lecture 16 Flashcards
What are autotrophs?
“self feeders” that sustain themselves without eating other organisms
What are heterotrophs?
obtain organic material form other organisms
What is photosynthesis commonly called
reverse respiration
What does photosynthesis do in terms of electrons?
reverses the direction of electron flow compared to respiration- electrons leave water and go to carbon
What is the function of chloroplasts in photosynthesis?
chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules and releasing oxygen as a by-product
What kind of reactions does photosynthesis consist of?
light and dark reactions
Where do light reactions occur?
in the thylakoids
What happens during light reactions?
-split H2O
-release O2
-Reduce the electron acceptor NADP+ to NADPH
-generate ATP from ADP by photo-phosphorylation
Where is the Calvin cycle?
in the stroma
What does the Calvin cycle do?
forms sugar from CO2 using ATP and NADPH
What is the site of photosynthesis in plants?
chloroplasts
Where are chloroplasts located in plants?
In the mesophyll of leaves, the interior tissue of the leaves
What are stomata?
microscopic pores on leaves where CO2 enters and O2 exits
What is the structure of chloroplasts?
an envelope of two membranes surrounding a dense fluid called the stroma
What is stroma?
dense fluid in chloroplasts
What are thylakoids?
connected sacs in the chloroplasts that compose a third membrane system
What are grana?
the third membrane system in chloroplasts
What is chlorophyll?
the pigment that gives leaves their green color
Where is chlorophyll located (specifically)?
thylakoid membranes
What are photons?
discrete particles that make up light
What are pigments?
substances that absorb visible light
Different pigments absorb different wavelengths
What happens to wavelengths that are not absorbed?
they are reflected or transmitted
What happens when a pigment absorbs light?
It goes from a ground state to an excited state, which is unstable
What happens when excited electrons fall back to the ground state?
excess energy is released as heat
What is fluorescence?
an afterglow produced by pigments that emit light in isolation
What does the light-harvesting complex consist of?
pigmented molecules bound to proteins and transfer the energy of photons to the chlorophyll ‘a’ molecules in the reaction-center complex
What is the reaction center complex?
an association of proteins holding a special pair of chlorophyll ‘a’ molecules and a primary electron acceptor
Why are chlorophyll ‘a’ molecules so special?
because they can transfer an excited electron to a different molecule
What does a primary electron acceptor do?
accepts excited electrons and is reduced as a result
What is the Z scheme?
describes the oxidation/reduction changes during the light reactions of photosynthesis.
What are the main products of light reactions?
ATP and NADPH
What is used to fix carbon in the calvin cycle?
ATP and NADPH
What are the similarities in mitochondrial and chloroplast structures?
-multiple membranes and compartments
-both respiration and photosynthesis feature an electron transport chain
-both ETC’s establish a proton gradient that is coupled to ATP synthesis
-generate ATP by chemiosmosis, but use different sources of energy
What is the source of energy in mitochondria
H+ in intermembrane space drives ATP synthesis as H+ diffuse back into the mitochondrial matrix
What is the source of energy in chloroplasts?
H+ pumped into the thylakoid space (lumen) drives ATP synthesis as H+ diffuse back into the stroma
Where are ATP and NADPH produced
on the side facing the stroma where the calvin cycle takes place
Light reactions generate ___ and ____ the potential energy of electrons by moving them from ___ to ____.
Light reactions generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH.
