Biology Module 3: Miss Colenette Flashcards
What are Goblet cells?
Goblet cells are cells that are scattered throughout the ciliated epithelium along the trachea. They contain mucus glands that produce viscous mucus which is released into the trachea to trap pathogens and micro-organisms, before being swept into the throat by the cilia, and being swallowed and destroyed in the stomach.
How do Ciliated and squamous epithelial cells, smooth muscle, goblet cells, cartilage capillaries and elastic fibres help maintain and run the mammalian gas exchange system?
-Ciliated epithelial cells are found along the trachea and bronchi, with small cilia projections to sweep mucus and dust up the throat and down the oesophagus
-Squamous epithelial cells allow for very thin alveoli walls, shortening the diffusion pathway and speeding up gas exchange
-Goblet cells secrete viscous mucus to trap pathogens and dust, stopping them from reaching the lungs
-Cartilage is present on the trachea in places called tracheal rings, which allow the trachea to stay open whilst still being able to flex
-Smooth muscles regulate airflow by dilating to increase airflow and contracting when less air is needed
-Capillaries surround alveoli and are especially thin to slow erythrocytes and allow gases to diffuse
-Elastic fibres allow lungs to stretch and recoil, causing expiration to be passive
What is the structure of the trachea?
-It is channel shaped to allow air to enter the lungs, with C shaped rings of cartilage (tracheal rings, with gaps between them) to prevent it from closing, but allow it to flex
-This also prevents friction between the trachea and the oesophagus
-It is lined with goblet and ciliated epithelial cells, to trap dust and pathogens
-The walls contain smooth muscle and elastic fibres to allow the trachea to flex
What is the structure of the bronchi?
-Similar structure to the trachea, but has thinner walls and a smaller diameter
-Cartilage can therefore form full rings and irregular blocks along the bronchi length
What is the structure of bronchioles?
-Narrow tubes with thin walls, usually not containing cartilage
-They are lined with ciliated epithelium and get smaller closer to the alveoli
-They posses elastic fibres and smooth muscle to adjust size and regulate airflow, though this is not present in smaller bronchioles
What is the structure of alveoli?
-Located at the end of small bronchioles
-Consists of a single layer of squamous epithelial cells
-Also contains elastic fibres in the extracellular matrix
-Have an extensive network of capillary beds over them to facilitate gas diffusion
What are the muscles between the ribs called?
Intercostal muscles. These are examples of antagonistic muscles (muscles working in a pair) as they consist of both an external intercostal muscle and an internal intercostal muscle
What makes an effective exchange surface?
-Large SA/V ratio - larger area for diffusion to occur
-Moist surface - gas can dissolve before diffusing
-Short diffusion pathway - less distance for gas to diffuse across
-Maintained concentration gradient
-Ventilated - helps maintain gradient
-Permeable membrane
What is the process of exhalation and inhalation?
Exhalation:
EEE = Exhalation, External, rElax
1. The External intercostal muscles rElax (the internal contract)
2. The volume of the lungs decreases so the pressure inside the lungs increases to ~ atmospheric level
3. Air therefore rushes out the lungs
4. The diaphragm relaxes and becomes domed due to being displaced by the organs beneath it
Inhalation:
1.The Internal intercostal muscles relax (the external contract)
2. The volume of the lungs increases so the pressure decreases in relation to the atmosphere
3. Therefore air rushes into the lungs
4. The diaphragm contracts, becoming flat and displacing the organs beneath it
What are the 4 different scientific methods of measuring breathing?
- Vital capacity - the maximum volume of air that can inhaled/exhaled in one breath
- Tidal volume - the volume of air exhaled/inhaled in a normal breath
- Breathing rate - number breaths 1 mins
- Oxygen uptake - O2 absorbed in a given time
How do you calculate Minute ventilation?
Minute ventilation = Tidal volume x Breathing rate
How do you calculate Oxygen consumption over a period?
Oxygen consumed over a period = Oxygen consumed (dm^3) / Time (s)
What is the opperculum?
-The opperculum is a bony plate that covers the gills in bony fish, eg, mackerel
-The opperculum both protects the delicate gills and moves outward to help draw water into the fish
What is the structure of gills on bony fish?
-The gills, situated on either side of the head, is covered by the opperculum
-The gills consist of 2 rows of gills filaments attached to 1 bony gill arch
-There are a number of gills arches present in 1 gill
-Surface of gill filaments folded into secondary lamelae to provide an extremely large surface area for oxygen to diffuse on
How does ventilation occur in bony fish?
- Opperculum and mouth expand, drawing water into gills in similar way to lungs with air
- Water runs over gill arches, gill filaments and gill lamelae/plates, which seems red due to rich blood supply
- Capillaries run around the gill lamelae in a coutercurrent flow, to maximise the rate of oxygen diffusion
- The water leaves the gills via the back of the opperculum
What is couter-current flow?
-The flow of the blood is in the opposite direction to the flow of the water
-This means that a favourable concentration gradient is maintained, even though the concentration isn’t as large as if the flow was parallel
How do insects ventilatory systems work?
- Air enters the insect via holes in the chitin exoskeleton called spiracles, which may have muscular sphincters that can open or close depending on the air requirements of the insect
- The air enters a trachea under the exoskeleton, which is supported by rings of chitin
- This splits further into small trachioles that deliver O2 directly to respiring cells, that contain tracheal fluid, which can be withdrawn during high respiration periods
- This means that gaseous exchange in insects is essentially passive as O2 diffuses from an area of high concentration in the air to the low concentration in the insect
- The CO2 exchange occur in the opposite direction
How does tracheal fluid regulate ventilation in insects?
-The tracheal fluid covers the end of the trachioles
-When the cells around them respire heavily/anarobically, eg whilst flying, they produce lactic acid as a waste product
-This lowers the psi of the cells and causes the tracheal fluid to move via osmosis into adjacent cells
-This exposes more trachiole area, and therefore the surface area available for gas exchange to occur on, so increase the rate of ventilation
-Some trachioles or tracheal have a more flexible wall and are called air sacs, which help increase the rate of flow of the gas through the insect, as more air makes up the residual volume
Why has ventilation in insects evolved as it is?
- It evolved due to the insects body being split into 3 very small sections, the head, the thorax and the abdomen, so there is little space for lungs
- Insects have a open-circulatory system that allows O2 to be delivered straight to active tissues that are respiring, like flight muscles
- O2 diffusion is quicker and more effective in air than in blood
How are xylem and phloem tissues specialised for their function, and what is their structure?
Go to Hodges yr 12 and find the 2 cards before studying them after the next 10 cards
What are the 3 ways H2O can move into the xylem vessels?
-Water has to move from the root hair cells, through the dermis (exodermis and then the endodermis) to reach the xylem
-It does this in 3 ways:
1. Apoplast pathway
2. Symplast pathway
3. Vacuolar pathway
What is the apoplast pathway?
-The movement of water through the cortex cell walls and intercellular space
-Cohesive/tensive forces acting on cell walls pulls H2O up plant
-The fastest of the 3
1. Water moves into cell wall
2. Moves through cell wall
3. May move from cell wall to cell wall across intercellular space or just move to adjacent cell walls
What is the symplast (+vacuolar) pathway?
-Movement of water through cell cytoplasm
-Moves between cells via plasmodesmata
-Each cell further from roots has lower psi, so water drawn up plant
1. Water enters cells across the plasma membrane
2. May move from cell to cell via plasmodesmata
3. May move from cell to cell across adjacent cell walls and plasma membranes
Vacuolar:
-Slowest
-Like symplast but moves from vacuole to vacuole
What is the Casparian strip and what is its function?
-Found in endodermis (inner cortex)
-Strip of waxy material called suberin that is impermeable to water
-Forces water and ions into cytoplasm, and into symplast pathway
-Means water and ions are under cellular control and can be moved into the xylem
What processes drive Transpiration?
Root pressure:
-Root cells around xylem move minerals into xylem, via active transport, causing water to move into xylem via osmosis and cause the movement of water up plant
Cohesive-tension theory:
-Forces in cohesion cause H2O molecules to adhere to xylem walls and cohere to each other, increasing hydrostatic pressure and moving H2O up vessel
Capillary action:
-Due to small xylem diameter, hydrostatic pressure increased, and water moved up vessel
Osmosis:
-Water movement passive as the roots have a high water potential and the leaves have a low water potential
-Therefore water drawn upwards via osmosis
What evidence is there for the cohesive-tension theory?
Diameter changes:
-The diameter of a plant changes throughout the day
-This is because tension and transpiration are at their greatest during the day, so the plant diameter decreases as xylem’s cave slightly
Broken Xylem vessels:
-Pressure is lost when vessels are broken, and so cohesive forces are broken
-This means H2O cannot be pulled up any longer and air replaces it, instead of H2O leaking out
What factors affect transpiration?
Airflow:
-Increases rate due to a good airflow removing H2O vapour , so maintaining a good concentration gradient for diffusion out of the leaf
Humidity:
-Measure of moisture in the air
-Decreases rate as when air is saturated, concentration gradient is lost
Light intensity:
-Increases rate due to guard cells responding and opening stomata, increasing H2O loss
Temperature:
-Increases rate as at a higher temperature, molecules kinetic energy is increased and so diffusion rate increases
What are sinks and sources, and what are some examples of them?
Sinks are tissues or cells that will use transported assimilates in metabolic processes, for example, roots or stems.
Sources are tissues or cells that provide and synthesise assimilates for the rest of the plant, eg, leaves or storage organs.
What are the 2 pathways assimilates can be loaded into the sieve tube elements?
The symplast pathway:
-Assimilates stored in plant cell permanent vacuole
-Moved passively into the sieve tube element via plasmodesmata
-This is mainly driven by changes in the cells ψ
The apoplast pathway:
-Assimilates diffuse through cell walls and intermembrane spaces
-When companion cells reached, assimilates actively loaded into sieve tube elements
What is the process of active loading?
- H^+ ions (acting as a co-transporter) will move via active transport outside of the plasma membrane
- This will cause the concentration of H^+ ions inside the cell to decrease and they will diffuse (facilitated) back through the membrane, bringing with it sucrose through a co-transporter protein
How does translocation between a source and sink occur?
- Assimilates actively loaded into sieve tube elements, decreasing the element’s water potential
- This causes water (from the xylem or surrounding cells) to move into the sieve tube element via osmosis, increasing the hydrostatic pressure of the phloem at the source
- This causes the water and assimilates to move down the pressure gradient, from an area of high pressure at the source to an area of low pressure at the sink
- The assimilates are actively loaded into the companion cells, raising the water potential of the element’s at the sink, causing water to move out via osmosis, and lowering the hydrostatic pressure of the phloem at the sink
- This maintains a favourable pressure gradient for mass flow to continue to ocur
What is some evidence for and against the mass flow hypothesis?
For:
-Tracers and radioactive elements can be seen under microscopes supporting the mass flow hypothesis
-Translocation occurs much faster than would be expected with just diffusion
-Companion cells contain mitochondria, which when inhibited, can no longer produce ATP, and translocation stops
-When a stem is cut, sap leaks out due to the loss of hydrostatic pressure
Against:
-Not all solutes move at the same speed, but sucrose does regardless of the concentration gradient
-Sieve plates seem to be obstructive
What are Xerophytes and how are they adapted? (marram grass + cacti)
-Plants with structural and physiological adaptations to aid their survival in hot, dry and arid conditions with little water
-Fleshy succulent leaves allows H2O storage during arid periods
-Hinge cells lose turgidity quickly and shrink, exposing the waxy cuticle to the air, and rolling the leaf, creating a humid space inside it
-Reduced leaf size, reducing the SA/V ratio for transpiration to occur
-Stomata open at night, which reduces the H2O loss and allows the plant to take in CO2 for photosynthesis during the day, stored as malic acid
-Sunken stomata + spines/hairs, trap moist air around the stoma reducing the concentration gradient
-Fewer stomata, fewer pores=less H2O loss, and found in upper epidermis
-Thick waxy cuticle, stopping H2O loss from top of leaves
What are Hydrophytes and how are they adapted?
Plants with physiological and structural adaptations that allow them to inhabit aquatic areas.
-Floating leaves, leaves are thin and flat, containing Aerenchyma (large air spaces) for buoyancy, keeping them at the surface to allow for optimum light intensity for photosynthesis
-Thin waxy cuticle, very thin as H2O loss not concern
-Stomata on upper epidermis, allowing gas exchange in air, not water
-Reduced roots and transport tissues, as nutrients and water can be absorbed by tissues and cells directly from the water
