Download AP Biology - Cell Structure and Function

A Tour of
the Cell
Animals & Plants
Chapter Five
Cell Study
O Light microscope – up to
0.2 m; magnify well up
to 1000x; not enough
for many organelles
Cell Study
O Electron microscope – up to 2nm
(hundredfold improvement) –
uses electron beam
O Specimens must be “prepared”
first
O Two types
Cell Study
O Scanning Electron Microscope
(SEM) – used for surface study –
appears 3-D
O Cilia in the
windpipe of a
rabbit
Cell Study
O Transmission Electron
Microscope (TEM) – internal
structure of cells
O Uses magnets to bend electrons
as they pass through
O Cells from
windpipe of a rabbit
Cellular Preparation
O Cell fractionation – take cells apart
& separate organelles for study
O Ultracentrifuge – 130,000 rpm
O Break cells apart
(homogenization),
then separate
organelles (differential
centrifugation)
Cellular Preparation
Cell Types
O Prokaryotic – no nucleus
O Bacteria & archaea
O DNA in region called the nucleoid (has
no membrane)
O Have plasma membrane, chromosomes,
ribosomes, cytosol
Cell Types
Cell Types
O Eukaryotic – have membrane-bound
organelles suspended in cytosol, including
a definite nucleus
(cytosol + organelles = cytoplasm)
O Eukaryotic = 10-100 m
O Prokaryotic = 1-10 m
Eukaryotic Cells &
Organelles
Eukaryotic Cells &
Organelles
Eukaryotic Cells &
Organelles
O Plasma Membrane
O Selective barrier
Eukaryotic Cells &
Organelles
O Membrane of phospholipids,
proteins, glycoproteins
Eukaryotic Cells &
Organelles
O Nucleus
O Contains most genes
O Surrounded by nuclear envelope –
double lipid bilayer membrane with
pores
O Inner nuclear side lined with nuclear
lamina (protein filaments for structure)
Eukaryotic Cells &
Organelles
O Inside, DNA is as fibrous chromatin
O Will condense into chromosomes
during division
O Nucleolus
O Inside nucleus
O Ribosomal RNA (rRNA) made here &
assembled to make ribosomes in
cytoplasm
Eukaryotic Cells & Organelles
Eukaryotic Cells &
O Ribosomes Organelles
O Two subunits made of ribosomal RNA &
protein
O Protein synthesis
O Free or on ER (structurally identical)
O Free make proteins that function in
cytosol
O Bound make proteins that are inserted
into membranes, for packaging within
other organelles, or exported
Eukaryotic Cells & Organelles
Eukaryotic Cells &
Organelles
O ER (Endoplasmic reticulum)
O Network of tubules & sacs –
cisternae
O Internal space – cisternal space
O Two types
Eukaryotic Cells & Organelles
Eukaryotic Cells &
Organelles
O Smooth ER
O No outer ribosomes
O Synthesis of lipids
O Carbohydrate metabolism
Eukaryotic Cells &
Organelles
O Detoxify drugs & poisons,
esp. in liver
O Muscle cells – Smooth ER pumps
calcium ions from cytosol to cisternal space –
when muscle is stimulated, Ca rushes back over
– triggers
muscle contraction
Eukaryotic Cells
& Organelles
Eukaryotic Cells &
Organelles
O Rough ER
O Produce secretory proteins
O Protein is made, threads
through pore into cisternal
space, folds into proper shape
O Most are glycoproteins
Eukaryotic Cells &
Organelles
O Secretory proteins leave ER wrapped
in membranes of transport vesicles
O Vesicles in transit throughout cell
O Rough ER also makes membranes
for endomembrane system
(nuclear envelope, ER, Golgi,
lysosomes, vacuoles, plasma
membrane)
Eukaryotic Cells &
Organelles
O Golgi Apparatus
O Manufacture, store, sort, ship
products of ER
O Flattened sacs (cisternae)
O Two faces – cis (receive
transport vesicles from ER)
and trans (vesicles pinch off to
other places)
 Products
move from
cis to trans
- modified
& refined
along the
way
Eukaryotic Cells & Organelles
Eukaryotic Cells &
Organelles
O Lysosomes
O Hydrolytic enzymes  digestion
O pH 5
O Enzymes made in rough ER, put through
Golgi, then into lysosomes
O Digest by fusing with food vacuole,
bacteria, invaders
Eukaryotic Cells &
Organelles
O Autophagy – recycle own cell’s
materials (like old organelles)
O Organismal advantage – removal of webbed
hands during embryonic development - tadpole
has tail destroyed as it turns into a frog
Eukaryotic Cells &
Organelles
O If lysosomes can’t digest – lack
of functioning enzyme – cell
gets filled with indigestible
materials
O Tay-Sachs
Eukaryotic Cells & Organelles
Eukaryotic Cells &
Organelles
O Vacuoles
O Food, contractile, central
O Central vacuole – in plants
O Enclosed by tonoplast
O Reserves of proteins, inorganic ions,
metabolic wastes, pigments, animal
warning system
O Role in growth
Eukaryotic Cells &
Organelles
O Endomembrane System
(organelles that are
underlined)
Eukaryotic Cells &
Organelles
O Mitochondria – cellular respiration
O Food  ATP
O Semiautonomous organelle
O Two layers – each phospholipid
bilayer
O Outer membrane - smooth
O Inner is convoluted – cristae
Eukaryotic Cells &
Organelles
O Separates into two
compartments
O Intermembrane space –
between outer and inner
membranes
O Mitochondrial matrix – inside
O Contains DNA, enzymes,
ribosomes
Eukaryotic Cells &
Organelles
O Chloroplasts
O Site of photosynthesis
O Two membranes
O Inside are thylakoids (sacs) –
each is called a granum
O Fluid outside thylakoid – stroma
(contain DNA, ribosomes,
enzymes)
Eukaryotic Cells &
Organelles
O Peroxisomes
O Contain enzymes that transfer
hydrogen to oxygen, making
H2O2 (hydrogen peroxide)
O Organelle helps detoxification,
fatty acid hydrolysis
O Then converts H2O2 to H2O
Cytoskeleton
O Network of fibers
O Support & shape
O Anchorage for organelles & enzymes
Cytoskeleton
O Cell motility
O Interaction with motor molecules
(proteins)
O Movement of cilia & flagella –
cytoskeleton components can slide past
each other
O Contraction of muscle cells
O Organelles can move within cell
Cytoskeleton
O Three
fibers
Cell Walls
O Protects, shape, prevents
excessive water uptake
O Cellulose embedded in
protein/polysaccharide matrix
O As young plant, makes primary
cell wall
Cell Walls
O Between walls of adjacent cells –middle
lamella (rich in pectins – thick)
O Cell stops growing – makes thicker
secondary
cell wall
Extracellular Matrix
(ECM)
O Surface of animal cells
O Glycoproteins (mostly collagen)
embedded in proteoglycan
network
Extracellular Matrix
(ECM)
O Cells attached to ECM by
fibronectins (glycoprotein)
Bind to integrins (receptor
molecules on plasma membrane)
Attach ECM to plasma membrane
to coordinate any changes
O ECM can coordinate cell’s behavior
Intercellular Junctions
O Plasmodesmata – perforations in plant cell
walls
O Allows cytosol, water, proteins, RNA,
small solutes to pass between
O Plasma
membrane
lines
channel
Intercellular Junctions
O
Animal cells:
1. Tight junctions –
membranes of neighboring
cells are fused – prevent EC
fluid leakage
2. Desmosomes (anchoring
junctions) – fastens cells
into strong sheets like rivets
Intercellular Junctions
3. Gap junctions (communicating junctions)
– provides cytoplasmic channel between
adjacent cells
O Allows small ions & molecules to pass
O Flow of ions coordinates cell
contractions