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.

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