The cell The cell is the smallest unit of life Science and technology evolve together microscope...
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Transcript of The cell The cell is the smallest unit of life Science and technology evolve together microscope...
The cell
The cell is the smallest unit of life
Science and technology evolve together
microscope
Cell theory
All living things are made up of 1 or more cells
Cells come from pre-existing cells
Microscopic examLight microscope = light passes through lens to maginfy object
Resolution = ability to distinguish between two points clearly
Two types of cellsProkaryotes (pre cells)
Eukaryotes (true cells)
Domains bacteria and archaea
Kingdom Monera
Domain Eukarya
Kingdoms protistafungiplantaeanimalia
Most cells same size
Allows for > surface area / volume
Prokaryotes
Domains bacteria and archeaeKingdom Monera
Bacteria and cyanobacteria (blue-green algae)
Smallest cells
No membrane bound organelles
NO NUCLEUS
Cell walls as well as cell membranes
EukaryotesALL other living things
Highly complex and organized
Membrane bound organelles distribute ‘division of labor’
Domain EukaryaKingdon Protista, Fungi, Plantae, Animalia
DNA in a nucleus
Plant cell vs. animal cell
Cell wallLarge central vacuolechloroplasts
centrioles
Non membrane organellesIn BOTH prokaryotes and eukaryotes
CELL MEMBRANE (plasma membrane)
Separates inside of cell from outside of cell
Phospholipid bilayer
Hydrophyllic phosphorus ‘heads’
Hydrophobic lipid ‘tails’
Amphipathic (hydrophobic and hydrophillic parts)
Selectively permeable
(early formation of micells)
Cell membraneFluid mosaic model
Phospholipid bilayer not ‘locked’ in place
Phospholipids may move laterally or flip flop
Cholesterol
Imbedded in phospholipid bilayer to helpStabilize fluidity andPrevent solidification in lower temperatures
Cell membrane
Fluid mosaic model
Transmembrane proteins within phospholipid bilayer
Why proteins?
Selective control of what enters/exits cell
Proteins (in addition to cholesterol) help stabilize fluidity of phospholipid bilayer
Act as markers for cell identification
diffusion
Small uncharged particles enter/exit a cell via diffusion
Movement is down a concentration [ ] gradient
From area of [ ] to an area of [ ]
Movement via diffusion is passive transportDOES NOT REQUIRE ENERGY
diffusion
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
In hypertonic solutions
Plant cells become flaccid due to osmosis
Plasmolysis = cell membrane separates from cell wall causing cell death
Animals cells lyse
Animals cells crenated
Cell membrane proteinsPeripheral proteins (not embedded in lipid bilayer)
Integral proteins (embedded in lipid bilayer)
May be transmember proteins
Move large or charged particles down a concentration gradient
= facilitated diffusion (passive transport)
Passive transport (facilitated diffusion)
DOES NOT REQUIRE ENERGY
Transport proteins
Gated channels allow diffusion of specific solutes (ie. Na+)
Stimulated to open by electrical or chemical stimulus
Active transport REQUIRES ENERGY
Membrane proteins may move charged or large particlesAcross the phospholipid bilayer AGAINST the Concentration gradient.
From area of [ ] [ ] Sodium potassium pump
more transport proteins
Membrane potentialInside 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)
Extracellular 1st messenger activates receptor protein
Receptor protein relay protein
Relay protein stimulates effector protein (an enzyme)
2nd messenger triggers metabolic or structural response within cell
Enzyme product = 2nd messenger
Signal-transduction pathway
Endocytosis / exocytosis
3 types of endocytosis
Phagocytosis
Pinocytosis
Receptor mediated endocytosis
Pseudopods wrap around particles to form vacuoles of ‘food’
Psuedopods enguf extracellular fluid
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
Desmosomes
Gap junctions
Cell membranes from neighboring Cells are fused together Forms a seal between Cells. Ie epithelial cells
Anchoring junctions. Hold cells together In sheets. Ie epithelial cells
Communicating junctions. Provide forCytoplasmic channels between cells.
Plant cellsPlasmodesmata = channels between plant cell walls and membranes
Cell-cell recognitionGlycoproteins identify cells to other cells
Immune system
Anchor proteins
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
integrins
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 wallFound 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)
Fungi cell wall made of chitin
Bacterial cell wall made of peptidoglycan
Plasmodesmata = openings between cell walls of adjacent cells
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 Network of protein fibers in cytoplasm
Nucleoid region = area of DNA concentration
in prokaryotes
cytoskeletonNetwork 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
Centrioles made of 9 sets of triple microtubules.Involved in cell division (animal cells)
Radiate from centrosome near nucleus (eukaryotes)
Flagella and ciliaFor movement
Specialized arrangement of microtubules allow flagella and cilia to move
Cilia are short and numerous oars
Flagella are long and few tail
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
9 doublets of microtubules in a ring with 2 microtubules in the center = ‘9 + 2’ pattern
‘walking’
Animals and protists
Animals, protists some plant sperm
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
Intermediate filaments more permanent for structure.Diverse class of proteins in keratin protein family.
cytoplasmic streaming Sordaria sp