Test 2 Ch 5 SG

Cellular Structures of Microbes

Feature	Prokaryotic	Eukaryotic
Nucleus	Absent	Present
Internal Structures	Few or none	Many (membrane-bound organelles)
Size	Small (~1.0 μm)	Larger (10–100 μm)
Complexity	Simple	Complex
Examples	Bacteria, Archaea	Algae, Protozoa, Fungi, Plants

• Microbes can be both Eukaryotic and Prokaryotic!!!

Eukaryotes

• Some Eukaryotes such as Fungi, algae, plants, and some protozoa have a Cell Wall

  • It is made of various polysaccharides

    • Plant cell walls- composed of cellulose

    • Fungal cell walls- composed of cellulose, chitin, and/or glucomannan

    • Algae cell walls- composed of a variety of polysaccharides

  • All Eukaryotic cells have Cytoplasmic Membranes

    • They are a fluid mosaic of phospholipids and proteins

    • Contain steroid lipids like cholesterol to help maintain fluidity

    • Control movement of molecules and material into and out of cell

• Eukaryotic cells have organelles with separate membrane inside the cell: Membranous organelles

• Eukaryotic cells contain a variety of organelles that are surrounded by phospholipid bilayer membranes like the cytoplasmic

  • Membranes including the nucleus, endoplasmic reticulum, golgi body and mitochondria

    • Prokaryotic cells lack these structures

Endocytosis

• The process by which Eukaryotic cells absorb particles by engulfing them

• Eukaryotic cell membranes helps in endocytosis

• Phagocytosis- when a solid is brought into the cell

• Pinocytosis- when a liquid is brought into the cell

The Cytoskeleton

• An extensive network of protein fibers and tubules

• Produces the basic shape of the cell

• Anchors organelles

• Made up of tubulin, actin and intermediate filaments

Ribosomes

• The sites for protein synthesis

• Eukaryotic ribosomes are larger than Prokaryotic ribosomes

• Eukaryotes have 80s ribosomes, composed of 60s and 40s ribosomes

• Prokaryotes have 70s ribosomes

  • The Svedberg or (S) unit is an indirect measure of a particle's size

  • Ribosomes are little protein producing robots

Nucleus

• Usually spherical to ooid and is often the largest organelle in a cell

• Some eukaryotic cells have a single nucleus, others have more

• It's often called "The control center of the cell"

  • Because it contains most of the cell's genetic instructions in the form of DNA

• Nucleoplasm- the semiliquid matrix of the nucleus

• The nucleolus (in the nucleoplasm) is where RNA is made and ribosomes are assembled

• Nuclear envelope- a double membrane that surrounds the nucleus. Which is made of 2 phospholipid bilayers

  • Contains nuclear pores- protein lined channels that pierce the 2 membranes.

    • Nuclear pores control the import and export of sibstances through the envelope

Endoplasmic Reticulum

• The factory in the cell

• Endoplasmic reticulum (ER)- network of tubes that is connected to the outer membrane of the nucleus. It is where the cell makes proteins and lipids

• 2 forms of ER

  • Smooth endoplasmic reticulum (SER) and Rough endoplasmic reticulum (RER)

  • SER plays a role in lipid synthesis as well as transport

  • Rough ER is rough because ribosomes attach to its outer surface where they produce proteins

Golgi Body

• The post-office of the cell

  • "shipping department" of a cell

    • it receives, processes, and packages large molecules for export from the cell

• Secretory- packages secretions in sacs

  • Fuse with the cytoplasmic membrane before dumping their contents outside the cell through exocytosis

• Composed of series of flattened hollow sacs that composed a phospholipid bilayer

Mitochondria

• Called the Powerhouse of the cell

  • Because their cristae produce most of the ATP in many eukaryotic cells

• 2 membranes

  • Cristae- the inner bilayer that forms numerous folds that increase the innder membrane's surface area

• It has their own DNA and carry 70s ribosomes

• It's divided independently of the cell but remain dependent on the cell for most of their proteins

Metabolism

• The collection of controlled biochemical reactions that takes place within a microbe

Metabolic processes

8 elementary statements

1. Cells get nutrients for building and energy

2. Metabolism needs energy from light or breaking down nutrients

3. Energy is stored in ATP

4. Cells break down nutrients into smaller building blocks

5. Cells use building blocks and energy to build larger structures

6. Enzymes and energy link building blocks to form macromolecules

7. Cells grow by assembling macromolecules

8. Cells divide when they double in size