions move down their concentration gradient via carrier proteins back into the companion cells
- co-transport of sucrose with the hydrogen ions occurs via protein co-transporters to transport the sucrose into the companion cells. Sucrose then diffuses through plasmodesmata into the sieve tube elements
83
# translocation
movement of sucrose within the phloem sieve tube element
- the increase of sucrose in the sieve tube elements lowers the water potential
- water enter the sieve tube elements from the surrounding xylem vessels via osmosis
- the increase in water volume in the sieve tube element increase the hydrostatic pressure causing the liquid to be forced towards the sink
84
# translocation
transport of sucrose to the sink (respiring cells)
- sucrose is used in respiration at the sink, or stored as insoluble starch
- more sucrose is actively transported into the sink cell, which causes the water potential to decrease
- this results in osmosis of water from the sieve tube element into the sink cell (some water also returns to the xylem)
- the removal of water decreases the volume in the sieve tube element and therefore the hydrostatic pressure decreases
- movement of soluble organic substances is due to the difference in hydrostatic pressure between the source and sink end of the sieve tube element
