Exchange and Transport Flashcards
Discotyledan
- 2 seed leaves
- xylem and phloem in vascular bundles
- schlerenchyma for strength and support
3 pathways of water in plants
Apoplast- water passes through spaces in cell walls (mass flow)
Symplast-water enters via cytoplasm(travels to next cell thru plasmodesmata
Vacuolar- like symplast but thru vacuole (osmosis)
Water potential
wp= tendency of water molecules to move from high water potential to low water potential
cell in pure water (0) = turgid
cell in sugar solution= water moves out
flaccid then plasmodysed
Transpiration
Loss of water vapour from the stomata in the upper part of the plant (usually leaves) \+provides water for photosynthesis \+transports minerals&ions \+maintains cell turgidity \+gives water to cool down on hot day
Pathway of transpiration
Water—>xylem—>spongy mesophyll cells (osmosis)
- Water vapour formed in mesophyll spaces & apoplast pathway
- water evaporates off sm
- Vapour diffuses thru stomata
- moves along wp gradient
- water vapour inside>wv outside
Factors affecting transpiration
- light intensity
- temp
- humidity
- wind air movement
- thick cuticle
Potometer
-leafy shoot freshly cut
-coloured dye (see air bubble)
-set up under water
-lift up to get air bubble
Control- type of leaves, volume of water
how water moves up stem
Root pressure- endodermis moving minerals in
Transpiration pull- water molecules attracted to eachother (cohesion)
Capillary action- (adhesion) water molecules attracted to side of xylem pulling the water in
marram grass
Leaf rolled to trap air inside
- thick waxy cuticle
- hair on lower surface reduce air movement
- stomata are in pits (trap moisture)
Xerophytes
plants adapted to prevent water loss
-cells have low water potential (salty)
so water fills back up
-dense spongy mesophyll (less SA for evaporation
Succulents
- store water in stem
- leaves reduced to spines (less SA)
- stem green (photosynthesis)
Hydrophytes
plants that live in water
- large air spaces in leaf (keep afloat)
- stomata on upper epidermis to get sunlight
How do hydrophytes transpire
Have hydathodes in tips or margins of leaves
-can release water droplets which may then evaporate on leaf surface
Xylem features
- lignin impregnates the cell (strength)
- waterproof
- long column of dead cells (hollow)
- stops column collapsing
- spiral (broken rings)
- 2 way
Translocation
Movement of sugars and assimilates in plant (sucrose)
- transported in phloem
- source —> sink
Phloem
transports sucrose & amino acids in phloem tissue
- made of sieve tubes and companion cell
- one way
Companion cells
- in between sieve tubes
- large vacuole (keep turgid)
- dense cytoplasm
- many mitochondria (produce ATP) for active transport
Sieve tube elements
- used for mass flow of sap
- no nucleus or cytoplasm
- sieve tube plates at end
- thin walls (short dp)
- callose will block tube if infection occurs
Importance of transpiration
- transports water & minerals around plant
- maintains cell turgidity
- supplies water for growth & elongation
- on hot days evaporation gives water supply to cool down
Active loading
ATP splits forming H+ ions
which actively transports out of companion cell to tissue
-the H+ ions pick up sucrose (co transport)
-the sugar is brought back in by facilitated diffusion (conc grad)
- then diffuses through plasmodesmata into sieve tube
Factors influencing need for transport system
- size (diffusion pathway increased)
- SA:Vol (more area to diffuse)
- level of metabolic activity (requires more energy)
Features of a good transport system
- fluid or medium to carry nutrients
- pump to create pressure (pushing fluid)
- exchange surfaces (enable substances to enter and leave)
adv of double circulation
Fish-blood pressure drops as it passes thru tiny capillaries
Mammals-blood pressure must not be too high in pulmonary (damage lung capillaries)
-heart can increase pressure after passed thru lungs
Double circulatory system
Heart —> body —> heart —>lungs —> heart
Arteries
- carry blood away from the heart
- thick walls (high pressure)
- carry oxygenated (apart from pulmonary artery)
Arterioles
Small blood vessels that distribute blood out to capillaries from artery
- layer of smooth muscle
- contraction restricts diameter of arteriolar
Capillaries
- very thin walls
- lumen narrow
- walls have single layer of flattened endothelial cells
- walls are leaky
Venules
Bloods flows into venules from capillaries
-thin layers of muscle and elastic tissue & thin outer layer of Collagen
veins
- carry blood back to heart
- thin walls(carries blood under low pressure)
- lumen relatively large
- contains valves (prevent backflow)
Open vs closed circulatory system
Open- means that blood is not always held in blood vessels, instead blood flows thru body cavity (tissues bathed in blood)
Closed-larger animals blood stays entirely inside blood vessels ( tissue fluid bathes the tissues)
+higher pressure
+more rapid delivery of O2
Movement of fluids
arteriole–>venule
-hydrostatic pressure highest at arteriole end
this causes the water to move out of vessel
-oncotic pressure puling water into
lymph system
- drains excess tissue fluid out of tissues and returns it to the blood system
- lymph fluid contains lymphocytes produces in lymph nodes
external features of heart
-cardiac muscle- myogenic
-coronary arteries lie over surface of heart and supply oxygenated blood to heart muscle
if this is restricted then could cause CHD,angina etc
Cardiac motions
Atrial systole- atria contract pushing blood into ventricles
ventricular systole-ventricles contract pushing blood out of heart
diastole- muscle relaxes allowing atria to fill
Wave of excitation
SAN (sinoatrial node) sends electrical impulses –AVN (atrioventricular node) – through branches in bundle of his – then to purkyne fibres
bicarbonate buffer system
-CO2 diffuses out of tissue into blood
-CO2 combines with water= carbonic acid
(sped up by carbonic anhydrase)
-this dissociates to H+ & HCO3-
-HCO3 ions diffuse out of RBC
-maintain PH chloride shift into RBC
-Oxyhaemoglobin dissociates by H+ions
-H+ ions join with haemoglobin =HHb
-Oxygen released into blood
bohr effect
to the right on the graph
- when theres more CO2 the haemoglobin becomes less saturated with oxygen
fetal haemoglobin
-shift to left of graph
fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin
-this is because fetal haemoglobin must be able to associate to oxygen where oxygen tension is low enough to make adult haemoglobin release oxygen
factors effecting the need for an exchange system
- size
- SA:V ratio
- level of activity
features of good exchange surface
- good bloody supply
- thin walls(short diffusion pathway)
- large SA:V ratio
inhalation
- diaphragm contracts (flattens)
- external intercostal muscles contract & raise ribs
- volume of chest cavity increases
- pressure in chest cavity decreases
- air moves into lungs
exhalation
- diaphragm relaxes (pushed up)
- external intercostal muscles relax & ribs fall
- volume of chest cavity decreases
- pressure in chest cavity increases
- air moves out
alveoli adaptations
- squamous epithelium
- short diff pathway
- elastic tissues stretch during inspiration & recoil during expiration
airways
- trachea has cartilage to prevent collapse (C&D shaped rings
- mucus made from goblet cells
tissues in the bronchus
- ciliated cells
- goblet cells
- smooth muscle cells
- chondrocytes in cartilage
spirometer
-measures lung volumes precautions -subject should be healthy -soda lime needs to be fresh -needs to be clinical grade O2 -water chamber not overfilled
Bony fish
-use gills to absorb O2 from water
each gill has 2 rows of gill filaments-primary lamellae
filaments are thin & folded into secondary lamallae= large SA
ventilation in bony fish
floor of mouth moves down -water drawn into buccal cavity -mouth closes -floor is raised -water pushed thru gills -operculum moves outwards movement reduces pressure in operculum cavity (helping water flow)
countercurrent flow in bony fish
-blood flows along gill arch and out along fillaments to secondary lamallae
-the blood then flows thru cappilaries in the opposite direction to the flow of water over lamallae
to absorb the max amount of oxygen from the water
insects tracheal system
-air enters via spiracles the air is transported thru tubes called trachaeae
-these divide into smaller tubes called tracheoles
the tracheoles are filled with tracheal fluid
insect adaptations
locusts can alter the size of their abdomen by specialised breathing movements
some insects move the wings to alter the size of the thorax
multicellular organsims need for transport system
demand for oxygen is high for aerobic respiration
high metabolic rates as large in size
tissue fluid
watery substance containing glucose, amino acids, oxygen delivered to cells whilst removing waste
formation of tissue fluid
hydrostatic pressure (highest at arteriole end) pushes nutrients out
oncotic pressure (brings fluid back in waste)
after tissue fluid has bathed in cells becomes lymph fluid
