Structure, function and growth of prokaryote and eukaryote cells

‘Before the true nucleus’ True nucleus Semi-fluid part of the cytoplasm that contains structures to support the cells organelles Structure, function and growth of prokaryote and eukaryote cells (a) Comparison of features and ultrastructure of prokaryotic and eukaryotic cells. • Comparison of DNA, presence or absence of nucleus and functions of organelles present, membranes and cytosol organisation

Discussion Questions • What cells are prokaryote / eukaryote? • What structures do all cells have in common? • What cell structures do you already know?

Eukaryote Cell - plant

Eukaryote Cell - animal

Features of an eukaryote cell….. • Cell Wall (plants only) • Made of Cellulose • Plasmodesmata • Connecting structures between cells that allow a continuous cytoplasmic link. • Middle Lamella • Thin layer of material that binds the cell walls of two adjacent cells together

…features of an eukaryote cell… • Vacuole (plants = large; animals = small or absent) • Membrane around the vacuole controls the movement of substances into and out of the vacuole. • Storage reservoir for nutrients, waste products, enzymes and other metabolites. • Maintains cell turgor

…features of an eukaryote cell… • Cytosol – fluid part of the cytoplasm which contains components of the cytoskeleton and in which the cells organelles are suspended. • Cytoskeleton • Framework of protein fibres that • provides support for the cell membrane • Supports the organelles • Helps the cell move • Provides a surface for chemical reactions • Nucleus • Nucleosomes • Structures made up of histone proteins, that DNA coils around allowing it to become tightly packed • Nuclear Membrane • Double membrane structure with pores • Membrane connects to the endoplasmic reticulum

…features of an eukaryote cell…

…features of an eukaryote cell… • Endoplasmic reticulum • Smooth ER • Site of biochemical reactions, in particular phospholipid and fatty acid synthesis • Rough ER • Has ribosomes attached • Site of protein synthesis • Golgi Apparatus (a.k.a. dictyosome in plants) • Modifies and packages materials such as proteins and polysaccharides. • Stores and transports secretory products such as enzymes and hormones.

…features of an eukaryote cell • Mitochondria • Has a double membrane.. • Contains its own DNA and ribosomes. • Matrix is the site of the Krebs Cycle. • Cristae (infolded inner membrane) is the site of the cytochrome system. • Chloroplasts (plants only) • Grana • Site of the light stage of photosynthesis • Stroma • Site of the Calvin cycle (carbon fixation)

…features of an eukaryote cell • Microvilli (animal only) • Finger-like projections covered by the cell membrane. • Increase the absorptive or secretory surface area of the cell. • Centrioles (animal only) • Assist in the organisation of the spindle fibres during cell division

…features of an eukaryote cell… • Lysosomes • Membrane bound sac containing enzymes that digest foreign invaders and unwanted organelles • Microbodies (aka peroxisomes) • Membrane bound vesicle containing enzymes that need to be kept separate from the rest of the cytosol

…features of an eukaryote cell • Endomembrane • All the internal membranes of the cell • Ensures the cytosol is organised so that the cell function can be controlled and regulated

Prokaryote Cell

Features of a prokaryote cell… • Cell Wall • Made of peptidoglycan (combination of polysaccharide and peptide chains) • A staining procedure called a gram stain can be carried out. Gram positive bacteria have a thicker cell wall that takes up the stain. Gram negative bacteria don’t take up the stain

Gram negative bacteria • Thin layer of peptidoglycan • Outer membrane • Gram positive bacteria • Thick layer of peptidoglycan

… features of a prokaryote cell… Flagella (singular = Flagellum) Used for movement Pili (a.k.a fimbriae) Shorter, straighter and thinner than flagella Used for attachment Glycocalyx (Capsule or Slime layer) Mucus like layer made of polysaccharide and/or polypeptide Protects bacteria from enzymes, antibodies and phagocytes

…features of a prokaryote cell… • Cytosol • NO NUCLEAR MEMBRANE • Does have a nuclear region where the DNA tends to congregate • DNA • Single circular molecule • DNA highly condensed by coiling and folding to produce a structure known as a nucleoid.

…features of a prokaryote cell • Plasmid • Small circular rings of ‘accessory’ DNA • Replicate independently of the main chromosome • Transferred from cell to cell • Ribosomes • Site of protein transcription

Learning Activities • Draw diagrams of prokaryote and eukaryote cells, with functions of organelles written in • Create a table that highlights differences and similarities between prokaryotes and eukaryotes • Add information to the organelles and cell structures sheet to include prokaryote structures

Learning Activities • Complete the following worksheets • Bacteria Cells • Identifying TEM Photographs • Identifying Cell Structures • Read DART material (pg 1-8) and take further notes

Learning Activities • Look at the following websites (access from biozone links (cell biology) • www.cellsalive.com/cells/cell_model.htm • www.wisc-online.com/objects/index_tj.asp?objid=AP11604 • Try the multichoice questions from past AH papers

Structure, function and growth of prokaryote and eukaryote cells