Hormones (5) Flashcards
what are the 2 roles of cytokinins in plants
cell division promote lateral bud growth
what is apical dominance
a condition where vertical growth supercedes lateral growth in a plant. this is controlled by auxins, where in high concentrations can inhibit growth but on the whole promote it
why does mimosa pudica respond to its external stimulus in the way it does
the rapid response frightens large herbivores and dislodges insects on its leaves.
what are the 3 roles of ABA- abscisic acid in plants
seed dormancy stomatal closure during abiotic stress antifreeze production
state the 6 roles of auxin hormones in plants
- to control cell elongation 2. to promote apical dominance- terminal bud growth i.e. the auxins in the apices diffuse down to lower branches 3. inhibit lateral bud growth 4. inhibit abscission (leaf fall) 5. root initiation 6. a selective weedkiller
outline the chemical defence against herbivory beginning ‘ph…….’
Pheromones are chemical substances released into the environment which affect the behaviour or physiology of other members of the same species.
state the commercial uses of auxins and ethene
ETHENE: fruit ripening AUXINS: rooting powder hormonal weed killers
what causes seed dormancy
ABA in high concentrations inhibits seed germination (the antagonist of GA).
state the 5 key plant hormones
Auxins (group of chemicals) Gibberellins- GA Ethene ABA - abscisic acid Cytokinins
describe how geotropism affects root growth
Gravity modifies the distribution of auxins so that they accumulate on the lower side of the root. In high concentrations they inhibit root growth, causing the root to bend downwards.
SACCHARIDES stored food is…. enzymes and intermediates in digestion are…. translocated products is…. role is growth and development is….
…carbohydrates eg. starch …amylase to break down starch to maltose, maltase to break down maltose to glucose …sucrose …respired to release energy/ATP and synthesis into cellulose and other wall substances
where were gibberellins originally discovered
in a fungal parasite of rice in Japan, causing them to growing unusually tall. It was discovered to be produced by the plants themselves.
describe how geotropism affects shoot growth
- gravity modifies the distribution of auxins in the shoots
- auxins tf accumulate on the lower side of the shoot and stimulate a higher rate of growth there
- this causes it to bend upwards
outline the blood glucose cycle with hormones
- The liver stores glucose as glycogen.
- Glucagon is secreted by the pancreas when blood glucose levels fall.
- Glycogen is hydrolysed into glucose.
- Glucose is absorbed by the small intestine and is released into the bloodstream after eating. Change detected in Islets of Langerhans (sensory receptors).
- Insulin is secreted by the pancreas when blood glucose levels increase.
- Excess glucose is stored in the liver.
what is the overall function of cytokinins
growth and division
does using two plants affect the validity of results in an experiment
If they are both the same species of plant, it will increase validity because the chance of the results coming from an outlier decrease. If they are from different species, validity decreases.
what is the name of the breakdown of glycogen to glucose
glycogenolysis
which cells produce the hormones in the pancreas and what is their main function
how is secretion controlled
the alpha cells in the islets of Langerhans produce glucagon
the beta cells in the islets of Langerhans produce
function: fat and carbohydrate metabolism
the pancreas acts as the control centre + effector
what is the benefit of apical dominance to plants
It promotes growth towards the light to maximise rate of photosynthesis.
If the apex/cells that are elongating are removed (eg. by a herbivore) there is a removal of the source of vertical growth, resulting in lateral buds growing which will bend upwards towards the light.
explain the commercial use of auxins in rooting powder
application of auxins to cut shoots stimulates production of roots, making propagation easier
what is antagonism (plants)
hormones having opposite effects so that the balance between them determines the response of the plant
what are the 2 roles of ethene in plants
fruit ripening promotes abscission
how do auxins generally affect apical shoot growth
Auxins are synthesised in meristem cells in apices
Auxins diffuse away from the apex of the shoot.
Auxins bind to receptor sites and affect cell wall plasticity. Vacuoles develop and low pH develops. Low pH keeps cell walls flexible, so they expand and stretch as water enters vacuole.
Large vacuole forms and enzymes break down auxins, inhibiting further cell elongation. Cell wall becomes rigid.
how can one recognise acini
they are darker stained berry-like clusters
when do plants lose their leaves (abscission)
Deciduous: annually or seasonally
Coniferous: throughout the year
explain briefly antifreeze production in plants
so that their membranes are not disrupted in the winter, leading to death, plants have evolved to have solutes, such as polysaccharides, amino acids and proteins, in the cytoplasm and sap of vacuoles to lower their freezing point, and are only produced in the winter. Thought to be linked to ABA.
what is a cutting, in terms of propagation
a small piece of the stem of the plant, usually with a few leaves
give an example of plant hormone synergism
auxins working with gibberellins to promote stem elongation (internodes)
what is meristem
undifferentiated tissue from which new cells are formed because cells are actively dividing, at the tip of a stem or root and cambium in vascular tissue.
what are the 5 stages of increasing blood glucose levels using glucagon
- Blood-glucose levels too low.
- Hepatocytes (glycogenolysis) and fat cells (gluconeogenesis) are targeted
- Glucagon activates enzymes to convert glycogen to glucose GLYCOGENOLYSIS
- Glucagon stimulates formation of glucose from non-carbohydrate sources; amino acids etc. GLUCONEOGENESIS
- Increases use of fatty acids in respiration
what is the overall function of ABA- abscisic acid
low production/ low growth
what is an internode
the part of the plant between branch points
what are 3 advantages and 1 disadvantage of using microorganisms to produce insulin to treat diabetics
(+) insulin produced by microorganisms is a cheaper source/more reliable/large scale production source
(+) more rapid response
(+) smaller chance of immune/allergic response
(-) ethical/religious objections to animal insulin
what is an additional benefit of synthetic auxins are weedkillers
they are simple to produce, cheap, low toxicity to mammals, they are specific to the weeds that they kill
what is a limitation of using a graph showing two distinct lines to give evidence of a difference when the dependent variable is changed
Differences may appear to be significant, but are not necessarily statistically different. The standard deviation of each result is needed to carry out a statistical test eg. unpaired t-test. The lowest concentration where the difference was significant would be the minimum concentration having an effect.
outline the 6 steps in insulin production and secretion from a cell
- RESTING STATE: the ATP + V-G ion channels in the membrane of the ßeta-cells are: K+ OPEN (ATP-sensitive) so K+ ions diffuse out of the cell. Ca2+ (V-G) CLOSED potential difference across membrane: -70mV
- when BLOOD-GLUCOSE LEVELS are too high, glucose moves into the cell by transporter protein and is metabolised in mitochondria to produce ATP (cellular resp.)
- ATP CLOSES K+ ATP-sensitive ion channels, K+ ions accumulate inside cell, tf inside the cell is less negative
- potential difference depolarised to -30mV
- Therefore Ca2+ voltage-gated channels open. Ca2+ enter the cell.
- Secretory vesicles of insulin fuse with csm and release the insulin they contain by exocytosis
what is the name of the conversion from glucose to glycogen
glycogenesis
what is the endosperm in a seed
the site of starch
PROTEIN stored food is…. enzymes and intermediates in digestion are…. translocated products are…. role is growth and development is….
…proteins …proteases to break down proteins into polypeptides …amino acids …converted to proteins for membranes and enzymes
which hormones are produced by the pancreas
insulin and glucagon
what is the name of the breakdown of non-carbohydrate sources to increase levels of glucose in the blood
gluconeogenesis
which experiment showed evidence of negative geotropism (and how to set it up)
- growing coleoptiles horizontally until a positive geotropic response is shown
- removing the tip and placing it on agar blocks, and dividing the agar block in two using a razor blade
- block A is above block B.
- Block B is shown to contain a greater concentration of auxin than block A.
how does auxin specifically affect cell wall plasticity (7 steps)
- The auxin molecule binds to the specific complementary receptor on the CSM 2. Stimulates proton pumps, causing H+ ions to be pumped out of the cell 3. pH of cell falls 4. over time, as levels of IAA inc., pH of cell dec., leading to more elongation of cells 5. Expansin enzymes break bonds between cellulose B-glucose monomers (B1,4 glycosidic bonds). H bonds between cellulose molecules broken. 6. Walls are less rigid 7. Water diffuses into cell, turgor pressure decreases
what is thigmonasty
nastic movement in response to touch eg. mimosa pudica
during seed germination and dormancy, what are the levels of GA and ABA
Germination: GA high, ABA low Dormancy: GA low, ABA high
why does etiolation occur
To improve the likelihood of the plant reaching a light source, in order to photosynthesise and create the sugars necessary for metabolic reactions.
what are control variables in the GA experiment
Same growth medium, same species of plant, concentration and volume of gibberellic acid applied, volume of water applied, light intensity, length of time allowed for growth and starting length of each plant
explain the commercial use of auxins in hormonal weed killers
Weeds (mainly dicots) interfere with crop plants (mainly monocots) by competing for light, space, minerals and water.
Synthetic dicot auxins are applied as weedkiller, growth rate increases and becomes unsustainable (broad-leaved dicots), while monocots unaffected, freed from competition.
what is the aleurone layer
cells containing protein stores and a seed before germination
what is an endocrine gland
one that produces hormones and releases them directly into the blood. They are ductless and produce a response
what is the pancreas
an exocrine gland made of acinar cells (acinus, acini) and islets of Langerhans
how does ABA cause stomatal closure
ABA stimulates the opening of potassium channels in cell membrane of the GUARD CELLS.
K+ diffuses out of the cell, decreasing water potential outside the cell.
Water diffuses out of the cell by osmosis down the water potential gradient.
Guard cells lose their turgor pressure and the stoma is closed.
explain why stomatal closure occurs
A plant will begin to wilt in high temperatures and/or low water availability.
ABA accumulates in the leaves to stimulate stomatal closure to rapidly prevent further water loss by transpiration from the leaves.
outline the process of seed germination, involving GA
- The seed embryo absorbs water.
- Once activated, the embryo produces GA, which diffuses into the aleurone layer.
- GA stimulates production of protease enzymes, which hydrolyse protein stores to amino acids.
- GA stimulates the synthesis of hydrolytic enzymes from amino acids.
- These hydrolytic enzymes hydrolyse food stores (amylase = starch to maltose, maltase = maltose to glucose) which are used as a substrate for cellular respiration to provide ATP
- ATP used for growth of radicle (root) and plumule (shoot) out of seed coat.
state what is phototropism
The movement of shoots towards light by growth.
Auxin hormones move to the shady/dark side of the coleoptile/apical meristem in shoots and travel down that side by active transport, promoting elongation of the cells on this side, causing it to bend. (plants show curvature towards unidirectional light)
what are nastic movements
plant movements that occur in response to environmental stimuli, but the direction of the response is not dependent on the direction of the stimulus.
what is an additional benefit of synthetic auxins are weedkillers
they are simple to produce, cheap, low toxicity to mammals, they are specific to the weeds that they kill
outline in detail the steps in abscission
-decreasing light intensity/light levels = decreased levels of auxins -when auxin levels decrease, leaves produce ethene -there is an ABSCISSION ZONE in the petiole (leaf stalk base) which is sensitive to ethene -there is an abscission layer. Enzymes are produced to digest the cell wall in this layer -there is also a protective layer. When the leaf falls, fatty material deposited here will protect the tree from entry of pathogens (protective scar). -vascular bundles to the leaf are sealed -weight of leaf + wind break the petiole along the abscission zone
how do auxins affect root and shoot growth
High concentration of auxin inhibits root growth, but promotes shoot growth Low concentration of auxin does the opposite.
explain the role of cytokinins when there is an apical meristem tissue present
cytokinins are attracted by the auxins in the apex, and therefore diffuse, along with mineral salts, from the roots to the apex. There they act synergistically with the auxins to promote cell elongation/growth. Food eg. sucrose is transported from the leaf to the apex. The dormant lateral bud will contain low levels of auxin and cytokinin.
describe how geotropism affects root growth
Gravity modifies the distribution of auxins so that they accumulate on the lower side of the root. In high concentrations they inhibit root growth, causing the root to bend downwards.
how is glucose produced when low blood sugar levels
- DIGESTION of carbohydrate 2. breakdown of glycogen GLYCOGENOLYSIS 3. conversion non-carbohydrate sources to glucose GLUCONEOGENESIS
explain the role of cytokinins when the apical meristem tissue is absent
cytokinins diffuse, along with mineral salts, from the roots to the lateral bud. Once lateral bud activated, produces more cytokinins to promote growth/cell elongation. Food eg. sucrose is transported from the leaf to the lateral bud, which becomes active and produces more cytokinins and auxins.
what will happen to a coleoptile with an untreated apical tip (when unidirectional light is present)
it will bend towards the light and elongate
what is synergism (plants)
hormones working together to give a combined response
outline the chemical defence against herbivores beginning ‘te…..’
Terpenoids are chemicals with an odour, often toxic to insects and fungi eg. citronella.
which two hormones does the adrenal medulla release
adrenaline and noradrenaline`
explain how geotropism is shown by plants
Shoots are negatively geotropic. Roots are positively geotropic.
what is a limitation of using a graph showing two distinct lines to give evidence of a difference when the dependent variable is changed
Differences may appear to be significant, but are not necessarily statistically different. The standard deviation of each result is needed to carry out a statistical test eg. unpaired t-test. The lowest concentration where the difference was significant would be the minimum concentration having an effect.
what causes apical dominance
auxins in the apex of the shoot of the plant stimulate upward growth of the stem. They inhibit the growth of lateral buds (side buds).
outline the chemical defence against herbivores beginning ‘a…..’
Alkaloids are a group of bitter-tasting compounds, many of which act as drugs eg. caffeine, cocaine, and can poison the animal digesting them. They can prevent germination of seeds of other species, reducing inter-specific competition.
where is gibberellin synthesised
in the embryo
what is the overall function of auxins
selective growth hormone
how will a plant with its apical bud absent appear
no lateral buds, but lateral branches
why is abscission important (3 reasons)
-to reduce the rate of transpiration when the rate of photosynthesis is low due to low temperature and low light intensity/levels -energy would be required to synthesise chlorophyll or antifreeze production, and low rate of photosynthesis “ -metabolic waste aggregated in vacuoles of leaf cells
what is the function of glucagon
An enzyme that increases blood sugar levels
TRIGLYCERIDES stored food is…. enzymes and intermediates in digestion are…. translocated products are…. role is growth and development is….
…lipids eg. oils …lipase to break down lipids into 2 FAs and glycerol …fatty acids and glycerol …respired to release energy and synthesis into membranes
state 6 tropisms
phototropism (light) +ve = shoots -ve = roots thermotropism (heat) hydrotropism (water) geotropism (gravity) chemotropism (chemical) thigmotropism (touch)
what do auxins affect in order to elongate cells
Auxins affect the plasticity of cell walls and therefore the cell wall stretches more easily.
what is a limitation of using a graph showing two distinct lines to give evidence of a difference when the dependent variable is changed
Differences may appear to be significant, but are not necessarily statistically different. The standard deviation of each result is needed to carry out a statistical test eg. unpaired t-test.
what are the 2 roles of gibberellins in plants
stem elongation (lengthening of the internode) and lateral bud growth seed germination
give three examples of plant hormone antagonism
-lateral bud growth AUXIN LEVELS VS. GIBBERELLINS LEVELS -abscission AUXIN LEVELS VS. ETHENE LEVELS -seeds GIBBERELLINS: germination VS. ABSCISIC ACID: dormancy
what is an exocrine gland
one that produces enzymes and releases them via a duct into the duodenum
where are auxins found in plants
in meristem cells in the apices of roots and shoots, or cambium.
what is glycogenolysis
the breakdown of glycogen to glucose to increase blood glucose levels
name the types of responses to herbivory in plants
CHEMICAL DEFENCES: tannins, alkaloids, terpenoids, pheromones THIGMONASTY: folding in response to touch
what is etiolation
When there are low light levels (low light intensity or absence of light), the plant uses its energy to promote the elongation of the apical stem, using auxin hormones. Therefore the plant develops chlorosis, because it does not use its energy to produce chlorophyll pigment. It also does not use its energy for other uses, and therefore will be thin and tall, with no branches/leaves/buds/internodes.
which experiment showed evidence of negative geotropism
-growing coleoptiles horizontally until a positive geotropic response is shown -removing the tip and placing it on agar blocks, and dividing the agar block in two using a razor blade to prevent any lateral movement of auxin (impermeable) -block A is above block B. -Block B is shown to contain a greater concentration of auxin than block A.
what are key limitations to keep in mind when discussing plants
They are not mobile and they have slow nervous transmission systems due to no central nervous system (tf not rapidly responding). They do communicate between cells and other plants, and respond to their environment, through an endocrine system of hormones, which stimulate responses.
explain the role of gibberellins
to elongate the stem, or the internodes between the branch points, by cell elongation. Different to auxins, they also stimulate cell division by stimulating a cell-cycle regulatory protein (triggering S phase).
how will a plant with its apical bud present appear
with dormant lateral buds (at the branches, at each internode)
outline what are VOCs
volatile organic compounds act like pheromones between the plants that produced them, and other organisms, in particular, insects. They diffuse through the air, and plants use them to defend themselves
what is the overall function of ethene
promotes ageing
describe how geotropism affects root growth
Gravity modifies the distribution of auxins so that they accumulate on the lower side of the root. In low concentrations they inhibit root growth, causing the root to bend downwards.
what are the 7 stages of decreasing blood glucose levels using insulin
- blood-glucose levels are too high
- beta cells detect high glucose concentration and secrete insulin directly into the bloodstream 3. insulin binds to specific insulin receptors on target body cells
- glucose transport channel proteins change shape; tertiary structure; and open
- increased uptake of glucose by tissues throughout body, in particular muscle cells, glucose concentration increases
- In the liver, glucose is respired, enzymes activated to increase fat synthesis from glucose, glucose stored as glycogen/glycogenesis
- increased cellular respiration + muscles store glucose as glycogen
what are the three types of hormone released from the adrenal cortex
glucocorticoids mineralocorticoids adrenal androgens
how does the response in mimosa pudica come about
K+ ion movement into cells, followed by water diffusing into cells, which changes the turgidity of the cells
what is the overall function of gibberellins
promotes growth
what experiment is carried out to show evidence of GA stimulation
Artificially adding GA to dwarf plants because they lack a gene involved in gibberellin production.
why are there high levels of ABA present during seed maturation
so that the seed does not germinate prematurely. It must first be mature before it becomes a plant/seedling/produces a coleoptile.
what is the function of insulin
to decrease blood sugar levels
what is gluconeogenesis
breakdown of non-carbohydrate sources to glucose to increase blood glucose levels
what are the 4 things released by the pancreas (give examples)
AMYLASES break down starch into simple sugars eg. pancreatic amylase PROTEASES break down proteins into amino acids eg. trypsin LIPASES break down lipids into fatty acids and glycerol eg. pancreatic juice PANCREATIC JUICE an alkaline fluid
what is glycogenesis
the synthesis of glycogen from glucose to decrease blood glucose levels
why are dwarf plants used in GA experiment
Dwarf peas do not naturally contain GAs. Tf it shows that the growth is due to the added GA. Gibberellic acid concentrations in normal pea plants cannot be controlled. With dwarf pea plants there is no variation because they do not produce GA.
outline the chemical defence against herbivores beginning ‘ta…..’
Tannins are bitter-tasting phenol compounds that are toxic to insects and off-putting for herbivores They bind to the digestive enzymes in the saliva and inactivate them (non-competitive inhibition)
what is a tropism
directional growth in response to environmental stimuli
how can one recognise islets of Langerhans
they are lighter stained, large, spherical clusters usually surrounded by acini
name the stimulus, receptor + effector
and how does homeostasis reverse the change
- STIMULUS: decrease/increase in blood-glucose conc. in blood (after eating/starving/exercise)*
- RECEPTOR: detected in Islets of Langerhans in pancreas*
- EFFECTOR: glucagon secreted by a cells or insulin secreted by ß cells*
When normal blood glucose conc. detected, negative feedback; glucagon/insulin secretion stops; hormone lost from blood in kidneys + excreted & affect other cells not to produce the converse hormone
how do auxins elongate cells
- Auxins binds to a specific receptor
- Stimulates ATPase to actively transport H+ protons into cell wall, decreasing pH
- K+ ion channels open, K+ moves into the cytoplasm, decreasing pH inside the cell
- Water moves by osmosis into the vacuole, expanding the cell/turgidity
- Expansin proteins activated by decrease in pH of cytoplasm, and hydrolyses intermolecular H bonds between cellulose microfibrils (cellulose does not break)
- Cell wall = less rigid, can elongate as water enters cell
