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Chapter 4
Life’s Home: The Cell
I.
Cells Are the Working Units of Life
A.
Cells are specialized to do certain jobs
B. Review of Metric System (mm–nm):
1 mm
1 um
1 nm
1 m = 100 cm
1 cm = 10 mm
1m = 1,000 mm
1 mm = 1,000 um
1um = 1,000 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,
many 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
Eukaryotic Cell
d) Multicellular and single-celled, larger size,
use oxygen
e) Five main components of eukaryotic cells
include nucleus, organelles, cytosol,
cytoskeleton, and plasma membrane:
Figure 4.3
• II. Animal Cells
A.Tour of Protein Production
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) Also, DNA is 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: Figure 4.7
b) Rough ER is embedded with ribosomes
c) Site where protein is made from mRNA “tape”
d) Can exist as free ribosomes in cytosol
e) Ribosomes are made in the nucleolus
f) Protein is processed and folded in interior of rough ER,
cisternal spaces
g) Membrane of ER buds off to form balls containing
proteins called transport vesicles
h) All the membranes of the cell form an
interconnected network (endomembrane
system)
i) Transport vesicles fuse with Golgi complex,
which modifies, sorts, and ships proteins to
their final destination
j) This entire pathway is demonstrated in an
animation from the resources for Chapter 4,
called figure 4_05.
3. Exocytosis—Vesicles fuse with outer cell
membrane for final export outside cell.
II.Animal Cells
B. Other Cell Structures (Section 4.5)
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)
Lysosomes don’t work in
Tay Sachs disease – child
dies before the age of 4-5.
3.
Mitochondria (Endosymbiosis sidebar) extracting
energy from food (mitochondria and disease)
Endosymbiosis – primitive cells were taken in by more
complex cells, and instead of being eaten, they became part of
the cell – thought to be true for chloroplasts and mitochondria
C. The Cytoskeleton (Section 4.6 and Figure 4.11)
1. Microfilaments (actin and movement
2. Intermediate filaments (skeleton)
3. Microtubules (motors)
4. Cilia and flagella
Cilia
Flagella
III. Plant Cells (Section 4.7)
A. Similarities between plant and animal cells: Figure
4.15
B. Differences:
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:
Chromoplasts – store pigment other than green
Leukoplasts – store starch ( turn black with iodine)
IV. Cell Communication (Section 4.8)
A. Next level of organization—from cells to tissues
B. Plant cell connections—
plasmodesmata:
C. Animal cell connections—
gap junctions:
Compound Light Microscope
light