Lecture 9: Cells 2 Flashcards
1
Q
Plastids
A
- describes mitochondria and chloroplasts
2
Q
Mitochondria
A
- found in both plant and animal cells
- Where Respiration takes place (energy comes from ATP)
- Have two membranes (outer and inner)
- The inner membrane is folded to generated cristae. This increases the SA to fill membranes with proteins that are required for generation
- The matrix has cytric acid cycle takes place (like cytoplasm of cell). You’ll also find DNA, RNA and ribosomes
3
Q
Chloroplast
A
- not found in animals (mostly plants)
- Responsible for photosynthesis
- Have outer membrane and an inner membrane
- Stacks of membranes sit inside and are called thylakoids
- Cytoplasm of the chloroplast is called the stroma (where carbon fixaition takes place- converts CO2 into sugar)
- Never find DNA and RNA inside the Golgi or ER (only outside). But, Chloroplass have RNA and RNA and ribosomes inside
- Gave rise to idea of endosymbiotic organelles
4
Q
Endosymbiotic Organelles
A
- Mitochondria and chloroplasts are descendants of bacteria. Bacteria was taken up by eukaryotic cell via phagocytosis
Evidence: - Double membrane (likely taken up by endocytosis)
- Own genome
- Own ribosomes more
similar to Eubacteria - Genes more similar to
eubacterial genes - Lipids come from ER through a unique system;
Unique machinery for protein import
5
Q
Cytoskeleton
A
- you need structure inside in order for cell to keep shape (since membrane is very flexible)
- This is a cytoskeleton
- Very crowded inside cell
- Almost entire space is taken up
6
Q
Cytoskeleton Filaments
A
- Actin filaments (smallest)
- Intermediate Filaments
- Microtubules (largest)
7
Q
Actin filaments
A
- exists in cells as monomers and filaments
- there are many proteins
that regulate polymerization
and depolymerization - When they polymerize, there is protein to protein interaction (non covalent)
- They have a polarity when they polymerize (neg end and pos end)
- form very long bundles
8
Q
Actin in Gut cells
A
- Cortically stabilizes the cell to make sure they look rectangular and can extend fingers (full of actin which increase SA so a lot of food can be taken up)
9
Q
Actin and Myosin
A
- interact to cause movement
- When myosin “head” attaches to actin and moves, the actin filament slides
- myosin can move in one direction
- can hydrolyze one ATP
10
Q
Actin and Myosin contraction
A
- Coiled-coil tail domains of myosin II can interact to form antiparallel bipolar complexes.
- These may contain many myosin molecules, as in thick filaments of skeletal muscle, or as few as 2 myosins.
- Myosin heads can move along actin filaments in only one direction.
- Antiparallel actin filaments can “contract”.
11
Q
Examples of movement caused by actin-myosin
interactions
A
• Cytokinesis in animals - Actin-myosin interactions pinch membrane in two •Cytoplasmic streaming in plants - Actin-myosin interactions move cytoplasm around cell - Cytoplasmic streaming (need to remove contents around cytosol which is mediated by actin myosin contraction)
12
Q
Microtubules
A
- As for actin, there are many
proteins that regulate growth
or shrinkage of MTs - alpha and beta tubulin bind together to form tubulin monomer
- Has polarity to it
- Then microtubules emirate from nucleus and go to cell periphery
13
Q
Microtubules; organization
A
- organize the cell
- they organize the transport of things from nucleus to periphery
- Basically highway of cell because they have two types of motors (actin has one) they move in opposite directions
- Gave kinesis and dyenin (walk in opposite directions)
14
Q
Kinesin
A
- has tail, stalk and then head
- “walks” along a microtubule track
15
Q
Dynein
A
- walks in opposite direction to kinesin
