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Anatomy - Cells and Cell Transport

Modified from various presentations by David Knuffke.
by

Jed Doyle

on 2 June 2016

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Transcript of Anatomy - Cells and Cell Transport

A Tour of The Cell
Introduction
Dead White Men Who Discovered (and were made of) Cells:
The Wide World of Cells:
Discovery of Cells (1600's)
Anton van Leeuwenhoek
Robert Hooke
First person to look at biological material under a high powered (~100X) microscope
Coined the term "cells" to describe the appearance of cork under a microscope
...These are not the only 2 contributions

Cytology: The study of cells
Cell Theory:
All living things are made of cells
The cell is the basic unit of life
All cells come from pre-existing cells
Cytology Techniques
Microscopy
Light Microscopy:
Maximum Magnification- 1000X
Maximum Resolution- 10 micrometers (um)
Types of light microscopy:
Electron Microscopy:
Maximum Magnification- 10,000,000X
Maximum Resolution- 20 nanometers (nm)
Types of electron microscopy:
Cell Size:
Cell Types:
There are physical constraints on cell size:
Too small: Can't fit all the stuff inside
Too big: Can't exchange matter with the environment efficiently.
Cells exist in the 10 um - 1 mm size range.
Prokaryotic
"simpler" (no membrane bound organelles)
smaller (typically 10-100 um)
Much more abundant
Eukaryotic
lots of membrane bound organelles.
larger (100 um - 1mm)
2 major types
"Plant-like"
"Animal-like"
(photoautotrophic)
(chemoheterotrophic)
Remember Me?
You Need To!
The Utility of Membrane-Bound Organelles
Why organelles?
By enclosing parts of the cell in membrane, eukaryotic cells are able to SPECIALIZE!
Membranes isolate different areas of the cell, which allows the cell to have varied conditions in different regions (different pH, concentrations of different molecules, etc.)
Membranes also provide surface for various reactions (Respiration and Photosynthesis, for instance).
The specialization of cellular regions is what makes eukaryotic cells so much more complex than prokaryotic cells.
Specialization is also a prerequisite for multicellular life (why?)
So many compartments = So many options
The Life of the Cell
All cells must do the following things to stay alive:
Process matter: Molecules need to be acquired, synthesized and digested
Process energy: In order to process matter, energy must be provided. This energy usually comes from one of two places (where?)
Process information: The instructions that enable the cell to process matter and energy must be interpreted by the cellular system. Signals from the environment must also be interpreted.

Many cells will also do the following :
Reproduce: The information that runs the cell must be passed on to new generations of cells.
Communicate: Cells respond to/direct other cells.
Cells have systems to do all of these things!
2 Major Points
Proteins
The Endomembrane System
Proteins are the molecules that a cell uses to do most of its work.
Here is a brief list of things that proteins do:
Build molecules
Digest molecules
Carry out chemical reactions
Provide structure
Copy DNA & RNA
Receive and send messages to the environment/other cells
Receive and send messages to other cells

The instructions to build proteins are stored in DNA (we can call them "genes")
The nucleus
Ribosomes
Structure: a double membrane, with protein pore channels
Function: site of DNA storage and replication, information relay to ribosomes
flourescence image showing nuclei (yellow)
Structure: a complex of RNA and protein. 2 subunits ("large" & "small"). Eukaryotic ribosomes are larger than prokaryotic ribosomes.
Function: site of protein synthesis, using an RNA transcript of a gene
The nucleolus is the region of the nucleus where ribosomal RNA genes are concentrated.

It can be seen under magnification as a dark spot on the nucleus.
How eukaryotic cells send proteins from ribosomes to their particular destinations
2 Kinds of Ribosomes
"Free":
floating in cytoplasm
make proteins that stay in the cytoplasm
"Bound":
Attached to Endoplasmic Reticulum ("ER")
make proteins that go into membranes, or are exported from the cell.
Ribosomes become free/bound based on the protein they are making
Endoplasmic Reticulum
Structure: a network of membrane channels attached to the nuclear membrane.
2 kinds:
rough: closest to nucleus, covered in bound ribosomes
free: farther from nucleus, no bound ribosomes
Function: Rough ER compartmentalizes the cell, provides structural support, & targeted protein synthesis. Smooth ER synthesizes lipids for the cell (for things like membrane), detoxifies compounds, breaks down glycogen.
Vessicles
Structure: A small compartment surrounded by membrane
Function: Various, depending on the contents.
Golgi Apparatus
Structure: A series of flattened, mebrane-bound sacs
Function: synthesis, modification & packaging of molecules
Plasma Membrane
Structure: a phospholipid bilayer with embedded proteins.
Function: Controls transport of matter into and out of cell.
Recieves/Sends messages with environment.
The Endomembrane System
Big Questions:
Why does life require cells?

How are cells organized?

What is the advantage to having organelles?

How do the interactions of cellular components allow for life processes?
Explain the cell theory

Compare different types of microscopy.

Explain why there are no giant cells around.

Refine your contrast of prokaryotic and eukaryotic cells.

Relate the structure and function of the organelles in this presentation.

Explain the interactions of the organelles in this presentation.

Explain how the organelles in this presentation provide for essential life processes.
Make Sure You Can:
A Ribosome!
"Open" Junctions
Big Questions:
What does the internal structure of a cell look like?

How do cells separate themselves from their environments?

How do cells communicate with the environment?

How do cells communicate with other cells?
Explain why cells need to have internal structural organization and support.

Explain the structure and function of the cytoskeleton.

Compare the components of the cytoskeleton.

Explain the structure and function of the cell membrane.

Describe the roles of phospholipids, cholesterol, and membrane proteins in cell membrane function.

Explain the structure and function of the cell wall.

Compare the structures of plant-like, fungal, and bacterial cell walls.

Explain the structure and function of the extracellular matrix.

Compare the structure and function of different types of intercellular junctions.
Make Sure You Can:
Inside the Cell:
At the Boundary:
Outside the Cell:
Between Cells:
The Cytoskeleton
Structure:
A network of structural proteins that extends throughout the cytoplasm.
Functions:
Structural support
Maintaining cell shape
Anchorage of organelles
Regulation of cell & organelle motility
Movement of chromosomes during cell division
Cilia & Flagella
Structure:
Motility related extensions of cytoskeletal proteins
Centrosome
Function:
Structure:
Animal-like cell only microtubule-organizing center
Function:
Origin of all microtubules in cell. Major role in animal-like cell division
Cell Wall
Intercellular Junctions
ECM
(Extracellular Matrix")
Structure:
A cross-linked network of structural polysaccharides.
Function:
Structural support only! Cell walls are non-living
Cellulose:
Plant-like cells
Chitin:
Fungal cells
Bacterial Cells
Peptidoglycan:
No Cell Walls in Animal-like Cells!
Structure:
A network of connective proteins and "proteoglycan" molecules outside of the cell membrane of animal cells
Function:
Cell anchorage. Cell communication.
Only animal cells have any major ECM...
Structure:
Proteins that connect cells to other cells.
Depending on the junction, a channel between cells may exist
"Closed" Junctions
Functions:
Anchorage & Transport ("open" junctions only)
The Cell Membrane
Structure:
Functions:
The "Fluid Mosaic Model": A phospholipid bi-layer with associated proteins
Boundary of cell
Transport of materials in and out of the cell
Communication between cell and environment
Cytoskeletal elements stained green & orange
Motor proteins connect vessicles to microtubules
intermediate actin filaments play a large role in cell motility
green = microtubules
red = microfilaments
The cytoskeleton is a dynamic regulator of cellular structure and function
Motion of the cell through space
Cholesterol:
Structure:
a steroid lipid
Function:
acts as a "temperature buffer" to help maintain membrane fluidity over a range of temperatures
Membrane Proteins:
Structure:
Various, depending on the role they play:
Integral proteins: penetrate one or both layers of the bi-layer.
Peripheral proteins: associated with the membrane, but don't penetrate the bi-layer.
The polarity of different regions of a membrane protein vary according to the role of that protein.
Functions:
Many and more. Here's brief overview:
Spotlight: Membrane Receptors
Structure:
Integral proteins that span the bi-layer with regions ("domains") that extend extra- and intra-cellularly.
Function:
Signal Transduction: The reciept of chemical messages from the environment and the relay (transduction") of those messages into the cell for response.
Spotlight: Glycoproteins
Structure:
Integral proteins that span the bi-layer with short polysaccharide residues projecting extra-cellularly into the environment
Function:
Cell-Cell Recognition: Glycoproteins serve as an identifying marker in cellular populations (like your body).
Membrane receptors are exploited by viruses (how?)
Glycoproteins are a complication for organ transplants (why?)
lipids with a phosphate attached to glycerol in place of a fatty acid tail.
polar (hydrophilic) phosphate "head", nonpolar (hydrophobic) fatty acid tails. This type of polar/non-polar molecule is called "amphipathic"
Spontaneously organizes in the presence of water to form a bi-layer
fluid: phospholipids are constantly moving
Structure:
Function:
Membrane Phospholipids:
Makes a "selectively permeable" membrane. Only small, non-polar molecules can easily move through the phosopholipid bi-layer (Why?)
membrane proteins are mobile in the cell membrane:
Each component of the cytoskeleton is assembled from protein subunits
Structure of chitin:
Structure of peptidoglycan:
Structure of cellulose:
Gap Junctions:
Open channels between animal cells
Desmosomes:
Cellular "rivets" that anchor cells to basement mebranes in tissues
Tight Junctions:
Cell-cell connections that make a waterproof seal.
Passive Transport
Movement of material from [High] to [Low]
No energy required
Chemistry must be Considered
A Free Ride
Diffusion:
The passive transport of molecules accross a semi-permeable membrane
Osmosis:
The Diffusion of water (opposite direction to solute)
Movement of material from [Low] to [High]
Energy is required
Transport
Things
Spread
Out
Active Transport
All other things being equal:
* This is a consequence of the second law of thermodynamics, which says that the entropy of a system will increase unless energy is added to that system.

Locally energy is added in to living systems.

Globally, no energy is added to the net total energy of the Universe.
Entropy on 2 different scales
To Cancel
Tonicity is Important
Must Use A Protein!
Bulk Transport
Endocytosis
Exocytosis
Big Questions
How does the cell control what is transported at the cell membrane?

Why is transport of materials between the cell and its environment necessary for life?

How does the environment influence living systems?

How do cells exist within the confines of the Laws of Thermodynamics?
Diffusion is an emergent & inescapable property of large concentrations of constantly moving molecules
What can diffuse through the bi-layer?
What does all the other stuff do?
Transport Proteins!
aquaporins and ion channels
Channels and Carrier proteins control the diffusion of charged and polar molecules
How can you "control" diffusion?
What's Happening Here?
What's Happening Here?
The Sodium Potassium Pump:
ATP Fills The Energy Reqirement
Tonicity is a relative measure of solution concentration
The tonicity of a cell's environment has serious consequences for the cell
Tonicity as it effects plant and animal cells.
Explain all situations shown!
Circles indicate homeostatic condition
Which way does sucrose go?
What if it can't?
The contractice vacuole of a paramecium is an adaptation for living in an environment that is hypotonic compared to the cell
Different osmoregulatory adaptations in salt-water and fresh-water fish
vs.
Moving Big Stuff
Intake of large molecules.
more specialized.
"Cell eating"
"Cell drinking"
"Cell being picky"
Release of large cellular products into outflow
Remember Me?
Any Questions?
A "Phagocyte"
Make Sure You Can
Explain how the consequences of the second law of thermodynamics allow diffusion to occur in the universe without an input of energy.

Compare passive and active transport.

Compare facilitated and simple diffusion.

Compare diffusion of a solute with osmosis of water.

Determine the tonicity relationships when given the concentrations of solutes of multiple solutions.

Predict the movement of specific molecules when given information about their relative concentrations and the characteristics of a given semi-permeable membrane.

Explain why animals and plants have evolved adaptations to survive in solutions of different toncities.

Predict the effect of altering tonicity on a plant or animal cell.

Compare exocytosis and endocytosis.

Explain the purposes and processes of the different modes of endocytosis employed by the cell.
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