Peroxisomes, Mitochondria, Chloroplasts

Peroxisomes

These are single-membrane organelles containing enzymes involved in many metabolic reactions.

free

Peroxisomes are synthesized on _________ ribosomes & imported as completed polypeptides.

redox

Peroxisomes have a lot of ___________enzymes (places for redox reactions).

hydrogen peroxide

Many substrates are broken down by oxidative reactions in
peroxisomes, which leads to production of ____________________________.

Catalase

____________ converts hydrogen peroxide to water or
uses it to oxidize another organic compound.

lipids

Peroxisomes are also involved in the synthesis of ____________.

cholesterol

In animal cells, ______________ and dolichol are synthesized in
peroxisomes and in the ER.

1. Vesicle budding from the ER (peroxisomes have new content)

2. Growth and division of existing peroxisomes (more rapid)

These are the 2 mechanisms by which Peroxisomes are formed:

Plasmalogens

These are phospholipids with one hydrocarbon chain joined to glycerol by an ether bond instead of a ester bond; important in some tissues.

mPTS (membrane peroxisome targeting signals)

These are regions of peroxisomal membrane proteins (PMPs) that direct and insert the proteins into the peroxisomal membrane.

PEX5 and PEX7; docking

These are primarily responsible for importing proteins into the peroxisome matrix by recognizing specific targeting signals (PTS1 and PTS2 respectively), and the PEX/cargo complex binds to a ________________ complex.

PEX3 and PEX16

These are crucial for the formation and proper assembly of the peroxisomal membrane itself.

C-terminus

PTS1 is located at the ____________________.

N-terminus

PTS2 is located at the _________________.

cristae; matrix

The inner-membrane space of the mitochondria has folds called ______________, which extend into the interior space called the ____________..

Matrix

In the mitochondria, this contains the genetic system & enzymes for oxidative metabolism.

fusion

Mitochondrial ___________ allows for the exchange of genetic material.

Fission

This is important in the distribution of mitochondria between daughter cells at cell division, & in facilitating transport of mitochondria to areas of high energy demand.

genome

The mitochondria has its own ________________(chloroplasts too).

NADH; FADH; FADH2

The Citric Acid Cycle reduces NAD to _______ and FAD to __________ and _________.

1. In the matrix, the citric acid cycle reduces NAD to NADH and FAD to FADH and FADH2

2. High energy electrons from NADH and FADH2 are transferred to molecular oxygen

3. This moves protons from the matrix to intermembrane space

4. This proton transfer creates a proton gradient between two sides of the inner membrane

5. This gradient stores energy created by oxidative phosphorylation

6. Selective permeability maintains the gradient

7. Gradient energy is used to synthesize ATP in the reaction that couples reverse movement of high energy protons from intermembrane space back to matrix, converting ADP to ATP.

These are the steps of oxidative phosphorylation:

inner

The _________ membrane is the primary site of ATP generation (know why).

mitochondrial matrix

This proton gradient is mainly created by depletion of protons in the __________________________.

complex

Because of the double-membrane structure of mitochondria, import of proteins is ______________.

Tom

Presequences bind to receptors on the
mitochondria that are part of a protein complex called the ________ complex.

Tim

This is the complex in the inner mitochondrial membrane.

import signals

Proteins with multiple transmembrane domains have internal _______________________ instead of presequences.

Matrix Processing Peptidase (MPP)

Presequences are cleaved by ___________________________________________.

OXPHOS inner membrane proteins

These are encoded by the mitochondrial genome, synthesized on ribosomes in the matrix, & targeted to the Oxa1 translocase in the inner membrane; they exit Oxa1 laterally into the inner membrane.

Tim22 Complex

Tim9-Tim10 chaperones bring proteins from the Tom Complex to the _____________.

Mim1

Proteins with a single transmembrane domain are inserted via the outer membrane protein ___________.

energy

Mitochondria are often positioned near locations of high ________________ use, like synapses.

Cardiolipin

This is a mitochondrial lipid that improves efficiency of oxidative phosphorylation by restricting proton flow across the membrane.

cytosol

Most lipids in the mitochondria are imported from the __________________.

phospholipid transfer

Lipid transfer between the ER and mitochondria is mediated by ____________________________ proteins.

proton pumping

The energy to move small molecules like ATP, ADP, and Pi is provided by the electrochemical gradient generated by ___________________________ across the inner mitochondrial membrane during oxidative phosphorylation.

Adenine Nucleotide Translocator

This is an integral membrane protein that mediates the transport of ATP & ADP; it is an antiporter.

CO2

Chloroplasts convert _________ into carbohydrates.

1. Both generate metabolic energy

2. Both evolved by endosymbiosis

3. Both contain their own genetic system

4. Both replicate by division

What are the ways in which Chloroplasts and Mitochondria are similar?

envelope

Chloroplasts are bounded by a double membrane called the chloroplast _________________.

1. Intermembrane Space

2. Stroma

3. Thylakoid Lumen

Chloroplasts have 3 internal compartments:

thylakoids

The thylakoid membrane (internal membrane system) forms a network of flattened discs called _______________.

Intermembrane Space

In the chloroplast, this is the space between the membranes of the envelope.

Stroma

In the chloroplast, this is the space inside the envelope but outside the thylakoid membrane.

porins

The outer membrane of the chloroplast contains _______________ and is permeable to small molecules.

ions

The inner membrane of the chloroplast is impermeable to ___________ and metabolites, which move through specific transporters.

thylakoid membrane; stroma

In chloroplasts, electron transport and ATP generation take place in the _____________________________; protons are pumped across this membrane from the ______________ to the thylakoid lumen.

In both, ATP generation takes place here from pumping protons across the membrane.

Why is the thylakoid membrane of the chloroplast equivalent to the inner membrane of mitochondria?

tRNAs

Chloroplast encoded _________ are sufficient to translate all the mRNA codons using the universal genetic code.

larger; complex

Chloroplast genome is present in multiple copies, but are ____________ and more ____________ than those of mitochondria.

free; completed

Similarly to mitochondria, most chloroplast proteins are synthesized on ________ ribosomes and imported into chloroplasts as _______________ polypeptides.

chlorophyll

Chloroplasts contain __________________ (pigment).

carotenoids

Chromoplasts contain _______________ (yellows & reds in fruits/flowers).

nonpigmented

Leucoplasts are ___________________ (store energy sources).

starch

Amyloplasts (Leucoplasts) store _______________.

lipids

Elaioplasts (Leucocytes) store ______________.

structure

Plastids have the same genome as chloroplasts, but differ in _______________ and function.

thylakoid membranes

Plastids have a double-membrane envelope but lack ___________________ and other components of the photosynthetic apparatus.

pigments

Plastids are classified based on the ______________they contain.