Energy for biological processes chp 17 Flashcards
what are some examples of metabolic activities
- active transport
- anabolic reactions (polymerisation of biological monomers)
- movement brought about by cilia, flagella and contractile filaments in muscles cells
define respiration
process where organic molecules are broken down into smaller inorganic molecules in order to produce energy
write out the balanced symbol equation for photosynthesis and respiration
bond formation and bond breaking, which one takes in energy which one releases energy
- energy is used to break bonds
- energy is released when bonds are formed
what determines wether a reaction is overall exo or endo thermic
depends on the total number and strength of bonds that are broken or formed during the reaction
why are large organic molecules used in respiration
- less energy is needed to break bonds than form bonds in products
- excess energy is used to synthesis ATP
what is chemiosmosis
- diffusion of protons from a region of high conc to a region of low conc through a partially permeable membrane
^releases energy used to make ATP
what does chemiosmosis depend on and how is this requirement met
- on creation of a proton conc gradient
- protons actively pumped using energy coming from electron transport chains
in which ways are excited electrons generated
- electrons present in the pigment molecules are excited by absorbing light from the sun
- high energy electrons released from NADH
what is an electron transport chain
- made up of a series of electron carriers
- ^each with progressively lower energy levels
How is energy generated from the electron carrier chain and how is it used
- high energy electrons move from one carrier in the chain to another, energy is released
- used to pump protons across a membrane, creating a conc gradient and therefore a proton gradient.
What is the only way the protons can move back through the membrane after the proton gradient has been generated during the process of ATP synthesis
dont just say chemiosmosis
- diffusion through hydrophilic membrane channels linked to the enzyme ATP synthase
- flow of protons through these provides energy to synthesis ATP
what is meant by autotrophic and heterotrophic
- autotrophic - they make their own nutrients via photosynthesis
- heterotrophic - obtain complex organic molecules by eating others
what is stacked to form grana (plural granum)
thylakoids are stacked to form grana
what links grana
joined by membranous channels called lamellae
where can chlorophyll be found within chloroplast
embedded within thylakoids membrane
what occurs within the storm of a chloroplast
chemical reactions occur within it
Why do plants appear green
- the pigment chlorophyll absorbs specific wavelengths of light
- ^mostly blue and red light , while it reflect green giving plants their green colour
where are most of the chloroplast and chlorophyll located in a plant
located in the upper mesophyll layer
what are examples of some other light harvesting pigments
- chlorophyll b, xanthopylls and carotenoids
- responsible for different shades of leaves
what is the antennae complex
it is the light harvesting system within plants formed from light sensitive pigments such as chlorophyll a and b and
what are the light harvesting system and reaction centre collectively known as
a photosystem
what light sensitive pigment gives plants there yellow and orange colours for example during the autum
- carotenoids are responsible for the yellow/orange colour
- orange carotene and yellow xanthophyll and 2 examples
what are the 2 stages of photosynthesis
- light-dependent stage
- light-independent stage
what occurs during the light dependent stage
- energy from the sunlight is absorbed and used to form ATP.
- Hydrogen from water is used 5to reduce coenzyme NADP to reduced NADP
what occurs during the light-independent stage
- hydrogen from reduced NADP and carbon dioxide is used to build organic molecules, such as glucose.
- ATP supplies the required energy
what reaction is involved within the light dependent stage of photosynthesis
- non-cyclic photophosphorylation
How many photosystems are involved in non-cyclic photophosphorylation
- 2
- photosystem 1 & 2
what happens to the electrons that have been excited at photosystem 2
- they are released from reaction centre in PS 2 and are passed to an electron transport chain (ATP produced by chemiosmosis)
- electrons lost are replaced from water molecules broken down by the sun
during the process of photosynthesis what photosystem is first in the process
photosystem 2
what happens to the electrons in photosystem 1 during photosynthesis
- excited electrons are released from reaction centre at PS 1, passed to another electron chain (ATP produced by chemiosmosis)
- electrons lost from reaction centre are replaced by electrons from the electrons released from PS 2
what happens to the electrons after they have left the electron transport chain during the process of photosynthesis
they are accepted along with a H+ ion, by the coenzyme NADP, forming reduced NADP
what is the function of reduced NADP
provides the hydrogen/reducing power of organic molecules, such as glucose in the light-independent stage
does the light dependent or independent stage come first
the light dependent stage comes first
what is photolysis
- water molecules are split into hydrogen ions, electrons and oxygen molecules using energy from the sun
- this is why water is a raw material of photosynthesis
What happens to the electrons generated during photolysis
they replace the electrons lost from the reaction centre of PS 2
what happens to the protons generated by photolysis during the process of photosynthesis
- they are released into the lumen of the thylakoids, increasing the concentration across the membrane
- as they move back across the membrane they drive the synthesis of ATP
- Once H+ ions are back in the stroma they combine with NADP and an electron to form reduced NADP
why is it important that during the light dependent stage H+ ions are used to form reduced NADP
it removes hydrogen ions from the stroma so it helps to maintain proton gradient across thylakoid membrane
There is a light dependent and independent stages during photosynthesis, which one has cyclic and non-cyclic photophosphorylation
- the light dependent reaction involves non-cyclic photophosphorylation
- the light independent reaction involves cyclic photophosphorylation
How can cyclic photophosphorylation occur
- electrons leaving the electron transport chain after PS 1 can be returned to PS 1, instead of being used to form reduced NADP,
^this leads to cyclic photophosphorylation
where does the light-independent stage of photosynthesis occur within the plant
- occurs in the stroma
what reactants are required for the light-independent stage
- CO2
- products from light dependent stage ATP and reduced NADP
what is the Calvin cycle
a series of reactions that produce organic molecules such as glucose in the light-independent stage of photosynthesis
what physically happens to carbon dioxide during the Calvin cycle
- enters spongy mesophyll layer of leaves by diffusion through stomata.
- diffuses into cells then further into stroma of chloroplasts where it combines with RuBP
How can the carbon within carbon dioxide be described as fixed during the calvin cycle
- it is incorporated into an organic molecule
what is the function of RuBisCO in the Calvin cycle
- it catalyses the reaction of carbon of CO2 being incorporated into RuBP
- ^producing an unstable intermediate
why is so much RuBisCO the most abundant enzyme in the world
it is very inefficient as it is competitively inhibited by oxygen so a lot it needed to carry out photosynthesis
what happens to the unstable intermediate formed from RuBisCO during the Calvin cycle
it immediately breaks down forming 2 GP molecules
During the calvin cycle what does a single GP molecule breakdown into and how is it done
each GP molecule is converted into TP (triose phosphate), using a hydrogen atom from reduced NADP and energy supplied from ATP
what is the majority of triose phosphate molecules converted into and why
it is recycled to regenerate RuBP so that the Calvin cycle can continue
what 3 steps can summarise the Calvin cycle
- fixation - carbon dioxide is incorporated into an organic molecule in the first step
- reduction - GP is reduced to TP by addition of hydrogen from reduced NADP using energy supplied by ATP
- regeneration - RuBP is regenerated from the recycled TP
how many full turns of the Calvin cycle are required to produce 1 glucose molecule
6 CO2 molecules have to enter the Calvin cycle, resulting in 6 full turns of the cycle
What would be the products of 6 full turns of the Calvin cycle
- 12 TP molecules, 2 of which will be removed to make a glucose molecule
^the other 10 will be recycled to regenerate 6 RuBP molecules
what are the factors that affect the rate of photosynthesis
- light intensity
- CO2 concentration
- Temperature
How does light intensity affect the rate of photosynthesis
- As light intensity increases, ATP and reduced NADP are produced at a higher rate
How does CO2 concentration affect the rate of photosynthesis
- CO2 Is needed as a source of carbon, so cetris paribus, increasing the CO2 conc increases the rate of carbon fixation in the Calvin cycle and therefore the rate of TP production
how could temperature increase the rate of photosynthesis
- at temp rises the rate of enzyme activity increases until they denature
- the rate of enzyme controlled reactions such as carbon fixation would increase
How could temperature decrease the rate of photosynthesis
- the rate of photorespiration increases above 25°C meaning photosynthetic rates may not be seen at higher temps even if enzymes aren’t denatured
- stomata on leaves will close to avoid water loss during dry spells which can limit CO2 diffusion into the leaf reducing the rate of the light-independent reaction, eventually halting photosynthesis
What is the effect of reduced light intensity on the Calvin cycle
- it will reduce the rate of the light-dependent stage.
^this will reduce the quantity of ATP and reduced NADP produced, both of these are needed in the light-independent stage - ^the conc of GP will increase and the conc of TP will decrease (as there is less TP there will be less regeneration of RuBP
vice versa
How would temperature effect the Calvin cycle
the Calvin cycle involves many different enzymes so temperature can increase or decrease enzyme activity
How could CO2 concentration effect the calvin cycle
- CO2 is an essential substrate for the Calvin cycle
- low cons will lead to reduced concs of GP (as there will be less carbon fixation) and TP
- Conc of RuBP will increase as it is still being formed from TP but not being used to fix CO2
