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Cells and Tissues - Lecture Notes | BIO 113, Study notes of Biology

University of Michigan (UM) - FlintBiology

cells and tissues lecture 1 Material Type: Notes; Class: Principles of Biology; Subject: Biology; University: University of Michigan - Flint; Term: Fall 2013;

Typology: Study notes

2012/2013

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BIO 326 Lecture 1: Cells and Tissues
1. Understand the 4 criteria for life and how they relate to cells.
a. All living things have DNA
b. All living things have a means of taking in energy from the outside world, and converting it to energy
they can use
c. All living things can sense and respond to change
d. All living things can reproduce
2. Understand the three tenets of cell theory.
a. Cell = the basic unit of structure in biology
b. Every organism either consists of cells or is itself a single cell
c. All cells arise only from preexisting cells
d. #1-2 developed in 1839 by Theodor Schwann, and #3 added in 1855 by Rudolf Virchow
3. Understand the basic principles of microscopy.
a. Microscopes magnify images
b. Resolving power: the fineness of detail that a microscope can reveal (the smallest distance that two
objects can approach one another and still be recognized as separate)
c. Resolution is a function of the wavelength of the illumination source employed
4. Understand the basic principles of light microscopy. Be able to identify micrographs taken using light
microscopy.
a. Light microscope
i. Uses visible light – sun or artificial source, wavelength of around 500nm – can distinguish
objects as small as about half of this: 250nm
ii. Can visualize the smallest cells and the major internal structures
iii. Uses 3 lenses:
1. Condenser lens focuses light on the specimen
2. Objective lens magnifies image
3. Projector lens (aka eyepiece) to convey magnified image to the eye
iv. Brightfield microscopy
1. Most living cells are largely transparent to transmitted light
2. (+) Overcome this by staining cells
3. (-) Stains are highly toxic so used when cells don’t have to be alive
v. Phase-contrast microscopy
1. Light travels at different speeds through regions of the cell that differ in composition
2. Converts these differences in refractive index into differences in contrast, revealing
more detail
5. Understand the basics principles of electron microscopy. Be able to identify whether micrographs were
taken using light or electron microscopy.
a. Transmission electron microscopy (TEM)
i. Electron gun produces beams which are focused onto the specimen. Some electrons are
absorbed and these areas appear darker; clearer areas are where electrons have passed
through.
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Download Cells and Tissues - Lecture Notes | BIO 113 and more Study notes Biology in PDF only on Docsity!

BIO 326 Lecture 1: Cells and Tissues

1. Understand the 4 criteria for life and how they relate to cells. a. All living things have DNA b. All living things have a means of taking in energy from the outside world, and converting it to energy they can use c. All living things can sense and respond to change d. All living things can reproduce 2. Understand the three tenets of cell theory. a. Cell = the basic unit of structure in biology b. Every organism either consists of cells or is itself a single cell c. All cells arise only from preexisting cells d. #1-2 developed in 1839 by Theodor Schwann, and #3 added in 1855 by Rudolf Virchow 3. Understand the basic principles of microscopy. a. Microscopes magnify images b. Resolving power: the fineness of detail that a microscope can reveal (the smallest distance that two objects can approach one another and still be recognized as separate) c. Resolution is a function of the wavelength of the illumination source employed 4. Understand the basic principles of light microscopy. Be able to identify micrographs taken using light microscopy. a. Light microscope i. Uses visible light – sun or artificial source, wavelength of around 500nm – can distinguish objects as small as about half of this: 250nm ii. Can visualize the smallest cells and the major internal structures iii. Uses 3 lenses:

  1. Condenser lens focuses light on the specimen
  2. Objective lens magnifies image
  3. Projector lens (aka eyepiece) to convey magnified image to the eye iv. Brightfield microscopy
  4. Most living cells are largely transparent to transmitted light
  5. (+) Overcome this by staining cells
  6. (-) Stains are highly toxic so used when cells don’t have to be alive v. Phase-contrast microscopy
  7. Light travels at different speeds through regions of the cell that differ in composition
  8. Converts these differences in refractive index into differences in contrast, revealing more detail 5. Understand the basics principles of electron microscopy. Be able to identify whether micrographs were taken using light or electron microscopy. a. Transmission electron microscopy (TEM) i. Electron gun produces beams which are focused onto the specimen. Some electrons are absorbed and these areas appear darker; clearer areas are where electrons have passed through.

ii. Must occur in vacuum because electrons may be slowed/scattered if they collide with air molecules iii. (+) Resolution of 0.1nm (much better than scanning electron microscope) iv. (-) Small region of cell, 2-D (as opposed to 3-D cell) v. (-) Complex prep process. Image must be very thin for electrons to pass through. vi. (-) Potential for artefacts - things that appear to be there due to errors in prep rather than actually being part of specimen

b. Scanning electron microscopy (SEM) i. Electrons are reflected back from the surface of a specimen as the electron beam scans rapidly back and forth over it ii. Also must occur in vacuum iii. (+) Wide depth of focus allows excellent impression of the 3-D shape of objects. iv. (+) Resolution = 1-20nm v. (-) Complex prep process vi. (-) Potential for artefacts

6. Understand the basics of fluorescence microscopy. Be able to describe the process of immunostaining to obtain images. a. Fluorescent molecules emit light when illuminated with light of a shorter wavelength b. Fluorescent dyes i. Some dyes specifically stain particular structures Example: Hoechst/DAPI bind tightly to DNA, and will only fluoresce when bound ii. Some dyes are attached to antibodies, and will reveal location of the protein of interest when used c. Genetically-encoded fluorescent molecules i. Green fluorescent protein (GFP) is classic example you will use in the lab ii. Cells induced to make proteins to which the GFP tag has been attached iii. Used to follow location of this protein in a living cell.

http://www.leinco.com/immunohistochemistry

i. The cell cycle is a carefully coordinated set of events that ensures successful cell division into two identical daughter cells ii. G1 (gap 1): cell grows and checks that it has necessary energy and materials to proceed to the next phase; assures that DNA is undamaged before replication in the S phase iii. S (Synthesis): DNA replication iv. G2 (Gap 2): cell checks that DNA is fully replicated before M phase, chromosomes condense v. M (Mitosis): chromosomal segregation occurs

  1. Prophase (breakdown of nuclear envelope, chromosomal condensation, doubling and movement of centrioles aka microtubule organizing centers to poles)
  2. Metaphase (microtubules attach at centromere of sister chromatids, resulting tension aligns them in the center of the cell)
  3. Anaphase (cohesin binding sister chromatids together dissolves, allowing microtubules to pull one half of each chromatid to each pole)
  4. Telophase (new nuclear envelope forms)
  5. Cytokinesis (establishment of plasma membrane, producing 2 individual daughter cells) 10. Understand the terminology of eukaryotic cellular microenvironment. a. Extracellular matrix: the meshwork of filaments and fibers that surrounds and supports mammalian cells b. Interstitial fluid: the aqueous medium outside cells

Restriction point

http://facweb.northseattle.edu/esekulic/ntr150/Protein/protein2.htm

c. Tissue: group of specialized cells with a common function

Image source: ADAM

11. Summary a. All living things are made of cells, their foundational, basic structure. These cells come from other preexisting cells. b. All cells contain DNA, can reproduce (if not terminally differentiated), take in energy from external environment and convert it to energy they can use, and sense and respond to change. c. Microscopy has been an instrumental means for learning about cells. There are different types of microscopy specialized for different applications. d. Cells come in 2 basic types, 3 domains, which are distinct from one another molecularly and behaviorally e. Multicellular eukaryotic cells live as part of specialized tissues.

Example quiz/test questions:

  1. Suggest a way to distinguish between bacterial cells and archaeal cells that does NOT include looking at its environment.
  2. A population of T cells has been stimulated to proliferate in response to a particular antigen. A sample of 1000 cells is examined microscopically, revealing that 200 of these cells are in the various stages of mitosis. Of the remaining 800 in interphase, 400 have x amount of DNA, 250 have 2x, and the remaining 150 have amounts somewhere between x and 2x. How many cells are in G1 phase? S phase? G2 phase?