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Biology 102
Lecture 8: Cell structure and
function (Parts 1 and 2)
Lecture outline
1. History of cell study
2. Basic attributes of cells
3. Cell structures
I. The history of cell study
A. Robert Hooke—1665—coined
the word cell, looked at cork
cells
B. Antonie van Leeuwenhoek
•
•
Created optics that could
visualize single cells
His technology “lost” for nearly
200 years
C. Robert Brown—1831—
discovered the "nucleus"
I. The history of cell study
D. Theodor Schwann—1838—
viewed animal cells in cartilage
1. Cells are the elementary
particles of plants and animals
E. Mattias Schleiden—Cells are the
fundamental basis of life
F. Virchow—1858—All cells come
from cells
I. The history of cell study
F. Cell theory
1.
All living things are composed
of one or more cells
•
What about viruses?
2. Cells are the basic unit of
structure and function
3. All cells come from preexisting
cells
II. Attributes of cells
A. Cell size
1. 1–100µm
II. Attributes of cells
2. Why is there a limit to cell size?
a. Surface-to-volume ratio
b. Distance from surface to center
II. Attributes of cells
B. Cell types
1. Prokaryotic—no nucleus (or other
membrane-bound organelles) circular
DNA, ribosomes
II. Attributes of cells
B. Cell types
2. Eukaryotic—larger, nucleus,
linear chromosomes,
membranous organelles
III. Cell structure
A. All cells (prokaryotes and
eukaryotes) possess a plasma
membrane, cytoplasm, genetic
material and ribosomes
1. Plasma membrane has phospholipid
bilayer, embedded glycoproteins
a. Isolates cytoplasm from
environment
b. Regulates molecular movement into
and out of cell
c. Interacts with other
cells/environment
III. Cell structure
A. All cells possess a plasma
membrane, cytoplasm, genetic
material and ribosomes (cont.)
2.
Genetic material—DNA, found
in the nucleus (of eukaryotes)
•
Within cytoplasm of
prokaryotes
3. Cytoplasm—water, salts, organic
monomers and polymers
a. Contains organelles
III. Cell structure
B. Organelles
1. Ribosomes assemble amino acid
monomers into polypeptide
chains
a. Associated with the ER in
eukaryotes
b. Composed of RNA and proteins
c. Both prokaryotes and
eukaryotes have ribosomes
d. NOTE: Other organelles are
present only in eukaryotes
III. Cell structure
B. Organelles (cont.)
2.
Endoplasmic reticulum consists of
folded membranes contiguous with outer
nuclear membrane
a. Rough ER: protein synthesis and secretion
b. Smooth ER: lipid synthesis and secretion
3.
Golgi apparatus: membranous sacs
associated with the ER
a. Sorts proteins and lipids by destination
b. Modifies some molecules
c. Packages these materials, then transports
them to appropriate location
4.
Lysosomes are Golgi-derived vesicles
containing digestive enzymes
Flow of membrane within the cell
•Follow pathway of
membrane flow
•Nucleus
•ER
•Golgi apparatus
•Lysosomes (and
other packets of
materials)
•Plasma membrane
III. Cell structure
B. Organelles (cont.)
5. Mitochondria provide energy for
cellular functions
a. Membrane-bound (two
membranes)

Most concentrated in
metabolically active cells (i.e.
muscles)
b. Break down molecules to obtain
their energy

Energy stored “short-term” as
ATP
c. Have their own DNA and
ribosomes; self-replicate
Structure of a mitochondrion
Note: Different reactions occur in
different parts of the mitochondrion
Plant cells: Have all the organelles
previously mentioned, and also…
III. Cell structure
B. Organelles (cont.)
6. Vacuoles
a. Large, water-filled
spaces (cell sap)
b. Can take up over 90%
of cell volume
c. Surrounded by
tonoplast (a single
membrane)
d. Functions:
1) Storage of red/blue
anthocyanins,
acids, salts, wastes
2) Maintain cell
pressure (turgor
pressure)—wilting
Maintenance of turgor pressure
III. Cell structure
B. Organelles (cont.)
7. Chloroplasts
a. Note double membrane
b. Green—contain chlorophyll pigment
c. Stacks of thylakoids (grana) within stroma (fluid)
a. As for mitochondria, diff. parts have diff. functions
d. Have their own DNA and ribosomes; self-replicate
III. Cell structure
B. Organelles (cont.)
8. Other plastids
a. Storage of materials such as pigments
and starch (as in potatos)
III. Cell structure
B. Organelles (cont.)
8. Nucleus is control center of the
cell
III. Cell structure
B. Organelles (cont.)
Functions of the parts of the nucleus
a. Nuclear envelope (membrane) with
pores


Water, ions and ATP can pass
through pores
Other materials are regulated by
“gatekeeper” proteins in the pores
b. Nucleolus

Site of ribosome assembly
c. Chromatin



Between nucleolus and envelope
DNA and protein (not in nucleolus!)
Replication and transcription
III. Cell structure
C. Cell walls in plant cells,
prokaryotic cells, fungi
1.
Plants

2.
Cell walls of cellulose (Ch. 3)
Fungi

Cell walls of chitin (Ch. 3)
3.
Function: support, protection
4.
NOTE: Animal cells do not
have cell walls!
III. Cell structure
D. Cytoskeleton
1.
Network of protein fibers to which
organelles and even enzymes are
attached
Microfilaments
Intermed. Fil.
Microtubules
III. Cell structure
Cytoskeleton functions
1.
2.
3.
Cell shape
Organization of cellular structures
Cell movement

4.
Organelle movement


5.
Caused by assembly, disassembly
and sliding of the filaments
Ex: Endocytosis
Movement of membrane from ER to
Golgi apparatus, etc…
Cell division
III. Cell structure
E. Cilia and flagella are protein
microtubule extensions of the
plasma membrane
1.
2.
Cilia: short and numerous
Examples: within oviducts to move eggs,
filter-feeding in invertebrates, movement
of particles out of respiratory system
III. Cell structure
2. Flagella: longer and fewer