BIOLOGY 11 IB 2.3: EUKARYOTIC CELLS

ASSESSMENT STATEMENTS 2.3.1Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell 2.3.2Annotate the diagram with the functions of each named structure 2.3.3Identify structures from in electron micrographs of liver cell 2.3.4Compare prokaryotic and eukaryotic cells 2.3.5State three differences between plant and animal cells 2.3.6Outline two roles of extracellular components

EUKARYOTIC CELLS Eu = True, karyon meaning ‘kernel’, referring to the nucleus  True Nucleus The general size of a eukaryotic cell is about um. The ribosomes are larger than eukaryotic cells (80S versus 70S ribosomes) Compartmentalization allows chemical reactions to be separated increasing the efficiency of the cell

ORGANELLES Endoplasmic Reticulum Ribosomes Lysosomes (not usually in plant cells) Golgi Apparatus Mitochondria Nucleus Chloroplasts (only in plant cells) Vacuoles

ENDOPLASMIC RETICULUM Extensive netowrk of tubules or channels that extends almost eveywhere in the cell from the nucleus to the plasma membrane Function: transportation of materials throughout the internal region of the cell Smooth ERRough ER Produces membrane phospholipids and cellular lipids Produces sex hormones (testosterone and estrogen) Detoxifies drugs in the liver Stores calcium ions needed for contraction in muscle cells Transport lipid based compounds Aid the liver in releasing glucose into the bloodstream when needed Involved in protein development and transport (function as support for ribosomes)

RIBOSOMES Carry out protein synthesis Can be free in the cytoplasm or attached to the rough ER Composed of RNA and protein Larger and denser in eukaryotes vs prokaryotes Composed of two subunits (80S)

LYSOSOMES Digestive centers the arise from the Golgi apparatus Sacs of hydrolytic enzymes the catalyze the breakdown of proteins, nucleic acids, lipids and carbohydrates Fuse with old or damaged organelles to recycle the components Responsible for breaking down materials brought into the cell by phagocytosis The interior of a functioning lysosome is acidic

GOLGI APPARATUS Composed of flattened sacs called cisternae Functions in the collection, packaging, modification, and distribution of materials synthesized in the cell One side is always close to the rough ER (cis side) receiving products from the ER Movement occurs to discharge the product from the opposite (trans) side. Small sacs, called vesicles, can be seen coming off the trans side carrying modified materials to wherever they are needed inside or outside the cell. Prevalent in glandular cells that manufacture and secrete substances (ex. in the pancreas)

MITOCHONDRIA Have their own DNA! (a circular chromosome similar to that in bacterial cells) Double membrane – smooth on the outside, folded on the inside Reactions within produce usuable cellular energy (ATP), where it gets its nickname ‘the powerhouse’ Produces and contains its own ribosomes (70S) Cells that have high energy requirements, such as muscle cells, have large numbers of mitochondria

NUCLEUS Isolated region housing the DNA in the form of chromosomes (strands of DNA wrapped around histones [protein]) Double membrane  nuclear envelope (allows for compartmentalization – providing an area where DNA can carry out its functions and not be affected by processes occurring in other parts of the cell) Nuclear pores in the nuclear membrane allow communication with the cell’s cytoplasm

CHLOROPLASTS ONLY in algae and plant cells! Double membrane, about the same size as mitochondrion Has its own DNA (in the form of a ring) and 70S ribosomes Grana (pile of thylakoids) + stroma (fluid containing enzymes necessary for photosynthesis) Can reproduce independently of cell

VACUOLE Storage organelles the usually form from the Golgi apparatus Occupy large space in plant cells Can store food, metabolic wastes and toxins, and water Enable cells to have higher surface area to volume ratios In plants, they allow an uptake of water providing rigidity

CENTROSOME Generally contains a pair of centrioles which are involved in assembling microtubules (important in providing cell structure and allowing movement) Important to cell division Higher plant cells produce microtubules even though they do not have centrioles Located at one end of the cell, close to the nucleus

Prokaryotic CellsEukaryotic Cells DNA in ring form without histonesDNA with protein as chromosomes/chromatin DNA free in cytoplasm (nucleoid region)DNA enclosed in a nuclear envelope No mitochondriaMitochondria present 70S ribosomes80S ribosomes No internal compartmentalization to form organelles Internal compartmentalization present to form many types of organelle Size = less than 10 micrometersSize = more than 10 micrometers

SIMILARITIES OF PROKARYOTIC AND EUKARYOTIC CELLS 1.Both types of cell have some sort of outside boundary that always involves a plasma membrane 2.Both types carry out all the functions of life 3.DNA is present in both cell types

Plant CellsAnimal Cells Exterior of cell includes an outer cell wall with a cell membrane just inside Exterior of cell includes only a cell membrane Chloroplasts present in the cytoplasmNo chloroplasts Possess large centrally located vacuolesVacuoles are usually small or non existent Store carbohydrates as starchStore carbohydrates as glycogen Do not contain centrioles within a centrosome area Contain centrioles within a centrosome area Fixed, often angular shape (because of rigid cell wall) Cell is flexible and usually round EUKARYOTIC CELLS