Mitochondria and Chloroplasts Flashcards
Endosymbiont theory
double membraned organelles present in eukaryotic cells (mitochondria and chloroplasts) are derived from formerly free-living prokaryotes that were engulfed by an ancestral cell for endosymbiosis
Stages of the endosymbiont theory
Anaerobic prokaryote -> infolding of plasma membrane -> endosymbiosis -> ancestral Eukaryote
Chloroplast and mitochondria DNA
- most DNA of mitochondria and chloroplasts has been transferred to nuclear genome
- DNA left in those organelles is highly reminiscent of bacterial DNA
- Because they have their own DNA, both chloroplasts and mitochondria have ribosomes
Products of cellular respiration
Carbohydrates + oxygen gas —> CO2 + H2O + ATP
Mitochondria membrane structure
have a double membrane consisting of an inner and outer membrane with aqueous compartments in between
Outer mitochondrial membrane (OMM)
- contains many enzymes with diverse functions
- porins: large channels which when open membrane is freely permeable (ex. to ATP)
Inner Mitochondrial membrane (IMM)
- Inner membrane has a high protein to lipid ratio (3:1)
- double layered folds known as cristae
- cristae increases surface area & has machinery for aerobic respiration and ATP formation
- rich in a phospholipid called cardiolipin (characteristic of bacterial membranes)
Aqueous compartments of the mitochondria
- intermembrane space
- matrix
- high protein gel-like consistency
- mitochondrial ribosomes and DNA (mtDNA)
- encodes polypeptides that are integrated into the IMM, ribosomes, tRNA
What is oxidative phosphorylation?
ATP synthesis from ADP
- takes place in the mitochondria
Main function of the citric acid cycle
Citric acid cycle uses Acetyl-CoA from glycolysis and passes sugars through the cycle to generate NADH and FADH2 which are needed in oxidative phosphorylation
Electron transport chain
- electrons are transported down through a series of complexes which pumps protons into the intermembrane space form the matrix
- generates an electrochemical gradient
- high energy electrons pass from coenzymes (NADH and FADH2 - from citric acid cycle) in the matrix to electron carriers in IMM
Complexes in the electron transport chain
Complex 1: turns NADH into NAD+
Complex 2: turns FADH2 into FAD
Complex 3: gets electrons passed from CoQ
Complex 4: passes O2 which combines with H+ to create H2O
- Energy transfer at each complex is used to pump protons from the matrix into the IM space
- Ultimately low energy electron is transferred to thermal electron acceptor and H2O is produced
Steps of oxidative phosphorylation
Step 1: electron transport chain
Step 2: controlled movement of protons back across IMM
Controlled movement of protons back across IMM
- happens via ATP synthase
- Potential energy in electrochemical gradient across IMM converted to ATP in matrix
- Now we are generating all of the energy our cells can utilize
Aerobic respiration
converts energy stored in food molecules to chemical energy stored in ATP. consumes oxygen and produces carbon dioxide as a waste product
Photosynthesis
Builds carbohydrates and releases oxygen from carbon dioxide and water - only happens in plants
components of the chloroplast
outer membrane, inner membrane, thylakoid membrane, thylakoid lumen, grana, stroma,
Photophosphorylation
The conversion of ADP to ATP using energy from the sun
- occurs on the chloroplast
- doesn’t replace cellular respiration
Membrane structure of Chloroplast
3 membranes
- inner membrane
- outer membrane
- thylakoid membrane
Goal of Light dependent reactions
- collect energy from the sun and break down water molecules to produce ATP and NADPH
- each water molecule breaks down into two hydrogen (H) atoms and one oxygen (O) atom.
Steps in light dependent reaction
- chlorophyll in light harvesting complex
- used light and water to generate e- O2 and H+
- electrons enter the electron transport chain
- ## H+ are pumped from stroma to thylakoid lumen to generate ATP
Thylakoids
Third membrane system in chloroplasts
- where the light dependent reactions happen
- thylakoids stacked on top of each other like pancakes = granum
Chloroplast genome
- Chloroplast have circular genome and ribosomes
- A good portion of the genome from the chloroplast has been moved to the nuclear genome
Light Independent reactions
- ATP (and NADPH) made in LDR are used to make CH2O
- also known as the calvin cycle
- ## occurs in the stroma
