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chapter 6: a tour of the cell - Coggle Diagram
chapter 6: a tour of the cell
Concept 6.1: Biologists use microscopes and
biochemistry to study cells
Cell fractionation
- takes cells apart and
separates the major organelles from one another
uses Centrifuges -
spins specimen around to get better visualizing
microscopy
- to see the cells and their parts
2 basic types of electron
microscopes (EMs)
are used to study subcellular structures
Scanning electron microscopes (SEMs
)= beam of electrons onto the surface of a specimen,
providing images that look 3-D
Transmission electron microscopes (TEMs)
= used mainly to study the internal structure of cells
light microscope (LM)-
visible light is passed
through a specimen and then through glass lenses
The resolution of standard light microscopy is too
low to study
organelles
= membrane structures in eukaryotic cells
Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions
all cells have plasma membrane, chromosomes, ribosomes, and
cytosol
( Semifluid substance)
Prokaryotic cells- have these - no nucleus, DNA in an unbound region called the
nucleoid
,
Cytoplasm
bound by the plasma membrane
Eukaryotic cells
are characterized by having DNA in nucleus by double membrane,
Cytoplasm
in the region between the plasma membrane and nucleus.
plasma membrane
- selective barrier that
allows sufficient passage of oxygen, nutrients, and
waste to service the volume of every cell.
Concept 6.3: The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes
nucleus
- contains most of the cell’s genes
nuclear envelope-
encloses the nucleus,
separating it from the cytoplasm
nuclear side of the envelope is lined -
nuclear lamina
, which is composed of proteins and maintains the shape of the nucleus
nucleus, DNA is organized by units -
chromosomes
Each chromosome contains one DNA molecule associated with proteins, called
chromatin
nucleolus
- located within the nucleus, is the
site of ribosomal RNA (rRNA) synthesis
Ribosomes
are complexes made of ribosomal
RNA and protein - 2 locations cytosol (free ribosomes) and envelope (bound ribosomes)
Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic
functions
endoplasmic reticulum (ER)
- accounts for
more than half of the total membrane in many in eukaryotic cells
smooth ER - which lacks ribosomes (lipids) Detoxifies drugs and poisons
rough ER- whose surface is studded with
ribosomes
Has bound ribosomes, which secrete
glycoproteins
(proteins + carbohydrates)
Distributes
transport vesicles
- secretory proteins
surrounded by membranes
Concept 6.5: Mitochondria and chloroplasts change energy from one form to another.
Mitochondria
-are the sites of cellular respiration, generate ATP
smooth outer membrane and an inner
membrane folded into
cristae
mitochondrial matrix
- metabolic steps of cellular respiration are
catalyzed in the mitochondrial matrix
Chloroplasts
- ound in plants and algae, are the
sites of photosynthesis
Mitochondria and chloroplasts have similarities with
bacteria -
endosymbiont theory
= early ancestor of eukaryotes
engulfed, an oxygen-using nonphotosynthetic
prokaryotic cell
endomembrane system
- has
Nuclear envelope
– Endoplasmic reticulum
– Golgi apparatus
Shipping and Receivingof flattened
membranous sacs called cisternae
Center ,
Golgi apparatus
-
–
Lysosomes
- is a membranous sac of hydrolytic
enzymes that can digest macromolecules
phagocytosis
- can engulf by cells , this forms a food vacuole
–
Vacuoles
- are large vesicles derived from the ER
and Golgi apparatus ,
food vacuoles
= formed by phagocytosis ,
Contractile vacuoles
( pumps excess water out of cells )
Central vacuoles
this contains solution called sap.
– Plasma membrane
These components are either continuous or
connected via transfer by
vesicles
chloroplast
- Capture of Light Energy , Chloroplasts contain the green pigment chlorophyll = The chloroplast is one of a group of plant organelles, called
plastids
peroxisomes
- are specialized metabolic
compartments bounded by a single membrane
functions - Some use oxygen to break fatty acids into smaller
molecules, eventually used for fuel for respiration
are specialized metabolic
compartments bounded by a single membrane
Roles of the Cytoskeleton
-
Support and Motility
cytoskeleton
-helps to support the cell and
maintain its shape, interacts with
motor proteins
to produce cell motility
Microtubules are the thickest of the three
components of the cytoskeleton
microtubules
- re hollow rods about 25 nm in
diameter and about 200 nm to 25 microns long
functions - shaping the cell, guiding movement of organelles
structures - control the beating of flagella (tail like) and
cilia (hair like). microtubule-containing extensions that
project from some cells.
structures of cilia and flagella -
A basal body
that anchors the cilium or flagellum.
A motor protein called
dynein
, = which drives the
bending movements of a cilium or flagellum
In animal cells, microtubules grow out from a
centrosome
near the nucleus
In animal cells, the centrosome has a pair of
centrioles
- are small cylindrical structures found in most animal cells.
continue 6.4 concept
Microfilaments
- are solid rods about 7 nm in
diameter, built as a twisted double chain of
actin
subunits
actin
-A network of microfilaments helps support the cell’s
shape
They form a
cortex
-just inside the plasma
membrane to help support the cell’s shape
Microfilaments that function in cellular motility contain the protein
myosin
- tiny machine in cells that uses ATP (energy) to move along actin filaments and do work.
Cells crawl along a surface by extending
pseudopodia
(cellular extensions)
Cytoplasmic streaming
=in plant cells, is a circular
flow of cytoplasm within cells.
Intermediate filaments-
- range in diameter from
8 to 12 nanometers,
Concept 6.7: Extracellular components
cell wall
-is an extracellular structure that
distinguishes ......plant cells from animal cells
Middle lamella: Thin layer between primary walls,
containing polysaccharides called pectins
Secondary cell wall
-Added between
the plasma membrane and the primary cell wall
Primary cell wall
- Relatively thin and flexible
concept 6.7
The Extracellular Matrix (ECM) of Animal Cells
extracellular matrix (ECM)
- Animal cells lack cell walls but are covered
made up of glycoproteins -
collagen
,
proteoglycans
, and
fibronectin
bind to receptors proteins - he plasma membrane called
integrins
cell junctions
-Neighboring cells in tissues , organs, or organ
systems often adhere, interact,and communicate
through direct physical contact
Plasmodesmata
-are channels that connect plant
cells
Tight Junctions,
- membranes of neighboring cells
are pressed together
Desmosomes
- (anchoring junctions)fasten cells
together into strong sheets
gap junction
- (communicating junctions) provide
cytoplasmic channels between adjacent cells
