Transcript The cell - inetTeacher.com

The cell
Cell theory
The cell is the smallest unit of life
All living things are made up of 1 or more cells
Cells come from pre-existing cells
Science and technology evolve together
microscope
Microscopic exam
Light microscope = light passes through lens to maginfy object
Resolution = ability to distinguish between two points clearly
Two types of cells
Prokaryotes (pre cells)
Domains bacteria and archaea
Kingdom Monera
Eukaryotes (true cells)
Domain Eukarya
Kingdoms
protista
fungi
plantae
animalia
Most cells same size
Allows for > surface area / volume
Prokaryotes
Domains bacteria and archeae
Kingdom Monera
Bacteria and cyanobacteria (blue-green algae)
Smallest cells
No membrane bound organelles
NO NUCLEUS
Cell walls as well as cell membranes
Eukaryotes
ALL other living things
Domain Eukarya
Kingdon Protista, Fungi, Plantae, Animalia
Highly complex and organized
Membrane bound organelles distribute
‘division of labor’
DNA in a nucleus
Plant cell
Cell wall
Large central vacuole
chloroplasts
vs.
animal cell
centrioles
Non membrane organelles
In BOTH prokaryotes and eukaryotes
CELL MEMBRANE
(plasma membrane)
Separates inside of cell from outside of cell
Selectively permeable
Phospholipid bilayer
Amphipathic (hydrophobic and
hydrophillic parts)
Hydrophyllic phosphorus ‘heads’
Hydrophobic lipid ‘tails’
(early formation of micells)
Cell membrane
Fluid mosaic model
Phospholipid bilayer not ‘locked’ in place
Phospholipids may move laterally or flip flop
Cholesterol
Imbedded in phospholipid bilayer to help
Stabilize fluidity and
Prevent solidification in lower temperatures
Cell membrane
Fluid mosaic model
Transmembrane proteins within phospholipid bilayer
Why proteins?
Proteins (in addition to cholesterol) help
stabilize fluidity of phospholipid bilayer
Act as markers for cell identification
Selective control of what enters/exits cell
diffusion
Small uncharged particles enter/exit a cell via diffusion
Movement is down a concentration [ ] gradient
diffusion
From area of  [ ] to an area of  [ ]
Movement via diffusion is passive transport
DOES NOT REQUIRE ENERGY
Osmosis = diffusion of water through a
semipermeable membrane
Water moves towards side with a lower water [ ]
aquaporins
osmosis
Hypertonic solution
Solution has higher concentration of solutes
Water diffuses out of cell
Hypotonic solution
Solution has lower concentration of solutes
Water diffuses into cell
Osmosis in plant and animal cells
In hypotonic solutions
Plant cells become turgid due to osmosis
Animals cells lyse
In hypertonic solutions
Plant cells become flaccid due to osmosis
Plasmolysis = cell membrane separates from
cell wall causing cell death
Animals cells crenated
Cell membrane proteins
Peripheral proteins (not embedded in lipid bilayer)
Integral proteins (embedded in lipid bilayer)
May be transmember proteins
Transport proteins
Move large or charged particles down a concentration gradient
= facilitated diffusion (passive transport)
Passive transport (facilitated diffusion)
DOES NOT REQUIRE ENERGY
Gated channels allow diffusion of specific solutes (ie. Na
Stimulated to open by electrical or chemical stimulus
more transport proteins
Membrane proteins may move charged or large particles
Across the phospholipid bilayer AGAINST the
Concentration gradient.
Active transport REQUIRES ENERGY
From area of  [ ]  [ ]
Sodium potassium pump
Membrane potential
Inside of cell has slightly
negative charge
Outside of cell has slightly
positive charge
Electrochemical gradient
drives transport of ions
across cell membranes
Electrogenic pump = protein that
generates voltage as it transports
substances across the membrane
Na / K pump
H+ pump
Some proteins are cotransporters
Specific particles ‘sneak in’ behind/with others
Enzymes and receptor proteins
enzymes
Sequential enzymes in
metabolic pathways may
be embedded in cell
membrane to enhance
efficiency of pathway
Receptor site
Binding site for
extracellular chemical
messenger (ligand)
Signal-transduction pathway
Extracellular 1st messenger
activates receptor protein
Receptor protein
relay protein
Relay protein stimulates
effector protein (an enzyme)
Enzyme product =
2nd messenger
2nd messenger triggers
metabolic or structural
response within cell
Endocytosis / exocytosis
3 types of endocytosis
Phagocytosis
Pseudopods wrap around particles
to form vacuoles of ‘food’
Pinocytosis
Psuedopods enguf extracellular fluid
Receptor mediated endocytosis
Ligands stimulate receptor proteins on cell membrane
to engulf extracellular particles via endocytosis
(LDL cholesterol)
Exocytosis = cell products exported from cell via
vacuoles and endomombrane system
junction proteins
Intercellular junctions
Join membranes of adjacent cells together
In animals:
Tight junctions
Cell membranes from neighboring
Cells are fused together
Forms a seal between
Cells. Ie epithelial cells
Desmosomes
Anchoring junctions.
Hold cells together In sheets.
Ie epithelial cells
Gap junctions Communicating junctions. Provide for
Cytoplasmic channels between cells.
Plant cells
Plasmodesmata = channels between plant cell walls and membranes
Cell-cell recognition
Glycoproteins identify cells to other cells
Immune system
Anchor proteins
integrins
Attach to cytoskeleton and ECM (extracellular matrix)
Bound to actin or other cytoskeleton parts.
Maintain cell shape .
Fix member proteins
in place.
Attach to ECM to
coordinate intracellular
and extracellular changes
ECM
Glycoproteins (i.e. collagen, proteoglycans, integrins)
secreted by cell.
Provide anchorage and support for cells.
Influence cells in embryonic development
Control activity of genes in nucleus???
Cell wall
Found in plants, fungi, bacteria and some protista but
NOT in animal cells
Plant cell walls made of cellulose
Primary cell wall secreted by young plant cells
Middle lamella = pectins between cell walls of 2 cells
‘glues’ 2 cells together
Secondary cell wall secreted by some plants (in many layers)
Plasmodesmata = openings between cell walls of adjacent cells
Fungi cell wall made of chitin
Bacterial cell wall made of peptidoglycan
Ribosomes and cytoplasm
ribosomes
Protein complexes and RNA involved
in protein synthesis
In cytoplasm of prokaryotes and eukaryotes
On the surface of rough ER in eukaryotes
cytoplasm
Region between cell membrane and nucleus
in eukaryotes;
Between nucleoid region and cell membrane
in prokaryotes
Cytosol = semi-fluid, gel like substance (same)
cytoskeleton
Nucleoid region = area of DNA concentration
in prokaryotes
Network of protein fibers in cytoplasm
cytoskeleton
Network of protein fibers
in cytoplasm
Maintain cell shape
Anchor organelles
Provide for MOVEMENT
microfilaments
Actin
Intermediate filaments
microtubules
Hollow tubes from -tubulin and -tubulin dimer
Radiate from centrosome near nucleus (eukaryotes)
Centrioles made of 9 sets of triple microtubules.
Involved in cell division (animal cells)
Flagella and cilia
For movement
Cilia are short and numerous
Flagella are long and few
oars
tail
Animals and protists
Animals, protists
some plant sperm
Specialized arrangement of microtubules allow
flagella and cilia to move
9 doublets of microtubules in a ring with
2 microtubules in the center = ‘9 + 2’ pattern
Basal body structured as a centriole anchors
cilia/flagella to cell
Dynein = motor molecule (protein) between microtubule
doublets that uses ATP To move flagella/cilia
‘walking’
Movement within cells
Microfilaments actin and myosin
slide past one another
when a muscle cell contracts
Microfilaments actin and myosin
involved in amoeboid movement
(use of pseudopods)
Microfilaments actin and myosin
involved in
cytoplasmic streaming
cytoplasmic streaming Sordaria sp
Intermediate filaments more permanent for structure.
Diverse class of proteins in keratin protein family.