Prokaryotic Cells Chapter 4

Prokaryotes The first types of cells to develop evolutionarily were prokaryotes The term prokaryote means “naked DNA” Prokaryotes therefore, do not have a nuclear membrane surrounding their DNA

Prokaryotes In fact, they have no membrane bound structures and are instead very simple in construction Prokaryotes began, and continue to be, unicellular organisms All bacteria are prokaryotes

Prokaryotes consist of the following structures: Plasma Membrane – controls what enters and exits the cell Sometimes has infoldings (called mesosomes) that increase the surface area of the membrane

Cell Wall – provides protection Made of a protein/carbohydrate structure Bacteria are identified based upon which of the two types of cell walls they have as based upon the Gram Stain Technique Gram positive bacteria stain purple Gram negative bacteria stain pink

Flagella – Tail-like structure that helps with locomotion Pilli – Threadlike projections that help with attachment and sexual reproduction (through transfer of DNA) Cytoplasm – clear, gelatinous fluid that takes up most of the space inside the cell and contains all necessary enzymes for metabolic processes

Ribosomes – Used for protein synthesis, which is a part of gene expression Composed of two parts called the “heavy” and “light” pieces Heavy and light pieces are 50s and 30s in size (s represents the svedburg unit) Total measurement of prokaryotic ribosomes is 70s (doesn’t add up because s is not a measurement of size but sedimentation during centrifugation)

Nucleoid – Region where DNA can be found In prokaryotes, DNA forms a closed loop Many prokaryotes also have a smaller loop called a plasmid that contains a few genes and can be easily transferred to other cells

Prokaryotes

Conjugation Form of reproduction in some prokaryotes 2 prokaryotes attach to each other via the pilus and exchange genetic material. Then go on to binary fission. NOTE: Conjugation does not create new prokaryotes!! It recombines the DNA before they go on to divide separately.

E. Coli infection http://www.biology.ualberta.ca/facilities/multimedia/uploads/microbiology/ecoli.html

Prokaryotes Binary fission Method of reproduction in prokaryotes Asexual form of reproduction in which a cell divides into two same size cells that are genetically identical

Eukaryotic Cells Chapter 4

Eukaryotic Cells evolved after prokaryotes The endosymbiotic theory states that eukaryotes came about when one prokaryote enveloped another

Eukaryotic Cells are much more complex than prokaryotes Made up of smaller components with specialized functions called organelles

Eukaryotes Cell Organelles Nucleus – contains DNA Ribosomes – create new proteins Composed of a 40s and 60s unit which makes the ribosome overall to be 80s Rough Endoplasmic Reticulum (Rough ER) – site protein synthesis Called “rough” because it is studded with ribosomes

Smooth ER – site of lipid (fat) synthesis and storage Lysosome – contains enzymes that break down cellular waste Golgi Apparatus (aka Golgi Body) – packages and ships proteins (to other parts of the cell as well as outside of the cell)

Mitochondria – “powerhouse of the cells”; creates energy for the cell in the form of ATP Cytoplasm – clear gelatinous fluid inside of the cell Centriole – helps with cell division in animal cells

Chloroplast – found only in plant cells, this organelle is the site of photosynthesis Cell Wall – found only in plant cells, this organelle gives support and structure to the cell Plasma membrane – controls what enters and exits the cell

Microtubules and Microfilaments – linear protein structures that provide support for animal cells; sometimes aid in movement of cell organelles Nucleolus – found within the nucleus, this organelle is in charge of creating new ribosomes Vacuole – stores food, water, and/or waste; animal cells have multiple small ones while plant cells have one large vacuole for water storage only

Plant and animal cells are very similar but have a few distinct differences: Plant Cells Animal Cells Cell Wall One large vacuole No centrioles Has chloroplasts Store energy as starch No cell wall Many small vacuoles Has centrioles No chloroplasts Store energy as glycogen

Animal Cell Mix-Match Plant Cell Mix-Match http://www.biology.ualberta.ca/facilities/multimedia/uploads/cell_biology/animalcell_DD.html Plant Cell Mix-Match http://www.biology.ualberta.ca/facilities/multimedia/uploads/cell_biology/plantcell_DD.html

2.3.5

Roles of extracellular components: Plant cell wall mantains cell shape, prevents excessive water uptake, and holds the whole plant up against the force of gravity Animal cells secrete glycoproteins that integrate themselves in the plasma membrane The glycoproteins help with support, adhesion and movement

Prokaryotes Eukaryotes No membrane bound organelles; DNA is in the cytoplasm (nucleoid region) DNA is “naked”; has no associated proteins No centrioles No mitochondria 70s ribosome All ribosomes are “free” Cell wall is made of peptidoglycans Multiple membrane bound organelles including the nucleus, which houses DNA DNA is associated with proteins that help it to fold into chromosomes Centrioles Mitochondria 80s ribosome Free ribosomes and ribosomes attached to the rough er No cell wall or one made of cellulose

Comparing Prokaryotes and Eukaryotes http://www.biology.ualberta.ca/facilities/multimedia/uploads/cell_biology/provseuk.html