CHAPTER 4: STRUCTURE AND FUNCTION OF THE CELL
I.
DISCOVERY OF THE CELL
A.
INVENTION OF THE MICROSCOPE
1.
ROBERT HOOKE: FIRST VIEWED CORK UNDER PRIMITIVE MICROSCOPES
a.
DESCRIBED THE SPECIMEN AS CONSISTING OF “A GREAT MANY
LITTLE BOXES”, WHICH REMINDED HIM OF MONKS’ CELLS (THUS, THE
NAME
1) THESE WERE ACTUALLY THE REMAINS OF DEAD CELLS
2.
ANTON van LEEUWENHOEK WAS THE FIRST PERSON TO VIEW LIVING
CELLS (“ANIMALCULES”)
B.
THE CELL THEORY
1.
WAS ORGANIZED ABOUT 150 YEARS AFTER van LEEUWENHOEK
2.
DISEASE-STUDYING GERMANS SCHLEIDEN, SCHWANN & VIRCHOW
GATHERED MUCH OF THE EVIDENCE NEEDED TO DETERMINE THAT:



ALL LIVING THINGS ARE COMPOSED OF ONE OR MORE CELLS
CELLS ARE THE BASIC UNIT OF STRUCTURE AND FUNCTION
CELLS COME ONLY FROM EXISTING CELLS
C.
CELL DIVERSITY
1.
SIZE
a. SOME ARE LARGE ENOUGH TO BE SEEN WITH THE NAKED EYE
(CHICKEN EGG, SOME NERVE CELLS)
b. MOST ARE ONLY 10 µm (0.002 IN. IN DIAMETER)-50 µm (0.000008
IN.)
c. CELLS ARE LIMITED IN SIZE BY THE RATIO BETWEEN THEIR OUTER
SURFACE AREA (MEASURED IN UNITS2 AND THEIR INTERNAL VOLUME
(MEASURED IN UNITS3)
1) INSIDE GROWS FASTER THAN OUTSIDE CAN KEEP UP WITH
NUTRIENTS, WASTES, ETC.
2.
SHAPE
a. CELLS COME IN MANY DIFFERENT SHAPES
b. SHAPE IS SUITABLE FOR EACH CELL’S SPECIFIC FUNCTION
3.
INTERNAL ORGANIZATION
a. CELLS CONTAIN A VARIETY OF INTERNAL STUCTURES CALLED
ORGANELLES (“LITTLE ORGANS”)
1) COMPONENTS THAT CARRY OUT SPECIFIC FUNCTIONS FOR THE CELL
2) HAVE THE SAME FUNCTIONS AS THE ORGANS OF A MULTICELLULAR
ORGANISM
b. CELL MEMBRANES SURROUNDING EACH CELL HELPS MAINTAIN
ORGANIZATION AND HOMEOSTASIS
1) CELLS WITH ORGANELLES THAT ALSO HAVE MEMBRANES ARE CALLED
EUKARYOTES, BECAUSE THEY ALSO HAVE A NUCLEUS (MAY BE
UNICELLULAR OR MULTICELLULAR)
2) ORGANISMS W/O A NUCLEUS ARE PROKARYOTES (WILL ALL BE
UNICELLULAR)
II.
PARTS OF THE EUKARYOTIC CELLS
A.
CELL MEMBRANE
1.
encloses cell contents and is selectively permeable (lets some things in and out,
but not others)
2.
made primarily of lipids and proteins
B.
MEMBRANE LIPIDS
1.
PHOSPHOLIPIDS ARE THE PRIMARY MEMBRANE LIPID
a.
EACH HAS A HYDROPHILIC (POLAR) HEAD AND TWO HYDROPHOBIC
(NONPOLAR) TAILS—ARRANGED IN A LIPID BILAYER
2.
IS REFERRED TO AS THE “FLUID MOSAIC MODEL” BECAUSE IT BEHAVES MORE
LIKE A FLUID THAN A SOLID
C.
MEMBRANE PROTEINS
1.
PERIPHERAL PROTEINS
a.
ARE ATTACHED TO THE INTERIOR AND EXTERIOR SURFACES OF SOME
CELLS
b.
ARE WEAKLY LINKED TO LIPIDS OR OTHER PROTEINS EMBEDDED IN THE
LIPID BILAYER
2.
INTEGRAL PROTEINS
a.
EMBEDDED PROTEINS THAT EXTEND ACROSS THE ENTIRE MEMBRANE IN
SOME CASES (EXPOSED ON THE INTERIOR, EXTERIOR, OR BOTH)
b.
MAY FORM CHANNELS OR PORES FOR TRANSPORT OF CERTAIN
MOLECULES
D.
ORGANELLES
1.
NUCLEUS—DIRECTS CELL ACTIVITIES VIA THE DNA CONTAINED WITHIN
2.
NUCLEAR ENVELOPE—SEPARATES NUCLEUS FROM CYTOPLASM
3.
NUCLEOLUS—SPECIFIC REGION WITHIN NUCLEUS THAT CONTAINS GENETIC
MATERIAL
4.
NUCLEOPLASM—NUCLEAR CYTOPLASM
5.
VESICLES—STORAGE SACS
6.
GOLGI APPARATUS (BODY)—PACKAGES AND TRANSPORTS MOLECULES
7.
8.
9.
10.
11.
12.
SMOOTH ENDOPLASMIC RETICULUM (SER)—TRANSPORTS PROTEINS; HAS NO
RIBOSOMES
ROUGH ENDOPLASMIC RETICULUM (RER)—SITE OF PROTEIN SYNTHESIS; HAS
RIBOSOMES
LYSOSOME—CONTAINS PEROXIDE; RESPONSIBLE FOR DESTRUCTION OF CELLS
MITOCHONDRION (--IA)—SITE OF ENERGY CONVERSION (CELL RESPIRATION)
CENTRIOLE—IMPORTANT IN CELL DIVISION
PLASMA MEMBRANE—SELECTIVELY PERMEABLE MEMBRANE THAT HELPS KEEP
THE CELL INTACT; REGULATES TRANSPORT
PLANT CELLS—IN ADDITION TO THE ABOVE, PLANTS ALSO POSSESS THE FOLLOWING:
13.
PLASTIDS—CHEMICAL FACTORIES AND/OR STOREHOUSES
a. EX: LEUCOPLAST STORES STARCH
14.
CHLOROPLAST (A KIND OF PLASTID)—CONTAINS GREEN PIGMENTS WHICH
CONVERT SUNLIGHT TO STORED ENERGY
15.
CELL WALL—EXTRA SUPPORT TO THE PHYSICAL STRUCTURE OF THE CELL,
OUTSIDE OF THE CELL MEMBRANE
III.
HISTORY OF CELLS
A.
CYANOBACTERIA (BLUE-GREEN ALGAE)
1.
LIVED AT LEAST 3.5 BILLION YEARS AGO
2.
HAVE NO NUCLEUS (PROKARYOTIC)
3.
WERE THE ONLY LIVING THING FOR ½ THE AGE OF THE EARTH (~ 2.5 BILLION
YEARS)
B.
EUKARYOTES
1.
FIRST CELLS WITH COMPARTMENTS (NUCLEUS)
2.
EVOLVED ABOUT 1.5 BILLION YEARS AGO
3.
MUCH LARGER THAN BACTERIA
4.
HAVE SPECIFIC MEMBRANE-BOUND ORGANELLES FOR SPECIALIZED FUNCTIONS
C.
ENDOSYMBOSIS THEORY
1.
HYPOTHESIS: A BACTERIAL CELLS WAS ENGULFED BY A LARGER CELL & LOST THE
ABILITY TO LIVE INDEPENDENTLY (SYMBIOSIS)
2.
THE INVADING BACTERIA LOST THE ABILITY TO LIVE INDEPENDENTLY AND
BECAME ORGANELLES
a. SUPPORTING EVIDENCE: MITOCHONDRIA AND CHLOROPLASTS HAVE THEIR
OWN DNA AND REPRODUCE INDEPENDENTLY OF THE ENTIRE CELL
D.
MULTICELLULARITY (MULTICELLULAR ORGANIZATION)
1.
EARLY EUKARYOTES WERE SINGLE-CELLED
2.
EVENTUALLY THEY BECAME CLUSTERED INTO COLONIAL ORGANISMS WHICH
EXHIBITED DIVISION OF LABOR (PHOTOSYNTHESIS, REPRODUCTION, ETC)
3.
LED TO CELL SPECIALIZATION AND INTERDEPENDENCE AS COLONIAL CELLS
LOST THE ABILITY TO PERFORM CERTAIN FUNCTIONS (EX: NERVE CELL)
a.
CELLS THAT PERFORMED THE SAME FUNCTIONS ORGANIZED INTO
TISSUES
b.
TISSUES WORKED TOGETHER TO PERFORM A SPECIFIC FUNCTION, THUS
FORMING ORGANS (EX: HEART)
c.
ORGANS WORKING TOGETHER FORMED ORGAN SYSTEMS (HEART,
LUNGS, BLOOD VESSELS FORM THE CIRCULATORY SYSTEM)
d.
PUT ALL TOGETHER = MULTICELLULAR ORGANISM