Energy for biological processes Flashcards
what are some metabolic activities? (activities which require energy)
-active transport
-anabolic reactions (building up)
-movement
ATP is produced in photosynthesis and respiration by what process?
chemiosmosis
what is chemiosmosis?
diffusion of protons from a region of high concentration to a region of low concentration through a partially permeable membrane. The movement of protons releases energy that is used in the attachment of an inorganic phosphate forming ATP.
what does chemiosmosis depend on?
the creation of a proton concentration gradient, energy comes form excited electrons
how are electrons raised to higher energy levels (excited)?
-electrons in pigments (chlorophyll) are excited by absorbing light
-high energy electrons are released when chemical bonds are broken in respiratory substrate molecules (glucose)
what is an electron transport chain?
made up of a series of electron carriers, each progressively lower energy levels. As electrons move between the carriers, energy is released. This is used to pump protons across the membrane to create a concentration difference and therefore proton gradient.
how is the proton gradient maintained?
due to the impermeability of the membrane
how can protons move back through the membrane?
through hydrophilic membrane channels linked to ATP synthase (catalyses formation of ATP). The flow of protons provides energy used to synthesis ATP.
what is photosynthesis?
the process by which energy in the form of light form the sun is used to build complex organic molecules.
what are autotrophic organisms?
organisms that can photosynthesis
what are heterotrophic organisms?
organisms that obtain complex organic molecules by eating other organisms.
symbol equation for photosynthesis?
6CO2+ 6H2O -> C6H12O6 + 6O2
Describe the structure found inside chloroplasts?
flattened sacs called thylakoids are stacked to form grana. The grana are joined by lamellae. Fluid enclosed is storm where many chemical reaction forming complex molecules take place.
what is chlorophyll?
primary pigment molecule. Chlorophyll absorbs mainly red and blue light and reflects green light.
why are there different shades of colours in leaves?
due to the different combination of pigments
what other pigments are embedded in the chloroplasts?
chlorophyll b, xanthophylls and carotenoids are embedded in the thylakoid membrane. These and other proteins for a light harvesting system (antennae complex)
wha is the role of the antennae complex?
absorb or hovers light energy of different wavelengths and transfer this energy quickly and efficiently to the reaction centre. Chlorophyll is located in the reaction centre
the light harvesting system and reaction centre are collectively known as a?
photosystem
Is chlorophyll produced when there is no sunlight?
No therefore it needs to be continuously synthesised however if sunlight is too intense, chlorophyll is destroyed
what colours do carotenoids and xanthophyll pigments form?
cartenoids form orange and xanthophyll forms yellow. They are usually masked by green chlorophyll.
What pigment is anthocyanin?
red/purple pigment formed from reaction between sugars and protein in cell sap. It is produced when sugar concentration is high. The colour is pH dependent.
high light intensity promotes the production of what?
anthocyanin
how does anthocyanin act as a sunscreen?
by absorbing blue-green and ultraviolet light, thereby inhibiting the destruction of chlorophyll.
how can different pigments be extracted from a plant extract?
through chromatography
what are the two stages of photosynthesis?
-light dependent stage: energy from sunlight absorbed to form ATP. Hydrogen from water is used to reduce coenzyme NADP+ to NADP
-light independent stage: hydrogen reduced from NADP and carbon dioxide is used to build organic molecules.
what wavelengths are absorbed from photosystem I and photosystem II?
PSI absorbs light at a higher wavelength (700nm) than PSII (680nm)
Describe the non-cyclic phosphorylation?
-The excited electrons are released from the reaction centre of PSII and are passed to an electron transport chain. -ATP is produced by chemiosmosis. -Electrons are replaced by photolysis.
-excited electrons are released from PSI into another transport chain and ATP is again produced by chemiosomosis
-electrons leaving the electron transport chain are accepted along with a hydrogen ion, by the coenzyme NADP, forming reduced NADP
What is photolysis?
water molecules split into hydrogen ions, electrons and oxygen molecules using energy from the sun. The electrons released from the reaction centre of PSII are replaced.
What is the symbol equation for photolysis?
H2O -> 2H+ +2e- + 1/2 O2
Where do hydrogen ions formed from photolysis go?
protons released to lumen of thylakoids, increasing proton concentration. As they move back through the membrane down concentration and electrochemical gradient, they drive the formation of more ATP. Once H+ ions are returned to the stroma, they combine with NADP and an electron from PSI to form reduced NADP. This is used in the light independent reactions of photosynthesis. This removes H+ ions from the stroma to maintain the proton gradient across the thylakoid membrane.
what is cyclic photophosphorlyation?
electrons leaving the electron transport chain can be returned to PSI, instead of being used to form reduced NADP. PSI can still lead to the production of ATP without any electrons being supplied from PSII.
What is the light independent stage of photosynthesis?
takes place in the stroma and uses carbon dioxide as a raw material. Products of light dependent stage- ATP and reduced NADP are used. Organic molecules like glucose are formed in a series of reactions called the Calvin cycle
Explain the Calvin cycle?
-In the storm, carbon dioxide combines with ribulose biphosphate (RuBP). The carbon in carbon dioxide is fixed
-Ribulose biphosphate carboxylase (RuBisCO) enzyme catalyses reaction forming unstable six carbon intermediate.
-unstable six carbon compound breaks down to form two three carbon glycerate 3-phosphate (GP) molecules.
-each GP molecule is converted to another three carbon molecule, triose phosphate (TP) using a hydrogen atom from reduced NADP and energy supplied by ATP (both from light dependent stage)
Why is ribulose biphosphate carboxylase (RuBisCo) considered an inefficient enzyme?
it is competitively inhibited by oxygen so a lot of it is needed to carry out photosynthesis successfully
What triose phosphate used for?
-regenerate RuBP
-used as a starting point for the synthesis of many complex biological molecules
What three steps can the Calvin cycles be summarised in?
-Fixation: carbon dioxides fixed
-Reduction: GP is reduced to TP
-Regeneration: RuBP is regenerated from the recycled TP
Describe the regeneration of RuBP?
for one glucose molecule to be produced six carbon dioxide molecules have to enter the Calvin cycle so there needs to be six turns o the cycle resulting in 12 TP molecules, two of which will be removed to make a glucose molecule. 10 TP molecules are recycled to regenerate six RuBP molecules.
What happens when carbon dioxide levels become low? (e.g stomata close due to increased humidity)
oxygen is a competitive inhibitor for enzyme RuBisCo, leading to the production of phosphoglycolate and reducing production of GP.
How is phosphoglycolate removed?
-it is a toxic two carbon molecule
-it is converted by the plant into other organic molecules and energy from ATP is needed for the conversion
what factors affect photosynthesis?
-light intensity
-carbon dioxide concentration
-temperature
how does light intensity affect photosynthesis?
light is needed as an energy source. The higher the light intensity, the more ATP and reduced NADP produced at a higher rate
How does carbon dioxide concentration affect photosynthesis?
increasing carbon dioxide concentration, increases rate of carbon fixation in the Calvin cycle and therefore the rate of TP production
How does temperature affect the rate of photosynthesis?
affects the rate of enzyme controlled reactions (carbon fixation). As temp increases, the rate of enzyme activity increases until proteins denature
what is photorespiration?
enzyme RuBisCo oxygenates RuBP
why might higher photosynthetic rates not be seen at higher temperatures even if the enzymes are not actually denatured?
the rate of photorespiration increases at 25 degrees
why is water never considered a limiting factor?
because for water potential to become low enough to limit photosynthesis, plants will have already closed its stomata and cease photosynthesis
what is a data logger?
an electronic device that records data over time using sensors. Physical properties like light intensity, temperature, pressure, pH and humidity can be recorded in graphical form or spread sheet.
What are the advantages o using a data logger?
-high accuracy
-many readings can be taken in a short time
Describe the effect of reducing light intensity on the Calvin cycle?
-it will reduce the rate of the light dependent stage therefore reducing the quantity of ATP and reduced NADP produced
-As ATP and reduced NADP are needed to convert GP into TP, the concentration of GP will increase and TP conc will decrease.
-There will be less TP to regenerate RuBP and RuBP conc will decrease.
How will lower temperatures impact the Calvin cycle?
-enzyme and substrate molecules will have less kinetic energy
-fewer successful collisions and a reduced rate of reaction
-lower concentrations of GP, TP and RuBP
How will lower carbon dioxide levels impact the Calvin cycle?
-reduced concentrations of GP and TP (less carbon dioxide fixed)
-Conc of RuBP will increase as it is still being formed from TP but not used to fix carbon dioxide
