Lec 15: Energy Generation in Mitochondria and Chloroplasts Flashcards
Which of these represents the fate of a portion of the O2 produced by photosynthesis in chloroplasts?
It is consumed by oxidative phosphorylation in mitochondria
What is true of the evolution of electron transport systems?
They are evolutionarily ancient, and likely provided energy for the earliest cells on earth
The first living cells on earth are suspected to have generated ATP by what process?
Fermentation: organic molecules are broken down to generate energy without the involvement of oxygen. (Which didn’t enter the atmosphere in large amounts until about a billion years after photosynthetic cells evolved)
Chemiosmotic coupling
How mitochondria, chloroplasts, and prokaryotes generate energy. It uses a membrane-based mechanism which involved using an electrochemical proton gradient to drive the synthesis of ATP.
Where is the electron transport chain?
On the inner mitochondrial membrane
Normally only small non-polar molecules can go through the lipid bilayer. In this case, the person would need to make more NADH (consuming more food) to generate the same amount of ATP).
Products of cell respiration in mitochondria
How NADH turns into NAD+
Overview of the citric acid cycle/big picture, where it happens
What are the different activated carriers used for?
NADH is mostly used for making ATP, the others are used more for catalyzing reactions
Oxidative Phosphorylation
A chemiosmotic process that converts oxidation energy (loss of electrons from a molecule) into ATP
In detail, what are the steps the hydrogen pumps?
Know:
- it’s on the inner mitochondrial membrane
- NADH dehydrogenase is the first
- ubiquinone carries the electron to cytochrome C reductase, so cytochrome C gets the electron
- the cytochrome C passes it to cytochrome c oxidase complex, which passes it to oxygen, to make water.
What does it mean to be an electrochemical gradient?
Pi: is the phosphate
First case: It would make ATP (the rhodopsin pumps H+ out, creating a gradient, which the ATP synthase needs to make ATP)
Second case: nothing happens, no gradient is created.
How does ATP synthase physically work?
Hydrogen ions flow down a channel and cause ATP synthase to revolve, creating a mechanical motor. This causes the ATP synthase to make ATP. It could run in reverse if the ATP concentration is high, and the proton gradient is low.
What steps generate the most ATP?
NADH from the citric acid cycle.
How is the energy provided to pump H out of the cell, against the gradient?
Overview of chloroplasts/photosynthesis
Noncyclic photophosphorylation
Where do the energy, electrons, and reactants come from at each step?
What are the products of each reaction?
High energy electrons come from excitation from sunlight as opposed to from NADH
Details of carbon fixation
3 CO2 means three carbons in
glyceraldehyde -phosphate means 3 carbons out
What do mitochondria and chloroplasts have in common?
They both may have evolved from bacteria that were engulfed.
They both contain their own DNA, and can only synthesize a few proteins. They rely on the rest being transported in.
Comparing the electron transport chain in chloroplasts and mitochondria
In eukaryotes, which organelle performs oxidative phosphorylation?
mitochondria. oxidative phosphorylation means that it oxidizes something (NADH) and phosphorylates something else (ATP)
How many ATP can be made from glucose under aerobic conditions? Anareobic?
Aerobic: 30
Anaerobic: 2
Which activated carrier contains a high-energy bond whose hydrolysis releases a large amount of free energy?
ATP
In mitochondria, what is the final electron acceptor in the electron-transport chain?
Oxygen (O2)
What is true of NADH?
It has a weak affinity for electrons, and a negative redox potential
Most of the energy for the synthesis of ATP comes from which molecules?
NADH produced by the citric acid cycle
As the human population grows, it becomes increasingly important to maximize crop yields. Therefore, scientists are searching for more efficient ways for plants to convert CO2 into biomass. One approach is to genetically modify plant enzymes involved in photosynthesis to increase their efficiency. Which plant enzyme, responsible for carbon fixation, is a major focus of research?
Rubisco
What represents the fate of a portion of the O2 produced by photosynthesis in chloroplasts?
It is consumed by oxidative phosphorylation in mitochondria
What is true of the evolution of the electron-transport systems?
They are evolutionarily ancient, and likely provided energy for the earliest cells on Earth
The first living cells on Earth are suspected to have generated ATP by what process?
fermentation
In animal cells, how is most ATP produced?
mitochondria produce most of the ATP using energy derived from the oxidation of sugars and fatty acids
Besides driving ATP synthesis, what does the proton gradient do?
it drives the active transport of selected metabolites into and out of the mitochondrial matrix
antenna complex
in chloroplasts and photosynthetic bacteria, the part of the membrane-bound system that captures energy from sunlight; contains an array of proteins that bind hundreds of chlorophyll molecules and other photosensitive pigments
Carbon fixation
Process by which green plants and other photosynthetic organisms incorporate carbon atoms from atmospheric carbon dioxide into sugars. This is the second stage of photosynthesis
cell respiration
process by which cells harvest the energy stored in food molecules, usually accompanied by the uptake of O2 and the release of CO2
chlorophyll
light-absorbing green pigment that plays a central part in photosynthesis
cytochrome
a family of membrane-bound, colored, heme containing proteins that transfer electrons during cell respiration and photosynthesis
cytochrome c oxidase
protein complex that serves as the final electron carrier in the respiratory chain; removes electrons from cytochrome c and passes them to O2 to produce H2O
photosystem
large multiprotein complex containing chlorophyll that captures light energy and converts it into chemical-bond energy; consists of a set of antenna complexes and a reaction center
quinone
small lipid-soluble mobile electron carrier that functions in the respiratory and photosynthetic electron-transport chains
reaction center
in photosythetic membranes, a protein complex that contains a special pair of chlorophyll molecules. It performs the photochemical reactions that convert the energy of photons (light) into high-energy electrons for transport down the photosynthetic electron transport chain.
redox pair
two molecules that can be interconverted by the gain or loss of an electron; for example NADH and NAD+
redox potential
a measure of the tendency of a given redox pair to donate or accept electrons
redox reaction
a reaction in which electrons are transferred from one chemical species to another. An oxidation-reduction reaction
respiratory enzyme complex
set of proteins in the inner mitochondrial membrane that facilitates the transfer of high-energy electrons from NADH to oxygen while pumping protons into the intermembrane space
stroma
in a chloroplast, the large interior space that contains the enzymes needed to incorporate CO2 into sugars during the carbon-fixation stage of photosynthesis; equivalent to the matrix of a mitochondrion
thylakoid
in a chloroplast, the flattened disc-like sac whose membranes contain the proteins and pigments that convert light energy into chemical bond energy during photosynthesis
photosystem II
note: comes first
It’s reaction center passes electrons to a mobile electron carrier called plastoquinone. It then transfers the high-energy electron to a proton pump called cytochrome b6-f complex. This is the only place where there is active proton pumping in the chloroplast electron-transport chain.
This proton gradient is used to make ATP.
photosystem I
note: comes second
captures it’s high energy electron and gives it to ferredoxin, which brings the electrons to an enzyme that makes NADPH from NADP+
where does the oxygen that is produced by photosynthesis come from?
electron energy flow in photosynthesis
stages of photosynthesis
stage 1: electron transport chain in the thylakoid membrane harnesses the energy of electron transport to pump protons into the thylakoid space. The high energy electrons are not donated to O2 at the end, they are donated to NADPH, which is then used for biosynthetic pathways.
stage 2: ATP and NADH produced by the photosynthetic electron-transfer reactions of stage 1 drive the manufacture of sugars from CO2. This happens in the chloroplast stroma. Results in glyceraldehyde 3-phosphate
Where do the electrons in photosynthesis come from?
In photosystem II, when the mobile electron carrier plastoquinone removes an electron from a reaction center, it leaves behind a positively charged chlorophyll pair. Same thing when photosystem I gives an electron to ferredoxin.
In photosystem II, this electron comes from splitting water into O2, H+, and an electron.
In photosystem I, it comes from the end of photosystem II.
