1. Cells
Scanning electron microscope image of a leaf from a Black Walnut tree. Image shows a cross-section of a cut leaf, itsupper epidermal layer, mesophyll layer with palisade cells and vascular bundles, and lower epidermal layer. The protrusion at center is just over 50 microns tall. (Dartmouth Electron Microscope Facility/Dartmouth College)#

2. Fish gills

3. Scanning electron microscope image of an ant
Scanning electron microscope image of an ant. Its eye is approximately 300 microns wide.

4. Pollen from a variety of common plants: sunflower, morning glory, hollyhock, lily, primrose and caster bean. The largest one at center is nearly 100 microns wide. (Dartmouth Electron Microscope Facility/Dartmouth College) #

9. Cells carry out all functions necessary for life
growth: an irreversible increase in size
homeostasis: keeping conditions inside the organisms within tolerable limits
metabolism: chemical reactions inside the cell, including cell respiration to release energy
nutrition: obtaining food, to provide energy and the materials needed for growth
reproduction: producing offspring either sexually or asexually
sensitivity: perceiving and responding to changes in the environment

10. What is the cell theory?
all living things are made of one or more cells
the cell is the smallest unit of life
all cells come from pre-existing cells

11. Evidence for the cell theory?
All living things are made of one or more cells
microscopes allow us to observe that all living things are either unicellular or multicellular
Robert Hooke: pioneering microscopist, cork cell
Antonio Van Leeuwenhook: master lens maker, animacules

12. Evidence for the cell theory?
The cell is the smallest unit of life
nothing smaller than a cell can survive independently
subcellular structures cannot survive independently (nuclei, ER, golgi, chloroplasts, mitochondria)
the lower limit on cell size is about 200nm, large enough for DNA, ribosomes, and membranes

13. Evidence for the cell theory?
All cells come from pre-existing cells:
Does this imply that life ALWAYS existed?
Contradicts with geological evidence
Exception made for the origin of life, when cells arose from non-living substances

14. Relative sizes of cells
molecules: ~ 1 nm
cell membrane thickness: ~ 10 nm
viruses: ~ 100 nm
bacteria: ~ 1 µm
organelles: up to 10 µm
eukaryotic cells: up to 100 µm

15. Prokaryotic vs. Eukaryotic cells
All cells contain small specialized structures called organelles
Prokaryotes = cells that do not have membrane bound organelles (e.g. most unicellular organisms, such as bacteria)
Eukaryotes = cells that contain membrane bound organelles (e.g. most multicellular organisms, such as us!)

16. Cell types
Textbook pages p. 171 – 187

17. Microscope tutorial

19. Prokaryotic vs. Eukaryotic cells
All cells contain small specialized structures called organelles
Prokaryotes = cells that do not have membrane bound organelles (e.g. most unicellular organisms, such as bacteria)
Eukaryotes = cells that contain membrane bound organelles (e.g. most multicellular organisms, such as us!)

20. Animal vs. Plant cells Plant cell Animal cell
Outer cell wall + plasma membrane => fixed, angular shape
Plasma membrane => flexible, rounded shape
Chloroplast
No chloroplast
Large vacuole
Vacuole
No centriole
Centrioles

21. Why is the cell small?

22. Why is the cell small? Surface area determines rate of exchange
Volume determines metabolism
As cell size increases, volume increases proportionally faster than SA => SA: V ratio decreases
Low SA reduces rate of exchange while high V increases metabolic demands
Cell cannot meet needs of metabolic demands

23. Stem Cell Research & Beyond

24. Why do cells look so different?
Stem cells = Cells that retain capacity to divide and differentiate along different pathways (pluripotent)
multicellular organisms can differentiate into a variety of interdependent cell types
each specialized to carry out a subset of functions  greater efficiency
cellular differentiation
achieved through differential gene expression
all cells in an organism have identical DNA

25. Stargardt’s disease Junvenile Macular Degeneration

26. Lymphoma Blood cell tumors that develop from lymphocytes

27. What’s the problem?
Use of embryonic stem cells, often obtained from laboratories carrying out in vitro fertilization (IVF)
Death of embryo – taking human life?
Adult stem cells: limited to differentiating into cell types of their tissue of origin & difficult to find in the tissue due to rarity

28. microbe

32. plant