Download Lecture02_Su2010_A Tour of the Cell

1
Cells are the basic unit of structure
and function
The lowest level of structure that
can perform all activities required
for life


Reproduction
Metabolic activity
Cell Theory:
 All organisms are made of cells
 All cells arise from other cells
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Fig. 6.2
3
Cell Fractionation
Fig. 6.4
Fig. 6.5
4
 Limits
to size
 Surface area to
volume ratio
Fig. 6.8
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Prokaryotes
Eukaryotes
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Prokaryote
What
differences do
you see?
Eukaryote
Fig. 6.6
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 Plasma
membrane
 Cytosol
 Chromosomes
 Ribosomes
Fig. 6.7
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Present in all cell types
Function:
 Separates
the internal from the external
environment
 Regulate chemical exchanges within the
environment

Chemical reactions more efficient
 Dynamic
selective barrier
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Prokaryotes
 No nucleus

Eukaryotes
 Nucleus
Nucleoid region
Simple
 No membrane bound
organelles


Complex
 Membrane bound
organelles


Smaller (1-5 nm)
 Evolutionarily older

(DNA in a membrane-bound
region)
Organelle – a structure with a
specified function w/i a cell
Larger (10-100 nm)
 Evolutionarily younger

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See Fig. 27.2
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Evolution of the
endomembrane
system
All the membrane bound
organelles within a cell,
except for mitochondria
and chloroplasts
 Inward folding of plasma
membrane formed
nuclear envelope,
organelles

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Animal cell structures:
 Plasma membrane
 Nucleus
 Cytosol
 Ribosomes
 Endoplasmic reticulum
 Golgi apparatus
 Mitochondria
 Cytoskeleton
 Vacuoles
 Peroxisome
Not typically found in plants:
 Centrosome
 Lysosomes
 Flagella
See Fig. 6.9 –Animal cell
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Intestinal (smooth) muscle
cells
Cheek cells (400X)
Cardiac muscle cells
Brain cells (astrocytes)
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Plant cell structures:
 Plasma membrane
 Nucleus
 Cytosol
 Ribosomes
 Endoplasmic reticulum
 Golgi apparatus
 Mitochondria
 Cytoskeleton
 Peroxisome
Not found in animals:
 Cell Wall w/plasmodesmata
 Plastids (Chloroplasts,
Amyloplasts, Chromoplasts)
 Central vacuole
Fig. 4.6 –Animal cell
See Fig. 6.9 – Plant cell
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Leaf cells
Root cell w/amyloplasts
Plant cell
Leaf cells w/chloroplasts
Leaf epidermal (surface)
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Cytoplasm
 Area between the
nucleus and the
plasma membrane
Cytosol
 Fluid of the
cytoplasm
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Functions
 Store genes on chromosomes
 Regulate gene expression
 Transport regulatory factors and gene
products
 Produce messages (mRNA) that code
for proteins
 Produce the components of ribosomes
 Replication of genetic material
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Nuclear envelope
 Double membrane
Pore complexes
 Gatekeepers
Nuclear lamina
 Protein filaments
 Maintains shape
of nucleus
Fig. 6.10
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Chromosomes
 Discrete units of DNA
 Chromatin - Association of
DNA molecules and proteins
 One chromatin = one
chromosome
Nucleolus
 Ball-like mass of fibers &
granules
 Produces ribosomal RNA
(rRNA)
 Assembles components of
ribosomes
Fig. 6.10
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Complex of proteins & rRNA
Function: Protein synthesis
 Ribosome parts are made in nucleus by
nucleolus
 Parts travel out of nucleus, into cytoplasm
Two types:
 Bound ribosome


Bound to endoplasmic reticulum (ER)
Make proteins for membranes or exportation from cell
 Free

ribosomes
make proteins that stay
in cytosol
Fig. 6.11
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DNA – Protein production
1.
mRNA synthesis
2.
mRNA travels to
ribosomes
3.
Ribosomes use mRNA
to synthesize proteins
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Functions:
 Manufacturing and distributing cellular products
 Detoxification of poisons
Contains:
 Nuclear envelope
 The endoplasmic reticulum (ER)
 The Golgi apparatus
 Lysosomes & Vacuoles
 Plasma membrane not Endo, but related
Membranes unique in structure & function
Membranes dynamic
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Function: manufacturing of many cellular
products
 Large – more than ½ of all membrane in cell
 Continuous with nuclear envelope
 Cisternae


Membranous tubules & sacs
Cisternal space
Fig. 6.12
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Smooth ER
 No ribosomes
Functions:
 Lipid production

E.g., steroids, phospholipds
 Metabolism
of
carbohydrates
 Detoxification of drugs
 Calcium ion storage
Fig. 6.12
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Rough ER
 Ribosomes bound to ER
Function:
 Produces secretory
proteins


Glycoproteins
Transport vesicles
 Produces
membrane
proteins
 Makes phospholipids for
membrane
Fig. 6.12
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Function:
 Receives products from ER
 Modifies products
 Stores products
 Delivers products


Other parts of cell
Other cells (secretion/exportation)
 Manufactures
Fig. 6.13
some macromolecules
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Cis face – receiving
Trans face – shipping

Products identified and “tagged”
e.g., phosphate groups added to
products
e.g., recognition proteins on
transport vesicles
Cisternal maturation model
Dynamic process
 Cisturnae move from cis to trans
 Products modified as cisturnae
move

Fig. 6.13
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Lysosome
 Membrane bound sac of hydrolytic
enzymes
 Keeps enzymes from rest of cell
 Higher pH in lysosome optimal for
lysosomal enzymes
Production:
 ER makes hydrolytic enzymes &
lysosomal membranes
 Transported to GA for processing
 Some bud directly from GA
Fig. 6.14
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Function:
 Nutrient digestion

Part of phagocytosis
 Destroy
harmful bacteria
 Recycle damaged organelles

Autophagy
 Embryonic
development
Fig. 6.14
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Membrane bound sacs that form (“bud”) from the
ER, Golgi apparatus or plasma membrane.
Function:
 Contain material
 Food vacuole
 Water pumps
 Contractile vacuoles
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Central Vacuole
 Large – can occupy 90% volume
of cell
 Coalescence of many smaller
vacuoles from ER, GA
 Single membrane
 Water, salts, other molecules
inside
 Few enzymes
Function
 Storage
 Growth of cell
 Protection
 Helps concentrate enzymes in
rest of cell
Fig 6.15
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Fig. 6.16
33
Function:
 Cellular respiration


Converts carbon compounds into ATP
ATP (adenosine triphosphate) –energy for cellular work
Found in most eukaryotic cells
 Not part of endomembrane systems

Contains its own DNA
 Has a double
membrane



Membrane proteins
made by free
ribosomes
Cristae – infoldings of
inner membrane
Fig. 6.17
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Function: Photosynthesis
 Creates carbon compounds using energy from the sun
 Contain chlorophyll a & other pigments
 Not part of endomembrane systems
 Contains its own DNA
 Has a double membrane
 Thylakoids – flattened interconnected stacks
 Granum – stacks of thylakoids
 Stroma – fluid outside thylakoids

Intermembrane
space

Stroma

Thylakoid space
Fig. 6.18
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Plastid
 Organelle with 2 membranes
 Has its own DNA & RNA
 Found in plants, some protists
Three main types
 Chloroplasts
 Chromoplasts


Function: Stores lipid soluble pigments
Usually colored
 Amyloplasts

Function: Stores starch
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 Specialized
membrane compartment
 Single membrane
Function:
 Contains enzymes that transfer hydrogen to
oxygen, producing hydrogen peroxide
 Breaks down fatty acids
 Detoxify
Composed of:
 Proteins from cytosol
 Lipids from ER
 Lipids synthesized in
Peroxisome
Fig. 6.19
1
Network of fibers extending
throughout the cytoplasm
Three types:
 Microtubules
 Microfilaments
 Intermediate filaments
Fig. 6.20
2
Microtubules
 Hollow rods
 Protein: tubulin
 Largest diameter (25 nm)
 Actively assembled & disassembled
 Function

Maintain cell shape




Compression-resisting
Cell division (centrioles)
Tracks for organelle movement
Cell motility (cilia & flagella)
Table 6.3
Fig. 6.21
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Microtubular containing
extensions from a cell
Flagella
 Typically one or two, long
 Undulating motion
Cilia
 Typically many, short
 Back & forth motion
Functions:
 Mobility of cell
 Movement of fluid past a cell
 Attachment (some cilia)
 Signal-receiving (specialized
cilia)
Fig. 6.23
4
Microfilaments
 Solid rods
 Protein: actin
 Smallest diameter (7 nm)
 Actively assembled &
disassembled
 Function

Maintain cell shape






Tension bearing
Change cell shape
Cell motility (pseudopodia)
Cell division (cleavage furrow)
Muscle contraction
Cytoplasmic streaming
Table 6.3
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Intermediate filaments
 Supercoiled cables
 Proteins: keratin family
 Intermediate & variable
diameter (8-12 nm)
 Permanent structures
 Function:



Maintain cell shape (tension
bearing)
Anchor nucleus, some organelles
Forms nuclear lamina
Table 6.3
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 Collagen

Glycoproteins (protein +
carbohydrate)
 Proteoglycan

complex
Core protein with many
carbohydrate chains
Fig. 6.30
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 Fibronectin

Attaches ECM to integrins
 Integrins

Cell surface receptor proteins
Fig. 6.30
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 Tight


junctions
Continuous seal around
cell
Prevent fluid leakage
 Desmosomes

Attach cells together
 Gap

Junctions
Cytoplasmic channels
 Proteins
Fig. 6.32
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Cell walls
 A protective layer
external to the plasma
membrane
 Plants (also bacteria,
archaea, fungi, some
protists)
Functions:
 Protection
 Maintain shape
 Prevent excessive water
uptake
Fig. 6.28
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 Matrix
of cellulose, other polysaccharides &
proteins
 What is cellulose?
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Function
 Energy source


used in cellular respiration to create ATP
What are some sources of carbohydrates?
 Carbon
skeleton “building block” for other
organic molecules
 Cell identity
 Fibrous structural material

Cellulose, chitin, peptidoglycan
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Monomer
 small molecule
Polymer
 large molecule made up
of many smaller
monomers
Macromolecules
 “Big molecule”
Synthesis & Breakdown of
Polymers
 Dehydration reaction
 Hydrolysis
Fig. 5.2
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Monosaccharides
 Simple sugar (CH2O)

E.g., glucose, fructose
Disaccharides
 Double sugar (complex carbohydrate)

E.g., sucrose, maltose, lactose
Polysaccharides
 Complex carbohydrates
 Long chains of sugar

E.g., glycogen, starch, cellulose, chitin
 Storage
molecules
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 Structural
polysaccharide
 Polymer of glucose
 Most abundant
organic compound on
earth
 Not digestible by most
organisms

Beta glucose
 Unbranched
straight

Fig. 5.8
&
Forms microfibrils
Fig. 5.7
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Plasmodesmata
 Channels between adjacent cells
 Cytosol is continuous between connected cells
Fig. 6.31