Download Unit Five - Objectives 1-8

Cell Biology
Unit Five
Cellular Structures of
Intracellular Transport
Endoplasmic
Reticulum
A continuous network of flattened
sacs, tubules & vesicles, found
throughout the cytoplasm
Two basic types – smooth & rough
The functions are varied and
incorporated with other
organelles
Endoplasmic
Reticulum
Is not static, with many transport
vesicles budding off to carry
products to the Golgi apparatus
and other cell destinations
Rough Endoplasmic
Reticulum
Characterized by attached
ribosomes
Main function is the biosynthesis
& processing of proteins
Some proteins are produced in
the rough ER
Rough Endoplasmic
Reticulum
Other protein are imported and
processed (folded)
Carbohydrates added to proteins
to produce glycoproteins
Quality control - recognition and
removal of improperly folded,
modified or assembled proteins
Smooth Endoplasmic
Reticulum
No ribosome attachment and
more tubular in shape
Smooth ER functions are varied
Smooth Endoplasmic
Reticulum
Drug detoxification takes place
through the process of
hydroxylation
Enzymes for the process are most
numerous in liver cells, but are
also found in lung & intestinal
cells
Smooth Endoplasmic
Reticulum
Detoxified compounds include
drugs, excretory compounds and
inactive hormones
Forms isolation envelopes around
defective organelles
Smooth Endoplasmic
Reticulum
Carbohydrate catabolism is
carried out in liver cells,
hydrolyzing glycogen to glucose
Calcium storage for muscle
contraction in skeletal & cardiac
muscle (sarcoplasmic reticulum)
Smooth Endoplasmic
Reticulum
Lipid anabolism produces all but
a few cellular lipids
Enzymes for synthesis are in the
SER membrane
Acetic acid is the base for all the
lipids synthesized
Smooth Endoplasmic
Reticulum
Cholesterol is synthesized from
acetic acid and is converted into
many different steroids, including
the sex hormones
Almost all phospholipids are
produced in the SER
Smooth Endoplasmic
Reticulum
Lipid anabolism is carried out in
all cells, but more importantly in
adipose, adrenal cortex, liver &
gonad cells
Fatty acids are produced from
acetic acid in the cytoplasm
Cellular Structures of Intracellular
Transport
Golgi Apparatus
Comprised of a series of flattened
membrane bound cisternae (disk shaped
sacs)
Functions in chemical modification,
sorting and packaging of proteins
Works in close association with the ER
Golgi Apparatus
The Golgi apparatus is continually
surrounded by transport vesicles
The apparatus has two sides
~ cis face - (forming face) (CGN)
- oriented toward the ER
~ trans face - (maturing face) (TGN)
- oriented away from the
ER
Golgi Apparatus
Golgi Apparatus
The central sacs found between the CGN
& the TGN are the medial cisternae
The CGN, TGN & medial cisternae are
biochemically & functionally distinct, with
each containing enzymes necessary for
lipid and protein processing
Lysosomes & Endosomes
Lysosomes are specialized organelles
that store hydrolases that catabolize
proteins, carbohydrates & lipids
Lysosomes are used to digest food
molecules, unneeded materials found
inside the cell, pathogens or defective
organelles
Lysosomes & Endosomes
Lysosomes that consume substances
of extracellular origin are
heterophagic lysosomes
Lysosomes that consume substances
of intracellular origin are autophagic
lysosomes
Lysosomes & Endosomes
Lysosomal enzymes are produced in
the ribosomes of the RER,
transported to the Golgi & packaged
into vesicles called early endosomes
Early endosomes mature into late
endosomes, which may then mature
into a lysosome or deliver its enzymes
to an active lysosome
Lysosomes & Endosomes
Exocytosis
Endocytosis
Phagocytosis
Receptor
Mediated
Endocytosis
The Intracellular Relationship
Between ER, Golgi, Vesicles &
Plasma Membrane
Peroxisomes
Peroxisomes are single membrane
bound organelles involved with the
metabolism of hydrogen peroxide
Found in most cells, they are most
abundant in the liver & kidneys
They contain a mixture of enzymes
including hydrogen peroxide
generating enzymes as well as
catalase
Peroxisomes
Dehydrogenases remove hydrogens
from substances which are directly
transferred to oxygen to form
water
Some of the substances degraded
are toxins (methanol, ethanol, etc)
Catalase degrades H2O2 to H2O
and O2
Peroxisomes
Contain enzymes for the rapid
catabolism of large fatty acids
The smaller fatty acids are then
sent to the mitochondria
Peroxisomes
Plant peroxisomes also contain
enzymes used to convert oils into
glucose
Peroxisomes originate as buds of
the ER and their enzymes are
produced by cytoplasmic ribosomes
The Plant Vacuole
Plant cells usually have one large
central vacuole
The central vacuole has a limited
role in storage and carries out
some lysosomal like functions
Its primary function is the
maintaining of turgor pressure
The Plant Vacuole
The central vacuole is contained
within a differentially permeable
membrane called the tonoplast
The tonoplast helps maintain a high
solute concentration in the vacuole,
causing it to take on water
The Plant Vacuole
This swelling of the vacuole presses
the contents of the cell against the
cell wall, constituting and
maintaining turgor pressure
The
Plant
Vacuole