Eukaryotic cells Structure of Eukaryotic cells Nucleus contains

Eukaryotic cells

Structure of Eukaryotic cells • • Nucleus - contains DNA Membrane bound organelles – p 64 Larger than prokaryotic cells Divided into 5 categories: – Nucleus and ribosomes – Organelles of the endomembrane system – Peroxisomes and vacuoles – Energy related organelles – cytoskeleton

Nucleus • • Nucleus contain chromatin material Nucleoplasm – semifluid matrix RNA produced in nucleus Nucleolus – dark region of chromatin, r. RNA produced and forms ribosomes • Nuclear envelope – double membrane with nuclear pores (allow m. RNA and ribosomes out)

Ribosomes • • Non-membrane bound, protein synthesis Composed of 2 subunits Polyribosomes – group of ribosomes Cytoplamsic ribosomes and ER ribosomes produce their own proteins

Endomembrane System • • • Nuclear envelope membranes of ER golgi apparatus vesicles Compartmentalizes the cell Page 72

Endoplasmic reticulum • Physical continuous with the nuclear envelope • Rough – studded with ribosomes – synthesizes proteins – Forms vesicles that transport large molecules usually to cell membrane or Golgi apparatus Smooth – continuous with rough, contain gland cells that synthesize lipids

Golgi Apparatus • Stack of curved, flattened sacs, face ER and cell memebrane • Receives vesicles from ER • Sorts and packages proteins and lipids, some are lysosomes, others exit through exocytosis.

Lysosomes • • Membrane vesicles produced by GA contain hydrolytic digestive enzymes Recycle cellular material. Tay-Sachs disease result of missing enzyme that digests a fatty substance that helps insultate nerve cells. • Apoptosis – programmed cell death

Peroxisomes • Vesicles that enclose enzymes whose action results in hydrogen peroxide • Hydrogen peroxide is broken down to water and oxygen by catalase.

Vacuoles • Membranous sacs larger than vesicles • Usually store substances • Central vacuole – filled with cell sap that give support to cell and stores nutrients and waste products, plants do not have an excretory system. – Functions as lysosomes in plants, old organelles fuse with vacuole and get broken down.

Chloroplasts • Use solar energy to synthesize carbohydrates • A type of plastid (double membrane organelle that contains a series of internal membranes/vesicles and DNA) ex. Chromoplasts, leucoplasts. • Stroma (space), Thylakoid (disk), granum (stack of disks)

Mitochondria • Double membrane, outer and inner (cristae) • Cristae are folded to increase surface area • Matrix contains mt. DNA and ribosomes • Produce ATP

Cytoskeleton • Maintains shape of cell and allows organelles to move. • Contains actin filaments, intermediate filaments and microtubules.

Actin filaments • Long, thin flexible fibers • Structural role, just under cell membrane • Together with myosin, move the cell and its organelles.

Intermediate filaments • Ropelike assembly of fibrous polypeptides. • Roles include supporting nuclear envelope, plasma membrane and/or cell to cell junctions.

Microtubules • Small, hollow cylinders • Made of tubulin, small globular protein • During cell division, disassemble and reassemble as spindle fibers, and back again.

Centrioles • 9 + 0 microtubule triplets • In animal cells, contained in the centrosome - main microtubule organizing center for the cell • Involved in the process of microtubule assembly and disassembly? • In cell division, aid in mitotic spindle organization? • Give rise to basal bodies in cells with cilia and flagella?

Cilia and Flagella • Hair-like projections used for locomotion • Membrane bound, 9+2 pattern • Basal body in cytoplasm at base