Plant Physiology And Biochemsitry Flashcards
(40 cards)
How does gibberellin lead to plant germination
1) seed is dormant
2) seed absorbs water
3) embryo produces Gibberellin
4) gibberellin stimulates aleurone layer
5) to produce amylase
6) amylase hydrolyses starch
7) to endosperm
8) to maltose
9) embryo uses glucose for respiration
10) the energy is then used for growth
11) gibberellin affects transcription of mRNA, coding for amylase
Describe the role of ABA in closing the stoma
1) ABA (abriscisic acid) is a stress hormone
2) plant secretes ABA in dry conditions
3) ABA binds to receptors
4) on plasma membrane of guard cells
5) H+ is therefore not pumped out of cell
6) high H+ concentration inside cell
7) k+ diffuses out of cell
8) water potential of cell increases
9) water moves out of cell by osmosis
10) volume of guard cell decreases
11) guard cells become flaccid
12) response is very fast
Effect of gibberellin on cell elongation
1) gibberellin is a plant growth regulator
2) this stimulates cell devision and cell elongation
3) cell elongation is due to changes in plasticity of cell wall
4) plant grows tall
5) if you apply gibberellin to drawf plants they will grow taller
6) there are both active and inactive forms of gibberellin
7) drawf plants have the inactive form of gibberellin
8) dominant allele (Le) causes synthesis of enzyme
9) the enzyme catalysed the active form of gibberellin
10) the recessive allele (le) results in the inactive form of gibberellin formed
How does gibberellin activate genes
It causes the destruction of DELLA protein repressors, which normally inhibit the transcription Factors that promote the transcription of the alpha amylase gene
How does auxin control cell elongation
1) Auxin binds to auxin receptor proteins in CSM
2) ATPase proton pump, pumps H+ from the cytoplasm into the cell wall
3) ph decreases
4) expansins (proteins) in cell wall are activated and break bonds between cellulose microfibrils and surrounding substances
5) cellulose microfibrils can move past each other temporarily
6) cell can expand while cell wall remains fairly strong
7) auxin also stimulates opening of potassium ion channels
8) k+ diffuses into cytoplasm and lowers water potential
9) water diffuses into cell by osmosis through aquaporins
10) cell wall stretches and elongates
How do Venus fly traps close
1) sensory hairs are touched twice in quick succession
2) h+ ions are pumped out of midrib cells into cell wall
3) high h+ concentration lowers ph
4) calcium pectate (the glue) in the cell walls dissolve
5) cell walls of mid rib cells loosen
6) high h+ concentration outside midrib cells create an electrochemical gradient
7) ca2+ diffuse into the midrib cells which lowers water potential causing water to enter
8) midrib cells expand
9) lobes flips from convex to concave
10) trap closes
When is ATP and reduced NADP used in photosynthesis
It is used in the light independent stage (calvin cycle) of photosynthesis to produce complex organic compounds
Where is the sight of the light dependent stage of photosynthesis
Thylakoid membrane
Where is the sight of the light independent stage of photosynthesis
Stroma
What pigments are in the chlorophylls group
These are the primary pigments and include chlorophyll a which absorbs yellow-green light. As well as chlorophyll b which absorbs blue-green light
What pigments are in the carotenoids group
These are the accesory pigments and includes beta carotene which absorbs orange light. As well as xanthphyll which absorbs yellow light.
What is the role of photosynthetic pigment
They absorb certain wavelengths of light, light energy is needed in photolysis.
Absorption spectrum
A graph of the absorbance of different wavelengths of light by pigment. It shows that little green light is absorbed, as this light is then reflected back the leaf appears green
Action spectrum
A graph of the rate of photosynthesis at different wavelengths of light. This shows the effectiveness of the different wavelengths of light, which is related to their absorption and their energy content. The shorter the wavelength the greater the energy it contains.
Retention factor equation
Distance travelled by pigment / distance travelled by solvent
Chromatography
You crush the leafs in a solvent. A mixture of pigments extracted from leafs is placed on the paper at the pencil line, it is dabbed on by capillary tube and given time to dry before more leaf extract is added. You then put the paper in a beaker with some solvent which is just below the pencil line. The solvent rises up the paper carrying each pigment at a different speed. This separates the pigment as they move at different speed.
Light independent reaction
Carbon dioxide from the atmosphere diffuses into the leaf through stomata and diffuses into the palisade mesophyll cells and then into the stroma of the chloroplast. In the stroma, carbon dioxide combines with the five carbon compound (ribulose biphosphate) RuBP using the enzyme RUBISCO. The combination of carbon dioxide and RuBP produces a 6-carbon compound which is unstable and breaks down into two molecules of the 3-carbon compound (glycerate 3-phosphate) GP. ATP and reduced NADP from the light dependent reaction are used to reduce the activated GP to (triose phosphate) TP. Some TP molecules are converted to useful organic substances such as glucose. Most TP molecules are used to regenerate RuBP using ATP produced from the light dependent reaction
Cyclic photo-phosphorylation
Involves only photosystem 1. Light is absorbed by photosystem 1 and is passed to the primary pigment. An electron in the chlorophyll molecule is excited to a higher energy level and is emitted from the chlorophyll molecule. It is captured by an electron acceptor and passed back to the chlorophyll molecule via a chain of electron carriers. Enough energy is released to synthesise ATP from ADP and inorganic phosphate by chemiosmosis. ATP is used in the light independent reaction
Non-cyclic photo-phosphorylation
Involves both photosystems. Light is absorbed by both photosystems and excited electrons are emitted from the primary pigment of both reaction centres. Theses electrons are absorbed by electron acceptors and pass along chains of electron carriers. The primary pigment of photosystem 1 absorbs electrons from photosystem 2. Its primary pigment receives replacement electrons from photolysis. ATP is synthesised as the electrons loose energy whilst passing along carrier chains
Photolysis of water
In photosystem 2, an enzyme cause H2O -> 2H+ + 2e- + 1/2O2. Oxygen is a waste product which is used by the plant in aerobic respiration, or released through the stomata. The protons are used to reduce NADP with electron from inorganic phosphate
The hill reaction
Liquidise the leaves in ice cold water and filter the resulting suspension to remove unwanted debris. Chill small tubes of buffered chloroplast suspension. Add DCPIP solution to the tubes. Place the tubes in different light intensities. Assess the blue colour at 1 minute intervals. Record the rate of loss of blue colour using a colourimeter
overview of light dependent reaction
Light energy excites electrons in the chlorophyll molecule in the thylakoid membrane, causing them to pass to an electron acceptor at the start of the electron transport . Electrons pass down the chain from one electron carrier to the next in a series of redox reactions. This process generates ATP from ADP and inorganic phosphate in a process called photophosphorylation. Light splits water into protons (H+ ions), electrons and oxygen (waste). The electrons are used to replace the electrons lost from the chlorophyll in step 1. This process is called photolysis of water. The protons are pumped across the membrane using the ATP in a process called chemiosmosis. This creates a chemical potential gradient. Reduced NADP is generated as the electrons in the electron transport chain are transferred to NADP along with a proton. Protons pass back through the membrane through an ATP synthase enzyme which makes ATP. Approximately 4 protons make one ATP molecule. Both ATP and reduced NADP are used in the light-independent stage of photosynthesis.
How are C4 plants adapted to their role
RuBP in bundle sheaf cells, away from oxygen to avoid photorespiration. Carbon dioxide combines with PEP, it is catalysed by PEP carboxylase in mesophyll cells. This forms oxaloacetate which is converted to malate. Malatate passes to bundle sheath cells, it then releases high concentrations of carbon dioxide. RuBP then reacts with the carbon dioxide. The enzymes also have a high optimum temperature
What happens to the calvin cycle intermediates
Some TP condenses to form hexose phosphate which is used to produce starch for storage, sucrose for translocation, or cellulose for making cell walls. Others are converted to glycerol and fatty acids to produce lipids for cellular membranes. Or the production of amino acids for protein synthesis
