A Tour of the Cell Ch 4
light microscope 1000x
electron microscope
scanning electron microscope
transmission electron microscope
metal coated objects reflect electrons
thin slices of objects
cell size and surface area surface area to volume ratio
rbc’s are among the smallest cells
Cell Theory
Robert Hooke
All living things are composed of cells
All cells come from other cells
Prokaryotic Cell
Eukaryotic Cell
Kingdom Monera
no nucleus, loop of DNA
no membrane bound organelles
eubacteria and archaebacteria
Cellular metabolism
K. Protista, Fungi, Plantae, Animalia
True nucleus--membrane containing
genetic matter in chromosomes
Membrane bound organelles
the sum total of all chemical activities of the cell
Compartmentalization
*localized environmental conditions
*isolated reactions
*enzymes incorporated into membranes
*unique lipid / protein compositions, depending on their specific function
Nucleus
*contains most of the genes
DNA + proteins = chromosomes
= chromatin
nuclear envelope
*pores--entry / exit
*protein--shape and organize chromatin
chromosomes
*dispersed--non dividing cells
*condensed--cell preparing to divide
*species characteristic chromosome number
Nucleolus
*ribosome synthesis
10,000 / minute
messenger RNA (mRNA) transcribed in nucleus from DNA
I
\/
through nuclear pores--into cytoplasm
I
\/
attaches to ribosomes--genetic message translated into primary protein structure
Ribosomes
*protein synthesis
*cells with higher protein synthesis have many ribosomes (liver--few million)
*in prokaryotic and eukaryotic cells
*2 subunits--join when they attach to mRNA
free ribosomes--proteins for cytosol
bound ribosomes--attached to E.R.
proteins for : membrane inclusion
export
Endomembrane System
interrelated directly--contact
interrelated indirectly--through vissicles
vessicles--membrane enclosed sacs, pinched off one membrane, moving to another
---------------
-------
-------
---------------
------------------
------------------
----------------
--
------------------
--------
----
--
system includes:
nuclear envelop
endoplasmic reticulum
golgi apparatus
lysosomes
vacuoles
plasma membrane
endoplasmic reticulum (ER)
network of tubes and sacs continuous with nuclear envelope
Smooth ER (lacks surface ribosomes)
a. synthesizes lipids, phospholipids, steroids
ex. mammalian sex hormones and steroids from adrenal glands testes, ovaries, skin oil glands
b. carbohydrate metabolism
c. detoxifies drugs and poisons
esp. in liver, add -OH, therefore soluble--excretable
d. stores Ca+
muscle contraction
Rough ER
a. protein synthesis
*growing protein enters E.R. tubules
*folds
*processed if necessary (add sugars)
*pinched off into vessicle
b. membrane synthesis
membrane proteins and phospholipids ate inserted into ER-(may be transported as a vessicle
elsewhere)
Golgi apparatus
made of stacks of flattened sacs
*receives vessicles from E.R
A. *modifies the contents
B. *pinches off products
alters chemicals
targets products for target organelles
sorts products for secretion
Lysosomes
*membrane enclosed hydrolytic enzymes
lipases, carbohydrases, proteases, nucleases
*isolated hydrolytic enzymes from cytosol
*pumps H+ inside to maintain pH5
*made by golgi
functions
A. intracellular digestion
*amoeba--fuses with food vacuole
*macrophage--fuses with bacteria and other invaders
B. recycle cell’s own organic material
*engulf / digest organelles
*release monomers
C. programmed cell destruction
*during metamorphosis / development
-------->
--------->
hand (webbing)
human diseases
from impaired lysosome function
*glycogen build up in liver (missing enzyme for hydrolysis)
*Tay-Sachs--lipid build up in brain
Vacuoles
membrane enclosed sac (LARGE)
*food vacuole
form by phagocytosis site intracellular digestion
*contractile vacuole
pumps excess water from protozoan
*central vacuole
most mature plan cells
stores: products, ions, dangerous cell byproducts, pigments (flowers), poisons (protect
plant), absorb water / elongate cell
Endomembrane Relationships
nuclear
envelope
extension
-------------->
of
rough E.R.
I
continuous
<--------------with
smooth
E.R.
I
secretory proteins are transported in
I
\/
vessicles
I
fuse with the
I
forming face of
I
\/
golgi apparatus
I
pinches off I maturing face
I
\/
give rise to ------------vessicles------------fuse, add, secrete
I
I
I
I
\/
\/
lysosomes, tonoplast
plasma membrane
E.R. produced, membrane and
I
Peroxisomes (microbodies)
membrane bound organelle (single)
*most eukaryotic cells
a. *enzymes that transfer H from various substrates to O
2
b. *enzymes that convert toxic H O to water
2 2
c. *enzymes that breakdown fats to acetyl CoA
d. *enzymes that detoxify alcohol and other harmful compounds
remove H--give to O
2
microbodies--(plant seeds)
*enzymes
lipids----->carbohydrates
E stored in oil available
????Produced by pinching off other peroxisomes????
Energy Transducers
mitochondria / chloroplast
change energy acquired from surroundings into forms usable for cellular work
*contain DNA, ribosomes
*reproduce within the cell
Mitochondria
a. site of cell respiration
catabolic, O requiring, make ATP
2
in most eukaryotic cells
smooth outer membrane
convoluted inner membrane
embedded enzymes for cell respiration
Plastids
Chloroplasts (3)
a. site of photosynthesis
structure
thylakoids
stroma
plastids are made from proplastids
amyplasts--colorless, store starch roots, tubers
chromoplasts--pigments-color of fruit, flowers, fall leaves
chloroplasts--pigments (including chlorophyll)- site of photosynthesis
change shape / move / divide
proplastids fate determined by cell location and environment
proplastid + light -----> chloroplast
Cytoskeleton
fibers throughout cell
shape
movement (by changing shape)
3 types of fibers
microtubules
microfilaments
intermediate filaments
microtubules
*support
*tracks for organelle movement
*separate chromosomes (cell division)
*cilia / flagella
microfilaments
*actin / myosin filaments---slide past each other
*pinch cell in two (cell division)
intermediate filaments
*fix organelle position
Plasma Membrane
phospholipids bi-layer controlling entry into/out of cell. semipermeable
Cell Surface--external to plasma membrane
cell wall--plants
cellulose + proteins, polysaccharides
protect, shape, stop H O uptake
2
young cells--thin flexible cell wall
pectin--sticky / between cells
older cells--thicken
glycocalyx--animal cells
sticky oligosaccharides bonded to proteins and lipids of plasma membrane
cell to cell attachment
cell recognition
PLANTS—vacuole [tonoplast], chloroplast, cell wall
vs
ANIMAL CELL--centrioles
Manufacturing
nucleus, ribosomes, rough e.r., smooth e.r., golgi
Breakdown
lysosomes, peroxisomes, vacuoles
Energy processing
chloroplasts, mitochondria
Support, movement, communication between cells
cytoskeleton, cell wall, extracellular matrix, cell junctions