Biology 1A    Sept 3, 1998
Lecture 3 - Cells

Page Contents :

• Reading Assignment
• Overview of Lecture
• Overview of Lab
• Lecture Outline
• Vocabulary
• Study Questions
• Related Websites

Stern: Chapter 3

Overview of Lecture:

All living organisms are composed of cells.
All cells come from other cells.
Living cells are bounded by a lipid membrane.
Survey of cellular machinery.

Overview of Lab:

(A bullet indicates a handout.)
• Observation of mitosis / plant cells.

A. Cells are the units of life.
1. Plants, animals, fungi, protists, bacteria ALL are made of cells. (Question: What about viruses?)
2. Variation in size of cells
3. Most multicellular organisms begin life as a single cell.
a. Development - the process by which a multicellular organism is produced from a single cell.
b. Three primary cell activities in plant development: division, growth, & differentiation
B. Early cell discoveries
1. Robert Hooke - coined the term cell after viewing cork under the microscope (Question: what did Hooke actually see?)
2. Antonj van Leeuwenhoek - Dutchman who discovered bacteria, protists, & blood cells
3. Robert Brown - English botanist who discovered Brownian motion and coined the term nucleus
4. Jean Baptiste de Lamarck - French biologist who said that, "no body can have life if its constituent parts are not cellular tissue or are not formed by cellular tissue."

A. Later cell discoveries
1. Matthias Schleiden & Theodor Schwann proposed the cell theory : "All organisms are composed of cells."
2. Rudolf Virchow said, "omnis cellula e cellula" (All cells from cells.)
3. Louis Pasteur - French chemist who disproved spontaneous generation.
B. Cell division
1. Mitosis is replication and division of the nucleus.
2. Stages are interphase, prophase, metaphase, anaphase, & telophase
3. Cytokinesis is separation of the cytoplasm.

A. plasma membrane (cell membrane)
1.8 nm thick
2. helps produce cell wall
3. selectively permeable - regulates flow into and out of cell
B. Fluid-mosaic model
1. phospholipid bilayer
a. Polar outside, nonpolar inside
b. Flexible and foldable
c. sterols stabilize the membrane in eukaryotes (e.g. cholesterol)
2. Proteins "float" in the membrane 3. Kinds of proteins in the membrane
a. anchoring proteins (e.g. cytoskeleton, flagellae)
b. permeases - transmembrane transport proteins
c. ion channels & pumps
d. cell-cell interaction proteins

A. Prokaryotic vs. Eukaryotic
1. prokaryote - a cell lacking a true nucleus (Bacteria & Archaea)
2. eukaryote - organism with a membrane-bound nucleus, cytoskeleton, and other organelles (Plants, Animals, Fungi, Protists)
B. The stuff of the cell is called protoplasm, and includes:
1. nucleus (in eukaryotes)
2. cytoplasm (everything else but the nucleus), and includes:
a. organelles - membranes and other complex structures
b. cytosol - mostly water, dissolved nutrients and ions, and enzymes
C. At the cell surface
1. cell wall (plants, fungi, bacteria)
2. flagellae and cilia
D. Internal membranes and support
1. Membranes are important in eukaryotes to partition the internal volume
a. vacuole - membrane-bound organelle for storage or waste disposal
b. ER - internal transport network
c. Golgi apparatus
d. vesicles - packaged from Golgi or other membrane
2. cytoskeleton - system of protein filaments (only in eukaryotes)
E. Ribosomes - small particles of protein and RNA; assemble proteins from amino acids
F. Semi-autonomous organelles in eukaryotes - chloroplasts and mitochondria
1. double membrane - smooth outer, folded inner
2. own DNA, replicate independently of cell, manufacture own ribosomes
3. mitochondria - energy generation by electron transport
4. plastids - site of photosynthesis (chloroplasts, chromoplasts, amyloplasts)
G. Nucleus
1. nuclear membrane - double, with regulated pores
2. nuceolus - site of rRNA synthesis (ribosomal RNA)
3. chromosomes - DNA
4. RNA
5. Controls cell function - experiments with nuclear transplantation in Acetabularia.

• How large is a typical bacterial cell? Animal cell? Plant cell?
• What are the three primary activities of plant development? Explain what happens in each stage.
• What is the significance of Robert Hooke's observation of cork cells?
• What is the "cell theory"?
• Explain how Pasteur disproved the idea of spontaneous generation.
• What are the stages of mitosis? What happens in each stage?
• Does mitosis occur in bacteria? How do you know?
• Besides mitosis, what must happen for a cell to divide?
• How thick is a typical cell membrane? How does this compare to the average size of biological molecules? How does this compare to the size of a typical bacterial cell?
• What are four kinds of molecules found in the cell membrane? How does each contribute to the functioning of the cell membrane?
• Why do certain proteins "float" in the cell membrane? (i.e. What keeps them there?)
• What is the difference between a prokaryotic cell and a eukaryotic cell?
• Would you expect to find lipids in the cytosol? Why or why not?
• Compare the chemistry of the cell wall in a plant, fungus, and bacterium.
• What organelles have membranes? Which organelles have their own DNA? Which help manufacture proteins? For each, explain its role in the functioning of the cell.
• Transplant experiments with the alga Acetabularia (mermaid's wine glss) showed that:
  a) the nucleus controls cell structure and form.
  b) all cells come from cells.
  c) cellulose is a polysaccharide in plant cell walls.
  d) all living organisms are composed of cells.

• UCMP - Eukaryote reproduction and morphology
• UCMP Glossary Vol. 4 : Cell Biology
• Antony van Leeuwenhoek
• Robert Hooke
• Jean-Baptiste Lamarck
• Cells Alive!