L21 - Transport into mitochondria and peroxisomes Flashcards
What is the primary function of mitochondria?
Its main function is energy production - as mitochondria make large amounts of ATP.
STEP 1 = glycolysis - the breakdown of glycolysis into pyruvate - occurs in cytoplasm.
Then pyruvate enters the mitochondria & CO2 is removed from pyruvate. The rest of the molecule enters the Krebs cycle (TCA cycle).
Its primary function is also to produce H+ and generate a proton gradient across the inner mitochondria membrane. –> This drives ATPase to make ATP.
Has a key role in APOPTOSIS.
Describe the structure of mitochondria.
- mitochondria have a double membrane
- Inner membrane is highly folded into Cristae which gives a high SA for energy production. (contains the REDOX performing proteins of the electron transport chain) and transport proteins move molecules in and out of the matrix)
- Outer membrane encloses the organelle - perforated with porins (allow entry of molecules <5000 kDa) and contains enzymes involved in lipid synthesis.
- The (inner) matrix has enzymes responsible for energy production and enzymes of the krebs cycle.
- The INTERmembrane space (between inner and outer membrane) contains enzymes that use ATP to phosphorylate other nucleotides. H+ ions are pumped into this space to create a proton gradient.
Explain mitochondria genetics.
Mitochondria have their own genetics as they contain their own DNA, which is inherited from the mother.
They have a circular chromosome - approx 15-17kbps and encodes 37 genes.
What are the steps in the life cycle of mitochondria?
Fusion
Fisson
Mitophagy
(FFM- ACRONYM)
how do you get proteins into mitochondria?
Proteins are fully synthesised before translocated into the mitochondria using signal sequences.
What do TOM, SAM, TIM and OXA stand for?
TOM: Translocator of the Outer Membrane
SAM: Sorting and Assembly Machinery
TIM: Translocator of the Inner Membrane
OXA: Cytochrome OXidase acitivity
How do you get proteins into the mitochondrial matrix?
- N-terminal signal sequence – recognised by the TOM complex
- The protein translocates through TOM and TIM23
- Translocates through TIM23 into matrix
- Signal is cleaved off
What are Peroxisomes?
Peroxisomes only have 1 membrane and do not contain DNA or ribosomes.
They are in all eukaryotic cells and carry out oxidative reactions.
They contain a variety of oxidative enzymes - catalase and urate oxidase.
What is the function of peroxisomes?
They contain a variety of oxidative enzymes - catalase and urate oxidase.
Its function is to remove hydrogen atoms from organic compounds.
Where do new peroxisomes arise from?
New peroxisomes arise from pre-existing ones by organelle growth and fission.
Most peroxisomal membrane proteins are made in the cytosol and then insert into the membrane of pre-existing peroxisomes.
