Eukaryotic organism

Premedical IV

The size range of organisms

Light microscopes

• visible light is passed through the

specimen and glass lenses

• the resolution is limited by the

wavelength of the visible light

• magnification to 1000x the size

of the actual specimen

Resolving power - the minimum

distance two points, which can be

distiquished.

Electron microscope

– focused a beam (current) of electrons, have the

wavelength much shorter than visible light, 1 nm (0.1nm)

TEM transmission: the beam through a thin specimen -

ultrastructure

SEM scanning: the electron beam scans the surface of

the sample

• use the electromagnets instead of glass lenses

SEM

Light microscope

Eukaryotic cells

Muscle cardiac cells

fibroblast

blood

Eukaryotic cell

Cytoplasm = cytosol + organelles

The nucleus• Genes that control the eukaryotic

cells

• Nuclear envelope is a double

membrane, each membrane is

lipid bilayer with proteins

• perforation by pores

• chromatin – DNA, histons,

non-histon protein

• cell division – chromatin

condensate to chromosomes

• the nucleolus – synthesis of

ribosomes components

• The nucleus control protein synthesis by sending

molecular messengers in the form RNA – mRNA -

messenger - TRANSCRIPTION

• is synthesized in nucleus according the DNA

• in ribosomes is genetic information translate into the

primary structure of a specific protein - TRANSLATION

• free ribosomes – suspended in the cytosol, function of

protein in cytosol

• bound ribosomes are attached to outside membrane

network called the endoplazmatic reticulum;

make proteins destined into membrane and for export from

the cell (secretion)

Ribosomes

The endomembrane system

Nuclear envelope, endoplasmic reticulum, Golgi apparatus,

lysosoms, various kinds of vacuoles and plasma membrane

• ER consist of a network of

membranous tubules and sacs

called cisternae

• ER is continuous with nuclear

envelope

• Smooth ER - cytoplasmatic

surface lacks ribosomes

• Rough ER – ribosomes are

attached to the cytoplasmatic side

Function of smooth ER – synthesis of lipids (phospholipids,

steroids), metabolism of carbohydrates (glycogen) and

detoxification of drugs (barbiturates) and poisons

Function of rough ER – secretion of proteins, glycoproteins

formation of transport vesicules to other components of

endomembrane system

Golgi apparatus – sorting cell products, they are modified

and stored (removes sugar monomers and product diverse

oligosaccharides)

two poles are reffered to as the cis face ad trans face

Exocytosis and Endocytosis is transport of large molecules

Cell secretes macromolecules by a fusion of vesicles

with plasma membrane = Exocytosis - budded from

the Golgi – products

Endocytosis – cell takes in macromolecules a particulate

matter by forming new vesicles from plasma membrane

three types :

Phagocytosis – cell engulf a particle

Pinocytosis – cell gulf droplets of

extracellular fluid

Receptor-mediated endocytosis is very

specific – receptor and ligand

Lysosomes are digestive compartments

• membrane bounded sac of

hydrolytic enzymes

• enzymes hydrolyze in acidic

environment (pH 5) proteins,

polysaccharides, fats and nucleic

acids

• function is intracellular digestion of

food particles, smaller organisms and

organic components engulfing by

phagocytosis and own organic old

material by autophagy

Mitochondria and chloroplasts

Vacuoles, vesicles • membrane–bounded sacs • vacuoles have various functions: food vacuoles contractile vacuoles tonoplast

• Convert energy (ATP) that cells use for work

Mitochondria are the sites of cellular respiration

Chloroplasts are sites of photosynthesis

• Semiautonomic organelles, that grow and reproduce

within the cell

• contain own DNA (prokaryotic origin)

Mitochondria

• in all eukaryotic cells• hundreds or thousands• two membrane, each

is phospholipid bilayer

with a unique collection

of embedded proteins

The outer membrane is smooth, the inner membrane is

convoluted with infolding called cristae

Intermembrane space

Mitochondrial matrix

Chloroplast A member of plant organelles

family called plastids:

leukoplast

chromoplasts

chloroplasts

thylakoids

Inner membranous

system, outside of it

is stroma

• photosynthesis

The cytoskelet• the dynamic networks of

protein fibers extending

throughout the cytoplasm

• Support, motility,

regulation

• microfilaments (2)

• intermediate filaments (3)

• microtubules (1)

1

2

3

3. cell-shape, mechanical support, provides anchorage for

many organelles and cytosolic enzymes

2. the thinnest filaments, twisted double chain of actin subunits,

cell-shape, cell organization, pull a forces, function in

muscle, amoeboid movement – pseudopodia

1. compression-resisting function, dynamic behavior, binding

GTP for polymerization, intracellular transport (associated with

dyneins and kinesins, they transport organelles like

mitochondria or vesicles, the axoneme of cilia and flagella,

the mitotic spindle

Centrosomes and Centriolas

• 9 set of triplets microtubules • tubulin α, β => microtubules• grow out from a centrosome, within of

animal cells are a pair of centriolas• cell shape, cell motility, cell division,

organelle movements

Flagella and Cilia

• Unicellular eukaryotic organisms, sperm of animals, algae

and some plants• Cilia occur in large numbers on the cell surface.• Cilia work like oars:

• Flagella are longer and are usually limited to just one or few • the motor molecule

called dynein• basal body identical

to centriole• 9 doublets of outer

microtubules• one doublet of inner

microtubule

Flagellum

Microfilaments - Actin filaments

• Molecules of actin – a globular protein G => F fibrilar protein

• Is a twisted double chain of actin subunits

• function is bear tension (pulling forces)

• ameboid movement – extend and contraction of pseudopodia

• maintenance of shape, changes of shape

Muscle cells• protein myosin arranged

parallel to actin

• actin and myosin sliding

past one another

• results to contraction of

muscle, shortening the cell

Plant Cells:

have chloroplast use photosynthesis have cell wall one large vacuole are rectangular

Animal Cells:

don't have chloroplast no cell wall one or more small vacuole either circular or have irregular shape

Cellulose of plant cell walls helps to plant cells to allow high pressure to build inside of it, without bursting. A plant cell has to be able to accept large amounts of liquid through osmosis, without being destroyed. An animal cell does not have this cell wall. If you start to fill the animal cell with too much distilled water or other fluid, it will eventually pop.

Campbell, Neil A., Reece, Jane B., Cain Michael L., Jackson, Robert B., Minorsky, Peter V., Biology, Benjamin-Cummings Publishing Company, 1996 –2010.