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5
Life’s Home
The Cell
4.1 Cells Are the Working Units of Life
4.2 All Cells Are Either Prokaryotic or Eukaryotic
4.3 The Eukaryotic Cell
4.4 A Tour of the Animal Cell: Along the Protein Production Path
4.5 Outside the Protein Production Line: Other Cell Structures
4.6 The Cytoskeleton: Internal Scaffolding
4.7 The Plant Cell
4.8 Cell Communication: Why Cells Need Not Be Islands
LECTURE OUTLINE
I.
Cells Are the Working Units of Life
A. Specialization, complexity
B. Review of Metric System (mm–nm):
C. Every form of life is a cell, or is composed of cells, and every cell came from a cell.
D. All cells have: plasma membrane, cytoplasm, and genetic material (DNA).
E. Two main cell types differ mainly in where that DNA is kept: Comparison
1. Prokaryotic
a. “Before the nucleus”
b. Includes bacteria and archaea
c. DNA localized to a “nucleoid” region, not in membrane-enclosed compartments
called organelles
d. Small size, usually single-celled, don’t need oxygen
2. Eukaryotic
a. “True nucleus”
b. Includes all other kingdoms: animals, plants, fungi, and protists
c. DNA enclosed in membrane, along with other organelles
d. Multicellular and single-celled, larger size, use oxygen
F. Five main components of eukaryotic cells include nucleus, organelles, cytosol, cytoskeleton,
and plasma membrane:
II.
Animal Cells
A. Tour of Protein Production
1. Begins in the control center, the nucleus:
a. DNA enclosed in a double-thick membrane (nuclear envelope)
b. Also contains a nucleolus—“little nucleus”
c. In the nucleus, DNA is duplicated into DNA for each daughter cell.
d. DNA is also copied into RNA, messenger RNA, which can exit the nucleus
(through nuclear pores in the nuclear envelope) and travel to where proteins are
made, the cytoplasm:
2. In the cytoplasm:
a. mRNA head to rough endoplasmic reticulum, a series of flattened membrane sacs
called cisternae:
b. Rough ER is embedded with ribosomes
(1) Site where protein is made from mRNA “tape” (antibiotics and ribosomes)
(2) Can exist as free ribosomes in cytosol
(3) Ribosomes are made in the nucleolus
c. Protein processed and folded in interior of rough ER, cisternal spaces
d. Membrane of ER buds off to form balls containing proteins called transport
vesicles:
e. All cell membranes form an interconnected network (endomembrane system)
f. Transport vesicles fuse with Golgi complex, which modifies, sorts, and ships
proteins to their final destination:
g. This entire pathway is demonstrated in an animation
3. Exocytosis—vesicles fuse with outer cell membrane for final export outside cell.
B. Other Cell Structures
1. Smooth endoplasmic reticulum, site of lipid synthesis and detoxification.
2. Lysosomes—cell recycling. Break down large molecules from food, defective
organelles, or old proteins into their monomers for reuse (link to Tay-Sachs):
3. Mitochondria (Endosymbiosis Essay) extracting energy from food (mitochondria and
disease):
C. The Cytoskeleton
1. Microfilaments (actin and movement):
2. Intermediate filaments (skeleton)
3. Microtubules (motors)
a. Cilia and flagella
D. Overall review:
III. Plant Cells
A. Similarities between plant and animal cells:
B. Differences:
1. Cell wall: functions include structural strength, limit water absorption, and protection.
Composition is cellulose and lignin:
2. Central vacuole: functions include storing nutrients and water, involved in
metabolism, retains and degrades wastes, and some color.
3. Plastids: functions to gather/store nutrients, pigments, photosynthesis—chloroplasts:
IV. Cell Communication
A. Next level of organization—from cells to tissues
B. Plant cell connections—plasmodesmata
C. Animal cell connections—gap junctions