Lecture 9: Mitochondria, Chloroplasts, Cytoskeleton & Cell Adhesion Flashcards
What are plastids? Examples?
Small organelles such as mitochondria or chloroplast
Are the chloroplast and mitochondria part of the end-membrane system?
No
How many membranes does the mitochondria have?
The mitochondria has two membranes, an inner membrane and an outer membrane
What are Christae?
Christae are formed when the inner membrane of the mitochondria is further invaginated
- Christae contains the enzymes for respiration
What is the matrix and where is it?
The matrix is the space inside the mitochondria.
-It is full of enzymes that catalyze the citric acid cycle
- It also contains DNA that is transcribed into RNA
-Does contain some ribosomes and RNA and circular DNA
Where are mitochondria found?
In all eukaryotes(plants, animals, fungi, protists)
What are mitochondria essential?
They provide our daily ATP needs
Where are chloroplasts found?
Found in plants and other eukaryotes but never in animals
How many membranes do chloroplasts have?
Two, an inner membrane and an outer membrane
What are thylakoids?
A stack of membranes separated from the inner membrane inside chloroplasts
- Help absorb sunlight for photosynthesis
-All photosynthetic enzymes are found within the thylakoids
What is the storma?
The space that fills the rest of the interior of the chloroplast similar to the matrix of mitochondria)
-Stroma contains enzymes that mediate carbon fixation
What is carbon fixation?
Conversion of atmospheric carbon dioxide into sugars
What is found inside chloroplasts?
-RNA
-DNA
-Ribosomes
-Circular DNA
Plastids are endosymbiotic, what does that mean?
They live inside other organisms and both mutually benefit
What is phagocytosis?
An event where one cell eats another one
What went through phagocytosis?
Both the mitochondria and chloroplasts went through phagocytosis which is how they ended up inside of cells
Prove of the endosymbiosis theory due to membranes of chloroplasts and mitochondria ?
-Both chloroplasts and mitochondria have double membranes
-Their outer membranes also have slightly different compositions than their inner membranes(out membrane is similar to a cell membrane, inner membrane is similar to a bacterial membrane)
How does the importation of lipids and proteins contribute to the endosymbiosis theory?
Lipids and proteins are imported completely different into chloroplasts and mitochondria compared to the endomembrane system(have a unique machinery for protein importation)(completely different from the ER, proteins are not made in the ER but instead in the cytosol and then enter into the mitochondria with their own machinery)(some are even made inside the mitochondria and chloroplasts)
What is the most important piece of evidence for the endosymbiosis theory?
Mitochondria and chloroplasts have their own genome, a circular genome which is typically found in bacteria
Additional pieces of evidence that are in favour of the endosymbiosis theory?
-They have ribosomes that look more bacterial
-Size of the mitochondria and chloroplast are similar to that of bacteria
Are the Golgi and ER from the same ancestor as the chloroplasts and mitochondria?
NO
What is a cytoskeleton?
-Any type of internal structure that gives cells their typical shape
-Normally huge protein complexes made up of many individual proteins that provide stability and shape and even allow cells to move around
What are the three components that make up the cytoskeleton?
- Actin Filaments
- Intermediate Filaments
- Microtubules
What are actin filaments?
-Made up of actin monomers that polymerize into actin filament
-Actin monomer refers to an entire protein
-Long chains
From largest to smallest name the three components of the cytoskeleton?
-Microtubules
-Intermediate Filaments
-Actin Filaments
Is the polymerization of actin filaments covalent bonds?
No, instead it is protein-protein interactions
What causes actin filaments to have polarity?
-Actin filaments have a positive and negative end because they are not perfectly round
Do proteins interact with actin filaments, if yes how?
- Proteins do interact with actin filaments
- Proteins can help them depolymerize, grow or can cut the actin filaments
-Some actin binding proteins will bind actin filaments together into big bundles of actin filaments
How do actin filaments work in gut cells?
- The actin is cortical in the gut cells(right below the membrane)
- The actin makes villi in gut cells(they stick out and increase the surface area of gut cells to help increase food that the body intakes)
What is myosin?
-A motor protein that can bind to and walk along the actin filaments
-It can only walk in one direction
How does myosin work?
- The head region of the myosin binds to the actin filament
- ATP is then hydrolyzed producing energy
- The myosin uses that energy to walk along the actin filament
What phenomenon does myosin give rise to?
The actin-myosin contraction
How does the actin-myosin contraction occur?
- Two strands of actin filament run anti parallel.
- Myosin on the same actin filament bind to each other with their rotted domain and their heads stick upwards or downwards.
- When ATP hydrolysis occurs now the myosin walk toward the positive end of the actin filaments.
- Contraction occurs because the myosin are walking in opposite directions
What is cytokinesis?
-Occurs after cell division, the cell is still connected through the cytosol and must be pinched off into completely different cells.
-This is an example of the actin-myosin contraction
What is cytoplasmic streaming in plants?
-An example of movement caused by actin-myosin interactions
How many ATP does one step pf the myosin take?
1 ATP per step
How are actin-myosin contractions useful in plants?
They help plants to generate internal movement of fluids to help speed up diffusion
What are intermediate filaments?
-Rope like structures found in cells that provide mechanical strength to cells(coiled coils of keratin) or nucleus(lamins)
-Provide mechanical strength
What do intermediate filaments stabalize?
-The nucleus
What don’t intermediate filaments contain?
-Motor proteins
- No polarity
- Do not polymerize/depolymerize
What are microtubules?
- Hollow cylinders similar to actin filaments
-Formed of monomers called alpha and beta tubulin(individual proteins)
How do microtubules form?
-The alpha and beta tubulin first form a dimer and then these dimers polymerize together(form noncovalent protein-protein interactions)
What do proteins do to microtubules?
-Cut them
-Grow them
-Shrink them
-Bind them together
How are microtubules organized?
Always point from the centre of the periphery
Organization of actin filaments and microtubules in terms of the centre and pheriphery?
-Microtubules start out at the organizing centre and go in all directions from this centre to the peripheries
-Actin filaments are at the peripheries and give structure to the cells
Why are microtubules known as highways of the cell?
-Entire organelles or mRNAs can be transported along microtubules in either direction
How does transportation along microtubules work?
- Kinesin(first motor) similar to myosin(has a head that through ATP hydrolysis can walk along the microtubule and there is a tail that binds to the “cargo”(thing being transported)
- Dyenin(second motor), walks opposite to kinesis
Do the motors of the microtubules walk in the same direction?
No
What are the names of microtubules motors vs actin filaments?
Microtubules: Dyenin, Kinesin
Actin Filament: Myosin
Where does transportation through microtubules occur most importantly?
Occurs in all cells but is most important in nerve cells
What are cilia and flagella made up of ?
Microtubules
Where are cilia found and what is there role?
-Cilia are found in single celled organisms
-Their role is to. help organisms move around by beating back and forth
Where are flagella found and what is there role?
-Found in sperm
-There role is to help sperm reach the egg
Where in humans do cilia occur?
-Cilia occur in the fallopian tubes(propel the egg to the right place)
-They are also found in the lungs to help get rid of dirt
What structure is produced by the microtubules in cilia and flagella?
-9+2 structure
- Nine microtubule doublets and two central microtubules
How do cilia and flagella beat(create movement)?
- Dyenin connects to the microtubule doublets with its head domain and with its tail it binds to another microtubule
- When ATP is hydrolyzed the microtubules slide past each other because they only walk in one direction.
- The sliding is not really possible because there are proteins called elastic proteins that also connect all the microtubule doublets
- The force caused by the want to slide must go somewhere and thus is what causes the microtubule doublets to bend
What are the two types of adhesions?
- Cell-Cell
- Cell-Matrix
What can cell-cell adhesion lead to?
- Phagocytosis
- DNA exchange
- Sperm-egg fusion
Is cell-cell adhesion what led to multicellular organisms?
Yes
What is tight junction?
-A type of cell-cell adhesion
-Membrane proteins from two different cells bind together extremely tightly
What is the function of a tight-junction?
-To prevent unwanted stuff from entering the gut
-To separate membrane domains into the apical side(face toward external environment) and the basolateral side(adjacent to basement membrane(membrane that surrounds cells)).
What is the gap-junction?
-A type of cell-cell adhesion
-Forms channels between two cells
Function of gap junction?
-Allows the free exchange of ions
-Important in the heart
What is cell-matrix adhesion?
Cells adhering to anything but another cell
What is the extracellular matrix?
All the proteins and goods that are secreted by cells and that fills up the intercellular space or the surrounding. Sometimes it helps to give structure to our body.
How are cells attached to the extracellular matrix?
They are attached by proteins called integrins
What are integrins?
-Big molecules that bind to the actin cytoskeleton found within a cell
- On the outside they bind to some extracellular matrix proteins
Focal adhesions?
Hundreds of integrins together in one spot
Where is the majority of cells ATP produced?
Mitochondria
What do chloroplast do?
Convert light energy into chemical energy
What molecules does carbon fixation yield?
-Sugars
-Amino acids
-Fatty acids
What are the most important structural proteins?
Actin filaments and microtubules
What is a monomer of actin filaments?
One single actin protein
Are microtubules polar?
Yes
What is the role of focal adhesions?
They attach our muscles to bone via tendons
They also attach our skin to basal lamina
