Transcript Week 2 Pre-Lecture Slidesx

Class 5 Learning Goals
Monday, Janary 9th,
2017
Lipids and Membranes
• After this class, you should be able to:
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Classify a molecular as one of three main classes of lipids
Describe the structure and formation of a lipid bilayer
Predict the comparative solubilities of any two molecules
Predict the solubilities of a molecule through two different bilayers
Lipid Structures
Peer Instruction
1) What are the defining features of each class of lipids?
2) Which are amphipathic, and why?
1) Why do lipid bilayers form?
Peer Instruction
2) In what ways can individual phospholipids
move within a bilayer?
Peer Instruction
Explain this data.
Peer Instruction
What compounds cross lipid bilayers most readily?
Rank these molecules from most to least likely to cross a plasma membrane:
Glucose
CO2
H2O
O2
K+
Peer Instruction
Are membranes with straight lipid tails more or less
permeable than membranes with kinked tails?
Are membranes with long tails more or less permeable
than membranes with short tails?
Are warmer membranes more or less permeable than
colder membranes?
Membranes: Saturation of C-C bonds in lipid tails
Key Concepts
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What kind of lipid is estradiol? Safflower oil?
Will a lipid bilayer form faster in pure water or muddy water? Why?
Which will go through a lipid bilayer faster:
– Benzene or methane? Potassium ions or methane? Glucose or ATP?
Through which membrane will sodium ions move more quickly:
– A membrane with long, straight tails or short, kinked tails?
Peer Instruction
Are membranes with straight lipid tails more or less
permeable than membranes with kinked tails?
Are membranes with long tails more or less permeable
than membranes with short tails?
Are warmer membranes more or less permeable than
colder membranes?
Tuesday January 10th, 2017
Class 6 Learning Goals
Transmembrane Transport and Organelles
• After this class, you should be able to:
– Predict the polarity of any part of an integral membrane protein
– For each of three types of membrane transport,
– Describe the logic for the cell of that transport type
– Describe the mechanism
– Be able to identify the type of transport from a scenario
– Name and predict the enzymatic components inside any of the
organelles in the given table
– Identify membrane movements necessary for
– organelle function
– the sorting/production/delivery of non-cytoplasmic proteins
– Trace the path of transport and development for a protein or lipid
moving through the endomembrane system.
Peer Instruction
Vesicles can form from membranes:
Vesicles can be absorbed into membranes:
This can be spontaneous, but is usually guided by proteins.
Peer Instruction
Explain these three mechanisms for cellular digestion.
(One sentence each, maximum)
Lysosome
Endosome
Lysosome
Vesicle
from Golgi
apparatus
Damaged
organelle
Organelles: The Lysosome
Lysosomes are singlemembrane-bound
centers for storage
and/or waste
processing.
Materials are delivered
to the lysosomes by three
processes:
-phagocytosis,
-autophagy, and
-receptor-mediated endocytosis.
(Peroxisomes are very similar, with a
Peroxide-based microenvironment)
Microenvironment: Acidic
Material being
digested within
lysosomes
Organelle
Cellular Role
Nucleus
(Covered in great depth in 355)
Lysosome
Peroxisome
Vacuole
Mitochondria
(Covered in depth in Week 5)
Chloroplast
(Covered in great depth in 220)
Rough ER
Smooth ER
Golgi Apparatus
Ribosomes
(Covered in depth next week)
Cytoskeleton
Plasma membrane
(Covered in depth yesterday)
Specialized
components
Microenvironment
The EndoMembrane System:
The protein & lipid factory
• Comprised of
– the rough ER,
– the smooth ER, and
– the Golgi apparatus,
• The EMS is the primary system
for protein and lipid synthesis.
This system allows
production, processing
and transport of specific
and diverse molecules.
Nucleus
EMS Organelles: The Rough ER
A Protein Synthesis and Processing Complex
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The rough ER is contiguous
with the nuclear membrane
New proteins are directly
inserted into the ER
Microenvironment: noncytoplasmic molecular
Lumen of
conditions for protein folding
rough ER
After processing, proteins are
transported to other destinations Ribosomes
on outside
by controlled vesicle budding
Free ribosomes
in cytoplasm
EMS Organelles: Smooth ER
A Lipid-Handling Center and Storage Site
• The smooth ER is the major
processing zone for lipids
• Smooth ER lacks ribosomes,
naturally
• ER hosts non-cytoplasmic
molecular conditions and
specialized enzymes
• After processing, lipids are
transported to other
destinations by controlled
vesicle budding
Smooth endoplasmic reticulum
Lumen of
smooth ER
EMS Organelles: The Golgi Apparatus
A Site of Protein Processing
The cis face is oriented
towards the rough ER
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A site for carbohydrate
modification of proteins
Packaging and transport to
cellular locations with
vesicles
Formed by a series of
stacked flat membranous
sacs called cisternae.
Receives products from
the rough ER and sends
finished products to the
cell surface in vesicles.
The trans face is oriented
away from the rough ER
Golgi apparatus
cis face
Vesicle
Lumen
Cisternae
Vesicles
trans face
Wednesday, January 11th,
2017
Class 7 Learning Goals
The Endomembrane System and Cell Movement
• After this class, you should be able to:
– Trace the path of transport and development for a protein or lipid
moving through the endomembrane system.
– Explain the dynamic nature of cytoskeletal elements
– Analyze and identify errors in a description of cellular movement
Organelles: The Cytoskeleton
• The cytoskeleton is a complex
network of fibers that helps
maintain cell shape by providing
structural support.
• The cytoskeleton is dynamic; it
changes to alter the cell’s shape,
to transport materials in the cell, or
to move the cell itself.
• The three types of cytoskeletal
elements are
– actin filaments,
– intermediate filaments, and
– microtubules.
Raven & Singer, 7th Edition
Organelles:
Cytoskeletal building
Peer Instruction
• The smallest cytoskeletal elements are
actin filaments, also known as microfilaments.
• Actin filaments form by polymerization of individual actin molecules.
the ‘-’ end
the ‘+’ end
‘actin polymerase’
‘actin depolymerase’
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How does this filament move to the right?
You have:
Peer Instruction
a cytoskeletal filament
a motor protein
a vesicle
a plasma membrane around the cell
Draw the answers:
How does your cell move a vesicle towards an organelle?
How does your cell move part of the plasma membrane?
1. ‘Crawling’
time 1
time 2
nucleus
Peer Instruction
time 3
nucleus
2. ‘Chasing’
nucleus
nucleus
target
3. ‘Contraction’
nucleus
nucleus
Key Concepts
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Why do you expect amino acid side chains on the outside of an integral
membrane protein (but within the bilayer) to be hydrophobic?
Explain the matches between three possible transport situations…
– facilitated diffusion, active transport, and passive diffusion
…and three cellular situations
– a need for extreme rapid transport, intake of a common large molecule,
letting a rare waste molecule out of the cell
What specialized enzymes would you expect in a mitochondrion? In the Rough
ER? What microenvironment is unique to the nucleus? To the peroxisome?
Imagine:
– 1) a lipid destined to become part of the plasma membrane, and
– 2) a protein that will be released outside of the cell.
• Describe the differences in the pathways taken by each molecule.
Where or when does each pathway utilize the joining of lipid membranes?
What would happen to a crawling cell that instantly lost all actin polymerization
enzymes? Be as specific as possible.
Where is energy used in the movement of a single cell?
Bonus question: Where does the energy come from to move Golgi
vacuoles to different parts of the cell? There are two very different answers…
This diagram contains
an implicit inaccuracy.
What is it?
nucleus
ER
Mitochondrion
Concept Questions
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Why do you expect amino acid side chains on the outside of an integral membrane protein
(but within the bilayer) to be hydrophobic?
Explain the matches between three possible transport situations…
– facilitated diffusion, active transport, and passive diffusion
…and three cellular situations
– a need for extreme rapid transport, intake of a common large molecule, letting a rare
waste molecule out of the cell
What specialized enzymes would you expect in a mitochondrion? In the Rough ER? What
microenvironment is unique to the nucleus? To the peroxisome?
Imagine:
– 1) a lipid destined to become part of the plasma membrane, and
– 2) a protein that will be released outside of the cell.
• Describe the differences in the pathways taken by each molecule.
Where or when does each pathway utilize the joining of lipid membranes?
What would happen to a crawling cell that instantly lost all actin polymerization enzymes?
Be as specific as possible.
Where is energy used in the movement of a single cell?
Bonus question: Where does the energy come from to move Golgi
vacuoles to different parts of the cell? There are two very different answers…