unit 3 bio (plant transport and energetics) Flashcards
external structure of leaf
leaf blade/lamina: thin and large surface area to volume ratio
petiole (leaf stalk): holds leaf in position to absorb maximum light energy
cuticle: transparent, waxy layer that reduces water loss through evaporation and allows light to enter the leaf
function of epidermis
upper and lower epidermis: single layer of closely-packed cells that protect the inner parts of a leaf
function of mesophyll cells
palisade mesophyll: elongated and cylindrical cells, contain the largest number of chloroplasts in the leaf & main sites of photosynthesis (can trap more light near leaf surface)
spongy mesophyll: loosely packed and irregular shaped cells, contain chloroplasts & covered with thin film of moisture to allow for dissolving of gases to diffuse into cells
fill in the blanks:
palisade mesophyll: ___ and ___ cells, contain the largest number of chloroplasts in the leaf & main sites of photosynthesis (can trap more light near ___)
spongy mesophyll: ___ packed and ___ shaped cells, contain chloroplasts & covered with thin film of ___ to allow for ___ to diffuse into cells
elongated; cylindrical; leaf surface
loosely; irregular; moisture; dissolving of gases
function of intercellular air spaces in leaf
allow for rapid diffusion of co2 and oxygen in and out of mesophyll cells
function of vascular bundle in leaf
xylem: transports water and dissolved mineral ions from roots to leaves of plants + provides mechanical support to the plant, provide mechanical support to the plant
phloem: transports sucrose and amino acids from the leaves to other parts of the plant
why do plants transport sugars in the form of sucrose instead of glucose
sucrose is a disaccharide while glucose is a monosaccharide, so it contains more energy than glucose and is more efficient for transport and storage. also prevents cells from immediately taking up glucose for respiration.
function of chloroplasts
contains chlorophyll that absorb light energy for photosynthesis
function of guard cells
control the opening and closing of the stomata that allows for gaseous exchange
function of stoma
open in the presence of light to allow co2 to diffuse in and oxygen to diffuse out of the leaf
close when it is too hot to prevent water loss
how do stomata open?
light triggers active uptake of potassium ions from nearby cells by guard cells, lowering their water potential. water enters guard cells via osmosis, causing walls of guard cells to become turgid. the uneven thickness of the cell walls of the guard cells cause them to bow with water intake, opening the pore of the stomata
how do stomata close?
potassium ions diffuse out of the guard cells, increasing their water potential. water leaves guard cells via osmosis, causing guard cells to become flaccid again and the stomata to close
fill in the blanks: light triggers ___ of ___ ions from nearby cells by guard cells, lowering their ___. water enters guard cells via osmosis, causing walls of guard cells to ___. the ____ of the ___ of the guard cells cause them to ___, opening the pore of the stomata
active uptake; potassium; water potential; become turgid; uneven thickness; cell walls; bow with water intake
fill in the blanks: ___ diffuse out of the guard cells, increasing their water potential. water leaves guard cells via osmosis, causing guard cells to ___ again and the stomata to close
potassium ions; become flaccid
adaptations of xylem vessels
- walls are strengthened with lignin deposits to provide mechanical support for the plant
- hollow and contain dead cells without cross walls to allow water to be transported more efficiently from the roots to aerial parts of the plant with less resistance
fill in the blanks:
- walls are strengthened with ___ to provide ___ for the plant
- ___ and contain dead cells without ___ to allow water to be transported more ___ from the roots to aerial parts of the plant with ____
lignin deposits; mechanical support
hollow; cross walls; efficiently; less resistance
adaptations of phloem vessels
consist of sieve tubes that are accompanied by companion cells that contain many mitochondria to release the necessary energy for the active transport of manufactured food in sieve tubes
fill in the blanks:
consist of ___ that are accompanied by ___ cells that contain many ___ to release the necessary energy for the ___ of ___ in sieve tubes
sieve tubes; companion; mitochondria; active transport; manufactured food
how do roots absorb water and mineral ions
mineral ions enter root cells via diffusion and active transport while water enters root hair cells via osmosis
adaptations of root hair cells
- contain more mitochondria than typical plant cells to release more energy for the active transport of mineral ions into the cell
- long and narrow extension that increases the surface area to volume ratio of the cell to increase the rate of absorption of substances into the cell
- more concentrated cell sap to provide a steeper water potential gradient between cell and the surroundings to increase the rate of osmosis of water into the cell
fill in the blanks:
- contain more ___ than typical plant cells to ____ for the ___ of mineral ions into the cell
- long and narrow extension that increases the surface area to volume ratio of the cell to increase the ____ of substances into the cell
- more concentrated ___ to provide a steeper ___ between cell and the surroundings to increase the rate of ___ of water into the cell
mitochondria; release more energy; active transport
rate of absorption
cell sap; water potential gradient; osmosis
what is transpiration
the loss of water through the stomata in the form of water vapour
how does transpiration work
water evaporates from surface of leaves, removing water from xylem vessels. this results in a suction force which pulls water up xylem vessels against gravity.
there is a concentration gradient between the inside of the leaf and the surrounding air as water vapour is more concentrated in intercellular air spaces. this causes water to diffuse out the stomata
benefits of transpiration
- pulls water and minerals from the roots to the stem and leaves
- evaporation of water from leaf cells removes latent heat of vapourisation, cooling the plant
- water transported to the leaves is used for photosynthesis, keeping cells turgid and replacing lost water
fill in the blanks: more water is lost by transpiration through the ___ surface of the leaf because it ___ (___ surface has more cells used for ___)
lower; contains more stomata
upper; photosynthesis
what happens when rate of transpiration is too high
wilting occurs as plant does not have enough water — it causes a reduction in the rate of transpiration, allowing less water to be lost, but also decreases rate of photosynthesis
factors affecting rate of transpiration
temperature
light intensity
humidity
how does temperature affect rate of transpiration
as temperature increases, the rate of transpiration increases until a certain point where it has reached its maximum rate
how does light intensity affect the rate of transpiration
more transpiration occurs in the presence of light as it can only occur when stomata are open as it occurs during gaseous exchange between the plant and the environment, and size of stomata are affected by the presence of light
how does humidity affect the rate of transpiration
intercellular air spaces are generally saturated with water vapour. this creates a concentration gradient between the inside of the leaf and the surrounding air, causing water vapour to diffuse out the leaf. if the air is drier, there will be a steeper concentration gradient that increases the rate of transpiration. if there is higher humidity, there is a less steep concentration gradient which decreases the rate of transpiration
redox reaction
oxidation: lose hydrogen ions
reduction: gain hydrogen ions
where does light dependent stage of photosynthesis occur
thylakoid membrane in the grana
products of light dependent stage of photosynthesis
NADPH and ATP produced from NADP+ and ADP
process of photosynthesis
water undergoes photolysis and is split to form oxygen, hydrogen ions, and electrons. light energy absorbed by the chlorophyll within the thylakoid is channeled into the formation of NADPH and ATP molecules. electrons and hydrogen are used to reduce NADP to NADPH. an inorganic phosphate is added to ADP to form ATP
3 stages of light independent stage
carbon fixation, reduction, regeneration of RuBP
calvin cycle processes
- CO2 fixation: co2 molecules are attached to RuBP molecules in the presence of rubisco enzyme to produce 3GP (glycerate-3-phosphate)
- Co2 reduction: oxidation of NADPH reduces glycerate-3-phosphate to form triose phosphate, turning NADPH into NADP
- regeneration of RuBP: ATP is used to divide triose phosphate molecules to form RuBP molecules which can then combine with CO2 to continue the cycle
how is glucose formed during photosynthesis used
- used immediately by cells for respiration
- converted to starch and stored temporarily
- converted to sucrose which is transported to other parts of the plant
- converted to amino acids to form proteins used for the synthesis of new protoplasm
- becomes fats
factors affecting rate of photosynthesis
light intensity, co2 concentration, temperature
how does light intensity affect photosynthesis
increasing light intensity increases the rate of photosynthesis until a constant rate is reached where the rate is at its maximum
how does co2 concentration affect photosynthesis
higher co2 concentration increases the rate of photosynthesis until a constant rate is reached where the rate is at its maximum
because more co2 molecules are available to bind to the active sites of rubisco enzymes until they are fully occupied
under natural conditions, co2 is an important limiting factor as atmospheric co2 concentration is only 0.03%
how does temperature affect photosynthesis
as temperature increases to the optimum, the rate of photosynthesis increases. as temperature increases beyond the optimum, rate of photosynthesis decreases. increase in temperature → increase in kinetic energy → increase in rate of effective collision between enzyme and substrate → increase in product formation
because
too cold: low kinetic energy of enzyme and substrate, rate of enzyme substrate complex formation is low
too hot: photosynthetic enzymes will be denatured
what is aerobic respiration
process by which glucose is broken down in the presence of oxygen, generating energy and producing carbon dioxide and water as by-products
equation of aerobic respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O
respiration vs breathing
respiration: chemical process of releasing energy of glucose and occurs within cells
breathing: physical process of moving air in and out of the lungs and occurs in the respiratory system
what is anaerobic respiration
the breakdown of glucose in the absence of oxygen to generate energy with lactic acid as a byproduct
why does anaerobic respiration occur
occurs when energy from aerobic respiration alone is insufficient to meet increased energy demand (e.g. during exercise)
what happens to lactic acid generated by anaerobic respiration
buildup of lactic acid decreases the pH of our blood, which affects the functioning of our enzymes. hence, it is transported to the liver to convert it back to glucose. the amount of oxygen needed to carry out this process is called oxygen debt
breathing and heart rate are still high after exercise to repay the oxygen debt
adaptations of alveoli
- wall made up of a single layer of cells to shorten diffusion distance to allow for a higher rate of gaseous exchange
- rich supply of blood capillaries around alveolus to maintain concentration gradient of gases for higher rate of gaseous exchange
- capillaries are extremely narrow to allow for a single file of red blood cells to pass through, increasing the surface area for gaseous exchange
- thin film of moisture covers inner surface of alveolus to keep alveolar wall flexible and allow oxygen to dissolve
fill in the blanks:
- wall made up of a ___ to shorten __ to allow for a ___ rate of gaseous exchange
- rich supply of blood capillaries around alveolus to __ of gases for higher rate of ___
- capillaries are ___ to allow for a ___ of red blood cells to pass through, increasing the ___ for gaseous exchange
- ___ covers inner surface of alveolus to keep alveolar wall ___ and allow oxygen to dissolve
single layer of cells; diffusion distance; higher
maintain concentration gradient; gaseous exchange
extremely narrow; single file; surface area
thin film of moisture; flexible
function of trachea
contains cilia that sweep away dust-trapped mucus away towards the pharynx
path of air when we breathe
- air enters nostrils. dust particles and bacteria in the air are trapped by nose hairs
- air travels through pharynx and larynx
- air reaches trachea where it is further cleansed, warmed, and moistened. remaining dust particles are trapped by mucus secreted by gland cells and swept by cilia up towards the throat to be expelled by the body
- air reaches the lungs, travels through bronchi and bronchioles into the alveoli where gaseous exchange takes place
what happens when we breathe in
- when we inhale, external intercostal muscles contract while internal intercostal muscles relax
- ribcage moves upwards and outwards
- diaphragm contracts and flattens
- volume of thoracic cavity increases
- lungs expand which causes a decrease in air pressure in the lungs. air is forced into the lungs
what happens when we breathe out
- external intercostal muscles relax and internal intercostal muscles contract
- ribcage moves inwards and downwards
- diaphragm relaxes and arches upwards
- thoracic volume decreases
- air pressure in lungs is higher than that of the surroundings, forcing air out of the lungs
toxic substances in cigarettes
nicotine
tar
carbon monoxide
effects of nicotine
stimulates body to produce adrenaline which increases heart rate and raises blood pressure
increases risk of coronary heart disease
effects of tar on respiratory system
causes cells in lung tissue to multiply uncontrollably and grow into a tumour
effects of carbon monoxide
haemoglobin has a higher affinity to CO than O2, hence it permanently binds to haemoglobin and prevents oxygen from doing so, reducing the ability of blood to carry oxygen, preventing oxygen from being transported around the body
causes shortness of breath and increased load on the heart to supply enough oxygen → increases risk of coronary heart disease
risks of smoking (diseases)
emphysema
bronchitis
atherosclerosis
lung cancer
what is emphysema
breakdown of alveolar walls
walls of alveoli weaken and break down → decrease in surface area for gaseous exchange, making it less efficient → reduced elasticity of lungs → wheezing and breathlessness
what is bronchitis
inflammation of windpipe or bronchi → excess mucus secreted → cilia become paralysed → dust-trapped mucus cannot be removed → blocked airways → coughing and lung infections
what is atherosclerosis
buildup of plague in arteries that makes them narrower and harder for blood to pass through → heart disease, stroke
effects of lung cancer
tumour in lung occupies air spaces and destroy the alveoli, decreasing surface area for gaseous exchange. less oxygen is absorbed into the bloodstream and less carbon dioxide is removed from it
treatments: chemotherapy, radiotherapy, removal of tumour and part of lung
