Mol Lecture #36 Flashcards
1
Q
Cytoskeleton
Overview
A
- Cytoskeletal networks: 3 types
- Stable structures, but they’re also dynamic (cell is constantly restructuring them)
2
Q
Microtubules
Functions + Structure
A
- Provide tracks for vesicular transport (microtubule tracks to mive through organelles)
- Flagella and cilia (specialized functions to help move the cell or structures within the cell)
- Cell cycle- mitosis: kinetichore/non-kinetichore microtubules
- Hollow tubule made up of subunits: Called tubulin
–> Tubulin has ‘+’ and ‘-’ ends (and so do microtubules) with different growth products - Microtubules often radiate from centrioles located near the nucleus
- Many microtubules, but the density is higher towards the nucleus.
3
Q
Motor Proteins
Microtubules
A
- Dyneins and Kinesins
- Stably attach to some cargo and move along the cytoskeleton
4
Q
Intermediate Filaments
A
- Function in structural support and providing tensile strength
- Structure can occur as monomeric filaments, in parallel bundles, and in interconnected networks
→ Key element: highly elastic- can stretch several times their length.
→ think about the epithelial layers of the skin - ability to stretch - Do not have a localization density- uniformly distributed
5
Q
Microfilaments (actin filaments)
Function
A
- They can anker membranes to other structures
- Provide tracks for vesicular transport
- Heavily involved in cell movement, maintaining cell shape
- Role in mitosis and cytokinesis
6
Q
Microfilaments
Structure
A
- Typically in 2 polymers of actin subunits (not covalently attached- just a lot of monomers, protein-protein interactions)
- Also have ‘+’ and ‘minus’ ends that grow and shrink at different rates (top to bottom like before)
7
Q
Non-covalent properties of Cytoskeleton Filaments
A
- exist between monomers in cytoskeletal filaments, or between ligands and their receptors
- The 3D shape of the involved proteins and the 3D shape at their interaction site matters/ chemical characterisitcs at the interation site matter.
- Proteins can be held together by non-covalent interactions at the binding site, including via hydrogen bonds, hydrophobic-hydrophobic interactions, polar-polar interactions, and charge-charge interactions.
8
Q
Motor Proteins
example
A
- Myosins- stably attach to some cargo, and move along the length of the filament
9
Q
Animal Cell interactions
A
- Cell adhesion molecules hold cells together (transient or semi-permanent interactions)
Also allow cells to bind to things in the environment → extracellular matrix
10
Q
Cell Junctions
A
- Mediate more stable interactions between cells
- Anchoring junctions: stitching cells together tightly (have plaque (internal structure) and connected directly to the cytoskeleton). Two types based on which cytoskeletal element they bind to.
- Tight junction: forms between two cells so that nothing passes between them (epithelial cell layers, low permeability across cell layer - think digestive tract control)
- Gap junction: large protein channels (multi-protein channels)- think nuclear pore complex
11
Q
Specifics (These are more permanent adhesions)
Anchoring
A
-Anchoring Junction: adjoins cells using a structure known as a plaque that is connected to the cytoskeleton.
- Demosomes- intermediate filament connections
- Adherens junctions- microfilament connections
12
Q
Tight junctions:
A
creates tight seal between cells to prevent passage of molecules etc. between them.
13
Q
Gap Junctions:
A
- multiprotein channels that allow rapid passage of molecules (etc) between cells. (ex. Neurons and muscle cells)
14
Q
Extracellular Matrix
A
- Proteins are in the extracellular matrix and they’re often glycoproteins
- Integrin: transmembrane protein that can attach to microfilaments, and bind to proteins in the extracellular matrix
15
Q
Cell Signaling
Overview
A
- How cells communicate with other cells and they’re environment- important for single celled organisms, but critical for mutlicellular organisms
- Responses depend on cell type
16
Q
Distance Types
A
- Contact dependent- membrane bound type
- Paracrine- cell secretes something (signal- soluble) maybe 3-5 cells away
- Endocrine- soluble molecule that is secreted and can go long distances (hormones): Into the bloodstream
- Synaptic- type of signaling distance thats only foud in excitatory cells- neurons, muscle- (very small distances between them), difference that the first one because something is being passed across
17
Q
Steps (for paracrine and endocrine focus)
A
- Reception: signaling ligand (soluble entity released that is received by the receptor)
–> Non-covalent interactions mediate the ligand binding, the same features that help proteins fold - Signa transduction: translate and amplify the signal, involves a cascade or proteins translating the signal
- Response
18
Q
Reception
A
- Ligand (soluble): hydrophobic)(might be able to cross over the membrane) or hydrophilic (cannot get across the membrane, so we have receptors
–> Often proteins, but often not - Cells have many different receptor types on their surface. Cells can therefore recognize many ligand types. (possibly integrating many signals at once as well)
19
Q
Transduction
A
- Transforming a signal into one that can cause a cellular response. Often involves many proteins acting in sequence .
20
Q
Protein types:
Transduction
A
- Kinases
- GTPases
- Small molecule intermediates
- Ions that flux (transported across a membrane)
21
Q
Response
Macro v.s. Micro
A
- Macroresponse ( larger level)
- Move
- Cell cycle
- Die (programmed cell death)
- Differentiate
- Take on the characteristics of a different cell
- Create special products
- Microresponse (molecular level)
- Changes in the amount or activity of cellular components (ex. Cyclins, changing gene transcription, enzyme (allosteric regulation to change the things that are already there, or making more/less of something))
22
Q
Regulation
A
- Cell signaling pathways have to be turned off and can be modified by the cellular environment and other pathways.
