Download Chapter 4 Cell Structure

Chapter 4
Cell Structure
I. Cell Theory (4.1)
• Hooke first observed cells 1665
• Leeuwenhoek first observed live
cells.
• 1838-9 Schleiden and Schwann.
A. Cell theory is the unifying foundation
of cell biology
1. All organisms are made of cells.
2. Cells are the basic units of life.
3. Cells are made through division of
preexisting cells.
B. Cell size is limited
1. Surface area – to – volume ratio: molecules
can more through the membrane quickly if
they are close in small cells;
surface area = r2 but volume = r3.
C. Microscopes allow visualization
of cells and components
1. Resolution: clarity; minimum distance 2
can be apart and still seen as 2 separate
points.
2. Types of Microscopes
1. Light: uses light and 2 lenses
2. Compound: uses multiple lenses
1. Electron: electron beams
2. Transmission electron: see through
specimen
3. Scanning electron: look at surface of
specimen
3. Using stains to view cell structure
• Stains: cause some structures to become
darker for contrast helping resolution.
D. All cells exhibit basic structural
similarities
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Nucleus or nucleoid
Cytoplasm
Ribsomes
Plasma membrane
1. Centrally located genetic material
i. Prokaryotes: simple organisms, most
genetic material is circular DNA
ii. Nucleoid: area near center of cell where
genetic material found (no membrane
separating it)
iii. Eukaryote: complex organisms, contain
nucleus and organelles.
iv. Nucleus: organelles w/ DNA
2. Cytoplasm
1. Cytoplasm: jelly-like matrix that fills inside
of cell
2. Organelle: membrane-bound structure w/
specific job
3. Cytosol: part of cytoplasm with organic
molecules (like proteins, sugars) and ions
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Cytoplasm
3. Plasma Membrane
i.
Phospholipid bilayer: 2 layers of lipids
around cell, separate contents from
surroundings
ii. Transport proteins: help move material
across membrane
iii. Receptor proteins: help cells communicate,
send and receive messages
II. Prokaryotic Cells (4.2)
• No nucleus
• No organelles
A. Prokaryotic cells have relatively
simple organization
1. Cell wall: provides structure; outside of
cell membrane and cytoplasm
2. Ribosomes: carry out protein synthesis
3. 2 types: archaea and bacteria
4. Cell membrane can take on other jobs
5. Functions as 1 whole unit
B. Bacterial cell walls consist of
peptidoglycan
1. Peptidoglycan: made of a carbohydrate
that provides structure, protection, and
water balance
2. Gram-positive: group of bacteria w/ single
layer of cell wall that holds violet dye
3. Gram-negative: group of bacteria with
multilayer cell wall that does NOT hold
violet dye.
C. Archaea lack peptidoglycan
D. Some prokaryotes move by means
of rotating flagella
1. Flagella: threadlike structures made of
protein fibers used for locomotion
III. Eukaryotic Cells (4.3)
1. Endomembrane system: membrane bound
sections carrying out chemical processes
2. Central vacuole: large organelle that stores
proteins, pigments, and waste
3. Vesicles: small transport sacs
4. Chromosomes: DNA tightly pack around
proteins
5. Cytoskeleton: proteins supporting the
shape and structure of a cell
A. The nucleus acts as the
information center
1. Nucleus: large organelle holding genetic
information
2. Nucleolus: area in nucleus synthesis of
ribosomal RNA
3. The nuclear envelope: membrane around
nucleus
i. nuclear pores: holes in nuclear
envelope that allow passage of RNA
and proteins
4. Chromatin: DNA wrapped around proteins
called histones to form chromosomes
i. chromatin
ii. nucleosomes
iii. histones
5. The nucleolus: Ribosomal subunit
manufacturing
i. Ribosomes are made of rRNA and protein.
ii. These parts are synthesized in the nucleolus.
B. Ribosomes are the cell’s protein
synthesis machinery
1. ribosomal RNA (rRNA): along with
proteins they form ribosomes which make
or synthesize proteins
2. messenger RNA (mRNA): carries info
from DNA to ribosome
3. transfer RNA (tRNA) : carries amino acids
to ribosomes
IV. The Endomembrane System (4.4)
1. Endoplasmic Reticulum (ER): phospholipid
bilayer w/ proteins makes this folded internal
membrane w/ channels.
2. Cisternal space/Lumen: inner region of ER
A. The Rough ER is a site of protein synthesis
1. Rough ER: Rough b/c it is covered w/
ribosomes. Makes proteins.
2. Glycoproteins: Proteins w/ short
carbohydrate chains.
B. Smooth ER has multiple roles
1. Smooth ER (SER):
network of enzymes
that synthesize
carbohydrates and
lipids.
Stores Ca2+
Modify foreign
substances so they
are less toxic, liver.
cells would have a
long SER
C. The Golgi apparatus sorts and
packages proteins
1. Golgi body: flattened stack of membranes
2. Golgi apparatus: collection of Golgi bodies
that collect, package and distribute
molecules sometimes from ER. Cis
entrance; leave through trans face in
vesicles. Finally it synthesizes the cell
wall.
3. Cisternae: stacked membrane that can
pinch off to form vesicles for transport.
D. Lysosomes contain digestive enzymes
1. Lysosomes: membrane bound digestive
vesicles that break down and recycle
proteins, lipids, nucleic acids and
carbohydrates.
1. Phagocytosis: Cells can take in large
molecules of food in vesicles which fuse
w/ lysosomes for digestion.
E. Microbodies: vesicles w/ enzymes
1. Peroxisomes: microbodies w/ digestive
and detoxifying enzymes that produce
and break down hydrogen peroxide and
remove electrons.
2. Glyoxysome: microbody found in plants
that convert fats to carbs.
F. Plants use vacuoles for storage
and water balance
1. Vacuoles: Stores useful molecules like
sugar, ions, pigments and water as well as
waste.
The large central vacuole in plants allows
the cell to contract and expand through
water channels.
Different types of vacuoles exist.
2. Tonoplast: membrane around vacuole that
contains water channels to maintain water
levels.
V. Mitochondria and Chloroplasts:
Cellular Generators
A. Mitochondria metabolize sugar to make ATP
1. Mitochondria: organelle involved in cellular
respiration. It has its own DNA. They can
divide to reproduce but this process is
dependent upon DNA in the nucleus.
2. Cristae: inner membrane of mitochondria
increasing surface area.
3. Matrix: solution in the interior of cristae
involved in respiration
4. Intermembrane space: outer compartment of
mitochondria.
5. ATP: energy storing molecule produced
during cell respiration
B. Chloroplasts use light to generate ATP and
sugars
1. Chloroplasts: organells that carry out
photosynthesis. They make their own food
thanks to Chlorophyll (green pigment).
Consist of membrane, grana and own DNA.
2. Grana: stacked thylakoids
3. Thylakoids: closed sections of membrane
containing photosynthetic pigments
4. Leucoplast: organelles that contain DNA but
have no pigment.
5. Amyloplast: Leucoplast that stores starch
(amylose)
6. Plastid: organelles that can reproduce and
carry out photosynthesis or serve as storage
C. Mitochondria and chloroplast
arose by endosymbiosis
Endosymbiosis
eukaryotes derived from one prokaryote
engulfing another
i.
Inner membrane of mitoch and chloropl
came from membrane of prokaryote, outer
membrane from plasma membrane or ER
of host.
ii. Mitoch are size of bacteria and inner
membrane similar to folded membrane of
bacteria.
iii. Ribosomes of mitoch and bacteria similar
iv. Mitoch and chloropl have circular DNA
like prokaryotes
v. Genomes of mitoch and chloropl similar to
bacteria
vi. Mitoch divide by fission like bacteria
VI. The Cytoskeleton: made of long protein fibers
3 types of fibers make
the cytoskeleton
1. Actin filaments: Actin
subunits link to create
long protein fibers made
of 2 protein chains
twisted together.
Responsible for
contractions, crawling,
pinching off, and cell
extensions.
2. Microtubules: tubulin subunits link to
make protein filaments form a tube shape.
Help in intracellular transport and
separation of chromosomes.
3. Intermediate filaments:
proteins overlapping,
twisted and bundled
together for strength.
Protein subunits include
vimentin for stability.
Examples of
intermediate filaments
are keratin found in our
hair and fingernails and
neurofilaments found in
nerve cells.
B. Centrosomes are microtubule-organizing
centers
1. Centrioles: organelles made of 9 triplets of
microtubules and involved in organization of
microtubules during cell division (animal cells
only). Make cytoskeletons, cilia and flagella.
2. Centrosome: area where pair of centrioles is
found.
C. The cytoskeleton helps move
materials within cells
• Thin actin filaments and thick microtubules
coordinate activities like cell division.
• Actin and myosin are proteins involved in
muscle movement.
• Anchors structures.
1. Molecular Motors
• Vesicle holding
material is bound to
a motor protein
(kinesin) that uses
ATP by a connector
protein (kinectin or
dynein).
• Microtubules act as
a rail road track for
these transport
vesicles.
VII. Extracellular Structures and
Cell Movement
A. Some cells crawl
• Actin filaments quickly polymerize extending
part of the plasma membrane forward.
• Myosin proteins contract pulling the rest of the
cell forward as well.
B. Flagella and cilia movement
1. 9 + 2 structure: 9 microtubule pairs
around 2 central microtubules
• Side arms are made of dynein, a protein
motor molecule that changes using ATP
2. Basal body: 9 triplets of microtubules
connected by proteins.
3. Cilia: short projections off a cell. There
are usually many cilia for movement.
They have a 9 + 2 arrangement of
microtubules.
C. Plant cell walls provide
protection and support
1. Primary walls: laid out when cell still
growing
2. Middle lamella: sticky substance to glue
cells together
3. Secondary walls: thick support and
protection
D. Animal cells secrete an
extracellular matrix
• Animal cells secrete glycoproteins,
elastins, and collagen to form an
extracellular matrix (ECM) around the cell.
• This ECM is bound to integrins which help
hold the cytoskeleton in place.
• The ECM provides support and strength.