Topic 1: Cells 1.2 Ultrastructure of Cells

Prokaryotic Cells Simple cell structure without compartmentalization Divide by binary fission

Cell Wall: rigid outer layer made of peptidoglycan that maintains shape and protects the cell from damage or bursting if int. pressure is high

Cell/Plasma Membrane: semi-permeable barrier that controls entry and exit of substances

Cytoplasm: Fluid component that contains the enzymes needed for metabolic reactions

Nucleoid: region of the cytoplasm that contains genophore (prokaryotic DNA)

Plasmid: additional DNA molecule that exists and replicates independently of genophore (can be transmitted between bacterial species)

Ribosome: complex RNA and protein that are responsible for polypeptide synthesis

Slime Capsule: thick polysaccharide layer for protection against desiccation and phagocytosis

Flagella (single flagellum): long, slender projection containing a motor protein which spins the flagella like a propeller, enabling movement

Pilli (attachment): hair like extensions which a shorter in length to allow bacteria to adhere to one another or to available surfaces.

Pilli (sex): hair like extensions which are longer in length, they allow for the exchange of genetic material (plasmids) via bacterial conjugation.

Binary Fission: Axesual reproduction Not mitosis (no genetic material

condensation & spindle formation)

The process:o Circular DNA is copied in

response to a replication signal

o Two DNA loops attach to membrane

o Membrane elongates and inches off (cytokinesis) , forming two separate cells

Topic 1: Cells 1.2 Ultrastructure of Cells

Eukaryotic Cells Compartmentalized cell structure

Cell Membrane: semi-permeable barrier that controls entry and exit of substances

Cytosol: fluid portion of the cytoplasm (not including organelles or other insoluble materials)

Nucleus: contains hereditary material (DNA) and thus controls cell activities and mitosis

Nucleolus: site of the reduction and assembly of ribosome components

Ribosome: complexes of RNA and protein that are responsible for polypeptide synthesis

Mitochondria: site of aerobic respiration, which produces large quantities of chemical energy (ATP) from organic compounds.

Golgi Apparatus: An assembly of vesicles and folded membranes involved in the sorting, storing and modifying of secretory products.

Lysosome: Site of hydrolysis/digestion/breakdown of macromolecules

Peroxisome: catalyses breakdown of toxic substances like hydrogen peroxide and other metabolites

Centrioles: Microtubule-organising centres involved in cell division (mitosis/meiosis and cytokinesis)

Endoplasmic Reticulum: system of membranes involved in the transport of materials between organelles

Rough ER: stu dded with ribosomes and involved in the synthesis and transport of proteins destined for secretion

Smooth ER: involved in the synthesis and transport of lipids and steroids, as well as metabolism of carbohydrates

Topic 1: Cells 1.2 Ultrastructure of Cells

Prokaryotes EukaryotesDNA Naked DNA (no histones) DNA associated with

histonesDNA Circular LinearDNA Genes do not contain

intronsGenes may contains introns

DNA Found in Cytoplasm Found in NucleusInternal Structures No membrane bound

organellesMembrane bound organelles

Ribosomes 70s ribosomes 80s ribosomesReproduction Asexual (binary fission) Asexual (mitosis) or Sexual

(meiosis)Reproduction Haploid DNA Diploid or more DNA