BI110 Study Guide - Midterm Guide: Integral Membrane Protein, Dna-Binding Domain, Peripheral Membrane Protein

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17 Nov 2016
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Biology Midterm 2
Module 14
Cytoskeleton is a Complex Protein Network
Structural Support
Intracellular anchor
Involved in mitosis
Components (bacteria also have cytoskeleton but animal and plant cells have these components)
Microfilaments (Maintain cell shape; made of actin)
Intermediate filaments (More permanent structures, variable compositions (keratin, lamin))
Microtubules (Motility-cilia/flagella, cell division, made of tubulin)
Chloroplast move in Response to Light
Move along actin microfilaments
The way chloroplasts move towards or away from light is due to cytoskeleton
Photoreceptor (phototropin- response to light to move chloroplast)
In the cytoskeleton and its compared to eyespot
Intermediate Filaments
Alpha-helical structure that intertwines with each other (thicker and more permanent than actin
microfilaments)
Strong, thick cables
Variable composition (kerotin- abundant in our nails and hair)
Microtubules
Eukaryotic flagellum (allow single celled organisms to move through space)
Classic 9+2 structure that makes up flagella
9-pairs of microtubules that extend all the way down
2-pairs of the two microtubules that are central
Dynein arms connect microtubules (motor proteins use ATP to change conformation and allows them to
bend)
Connect adjacent long microtubules
Marks the spot where microtubules start (microtubules organization centre- also important in
mitosis)
Module 16: Extracellular Structures
Complexity of extracellular matrix in animal cells
Collagen- proteins that form long polymers, most abundant human protein which takes up 40% of
body components
Proteoglycan complex because collagen fibers are embedded within
Protein with lots of carbohydrates added to it
Fibronectin connects matrix and communicates between cells
Integrin connected to fibronectin and allows information to be shared
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Cell Junctions
Tight Junctions- watertight connections between adjacent cells (span entire length they are like a seal
(provide a seal of water tight connection which prevent water loss)
Desmosomes- they are live rivets and have an anchoring function, connect cells together; connect to
intermediate filaments (they are inside the cell- they hold two cells together like magnets if you have a
very dense tissue= increase in desmosomes)
Gap Junctions- channels between cells that allow movement of water and small molecules
Plasmodesmata are channels only in plant cells
Desmosomes hold cells together; they are like rivets (cells that are very close together have multiple
desmosomes)
Tight junctions prevent water loss, hold cells very tightly together
Cellulose is not found in the animal extracellular matrix
Plant cell wall
All interconnected
How does the cell wall get there? How do they get deposited? - cellulose synthase which is a plasma
membrane enzyme (individual glucose monomers get put through enzyme from inside of the cell, the
enzyme converts it to long polymers on the outside of the cell- got there through the endomembrane
system)
Middle lamella- made of pectin, sticky and holds the cells together
Plasmodesmata
Functionally analogous to gap junctions in animal cells, but different in how they achieve that
Membrane bound junctions, when cytoplasm gets caught during division and causes a channel
Allow signalling molecules to pass through
In gap junctions the channels are made of proteins
One cell type sends signal but another cells responds (channels allow this to happen)- Signalling molecules
is SHR which leads to response but adjacent cells will create another signalling molecule in response
o Signal must become trapped in the cell type so that it stops moving through plasmodesmata
Module 17: Cell Membranes
The importance of selectively permeable membrane
Cells and organelles need barrier to seperate internal and external contents
Barrier must have the following qualities:
o Don’t want most things to get across, want things to stay on either side
o Impermeable to most molecules and ions
o Ability to exchange some molecules/ions between compartments
o Insoluble in water (if dissolved then there wouldn’t be a barrier)
o Permeable to water (allow water to get across)
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The functions of membranes
Cell wall- provides structure, protect cell, and gives it shape
(unique feature of plant cells)
Primary-where most structure provided, most sturdy,
thickest part (made of cellulose which is a polysaccharide of
glucose which is highly branched)
Different types of cellulose for different components
Doesn’t just allow sodium ions to cross the membrane (this
is because sodium ions are positively charged which are
hydrophilic ions)
The membrane has a hydrophobic interior therefore
ions cannot get across without assistance
Small uncharged things like different gases can freely
get across by diffusion
o For respiration
Organization and localization of functions
Transport processes (membranes are selectively permeable- transport proteins that allow ions to pass
through membrane)
Organic molecules can get across such as glucose with proteins embedded in membrane
Signal detection (the cell will respond to it through receptors in the membrane)
Cell-to-cell interactions (membrane proteins)
What is a cell membrane?
A permeability barrier that consists of:
Phospholipids, glycolipids
Sterols (except in bacteria) VERY IMPORTANT
Cholesterol (animals)
Ergosterols (fungi)
Phytosterols (plants
Membrane proteins
Integral proteins
Peripheral membrane proteins
Phospholipids
Can have different head types (different membranes have different percentages of all the different
phospholipids)
Primary molecules that make up biological membranes
One saturated fatty acid tail (straight)
One unsaturated fatty acid tail ( one double bond- monounsaturated, but can have poly-unsaturated
which is multiple kinks)
Different types of combos because of different fatty acids and different heads
Can have different tail lengths
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