Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

UNIT 1
...
coli)



Prokaryotic Features:

• Cytoplasm

◦ internal fluid component of the cell

• nucleoid

◦ region of cytoplasms where DNA is located (circular)

• plasmids

◦ autonomous circular DNA molecules that may be transferred between bacteria

• ribosomes

◦ complexes of RNA and protein that are responsible for polypeptide synthesis (70S)

• cell membrane

◦ semi-permeable and selective barrier surrounding the cells

• cell wall

◦ rigid outer covering made of peptidoglycan; maintains shape and prevents bursting (lysis)

• slime capsule

◦ thick polysaccharide layer used for protection against desiccation and phagocytosis

• flagella

◦ long, slender projections containing a motor protein that enables movement

• pili

◦ hair-like extensions that enable adherence to surfaces

• binary fission form of asexual production used by prokaryotic cells

• in the process:

◦ circular DNA is copied

◦ two DNA looks attach to membrane

◦ membrane elongates and pinches off (cytokinesis), forming 2 cells



Eukaryotic Cells
• organisms with cells that have a nucleus

• more complex and believed to have evolved from prokaryotes

• divided into 4 kingdoms:

◦ protista: unicellular/multicelluar organisms without specialized tissue

◦ fungi: cell wall made of cellulose and obtain nutrition via heterotrophic absorption

◦ plantar: cell wall made of cellulose and obtain nutrition autographically via photosynthesis

◦ animalia: no cell wall and obtain nutrition via heterotrophic ingestion



Organelles:

• specialized substructures within a cell that serve a specific function

• prokaryotic cells do not typically possess any membrane-bound organelles, whereas
eukaryotic cells possesses them



In Both Types of Cells:

• Ribosomes

◦ structure: two subunits made of RNA and protein; larger in eukaryotes (80S) than
prokaryotes (70S)


◦ function: site of polypeptide synthesis (translation)

• Cytoskeleton

◦ structure: a filamentous scaffolding with the cytoplasm

◦ function: provides internal structure and mediates intracellular transport (less developed in
prokaryotes)

• Plasma Membrane

◦ structure: phospholipid bilayer embedded with proteins

◦ function: semi-permeable and selective barrier surrounding the cell



Eukaryotic Organelles:

• Nucleus

◦ structure: double membrane with pores, contains an inner region called a nucleolus

◦ function: stores genetic material DNA as chromatin; nucleus site of ribosome assembly

• Endoplasmic Reticulum

◦ structure: membrane network that may be bare (smooth ER) or studded with ribosomes
(rough ER)

◦ function: transports materials between organelles (smooth ER = lipids, rough ER =
proteins)

• Golgi Apparatus

◦ structure: an assembly of vesicles and folded membranes located near the cell membrane

◦ function: involved in the sorting, storing, modification and export of secretory products

• Mitochondrion

◦ structure: double membrane structure, inner membrane highly folded into internal cristae

◦ function: site of aerobic respiration (ATP production)



Plant Cells Only:

• Chloroplast

◦ structure: double membrane structure with internal stacks of membrane discs (thylakoids)

◦ functions: site of photosynthesis → manufactured organic molecules are stored in various
plastids

• Vacuole (large and central)

◦ structure: fluid-filled internal cavity surrounded by a membrane

◦ function: maintains hydrostatic pressure (animal cells may have small, temporary
vacuoles)

• Cell Wall

◦ structure: external outer covering made of cellulose (not an organelle per se, but a vital
structure)

◦ function: provides

◦ support and mechanical strength; prevents excess water uptake



Animal Cells Only:

• lysosome

◦ structure: membranous sacs filled with hydrolytic enzymes

◦ function: breakdown/hydrolysis of macromolecules (presence in plant cells is subject to
debate)



Electron Microscopy
• electron microscopes use electron beams focused by electromagnets to magnify and resolve
microscopic specimens

◦ transmission electron microscopes (TEM) generate resolution cross-sections of objects


◦ scanning electron microscopes (SEM) display enhanced depth to map the surface of
objects in 3D

• electron microscopes have 2 key advantages when compared to light microscopes:

◦ they have a much higher range of magnification (can detect smaller structures)

◦ they have much higher resolution (can provide clearer and more detailed images)

• some disadvantages of electron microscopes are that they cannot display living specimens in
natural colors
Cell Micrographs
• micrograph is a photo or digital image being taken through a microscope to show a magnified
image of specimens

• while organelles have identifying structure, specific shapes may vary depending on the location
of cross-section

• attempts can be made to deduce function based on the relative abundance of various
organelles:

◦ mitochondria: cells with many mitochondria typically undertake energy-consuming
process (e
...
neurons, muscle cells)

◦ ER: cells with extensive ER network undertake secretory activities (e
...
plasma cells,
exocrine gland cells)

◦ lysosomes: cells rich with lysosomes tend to undertake digestive processes (e
...

phagocytes)

◦ chloroplasts: cells with chloroplasts undergo photosynthesis (e
...
plant leaf tissue but not
root tissue)



Prokaryote Structure

• pili: shown as single lines

• flagella: shown as thicker and significantly longer lines than the pili

• ribosomes: labeled as 70S

• cell wall: labelled as being composed of peptidoglycan; thicket than cell membrane

• shape: appropriate for bacteria chosen (e
...
E
...
g

---